Geology of petroleum

Emmons, William H. (William Harvey) · 1921 · Historical

Geology of petroleum by Emmons, William H. (William Harvey) (1921). Full text and reference in the Mountain Man Mining Library.

Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.

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J

Geology Of

Petroleum

N.

By

WILLIAM HARVEY EMMONS, Ph.D.

Professor And Head Of Dbpartmet Of Oeoloot Axd Mineralogy, University

Of Minnesota; Director, Minnesota Oeoloqical Survey; Formerly

Qeologist, Sf.Ction Of Metalliferous Deposits, United

States Oeologzcal Survey.

First Edition

'

McGRAW-HILL BOOK COMPANY, Inc,

New York: 370 Seventh Avenue

London: 6 & 8 Bouverie St., E. C. 4

1 I

Copyright, 1921, by the McGraw-Hill Book Company, Inc.

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Thb Map1.K Phkss Vork Ia

Preface

I have attempted in this volume to present as briefly as is practicable a perspective of the data of the geology of petroleum. The work is based on a series of lectures which for several years past I have offered in courses on economic geology at the Dniversity of Minnesota. These lectures have been rewritten and expanded. The material was first prepared some years ago to be included as a chapter in *'The Principles of Economic Geology/' recently issued. The chapter was so large, however, that to have included it would have defeated some of the purposes of that volume. It was withdrawn and rewritten and is offered here.

This book was prepared to be used as a text for students who wish to acquire some knowledge of the geology of petroleum, especially for those who have already studied the operation of geologic processes and the principles of stratigraphy. I have introduced sections showing the strata of many oil fields and many details of stratigraphy which it will be desirable to omit in classroom work. The best results will probably be obtained by omitting much of the material presented for certain fields and emphasizing that relating to other fields, especially those of which the students already have some general knowledge.

Within the last few years I have had many opportunities to visit the geologic departments of petroleum engineers and corporations and have been impressed with the large amount of carefully prepared data which they possess. I can not hope to add much, if anything, to these data. Nevertheless, by offering a Uttle about many fields I trust I have rendered a service to the profession. This volume is not intended to serve as a handbook of petroleum geology. I have included in it, however, brief sketches of the geology of many oil fields and numerous references to the literature treating them, and I hope it will serve some of the needs of a geologist who is undertaking the study of a field new to him.

I reaUze that there may be serious omissions and possibly errors in the presentation and discussion of so much material gathered

vi PREFACE

from so many sources. I shall esteem it a favor if anyone whose statements I may have misquoted or misinterpreted will set me right, and if those who have had .superior opportunities for study of certain districts will correct any wrong impressions I may have given.

In general I have followed the standard uses of terms. With respect to the use of the term monocline, however, I have departed from the once standard usage and have classed as monoclinal structural features those strata on the flanks of other folds that outcrop and are sealed above the reservoirs. In this usage I have followed many of the highest authorities in the field of petroleum geology. Such a use, I believe, is justified. It is convenient and in many cases it greatly simplifies expression and it is understood by all geologists working in the field of petroleum geology.

I acknowledge my indebtedness to Professors C. R. Stauffer and F. F. Grout and to Messrs. G. M. Schwartz and John Gruner, of the Department of Geology and Mineralogy of the University of Minnesota, and to Mr. Julius Segall and Mr. Frank Notestein, who have read critically sections of the volume; to Prof. J. A. Bownocker who has read the sections on Ohio fields and to Mr. N. O. Barrett who has read the section on Illinois fields; and to Messrs. O. F. Ernster and Karl A. Berg for many services, especially in connection with the preparation of drawings. I have endeavored suitably to acknowledge sources of information by footnote references.

W. H. Emmons.

Univeesity of Minnesota, Minneapolis, December J 1920.

Contents

Chapter I

Page

Preface v

Introduction 1

Greneral Occurrence of Petroleum 1

Uses 3

Historical Notes 3

Geographic Distribution of Petroleum 6

Geologic Distribution of Petroleum 10

Kinds of Strata Containing Petroleum and Gas 10

l' Geologic Ages of Strata Producing Petroleum and Gas 11

Chapter Ii

Surface Indications of Petroleum and Materials Associated

WITH It 16

Distribution 16

Classification of Hydrocarbons and Allied Substances 17

Oa Seeps 23

QU Ponds 25

Solid Bitumens 25

Bone Deposits in Asphalt 27

Bituminous Rocks 27

Test for QQ in Rocks 28

Bituminous Dikes 29

Gas Seeps 33

"Paraffin Dirt" 36

Mud Volcanoes 36

Mud Dikes 38

Oil Shales 38

. Burnt Shales 39

Salt Water Seeps 39

Sulphur and Sulphur Compounds 40

Chapter Iii

Openings in Rocks 41

Sizes of Openings. 41

Origin of Openings 42

Primary Openings 42

Intergranular Spaces in Sedimentary Rocks 42

Bedding Planes 44

Vesicular Spaces 44

Contents

Page

Openings in Pumice 44

Miarolitic Cavities 45

Submicroscopic Spaces 45

Secondary Openings 45

Openings Formed by Solutions 45

Openings Due to Shrinkage 45

Openings Due to the Force of Crystallization 46

Openings Due to Greater Stresses 47

Chapter Iv

Association of Petroleum and Salt Water 48

Chapter V

Reservoir Rocks and Covering Strata 53

Reservoir Rocks 53

General Character 53

Mineral Composition of Reservoir Rocks 58

Capacities of Reservoir Rocks 59

Coverings of Reservoirs 65

Kinds of Covering Strata 65

Thickness of Covering Strata 66

Chapter Vi

Some Properties of Petroleum and Gas 68

Color . . 68

Odor 68

Density 69

Viscosity 71

Composition of Petroleum 71

Composition of Natural Gases 74

Chapter Vii

Origin of Petroleum and Natural Gas 80

Inorganic Theories . . . . 80

Organic Theories 83

Association of Petroliferous Strata and Coal 88

Accumulation of Petroleum in Beds Formed Under Arid Conditions 90

Temperatures of Oil Fields 92

Chapter Viii

Maps and Logs 96

Structural Contour Maps 96

Well Logs 101

CONTENTS ix CHAPTERX

Paqb

Accumulation of Petroleum 105

The Anticlinal Theory 105

Segregation Due to Diflferences in Surface Tension 112

Fractionation of Petroleum in Clay 117

tp

Chapte

Structural Features of Oil and Gas Reservoirs 120

Reservoirs in Anticlines and Domes 120

Amplitudes of Anticlinal Folds that Form Reservoirs 131

Shapes of Anticlines that Form Reservoirs 133

Origin of Anticlines that Form Reservoirs 134

Arrangement of Anticlines that Form Reservoirs 137

Segregation of Oil on Basinward Sides of Folds 138

Reservoirs in Monoclines 139

Monoclines Sealed by Overlying and Underlying Clays or Shales

Joining Above Reservoirs 142

Monoclines Sealed by Faults 144

Monoclines Sealed by Local Cementation of the Reservoir Rock 146

Monoclines Sealed by Asphalt 146

Monoclines Sealed by Unconformities 149

Monoclines Sealed by Igneous Intrusions 152

Reservoirs in Flat-lying Beds 153

Aclines 153

Terraces 153

Reservoirs in-Synclines 154

Reservoirs Formed by Fissures 156

Accumulation in Sands of Irregular Pore Space 159

Accumulation at Unconformities 160

Successions of Petroliferous Strata 161

Distances Covered in the Migration of Petroleum 162

Minimum Inclination Necessary for Migration 163

Behavior of Folds in Depth 164

CHAPTER fX

Deformation OF Petroliferous Strata '.170

Deformation in Unconsolidated Materials 170

Influence of Faulting on Reservoirs 170

Chapter Xii

Metamorphism of Petroleum by Dynamic Agencies 173

Chapter Xiii

Gas Pressure and Oil Recovery 180

Gas Pressure 180

Behavior of Certain Wells That Yield Oil and Gas 183

X Contents

Chapter Xiv

Page

Petroliferous Provinces and Petrolkogenic Epochs 190

Chapter Xv

Appalachian, Lima-Indiana and Michigan Fields 195

Introduction 195

Appalachian Oil Fields 206

General Features 206

New York, Pennsylvania, and West Virginia 210

Eastern Ohio 225

References for New York, Pennsylvania, Ohio and West Virginia 231

Kentucky 233

Tennessee 244

Alabama 247

Lima-Indiana Field 248

Michigan Field 254

Chapter Xvi

Illinois 256

Introduction 256

Crawford, Lawrence and Adjoining Counties 261

Central and Western Illinois 264

References for Illinois Fields 269

Chapter Xvii

Mid-Continent Fields 271

General Features 271

Northeastern Oklahoma, Southeastern Kansas, Arkansas, and

Missouri 279

General Statement 279

Oklahoma 281

Salient Features 281

Cushmg Pool 287

Glenn Pool 292

Bristow Quadrangle 295

Nowata County Pools 295

Washington County Pools 296

Osage County Pools 297

Kay County Pools 298

Billings, Noble County 298

Garber, Garfield County 299

Muskogee County Pools 300

Okmulgee County Pools 304

References for Oklahoma . . . . 304

Arkansas 306

Kansas 307

Missouri 314

CONTENTS xi

Pages

Red River Region, Oklahoma and Texas 316

General Features 316

Healdton, Oklahoma ! ... 320

Loco, Oklahoma 321

Duncan, Oklahoma 322

Lawton, Oklahoma . 322

Cement, Oklahoma 323

Madill, Oklahoma 324

Wichita and Clay Counties, Texas 324

North-central Texas Fields 328

Fields East of Balcones Fault, Texas 337

General Features 337

Corsicana Field 339

Mexia-Groesbeck Field 342

Thrall Field 343

Northwestern Louisiana and Northeastern Texas 346

General Features 346

Caddo Field 351

De Soto-Red River Field 355

Pelican Field 365

References for Texas Fields 356

References for Louisiana Fields 356

Chapter Xviii

Prospects in Mississippi, Alabama and Georgia 358

Mississippi 358

Alabama 360

Georgia 362

CHAPTER XIX Gulf Coast Fields of Texas and Louisiana 36C

Chapter Xx

Rocky Mountain Fields 375

Wyoming 375

Greneral Features 375

Salt Creek 382

Powder River 385

Big Muddy Dome 386

Douglas 386

Lander 389

Maverick Springs 389

PUot Butte 390

Central Wyoming 390

Rock River 392

Lost Soldier 392

Xll CONTENTS

Page

Moorcroft 392

Newcastle 393

Upton-Thomton 394

Buck Creek 394

Mule Creek 394

Spring Valley 396

Labarge 396

Big Horn Basin 397

References for Wyoming 408

Montana 409

General Features 409

Stillwater Basin 411

Lake Basin 413

Porcupine Dome 415

Musselshell Valley 418

North-central Montana 420

Birch Creek-Sun River Area 421

Blackfeet Reservation 421

Bowdoin Dome 426

Eastern Montana , . . 426

North Dakota 428

Colorado 429

General Features 429

Florence 429

Boulder 431

Rangely 433

White River 434

Urado 434

Utah 435

Green River District 435

Hanksville 435

Salt Lake Basin 435

San Juan Field 438

Virgin City 439

New Mexico 439

Idaho and Oregon 441

Chapter Xxi

Pacific Coast Fields 442

California 442

General Features 442

Coalinga 444

Lost Hills 449

McKittrick, Sunset, and Midway 450

Kern River 457

Santa Clara 458

CONTENTS xiil

Paob

Summerland 460

Santa Maria 462

Los Angeles 463

Puente Hills 466

References for California 469

Alaska Fields 470

Chapter Xxii

Canada and Newfoundland 475

Ontario 476

Nova Scotia 483

New Brunswick 483

Quebec 484

Western Canada 485

References for Canada 494

Newfoundland 495

CHAPTER XXIII Mexico 497

Chapter Xxiv

Europe Except Russia . 507

Great Britain 507

France 509

Germany 513

Italy 514

Sicily 517

Galicia 517

General Features 517

Boryslaw 520

Opaka-Schodnica-Urycz 523

Western Galicia 524

Rumania 525

Chapter Xxv

Russia, Mesopotamia, Persia, and Egypt 533

Russia 533

General Features 533

Baku 535

Grozny . . . 541

Maikop . 542

Taman and Kertch 543

Sviatoi 543

Cheleken Island 544

Transcaspian Province 545

Tiflig 545

/

Xiv Contents

Page

Ferghana 546

Northern Russia 546

Mesopotamia 546

Persia 547

Egypt 649

Chapter Xxvi

Bubma And Oceanica 553

Burma 553

Yenangyaung 654

Yenangyat-Singu 655

Sumatra 557

Java 559

Borneo 560

Philippine Islands 561

Japan and Formosa 666

New Zealand 568

Australia 569

Chapter Xxvii

Caribbean Islands . . . . 571

Cuba ' 571

Haiti and Santo Domingo 573

Barbados 574

Trinidad 574

Chapter Xxviii

South America 580

Venezuela 580

Colombia 681

Peru 584

Ecuador 590

Argentina and Bolivia 591

Index 595

Geology

Of

Petroleum

Chapter I

Introduction General Occurrence Of Petroleum

Petroleum, or rock oil, is an inflammable mixture of oily hydrocarbons that exudes from the earth or is pumped up and is used extensively for generating heat, light, and power and for lubricating machinery.

Asphalt um is a solid bitumen, and maltha a semifluid bitumen; both are residues formed by the partial evaporation or inspissation of petroleum.

Natural gas, or rock gas, is an aeriform mixture that is found at or beneath the surface of the earth and is used as an illuminant, for fuel, and for generating power. Natural gas is commonly associated with petroleum.

Petroleum and natural gas are formed by the decomposition of, plant and animal remains that have been buried with sediments in the sea. They are almost never found in commercial quantities in igneous rocks, in metamorphosed rocks, or in fresh-water sediments not associated with marine strata. They generally originate in mudS; clays, or shales, or much less commonly in marls or limestones. Petroleum and natural gas can not ordinarily accumulate in shales in large amounts, because in such rocks adequate openings are generally not available. As a rule they accumulate in sands or sandstones associated with clays or shales, or in porous" limestones. In age the petroleum-bearing strata range from Ordovician to Recent.

Salt water is generally associated with petroleum and is believed to be sea water that filled the pores of the sands when they were laid down in the sea. Waters from oil-bearing strata differ from sea water in concentration and in composition, but there are

. of petroleum

MP9-*tcur;;pp0j$ixigl!iab 'changes have taken place since the original sea water was stored in the rocks. Not all oil-bearing strata are saturated with salt water; some contain very little water, V and in at least two fields the oil is floated on water that is practically free from salt.

Where rocks are saturated with petrolemn, natural gas, and salt water, the oil is generally found above the water, and as a rule the gas is found above the oil. This rearrangement is due chiefly to . gravity.

As a rule the strata that contain petroleum are folded. In some _places they are only gently folded; in others they are thrown into sharp folds, the beds dipping 20 to 30 degrees or more. In consolidated rocks, such as shales, sandstones, and limestones, which have been intensely deformed by faulting and close folding, oil is generally not found in large amounts. In unconsolidated series of rocks, such as clays, marls, and sands, large accumulations are known in areas of highly complicated structures. In some regions unconsolidated oil-bearing rocks have been intensely faulted by thrust faults and overturned, yet they stiU retain large accumulations of petroleum.

/ Many of the oil fields are on monoclines, on which are developed secondary folds, such as anticlines, synclines, domes, and structural terraces. In rocks that are highly saturated with oil and in beds that dip very gently the oil gathers in domes, if any are available, but accumulation takes place also in very gentle folds and in structural featiu-es that are not **closed" (see p. 96), such as plunging anticlines and terraces. In rocks that are less highly saturated with oil in a country containing sharp folds, the accumulation is generally in areas of closed structures, such as domes, or in traps such as are formed where an open fold is crossed by a fault.

Not all reservoir are porous beds on anticlines. Any body of porous rock seate|$above inany manner may under certain conditions supply a reservoir for the accumulation of either petroleum or natural gas.

If the porous strata in areas of folded structure are not saturated with water, oil will descend on the folds until it occupies the flanks of synclines, and if no water is present it tends to move down to the bottoms of the folds. In strata containing openings of unequal size, oil and gas accumulate in the larger openings, the water being drawn by capillary attraction into the smaller ones.

Introduction

Uses

in its crude state petroleum is used extensively for fuel. It has a high evaporating power per unit of weight and is in demand for use imder locomotive and marine boilers. The heavy oils are used for fuel more generally than the lighter oils, because as a rule the heavy oil will not yield such valuable products. Heavy oils are used also in the crude state for road dressing, and for making roofing.

In refining petroleum, it is broken up by a process of distillation into many products, including petroleum ether, gasoline, naphtha, kerosene, lubricating oils, vaseline, paraffin wax, and petroleum coke. Each of these materials has a variety of uses. Ether is used in medicine as a cooling agent and for priming internal-combustion engines in cold weather. Gasoline is used as fuel in internal-combustion engines, for cleaning cloth and other substances, and as a solvent of oil and grease. Naphtha is used for approximately the same purposes and much commercial gasoline is a mixture of gasoline and naphtha. Kerosene is used principally for illumination and as a fuel for tractors. Lubricating oils are the heavy viscous products obtained by refining petroleum. They are used for lubricating machinery and when highly refined for medicinal purposes, especially as laxatives. Paraffin wax is used for making candles, for sealing preserved fruits and vegetables, and as a preservative. It is used also for medicinal purposes, especially in the treatment of burns. Petroleum coke is used in metallurgic processes, as a fuel, and for making carbons for batteries and arc lights.

Many petroleum refineries do not produce all the products mentioned. Some "topping plants" distill off the lighter products, such as may be used as fuel for internal-combustion engines, and sell the heavier residues for fuel oil or for road dressing.

Asphalt is formed in nature by the drying up of petroleum, chiefly where it exudes at the surface. It is used for making pavements, roofings, and other building materials. Some oils on refining yield an artificial asphalt that is much like the natural product and is used for similar purposes.

Historical Notes

The bitumens were known to the ancients in the earliest historic era. The Bible refers to oil obtained from a rock and to pitch

Geology Of Petroleum

World's Production o

Crude Pbtrolehu Since

(After J. D. Northro

.2Ts 1,113.

Sto 265,782,

,870 33S,31E,6ai

ti.em

W,M2 S3.0E2

ma, SOS

204. 8 105, I2 181. SSI 474, J79 £83. 7M 07,aM

1.320.S28

4.S3T.8Ie

13,£4,5H 18,009, 407 23 [ 048 '787

3,181

15.774,6

], 456,918 jd,37S,42S 46,140,174

47,220,833 £4,399,568 61, 60S, 357

7S!779!417

8d!mo!o

Sos, 884 343,832 464, S37 515,268

63o!t30

692! 660

1.452!990

2,443.080

2!37e!l08

2! 346! 505

047. 28 24.112.529

Quulitj mukelaL 'EaluoaUd. 'loehidee Brituh Bonieo.

Introduction

ST Years and ConNnuiis, ] U. S. Geological Survey)

F 42 GaUjONb

Infia

"tSS"'

Pau

'S:

Trinidad

Esypt

Otbcr GMiniria

Total

YMt

I,9M,:7S

..Ims

M.730

..im

,m

M,I31

1 12,510

im

4M,g7e

1. 27,132

t7,B36

114,1119.183

. m

,!M

a

447,880

Sis, 292. 167

, 505

mi.m

282, 308

'13 174 Wm

z.9sa.e4G

40.S4S,712

411,000

2s,ooa

Isis

176.103,267

0.04 0 20

''ltim.tal ii. pirt.

n Cubi, 127,

>,udfi.S9

6 Geology Of Petroleum

used for making tight the seams of boats. The Persian fire worshipers had shrines at gas seepages in the Apsheron Peninsula, Russia, and until recent years the followers of Zoroaster made pilgrimages to that region and to Holy Island, nearby, in the Caspian Sea. There are numerous references to the bitumens in Greek and Latin Uterature. The Romans used petroleum in lamps. The bitimiens were obtained at oil seeps or springs or in shallow pits, dug at the surface, into which the oil would flow. '

Many place names refer to pitch or oil — for example, Pechelbronn (pitch spring), near Hagenau, Alsace; La Brea (pitch or asphalt), a name used for many places in Spanish countries; the Persian Kir, the Russian Neft, and the Burmese Yenang.

In modern times petroleum has been exploited for more than a century in Alsace, where deep shafts were simk into the oil-bearing formations. In Burma deep wells were put down by hand, and oil was bailed out of them with buckets. These methods are slow and laborious and because of the gas associated with petroleum are dangerous and frequently result in loss of life. The exploitation of petroleum on a considerable scale began about 1860, when modern drilling practice was introduced. The machinery and technology of drilling were developed largely in the Appalachian region, in the United States, and in the Petrolia region. Lambton County, Ontario, which were among the first regions to be exploited on the modern scale. The Canadian rig" and "American rig*' are widely used throughout the world.

Geographic Distribution Of Petroleum

On pages 4 and 5 is a table showing the production of petroleum to 1917, inclusive, with the percentage of the whole that each country produced. In order of output the countries rank as follows: United States, Russia, Mexico, Dutch East Indies, Galicia, Rumania, India, Japan, Canada, Peru, Germany, Trinidad, Argentina, Egypt, Italy. Since 1917 no large fields have been discovered or opened except in Persia and Colombia, of which the statistics are not available. Figs. 1 and 2 show the distribution of the oil fields. The United States and Russia together have produced about 87 per cent of the world's petroleum output to 1917.

'Thompson, A. B. : The Oil Fields of Russia, p. 96, London, 1904. Redwood, Boverton: A Treatise on Petroleum. Vol. 1, p. 48, London,

Introduction 7

North America has produced 64.31 per cent; Europe, including Russia, Rumania, Galicia, Germany, and Italy, has produced 30.60 perc ent ; Asia and Oceanica, including the Dutch East Indies,India, and Japan, 4.42 per cent; South America, including Peru, Trinidad, and Argentina, 0.43 per cent; and Africa, 0.04 per cent. The Western Hemisphere has produced 64.74 per cent, and the Eastern Hemisphere has produced 35.06 per cent of the total. Australia and Africa, except northern Egypt, are essentially improductive. The Northern Hemisphere has produced 96.95 per cent, and the Southern Hemisphere, including all of the Dutch East Indies (where some of the oil is found north of the Equator), Peru, and Argentina, has produced 2.85 per cent. It is noteworthy also that 92.29 per cent of the world's production has come from the north temperate zone, and the remaining 7.51 per cent has come from fields south of the Tropic of Cancer. The continents rank in order of output: North America, Europe, Asia, South America, and Africa. The most thoroughly explored coxmtries have been the most productive.

Clapp, who has devoted considerable study to both Asia and South America, states that the South American output will probably rise in the course of a few years to second place; although in his opinion 2 the final rank of the continents by total production, when fully developed, is likely to be as follows: North America, Asia, South America, Europe, Africa. This is a decidedly optimistic view of the future supply of Asia and South America, considering the great production of European Russia and the undeveloped territory on both sides of the Caucasus Mountains and in other parts of Russia in Europe.

In the immediate future Persia and Colombia are likely to become increasingly important as producers of oil, and an increased production is expected from Mexico and Oceanica. Except in the United States there has been very little development of territory far away from areas exhibiting surface indications of oil. Large production may be expected when the same methods of prospecting areas of favorable structure in consolidated rocks that are applied in North America shall be extensively applied in other fields.

Production of the Emba field, north of Caspian Sea is included with that of European Russia.

*Clapp, F. G.: Petroleum Resources of South America. Am. Inst. Min. Eng, BvU. 130, p. 1744.

Geology Of Petroleum

Fio. 1. — Map showing producing oil fields of Western Hemisphere. (A few

prospective fields are shoxon.)

Introduction

Fig. 2. — Map showing producing oil fields of Eastern Hemisphere. few

prospective fields are shown.)

10 Geology Of Petroleum

The United States, by bringing in new fields, has steadily advanced production. It is not expected that as many new fields will be discovered in the future. Probably some will be brought in, new pools on extensions of oil fields will be discovered, and deeper reservoirs will be developed in the producing fields. Nevertheless many investigators who have given most thought to the matter are of the opinion that the United States is not very far from the zenith of its production. As the world's greatest consumer of petroleum and its products the United States must look to foreign fields in the near future, or we must learn to do without some of the things which we have come to regard as necessary.

The world's oil supply has been discussed by Smith, and by White.

White gives an estimate, prepared by geologists of the United States Geological Smey, of the oil remaining in the strata in the United States, January 1, 1919. He states that the quantity available is 6,740,000,000 barrels. At the present rate. of consumption this would last the United States about 17 years. White published an estimate of the supplies of the principal countries' of the world that are known to contain oil. This estimate, which was prepared by Eugene Stebinger, is stated on page 11. The unused resources of the United States and Alaska are taken as the unit, 1.00, estimated to be 7,000,000,000 barrels.

Geologic Distribution Of Petroleum

Kinds oi Strata Containing Oil and Gas. — The world's petroleum comes from sedimentary beds, practically all of it from sands, sandstones, conglomerates, and porous limestones and dolomites. The deposits the world over are held in by coverings of shale, clay, or marl. The producing beds almost without exception are marine strata or strata of fresh-water origin that are closely associated with marine strata. The organic material from which the oil is derived finds lodgment in clays and marls when they are deposited, and the oil accumulates in sands and other porous rocks that are associated with the clays and marls, r The bodies of strata most

iSmith, G. C: a Foreign Oil Supply for the United States. Advance Publication No. 167, Trans., Amer. Inst. Min. Eng., February, 1920.

Whitb, David: Petroleum Resources of the World. Oil and Gas Jour., vol. 19, No. 2, pp. 76-82, and vol. 19, No. 3, pp. 64-62, 1920.

Reservoir rocks are discussed on p. 53; cover caps on p. 65.

Introduction

Oil Resources op Principal Oil Containing Regions op the World,

(Estimate of Eugene Stebinger)

County Or Region

United States and Alaska

Canada

Mexico

Northern South America, including Peru

Southern South America, including Bolivia

Algeria and Egypt

Persia and Mesopotamia

Southeastern Russia, southwestern Siberia, and the

region of the Caucasus

Rumania, Galicia, and western Europe

Northern Russia and Saghalien

Japan and Formosa

China

India

East Indies.

Total eastern hemisphere . Total western hemisphere Total north of equator . . . Total south of equator . . .

Relative

Millions of

Value

Barrela

7,000

4,625

5,730

3,560

5,820

5,830

1,135

1,235

1,375

3,015

43,055

21,255

21,800

36,400

6,655

k

'Oil and Gaa JournaU vol. 19. No. 3, p. 54. 1020.

common in oil fields are those in which thick shales, clays, or marls ) alternate with relatively thin sands.

Geologic Age of Strata Producing Petroleum and Gas. — Oil or

gas, or both, are fomid in strata ranging from the Cambrian to the Recent. Large amounts are found in the rocks formed during the Paleozoic, Mesozoic, and Cenozoic eras. All the oil produced in Europe and in Asia is derived from the Cenozoic formations, except a small production in Derbyshire, England, which comes from Paleozoic beds, and a small production in Galicia, Alsace and Hannover where oil is derived from the Mesozoic. In the Eurasian fields the Miocene and Oligocene are the most productive strata, although the Eocene yields considerable oil in Galicia.

In Mexico, Venezuela, and Argentina the principal producing strata are Cretaceous. In Colombia oil is derived from the Cretaceous and the Tertiary. The production of Barbados and most of that of Trinidad are derived from Miocene strata.

12 Geology Of Petroleum

In North America large amounts of petroleum are found in strata of Paleozoic, Mesozoic, and Cenozoic age. The Paleozoic strata produce the oils of the Appalachian region, the Illinois*field, and the Oklahoma, Kansas, and northern Texas fields. They yield also the oil produced in Canada.

The Cambrian has produced a little gas in New York.

Oil and gas are found in the Trenton limestone (Ordovician) in the Lima-Indiana field of Ohio and Indiana. The Trenton produces some oil also in southeast Illinois and in the Dover West field, just east of Lake St. Clair in Kent County, Ontario. In New York gas is derived from the Trenton.

The Silurian produces a little oil in the Appalachian field. It is the chief source of gas in the Clinton gas field of eastern Ohio, and it yields some gas also in Ontario, west and south of Niagara Falls,

The Devonian yields oil and gas in New York, Pennsylvania. West Virginia, Ohio, Kentucky, Tennessee, Indiana, and Ontario. In Pennsylvania both lower and upper Devonian are productive; in West Virginia the Chemung is barren but the Catskill is productive. In Canada limestone of the Devonian is the chief producing formation. The Devonian limestone has produced oil and gas also in eastern Kentucky.

The Mississippian produces oil in Pennsylvania, West Virginia, Ohio, Kentucky, Illinois, western Indiana, and Texas. In Pennsylvania, West Virginia, Illinois, and northern Texas it is highly productive.

The Pennsylvanian strata produce oil in the Appalachian region and in Illinois. Oil and asphalt are found in Pennsylvanian beds also near Princeton, Indiana. The Pennsylvanian Cherokee shale is the chief oil and gas bearing formation in Kansas and Oklahoma. The Pennsylvanian is productive also in northern Texas. Pennsylvanian rocks carry oil in the San Juan field, Utah. Some oil is found in the Embar (Pennsylvanian and Permian), near Lander, Wyoming.

A little oil is found in the Permian (Red Beds) in Oklahoma, at Virgin City, Utah, and in Pecos Valley, New Mexico. '

The Trinity sand (Cretaceous, Comanche) carries oil in the Medill field, Oklahoma, and asphalt in Pike County, Arkansas. At both places it is unconformable above the flexed and eroded Carboniferous beds that are believed to have supplied the oil.

The Upper Cretaceous carries the oil in eastern Texas and

Introduction 13

northern Louisiana and in the Big Horn Basin, Salt Creek, Big Muddy, and many other fields in Wyoming. A little oil is found in the Graneros (Benton) at Moorcroft, Wyoming, and in the Benton in the Labarge and Spring Valley fields, Wyoming. Oil is found in the Pierre (Upper Cretaceous) in the Shannon field, Wyoming; in fractured Pierre shales at Florence, Colorado; and in a sandstone included in the Pierre in the Boulder field, Colorado. Oil is found in the Mancos (Upper Cretaceous) in the Rangely field, Colorado, and possibly in the Mesaverde (Upper Cretaceous) in the DeBeque field, Colorado. In the McKittrick-Sunset region, California, a little oil appears in the Chico (Cretaceous) shales.

The Tertiary formations are important oil carriers in the Gulf coast fields — for example, Spindletop, Sour Lake, Saratoga, Batson, Dayton, and Humble, all in Texas, and Jennings and Anse La Butte, in Louisiana. In the Wasatch (continental Eocene) asphalt is found in the Uinta Basin of Utah and Colorado, and some oil is found also at Vernal, Utah. In the California fields the principal oil-bearing formations are Eocene (Tejon, Sespe, and Topatopa) and Miocene (Vaqueros, Monterey, Modelo, Puente, Santa Margarita, Fernando, and Jacalitos).

Oil is found also in Pleistocene beds in the Summerland and Puente Hills regions, California. Gas is found in Pleistocene beds of Lake Bonneville, Utah, and asphalt in Salt Lake.

Gum beds and a lubricating oil are found near the base of the glacial drift in Lambton County, Ontario. This oil obviously has escaped from lower beds.

The subjoined tables summarize the data as to the age of the principal reservoirs of oil and gas.

Geology Of Petroleum

Aqb or Principal Pbtbolbum Rksbrtoibs in thb Unitiio SrAnis

o

Pleistocene. . Pliocene. . . . Miocene. . . . Oligocene. . .

Eocene

Upper

Cretaceous Lower

Cretaceous Jurassic . . .

Triassic

Permian. . . . Pennsylvanian Mississippian . Devonian. . . .

Silurian

Ordovician. . . Cambrian

gas gas gas

s

H-

H- +

o O

+

M o

d

o

a ;4

o

.!

a

o

gas

S

+ +

4- +

little oil is found in the White River formation (Oligocene) in the Douglas field. bEmbar formation, parUy Pennsylvanian

Age of Principal Petroleum Reservoirs in*the Caribbean Region and

South America

Pleistocene. Pliocene. . . Miocene . . Oligocene . . Eocene. . . . Cretaceous. Jurassic. . .

o o

cs

'3

o

d

4-

+

0) N

cs-5 fls o

4 h gS

4-? 4-?

0 Q 08'

(3

tt

+

oJn Trinidad oil exudes from Pliocene strata, Miocene strata.

It is probably derived in the main from

Introduction

Age of Principal Petroleum Reservoirs in the Eastern Hemisphere

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Cretaceous

Jurassic

Triassic

Permian

Upper Carboniferous

Lower Carbonif er-

'+

is

Od

+

1=3

+

+

M 8

Aps

+ +

H

g

+

+

H

+

+

'+

Oq

+

+

a

ous.

+

Subordinate.

Miocene subdivided into Maeotie, Sarmatian. Tortonian, Helvetian, and Burdigalian; each carries petroleum in places.

cirrawady River fields, include Yenangyaung and Yenangyat-Singu.

''In Alsace the principal petroliferous series is lower Oligocene and includes marine and nonmarine sediments. A little oil is found in Mesosoic rocks.

The upper Oligocene is the richest petrolileroua formation.

/Probably upper Olifrocene.

Eocene is the most important eeriea.

Chapter Ii

Surface Indications Of Petroleum And Materials

Associated With It

Indications of oil deposits include oil and the materials that have been formed by the drying of oil — asphaltum, gilsonite, paraffins, maltha, etc. — as well as the common associates of oil, such as bituminous rock, oil shale, burned shale, gas, salt water, and in some regions sulphur and its compounds and acid waters. Mud volcanoes and in some regions mud dikes, indicating the existence of mud volcanoes that have been eroded, are evidence of gas. In places "paraffin dirt" (see page 36) has been found above deposits of oil or gas.

Any indication of oil or gas is to be interpreted in connection with its geologic setting, namely, the rock column, the structure.

Fig. 3. — Sketch showing oil seeps at outcrop of petroUferous stratum and an accumulation, of oil and gas (black) many miles away down the dip from the outcrop.

and the degree of metamorphism shown in associated beds that may be present. The geologic conditions at the surface — the rocks present and their attitude — are indications of what may be expected at depths. These are treated in other chapters.

Distribution. — Oil springs or asphaltites are found in many oil fields and are generally regarded as favorable indications. The springs may exude at outcrops of the oil sands or limestones in which the oil is stored (Fig. 3), or they may exude from fault fissures, joints, or other conduits in beds that cover le oil-bearing stratum. Where oil exudes from the oil-bearing stratum the springs merely indicate that the stratum is petroliferous and that the deposits are being scattered. Petroleum deposits commonly are not situated below the points of issue, but in some regions they

r.'

Surface Indications Of Petroleum

Classification Of Hydrocarbons And Allied Substances

(After Blake, Eldridge, and Others) Classification of Natural Hydrocabbons

("Natural gaa."

Oq

a

O

Fluid.

f Naphtha. Petroleum.

Viscous (malthite)

Maltha. Mineral tar Brea. Chapapote.

Bituminous. . . Elastic

[Asphaltite

Solid. . .

Coal

Resinous.

, jElaterite (mineral caoutchouc). \Wurtzilite.*

Albertite Impsonite. / Grahamite. Nigrite. Uintaite (gilsonite).

Lignite.

Bituminous coal. Semibituminous coaL Anthracite coal.

(Succinite (amber). Copalite. Ambrite, etc.

Cereous.

Crsrstalline

Ozokerite. Hatchettite, eto.

Fichtelite. Hartite, etc.

aWurtiilite might perhaps better be classed with the asphaltites.

are down the dip many miles away, at places where the structure is

favorable for retaining oil. In southeastern Kansas, southwestern

Missouri, and northeastern Oklahoma the Pennsylvanian oil sands

that yield prolific supplies farther west in Oklahoma and Kansas

are exposed at the surface. Here and there along their outcrops

'Adams, G. I., Haworth, EaASMUs, and Cranb, W. R.: Economic Geology of the lola Quadrangle, Kansas. U. S. GeoL Survey Bull. 238, p. 16, 1904.

Geology Of Petroleum

/

Classification op Natural and Artificial Bituminous Compounds

(After Eldridge)

Mixed with limestone fSeyssel, Val de Travers, Lobsan, Utah, ("asphaltic limestone") and other localities

Mixed with silica and sand f California, Kentucky, Utah, and other ("asphaltic sand"). localities. "Bituminous silica."

a

o o

n

O

a

("asphaltic earth"). ' ' '

Bituminous schists (Canada, California, Kentucky, Virginia,

1 and other localities, pi Jxhick oils from the evaporation of petro- I leum.

o

5S

Viscous.

Solid.

f Gas tar. \Pitch.

f Refined Trinidad asphaltic earth. I Mastic of asphaltite.

) Gritted asphaltic mastic.

Paving compounds.

and also in the zinc mines of the Joplin region, deposits of bitumen and of partly dried out oil are found in considerable quantities at the base of the Pennsylvanian strata. At Tar Spring, six miles north of Miami, Oklahoma, a heavy bitumen oozes in considerable quantities at the base of the Pennsylvanian. At that horizonthe bitumen is so abundant as to interfere with prospecting for metals with the chum drill. These deposits are surface suggestions of the Oklahoma-Kansas oil fields, which lie many miles to the west. Above the oil pools themselves, oil seeps are generally lacking in this region.

Not all petroleum springs, asphaltite deposits, and gas seeps occur at the outcrops of the oil sands or other oil-bearing formations. In some regions these evidences of oil are found at the crests or on the flanks of anticlines, where the oil has seeped through the cover of the reservoir. (See Kg. 4.) Where the hydrocarbons escape through fissures or joint planes, valuable deposits may occur not far away, or even directly below their places of issue. In many

*SiEBENTHAL, C. E. I Origin of the Zinc and Lead Deposits of the Joplin Region, Missouri, Kansas, and Oklahoma. U. S Geol. Survey BvJH, 606, p. 205,

Surface Indications Of Petroleum 19

fields surface evidences of oil are very clearly exposed at or near the tops of structural features that have yielded oil. This is very common where rocks are unconsolidated and is a noteworthy feature of many fields where Tertiary beds are petroliferous. In California, on the Gulf coast, in Alsace, Galicia, Rumania, Baku, Russia, Burma (Yenangyaung and Yenangyat), Java, Sumatra, and elsewhere in Oceanica either asphalt, oil seeps, gas seeps, mud volcanoes, mud dikes, or salt springs appear near or directly above deposits of petroleum. In some of these districts it is clear that oil or gas has issued through fissures at or near the tops of the petroliferous folds.

In North America superficial indications of oil are found in many oil-bearing regions. Oil Spring, in Allegany County, New York, and Oil Creek, in western Pennsylvania, were known before the Appalachian oil field was exploited. At Smith's Ferry, in the

Oil Seeps

0 /OMiks

Fig. 4. — Sketch showing oil seeps at crest of fold above oil accumulation

(black).

Beaver quadrangle, Pennsylvania, the oil floating on the Ohio River was gathered and sold as "Seneca oil" f or "medicinal purposes. In West Virginia a grahamite dike was worked before the Appalachian field was developed. Burning SpringspWest Virginia, is at a gas seep on the Burning Springs- Volcano-Eureka anticline, which has yielded much petroleum. At Oil- Springs, Lambton County, Ontario, a liquid extracted from the "gum beds'' yielded "gum oil," before the Oil Springs dome was exploited for petroleum. Oil seeps were found upon the Salt Creek dome, and on many other uplifts in Wyoming. An oil spring exists in the Boulder field, Colorado, although it was not this spring that led to drilling. An oil seep issues not far from the productive part of the Florence field, Colorado. Oil seeps or asphalt deposits are present

WooLSEY, L. H. : Economic Geology of the Beaver Quadrangle, Pennsylvania. U. S. Geol. Survey . 286, p. 76, 1906.

Williams, M. Y.: Oil Fields of Southwestern Ontario. Canada Dept. Mines Summary Rept., 1918, part E, p. 30, 1919.

20 Geology Of Petroleum

in the San Juan field, Utah. In the California oil fields asphalt is almost invariably present in large amounts, and oil seeps and tar springs abound. Such evidences are present in the Coalinga, McKittrick, Sunset, Santa Clara, Santa Maria, Summerland, Puente Hills, Los Angeles, and some other fields.

In some fields where oil seeps are lacking gas seeps have led to drilling.

At Findlay, Ohio, gas issuing into cisterns led to the discovery of the field. The Caddo field, Louisiana, was drilled because of the gas bubbling up in Caddo Lake.

In the ''salt dome'' fields of the Gulf coast, surface indications of oil and gas abound. Because much salt and sulphur are associated with the oil these substances also, when appearing at the surface, are regarded as indications of petroleum. Small moimds rising above the general level of the flat country mark some of the oil districts and have led to drilling. Not all the moimds have proved productive, and not all the districts are on mounds, but practically all the producing pools are marked by the escape of gas. Gas bubbles in water or gas seeps were noted at Spindletop, Sour Lake, Saratoga, Batson, Dayton, and Humble, Texas, and in the Jennings field and at Anse La Butte and Welsh, Louisiana. Sulphur was noted in the soil at Spindletop, and "sour" water at Sour Lake and Saratoga, Texas. At Sour Lake oil and asphalt appeared ilso, and at Saratoga, oil.

In the Tuxpam-Tampico field, Vera Cruz, Mexico, the rocks dip / eastward from the mountains to the coast at low angles. At many, places dikes, sills, and stocks of basaltic rocks intrude the sedimentary beds. Most of the surface indications of oil are closely associated with the basalts, and hundreds of them occur throughout the plain. Among the locaUties where oil seeps are abundant are Panuco, Dos Bocas, Casiano, Tres Hermanos, Ojo de Brea, Chapapotillo, and Monte Grande.

Manjak, a tar formed by the drying of oil, is exploited in Barbados, where it is found at the outcrops of Miocene sandstones and shales. Earth saturated with tar is found at Tarry Gully, near St. Andrew. At the "boiling spring" near St. Andrew inflammable gas issues from a pool of water. Wells sunk in the Miocene of Barbados yielded a little oil.

'Garfias, V. R. : The Effect of Igneous Intrusions on the Accumulation of . Oil in Northeastern Mexico. Jour, Geology vol. 20, p. 666, 1912.

Surface Indications Of Petroleum 21

J

Trinidad Island has one of the largest deposits of asphaltum known. Pitch Lake, at La Brea, which lies southwest of San Fernando, is 137 acres in extent and has produced over 2,000,000 tons of asphalt. A heavy viscous asphaltic material rises slowly into the lake. In recent years an oil field of considerable size has been developed not far from La Brea.

In a spring at Pechelbronn, Alsace, was discovered in 1498 an oil which issued with the water and would bum in lamps. In 1735 the outcrop of an oil sand was detected about 500 feet from the spring, and oil was distilled from it in an iron retort. Subsequently this sand was mined from a shaft, and still later this field was developed with shafts and borings.

In GaUcia oil was collected at the surface and in shallow wells in the earUest historical era. The Boryslaw-Tustanowice field, the most productive in the coimtry, was noted for its oil springs long before deep exploitation was begun. At Schodnica oil from beds near the surface was produced before deep drilling was attempted. In and around Boryslaw ozokerite deposits were worked before the field was drilled for oil. Most of these deposits were exploited in shallow shafts, but later it was found that they extended to very great depths below the surface.

In Rumania there is a large body of oil-bearing strata, and at many places where they crop out there are clear evidences of petroleum. In the Prahova and Bercu districts numerous pits were dug for catching oil. The mud volcanoes of the Berca and Beciu region are famous. There for about seven miles mud volcanoes, oil seeps and salt springs are closely spaced. In this region at many places oil is obtained from hand-dug shafts.

In the foothills of the Caucasus Mountains in Russia gas and oil seeps are numerous. The Balakhany-Sabunchy-Romany field is an elongated dome where along the main upUft there are mud volcanoes, many of which spout mud, petroleum, gas, and water. Of these the Bog-boga is over 100 feet above the plateau. A short distance from this field is the Surakhany field, where gas was obtained from seeps by the fire worshipers, for use in their temples for 2,500 years. Off the coast of Bibi-Eibat, in Baku Bay, on the Caspian Sea, so much gas rises in the water as to agitate it vigor* ously, and when lighted on a calm day the gas will bum.

The Grozny field, in the northern foothills of the Caucasus, is

Thompson, A B.: Oil-field Development, p. 179, London, 1916.

22 Geology Of Petroleum

on an anticline miles long. The surface indications include oil seeps, and oil was recovered from hand-dug wells before the field was driUed.

. The Maikop field, Kuban, Russia, is 300 miles west of Grozny. Here Cretaceous beds are. formed in gentle folds and are imcon- f ormably overlain by Tertiary beds that dip at low angles. The Tertiary rocks consist of sand and shale, and where they crop out the sands are so highly impregnated with oil that it oozes out when the sand is squeezed in the hand.

Holy Island, in the Caspian Sea off the Apsheron Peninsula, is a faulted dome. According to May, there are ten or twelve mud volcanoes and seeps in the faulted region. Beds of asphalt and small lakes of oil are forming today. Cheleken Island, in the Caspian Sea, is another faulted dome, in which hot salt springs issue and deposits of ozokerite are found in faults. South of the Caucasus, in the Tiflis legion, evidences of oil are numerous and have led to the development -of a comparatively small oil field. In the Ferghana district, Tiurkestan, oil seeps abound.

In Egypt, on the coast of tlie Red Sea near the mouth of the Gulf of Suez, is the mountain as Gebel Ziet (oil mountain), called by the Romans, Mons Ftrolius. Here limestone, gypsmn, and clays are impregnated with oil and gas. This material was formerly used for patching boats and wrapping mummies by the Egyptians. Recently a considerable oil field has been developed in this region.

In Mesopotamia, in the region of the lower Euphrates and Tigris, oil seeps are numerous and have furnished material for calking boats and similar purposes since a time long before the Christian era. No considerable oil field has been developed nearer thian the Persian field, to the east.

In the Yenangyaung (earth-oil creek) field, Biurma, India, on the JLrrawady River, oil seeps in Tertiary rocks are numerous, and the Burmese recovered considerable quantities of oil by sinking shallow shafts. Mud dkes are found in the Pegu and Irrawady formations and are supposed to fill the conduits through which mud volcanoes were fed at a time before the mud volcanoes were eroded. Yenangyat (earth-oil place), Burma, is on an elongated dome.

Trench, R. H. : Discussion of paper by A. B. Thompson in Min. and Met. Inst. Trans., vol. 20, p. 247, 1911. 'Idem, p. 248.

Surface Indications Of Petroleum 23

Petroleum springs were long ago recognized there, and many of them are approximately at the crest of the fold.

Oil occurs in many islands of the Oceanica group. In Java oil seeps are numerous along the crests of folds which trend parallel to the length of the island. These have led to the development of proUfic oil fields. Similar conditions are found in Siunatra and Borneo.

In the Philippine Islands oil and gas seeps are found in seven or eight regions, though no commercial supplies have yet been exploited. At Villaba, at the northwest end of Leyte, considerable quantities of asphaltum occur, probably along a fault which cuts through limestone and sandstone.

In Japan there are many seeps in the oil fields, and shallow wells were formerly dug to collect oil.

In Colombia oil seeps are numerous in many districts. Mud volcanoes are abundant in the Tiurbaco field of the Caribbean district and in the Tubara field, 20 miles east of Cartagena. One hundred mud volcanoes are said to occur in an area of 3 acres near developed oil wells. Oil is associated with the coal series on the Baudo River and may be seen floating in the Andagueda River, a tributary of the Atrato. In the Magdalena-Santander district there is a large and promising area where oil seeps are common.

In northern Argentina and Bolivia, east of the Andes, oil springs are abundant over a large area. It is believed by some that a large oil field will be developed in this region.

In some fields oil and gas seeps are lacking. The principal oil fields of Illinois show no surface indications, although in one unimportant field a little oil seeped through a deep boring into a coal mine. The Rivadavia field, the principal oil-producing region in Argentina, was discovered by accident in sinking a well for water. The Roma gas field, Queensland, Australia, which is not commercially productive, was discovered by drilling for water. [Ofleeps. — Oil seeps are evidences that oil exists in the region inmich they are found, though in many regions that contain oil seeps considerable drilling has not disclosed commercial supplier for example, the fields on the northwest coast of Newfoundland, on Gaspe Peninsula, Quebec, and near Albert, New Brunswick. Most of the large oil-producing regions of the world, however, contain oil seeps at one place or another, although numerous individual pools in these regions do not lie below the seeps. Many oil seeps

/

24 Geology Of Petroleum

are associated with springs of water. In some there is merely a slight iridescent film or "rainbow" of oil above the water. Such a film resembles somewhat the film of iron oxide that covers some pools of water, and iron oxide films have been mistaken for oil fihns. The iron oxide film differs from the oil film, however, in that it is brittle and will break if the water is agitated, whereas the oil film will not. In many oU springs the oil on the water forms a considerable layer. At some places it is collected by laying a blanket on the pool. The blanket absorbs the oil and is wrung out and the oil recovered. In other springs the oil is skimmed off.

Oil Spring, in Allegany County, New York, was exploited long before the Appalachian oil field was developed. It was described by Benjamin SiUiman in 1833 as follows:

oil spring or fountain rises in the midst of a marshy mound; ft is a muddy and dirty pool, about eighteen feet in diameter, and it is nearly circular. There is no outlet above ground — no stream flowing from it, and it is of courae stagnant water, with no other cirQulation than that which springs from changes of temperature and from the gas and petroleum which are constantly rising through the pool. The water is covered with a thin layer of the petroleum or mineral oil, giving it a foul appeance, as if coated with dirty molasses, having a yellowish-brown colorJThey collect the petroleum by skimming it like cream from a muk pan. It has then a very foul appearance, like very dirty tar or molasses. Silliman states that cattle like to drink the water of the spring.

When the amount of oil from a well or pool is very small, it is sometimes difficult to ascertain whether or not a steady flow of oil exists. Pools of water contaminated with oil that has been used to lubricate machinery or for other purposes have been mistaken for oil springs. Thpetrolemn of sprVngs is generally heavy, because it has suffered evaporation or oxidation or both, and that of some springs resembles lubricating oil in appearance, but often tests or analyses will show whether the oil of a spring is in the natural state or whether it is a product of refining.

A few oil springs jdeld conunercial supplies of oil. One at Urado, in the Uinta Basin near. the Colorado-Utah line, has been opened by a short tunnel and supplies several barrels of high-grade lubricating oil daily from flat-lying sands. Many oil springs in

SnjiiMAN, Benjamin: Notice of a Fountain of Petroleum, Called the Oil Spring. Am, Jour. Sci., vol. 23, pp. 97-99, 1833 (SiUiman'a Journal),

Surface Indications Of Petroleum 25

Galicia, Rumania, Russia, Burma, Oceanica, and Japan have been exploited by digging trenches, shallow pits, and wells into which the oil can flow. At some places enormous quantities of oil flow out at the surface. At Pitch Lake, Trinidad, enough has issued to make on drying over 3,000,000 tons of asphalt. At AUat railway station in the trans-Caucasus region, Russia, east of the Caspian Sea, in 1908 and 1909 so much oil issued from fissures that it formed large lakes inundating the railway tracks.

Oil Ponds. — At some places oil has been noted above the surface of the sea, where it has issued from oil springs on the sea bottom] According to Thompson,* oil has been observed in the Pacific on the coast near the oil fields of northern Peru. Fenneman' mentions oil ponds in the Gulf of Mexico oS the coast of Texas, where ships find quiet water during storms. Off Galeata Point, at the southeast corner of Trinidad, submarine eruptions accompanied by discharges of petroleum and pitch ai*e recorded.'* Holland describes an island off the northwest coast of Borneo that was made by an oil eruption. This island was 210 by 120 feet and was forty feet high. Thompson* states that at many localities in the Caribbean Sea off the coast of Mexico vast quantities of oil are periodically ejected, covering the sea for miles.

PSolid Bitumens. — Asphaltite is a general term applied to solid asphaltic hydrocarbons. Between oil and asphalt there are all stages, grading from the Uquid to the solid state Many of the soUd hydrocarbons have been described and niimed aa distinct species. These include gilsonite, uintaite, elaterite,. wurtzilite, albertite, grahamite, and many others.' They vary greatly in

Thompson, A. B.: Oil-field Development. P. 175, 1916.

cU., p. 180.

'Fenneman, N. M. : Oil Fields of the Texas-Louisiana Gulf Coastal Plain. U. S. Geol. Survey Bull 282, p. 74, 1906.

Thompson, A. B., op. cU., p. 180.

'Holland, T. H.: Discussion of paper by A. B. Thompson in Inst. Min. and Met. Trans., vol. 20, p. 233, 1911.

Op. cU., p. 179.

ELDRmoB, G. H. : The Asphalt and Bituminous Rock Deposits of the United States. U. S. Geol. Survey, Ttoentp'second Ann. Rept., part 1, p. 220, 1901.

Clabkb, F. W.: The Data of Geochemistry, 3d ed. U. S. Geol. Survey BvU. 616, p. 719, 1916.

Blake, W. P.: Uintaite, Albertite, Grahamite, and Asphaltum Described and Compared, with Observations on Bitumen and Its Compounds. Am. Inst. Min. Eng. Trans., vol. 18, p. 563, 1890.

26 Geology Of Petroleum

composition; most of them are mixtures of hydrocarbons. Ozokerite is largely parafi and is an important source of that material.

As a rule the asphaltites that are found at the surface contain considerable material other than the hydrocarbons. The asphalt of Pitch Lake, Trinidad, is about one-third sand and clay, onethird water, and one-third bituminous matter. Many asphaltic sands and bituminous limestones carry from 5 to 20 per cent only of bituminous matter (p. 27). Other bitumens are nearly pure, among them the gilsonite dikes of Uinta Basin, Utah, the grahamite dike of Ritchie County, West Virginia, and the ozokerite deposits of Galicia. Bitumens that have been deposited as dikes, especially those deposited as dikes in consolidated rocks, are commonly pure. These are sought for fuels, for making varnishes, and for many other purposes.

Asphalts, as already stated, are formed by the mspissation or drying out of petroleum. They may be regarded as the residual products of natural distillation in which the more volatile fluids are generally scattered. The process is commonly attended by the oxidation of certain constituents, and the oil becomes less readily inflammable. y/ The drying out of petroleum is undoubtedly by far the most common method of formation of bitumens. Some, however, are foimd in coal and are believed to be derived from vegetable resins. Others are associated with metallic ores, and it has been suggested by some writers that these have originated at deep sources in connection with volcanic processes. Bitumens are associated with many quicksilver veins of California and elsewhere, and with the vanadium veins of Minasragra, Peru. As a rule the deposits of bitumen in coal and in metalliferous veins are relatively small. Some of the deposits derived from the drying out of petroleum are very large. The great Pitch Lake of Trinidad has been mentioned. At many other places in Trinidad there are enormous deposits of asphalt mingled with the soil. On the mainland in Venezuela the Bermudez deposit of asphalt is of the same order of magnitude. The gilsonite dikes of Utah are extensive. Eldridge estimated the amount in three of them to be 30,674,613 tons. At many places

Becker, G. F.: Geology of the Quicksilver Deposits of the Pacific Slope. U. S. Geol. Survey Mon. 13, pp. 286, 360, 372, 1888.

*Hbwett, D. F. : Vanadium Deposits in Peru. Am. Inst. Min. Eng. Trans.y vol. 40, pp. 279-280, 1910.

Surface Indications Of Petroleum 27

in California asphalts cover large areas. In Oklahoma, in Texas, and in Kentucky large deposits of solid bitumens have been exploited. In some other regions deposits of asphalt are small. Where they are formed by leakages from outcropping petroliferous strata they are commonly closely spaced.

Bone Deposits in Asphalt. — In the petroleum-bearing area near ' Los Angeles, California, enormous deposits of impure asphalt are found at the outcrop of an oil sand and in the wash above the sand. From a pit dug in the asphalt numerous skeletons of animals that lived in comparatively recent times are foimd. These remains include the skeletons of saber-tooth tigers, deer, and other animals. The deposit is a conglomerate of bones held together by solid or semi-solid bitumen. A little oil exudes in the bottom of the pit. The bones lie closely spaced. Evidently the animals went to a spring to drink water, perhaps somewhat salty, and became immersed in the sticky matter. Hundreds of skeletons have been taken from a small pit. Thompson notes pitch springs in Peru with abundant bones, and he notes the presence of similar deposits in Sviatoi (Holy Island), in the Caspian Sea. f Bituminous Rocks. — Sandstones and limestones at many places are filled with dried or partly dried petroleum. There are all gradations between impure asphalts and bituminous sandstones. The bituminous material in some beds is formed from petroleum that has risen in springs. An example is that of the "gum beds" of Oil Spring, Ontario. 2 In others the bituminous material is that which has remained in the beds after they have been drained of oil. Washbume estimates that 60 per cent of the oil stored in sandstone strata is ordinarily removed from them by wells. Adsorption of oil by sand grains is high, and some of the oil remains even after repeated washings with water. If a saturated sand wth 20 per cent porosity is drained and it retains 40 per cent' of its oil, the oU would equal 8 per cent of the volume occupied by the sands.

Probably the largest body of bituminous material in the world is the deposit of "tar sands" on the Athabasca River in northern

Eldridge, G. H., and Arnold, Ralph: The Santa Clara Valley, Puente Hills, and Los Angeles Oil Districts, Southern California. U. S Geol. Survey BuU. 309, p. 140, 1907.

'Williams, M. Y.: Oil Fields of Southwestern Ontario. Canada Dept. Mines Summary Rept., 1918, part E, p. 34, 1919.

Wabhburnb, C. W. : The Estimation of Oil Reserves. Am. Inst. Min. Eng. Trans.y vol. 51, p. 646, 1916.

28 Geology Of Petroleum

Alberta, which covers an area variously estimated at 2,000 /to 10,000 square miles. The sands are about 200 feet thick and are estimated to contain 14 gallons of oil to the ton. They are of Cretaceous age (Dakota or approximately Dakota) and rest on Devonian limestone. In cracks and joint planes of the Devonian rock pitch has hardened, and Bell states that the petroleum in the sands has passed upward through the Devonian limestone at a remote period.

Many petroliferous strata contain at their outcrops a little residual bituminous matter that is not evident on inspection of the outcrop, although the rock if broken under water may yield an iridescent film of oil.

Test For Oil In Rocks

(After Woodruff)

1. Select a representative specimen of rock to be tested. It is generally advisable to obtain several samples as large as one to five pounds each.

2. Break them up, and thoroughly mix the pieces. If the samples consist of sand, mix the sand.

3. Dry the sample on a plate in the sun or over a radiator. Do not dry it over a fire; to do so may drive the oil from the rock or sand.

4. Crush the sample to a powder. Mix the powder. Loose sand does not need to be crushed.

5. Place about a tablespoons ul of the sample in a bottle. Pour chloroform or carbon tetrachloride over the sample until it is thoroughly saturated and there is about half a tablespoonful of the liquid above the crushed rock or sand. Cork the bottle, but not too tightly. Shake occasionally for 15 or 20 minutes.

6. Place a white filter paper in a glass funnel over a white dish.

7. Pour the contents of the bottle into the funnel. After the liquid has passed through, place the white dish in a window where the liquid can evaporate.

8. Examine the filter paper. If the rock contains more than a trace of oU, there will be brown or black ring on the filter paper.

9. After the liquid in the dish has evaporated, examine the remaining substance. It is the petroleum which was in the rock.

Apparatus for Testing

One dinner plate on which to dry specimens.

Some means for crushing rock.

One or more bottles, 4 or 6 ounce size, with corks, in which to treat the rock.

iBell, E. C. : Geology and History of the Canadian Field. OU and Gob Jour. Suppl., May, 1919, p. 259.

*, Robert: The Tar Sands of the Athabasca River, Canada. Am. Inst. Min. Eng. Trans,, vol. 38, p. 838, 1907.

Surface Indications Of Petroleum 29

CUorbfonn or carboo tetnichloride.

One glass funnel 3 or 4 inches in diameter.

Two dosen round filter papers, 6 inches in diameter.

Two or more white dishes.

Bituminous Dikes. — BitumiuouB dikes are formed where petrolemn enters fissures and becomes hardened before it reaches the surface. The process of hardening is brought about by the loss of more volatile constituents and probably in some places by oxidation. Such dikes, during their formation, probably feed gas and oil spring at the surface.

One of the best known bituminous dikes is the albertite dike in

New Brunswick. In this region Paleozoic limestone, shale, and sandstone are folded and at some places on edge. The Albert formation, which consists in places of bituminous shales and sands, is probably of Devonian age, althoih it has been placed by somf: in the lower Carboniferous. It yields as much as 50 gallons of shale oil to the ton and has been distilled on a commercial scale. Surficial indications of oil are widely distributed in this region. The Albert shale under cover of overlying rocks has been penetrated by the driD and yielded considerable quantities of gas and some oil. The only lane albertite dike is that at the Albert

30 Geology Of Petroleum

mine. This dike was worked to depths of 1,100 feet or more and for half a mile along the strike. At places it is 15 feet wide and sends out apophyses into the country rock. It is nearly straight, stands approximately vertical, and follows the general direction of an anticlinal axis. It has yielded over 200,000 tons of albertite.

In Ritchie County, West Virginia, there is a dike of grahamite,* much like the albertite dike of Nova Scotia. This dike (Fig. 5) is nearly a mile long and about 5 feet wide for the most part, thinning out to a few inches at the ends. It stands nearly vertical. The fissure that is filled with grahamite, according to Fontaine, is a zone of fracturing, probably one of sUght displacement. As noted by White the fissure strikes almost at right angles to the great Burning Springs- Volcano-Eureka anticline, which produces oil west of the deposit. The fissure is supposed to have been made by tension during the formation of the anticline and was filled with petroleum largely from the Cairo sand, which lies at a depth of 1,530 feet* and is the main producing rock of this region. The Big Injun sand below, at a depth of 1,652 feet, also may have contributed petroleum. The oil filling the fissure, according to White, was gradually converted by oxidation and other processes into grahamite.

Grahamite dikes are found also in south-central Oklahoma.

In the Uinta Basin, Utah, lower Tertiary beds consisting of shales, sandstones, and limestones of the Wasatch and Green River formations dip northward at low angles toward the Uinta Mountains. The section includes several hundred feet of the Green River oil shales, which on heating will yield large amounts of shale

*Ells, R. W. : The Bituminous or Oil Shales of New Brunswick and Nova Scotia. Part 2, p. 9, Canada Geol. Survey, 1909.

Young, G A. : Twelfth Internat. Geol. Congress Guide Book No. 1, part 2, pp. 366-367, 1913.

Clapp, F. G., and others: Petroleum and Natural Gas Resources of Canada Part 2, p. 50, Canada Dept Mines, Mines, Branch, 1915.

Fontaine, W. M. : Notes on the West Virginia Asphaltum Deposit. Am. Jour. Sd., 3d ser., vol. 6, p. 409, 1873.

White, I. C: Origin of Grahamite. Geol. Soc. America Bull,, vol. 10, p. 278, 1899.

Eldridge, G. H.: The Asphalts and Bituminous Rock Deposits of the United States U. S. Geol. Survey, Twenty-second Ann, Rept., part 1, p. 235,

Winchester, D. E.: Oil Shales of the Uinta Basin. U. S. Geol. Survey Bull. 691, p. 27, 1919.

Surface Indications Of Petroleum

oil- In this region dike hydrocarbons are developeil in great variety. Asphaltic dikes consisting of gilsonite (Fig. 6),elatrite, tabbyite, albertite, wurtzite, and nigrite are developed and also dikes of paraffin, ozokerite. The asphaltic dikes are found both above and. below the oil-shale formation, and the ozokerite dikes below it. The gilsonite dikes are very large and extend for many miles along the strike. Eldridge" digested that the hydrocarbons that filled the dikes were derived from Cretaceous shales and that they came from below under pressure. Winchester, however, regards as plausible the hypothesis that the Green River oil shale supplied the material for all the bituminous dikes of the Uinta Basin, as well as the aaphaltic material that saturates certain sandstones in the region.

Deposits of solid bitumen in the form of dikes are commonly associated with gas. In the ozokerite mines of GaUcia strong currents of air are blown into the galleries to remove the gas and prevent injury to the miners. In the Old Black Dron gilsonite mine, near Black Dragon station, Utah, no explosives are used, and possession of matches in the mines is prohibited under threat of dismissal. Electric lights only are permitted. A disastrous explosion which caused the death of several men is supposed to have resulted from the striking oi a match by a miner in dehance of orders. The fire which ensued melted some of the gilsonite and caused it to run down into the old

stopes, so that after the mine was reopened gilsonite was being mined in the same places from which gilsonite had been removed before the explosion.

Ozokerite, or mineral wax, is a native bitumen with a paraffin base. It is essentially paraffin. It is found in Gahcia, in England, on Cheleken Island in the Caspian Sea, in the Salt Creek region of Wyomii, and in the Uinta Basin in Utah. It is Bup-

Op. cU., p. 351.

Vp. cU., p. 49.

f 4 eFftt

Fio. 6.— Sketch of gilsonite dike, Ducheane Mine, Uinta BasJD, Utah. (A/(er 'Eldridge.) The gilsonit is black, a, sandstone walls of dike : t>, fragments of sandstone in dike.

32 Geology Of Petroleum

posed to be fonned by the drying out of paraffin oil. Considering its orin, its occurrence at depths of nearly 2,000 feet at Boryslaw, Galicia, is noteworthy.' {Fig, 7.)

In the Salt Creek region, Wyoming, according to Wegemann,* ozokerite is associated with calcite, which fills all fault uree at the surface. It is produced by the evaporation of oil that has risen in these fissures and long remained in them. The deposits of ozokerite appear to be confined to the dome above the oil pool and are not found in the adjoining synclinea, in which shale oil is

iDd while

lUilUlIc .htl.(].w.

) 1 O"""

encountered. This relation is suggested also by the section in Fig. 7.

Many natural oils carry paraifin in solution. When these issue in wells, owing to relief of pressure and consequent decrease in temperature, some of them deposit paraffin in the bores. Probably some ozokerite dikes are similarly fonned where oil escapes through fissures.

ZuBER, Rudolph: Die Geologische Verhaltnisse von Borydaw in Ostgalizien. Zetttehr. prakt. Geologie, 1904, pp. 41-48.

Weqemank, C. H.: ITie Salt Creek OU Field, Wyoming. U S. Geol. Survey BvU. 670, p. 36, 1911.

Surface Indications Of Petroleum 33

Gas Seeps. — Gas accompanies the oQ that issues at many oil springs. There are also many gas seeps where no oil issues. Because the gas is colorless and some of it odorless, gas seeps are not so easily recognized as oil seeps. Many of theni have been recognized where the gas issues as bubbles in pools of water or by explosions of the gas resulting from accidental ignition. Where the gas is under pressure and the seep is in a sand or soft sandy earthy the movements of the sandy or clay particles may lead to the discovery of gas. The issue of gas under pressure may build up small "pimples," mounds, or mud volcanoes on the surface, which are easily recognized. Where heavy, lethal gases issue in depressions, animals exposed to them are killed, and the remains mark the places of accumulation.

The gases that issue at the surface of the earth include chlorine, nitrogen, carbon dioxide, carbon monoxide sulphurous compoimds, methane, and other hydrocarbons. Chlorine, nitrogen, and carbon dioxide have little significance as surficial indications of petroleum. They are not inflammable, and they issue in regions where volcanic processes are active or have recently been active, and elsewhere. Carbon monoxide is not ordinarily abundant in gas seeps, although a little may be present associated with other gases. Carbon monoxide and methane are the "fire damp" of coal mines.

Carbon dioxide, carbon monoxide, and gases other than the hydrocarbon gases are found under many geologic conditions. They are comparatively rare in considerable amounts in association with petroleum, although one or more are present in some petroleum gases, mixed as a rule with much larger quantities of methane. The hydrocarbon gases are commonly associated with oil and are more significant as indications of oil than carbon dioxide and carbon monoxide. Helium is found in some natural gases (p. 82).

The most common constituent of natural gases is methane. Methane gas, however, is not all associated with petroleum deposits. It is "marsh gas," which forms in peat bogs or anywhere that vegetation is decaying. The "will-o'-the-wisp" of the marshes and swamps is burning methane. It occurs in swamp deposits that are buried below glacial lacustrine clays in Minnesota and bordering States. In many fields, however, as stated above, methane is associated with petroleum. Commonly the methane contains also small amounts of other gases. In some fields ethane,

Geology Of Petroleum

propane, and butane are associated with methane. These and heavier hydrocarbon gases are generally rarded as evidence that the gas is petroleum gas — that is, that it is associated with oil — and if the structure of the beds is favorable their presence warrants drilling for oil at a structurally lower point, below the gas reservoir. Some analyses of gases are given below.

Analyses of Gas of Texas and Louisiana Fields (By Bureau of Mines. From U. S. Geol. Survey . 661, p.. 239, 1918.)

Carbon dioxide (CO,) . . .

Oxygen (O,)

Methane (CH4)

Nitrcen (N,)

Ethane (CEU)

Specific gravity determined

Specific gravity calculated

Heating value, in British

thermal units, at deg.

Trace

1,052

1,027

1,030

1. WeU No. 1 on Mackey lease, near Corsicana, Texas.

2. Well on Anglin lease of Robinson Oil & Gas Co., Mexia-<xroesbeck field, Texas. U. S. Geol. Survey BvU, 629, p. 102, 1916.

3. Well on L. B. Phillips lease of Southwestern Gas &. Electric Co., 10 miles west of Shreveport, Louisiana. Depth 1,000 feet.

4. Edwards well No. 1 of Southern Oil A Gas Co., sec. 23, T. 21 N,. R. 11 W., Caddo field, near Vivian, Jjouisiana. Depth 1,040 feet.

5. Swamp gas.

6. Beatty well No. 1, Petrolia field, Texas. U. S. Geol. Survey , 629, p. 41, 1916.

7. P. H. Youree well No. 3 of Gulf Refining Co. of Louisiana, sec. 33, T. 17 N., R. 14 W., nouth of Shreveport, Louisiana.

The presence of ethane, propane, and butane in gas is generally regarded as a favorable indication of petroleum, because these substances are found in a great many gases that are associated with oil. Nevertheless, their presence is not an infallible indication. One or more of the hydrocarbon gases heavier than methane were found in a sample of natural gas collected in 1917 in a glacial-lake deposit that is covered with lacustrine clay in southern Minnesota* On the other hand, a gas from the Edwards well (see table above),

Surface Indications Of Petroleum 35

in the Caddo field, Louisiana/ showed on analysis no hydrocarbon except methane, although the sand that yielded the gas contains oil in the same part of the field where the gas sample was taken.

Natural gas carries gasoline vapors much as air carries water vapor. Gas under great pressure is less Ukely to carry the gasoline vapors than gas under less pressure. When a boring penetrates a reservoir containing oil and gas under great pressure, the gas inmaediately expands and moves toward the hole, carrying the oil with it. As there is less resistance to the movement of the gas it moves faster and is exhausted first. When the pressure is high the dry gases absorbed in the oil are liberated, but as pressure decreases the wet gases liquified and dissolved in the oil are also released. A dry gas issuing under great pressure is more likely to be associated with oil than a dry gas issuing under low pressure.

Gas, like oil, issues both on land and sea. The seep on the Caspian Sea off Bibi-Eibat has been mentioned. Near Holy Island, also in the Caspian Sea, and off the coast of Peru, ag observed by Thompson, gas exuded beneath the sea.

Sulphurous gases and sulphur are associated with many petroleums and in smaller proportions with some natural inflammable gases. The sulphur gases include sulphur dioxide and hydrogen sulphide, both of which are easily detected by their odor. The gases accompanying the oil at Spindletop field, near Beaumont, Texas, were poisonous, possibly owing to the presence of sulphur compounds. These gases deposited sulphur on the Spindletop dome, and it was the occurrence of such deposits that led to the driUing of this field in a search for commercial deposits of sulphur.

Sulphur gases are found at the surface of many of the salt-dome deposits of Texas and Louisiana (p. 365). Because sulphur, hydrogen sulphide, and sulphur dioxide are widely dispersed in nature and occur in places far removed from petroleum deposits, they are generally of uncertain value as indications of oil, although in some small areas their presence is regarded as significant.

Matson, G. C, and Hopkins, O. B.: The Corsicana Oil and Gas Field, Texas. U. S. Geol. Survey Bull 661, p. 239, 1918

*Lewi8, J. O. : Methods for Increasing the Recovery from Oil Sands. U. S. Bur. Mines BuU., 148, p. 20, 1917.

Thompson, A. B. : Oil-field Development, p. 180, London, 1916.

*LucA8, A. F. : Principles and Problems of Oil Prospecting in the Gulf Coast Country (discussion). Am. Inst. Min. Eng. Trans. t vol. 59, p. 470, 1917.

36 Geology Of Petroleum

ParaflBn Dirt — The so-caUed paraffin dirt of the Gulf coast oil fields has been considered an indication of the presence of oil and gaa, and wells have been brought in On the basis of such evidence. Its association with oil and gas was first pointed out by Lee Hager.

The term ''paraffin dirt" has been appUed to peaty, clay soils with a peculiar texture, which has been described as "ciu*dy" or "rubbery." When moist, the material breaks much after the fashion of "green" cheese. It is rubbery under compression but does not resemble rubber in tenacity or cohesion. In the field it resembles "art giun." When dry, the material ranges from hard clods to a homy mass.

The moist material ranges in color from dark brown in the specimens rich in organic matter to grayish in specimens containing more inorganic matter. It is readily attacked by molds. It has a characteristic "swampy" or "mucky" odor when wet.

Brokaw analyzed a sample taken 1 mile north of Spanish Lake, St. Martin Parish, Louisiana, near a test well; another near the discovery well in the New Iberia oil field, Iberia Parish; one from Lake Dauterive, St. Martin Parish; and another near the discovery well in St. Martin Parish. He showed that the place of paraffin dirt among the evidences of oil and gas rests on the possibiUty that it may indicate gas-saturated soils in which gas inhibits oxidation, and obviously such soils are present in the vicinity of gas seeps. It does not necessarily follow that every gas seep is accompanied by paraffin dirt, nor is paraffin dirt an infalUble sign of a gas seep. Most "paraffin dirt" probably contains no paraffin.

/ Mud Volcanoes. — Gas issuing at the surface may carry with it particles of sand and clay which are deposited at the place of issue. Continuation of the process will build up a "pimple," mound, or cone. The process goes on generally in unconsolidated rocks, especially in the presence of water. If the wet clay or mud seals over the place of issue gas accumulates under pressure, and when the pressure is sufficient it blows off the seal with violence, imitating on a small scale the eruption of a volcano. In arid countries these mounds are built to considerable heights. The Bog-Boga mud volcano, in the principal oil district of the Baku region, Russia, is more than 100 feet above the plateau on which it stands and forms one of the high features of thelkndscape. (See p. 540.)

Brokaw, A. D. : An Interpretation of the So-called Paraffin Dirt of the Gulf Coast Oil Fields. Am. Inst. Min. Eng. BuU, 136, pp. 947-950, 1918.

Surface Indications Of Petroleum 37

In many Tertiary oil fields where the rocks are unconsolidated mud volcanoes are numerous. On the Taman and Kertch peninsulas, north of the Black Sea, there are many mud volcanoes, and great streams of mud flow down their sides. Several mud volcanoes are present on the shore of the Caspian Sea southwest of Baku, near the Bibi-Eibat oil field. They are reported also on Cheleken Island, and at Napthun, east of the Caspian Sea. They occur in Rumania (p. 532) and are numerous on the Arakan Islands, off the west coast of Burma, and on Cape Negrais, in southwestern Burma. They are found also in Borneo, Sumatra, Trinidad and Colombia. At many places in Rumania, Russia, Borneo, and Smnatra, they are on anticlines in Tertiary rocks that have yielded oil.

' Mud volcanoes, like seeps of oil and gas, have been known to rise from the sea* bottom. In 1897 during an earthquake a great mud volcano rose off the Klias peninsula, Borneo. The material ejected formed an island 750 feet long and 420 feet wide. Stigand states that this island was 50 to 60 feet high and eventually became joined to the mainland. Thompson records a volcano near the Arakan Islands, off the coast of Burma, which in 1907 threw out enough muddy material to make an island 1,200 feet long, 600 feet wide, and 20 feet high. The material had a temperature of 148° F. Off Erin, on the south coast of Trinidad, in 191 1 masses of hot mud with much gas were thrown out from the sea and formed an island of 23 acres, 14 feet high. This eruption, according to Thompson, occurred above a submarine anticline.

There are no typical mud volcanoes in the United States. Possibly some of the mounds of the Gulf coast region of Texas and Louisiana have been formed by processes nearly related to those which operate to form mud volcanoes. Features like small mud volcanoes appear at the surface in the Vale region of Oregon and Idaho. In the Caddo district of Louisiana small pimply elevations have been noted, but these, according to Matson, are probably the work of ants.

Somewhat similar in origin to mud volcanoes are the sand heaps that acciunullite at the casing heads of some gushers drilled in

Berghaus, H. : Atlas derGeologie, Gotha, 1892.

SnoAND, J A. : Discussion of paper by A. B Thompson in Inst. Min. and Met. Trans,, vol. 20, p. 262, London, 1911. Thompson, A. B. : Oil-field Development. P. 184, 1916

38 Geology Of Petroleum

loose sand. At some of the wells in California the engine houses and the lower parts of derricks have been thus completely buried. In some wells in the Sunset field, California, two-thirds of the total yield is sand. One well produced nearly 110,000 cubic feet of sand in two years. Some pumping wells in the North Midway field, California, produce sand at the rate of over 200,000 cubic feet a year.

Describing the sand masses produced by wells in Russia, Thompson says that the oil from fountains is commonly accompanied by an equal bulk of sand, large numbers of stones, and miUions of cubic feet of gas which becomes disengaged from the oil on its exit from the tube. A Bibi-Eibat well spouted 10,000 tons of oil and 10,000 tons of sand in a day and in a few weeks yielded 1,700,000 cubic feet (85,000 tons) of sand, which is enough to cover an acre to a depth of nearly 40 feet.

Mud Dikes. — Mud dikes that cut across the strata are found in some oil fields. They are supposed to have filled the vents through which gas issued to form gas seeps or mud volcanoes. Such dikes are found in Burma in the Yenangyat and Yenangyaung fields. What are undoubtedly mud dikes occur in the Huron shales of the gas field around Cleveland, Ohio. Dikes are formed also by clay squeezed into fissures.

/ Oil Shales. — As oil shales are commonly the original sources of petroleum and gas, their presence is usually regarded as a favorable indication. McCoy says that petroleum shales are always present in the petroliferous series that are exploited in the Oklahoma- Kansas field. From such a shale, under great compression, he extracted a little oil. Winchester suggests the Green River oil shales as sources of the great gilsonite veins and other solid hydrocarbons that are abundant in the Uinta Basin, Utah. Oil is extracted commercially from the oil shales of the West and Mid-

*KoBBE, W. H.: Problems Connected with the Recovery' of Petroleum from Unconsolidated Sands. Am. Inst. Min. Eng. Trans., vol. 1, 56, pp. 799-822,

Thompson, A. B. : The Oil Fields of Russia. Pp. 52-53, London, 1908.

'Pascoe, E. H. : The Oil Fields of Burma. India Geol. Survey Mem., vol. 40, part 1, pp. 72-73, 1912.

*McCoY, A. W. : Notes on Principles of Oil Accumulation. Jour. Geology, vol 27, pp. 252-262, 1919.

Winchester, D. E. : Oil Shale of the Uinta Basin, Northeastern Utah. U. S. Geol. Survey Bull. 691, pp. 27-55, 1919.

Surface Indications Of Petroleum 39

lothian districts, Scotland, and elaborate attempts have been made to extract oil profitably from the kerosene shales of New South Wales. Some oil shales approach coal in carbon content and yield 80 to 120 gallons of oil to the ton. The oil shales of the Albert series, at Albert, New Brunswick, which were once exploited for oil, are reported to carry 50 gallons to the ton. /Dumt Shales. — In CaUfomia the Monterey shale, which accord- Ang to Arnold has supplied the bulk of the material from which the oil of that region was derived, is burnt red at many places, some of them in the Santa Clara district. The alteration has taken place at depths far below the usual depths of oxidation. In Trinidad red shale is found at many places. This is presumably a clay burnt hard by the oxidation of the petroliferous material it contained. The burnt clay is termed porcelainite* Here, as in California, slow combustion has evidentljTpenetrated to depths beyond those to which air can easily penetrate. Eldridge and Arnold suggest that the changes in California are brought about by spontaneous combustion. At Burnt Hill, Barbados, a bituminous shale by slow combustion has been converted into a hard, bricklike rock. Thompson mentions places on the Yorkshire and Dorsetshire coasts of England where Lias and Kimmeridge bituminous clays, which exude oil, ignite and burn for considerable periods.

Salt-Water Seeps. — Salt water is associated with petroleum in practically every large oil-producing region in the world. (See p. 48.) The only places known to me where oil is associated with water that is fresh or nearly fresh, are in the Rocky Mountain region of the United States, where in several fields the water that floats the oil is evidently mingling with circulating ground water and has been thereby diluted. Salt seeps are found in many oil fields. Many i$alt licks, or places where animals congregate to lick the salt from the earth or rocks, are formed of drying brine. Where the brine is associated with oil the animals' feet become oil soaked, and it is said that oil seeps have been discovered by men observing

Steuart, D. R.: The Oil Shales of the Lothians, 2d ed., part 3. Scotland Geol. Survey Mem., 1912.

*Thomp80N, a. B. : Oil-field Development. P. 205, 1916.

'ELDRmoE, G H., and Arnold, Ralph: The Santa Clara Valley Oil District, Southern California. U. S. Geol. Survey Bull 309, p. 22, 1907.

*Wall, G. p., and Sawkins, J. G.: Report on the Geology of Trinidad. Part 1, p. 50, West Indian Survey, 1860.

Thompson, A. B : Oil-field Development. P. 195, 1916.

40 Geology Of Petroleum

oil on the feet of pigs that had returned to farmhouses from their range. Large quantities of bones are found in some such places. These are evidently the remains of animals that drank at springs which possibly were salty.

Brine and rock salt are among the most widely distributed materials in the earth and occur at many places far removed from oil fields. The presence of salt water may suggest the possibiUty of petroliferous strata, but it has no certain significance, as many oil pools have been found where no salt springs issue and many salt springs issue at places remote from oil fields.

Sulphur and Sulphur Compounds. — Sulphur or sulphur com- / pounds are found in the petroleimi of many fields and in the salt y water that is associated with the petroleum Probably some of the sulphur associated with petroleum has been derived from the plants and bodies of animals that suppUed the material from which the oil and gas have been derived. If, as is supposed by many, petroleimi bacteria convert organic material to oil and gas, sulphur bacteria, which, Uke the so-called petroleum bacteria, are anaerobic, probably work under similar conditions to convert sulphates to sulphur and its unoxidized compoimds. Sea water that is buried with the sediments that yield oil is probably the principal source of theulphur.

Sulphurous gases have been mentioned (p. 35). Some of them deposit native sulphur and on oxidation yield sulphuric acid. In the Spindletop oil field of the Gulf coast region, sulphur was found in the soil, and the discovery well was drilled as an exploration for sulphur. At Sour Lake, also in the Gulf coast field, acid waters were among the surface indications that led to drilling.

Sulphur and aci3 waters, Uke salt and salt water, are widely distributed in the earth. It is only in certain surroundings that they are of interest as indications that suggest of the possible presence of petroleiuu,

. Chapter Iii

Openings In Rocks' Sizes Of Openings

Openings may be classified with respect to their size and with respect to their origin. With respect to size, they may be placed in three groups — supercapillary, capillary, and subcapillary.'

Supercapillary openings are those in which water obeys the ordinary laws of hydrostatics. For water at ordinary temperatures, tubes with holes more than 0.508 miUimeter in diameter or sheet openings more than 0.254 millimeter wide are supercapillary.

Capillary openings are tubes with holes less than 0.508 and greater than 0.0002 millimeter in diameter, or sheet openings between 0.254 and 0.0001 millimeter wide. In these water does not obey the ordinary laws of hydrostatics but is affected by capillary attraction. Water will not circulate so freely in such openings because of the greater friction along the walls. Hot water may move through such openings more readily than cold, however, and imder pressure either hot or cold solutions may be forced through capillary openings.

Siibcapillary openings include tubes with holes less than 0.0002 millimeter in diameter and sheet openings less than 0.0001 miUimeter wide. In these the attraction of the molecules of the solid extends across the open space. Water may enter such openings, but it tends to remain as if fixed to the walls, prohibiting further entrance of solutions. Circulation of solutions at ordinary temperatiu*es through such openings is therefore very slow.

If two rocks have equal amounts of pore space — supercapillary in one and subcapillary in the other— the one with the larger openings will afford more favorable conditions for the movement of fluids. Muds, clays, shales, and rock powders, which contain

This chapter is an abridgment of a discussion of openings in rocks in an earlier volume by the writer, "The Principles of Economic Geology," New York, 1918.

'Daniel, Alfred: A Text-book of the Principles of Physics. P. 315, 1896.

Van Hise, C. R. : A Treatise on Metamorphism. U. S. Geol. Survey Mon. 47, p. 135, 1904.

42 Geology Of Petroleum

exceedingly minute openings, are the great natural barriers to

circulation, although, under sufficient pressure, fluids are forced

through them.

Origin Of Openings

With respect to their origin, openings in rocks are classified as follows:

Primary Openings:

Intergranular spaces. Bedding planes. Vesicular spaces. Openings in pumice. Miarolitic cavities. Submicroscopic spaces.

Secondary Openings:

Openings formed by solution.

Shrinkage cracks due to dehydration, cooling, loss of

fluids, etc. Openings due to force of crystallization. Openings due to the thrust of solutions. Openings due to the greater earth stresses.

Primary Openings

Intergranular Spaces m Sedimentary Rocks. — The pore spaces in sedimentary rocks constitute a percentage of the volume of the rock ranging from less than 1 up to 25 or even more. According to Buckley, the Dunnville sandstone of Wisconsin has a pore space of 28.28 per cent. Many sandstones have 20 per cent or more. As shown by Slichter, the size of the grains does not determine the amount of pore space: a fine-grained rock may be as porous as a coarse conglomerate. Fig. 8 shows a pile of balls arranged in the most compact manner possible. Fig. 9 shows the spaces between the balls of Fig. 8. It is obvious that if these balls were increased or decreased in size the changes would aflFect similarly the spaces between them. The amount of space depends principally upon the assortment of grains and the system of pack-

Buckley, E. R : Building and Ornamental Stones of Wisconsin. Wiscon> sin Geol. and Nat. Hist. Survey Bull. 4, pp. 225, 403, 1898.

Slichter, C. S.: Theoretical Investigation of the Motion of Groun' Waters. U. S. Geol. Survey Nineteenth Ann. Rept.f part 2, p, 305, 1899.

Openinos In Rocks

FiQ, D. — Cut showing pore space in a mass of spheres packed in the moat compact manner possible, {After Slichl.)

44 Geology Of Petroleum

ing. If small grains fill in the spaces between large grains, the porosity is obviously diminished. The fact that very fine material will not permit the free movement of fluids is not due to the absence of openings but to the small size of the openings. In rock with subcapillary openings fluids tend to remain fixed to the rock particles. The pore spaces of the more coarsely granular rocks, such as sandstone, are more likely to serve as reservoirs for fluids than those in fine-grained rocks, such as shales. Clay particles are small, and because many are flat they pack closely. Moreover, colloidal matter in clay and shale tends to decrease permeabihty. Under suiScient pressure, however, fluids will be driven through even clays and shales.

Some sedimentary rocks contain large numbers of fossil shells that are hollow, some beds being made up largely of such shells. The porosity of such a bed may be very great.

Bedding Planes. — Bedding planes are due to the assortment or sizing of material during transportation and deposition. On account of the assortment of grains there is also a different arrangement of the pore spaces in the different beds. Consequently, even in a nearly homogeneous rock the different beds commonly have different degrees of permeabiUty. Fluids moving along the beds may follow the most permeable layer, but fluids moving across them must traverse also the most impermeable layers. Fluids will therefore pass along beds more readily than across them.

Vesicular Spaces. — Magmas generally contain included fluids. When the magmas are erupted and flow out upon the surface, pressure is reUeved and the fluids expand and escape as gases. If they expand when the lavas are in a sticky or viscous condition and near the point of solidification the openings due to expansion are preserved. The openings due to expanded gases in lavas, unlike the pores in sandstone, are generally not connected and therefore do not offer continuous passages to fluids.

Openings in Pumice. — Pumices are lavas that contain very large amounts of pore space. The openings are formed in the same manner as vesicles but are generally smaller and much more numerous. Siliceous lavas, such as rhyolites and other acidic rocks, are more viscous than basic lavas, such as basalt or diabase. Rock

KiNo, F. H.: Principles and Conditions of the Movements of Ground Water. U. S. Geol. Survey Nineteenth Ann. Rept.f part 2, p. 135, 1899.

Openings In Rocks 45

froth is more generally formed with siliceous material, although both acidic and basic lavas are commonly vesicular. Open spaces in a pumice are not continuous, and the circulation in them is slow. Fragments of pumice placed in water may float for days before the spaces are filled and the water-logged fragments sink. Petroleum deposits in pumice are rare or unknown.

Miarolitic Cavities. — Some igneous rocks and some pegmatites contain small openings which are believed to be spaces formerly occupied by fluids of the rock magma that were unable to escape during the solidification of the rock. Such openings, called miarolitic, are present in rocks that solidified under pressure and are unlike vesicles, although both are due to imprisoned fluids. The walls of miaroUtic cavities are usually rough, because they are lined by crystals of the rock. Miarolitic cavities are not known to be ! seats of accimiulations of petroleum.

Submicroscopic Spaces. — The denser rocks, which appear solid, contain nevertheless small amounts of pore space. A granite, which under the microscope has no visible openings, will absorb a small amount of water in the cold. Shales contain nmnerous openings, but these do not permit the ready passage of fluids because they are largely subcapillary. Under pressure, however, fluids are forced into or through subcapillary openings.

Secondary Openings

Openings Fonned by Solution.— In soluble rocks like limestones and dolomites large openings may be formed by solution and by removal of rock matter. Solution usually proceeds by enlargmg smaller openings, such as joints, bedding planes, or fissures. These openings may become the principal drainage channels of the country, and the solution cavities along them may be developed on an enormous scale. As a rule solution is more active above tle water level, but large cavities have been found considerably below the present water level. Where an ancient drainage surface is buried by later strata solution cavities may be found at great depths.

Openings Due to Shrinkage. — Shrinkage may be caused by dolomitization, dehydration, cooling, and other processes. If a fairly pure limestone is changed to dolomite without addition of carbon dioxide a shrinkage of about 12 per cent takes place. The

46 Geology Of Petroleum

porosity of some dolomites is assmned to be due to shrinkage. Cracks due to shrinkage in drying are common. Cooling cracks are formed soon after the solidification of igneous rocks, before they have cooled to the temperatures of the surrounding rocks.

Openings Due to the Force of Crystallization. — The force which crystaUizing matter exerts on the containing walls has been assumed to be sufficient to push the walls apart. If this force so operates it would be supposed that a solution, having once gained entrance to a fissure, however narrow, could enlarge the fissure while it was being filled. This process does not produce open spaces but is assumed to widen those already formed. Becker and Day performed experiments to ascertain the strength of such a force and found it to be of the same order as the crushing strength of crystals. They say: "It is manifest that we here have to deal with a force of great geological importance. If quartz, during crystallization, exerts a pressure on the sides of a vein which is of the same order of magnitude which it ofiFers to .crushing, then this force is also of the same order of magnitude as the resistance of the wall rocks, and it thus becomes possible that veins have actually been widened to an important extent, perhaps as much as 100 per cent or even more, by pressure due to this cause."

Dunn 2 considers the force of crystallization as an agent that has operated in expanding the openings of quartz-filled reefs of Bendigo, Victoria. The hypothesis appears, however, to be of limited application, if not untenable for many deposits. Very commonly veins show numerous vugs, and it is improbable that crystals, where they could grow freely into open spaces, would thrust aside great masses of rock. Moreover, the crystals themselves are generally not distorted. They do not show that their own growth was afiFected by such enormous pressures as are demanded by this hypothesis.

Harris' has appealed to this force in an hypothesis which he proposed to account for the salt domes of the Gulf coast region, and many investigators working in that region have accepted his

Becker, G. F., and Day, A. L.: The Linear Force of Growing Crystals. Washington Acad. Sci. Proc, vol. 7, pp. 282-288, 1905.

DuNN, E. J.: Report on the Bendigo Gold Field, Victoria. P. 25, Dept. of Mines, 1896.

Harris, G. D. : Oil and Gas in Louisiana, With a Brief Summary of Their Occurrence in Adjacent States. U. S. Geol. Survey BuU. 429, p. 8, 1910,

Openings In Rocks 47

hypothesis. The puzzUng genesis of the salt domes, however, should be regarded as a problem that is only in process of solution (p. 372).

Openings Due to Greater Stresses. — The openings that are due to the greater stresses attending the deformation of the earth are the seats of the larger number of the world's metalliferous deposits. Such openings, however, are less significant in connection with the origin of the bitimiens. Many dikes of ozokerite, gilsonite, and other bitumens have formed by the drying out of petroleum in great fractures. Few metalliferous veins filling openings in rocks are longer or wider than the great gilsonite dikes of the Uinta Basin, Utah. In some regions that yield petroleum fissures and zones of fracturing have served as passages between the strata in which the petroleum and gas originated and the strata in which they accumulated. In a few regions the fissures in rocks serve as

the petroleum and gas reservoirs.

Chapter Iv

Association Of Petroleum And Salt Water

Salt water is associated with petroleum in practically all the large oil-producing regions in the world and in nearly all prolific oil pools in these regions (Fig. 10.) In the Appalachian oil fields salt water generally saturates the petroliferous strata below the Catskill formation and also some of the petroliferous strata above the Catskill. The Catskill itself is not saturated. This series is of terrestrial origin. According to Reeves,* in places the pore space in the Catskill sands is filled with air. Tjie sediments had evi-- dently dried out before they were submerged in the sea. This series, which embraces the Venango oil sand group, is very prolific

01 H- Wafer

Fig. 10. — Sketch showing a common relationship of oil, gas, salt water, water somewhat salty, and fresh water. The circulation of fresh ground water sweeps out the brine near the surface and dilutes it in depth.

in southwestern Pennsylvania. In the Venango group the oil is found in synclines. (See p. 212.)

In the Ohio portion of the Appalachian field the Pennsylvanian and Mississippian strata carry salt water. In the Clinton gas field the Big lime (Silurian), which lies a short distance above the "Clinton'' sand, is soaked with brine. Near Bremen, Fairfield County, a very light oil is found in the Clinton in a small pool that appears to be free from water. From this fact Bownocker concludes that the oil is in shallow basins rather than on the slopes of anticlines. It seems probable that the oil is perched in this basin and that gas rather than brine may be found in the Clinton below

'Reeves, Frank: Absence of Water in Sandstones of, the Appalachian Oil Fields. Econ. Geology, vol. 12, pp. 254-278, 1917.

'BowNOCKEB, J. A.: Petroleum in Ohio and Indiana. Geol. Soc. America BvU,t vol. 28, p. 672, 1917.

Association Of Petroleum 49

the pool. This occurrence of oil free from water, according to Bownocker, is unusual in Ohio.

In the Lima-Indiana field, where oil and gas are found in the Trenton limestone, salt water rises to nearly equal altitudes. In the Irvine field, eastern Kentucky, salt water is associated with the oil, some wells yielding considerable quantities. In the Wayne County and McCreary County fields, in southern Kentucky, oil is foimd in Paleozoic rocks. Where the oil Ues in synclines the rocks do not contain water. Salt water is present in the Spurrier region, Tennessee.

In Lambton Coimty, Ontario, the petroUferous strata carry salt water. The Dundee (Comiferous) formation in southern Michigan contains brine.

In Illinois petroleum is found chiefly in the lower part of the Pennsylvanian and upper part of the Mississippian rocks, in both of which it is associated with much salt water. As stated by Kay* in the bottom of the Illinois basin and well up on its sides the Pottsville rocks are saturated with salt water.

In the Oklahoma-Kansas field salt water is associated with the oil, and in the western part of the field the sands are saturated and the oil and water are under considerable pressure. In the Red River field of southern Oklahoma and northern Texas, and in the Ranger field of Texas the petroUferous rocks are saturated with brine.

In the fields of northern Louisiana and eastern Texas, where oil is obtained from the Upper Cretaceous beds, salt water is present in the producing members. The Woodbine sand yields oil and gas in Louisiana and at South Bosque, Texas. At both places it carries brine. At Corsicana, Texas, where the Woodbine is barren, it yields water that is only sUghtly saUne. The Blossom sand at Caddo, Louisiana, carries oil and salt water. The Nacatoch sand is saturated with brine in the Caddo field. The Taylor marl

Shaw, E. W. : The Irvine Oil Field, Estill County, Kentucky. U. S. Geol. Survey BuU. 661, p. 149, 1918.

*Pbmberton, J. R. : a R6sum of the Past Year's Development in Kentucky From a Geologic Standpoint. Am. Assoc. Pet. Geol. BttU., vol. 2, pp. 38-53,

'Smith, R. a.: The Occurrence of Oil and Gas in Michigan. Michigan Geol. and Biol. Survey Pub. 14, Geol. ser. 11, p. 27, 1914.

<Kat, F. H. : Oil Fields of Illinois. Geol. Soc. America BuU., vol. 28, p. 657,

50 Geology Of Petroleum

carries salt water at Thrall, Texas. Salt water and salt are associated with petroleum in the salt-dome field of Texas and Louisiana.

[ In the West, also, salt water is associated with petroleum in nearly every large field. It is present in all the producing fields of Wyoming except in the Grass Creek anticline of the Big Horn Basin and some neighboring anticlines, where the oil is floated on a water that is only sUghtly salty or feebly alkaline. In this region, as stated by Hewett and Lupton, there has probably been accession of surface water to the beds from the outcrops. In the Salt Creek field the oil is floated on brine. Recently, however, a well sunk near a fault, on the west border of this field, yielded comparatively fresh water. In the Pecos Valley, New Mexico, a heavy black oil is associated with water that rises copiously into artesian wells. The water carries a considerable concentration of salts in some wells but very little salt in others. In California the petroleiun is associated with brine.

In Mexico great quantities of salt water are encountered in the petroleumrbearing strata. The Dos Bocas well, after spouting oil heavily for 58 days, began to discharge hot salt water, yielding 1,500,000 barrels a day.

In the Boryslaw region, Galicia, oil occurs in the Miocene salt shale and SaUferous clays, and in Rumania in the Saliferous clays. In Rumania oil is associated with salt water and some with salt. In the Berca and Becieu fields salt efflorescences accompany oil seeps and mud volcanoes above the producing anticlines.

In the Baku field, Russia, all the deep waters are brines. At Holy Island salt water issues in the oil fields. In Egypt salt and salt water are closely associated with the petroliferous beds. In the Irrawady River field, Burma, the oil is floated on salt water. Noteworthy features of the water of Yenangyaung, as indicated by analyses reported by Pascoe, are the large amount of carbonates and the absence or low content of sulphates.

*Hewett, D. F., and Lupton, C. T.: Anticlines in the Southern Part of the Big Horn Basin, Wyoming. U. S. Geol. Survey BvU, 656, pp. 46, 166,

Fisher, C. A. : Geology and Underground Waters of the Roswell Artesian Basin, New Mexico. U. S. Geol. Survey Water-Supply Paper 158, 1906.

'Preiswerk, H.: Ueber den Geologischen Bau der Region der Schlammvulkane und Oelf elder von Berca und Becieu bei Buzen in Rumanien. Zeitschr, prakt. Geologic, 1912, pp. 86-95.

Association Of Petroleum 61

The waters of the oil fields of California were investigated by jRogers The water-being sands are generally encountered above, below, and, in many places, in the oil measures. The water in many of the sands is imder high pressure. Some of the groimd waters are as salty as ocean water, but others are fresh. This difference is believed to be the result of difference in freedom of circulation, which is controlled by the structure. Where the structure prevents circulation the ground water is salty, but where it does not and circulation is relatively free, surface water has entered the beds and replaced much of the strong chloride water originally present. Ground water near the surface and near the outcrops of the beds is comparatively fresh, but the content of chloride generally increases with depth. The deeper waters trapped in structural troughs, like the Midway syncline, closely resemble ocean water in most respects and are believed to be only slightly altered sea water. The surface waters and shallow ground waters and also the deeper ground waters outside the oil fields on the west side of San Joaquin Valley contain sulphate. In the oil fields, however, the content of sulphate decreases with depth, and ground waters near and in the oil measures are practically free from sulphate. This decrease in sulphate is attended by a corresponding increase in carbonate, and in districts in which chloride is not abundant the waters near the oil measures are nearly pure carbonate waters. Where chloride is the predominating acid radical, even in the shallower waters, carbonate is unimportant, and the chief change with depth is the disappearance of the sulphate. The amoimt of sulphide in the deeper waters is roughly proportional to the amount of sulphate in the waters directly above them, or nearer the surface. Calcium and magnesium predominate in many of the surface waters, but sodium and potassium greatly predominate in the deeper waters. Most of the waters associated with the oil are therefore variously proportioned mixtures of solutions of alkaline carbonates and chlorides, the proportion of carbonate depending chiefly on the extent to which meteoric water is able to enter at the outcrop.

When gases under high pressure are released they expand and the salt solution, carried as spray, becomes cooler and deposits salts by evaporation of water in their reservoir rocks and in casings

Rogers, G. S. : Chemical Relations of the Oil-field Waters in San Joaquin Valley, California. U. S. Geol Survey BuU. 653, p. 113, 1917.

52 Geology Of Petroleum

of wells. Mills and Wells state that waters associated with petroleum undergo deep-seated concentration, brought about by their evaporation into moving and expanding gas. During this concentration there is a definite order of change in the relative proportions of the dissolved constituents in the waters. Carbon dioxide and other gases are lost from solution. Calcimn, magnesium, and iron separate from solution as carbonates, and under favorable conditions sodium and minor proportions of calciiun and magnesium separate as chlorides — a process similar to the salting up of gas wells. A further separation of the dissolved constituents, more particularly of calcium, magnesium, iron, sodium, barium, strontium, carbonate, and silica, is brought about when waters from different beds and having different properties of reaction become mixed. The ratio of calcium to chlorine in the waters increases and the ratio of sodiimi to chlorine decreases with the concentration. Mills and Wells state that concentration by natural processes is brought about much as it is in wells, the gas pressure being gradually relieved by leakage of reservoirs where gas escapes in seeps at the surface, or into other strata containing gas at a lower pressure.

MiLls, R. V. A., and Wells, R. C: The Evaporation and Concentration of Waters Associated with Petroleum and Natural Gas. U. S. Geol. Survey BuU. 693, pp. 1-103, 1919.

Chapter V Reservoir Rocks And Covering Strata

Reservoir Rocks

General Character. — The reservoirs that contain oil and gas are the pore spaces in sands, sandstones, and sandy marls and the pores, solution cavities, and fissures in limestones, dolomites, and other sedimentary rocks. Oil is found in fissures in indurated shale and in fissures in igneous rock, but such occurrences are comparatively rare.

In Pennsylvania and West Virginia, altogether, there are thirtyseven reservoir strata, of which thirty-five are sands and sandstones, one a conglomerate, and one a limestone. The limestone is the Greenbrier, of Mississippian age.

Of the eight principal reservoir strata in Ohio seven are sands and one, the Trenton, is limestone.

In Indiana the Huron sandstone, the Jeflfersonville or "Corniferous'* limestone, and the Trenton limestone are the chief reservoir strata.

In Kentucky the principal reservoir stratum is the Jeflfersonville or "Corniferous*' limestone, although oil or gas or both are found also in many sands, and a small production is derived from limestones below the Devonian.

In the Spurrier and Riverton districts, Tennessee, the oil is derived from Ordovician limestone. In the Glenmary district it is obtained probably from an oolitic limestone.

In the Fayette gas field of Alabama* gas is derived from sands.

In Michigail oil is derived from the Dundee Umestoiie.

Fuller, M. L.: Appalachian Oil Field. Geol. Soc. America BvU.f vol. 28. p. 633, 1917.

'BowNocKER, J. A.: Petroleum in Ohio and Indiana. Geol. Soc. America BuU., vol. 28, pp. 667-676, 1917.

*Glenn, L. C: Recent Oil Development of Glenmary, Scott County, Tennessee: Resources of Tennessee. Vol. 7, p. 40, 1917.

*MuNN, M. J.: The Fayette Gas Field, Alabama. U. S. Geol. BuU. 471, p. 38, 1912.

Smith, R. a. : The Occurrence of Oil and Gas in Michigan. Michigan Geol. and Biol. Survey Pvb. 14, Geol. ser. 11, pp. 1-281, 1914.

M

/

64 Geology Of Petroleum

In Illinois in the principal producing district there are seven reservoir strata. All of them are sands or sandstones except the so-called McClosky sand, which is an oolitic limestone, and the Trenton dolomite.

In the Oklahoma-Kansas field the chief reservoir strata are sands. In Oklahoma, as shown by Aurin, there are more than 40 producing strata, of which all but two are sands. The Oologah, or Big lime and the Oswego or Fort Scott limestone, of the Pennsylvanian, at places form reservoirs. Gardner' states that 90 per cent of the Oklahoma production has been derived from a single gand, the BartlesvUle.

In the Arkansas gas field near Fort Smith/ and in the oil field south of Kansas City, Missouri,' the reservoir strata are sandstones.

In the Red River district of southern Oklahoma and northern Texas the reservoir rocks are sandstones. In the Ranger and neighboring districts the principal reservoir strata are sandstone. In the Ranger and Caddo fields one reservoir horizon is at a contact between limestone and shale. In the Balcones fault region of Texas and in the northern Louisiana fields* the chief reservoir strata are sands, although in some districts the Austin (Annona) chalk carries gas and a heavy oil, and at Thrall oil is foimd in a tuflf included in the Taylor marl.' In the Gulf coast region of Texaa and Louisiana oU and gas are found in porous fractured limestone and in sands.

In the principal oil fields of Wyoming oil and gas are found in sands. On the Shoshone anticline, however, oil is derived from

>Kat, F. H.: QQ Fields of Illinois. Geol. Soc. America Butt., vol. 28, p. 657,

'AuRiN, F.: Correlation of the Oil Sands of Oklahoma. Oklahoma Geol. Survey Circ. 7, pp. 1-16, chart, 1917.

*Gardner, J. A.: Mid-Continent Geology. Oil and Oas Jour. Suppl., May, p. 7. 1919,

MrrH, C. D. : Structure of the Fort Smith-Poteau Gas Field, Arkansas and Oklahoma. U. S. Geol. Survey Bull. 541, p. 23, 1914.

*WiL80N, M. E.: Oil and Gas Possibilities in the Belton Area, Missouri. Missouri Bur. Geology and Mines, 1918.

*Matson, G. C, and Hopkins, O. B.: The Corsicana Oil and Gas Field, Texas. U. S. Geol. Survey 661, p. 217, 1918.

niDDBN, J. A., and Bybbb, H. P.: The Thrall Oil Field. Univ. of Texas BuU. 66, p. 39, 1916.

Reservoir Rocks And Covering Strata 55

limestones. A small part of the oil produced at Salt Creek comes from fractures in shale.

In the Florence district, Colorado, oil is found in fissures in shales. In the fields of western Colorado and in Utah the oil and gas are in sandy strata.

In California fields' the reservoirs are sands and conglomerates.

In Middlesex counties the principal producing area of Lambton and the Ontario field, the oil and gas are in Devonian limestone. In Dover West, Kent County, some oil has been derived from the Trenton limestone, and near Niagara Falls gas is derived from the Clinton sand. In the foothill region of the Canadian Rockies gas is derived from sand.

In the Tampico region of Mexico the principal reservoir rock is limestone, although some oil is derived from sands above it. In Trinidad oil is derived from sands. In the coastal fields of Peru and Ecuador the oil is in sandstone. In the Comodoro Rivadavia field, Argentina, the reservoir is a coarse pebbly sandstone.

In Derbyshire, England, oil is found in limestone. In Alsace the oil is almost exclusively confined to sandstones that are included in marl beds. In the Boryslaw field, Galicia, according to Zuber,* the oil and gas are in flaggy sandstone in the SaUferous formation, and in conglomerates and sandstones in the Dobrotow formation, which is the richest in oil. In the Schodnica field the Eocene oil is in thick sandstone lenses and the Cretaceous oils are in sandstone lenses covered by shales or saline clays. In Rumanian fields the oil reservoirs are sands, sandstones, conglomerates, and probably

Wegemann, C. H.: The Salt Creek Oil Field, Wyoming. U. S. Geol. Survey BvU. 670, p. 36, 1917.

*Washburnb, C. W.: The Florence Oil Field, Colorado. U. S. Geol. Survey BvU, 381, p. 522, 1910.

'Arnold, Ralph, and Garpias, V. R.: Geology and Technology of the California Oil Fields. Am. Inst. Min. Eng. Bull 87, p. 405, 1914.

*WiLLLiMS, M. Y.: Oil Fields of Southwestern Ontario. Canada Dept. Mines Summary Rept, 1918, part E, pp. 30-42, 1919.

VoN Wervekb, L.: Vorkommen, Gewinnen und Entstehung des Erdols in Unter-Elsass. Zeitschr. prakt. Geologic, 1895, pp. 97-114.

ZuBBR, Rudolph: Die geologischen Verhaltnisse von Boryslav in Ostgalizien: Zeitschr. prakt. Geologic, 1904, pp. 41-48.

Preiswerk, H.: Ueber den Geologischen Bau der Region der Schlammvulcane und Oelfelden von Berca und Becieu in Rumanien. Zeitschr. prakt. Geologic, 1912, pp. 86-95.

56 Geology Of Petroleum

volcanic tuflfs. The reservoirs of the Baku field, Russia, are sands of unusual thickness. In the Grozny field* they are sands and sandstones. In the Maikop field the oil is found in loose sands. At Holy Island the oil is in sand.

The reservoir rocks of the Irrawady River fields in Burma are sands. In Japan the reservoirs are sandstones and volcanic tuffs.

It is noteworthy that the reservoir rocks in most oil fields are sands and sandstones. Among the exceptions are the Trenton limestone in Ohio, Indiana, and Ontario; the Devonian limestone in Ontario, Michigan, Indiana, and Kentucky; the Greenbrier limestone in Pennsylvania and West Virginia; the McClosky "sand'' in Illinois; the Oologah and Oswego limestones in Oklahoma; the Annona chalk of Louisiana and Texas; the limestone cap rock above the salt plugs in the Gulf coast region; the Embar limestone of Wyoming fields; the Tamasopa limestone of Mexican fields; the Mountain limestone in England; and the oil-bearing limestone of the Suez field, Egypt.

The sandstones differ greatly as to size of grain. In several fields oil or gas or both are found in conglomerates — for example, the Sharon conglomerate (Potts ville) of the Pennsylvania-West Virginia region. The Vaqueros formation of the Coalinga district and the McKittrick formation of the McKittrick district, California, yield oil in part from conglomerates. The reservoir of the Comodoro Rivadavia district, Argentina, is a coarse pebbly sand. In Rumania and Galicia some of the reservoirs are conglomerates. In the Galician fields the Dobrotow formation, which is very rich in oil, consists in part of conglomerates.

At many places oil is found in or near igneous rocks, but under conditions which indicate that it migrated from sedimentary strata near by. In three fields the productive reservoirs are igneous bodies, but in each of these fields associated sediments cover the igneous bodies and in each the igneous bodies are, in part at least, tuffs, breccias, or volcanic ash and sand.

Many occurrences of bitumen in porous igneous rocks are known.

Adiassevich, a.: Oil Fields of Russia. Am. Inst. Min. Eng. Trans. y vol. 48, p. 613, 1914.

Trench, R. H.: The Relationship of Structure and Petrology to the Occurrence of Petroleum. (Discussion of a paper by A. B. Thompson.) Am. Inst. Min. and Met. Trans., vol. 20, p. 247, 1911.

Pa8Coe, E. H. : The Oil Fields of Burma. India Geol. Survey Mem,, vol 40, part 1, pp. 65-100, 1912.

Reservoir Rocks And Covering Strata 57

One at Tar Point, Gaspe, Quebec, is noted by Logan. Clapp* mentions a vesicular basalt from Colorado in which the oil was shown by David T. Day to be sealed by calcite. Washbume' describes a porous basalt containing oil from the Johnson ranch, western Lane County, Oregon. These examples could be multiplied. It is noteworthy that none of them give evidence of petroleum originating in the igneous body and that none of them are of much commercial importance.

In Cuba, at many places, small amounts of petroleum have been obtained from fractured serpentine. DeGolyer* states that the oil probably originated in Jurassic or other sedimentary rocks, and then seeped into the serpentine from them.

The Thrall field, Williamson County, Texas, contains wells that were gushers. The petroleum reservoir is a vesicular, soft green basic igneous rock, in the Taylor marl. It lies at a depth of about 850 feet. The top of the igneous body is arched, so that it has a closure of at least 125 feet. (See p. 343.) The rock is brecciated, and Larsen, who examined specimens microscopically, states that some of them appear to be tufiF. The oil is probably derived from the Taylor marl. It is red in color and, like that derived from the Taylor marl in the Corsicana field, Texas, has a parafiin base. It is heavier, however, than the Corsicana oil.

In the Furbero district, Mexico,® igneous rocks including basalt, dolerite, basalt-gabbro, volcanic ash and sands, are covered by the Mendez shale and possibly by other strata which are indurated near the igneous mass. The sedimentary rocks above form an anticline. Petroleum has accumulated in openings in the igneous rocks and in the Mendez shale. DeGolyer states that the petroleum probably originated in the Tamasopa (Cretaceous) beds.

LoGAN, Sir William: Geology of Canada. Pp. 405-789, 1863.

*Clapp, F. G. : Revision of the Structural Classification of Petroleum and Natural Gas Fields. Geol. Soc. America Bull., vol. 28, p. 592, 1917.

'WaShburne, C. W.: Geology and Oil Prospects in Northeastern Oregon. U. S. Geol. Survey BuU. 590, p. 100, 1914.

*DbGoltbr, E. : The Geology of Cuban Petroleum Deposits. Assoc. Am. Pet. GeoL BuU. 2, pp. 133-167, 1917.

Uddbn, J. A., and Bybee, H. P. : The Thrall Oil Field. Texas Univ. BuU. 66, 1916.

DbGoltbr, E.: The Furbero Oil Field, Mexico. Am. Inst. Min. Eng. , 105, pp. 1899-1911, 1915.

58 Geology Of Petroleum

At Copper Mountain, in the Wind River Basin, Wyoming, pre- Cambrian granite forms the base of a dome. Paleozoic and later strata dip away from the granite on three sides of the dome. On the fourth side are Tertiary strata, nearly flat-lying. The granite is fractured and faulted, and in it, in shafts and tunnels, a heavy asphaltic oil and asphaltimi are encountered. The oil, according to Trumbull, was once accimiulated in the Embar (Carboniferous) beds, which elsewhere contain a heavy oil and which, with a thick series of Paleozoic and Cretaceous rocks, have been eroded from the dome. The oil may have migrated laterally as the strata were tilted, or even laterally and upward into the lower rocks, which had been raised to great altitudes near the center of the dome.

Petroleum is found in small amounts in metamorphosed rocks. The occurrence at Furbero, Mexico, has been mentioned. A little petroleimi is found also in a gneiss in the Santa Clara district, California. In the Controller Bay region, Alaska,' oil seeps from schists were noted, and in the Copper Mountain region, Wyoming/ bitumen is found in a homblendic rock and also in the granite. None of these accumulations are important sources.

Mineral Composition of Reservoir Rocks. — The sands that form the reservoirs of sandy strata range from fine sands to the pebbles of conglomerate. Few data are available regarding the mineral character of sands as shown by microscopic study. Most petroliferous sands consist mainly of quartz, but in some, feldspar, mica, and chlorite are present. Pyrite is often abimdant. Some petroliferous sands contain fragments of heavy residual minerals such as magnetite, garnet, ilmenite, amphibole, and monozite. Recently the method of identifying sands by microscopic study of the minerals present has been used by operating companies. Such study is expected to add much to the data available concerning the mineral character of sands.

Many minerals, on altering, yield clay. The fine particles of kaolin and the colloidal matter that is present in many clays tend to seal openings between the original mineral particles. Many of

Trumbull, L. W.: Petroleum in Granite. Wyoming State Geologist's Office BvU, 1, ScL ser., pp. 1-16, 1916.

'Eldridge, G. H. : The Santa Clara Valley Oil District, Southern California. U. S. Geol. Survey BvU, 309, p. 5, 1907.

'Mabtin, G. C: Geology and Mineral Resources of the Controller Bay Region, Alaska. U. S. Geol. Survey Bva. 335, p. 42, 1908.

Trumbull, L. W.: op. cit,, p. 9.

Reservoir Rocks And Covering Strata 59

the ferromagneslan minerals form clay readily on weathering. These are more abundant, in general, in basic rocks than in acidic rocks like granites. Sands derived from basic rocks are generally less porous than sands derived from acidic rocks. Woodruff states that certain sands of Cuba are derived largely from gabbro fragments and that they have altered partly to clay, which fills the pores and limits their capacity. It is noteworthy, however, that fragments of limburgite, a rather basic rock, are found in the Thrall field, Texas, 2 and that basic igneous rocks, in part tuflfs and volcanic sands, constitute part of the reservoir at Furbero, Mexico.'

The porous limestones that form reservoirs include dolomites and also limestones that are not high in magnesium. The Trenton limestone of the Lima-Indiana oil field is in the main a dolomite, and Orton maintained that its porosity and ability to hold oil are due to dolomitization. He showed by analyses that the dolomitized portion of the formation is productive and that where it is barren it is low in magnesia.* Phinney, who investigated the Indiana field after Orton's conclusions had been published, states that the cavities of the Trenton are due "to loss of substance and not to substitution." He believed that the formation is commonly hard and uniform in texture and compact between the irregular ramifying cavities and pores interspersed through it. The Greenbrier limestone, in which some of the oil of the Appalachian region is found, is at many places non-magnesian. The Devonian limestone, of the oil-bearing region of Ontario, is somewhat dolomitic, and the Devonian of eastern Kentucky is dolomitic in the Irvine field, where it constitutes the reservoir rock. The Tamasopa limestone of the Mexican fields is said to be, in, part at least, of low magnesia content.

Capacities of Reservoir Rocks. — The amount of petroleum and

WooDRXJFP, E. G.: Petroliferous Provinces. Am. Inst. Min. Eng. BvU, 150, p. 909, 1919.

Udden, J. A., and Btbbe, H. P.: The Thrall Oil Field. Texas Univ. BvU. 66, p. 39, 1916.

'DbGolteb, E.: The Furbero Oil Field, Mexico. Am. Inst. Min. Eng. BuU. 105, pp. 1899-1911, 1915.

Obton, E. : The Trenton Limestone as a Source of Petroleum and Natural Gas in Ohio and Indiana. U. S. Geol. Survey Eighth Ann, RepLy part 2, p. 583, 1889.

*Phinnet, a J.: Natural-gas Field of Indiana. U. S. Geol. Survey Eleventh Ann, Reptf part 1, p. 617, 1891.

60 Geology Of Petroleum

natural gas a reservoir will hold depends upon its size and its porosity. The porosity of a fractured rock varies greatly because of differences in size and irregular spacing of fractures. Porous sands, on the other hand, are comparatively regular, although many of them show considerable differences also. The most porous sands are those that are made of comparatively uniform grains and free from clay. Cementation by silica, lime carbonate, iron oxide, or other substance will decrease porosity. An experienced driller can generally estimate the porosity of a sand by its "feel." If it is loose and free from cement and clay particles, its porosity is likely to be high. Other tests include touching it with the tongue or blowing through it to ascertain porosity. Chemical tests will reveal any trace of oil (p. 28). The amount of lime carbonate is easily estimated by treatment with acid.

Outcrops of a loose-textured, porous sandstone will show rounded forms of sugary texture. A good example is the St. Peter isandstone found at Minneapolis and at many other places in the Mississippi. Valley. Under proper conditions this sand would afford a good reservoir for oil accumulation. Unfortunately, the conditions other than porosity are unfavorable. If a sand is cemented by silica its outcrop shows the customary jagged forms of .quart z- ite. Surfaces here and there may be worn smooth and polished by wind erosion.

The porosity of a sand does not depend upon size of grain; a fine sand may have pore space less than, equal to, or greater than a coarse one. Uniformity of grains, shape of grains, and arrangement or system of packing affect porosity. If spheres of imiform size are packed in tbe closest possible manner (see Figs. 8 and 9) the pore space between them is 25.95 percent by voliune.* If the spheres are of different sizes the pore space is less, because the small particles fill the spaces between the large ones. If the particles are of irregular or angular shape the porosity may be greater or less than that of a system of uniform spheres, if the material is highly angular, with no flat particles, the porosity is likely to be

greater. Fig. 11 shows porous sands.

'Slighter, C. S.: Theoretical Investigation of the Motion of Ground Water. U. S. Geol. Survey Nineteenth Ann. Rept, part 2, p. 310, 1899.

Kino, F. H.: Conditions and Movements of Underground Water. Ideniy pp. 209-215.

Lewis, J. O. : Methods for Increasing the Recovery From Oil Sand& U. S. Bur. Mines Bull. 148, pp. 16-20, 1917.

Reservoir Rocks And Covering Strata 61

Buckley states that the Dunville sandstone of Wisconsin has a pore space of 28.28 per cent, A specimen of the Wall Creek sand, which is the principal petroleum-bearing stratum in the Salt Creek field, Wyoming, collected by Wegemann in the Powder River field, just west of Salt Creek, under tests made by C. E. Van Orstrand, showed a porosity of 25.8 per cent.* Another specimen, somewhat

(A) Hoing und, Colnuir field, lUinois. (B) Producing sand of the (

(O Gnins of und (rom emidaiane shown In B. iiiagniGed

Fig, 11. — Photographs of oil sand. (From A. W. Latter, Econ. Geology.)

shaly, taken near the base of the formation, has a porosity of 20.4 per cent, and a thin layer of calcareous sandstone showed only 7.6

>Bi7CKLiET, E. R.: Building and Ornamental Stones of Wisconsin. Wisconsin Geol. and Nat. Hist. Survey BuU. 4, pp. 225, 403, 1898.

'Wboeuahn, C. H.: The Salt Creek Oil Field, Wyoming. U. S. GeoL Survey BuU. 670, p. 27.

62 Geology Of Petroleum

per cent. The average porosity of the Wall Creek sand as indicated from the three determinations is 17.9 per cent. The effective porosity, however, is less than that, for as noted by Wegemann, some of the intergranular spaces are sealed and cut off from other spaces by impervious material, so that oil can not enter them. The Shannon sand of Salt Creek has a porosity of 26.7 per cent.

Van Orstrand made tests of the porosity of the Nacatoch sand member of the Navarro formation, which carries the great gas deposits of the Mexia-Groesbeck field, Texas. The results ranged from 16.6 to 34.2 per cent; and the average was 25.5 per cent. The sand in this field is uniformly porous, according to Matson. The pressure, which was originally 276 pounds to the square inch, was probably enough to force the gas into minute pores. The oil and gas bearing sandstone of Petrolia, Texas, tested by Van Orstrand, showed a porosity ranging from 18.5 to 27 per cent.

Fragments of the third sand at Oil City, Pennsylvania, were tested by Carll,' who estimated them to be capable of absorbing 7 to 10 per cent of their bulk without pressure and probably 12.5 per cent under pressure. Gardner* estimated the porosity of the Bartlesville sand of Oklahoma to be 20 per cent. The porosity of some of the sands of Baku, Russia, according to Thompson, is 25 per cent or more.

Sandstones such as are used for building are not much less porous than some oil sandstones. Buckley found the average porosity of 32 Wisconsin sandstones to be 15.89 per cent and of six Missouri sandstones to be 17.74 per cent. The average of six building stones of Ohio, according to Bownocker,* is 16.63 per cent. Three

'Matson, G. C: Gas. Prospects South and Southeast of Dallas, Texas. U. S. Geol. Survey BuU, 629, p. 87, 1916.

*Shaw, E. W.: Ga9 in the Area North and West of Fort Worth, Texas. U. S. GeoL Survey BuU, 629, p. 36, 1916.

Carll, J. F. : The Geology of the Oil Regions of Warren, Venango, Clarion, and Billings Counties, Pennsylvania. Second Geol. Survey, vol. 3, p. 251, 1880.

Gardner, J. H. : Mid-Continent Geology. Oil and Gas Jour. Suppl., May, 1919, p. 7.

'Thompson, A. B.: The Oil Fields of Russia. P. 45, London, 1904. . Buckley, E. R. : Building and Ornamental Stones of Wisconsin. Wisconsin Geol. and Nat. Hist. Survey 4, Econ. ser. 2, p. 402, 1898.

'Buckley, E. R.: The Quarry Industry of Missouri. Missouri Geology and Mines, vol. 2, 2d ser., p. 317, 1904.

BowNocKER, J. A.: Building Stones of Ohio. Qhio Geol. Survey BvlL 18, 4th ser., p. 77, 1915,

Reservoir Rocks And Covering Strata 63

determinations of building stones of Washington, made by Shedd, showed an average porosity of 13.7 per cent.

The size of the grains of a sand does not appear to limit its porosity. Some of the productive sands of the Duke-Knowles pool in Texas have very fine grains. In many parts of the Sunset-Midway field, California, according to Pack, more than 80 per cent of the oil sands are smaller than 200 mesh. Of five samples of oil sands from Russian fields treated by Thompson,* nearly all of the material passed through a screen measuring 80 meshes to the inch and all of one sample passed through one measuring 200 meshes to the inch.

Clay particles between sand grains greatly reduce porosity. The small clay particles fill the pores and some clay Iq in a jelly-like colloidal state which is relatively impervious.

Sands grade into muds and sandstones into shales. Muds and shales are made up principally of very fine sand grains and clay. Very thin sands in thick series of shales are likely to be filled with clay and impervious to oil and water. Some of the sands of the Cretaceous shale and sand series that is productive in Wyoming are barren at places in northern Montana, where the thickness of the sands decreases. Sands that were laid down far out from shore lines are conmionly less porous than sands deposited near shore.

The estimation of production by utiUzing saturation as a factor has been w'orked out by Washbume.* He estimates that the porosity of sand ranges from 0 to 20 per cent and notes that field determinations of surface samples generally show lower porosity than those of buried sands, probably because near the surface calciiun carbonate is deposited in some of the openings. In one determination the deep sands showed one-fourth greater porosity than the same sand at the surface. Washbume estimates for two samples 60 and 75 per cent saturation, the volumetric remainder, 40 and 25 per cent, respectively, being assigned to gases and water. The amount of oU extracted is, according to Washbume, 60 to 80

Shedd, Solon: Building and Oraamental Stones of Washington. Washington Geol. Survey Ann. Rept., 1902, vol. 2, pp. 134-136, 1903.

*Pack, R. W.: The Sunset-Midway Oil Field, California. U. S. GeoL Survey Prof. Paper 116, p. 000, 1920.

Thompson, A. B. : Oil Field Development. P. 107, 1916.

Washbubne, C. W.: Estimation of Oil Reserves. Am, Inst. Min. En Trans., vol. 51, p. 645, 1915.

64 Geology Of Petroleum

per cent, the higgler figure for gas-rich oils, in sands pumped to a vacuum. Heavy asphaltic oils may yield ccmsiderably less.

The porosity of porous limestones can DOt be so readily estimated because the pores in limestoDe are more diverse in size and not so regularly spaced. Enlarged sections of the Trenton limestone showing the nature of the pores are illustrated in Fig. 12, after

Orton.' The porosity of some limestones is very great. The Trenton limestone and the Tamasopa limestone of the Tampico region are among the most productive oil-bearing strata known. The Spindletop, a prolific dome in Texas, derived its oil from a porous limestone.

Orton, Edward: The Trenton limestone as a Source of Petroleum and iDflammable Gas ia Ohio and Indiana. U. S. Geol. Survey Eighth Ann. Rept., part 2, pp. 475-662, 1889.

Reservoir Rocks And Covering Strata 65

Coverings Of Reservoirs

Kinds of Covering Strata. — Nearly all the strata that f onn petro-j liferous reservoirs are covered by argillaceous rocks. Paleozoid reservoirs are generally covered by shales; Mesozoic reservoirs by* shales, clays, or marls; Cenozoic reservoirs by clays or marls, or, where the strata have become indurated, by shales.

In the Appalachian field of the United States the covering strata are shales. In the fields of southwestern Ontario the strata that cover the petroleum-bearing Umestone are soft shales or "soap rock." In Ohio, Indiana, and Illinois the reservoir rocks generally are covered by shale. In the Colmar field, Illinois, the Hoing sand lies as patches on eroded shale and is covered by the Niagara limestone. In Kentucky and Tennessee the reservoirs are covered by shale, but in parts of these States the covering shales are thin and some of the reservoirs are not effectively sealed.

The covering strata in all the Kansas, Oklahoma and northern Texas fields are shales. In the Balcones fault region of Texas the reservoirs are covered by clays and marls. In the northern Louisiana fields the covering strata are clays. In the Gulf coast region of Texas and Louisiana the covering strata are clays, muds, and "gumbo."

In the Rocky Mountain fields the covering strata are shales, except in the Douglas field, Wyoming, where a little oil in the White River formation is found in sandstone below clays. In California fields the covering strata are shales and clays.

In the Tampico field, Mexico, the deposits in the Tamasopa limestone are covered by shales and clays. The petroliferous strata of Trinidad are covered by clays. In Peru the beds covering the oil strata are shales.

In Alsace the petroliferous sandstones, according to Von Weryeke, are covered by marls. In the Boryslaw field, GaUcia, the gas and oil-bearing sandstones of the Saliferous formation are covered by clay, shale, or marl. The sands and conglomerates of the Dobrotow (upper Oligocene) are covered by shales. In the Schodnica field the principal petroliferous members are thick sandstone lenses in clay. In the Rumanian fields the oil and gas are in sandstones and conglomerates covered by marls, clays, and shales. In the Baku fields, Russia, the oil is found in sands covered by clays and marls. In the Grozny field the sands and argillaceous cap rock are said to be more indurated. At Maikop, Russia, the

66 Geology Of Petroleum

reservoir is sand covered by shale. At Holy Island the reservoir- is a sand covered by clay. In the Burma fields the oil sands are covered by clay. In Java the oil sands are covered by clay and clayey marls. Id Japan the reservoirs, which consist of sandstone and tuff, are covered by shale.

Tbickness of Covering Strata. — The thickness of the covering /that is necessary to retain a petroleum deposit depends upon the [gas presaure that exists in the deposit. If the covering is a soft, pliable rock that will not fracture it is more effective than aa indurated, brittle or jointed p rock. Most of the lai pe-

troleum deposits developed

are relatively deep. They are held down by adequate covers of clays or shales that fracture with difficulty and close the fractures that are made in them. Some oil

fields, however, are devel- Fia. 13. — Section ot Oil Springs dome, j .. „ *i.

OnUirio, .ho-ins thin over cin hSdinj iii "P"! "'"T M" te turfacc. oil under high gaa presaure. The vertical The Drake well at TitUS- Bcele is greatly exaggerated. (Based on „ . „ „ „„

sketch by Williins.) Pennsylvania, encoun-

tered oil at a depth of only 69 feet and yielded oil at the rate of 25 barrels daily. Flowing wells have been brought in less than 100 feet below the surface. A wellknown shallow oil field is the one in Lambton and Middlesex 13). The producing stratum is the porous limestone, which is covered by about 400 feet of shales, limestone, and glacial drift. The shales are soft and very pliable and are referred to by the drillers as "soapstone." Flowing wells shooting high in the air and producing from 3,000 to 6,000 barrels a day each were obtained in this field. The efficiency of the thin covering is due probably to the nature of the rocks, the limestone layers giving strength to the whole and the soft shales sealing any opening that may have formed.

The Llewellyn well, 100 feet deep, which flowed oil at the rate of 1,000 to 2,000 barrels a day, was opened in the early sixties on the Eureka Springs anticline in West Virginia.

iFniiBR, M. L. : Appalachian Oil Field. Geol. Soc. America BuU., vol. 28, p. 623, 1917.

Reservoir Rocks And Covering Strata 67

-Ttpical Record of ▲ Well in Oil Springs Pool, Lambton County,

Ontario

Pleistocene: Feet

Surface 0- 60

Hamilton:

Upper limestone 60- 95

Upper "soapstone" 95-196

Middle limestone 196-223

Lower "soapstone" (salt water at 252 lt) 223-330

Onondaga:

Lower limestone (oil at 370 feet) 330-370

Shallow wells encounter oil in the Irvine district, Kentucky, where a porous limestone forms the reservoir. It is overlain by the black shale of the Chattanooga formation (Upper Devonian). This shale is higher in the geologic column than the Hmilton, which is the covering of the "Comiferous" limestone in Ontario. It is also more brittle, although where sufficiently thick it supplies a good cap rock. In this region wells only 80 or 90 feet deep simk in the shales and penetrating the limestone have obtained oil. Unlike the oil in the Ontario field, however, it was not under a high gas pressure.

Oil was found at comparatively shallow depths in the eastern

part of the Kansas-Oklahoma field, and also at Brownwood and

Strawn, Texas. In these regions where the oil-bearing strata are

shallow in general the pressures and the initial production are low.

In the great Mid-Continent gusher fields the coverings are in

general comparatively thick.

iShaw, E. W. : The Irvine Oil Field, Estill County, Kentucky. U. S. Geol. Survey BvU. 661, p. 145, 1918.

Chapter Vi

Some Properties Of Petroleum And Gas

Color. — Most crude oils are opaque except in very thin bodies. As a rule the color of thin layers in light passed through them is brown, although some oils are red and others yellow. The light oil obtained in the Calgary field, Alberta, is a pale lemon-yellow. A little white oil has been found in the Los Angeles field, California, and considerable quantities of pale straw-colored or "white" oil are recovered in the Surakhany field in the Baku region, Russia. White oils are supposed to result from the natural filtration of petrolemn through clay. Siunatra, according to Thompson,2 yields large quantities of volatile crude oil having the color of port wine.

By reflected light most crude oils have a greenish cast. Some, however, are yellow or black, or of the same color as when seen in transmitted light. The greenish cast of crude oil in reflected light frequently serves to distinguish it from some products of refining, which have a bluish fluorescence.

Odor. — Oils from different fields have different and fairly constant odors. The Pennsylvania oils smell like gasoline. CaUfornia oils, which have less odor, smell Uke coal tar. Some East Indian oils smell like oil of cedar. The Lima-Indiana oil has the disagreeable odors of sulphur compounds.

r The odors of oils have been used to assist in ascertaining their Origin. According to Clapp, in order to determine the characteristic odor of an oil, samples should be prepared in narrow bottles, stoppered, half filled with the oil. The oil is shaken vigorously so as to impart its odor to the air above the oil in the bottle, and if this gives the odor of hydrogen sulphide, a strong solution of caustic potash is added and the oil shaken until the odor gf sulphide

Thompson, A. B. : The Oil Fields of Russia. P. 94, London, 1904. 'Thompson, A. B.: Oil-field Development. P. 278, 1916. Clapp, F. G. : Petroleum and Natural Gas Resources of Canada. Vol. 1, p. 45, Canada Dept. Mines, 1914, Mines Branch. *Clapp, F. G., op, cU,f p. 47.

Some Properties Of Petroleum And Gas 69

of hydrogen disappears. Many Califomia oils, shaken with

caustic potash solution will give an odor of pyridine. In a second

sample the odor should be noted after similar treatment with

dilute sulphuric acid.

Density

The value of an oil in a general way is suggested by its weight, or specific gravity. As a rule Ught oils will yield larger proportions of the more valuable products, such as gasoline and kerosene. The heavier products are used in the main for fuel and for road dressing and are lower priced. If, however, the heavy oil contains considerable paraffin wax or materials that can be used for lubricants it may bring a higher price than light oil. The highestpriced oils are natural lubricating oils. These are comparatively: rare and are generally produced from shallow wells of small yield.

The specific gravity of an oil is its weight divided by that of the weight of the same volume of distilled water, taken as 1.000. By this standard oils range in weight from 0.780 or less to 1.000.'

In foreign coimtries the decimal specific-gravity scale is extensively used, but in the United States the Bamne scale is used almost exclusively. That is an arbitrary scale in which the weight of water is placed at 10°, the degrees increase as the weight of the liquid decreases. Thus, the lighter an oil the higher the number on the Bamne scale. The United States Bureau of Standards uses the following formula' for converting degrees Baumg into the decimal standard:

"Baumfe 130

Specific gravity of Uquid

The density is taken at 60° F.

On p. 70 is a table to be used for converting readings from one scale to the other and from pounds per gallon, barrel, or cubic foot to either scale. Gravity determinations are made by weighing a known volume of the oil either in a large container or on an assay balance in a small weighing bottle, or by placing the hydrometer in the oil and reading off the scale.

'Used for liquids lighter than water.

Geology Of Petroleum

EquivALBMTS OF BatimA Scalb and Specific Gbavitt

(After Payne and Stroud)

Specific Gravity

WiiGHT, Pounds

Deg. B.

Specific Gravity

WsiGBT, Pounds

"it

Per Gallon

Per Barrel

Per

Cubio

Foot

Per Gallon

Per Barrel

Per Cubic Foot

Some Properties Of Petroleum And Gas 71

Oil expands with increase in temperature. The coefficients of expansion of certain oils are shown in the following table:

Coefficients of Expansion of Some Oils

(After Hoefer)

Origin

West Virginia (Burning Spring) .

Pennsylvania (Oil Creek)

Canada

Burma

Russia (Baku)

Eastern Galicia

Western Galicia

Rumania (Ploiesti)

Italy (Parma, Neviano de Rossi),

Hanover (Oberg)

Alsace (Pechelbronn)

France (St. Gabian)

Zante

Density X 1,000 at

0 Dcg. C.

50 Deg. C.

Coefficient of Expansion X 100,000

Viscosity. — The viscosity of oil varies with its specific gravity. It is measured by ascertaining the time it takes a given amount of the oil to flow through a small opening in a viscosimeter. The instruments used are the Engler viscosimeter and the Saybolt viscosimeter. A unit often used is the Engler unit, obtained by dividing the time of the outflow of 200 cubic centimeters of the oil by the time of outflow of the same quantity of water at 20° C.

The determinations are of interest especially to pipe-line companies and all others who transport oil through pipes. Some oils are so thick that it is found practicable to heat them, to decrease their viscosity. The lubricating properties of oils are closely related to their viscosity.

Composition of Petroleum. — Petroleums are mixtures of compounds of carbon and hydrogen, generally with impurities consisting of sulphur compounds and nitrogen compounds. Hydrocarbons of the following series have been discovered in petroleum.

. CnH2n+2 CnH2n-e

CnH2n CnH2n_8

CnH2n-2 CnH2n— iQ

CnH2n-4 CnHgn-U

HoBFER, H.: Das Erdol. P. 54, 1906.

Geology Of Petroleum

The compounds most frequently appearing, according to Hoef er, belong to the first or parafSn series, the second or olefine series, and the fifth or aromatic (benzene) series. Of these the parafl&ns are much the most abundant in both natural gas and petroleum. The sulphur compounds in oil are mentioned on page 85, and the nitrogen compounds on page 82.

Paraffins from Petroleum*

Name

1. Gaseous:

Methane

Ethane.

Propane

Butane

2. Liquid:

Pentane

Hexane

Heptane

Octane

Nonane

Decane

Endecane

Dodecane

Tridecane

Tetradecane. . . .

Pentadecane.

Hexadecane

Heptadecane

Octodecane

Eicosane

Tricosane

Tetracosane

Pentacosane. . . .

He3cacosane

Octocosane

Nonocosane

Hentriacontane . Dotriacontane . . Tetratriacontane Pentatriacontane

Formiila

Ch4

C2He CsHg C4H10

91x20

CioH2t

C11H24

C18H28 C14H30

C16H32 C16H34 CitHss

C2oH4l C2jH48 C24H6O

C2eH64

C28H68 C29H60

CjlH64 C82H68 C84H70 C86H72

Boilins Point

Deg. C.

+ 1

°After HoEFER, H.: Op. ctt., pp. 58-59, with additions and changes.

Some Properties Of Petroleum And Gas 73

Oils are commonly classified as those with asphaltic base and y those with paraffin base. Asphaltic oils are those that yield on distillation a dark asphaltic residue. Paraffin oils on distillation yield light-colored paraffins that do not dissolve in the solvents that dissolve asphalts. Oils that contain paraffin are more easily refined than those that contain asphalt. In general asphaltic oils sell at a lower price than paraffin oils. Many oils, including most mid-continent and Rocky Mountain oils, contain both asphalt and paraffin.

In ordinary work oil is analyzed to ascertain what fractions may be obtained from it by distillation, rather than exactly what chemical compounds are present. The standard method of analysis, known as Engler's method, has been recommended by the Third International Petroleum Congress. This method is described by Day as follows. One hundred cubic centimeters of the crude oil, measured at 60° F., is delivered by a pipette into a distilling bulb holding about 125 cubic centimeters. The thermometer used is a nitrogen thermometer, reading to 550° C. The condenser tube, as prescribed by Engler, is 75 centimeters long and has an inclination of 75° from the horizontal. The point of initial boiling is taken when the first drop of oil falls from the condenser tube into the receiving flask. To avoid loss by evaporation the condenser tube is ground to fit into the graduated receiving flask, which is provided with a stopcock to draw oflf the oil at 150° C. and again at 300° C. The fraction between the initial boiling point and 150° C. (302° F.) constituting the gasoUne fraction, and the fraction between 150° and 300° C. (572° F.), constituting the kerosene fraction, are examined for specific gravity. The residuum is weighed as soon as cool; then its specific gravity is taken in the usual way and the volume calculated. The total thus obtained for the different fractions includes the sum of all determinations.

Dat, D. T. : The Production of Petroleum in 1913. U. S. Geol. Survey Mineral Resources, 1913, part 2, p. 1123, 1914.

Geology Of Petroleum

Analyses of

Petroleumso

Depth

of Well,

Feet

Phybicai. PRorxsras

Location

Gavrrr i

kT 60 DSQ.

Color

Odor

Specific

1 Petrolia. Ontario. Lambton County .

2,462

Darklvown Brown

Dark green Medium green

2 Vf nnm Oounty. PenMylvniA

3 Petroleum, Allen County, Kentucky

4 Parkersburg, Wood County, West

Virsinia

Like Pennsylvania ail Like Pennaylvania oil

5 Bremen pool, Fairfield County, Ohio

6 Northwestern Ohio— Trenton lime-

stone

Like Pennayivania oil

7 lAwrenee County. Dlinni ,

Dark green

Sulphur

Dark green Black

Dark green Brown

10 Glenn pool. Creek County, Oklahoma

11 Sour Lake pool, Hardin County,

Texas

Shilphur

12 Caddo pool, Marion County, Texas .

13 Coalinsa. Fresno County. CaliffniiAr

Like Pennsylvania oil

1 4 RivAr. Katii Cimmtv. ORlifnmui.

Black Dark brown

15 Zorritos. Peru

16 Baku Russia

'In the preparation of this table I have used data compiled by F. G. Clapp.

1. Rkowooo, Bovbrton: Treatise on Petroleum. Vol. 1, p. 228.

2. HsNBT, J. T. : History of Petroleum. B. Silliman. analyst.

3. 4, 5, 7, 11, 12. DAT, D. T.: U. S. Geol. Survey Mineral Resources. 1909, part 2. 6. Obton, Edward: U. S. Geol. Survey Eighth Ann. Rept., part 2, 1889.

8. Indiana Dept. Geology and Nat. Resources. W. A. Noyes, analyst.

Composition of Natural Gas. — Natural gas is associated with practically all petroleums. It rises to the higher points of reservoirs, and it is absorbed in the oil. Under the high pressures that exist in some fields considerable quantities are absorbed. Expansion of gas pushes the oil out of the interstices of the rocks and causes it to flow in wells. It is the gas pressure that causes wells to spout oil and salt water. Even in wells that are pumped, the gas generally forces the oil to the boring.

Some Properties Of Petroleum And Gas 75

Analyses of Petroleums*

Distillation bt Enoler's Mithod, bt Volume

Unsatoratbd Htdbo-

Carb0N8,

To 150 Deg. C.

150 Deg.-300 Deg.C.

Residuum

Total Cubic

Sulphur,

per Cent

P&r-

per

Cent

Asphalt,

per Cent

Water,

per

Cent

PBB CbnT

Cubic

Specific

Cubic

Specific

Cubic

Specific

Centi-

Crude

Des.-

Centi-

Grav-

Centi-

Grav-

Centi-

Grav-

meters

meters

ity

meters

ity

meters

ity

Deg.

"40. 00

a a

t

a

a

a a

a a a

a

Trace

t

Much

None

t

a

a a

r

a

Trace

a a a

t

a

a a

a

a a

a

a

,11.0

a

a

[

a

a

a

a a a a

a

J

a

a

a a a a

r

a a

m

a a

9, 10. Day, D. T.: U. S. Gcol. Survey Mineral Resources, 1909, part 2.

13. U. S. Geol. Survey, from card reporting production.

14. Am. Chem. Soc. J'ottr., vol. 25. Edmond O'Neil, Univ. California, analyst.

15. U. S. Geol. Survey Mineral Resources, 1909, part 2. American Analysis A Chemical Co., analyst.

16. 17. Rbowood, BovsBTON, op. dLt p. 225.

Although practically all oils are associated with inflammable gas, there are at many places issues of gas that are not associated with oil. The gas that forms in swamps and marshes has been mentioned (p. 33). In Minnesota, in sands below glacial clay, gas is foimd in quantities sufficient for lighting houses and under a pressure as great as 12 pounds to the square inch. Swamp gas is generally methane or ''marsh gas." Analyses of natural gases

Geology Of Petroleum

are shown in the accompanying tables. Properties of some of the hghter hydrocarbons are given in the table following the analyses.

Analyses op Natural Gas (Table Prepared by F. E. Carter)

Ontario.

VancoaTer, British Columbia.

Calgary, Alberta

United States:

Wyoming

Pennsylvania

New York

Cleveland, Ohio

California... Russia:

Ssuracbany..

Bibi-Eibat..

Baku

Galicia:

Tustanowioe.

Hungary: Seibenburgen.

Eiflsarmas.

Meth-

Eth-

ane

ane

(Ch4)

(Ca)

Carbon Dioxide (COi)

Oxygen (Oi)

Nitrogen

Other Gases

Trace

Hs, 2.2; CO, 0.5; HsS, 0.2; CsH4.

Authority

CtH4.0.9;

He, 0.2 CtHi, 0.2;

CO, 0.5 CsH4, 0.2;

CO, .3 C3H4, i.a

Heavy hydrocarbons, 8,7

Heavy hydrocarbons, 1.1; unstated, 6.0

Hi, 0.4

PhiUips Carter''

BurreU' Phillips' Phimpa' PhilUpB Cady Bad MeFarland' Da

Da

V.Herr*

Da

Da

Gniadewies and Haus-

Zeller

Ciako'

Exploit du Petrol, 1908, p. 302.

&Anu Chem. Jour., vol. 16, p. 416, 1894.

cFuel-testing Division, Mines Branch, Ottawa.

''Bur. Mines Tech. Paper 57.

Am. Chem. Jour. vol. 16, p. 416, 1894.

/Chem. 1887, p. 1524.

eJour. Am. Chem. See., vol. 29. p. 1523, 1907.

*Trudy, 1908.

Petroleum, vol. 6, p. 2245, 1911.

lPetroleum, 1906, p. 297.

iJour. Qasbeleuchtung, December, 1911.

See also Cadt, H. P., and McFarland, D. F.: Chemical Composition of Gas. Kansas Geol. Survey, vol. 9, pp. 228-302, 1908.

SOME PROPERTIES OF PETROLEUM AND GAS 77 Analtsbs of Natural Gas'

Vuitun Fraoo

King.

Km ChrioD

Forat

Bbthi Bureg Grand Qimiid

Qilifam* C3JUni.

CtlifwiiB CWifomia Cliforni. Ctlilcniii

Do. Do. Do.

OUibocu Oklnhonu

Keotudty

UMh

10,S

Oj

0,Os

2.S 3.S

0,0

0,0 D.0

o.o

S3

1,0

B.8

BO.g

M.2

as. 8

0S.3

Ioc

J]

,0

) )

(i4.2

g7.7

M.3

70,0

81,8 M,l

90,8 M.0

ro

0,0

8,0

a.i

28,2

16,9

31,7

Oo

1,044 1,240

I.Oi*

l!l84 1,004 1,273 1,M8

59

HA 2.8 per ont. 'HA 0.1 per oent

The recovery of gasoline from natural gas has become an important industry. By one method the gasoline is recovered by condensation of the gas; by another it is recovered by absorption of the gasoline when the gas is passed through a heavy oil. The gasoline is in great demand for mixing with low-grade naphtha. In 1911 176 plants in nine States produced 7,425,839 gallons of gasoline from natural gas. In 1917, only six years later, 886 plants in 12 States produced 217,884,104 gallons. Prior to 1916 the greater portion of the gasoline recovered from natural gas was obtained by methods involving compression and condensation. Since 1913, however, a steadily increasing proportion of the annual output of natural-gas gasoline has been recovered by the absorption process. The development of this process ttiat followed work

Geology Of Petroleum

done by G. M. Sabolt has extended the scope of the natural gas gasoline mdustry to include types of natural gas containing too little gasoline to warrant their successful treatment by compression methods. Some gasoline is recovered also from ''drips" in pipe lines that carry gas.

Properties of Seven Paraffin Hydrocarbons*

J

s

Methane

Ethane . Propane Butane . Pentane Hezane . Heptane

CHi

C4HtO

CiHii C7H16

84.1*'

36.4* 68.9* 98.4*

Id

'a

Grams

ld

B.tiL

1,861 5,012

M

a

British Candlepower

e5.0

A35.0 A53.9

m

k. e

oBur. Mines Bull. 88. 1915. .

6H0LLXMAN, A. F.: Organic Chemistry, edited by A. J. Walker. P. 41, 1910. Landolt and BdRNSTEiN: Physikalisch-chemische Tabellen, 3d ed. Pp. 416, 425, 1905. (J. Thomsen.) <'Gas at ordinary temperature.

Wbight, L. T.: Illuminating Power of Methane. Chem. Soc. Jour., vol. 47, p. 200, 1885. /Landolt and BOrnbtein: Physikalisch-chemische iTabellen, 3d ed. P. 185, 1905. (Dewar.) older. (OUewski.)

aFrajtkland. p.: Illuminating Power of Methane. Jour. Chem. Soc, vol. 47, 1885, p. 235. Landolt and BOrnbtein: op. cit.t o. 182. (Dewar.) Liquid at ordinary temperature.

*NoRTHROP, J. D. : Gasoline from Natural Gas. U. S. Geol. Survey Mineral Resources, 1917, part 2, p. 1115, 1919.

SOME PROPERTIES OF PETROLEUM AND GAS 79 Natubaitas Gasoline Mabkbted in the United States in 1917<>

state

OUahom... . WestVirpius.

California

Teaa.

Ohio

Lomnana

Iffinda

Ecntadcy. . . .

New York.. . . Cokndo

Number

Daily Capacity

17,392

4,642

2,122

902,385

QAaoLiini Pboducid

Quantity

115.123.424

32.668.647

28.817.604

13.826.250

6.920.405

5.439.560

4,979.754

4,934.009

3.818.209

1,174.980

181,262

217,884,104

Value

21.541.905

6,511.813

4.438,022

2.778.098

1,149.441

1.051.376

241,219

40.188.956

Prioe

per

Gallaa

Centa

MCtt.Ft.

84,719.941

167.771,351

45,351.247

49,487.056

12.677.216

30.062,141

2,233,511

2.685.895

24,915,946

9.315,339

429,287.797

U. 8. Geol. Survey Mineral Reaouroes, 1917, pwt 2, p. 1119, 1010.

Chapter Vii

Origin Of Petroleum And Natural Gas

The theories of the origin of petroleum and inflammable natural gas are separated into two groups, which may be called the inorganic and the organic.

Inorganic Theories

The theory that oil has been formed by inorganic processes has, in one form or another , been advocated by many chemists, l Their theses assume that waters or gases within the earth, acting on chemical compounds, generate the hydrocarbons which accumulate near the surface at favorable places. '] This theory is attractive because it suggests processes by which oil may be continuously forming, the supplies being replenished in part as they are used. Notwithstanding its attractiveness the theory of inorganic origin has not been accepted by many geologists because of the insuperable difficulties which it encounters in the field. Petroleum reservoirs are generally tightly sealed. The rocks that have been nearest the interior of the earth, the igneous rocks and crystalline schists, are nearly everywhere barren of oil. The geologic settings

of accumulations of petroleum offer the extreme antithesis to those

of deposits of metals other than iron, which in the main are found

near the centers of volcanism.

Berthelot showed that carbon dioxide at high temperatiu'es can react on free alkaline metals, which some have supposed the interior of the earth contains, and can yield acetylene, which would break down, forming higher hydrocarbons. He showed that n cetylene heated to high temperatures yields benzjge,

Mendelief suggested that iron carbides are present in the interior of the earth, and that underground water coming into contact with these compounds yields hydrocarbons. This theory was sup-

Berthblot, p. E. M. : Sur TOrigine des Carbures et des Combustibles Minraux. Compt. Rend., vol. 62, pp. 949-951, 1866.

*Mendeliep, D.: Enstehung und Vorkommen des Mineralols. Abstract by G. Wagner. Deutsch. Chem. Gesell. Ber., vol. 10, p. 229, 1877.

Origin Of Petroleum And Natural Oas 81

ported by Moissan and others, who produced hydrocarbons from iron carbides.

These and other inorganic theories have been advanced. Becker' attempted to show a relation between areas of magnetic deflection due to the presence of iron carbides and oil fields. The unprobability of his hypothesis has been pointed out by Tarr.' Coste has defended the inorganic theory, but most of his assumptions are unsubstantiated.

Nitrogen is foimd in many samples of natural gas and. petroleum. Nitrogen exists also in some mines that exploit deposits of the nletals that have been formed in comparatively late geologic time and that are associated generically with igneous rocks.* It has been suggested that nitrogen found in natural gas is of deepseated origin. This element, however, is widely distributed in nature and takes part in many biochemical processes. Mabery* found that samples of petroleum collected from widely separated regions all contained nitrogen compounds. It is present as pyridine and quinoline bases and their derivatives, and M'avery states that the association and composition of these substances are such that they could have originated only in plant and animal remains.

Inspection of Mabery's analyses with respect to the depth of the oil pools from which the samples came, shows the noteworthy fact that the deepest oils do not contain the most nitrogen, nor are those found nearest the surface much lower in nitrogen than those that are found in the deeper measures. The Paleozoic oils, which have probably been more deeply buried than those of later age, do not contain as much nitrogen as the Cretaceous and Tertiary oils. Of the oils Mabery analyzed, 13 are from Paleozoic and 8 from Tertiary and Cretaceous fields. The average nitrogen content of the

MoissAN, H.: Sur la Formation des Carbures d'Hydrogne Gazeux et Liquides par F Action de Teau sur les Carbures Mtalliques. Compt. Rend., vol. 122, pp. 1462-1467, 1896.

'Becker, G. F. : Relations Between Local Magnetic Disturbances and the Genesis of Petroleum. U. S. Geol. Survey Bull 401, pp. 1-24, 1909.

'Tarr, W. a. : The Lack of Association of the Irregularities of the Lines of Magnetic DecUnation and the Petroleum Fields. Econ. Geology, vol. 7, pp. 647-661, 1912.

<Co8TE, Eugene: The Volcanic Origin of Oil. Am. Inst. Min. Eng. Trana, vol. 35, pp. 288-297, 1905.

*Emmon8, W. H. : The Prmciples of Economic Geology. P. 285, 1918.

Mabery, C. F. : The Genesis of Petroleum as Revealed by Its Nitrogen Constituents. Am, Chem. Soc. Jour.f vol. 41, No, 10, pp. 1690-1697, 1919,

Geology Of Petroleum

Paleozoic oils is 0.061 per cent; that of the later oils, 0.104 per cent. These relations suggest that nitrogen compounds in petroleum break up with age, the nitrogen accumulating in gas associated with the petroleum.

NiTBOOEN Or QUiS*

PALEOZOIC on

No.

Locality

Rock strata

IHyth. Feet

Nitrogen, per Cent

Dudley, Ohio

Berea grit Rosenberg sand First Cow Run sand Berea grit Goose Run sand Berea grit

Berea grit Third sand Third sand

1,400 1,240

1,150

1,170

2,700 1,200 1,080

1,125

Emlenton, Pennsylvaiiia. Malta. Ohio

Cominff. Ohio

Marietta, Ohio

NewDort. Ohio

Cabin Creek, West ViririTiia

Titusville, Pennsylvania Emlenton, Pennsylvania. Bartlesville, Oklahoma. . Mahoning Valley, Ohio. . Mecca. Ohio

Pure quartz sand Sand

Morris, Kansas

Tertiart And Cretaceous Oils

Humble field, Texas, medium

Vinton, Louisiana

Sour Lake, Texas

Beaumont, Texas

Jennings, Louisiana

Caddo, Louisiana

Humble field, Texas, light. Baku, Russia

2,750 2,750 1,300 1,000 2,000 2,200 950-1,300

Mabubt, C. F., op cU.t p. 1693. I have taken the liberty to rearrange Mabery's table. — Average of two determinatiozu.

In some gases from the oil fields of the Mid-Continent region helium is present with methane and nitrogen. Its presence has

Cadt, H. p. and McFarlane, D. F. : Chemical Composition of Gas. Kansas Geol. Survey, vol. 9, pp. 228-302, 1908.

Origin Of Petroleum And Natural Gas 83

suggested to some investigators a deep-seated source of the gas and the oil associated with it. Little is known of the geologic occurrences of helium. The high molecular velocity of this Ught element renders plausible the hypothesis that it departs from the planet, and if so it was once more abundant in the earth than it is today.

Organic Theories

The theory that petroleum is generated by natural distillation under geothermal and dynamic influences from organic matter biuied in sediments was first suggested by Newberry and by Orton.2 Laboratory experiments that support this theory include those of Warren and Storer,* who prepared a calcium soap from menhaden oil which on distillation yielded a mixture of hydrocarbons like kerosene. Engler* distilled directly from menhaden oil the paraffins from pentane to nonane. obtained by distilling a mixture of fresh herring and pine wood a product that yielded on redistillation a residue like gilsonite, and by distilling herring alone he obtained one like elaterite.

Clarke® mentions calculations made by Szajnocha which show that the annual catch of herring on the northeast coast of Germany could yield in 2;560 years as much oil as Galicia has produced.

Engler obtained hydrocarbons by the distillation of vegetable oils. The theory that oil is derived principally from animal remains was supported by Engler* and by Hoefer®, both well known for their investigations of the origin of petroleum.

*Nbwberrt, J. S. : Devonian System. Ohio Geol. Survey, vol. 1, p. 160,

*Obton, Edward: The Origin and Accumulation of Petroleum and Natural -Gas. Ohio Geol. Survey, vol. 6, p. 74, 1888.

Warren, CM., and Storer, F. H. : Examination of a Hydrocarbon Naphtha Obtained from the Products of the Destructive Distillation of Lime Soap. Acad. Arts and Sci. Mem., 2d ser., vol. 9, p. 177, 1867. . Engler, C. : Zur Bildung des Erdols. Deutsch. Chem. Gesell. Ber., vol. 21, p. 1816, 1918.

Day, W. C.: The Laboratory Production of Asphalts from Animal and Vegetable Materials. Am. Chem. Jour., vol. 21, pp. 478-199, 1899.

Clarke, F. W. : The Data of Geochemistry, 3d ed. U. S. Geol. Survey Bull, 616, p. 730, 1916. (The original paper is not accessible to me.)

Engler, C. : Cong. Internat. du Ptrole, Paris, 1900, p. 20.

Engler, C: Zur Geschicte des Bildung des Erdols. Deutsch. Chem. Gesell. Ber., vol. 33, pp. 7-21, 1900.

HoEPER, H. : Das Erdol, p. 219, 1906.

84 Geology Of Petroleum

I These experiments show that compounds like those found in / petroleum may be derived from either animal or vegetable matter.

A theory that is accepted by many investigators today is that there are two stages in the formation of petroleum from organic material. In one biochemical processes predominate; in the other geochemical or d3mamochemical processes. Petroleum is believed to be derived from remains of plants, especially from those of low orders yielding waxy, fatty, gelatinous, or resinous substances, and from animal matter. The organic matter was deposited on the sea bottom in estuaries or not far from shore and in lakes. Through the action of anserobic bacteria it is changed, the cellulose probably being altered to other compounds and the waxes and fats set free. That plants of low orders, when distilled, can 3deld petroleum was demonstrated by Renault.' Prominence is given to such plants in the contributions by Dalton, White, and Winchester, mentioned elsewhere.

The probability that bacterial action plays a part in the reaction that 3rields petroleum was brought forward by Morrey.' That the source of the material is principally muds and shales is evident fl'om the association of shales and clays with oil-bearing strata.

/ The anserobic bacteria are active probably as soon as the mud containing organic material is deposited. Any oily matter which they set free could accumulate even on the sea bottom, for fine particles of clay surround globules of oil and sink them or hold them below water. Oil will not float long on water that is even slightly turbid. That is often shown on the Mississippi Biver near the Hennepin Avenue Bridge at Union Station, Minneapolis. Frequently oil is passed into the river from industrial operations. It covers the water for a few hundred feet along the river below the

Dalton, W. H.: On the Origin of Petroleum. Econ. Gleology, voL 4, pp. 603-631, 1009.

White, David: Some Relations in Origin Between Coal and Petrolemn. Washington Acad. Sci. Jonir, vol. 5, pp. 189-212, 1915. Late Theories Regarding the Origin of Oil. Geol. Soc. America BtiZZ., vol. 28, pp. 727-734,

'Rbnault, B. : Houille et Bacteriaces. Soc. Hist. Nat. Autmi. BiiU., voL 9, pp. 475-500, 1896; Compt. Rend., vol. 117, p. 593, 1893.

MoitREY, C. B., and Orton, Edward: Origin of Oil and Gas. Ohio Geol. Survey BmZZ. 1, p. 313, 1903.

Stuart, Murray: The Sedimentary Deposition of Oil. India Geol, Purvey Rec, vol. 40, pp. 320-333, 1910.

Origin Of Petroleum And Natural Gas 85

bridge and disappears downstream. After they have sunk the oil the clay particles can hold it down permanently, and it will accumulate at the bottom of the water.

There are few data showing the depth at which bacterial action takes place in buried sediments. Sulphur bacteria, which break up sulphates, probably live very near the sea bottom. Murray and Irvine show that sea water associated with the muds from the sea bottom contain less than half as much sulphate radicle as normal sea water. Shaw states that anserobic bacteria have been reported to be present at depths of 20 feet in bogs.

Some processes that either generate oil from the strata or accumulate it are active for a long time after the burial of the deposits. This conclusion is warranted by the fact that oil accmnulates under pressiu-e in reservoirs on monoclines that have been sealed long after burial, either by faults, by dikes, or by later impermeable strata that are deposited above them unconformably. The oil that had formed before the top of the reservoir became sealed would have been expelled if it had been under water pressure or gas pressiure at that time.

The anserobic bacteria that are supposed to effect the decomposition of cellulose in buried strata presumably work best in the presence of salt water. This is suggested by the fact that practically all productive petroleiun deposits are found in marine strata or in beds closely associated with marine strata. Coal deposits, on the other hand, are formed principally in fresh water, and the beds most closely associated with them are in the main nonmarine.

The sulphur bacillus {Bacillus sulphurens) and the petroleum bacillus (Micrococcus petrol) probably work together. Both are anserobic. Sea water that has been buried is depleted of sulphates (p. 51), and some of it carries hydrogen sulphide. Native sulphur is often found in marine strata. Sulphur bacteria take oxygen from (Sulphates and set sulphur free.

Sulphur, or its compounds, is found in the petroleum of most fields, although in some fields it is present in very small amounts. It is abimdant in the oils of the Lima-Indiana field, where it occurs as methyl sulphide (CH,)2S. Other sulphides of the paraflSn

Murray, J., and Irvine, R. : On the Chemical Changes in the Composition of Sea Water. Roy. Soc. Edin. Trans. vol. 37, pp. 481-57, 1896.

Shaw, E. W. : The R61e and Fate of Connate Water in Oil and Gas Sands (discussion). Am. Inst. Min. Eng. Trans., vol. 51, p. 606, 1915

86 Geology Of Petroleum

series have been identified. Sulphur compounds have been identified in Canadian oils, and free sulphur occurs in a Texas oil. The sulphur in oils is probably derived from bodies of plants and animals, many of which contain sulphur, as well as from sea water.

Because practically all important accumulations of oil are in or near marine strata it is supposed that organic matter buried in the sea may be more readily converted into oil than organic matter buried in fresh water. Nevertheless, oil shales such as are supn posed to have supplied some of the materials for the generation of petroleum are not all marine. The Green River oil shales contain remains of fresh-water shells. Winchester suggests as probable the hypothesis that these shales were the sources of the great bitumen dikes and asphaltic sandstones that are present in rocks below and above them in the Uinta Basin.

In California several of the formations associated with the oil measures are diatomaceous. One of these formations, the Monterey shale, is made up almost entirely of diatom tests. It is more than 2,000 feet thick and is present in nearly every important field. The oil has accumulated in sandstones associated with the shale. As shown by Arnold' and his associates, the sandy members are generally barren except where diatomaceous shales are present.

Diatoms are free-moving vegetable organisms. They dwell in the sea and also in fresh waters. The larger number of species are marine. These hve near the sea bottom and on free-floating plants, in the main of the plankton. Diatoms have siliceous tests made of two valves that fit together as a pill-box fits into its cover. They contain protoplasm much like that found in other algal cells, with chlorophyl, colored brown by diatomin. Their abundance, the composition stated, and their constant association with

Mabery, C. F., and Smith, A. W. : Sulphur Compounds in Ohio Petroleum. Am. Chem. Jour,, vol. 13, pp. 233-243, 1891.

Winchester, D. E.: Oil Shale of the Uinta Basin, Northeastern Utah. U. S. Geol. Survey Bull. 691, pp. 26-50, 1919. Schuchert states that some of the shale deposits may be of saline lakes. Amer. Inst. Min. Eng. Bull. 155, p. 3060, 1919.

Prop. Chas. Schuchert suggests that the lake in which the Green River was deposited may have been salt at one time. Written communication.

'Arnold, Ralph, and Anderson, Robert: Geology and Oil Deposits of the Coalinga District, California. U. S. Geol. Survey Bull. 398, 1910.

Arnold, Ralph, and Johnson, H. R. : Preliminary port on the McKittrick Oil Region. U. S. Geol. Survey Bull. 406, 1910.

Origin Of Petroleum And Natural Gas 87

oil-bearing strata in California have led Arnold to regard the dia toms as the principal sources of California oil and gas.

It has been suggested that "kerogen," the oil-yielding substance of oil shale is the product resulting from bacterial action on organic matter. This substance is assumed by some to represent a common intermediate product, which may later, by dynamic metamorphism, be transformed to oU and gas.

Practically every body of oil-bearing strata in the world includes a considerable thickness of shales or clays, or of marls and clays. These rocks not only furnish the impermeable covers necessary to prevent the escape of oil or gas, but in general they supply the organic matter from which the oil and gas are derived. As a rule the oil and gas are found in sands or sandstones associated with shales or clays, or in fractured limestones or dolomites. In a great many districts the producing strata consist of great thicknesses of shales or clays, containing several relatively thin beds of sand. Such a body of strata is commonly formed near shore, under delta conditions, or offshore in water only moderately deep. Deep-sea conditions are presumably less favorable for the deposition of such beds. Twenhofel states that black hydrocarbonaceous shale may form in water so shallow that it is but a step to land conditions. In Esthonia, on the Baltic, there are a number of localities along the shores in which deposits of black shale are now forming.

It is characteristic of a great many petroliferous regions that the strata change within short distances both laterally and vertically. Such changes are noteworthy in the oil fields of Burma, in the Apsheron region of the Caucasus, Russia, in the Appalachian oil fields, in Oklahoma, in California, and elsewhere. In some of the Burma fields one well section may dififer greatly from that of a well a few rods away. Such abrupt changes in sediments are characteristic of near-shore conditions. In other fields, like those of Indiana, the strata are persistent, and sections of wells started at the same geologic horizon will resemble each other closely. All these data indicate that oil-bearing sediments form most abundantly in shallow water and to a less extent in deep water though not at abyssal depths.

Steuabt, D. R. : The Chemistry of Oil Shale; The Oil Shales of the Lothians. 2d ed., part 3, p. 164, Scotland Geol. Survey Mem.y 1912.

Twenhofel, W. H: Notes on Black Shale in the Making. Am. Jour. Sci., 4th ser., vol. 40, pp. 272-280, 1915.

88 Geology Of Petroleum

While practically all of the petroliferous deposits of the world are associated with marine strata, it is possible that some have formed in saline lakes. Schuchert states that "kerogen'' may be formed in saline lakes, probably in those only that are not over 4 per cent salt.

Assocution Of Petroliferous Strata And Coal

It has been suggested that oil is derived from the materials that form coal. "Coal oil" and kerosene distilled from petrolemn are nearly related with respect to their physical properties. Pictet and Bouvier distilled from a coal from Montrambert, Loire, a tar in which they found C10H20 and C11H22, hydrocarbons identical with some separated from petroleums.

Coal has been formed in the main from vegetable matter deposited in fresh water. If vegetable matter deposited in fresh water can yield oil, a close association of coal deposits and of oil deposits would be expected. Methane gas is commonly associated with coals, and it is reasonable to suppose that heavier hydrocarbons also might be derived from coal-forming materials. They are formed when coke is made from coal. If there is a close generic relation between the formation of coals and the formation of oils, one should expect frequently to find oil-soaked coals and coal measures impregnated with oil, and also coal or lignite in the oil measures. The great coal-producing strata of the earth generally are not the oil-producing strata. Many of the oil-producing strata are nevertheless lignitic or closely associated with highly lignitic beds — more generally in Europe and Asia than in North America.

The oil-bearing series of Alsace, near Schwabweiler, passes into thin upper Oligocene sandstones, which alternate with coal seams 20 inches thick or less.' Carbonized plant remains are found in petroliferous saliferous sandstones in the Oligocene of the Bory-

ScHUCHBBT, Charles: Petroliferous Provinces. Discussion of a paper by E. G. Woodruff. Am. Inst. Min. Eng. Bull, 155, pp. 3059-3060, 1919.

Cunningham-Craig, E. H. : Origin of Oil and Shale. Royal Soc. Edinburgh Proc, vol. 36, pp. 44-86, 1916.

Pictet, A. and Boxtvier, M.: Ueber die Distillation der Steinkohle Unter Vermindertem Druck. DeiUsch, Chem. GeaelL Ber., 1913, pp. 33-42.

*VoN Wbrveke, L.: Die Entstehung der Unterelsaessischen Erdoelager erlautert an der Schichtenfolge im Oligocaen. Phil. Gesdl. Elsass-Loringen, Mitt., Band 4, Heft 5, pp. 697-721, 1913.

Origin Of Petroleum And Natural Gas 89

slaw field of Galicia, and also in the upper Inoceramus (Cretaceous) petroliferous beds of the Schodnica field. In Rumania, beds of lignite are found in the Pontian (Pliocene) in which petroleum also is present, possibly, however, as a result of infiltration from lower beds. The Burdigalian (Miocene) petroliferous sandstones of Rumania carry also beds of lignite. Coal fragments occur in the Pegu (Miocene) beds, which 3deld oil in the principal fields of Burma. Some of the coal beds of Sumatra are petroliferous.

At Roma, Queensland, Australia, gas occiu*s in Jura-Trias rocks consisting of sandstones, shales, and thin coal seams.' Plant remains are found in the petroliferous rocks of Trinidad.*

In North America oil, coal, and Ugnite are geologically not so closely spaced, although many of the great oil fields are not far from the great fields of coal and lignite. The coal fields of the Appalachian region are mainly within the area bearing oil, but the prmcipal oil-producing beds are below the coal-producing beds and separated from them by hundreds of feet of shales. The Ordovician and Devonian oils of Ohio, Indiana, Kentucky, Michigan, and Ontario are not closely associated with coals. The coal basin of Michigan lies above the Devonian strata. The coal measures of the Michigan coal basin possibly joined those of the Appalachian coal basin before the country was denuded by erosion. This, however, is uncertain. The Ohio-Indiana oil region was once probably overlain by coal.

In Illinois much oil is found in the coal series, but generally at geologic horizons below those of the coal. In the northeastern Oklahoma oil fields coal beds are found in the Pennsylvanian oil measiu-es associated with the oil sands. In the Pawhuska quadrangle, as noted by Heald,** the upper Pennsylvanian rocks contain layers with marine fossils but are accompanied by some thin lenticular beds of coal and beds of clean, fine-grained swamp clays with plant remains that indicate swamp or land condi-

ZuBER, Rudolf: Die Geologischen Verhaltnisse von Boryslaw in Ostgalizien. Zeiiachr. Prakt, Geologies 1904, pp. 41-48.

Pascoe, E. H. : The Oil Fields of Burma. India Geol. Survey Mem., vol. 40, p. 234, 1912.

Cameron, W. E. : Report on the Significance of a Flow of Gas in the Roma No. 2 Bore. Queensland Geol. Survey Pw6., 247, 1915.

*Cxjnningham-Craig, E. H. : Oil Finding, p. 13, London, 1914.

*Heald, K. C. : Geologic Structure of the Northwestern Part of the Pawhuska Quadrangle, Oklahoma. U. S..Geol. Survey BvU, 691, p. 61, 1919.

90 Geology Of Petroleum

tions. Ripple marks, worm trails, mud cracks, and footprints of quadrupeds in some of the sandstones show that the materials forming the beds were laid down on tidal flats, flood plans, or other low places where they were not submerged at all times or where the water was very shallow. Some of the oil sands of northern Texas are in coal-bearing formations. In northern Louisiana oil sands are associated with lignitiferous strata. In Wyoming the principal oil measures are older than the Laramie coal-bearing formation and younger than the Dakota, which in places carrier plant remains. In California there are no coal measures comparable to the oil measures. It is improbable that hgnite has contributed any considerable portion of the materials from which the California oils were derived.

In brief, the organic materials that have formed coals and lignites may have contributed fractions that have accumulated as deposits of petroleum and gas. It is improbable, however, that the principal coal deposits have formed from the materials that have contributed the principal petroleum deposits. This is shown at many places by the presence of barren sands between the oil sands and coal beds. There are probably in all fields, moreover, other sources of organic matter adequate to have supplied petrolemn.

Accumulation Of Petroleum In Beds Formed Arid

Conditions

Many petroliferous strata are closely associated with red beds, salt, and gypsmn — strata that are assumed to have formed imder arid conditions. This association is noteworthy, for arid conditions generally are not favorable to the accumulation of organic remains. Salt and gypsum in the main are formed in arms of the sea or precipitated in closed basins, such as do not exist in moist climates. Most marine organisms, moreover, will perish in salt solutions that are highly concentrated.

Not all red beds are associated with salt and gypsum. Red beds alone are not proof that the conditions were arid when they were formed. Many of the deserts of today are not conspicuously red. On the other hand, red beds are now being deposited as sediments at some places in moist regions.

The red shales that are closely associated with many oil-bearing

*ToMLiN80N, C. W. : The Origin of Red Beds. Jour. Geology y vol. 24, pp. 238-253, 1916.

Origin Of Petroleum And Natural Gas 91

series may have become red in part after the shales were deposited. Red oxide of iron may be formed from hydrated iron oxide by the dehydrating action of salt solutions, just as anhydrite is formed from gypsum. This action may be brought about in a saturated solution of sodium chloride at a temperature not above C. Concentrated salt solutions are common in oil fields.

The association of oil deposits in many regions with beds formed under arid conditions is probably due in part to the porosity of sands formed under such conditions. In arid cUmates weathering is largely mechanical rather than chemical. The sands are Ukely to be clean and free from clay particles. Moreover, the windblown sands are commonly porous, because the wind sorts the quartz grains and clay particles. A desert sand, with round grains, free from clay, submerged and covered by marine organic clays, marls, or muds would afford an excellent reservoir for the accumulation of oil.

In the Appalachian region red sediments are closely associated with many of the oil and gas bearing beds. The Catskill series contains a considerable amount of red shale. Red shales of the Mauch Chunk inclose petroUferous beds. In places the "Clinton" sand of Ohio is red. In Illinois red shales are found in the Chester (Mississippian), which is oil bearing. In the Mid-Continent oil field red shales are associated with some of the productive sands. In the Appalachian region salt and gypsum are found in the Salina, which, however, is not intimately associated with the strata that yield the petroleum.

In some fields in Europe the petroliferous beds are associated closely with land sediments formed under arid conditions. In Alsace the petroliferous series consists in part of red marl, anhydrite, gypsum, and pyrite lenses. In some parts of the district coal seams are present. As stated by Von Werveke, the series is part marine and part non-marine. The conditions when it was laid down changed from marine to non-marme, terrestrial, and arid. Although the oil-bearing beds are associated with the arid land

sediments, where anhydrite is present there is no oil in the sands.

DAUBBisE, A. : Etudes et Experiences S3mthetiques sur le Metamorphisme. Annalea dea Mines, 5th ser., voL 16, p. 411, 1859; Smithsonian Inst. Anniud RepL, 1861, p. 270.

MiLLS, R. V. A., and Wells, R. C. : The Evaporation and Concentration of Waters Associated with Petroleum and Natural Gas. U. S. Geol. Survey BvU. 693, p. 24, 1919.

92 Geology Of Petroleum

In Galicia the Sarmatian strata (Miocene) consist of limestone, sandstone, sands, clays, and shales, with gypsiferous and saliferous clays in the lower part of the section. The Sarmatian Salifere is the oil-bearing series in the Boryslaw-Tustanowice field. In Rmnania gypsum is found in the Tortonian and Helvetian of the Miocene. Both of these formations carry petroleum. The Sarmatian also carries petroleum in Rumania and is one of the petroferous series of the Baku fields, Russia, where it is gypsiferous.

In Egypt, Miocene strata yield oil along the west coast of the Gulf of Suez. As stated by Hmne, the oil-bearing strata are associated with great thicknesses of salt and gypsum beds.

In the Yenangyaung and Yenangyat-Singu fields, Burma, the oil-bearing series is the Pegu formation, of Miocene age, which is associated with red beds.

These associations are significant, yet practically all the oil-bearing series that contain beds formed under arid conditions include also, associated with red beds, or with red beds, salt, and gypsum, bodies of marine strata containing organic matter or remains of organic bodies, adequate to supply material for the formation of petroleum. Strata formed imder arid conditions doubtless supply the favorable reservoirs rather than the sources of organic matter that yields petroleimi.

Temperatures Of Oil Fields

Temperatures increase with depths in the earth, m general at the rate of about V F. for 60 or 70 feet. Many observations have been made in mines and wells, and the results differ widely owing to differences in local conditions, such as ventilation in mines, the structure of the rocks, and the nearness to watercourses of points where observations have been taken. Temperatures are higher in some oil fields than elsewhere at similar depths. Koenigsberger and Muehlberg have suggested that temperature gradients may be used in prospecting for oil. The differences in the gradients of oil fields are so great, however, that the value of their conclusions is somewhat problematic. Nevertheless, so far as is indicated by

Koenigsberger, Joh. : Normale und anormale Werte der Geothermiflchen Tiefenstufe. Centralbl. Mineralogie Jahrhuch 1906, pp. 673-679.

Koenigsberger, Joh. and MtHLBERG, Max: On the Measurements of the Increase of Temperature in Bore Holes. Inst. Min. Eng. (England) Trafu., vol. 39, pp. 617-644, 1910; Ueber Messungen der Geothermischen Tiefenstufe. Neuea Jahrb., Beilage Band 31, pp. 107-157, 1911.

Origin Of Petroleum And Natural Gas 93

data now available, the temperatures in oil fields are generally above normal. Rogers has recently investigated this problem and has found a high gradient in the Sunset-Midway district, California.

Many factors aflfect the accuracy of observations of temperatures in borings and of fluids that are encoimtered in them. Expanding gases cool the fluids, and temperatures change somewhat as the fluids rise." These factors are discussed by Rogers. So far as is indicated by data now available, temperatures generally increase more rapidly in Cretaceous and Tertiary oil fields than they do in older ones. That is not true everywhere, however, for the gradient in certain Rimianian fields, where the oils are found only in Tertiary strata, are lower than in the Bartlesville field, Oklahoma, where oil is derived from Pennsylvanian strata. The data available are not sufficient for generalization, although they indicate an attractive problem for study.

There is little exact data indicating the temperatures that formerly existed in oil fields. Some of the Sunset-Midway oils of California are over F. and, according to Pack,*were probably hotter at times of migration.

Willis states that the lowest strata of the Appalachian geoyncline when deeply buried probably had a temperature of about C.

Rogers, G. S. : The Sunset-Midway Oil Field, California, part 2. U. S. GeoL Survey Prof, Paper 117, pp. 37-42, 1919.

cit, pp. 42-43.

Pack, R. W. : The Sunset-Midway Oil Field, California. U. S. Geol. Survey Prof. Paper 116, p. 74, 1920.

Willis, Bahjst: Geologic Distillation of Petroleum. Bidl, Amer, Inst, Min, Eng, No. 157. sec. 10, pp. 1-7, 1920.

Geology Of Petroleum

GBoraBRUAL Gradient in Oil and in Other Regions'

Depth per

Depth

Tempera-

Degree of

of

ture at

Increase in

Remarks

Ofaaenrer

WeU

Bottom

Temperature

Feet

Deg. F.

Feet

Oa fields:

Sunset-Midway, Cafi-

f ornia

1,470-

Based on average of corrected

Rogers

3,870

temperature of water in 9 wells in western part of field

Bartlesrille, Oklahoma.

1,275

Woodruff*

Batson, Texas

Oil and wator well

Fenueman''

Florence, Colorado

Based on average temperature of oil produced by many wells

Washbume

Findlay, Ohio

Precise measurements

Johnston*

Wheeling, West Vir-

4,462

Precise measurements in dry hole

Halloek

Vera Orus, Mexico

2,276

Furbero oil field

Mohlberg'

Peehelbronn, Alsace . . .

25.3-38.3

Asphaltio shale oil

Branca*

Campina, Rumania —

2,726

Dry hole

Tanasesen

Lucaoesti-Zemes, Ru-

mania

Oil and water well

Tanascscu*

Bibi-Eibat, Apeheron

Peninsula, Russia . . .

2,695

Thermometer submerged for 11 hours in oil well

Goloubjatnikov/

Samarinda, Borneo

2,214

Oil well producing light paraffin oil

Mohlberg*

Echigo, Japan

2,381

Kawamura*

Other districtB:

'

Bay City. Michigan . . .

Lane'

Charleston, South Car-

olina

2,001

Temperature of outflowing

Knapp"*

water

""1'1'

Ames, loiro

. 2,100

129.6:

Predse measurements Precise measurements .

Beyer"

Maris, Holland

Beyer**

Schladebach, Germany.

6,630

Precise measurements

Dunkerf*

Paruschowits, Ger-

many

6,427

Predse measurements

Henrich'

'RooERB, G. 8. : The Sunset-Midway Oil Field, California, part 2. U. S. Qeol. Survey Prof. Paper 117, p. 41, 1919.

Personally communicated by N. H. Darton.

'Fbnneman, N. M.: Oil Fields of the Texas-Louisiana Qulf Coastal Plain. U. 8. Qeol. Survey Bull. 282, p. 56, 1906.

''Wabhbubnx, C. W.: The Florence Oil Field, Colorado. U. S. Qeol. Survey Bull. 381, p. 630, 1910.

'Johnston, John, and Adams, X.. H. : On the Measurement of Temperatures in Bore Holes. Econ. Geology, vol. 11, p. 741, 1916.

Hallock, William: Deep Well at Wheeling, West Virginia. Am. Jour. 8ei., 3d ser., vol. 43, pp. 234-236, 1892; School of Mine Quart., vol. 18, pp. 148-153, 1897.

Origin Of Petroleum And Natural Gas 95

'KoNiGBBBBOSB, J., and MOblbbbo, M.: On Measurementsof the Increase of Temperature in Bore Holes.. Inst. Min. Eng. (England) Trans., vol. 39, pp. 617-644, 1910

Branca, W.; Ver. Naturkunde in WOrttemberg Jahreshefte, 1897, p. 42.

*TANABBScn, I.: Etud Preliminaries but le Rlme Thermique. Inst. Geol. Romanei Annarult vol. 6, iase. la, p. Ill, 1912.

'GoiiOUBJATNiKOV, D.: Observations Gothermiques a Bibi-Eibat et Sourakhany (in Russian). Com. Geol. Mem., nouv. sr., livr. 141, p. 32, 1916. The observation cited is close to the average of several hundred careful measurements. The average gradient in the neighboring Sourakhany field is 44.5.

Kawamttba: On the Geothermio Gradient in the Echigo Oil Fields, Japan (in Japanese). Geol. Soc. Tokio Jour., vol. 19, pp. 179-185, 222-227, 1912.

'Lanb, a. C: The Geothermal Gradient in Michigan. Am. Jour, ScL, 4th ser., vol: 9, p. 435, 1900.

"Stsphxnson, L. W.: A Deep Well at Charleston, South Carolina. U. S. Geol. Survey Prof. Paper 90, p. 70, 1915.

", S. W.: Iowa Agricultural College Water Supply, pp. 13-14, Ames, 1897.

'Temperatur-Metingen in Diepe Boorgaten. Ryksoptporvng tan Ddfstoffen JtutrvenlaOt 1912, pp. 27-28.

'Dunkbb, E.: Ueber die TemperaturBeobacbtungen im Bohrlocbe zu Schladebach. Neues Jahrb., 1889, Band 1. pp. 29-47.

i', F.: Ueber die Temperaturverh&ltnisse in dem Bohrloch Paruschowits V. Zeit- . prakt, Oeologie, vol. 12, pp. 316-320, 1904.

Chapter Viii

Maps And Logs

Structural Contour Haps

Structural contour maps are used extensively in mapping oil

fields. They show approximately, by contours, the position of a

bed or horizon over the entire area mapped, and one familiar with

their use may picture the structure from them at a glance. As a

rule it is not possible to map a bed or horizon over a large folded

area. At some places it may be removed by erosion; at others it

may be concealed. Its outcrops are mapped and their elevations

noted at many places, with the dip and strike (Fig, 14). Its poai-

FiG. 14. — Sketches sbowiog parts of folds. (j4/ier WillU.)

tions in wellS are also recorded. Where it has been removed by erosion any bed below it that is now exposed is noted, and the former position of the bed to be mapped is estimated from its distance above the exposed bed in the geologic column as determined within or near the area.

If the structure is domatic the contours will "close," or pass all the way around the dome. Such a fold is called a "closed fold."

Maps And Logs

O

Emilcs

Fig. 15. — Sketch map showing elevation of the same stratum at diflfirent

points, marked by crosses. {After Gardner,)

o

(

_Jv

—

/aeo If

] %067

f

T

Fig. 16. — Sketch map showing elevations of same stratum at different points marked by crosses as in Fig. 15. The structure contours are drawn connecting points of equal elevation, thus outlining an elongated dome. {After Gardner

Fin. 17. — Lengthwise section of elongated dome shown in Fig. 16, vertical

scale greatly exaggerated. {After Gardner.)

&8 Geology Of Petroleum

Fig. 15 ifl a sketch showing elevations of the same stratum or horizon at different places. Fig. 16 is a sketch of the same area

Fig. 18. — Cross section and sketch of an anticline illustrating the use of Btnicture contours [above.) Structure contour map of the same antichne is shown below. The structure oontoura are drawn on the top of sandstone X Y Z. {After Hetoett and Lupton.)

Maps And Logs

with structural contours drawn to connect points of equal elevation. It outlines an elongated dome, or anticline, with at least 30 feet of closure. Fig. 17 is a lengthwise section of the anticline, in which the vertical scale is greatly exaggerated.

'rtlXtr y Line of outcrop- hfi-er '-I designahng bed

Line ofduHrop inferred Flowing scream Infermiffenf sfreotm '''z 1600-s, Contour Una

Contour inferred Dim rocfof or frail Rooid or highway Road station on bed Plane table station

X)

±

Tn'angulcrtion station Rod turning point on bed Length of shot anof percen t of dip Section comer, found Error of closure Lirof traverse (hot side shots Pepresiion contour Fault visible

Fault concealed or in f erred

'', Company holdings

NOTElMake the following symbols/ in oliqfneterj regardless scale of map

O Well .location <j) Temporarilyabondoned,well casing

© up not pulled

Prilling well Combination oil dnd gas well

Oil well X Oil seep at surf ace

Gas well Oil showing in drilled well

Pry hole abonchned Oas showing at surface

-4- Abondoned well jj Oas showing in drilled wett

"Y" Abondened gais well

Limestone Shale

Columnar sections must- show brief description of beds and depth to oil sands

Fig. 19. — Symbols commonly used on field maps. {AJier Woodruff.)

In ordinary mapping of beds having complicated structure it is not regarded good practice to use a vertical scale on the cross section that is different from the horizontal scale, because it gives a

100 Geology Of Petroleum

distorted picture of the Btructure. For mapping flat-lying rocks, however, this practice is necessary. In some fields the folds are so low that they can not be shown on a true scale. If a contour map ia used to depict the structure, together with the section, the amount of exaggeration is instantly apparent.

In some fields the relation of oil and gas accumulations to structure is very close. On the presence of a closure of 30 feet may depend the localization of 30 feet of sand saturated with oil or gas.

Angle Setiunn Krectioo of Dip and ttiroc+ion of Dip Component- Flo. 20. — Chart for determining the amount of true dip, when components are known, on lines oblique to line of dip. Horizontal lines represent true dip, curved lines represent dip components. (After Lahee.)

The mapping is done as accurately as is possible, with instruments of precision.

Small domes like that shown in Fig. 16 are typically developed in the oil fields of Oklahoma and Kansas. In fields in mountainous countries the structural features are larger and the dips steeper. Fig. 18 shows a sketch and cross section of an anticline, with a contour map.

It is desirable that as far as practicable the same symbols be

Maps And Logs ..,. . . .101

used on different maps. Fig. 19 is a chart prepared by E. G. Woodruff, showing symbols that are commonly used.

When the true direction of dip of a bed and the differences in elevations of the bed in different wells are known, it is frequently desirable to determine the amount of dip. Fig. 20 is a chart prepared by F. H. Lahee for this purpose. Suppose two well logs show a difference in elevation of a certain bed amounting to 30 feet to a mile in a direction N. 40° E. The true dip is known to be N- 80° E. The angle between the true dip and the dip component is 40°. The intersection of the vertical line marked "40°" with the curve marked "30'" indicates that the amount of the true dip between the two wells is about 40 feet to the mile.

In many fields, formations above the oil-bearing strata have the forms of flat-lying wedges, or are tabular bodies thicker at some places than at others, varying irregularly. To show these variations the convergence sheet is used. Such sheets are frequently made on transparent paper or cloth and placed above the map. The depth of the oil sand may then be readily estimated where the out-cropping horizons and elevation are accurately plotted. In the Appalachian region the Devonian rocks increase gradually from Ohio eastward. The rate of increase is shown by the parallellines in Fig. 101, after I. C. White. These lines show the convergence of the strata from east to west. The convergence sheet is used in drawing structural contours on the key bed, or on the oil-bearing

stratum.

Well Logs

Well logs are utilized when they are accessible. In fields covered with mantle rock these supply most of the detailed information. Some companies provide for samples to be taken, at regular intervals, from the holes, but as a rule the written well records only are accessible. That is particularly true in the United States where most fields are developed by two or more companies, and where, generally, there is a courteous interchange of such data. The driller's log depends principally upon the erudition of the driller and his previous experience. He often carries the names of rocks encountered in one district to another perhaps far removed, and in different surroundings. The rocks encountered with the cable or impact drill may be recorded differently when encountered. with the rotary driU which progresses by abrasion.

A "hard rock" is generally one that is hard to make progress in.

102 . . . . GQWQy OF PETROLEUM

If the cable system is used, a stratum of gypsum might be classed as a hard rock because it is elastic and not readily broken by blows, whereas a hard, brittle limestone which is easily drilled would be classed as 'soft." The gypsum would be classed as soft if the rotary system is used, because it is readily cut, whereas the limestone which resists abrasion would be hard.

'Slates" are reported in most logs of wells that are driven through argillaceous rocks that are more consoUdated than clays or soft shales. Oil sands are rocks that contain oil, whether sands, sandstones limestones, or dolomites.

With the rotary drill, a formation is 'sticky" which cuts in large pieces that adhere to the bit and drill pipe. A formation that is sticky with the rotary is usually sticky with the cable tools. On the other hand, formations are encountered in which the cable tools stick, owing either to the elasticity of the formation or to the fact that the drilled-up particles do not mix readily with the water in the hole and settle so quickly as to stick the bit. These formations might not appear sticky to the rotary driller.

The term "sandy" may be used accurately by the cable-tool driller. He obtains samples of the formation through which he passes, of sufficient size to determine the relative amount of sand to clay or sand to shale in any formation. In the case of the rotary drill, this term is misleading. The rotary well is drilled with the aid of a "mud" of varying density. It is usually a mixture of clay, sand, and water. It often contains as high as 40 to 50 per cent sand. As stated by Knapp, any change in the density of the mud changes its capacity to carry sand. Even a small shower falling on the slush pit will change the density enough to cause some of the suspended sand to be precipitated.* These properties of the mud lead to error in the observation of the formation. If a clay formation containing a moderate amount of sand is encountered while drilling in a mud low in sand content, the mud will absorb most of the sand, which will not settle out in the overflow ditch and its presence in the formation will not be noted, if not felt by the action of the bit in drilling. If, some time later, the mud is thinned by adding water this sand will appear in the overflow and may be attributed to a formation many feet below the one from which it actually originated.

Knapp, a. : Rock Classification from the Oil-driller's Standpoint. Mining and Metallurgy, sec. 26, No. 158, pp. 1-6, February, 1920.

Maps And Logs 103

The so-called "jigging" action of the rising column of mud on the sand or cuttings also leads to misinterpretation. The deeper the drill, the finer the sand in cuttings brought to the surface by mud. As stated by Knapp, the coarser particles are pounded into the walls of the well or broken.

A change in the speed of pumping the mud also causes a change in the amount and size of the cuttings that appear at the surface. Thus, in the case of the rotary, "sandy" may have little or no meaning when applied to a formation. The term sandy is often used in contradistinction to sticky. A formation that drills easily and is not sticky is often recorded as sandy because sand tends to decrease stickiness.

A wet specimen, fresh from the hole, has a different color from the same specimen dried. Many specimens, when dried, bleach. Many of them air slack or oxidize. The terms, light and dark should be used only for the extremes. They are, in general, relative. A sample of wet shale examined under an electric light might appear darker than in daylight. The terms indicating shades are more definite than light and dark, and are recommended by Knapp.

Clay is readily recognized by the "feel of the bit" while drilling with either cable tools or rotary. To some drillers all clay is gumbo while to others gumbo is only sticky clay. Some clays have the property of cutting in large pieces but do not adhere excessively to the bit and drill pipe and are designated as "tough."

Free, uncemented sand is easily recognized by the feel of the tools in both systems of drilling. "Packed sand" is a sand that is slightly cemented with some soft, easily-broken cementing material, such as calcium carbonate. It cuts, when drilled with a rotary, with much the same feeling as when cutting crayon with a knife. The cementing material is dissolved or broken before reaching the surface, so that the driller finds only sand in the overflow. A microscopic examination of sands from the overflow often shows cementing material to be present when not suspected by the action of the bit.

A quicksand is one that caves or sticks the tools; a heaving sand is one that rises in the bore. A "shell" may be the test of an organism or a thin layer of any kind of sedimentary rock.

Geology Of Petroleum

I 1

fill

It

ll-ilifi 11 ilim I'f titi

s

I I

'" ' 1 li ,

11 I J I fa lllail 111 Ifll

Chapter Ix

Accumulation Of Petroleum

Water, oil, and gas in porous strata tend to arrange themselves in accordance with their density — the oil above the water and the gas above the oil (Fig. 21). In folded rocks that are saturated with water, oil, and gas, the oil and gas rise to the crests of the upfolds, or anticlines, and the water is found on the flanks of the anticlines and in synclines. If the rocks are dry the oil is found low on the folds or in synclines. If some water is present, the oil floats on the water and will be found low on the anticlines, its position

yOlI and Gai

FiQ. 21. — Section through Bartlesville field, Oklahoma. {After

Becd.)

depending on the amount of water present. On monoclines that are sealed the oil rises above the water, and the gas above the oil.

The Anticlinal Theory

The theory of gravitational arrangement according to density is generally referred to as the anticlinal theory or the structural theory. This theory was formulated as a result of work in the Appalachian field of the United States and in the Ontario field. It is doubtful, however, whether the theory meets so many difficulties in any other large oil field in the world, as in the Appalachian region, where many of the sands are not saturated with water. In these sands the oil is found far down on the flanks of the anticlines and in synclines. At some places, especially in the well-known fields in Pennsylvania near Pittsburgh, these sands are very productive, and it was natural that the theory should have met a lack of enthusiasm where pronounced exceptions to it were so prominently displayed.

The fact that oil and gas and water will separate by gravity was

t

106 Geology Of Petroleum

first noted in America by Andrews* and by Hunt.* Andrews had studied the Burning Springs- Volcano anticline of West Virginia, and Hunt the Petrolia and Oil Springs domes of Lambton County, Ontario. In these localities the segregation of oil and its accumulation at the tops of domes is very marked. (See Figs. 13 and 26.)

Alexander Winchell and J. S. Newberry gave the theory a more definite form. Winchell* based his conclusions chiefly on the relations he had observed in Ontario, and Newberry* on the areas in western Pennsylvania, West Virginia, and eastern Ohio. In the years immediately following these discussions the theory made little progress. The fields of Pennsylvania were then being developed, and in these fields many of the accumulations are in sjclines. Lesley® and his associates of the Pennsylvania Geological Survey opposed the anticlinal theory. The theory was discredited in many quarters, because so many exceptions to it had been found. I. C. White revived it, worked out many problems nearly related to it, and was probably the first investigator to use it in a practical way.

Orton agreed with White as to his main contention and soon after the discovery of oil in the Trenton fields of Ohio and Indiana made a survey of the fields and found that accumulations were on or near anticlinal axes and on terraces, or "arrested anti-

Engler and Hoefer state that Oldham recognized a connection between the anticline and oil accumulation at Yenangyaung in 1855 (Das Erdoel, Band 2, p. 18).

Andrews, E. B.: Rock Oil, Its Relations and Distribution. Am. Jour. Sd., 2d ser., vol. 32, pp. 85-91, 1861.

HuNT, T. S. : Notes on the Geology of Petroleum or Rock Oil. Canadian Naturalisty vol. 6, pp. 241-255, 1861.

*WiNCHELL, Alexander: On the Oil Formation in Michigan and Elsewhere. Am. Jour. Sci., 2d ser., vol. 39, p. 352, 1865; Something About Petroleum, in Sketches of Creation, Harper & Brother, 1870; also notes in appendix about initial production of Ontario wells.

'Newberry, J. S.: Devonian System. Ohio Geol. Survey, vol. 1, p. 160,

Lesley, J. P.: Geology of the Pittsburgh Coal Region. Am. Inst. Min. Eng. Tram.y vol. 14, pp.' 654-655, 1886.

AsHBURNER, C. A. '. The Production and Exhaustion of the Oil Regions of Pennsylvania and New York. Am. Inst. Min. Eng. Trans, f vol. 14, pp. 419- 428, 1886; The Geology of Natural Gas. Idem, p. 434.

White, I. C. : The Geology of Natural Gas. Science, vol. 6, Jime 26, 1885; Petroleum and Natural Gas. West Virginia Geol. Survey, vol. A, pp. 4-64, 1904 (a reprint and amphfication of the first paper).

Accumulation Of Petroleum 107

clines," where there was a flattening of the northward dip of the strata. Later Orton published a monograph on the Lima- Indiana field.* In this paper he amphfied his former discoveries and presented a map,* which is probably the first contour map drawn for the purpose of showing structure in an oil field. This report marks .a decided advance in geologic methods applied to mapping the structure of oil fields. It was followed by a series of brilliant papers by mn engaged in the survey of the Appalachian oil region by the United States and Pennsylvania geological surveys, xmder the direction of Campbell. These reports and the structural contour maps accompanying them have shown that oil and gas occur at the tops of structural uplifts in saturated rocks and lower in imsaturated rocks. Woolsey in 1906 noted that the oil was found high in anticUnes where the beds contain water and in the hollows of synclines where they do not. F. G. Clappand Stone and Clapp* investigated further the occurrence and relations of oil, gas, and water in unsaturated synchnes. Griswold and Munn in 1907 made a detailed report on a large area in south* western Pennsylvania in which the oil in the saturated rocks, the Big Injim sand and beds above it was found in the higher parts anticUnes, and that in the unsaturated rocks, the Squaw sand and those below it, on the flanks of anticUnes and in synclines. (See Fig. 63.) They suggested the hypothesis that the unsaturated rocks had formerly been saturated and partly drained. Later Reeves® reviewed the problem and noted that the imsaturated

Orton, Edward: The Origin and Accumulation of Petroleum and Natural Gas. Ohio Geol. Survey,, vol. 6, p. 94, 1888.

Edward : The Trenton Limestone as a Source of Petroleum and Inflammable Gas in Ohio and Indiana. U. S. Geol. Survey Eighth Ann, Rept, part 2, pp. 475-662, 1889.

Idenif pi. 55, opp. p. 548.

*WooL8ET, L. H. : Economic Geology of the Beaver Quadrangle, Pennsylvania. U. S. Geol. Survey BvU, 286, p. 81, 1906.

KDlapp, F. G. : Economic Geology of the Amity Quadrangle, Pennsylvania. U. S. Geol. Survey BuU. 300, pp. 1-145, 1907.

Stone, R. W., and Clapp, F. G. : Oil and Gas of Greene County, Pennsylvania. U. S. Geol. Survey BuU. 304, pp. 79-82, 1907.

Griswold, W. T. and Munn, M. J. : Geology of the Steubenville, Burgettstown, and Claysville Quadrangles, Ohio, West Virginia, and Pennsylvania. U. S. GeoL Survey BuU, 318, 1907.

Reeves, Frank: The Absence of Water in Certain Sandstones of Appalachian Oil Fields. Econ. Geology, vol. 12, pp. 354-378, 1917.

f

108 Geology Of Petroleum

rocks in the Catskill of the Devonian are a fresh-water or terriginous series that was probably dry when buried below the sea. He recorded great flows of salt water from deep wells below the Devonian, opposing suggestions made earlier that the Catskill rock had dried out after being buried.

During the development of the California oil fields, Arnold and his associates worked out the structural details of accumulations. They foimd that the principal oil pools are op anticlines and monoclines sealed with asphalt or by faults.

Later the structural relations in the Illinois fields were foimd to accord with the gravitational theory. The accumulations of the Kansas, Oklahoma, Texas, Louisiana and Wyoming fields were found to be in accord with it except wher the rocks are dry. Sonie of the deposits are found in sealed monoclines or terraces, but the gravitational arrangement is in general clearly expressed. Nearly every governmental report on an oil field in any coimtry that has been published in recent years discusses the relations of the accumulation to structure. These relations are treated elsewhere (pp. 120-169).

The differences in the surface tension of oil and water cause them to separate, the oil and gas occupying the large spaces and the water the smaller ones. This segregation, as pointed out by Washburne,* attends gravitational separation, and its influence has been noted in many fields (p. 112).

The theory of gravitational separation of gas, oil, and water is

demonstrated in so many fields, so widely separated, and under so

many different conditions that additional proof is not required to

substantiate it. The gas is above, and with the oil, and generally

both are above salt water. This arrangement is modified by capil-

Arnold, Ralph and Anderson, Robert: Geology and Oil Resources of the

Ckialinga District, California. U. S. Geol. Survey BvU. 398, pp. 1-354, 1910.

Arnold, Ralph and Johnson, H. R. : Preliminary Report on the McKittrick-Sunset Oil Region, Kern and San Luis Obispo Counties, California. U. S. Geol. Survey BvU, 406, pp. 1-225, 1910.

Eldridge, G. H., and Arnold, Ralph: The Santa Clara Valley, Puente Hills, and Los Angeles Districts, Southern California. U. S. GeoL Survey Butt. 309, pp. 1-266, 1907.

K])lapp, F. G. : Revision of the Structural Classification of Petroleiun and Natural Gas Fields. Geol. Soc. America BwZZ., vol. 28, pp. 553-602, 1916.

Washburnb, C. W. : The Capillary Concentration of Gas and Oil. Am. Inst. Min. Eng. BvU, 93, pp. 2365-2378, 1914.

Accumulation Of Petroleum 109

lary attraction. Where there are great differences in the sizes of the openings that constitute the reservoirs, the water cUngs tenaciously to the smaller openings, and the larger ones are filled with oil and gas./ To some, however, this theory appears inadeqiiate. In many fields the Une between water and oil is not level. The amount of oil that can be removed from a reservoir is estimated to be 10 to 75 per cent of that originally contained. In some porous sandstones so much oil remains that after drying they contain from 4 to 8 per cent or more of bitumen. Originally the oil sands must have contained much less than 4 per cent, for in many fields the expanses of the "dry" oil sands are at least 20 times as great as the producing, areas. The unproductive parts of the oil sands, moreover, are either essentially barren of oil or contain much less than the parts that have been drained by man. Evidently nature's process of accumulating an oil poot is more efficient than man's process of draining it.

Various theories have been proposed as corjfllaries to the anticlinal theory. Of these the hydromotive theory of Munn is perhaps the best known. He suggests that bodies of water in motion carry the oil with them. If the water moved downward or later- aDyit could carry the oil with it, and the oil carried down would tend to float into any higher structural features it encountered and accmnulate in them. The higher folds would serve as oil traps raised above the passageways of water and oil. If, in depths below the higher folds the sands were for any reason impermeable, the downward flow would turn to a horizontal course and larger volumes of water might pass below the oil trap, giving greater opportunities for segregation.

Johnston' suggests that the oil is carried through the sands as films on globules of gas. Daly* appeals to pressures generated as a result of diastrophic movement. These methods of segregation probably assist gravitationfi.1 separation to some extent.

There is reason to suppose that the temperatures of the oil

Lewis, J. O. : Methods for Increasing the Recovery from Oil Sands. U. S. Bur. Mines BuU, 148, pp. 25-28, 1917.

*MuNN, M. J. : The Anticlinal and Hydraulic Theories of Oil Accumulation. Earn. Geology, vol. 4, pp. 609-529, 1909.

Johnston, R. W. : The Accumulation of Oil and Gas in Sandstone. Science, new ser., vol. 35, pp. 458-459, 1912.

*Dalt, Marcel: Water Surfaces in the Oil Fields. Am. Inst. Min. Eng. Trans,, vol. 69, pp. 657-563, 1918.

Geology Of Petroleum

measures have, in general, been higher than they are now. The water ejected from the Dos Bocas well in Mexico, was hot. The temperatures of muds ejected from a mud volcano oflf the coast of Burma was 148° F. In many fields there is reason to suppose that temperatures in the oil sands have been as high as 70° C. Oil loses viscosity with increase of temperature and would be less readily adsorbed by grains of sand. At depths of 6,000 feet some oils would be no more viscous than water.*If a vessel is filled with sand that is saturated with oil, and the bottom is perforated so that all the oil that can be removed by gravity will drain out,

. (a) T

Glass tube bent to represent anticline.

Glass tube filled with oil sand and sea water, acidified with acetic acid. Ground

. dolomite was introduced at A and A'.

(c)

Same as 22b, after 48 hours. AA' is dolomite; BB' sea water in sand; CO' segregation of oil in sand; D accumulation of gas in sand.

Fig. 22. — Experiment illustrating accumulation of oil and gas in sand.

much oil will remain in the sand. If air is blown through the sand, more oil will be removed. If water, hot water, and superheated water, are successively passed, through, additional oil will be carried out with each. The water of oil fields is probably rarely as hot as steam, but efficiency to overcome adhesion is aided, doubtless, by high temperature. Oil will absorb more gas than water, and the gas makes it lighter and assists accumulation. An increase of temperature of only 50° C. will decrease the density of

iWashburne, C. W. : The R61e and Fate of Connate Water in Oil Sands, Am. Inst. Min. Eng. Trans., vol. 51, p. 607, 191$.

N

Accumulation Of Petroleum 111

oil appreciably, increasing the difference in weight between oil and water.

A series of experiments has recently been made in the geological department of the University of Minnesota, in which gas was introduced into an oil-soaked sand in a closed system. Tubes about six feet long, were bent to form anticlines of which the limbs had slopes of about 15 degrees. (Fig. 22a.) These were filled with sand which had been mixed with oil. The amount of oil introduced was only that which adhered to the sand, the excess having been drained away. This was charged, together with sea water which had been made slightly acid with acetic acid. The tube was completely filled with the mixture and allowed to remain a considerable period, as shown by Fig. 226. No segregation took place except locally, where the oil gathered into small drops. Subsequently small amoimts of dolomitic limestone were introduced at each end of the tube (Fig. 226; A, A') After forty-eight hours a considerable segregation of oil, gas, and water had taken place. (Fig. 22c). The gas occupied the highest part of the tube (D), and rested on oil (C, C'), which in turn rested on salt water (B, B') The space occupied by the gas represents air spaces which it was not possible to eliminate in charging the water and the oil soaked sand in the tube, together with the space made available by the gas "pressure forcing liquids into small cracks of the sand.

The method of segregation is due principally to gravity. Gravity, however, will not operate in the absence of gas, because adhesion is great enough to hold the oil tightly to the sand. The gas generated presses on both oil and water, but the oil being lighter is pushed up farther and rides above the water. It is clear that the oil is not carried by the gas as films on gas bubbles, because the amount of oil is much greater than would be required to form films. A small amount of gas seems to be as effective as a large amount, provided the pressure is sufficient. That the pressure is effective, rather than the movement of the gas, is clear from additional experiments. The system, with acid and dolomite, was set up exactly as is shown in Fig. 22c, but the tube was arranged to represent a sjmcUne rather than an anticline. The gas rose on either limb, near the end of the tube, the oil below the gas, and water segregated below the oil. A terrace was set up, the tube being bent so

, G. a. : Gas an Important Factor in Oil Occurrence, Eng. and Min. Jour,, vol. 109, p. 888, 1920.

Geology Of Petroleum

that two anns sloped approximately 15. Between the two arms the tube was level, as it was also at the upper end. . After being charged with oil soaked sand, acidified sea water and dolomite, the oil rose to the first level of the terrace and remained several days. Subsequently it moved up the higher inclined arm to the flat portion of the tube. There was a strong tendency for the maximum accumulation to remain in the flat part of the tube nearest the bent Umb.

In other experiments gasoUne or ether was used instead of acid and dolomite. On warming the system similar results were obtained.

Segregation Of Oil And Water Due To Differences In Their

Surface Tension

Surface tension is the tension of a liquid by virtue of which it acts as an elastic enveloping membrane, tending always to contract to the minimum area. It is best exemplified in films freed from liquid masses, as in soap bubbles, and in the formation of drops. It is commonly explained as due to the fact that while molecules in the interior of the liquid are attracted in all directions, and are thus in equilibrium, those on the surface have no neighbors outside to balance the attraction of those within and are consequently acted upon by a resultant force tending toward the interior. .

Capillary Constants of the Paraffin Series*

'Compiled by C. W. Washburne. Dynes per centimeter.

Substance

Tempera-

Surface

Substance

Tempera-

Surface

(Normal)

ture,

Tension

(Normal)

ture,

Tenaion

Deg. C.

Deg. C.

Ci&Hss

C16H.4

Accumulation Of Petroleum 113

As a result of surface tension, water and oil will be drawn into small openings of capillary size, regardless of the force of gravity. Examples are the movements of water into a sponge or the rise of oil in a lamp wick The surface tension of a water-air surface is about 75.6 dynes per centimeter at 0° C. and 72,8 dynes at 20° C Washbume' states that the surface tension of salt water such as isfoundin oil fields is 79 dynes per centimeter. Washbume found also that Pennsylvania crude oil (specific gravity 0.852) had a tension of 24 dynes at 20° C.

As water has about three times the surface tension of crude oil, capillary action must exert about three times as much pull upon

23B. — View of apparatus illustrated in Fig. 23A, ahowing accumubtion of oil in coarse sand after movemeut from oiT-soaked mud. (Afl McCoy.)

it. The amount of the capillary pull varies inversely as the diameter of a pore. Hence the constant tendency of capillarity is to draw water rather than oil into the finest openings, displacing the gas and oil in them. Gae can not be drawn into capillary opening

'Washbobnb, C. W. ; The Capillary Concentration of Gas and Oil. Am. Inst. Min. Eng. Tran., vol. 50, pp. 829-842, 1914.

The movements of oil and water in quartz sand, due to diSerencea in surface tension, are probably similar to movements in contact with glass. In clayey containers the results may be quantitatively diSerenl, Exact data are not available.

Geology Of Petroleum

Mr*0

kffyt

9D'mt

UmiAKtiwWfe'b Oilpoo|>'m . . StrueUnContMin (MfooliHiTiNrd jOil pools m Ml rltfirindfoet Sand

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Ik.M prvtfuc* ( iait WOMO >Wld. ntaCuin 1000

Ur Sand Sand SIM aMd BowUcT

Sands

(No Wtt waUrJi (No toit woUr)

FiQ. 24. — Map showing oil wells in Sewickley quadrangle, Pennsylvania.

(il/<er Afwnn.)

by surface tension, hence water can force it out of the fine pores without any resistance. Therefore, as stated by Washburne, gas is the most quickly and completely gathered in the largest 0p. 7., p. 832.

ACCUMULATION Of PETROLEUM 115

openings available. Capillarity, moreover, reaiBts the movement of water from fine to large pores

more than it resists the move-

ment of oil and gas from them. i jj

Thus water will enter fine capil- I

laries about three times as readily § §

aa oil, and it encounters about 1.

three times as much capillary re- I

Stance in leaving them, Conse- ll J

quently oil and gas are concen- u

trated in the largest openings, as -f

the laiest openings have the

least capillary power.

Capillary action is not exerted -b

in supercapillary openings. (See

p. 41.) As water is moat readily £

removed from such openings by jS

capillary action in the surround-

ing material they are moat readily '§

filled with oil and gae.

Capillary attractions decrease &fc

with increase of temperature and .g §

therefore with increase of depth. %

With an increase of 1" C. per 30

meters in depth, capillary action -g

loses half its force at a depth of i

about 5,000 meters. As heat in- "S

creases more rapidly downward &ri 2

inmany oil fields than the normal B S,

increase, it is probable, according J I J

to Washbume, that capillary a'3

force decreases one-half at depths a

' of 3,000 or 4,000 meters. More-

over, the surface tensions of all \S. A

but the latest hydrocarbons de-

crease much less rapidly than that "1 8

of water for each increment of g

temperature, so that the surface tension of water does not have such great excess over that of oil at these depths. Hence it is

116 Geology Of Petroleum

probable that the capillary concentration of oil and gas must all be effected within 4,000 or 5,000 meters of the ground surface. Oil in deeper strata must remain diffused in the shales, if that was its original distribution, unless it was concentrated in the sands at some former period when the strata concerned were closer to the surface.

If oil-soaked mud is placed near water-soaked sand the oil will move to the sand. McCoy placed in a glass box a water-soaked sand Fig. 23A) in which was a layer of coarser sand (A). Above the sand was placed water-soaked mud (C), containing a layer of oil-soaked mud (D). Two series of these beds at different levels were separated by a celluloid sheet (E), representing a fault. Within one hour after removal of the sheet, oil began to collect in the layer of the sand having the largest pores, and it continued to do so for several hours imtil the porous sand was nearly filled on eachside of the plane representing the fault (Fig. 23B). Water, by capillary action, had partly replaced the oil in the oil-soaked mud.

In the Sewickley quadrangle, near Pittsbiuh, Pennsylvania, oil is produced from the Catskill sands (Devonian) and from the Hundred-foot sand, near or above the top of the Devonian. The Hundred-foot sand is from 30 to 125 feet thick and is saturated with salt water. The sand is of medium grain and porosity and contains lenses of coarse sandstone and conglomerate which are much more porous than the surrounding sand. The porous lenses are a mile long, more or less, and a few feet thick. Practically all the oil is concentrated in them. The country is thrown into very gentle folds, and nearly all the lenses or "pay streaks" that contain oil are in the higher parts of the anticlines. The oil is associated with gas imder pressure and with salt water. Down the dip and in synclines the pay streaks generally carry water only. Some of the wells have flowed as much as 2,000 barrels of oil a day. This area is shown in the accompanying map (Fig. 24). The section in Fig. 25 illustrates the occmrence of oil on anticlines in the pay streaks. The pools lower on the flanks of anticUnes and in synclines in the sands below the Hundred-foot sand (Fig. 24) are noteworthy.

>McCoT, A. W.: Notes on Principles of Oil Accumulation. Jour. Geol. vol. 27, pp. 262-262, 1919.

'MuNN, M. J. : Studies in the Anticlinal Theory of Oil and Gas Accumulation.con. Geology, vol. 4, pp. 141-157, 1909.

Accumulation Of Petroleum 117

Fractionation Of Petroleum In Clay

It has been suggested that some white oils and some very light oils have been formed by the fractionation of petroleum that has passed through clay. When oil is mixed with fuller's earth and then displaced with water about two-thirds of the oil will pass out and one-third of the oil will remain in the earth. As shown by Day and his associates, oil passing through a dry fine clay (fuller's earth) loses its sulphur compounds, unsaturated compounds, and heavier components more readily than its Ughter ones.

When petroleum is allowed to rise in a tube packed with dry fuller's earth, the fraction at the top of the tube is Ughter than the one at the bottom. When water is added to fuller's earth that contains petroleum, the oil which is displaced first differs in specific gravity from that which is displaced afterward, when more water is added. The paraffin hydrocarbons tend to collect in the lightest fraction at the top of the tube, and the unsaturated hydrocarbons at the bottom.

*Dat, D. T.: Experiments on the Diffusion of Crude Petroleum Through Fuller's Earth. Science, new ser., vol. 17, pp. 1007-1008, 1903.

Gilpin, J. E., and Cram, M. P.: The Fractionation of Crude Petroleimi by Capillary Diffusion. U. S. Geol. Survey Bull 365, pp. 1-33, 1908.

Gilpin, J. E., and Branskt, O. E.: The Diffusion of Crude Petroleum Through Fuller's Earth, with Notes on Its Geologic Significance. U. S. Geol. Survey BitlL 475, pp. 1-50, 1911.

Geology Of Petroleum

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Accumulation Of Petroleum

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Chapter X

STRUCTDSAL FEATURES OF OIL AND GAS RESERVOIRS RESERVOIRS IN ANHCUIVES AlVD DOMES

Occturence. — In accordance with the gravitational theory of accumulation, where reservoir rocks are saturated with salt water, oil will rise above the water and gas above the oil. On a fully developed, regular structural dome the normal arrangement would be a circular area of gas wells surrounded by a belt of oil wells, which in turn is surrounded by an area containing salt-water wells only. This ideal arrangement is not the most common one in oil fields, because most structural featiu-es are irregular in form, and oil sands rarely have uniform porosity. Gas and oil, moreover, in many petroleum fields occur together and will issue simultaneously from wells drilled on the tops of folds. In many folds the water is not clearly segregated from the oil. Many wells yield mixtures, some of them emulsions of oil and water. Size of pores also influences segregation (p. 112). There is, nevertheless, in almost every great oU field in the world a distinct segregation of oil and gas in the higher parts of the uplifts.

In the Appalachian oil field of North America oil and gas are generally acciunulated in anticlines except in terrestrial rocks, the sands of which are not saturated with water. The Venango group of southwestern Pennsylvania is a prolific series of dry or partly dry sands in which much of the oil is found in synclines. In the Carboniferous strata above the Venango group the oil is found in saturated rocks and accumulates near the tops of the anticlines. In the Volcano anticline of West Virginia the oil has acciunulated near the crest of a dome (Fig. 26). In the Lima-Indiana field of Ohio and Indiana, where oil is found in the Trenton limestone, the accumulation lies below or near a broad anticlinal axis that extends northward from the vicinity of Cincinnati and branches, one end trending toward the south end of Lake Michigan, and the other toward the west end of Lake Erie. In Ohio the best yield is obtained below the arch and on terraces; in Indiana it is found on the north side of the arch, where the rocks dip northeast. The east branch of the axis of the Cincinnati anticline becomes essentially

Structural Features Of Reservoirs 123,

Explanation

Gm WeU Dry Hote

— Straeturo Contour Ltoea, showing Elevation of Wasbloston Coal -Bed above Tide

H H 0 12 8 4

Scale of Miles

Fig. 26. — Contour map of a part of the Volcano anticline, Wood, Richie. Wirt and Pleasants Counties, West Virginia. Contour interval 100 feet. (After White, Grimsley and Hennen, West Virginia GeoL Survey,)

flat north of Lake Erie, in the region of Lake St. Clair. North of Lake St. Clair, however, an axis may be traced northeastward to the Petrolia dome, in Lambton* County, Ontario. Practically all

Geology Of Petroleum

the oil produced in Canada has come from Lambton and Middlesex Counties, Ontario, where at Petrolia, at Oil Springs, and in Mosa Township the oil has accumulated in well-defined domes.

Fig. 27. — Sketch showing structure of principal oil region of Lambton County,

Ontario. {After Williams.)

In this district a subordinate amoujut of oil has been found also on anticlinal noses on the flanks of the domes. (Figs. 27, 28).

Structural Features Of Reservoirs 123 .

Classification op Oil and Gas Reservoirs

A. Mevated structural features.

' 1. Anticlines and domes: Appalachian fields and Lima-Indiana in part, southwestern Ontario, Illiuoia, Mid-Continent field, Wyoming, California, Gulf coast ; Mexico {domes near intrusives); Trinidad; Colombia, Galicia; Rumania; Baku, Grozny, Sviatoi, and Cheleken, Russia; Burma; Oceanica; Japan.

2. Monoclines sealed by

(a) Overlying and underlying shales, joining above reservoirs: Appalachian fields, in Pennsylvania, West Virginia, and Ohio, in part, some Mid-Conti-

(6) Faulting: Los Angeles, California; Benigadi, Russia; eSuudci Rumania and Galicia in

(c) Local cementation of reser- XfjJI

voir rock: Glenn pool, Oklahoma; probably many others.

(d) Asphalt: Coalinga and Mc- ' Kit trick-Mid way-Sunset

6elds, California in part, (c) Unconformities: Maikop

Russia, Douglas, Wyom-

ing. if) Igneous intrusions: Tux-

pam-Tampico field, Vera

Cruz, Mexico.

B. riat-lyii beds.

1. Aclines including oil sands: Como- (in part); New Plymouth, Paritutu, New Zealand. 2. Flat-lying lenses.

3 Terraces: Pennsylvania, Ohio-Indiana, districts in eaj Kansas-Oklahoma field in part.

h

Geology Of Petroleum

C. Depressed structural features.

1. Synclines and basins: Catskill sands in Pennsylvania and West Virginia; some parts of fields of California and Galicia; unimportant districts of Rocky Mountain fields.

D Fissures.

1. In shales: Florence, Colorado; part of Salt Creek, Wyoming; part of

Cleveland, Ohio.

2. In schists: Small occurrences of Santa Clara, California and Alaska.

3. In igneous rocks: Cuba; part of Furbero, Mexico.

E. Combinations of two or more structural features named above: Numerous fields.

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In Kentucky the principal producing fields are on anticlines; these include Irvine, Campion, Station, and Cannel City.

In Illinois the principal producing wells are along the La Salle anticline, especially in domes that are on and near the crest of the anticline in Lawrence, Crawford, Clark, and Cumberland Counties. In the southwestern part of the State oil is found in

Structural Features Of Reservoirs 125

126 Geology Of Petroleum

small pools at or near the crests of domes in Sandoval, Marion County, in Carlinville, Macoupin County, and in Greenville, Bond County. In the Carlyle field, Clinton County, the beds are practically horizontal. Within short distances they dip away from the field or become tight.

In many districts in the Oklahoma-Kansas region the oil and gas are clearly segregated at the tops of anticlines and domes. These include the accumulations of the Cushing, Ponca City, Garber, Augusta, Eldorado, and many other fields. East of a north-south Une through Tulsa, Oklahoma, the rocks are less highly saturated and some of the pools are on structural terraces. Some are on comparatively regular monoclines. In the Bartlesville field, Oklahoma, which has been highly productive, the monoclinal dip is nearly uniform at many places. Where it is not the oil is concentrated on slight upwarps of the undulatory strata. In the lola field of Kansas the anticlinal structure is barely perceptible, although, according to Orton, it may be measured over very broad arcs. In the western part of the Kansas field the oil pools are on anticlines and domes.

In the Red River district, south of the Arbuckle Mountains, in southern Oklahoma and northern Texas, oil or gas or both have accumulated in domes or anticUnes in the Healdton (Figs. 29,30), Fox, Graham, Loco, and Duncan fields. In Texas the Petrolia field is a dome; the Electra and Burkbiu-nett pools are probably anticlinal deposits in areas complicated by faulting. In the Ranger and neighboring districts the oil pools are on the Great Bend arch, below small anticUnal noses that are generally without recognized closure at the surface. It is thought by some investigators that the amplitudes of these folds increase with depth, and there is some evidence that the folds are also closed in depth. In the Corsicana field, Texas, some of the pools are on an essentially regular monocline that shows no closed folds, but others are on domes on the monocline. The Mexia-Groesbeck gas field and the Thrall oil field are on domes.

In northern Louisiana oil or gas or both are found on domes in the Caddo, Shreveport, De Soto-Red River, Pelican, Homer, and Monroe fields. In the Homer and Red River-De Soto fields pronounced faults are found near the crests of the producing domes. On the Gulf coast in Texas and Louisiana oil is found in many salt domes, which are believed to lie along axes of faulting and flexing.

Structural Features Of Reservoirs 127

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o

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o

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128 Geology Of Petroleum

In the Rocky Mountain fields all the oil in the principal producing districts is derived from deposits lying on domes and anticlines. In Wyoming, which produces about 97 per cent of the oil and gas from the Rocky Mountain fields, more than 98 per cent of the output (1917) is derived from fields having closed structure. Of these fields about 15 produce oil, and several others produce gas only. All the elevated closed folds are domes except one or possibly two. In one of these the oil is accumulated in a fault trap formed by an anticline plunging away from a fault. In the Salt Creek field (Fig. 31), which is the most productive in Wyoming, oil occurs on a dome. On this dome and west of it oil is derived from fissures in shale. In the Shannon field, north of the Salt Creek field, a little oil has been obtained from a small half dome or nose. In the Spring Valley district, Uinta County, in the southwest corner of the State, a few thousand barrels have been obtained from wells sunk in a syncline.

In the Boulder district, Colorado, oil is derived from thin sands in a shale and probably from fissures in the shale also. In the northern extension of this district flowing wells were brought in pn an anticline.

/ In California the oil-bearing rocks are generally saturated andthe oil and gas are found on uplifts. The Coalinga field is divided into two parts, the Eastside and Westside. On the Westside the oil has accumulated on a monocline where at the outcrop the oil sands are cemented with asphalt. On the Eastside the oil is concentrated below the Coalinga anticline. In the Lost Hills district, Kern Coxmty, about 50 miles southeast of the Coalinga district, oil is accumulated on the extension of the Coalinga anticline.' The Midway district, on the northeast flank of the Temblor Range, is on a monocline on which two subsidiary folds are developed. These folds have undulating crests, and the best yield, according to Arnold and Johnson, is obtained on or near the nodes of the crests. In the McKittrick field oil is found in anticlines and in synclines, the rocks being overturned, and on monocUnes

Arnold, Ralph, and Anderson, Robert: Geology and Oil Resources of the Coalinga District, California. U. S. Geol. Survey BvU, 398, pp. 1-354,

Arnold, Ralph and Garfias, V. R. : Geology and Technology of the California Oil Fields. Am. Inst. Min. Eng. BvU. 87, p. 422, 1914.

Arnold, R., and Johnson, H. R. : Preliminary Report on the McKittrick- Sunset Oil Region. U. S. Geol. Survey Bull 406, p. 165, 1910.

Structural Features Of Reservoirs 129

where the beds are healed by asphalt. The Kern River field, in Kern County, 4 miles north of Bakersfield, is on a low dome on a general monocline, superimposed on which are minor folds that control accumulation. The Santa Clara district, in Ventura and Los Angeles Counties, is structurally dominated by an overturned anticline. In this field the structure is exceedingly compUcated. One part of the field is situated in a syncUne. A few wells have encountered some oil in schists. In the Santa Maria field oil is accumulated principally on anticlines.* In the Summerland field, a small district near shore and below the Pacific Ocean, the relation of accumulation to structure is not clear. In the Los Angeles field oil is accumulated near the crest of an anticline and in amonocline developed on its limb where the oil-bearing strata crop out (Fig. 182, p. 465). In part of the field the oil appears to be sealed in by the faulting of shales against the reservoir rock. In the Puente Hills district the oil is found on anticlines and on monoclines sealed by faults.'

In foreign fields nearly all the petroleum and natural gas is found in the elevated parts of structures.

Southwestern Ontario has supplied most of the petroleimi discovered in Canada. The oil is obtained mainly from clearly defined domes, although a Uttle has been obtained from open anticlines and on monoclines.*

In Mexico all the large wells are located where the structure is anticlinal or domical and the rock shows pronounced fractiu'es, usually in the regions of basaltic intrusives. In the Furbero dis trict, at the south end of the oil region, oil is found in an indurated and shattered shale above an igneous sill. In Trinidad oil is found on anticlines.

All the oil produced in Europe, Asia, and Africa comes from

Arnold, Ralph, and Garfias, V. R., op, dt, p. 436.

Arnold, Ralph, and Anderson, Robert: Preliminary Report on the Santa Maria Oil District. . U. S. Geol. Survey BidL 317, p. 30, 1907.

"Eldridge, G. H.: The Puente Hills Oil District, Southern California. U. S. Geol. Survey Bull. 309, p. 102.

M. Y.: Oil Fields of Southwestern Ontario. Canada Dept. Mines, Summary Reyt, 1918, part E, pp. 30-42, 1919.

*HuNTLET, L. H. : The Mexican Oil Fields. Am. Inst. Min. Eng. Bull. 105, p. 2092, 1915.

Db Golyer, E. L. : The Furbero Oil Field, Mexico, Am. Inst. Min. En. 105, pp. 1899-1911, 191$,

130 Geology Of Petroleum

strata later than Paleozoic, except in Derbyshire, England, where

oil has accumulated in a dome in rocks of

Paleozoic e. With this exception the oil-

. bearing strata are all of Mesozoic and of

a Tertiary age, much the greater part being of

cd the Tertiary.

In Alsace oil is found in lenses of sands

completely inclosed in marls, on monoclines,

I or sealed up the dip by marls coming to-

gether. Some of the lenses are faulted against

Ig impervious beds up the dip.

In the Boryslaw field, Gahcia, where the

-g petroliferous beds are found among strata

that are closely folded and faulted along

M overt rusts, the accumulations occur in

t anticlines and also in gentle synclines be-

Q tween them. The Tustanowlce field is on a

g I monocline. In the Opaka-Schodnica-Urcyz

field, in a block between two profound faults,

as shown by Zuber, oil is produced from anti-

clinea, synclines, and moDoclinea. In western

J'o Galicia, which includes the Potak, Rogi,

34 Rowne, Kroaus and other fields, the oil is

generally concentrated in domes and anti-

J clines.

"3 In Rumania the bulk of the output comes

from anticlines, salt domes, and monoclines

g sealed by faults.

'S In Baku, Russia, the oil is derived from

't anticlines and from monoclines on their

"S flanks. The principal structural features are

.2 probably domes or irregular closed folds and

S monoclinal lenses (Fig. 32.) In the Holy

I f Island and Cheleken fields oil is derived from

M quaquaversal uplifts. The Grozny field is on

S an anticline crossed by faults. The Maikop field is on a monochne sealed at an uncon-

formity.

In Burma the petroleum is derived from

anticlines, especially from the high places on their undulating

Structural Features Of Reservoirs 131

Seof hveJ ? ' Mife

Fig. 33. — Section of Dropright dome, Gushing field, Oklahoma. Vertical and horizontal scale are the same. Shows curvature of Pawhuska limestone from northwest comer of section 5, to northwest comer of section 27 T. 8. N., R. 7. E. {Data from Beal.)

Fig. 34. — Section of De Soto-Red River field, Louisiana. Vertical and horizontal scale are the same. Shows curvature of Nacotosh sand from northwest comer of section 14 to fault in section 23. T. 13 N. R. 11 W. {Data from Matson and Hopkins.)

Fig. 35. — Section of Thrall field, Texas. Vertical and horizontal scale are the same. Shows curvature of oil-bearing rock. {Data from Udden and Byhee.)

5ea/e\/e/

Fig. 36. — Section of Volcano anticline. West Virginia. Shows curvature of Washington coal bed from Straight Fork Creek through town of Volcano to Goose Greek. Vertical and horizontal scale are the same. {Data from Hennen, West Virginia GeoL Survey.)

in Wall Creek samn

jWe

Fig. 37. — Section of Salt Creek dome, Natrona County, Wyoming. Shows curvature of Wall Greek sand from southwest comer of section 27, T. 40 N. R. 79 W. to southwest comer of section 26, T. 40 N. R. 78 W. Vertical and horizontal scale are the same. {Data from Wegeman, 17. S, GeoL Survey,)

crests. The fields of Oceanica and Japan that have been described are on anticlines.

Geology Of Petroleum

FiQ. 38. — Sketch plan of Yenangyaung oil field, Burma. The heavy black line is the red bed at the base of the Irrawadian formation. {After raacoe.) For sections along AA', BB' and CC, see Fig. 39.

Structural Features Of Reservoirs 133

Amplitudes of Anticlinal Folds That Form Reservoirs. — The

domes and anticlines on which oil and gas accumulate differ much as to size and elevation. In Kansas, Oklahoma, and Texas productive fields are developed where the closure is less than twenty feet and the dips are as low as 30 feet to the mile. The anticline of the lola field of Kansas, according to Orton, rises 50 feet in 8 miles.* The closure in the steepest part of the Eldorado field, Kansas, is more than 100 feet, and in Augusta, Kansas, it is approximately the same. Many productive folds are larger. Fig. 33 is a section, true to scale, of the Gushing field, Oklahoma. Fig. 34 is a similar section, of the DeSoto-Red River field, Louisiana. Fig. 35 is a section of the Thrall field, Texas. A section of the Volcano anticline

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Red bod Red bed

Irrciwfffd/brn

Pegu

Fia. 39. — Sections through Yenangraung oil field, Burma, along lines A

BB' and CC in Fig. 38. (After Fascoe.)

of West Virginia is shown in Fig. 36, and one of the Salt Creek dome of Wyoming in Fig. 37.

Shapes of Anticlines That Form Reservoirs. — Some anticlines and domes that yield oil are fairly symmetrical — for example, the Yenangyaung dome of the IrrawadyRiver region of Burma (Figs. 38, 39) ; the anticline at Bibi-Eibat, Russia; and the Volcano dome, Ritchie County, West Virginia. Other domes are unsymmetrical— for example, the Grass Creek dome and the Salt Creek dome, Wyoming, and the Oil Springs dome, Ontario. The axial planes

Edward: €reological Structure of the lola Gas Field. Geol. Soc. America Buff., vol. 10, p. 104, 1911.

Y

/

134 Geology Of Petroleum

of some domes and anticlines are steeply overturned, as in the Yenangyat-Singu field, Burma; the Campina field, Rumania; the Boryslaw field, Galicia; and the Grozny field, in the Caucasus region (Fig. 40).

Oil and gas are found in overturned folds whose axial planes lie at low angles. In some of the California fields (Fig. 64, p. 155) the strata are so closely folded as to form isocUnes, and a well may penetrate the same formation twice. Such folds producing oil are apparently confined to fields that contain unconsolidated or partly consolidated beds. Deformation so intense in thoroughly consolidated rocks would generally result in scatterii the oil and gas.

Origin of Anticlines That Form Reservoirs. — Anticlines and domes in general {ire formed by compressive stresses operating on

Fia. 40. — Section of Grozny oil field, Russia. (_Afier Thompson.)

the earth's crust. Many of them are small mountain folds formed when the larger mountain axes were elevated. This is indicated by their positions on monoclines that dip away from mountain ranges. Some of the subordinate folds are 100 miles or more from the controlling major mountain axes.

Certain folds contain central cores of igneous or sedimentary rocks on which the sedimentary beds lie uneonformably. These cores were once hills. Their rocks were already compact, and in the compacting and settling of the overlying sediments, which were thicker away from the core, a gentle inchnation of the beds away from the core was developed. The beds were thus arched as if by folding, and their initial dip away from shore lines was

Structural Features Of Reservoirs 135

emphasized. Some investigators believe that the compacting of shales of varying thickness in Kansas fields has given rise to recognizable structural features.*

In the Tampico-Tuxpam field of Mexico the sedimentary rocks dip eastward at low angles. At many places igneous intnisives

Pio. 41. — Hypothetical section of a type of oil field, ftccording to Garfias. The Reservoir la intrusion that penetrated the series of Cretaceous hmestones and shales and only slisbtly disturbed the Cretaceous-Eocene shales. Black represents the fractured and porous material which constitutes the reservoir. It ia covered by an impervious cap.

have been thrust into the sediments, and reservoirs have formed near them. The intrusions probably cause a gentle doming of the

'Blackwblder, E. B : The Origin of Central Kansas Oil Domes. Amer. Asso. Petrol. Geologists, vol. 4, No. 1, pp. 89-94, 1920.

Geology Of Petroleum

rocks, sufficient to influence accumulation. The folding generally decreases toward the surface, where it is at many places difficultly recognized (Fig. 41). In the Ebano field, according to Garfias,* an igneous plug has domed the rocks it penetrates and on solidifying and sinking it has drawn the beds downward near its contact

Fig. 42. — Section of Spindletop oil field, Texas, a, rock salt; b, gypsum;

c, limestone. (After Lee Hager.)

with them. This has given rise to wha't he terms the anticlinal ring and fimnel structure. This structure is rare in other oil fields, although similar processes have operated in volcanic regions of the

western United States, in which the sedimentary rocks dip away from intrusive masses except near the contact, where for short distances they dip toward the intrusives.

Salt domes are structural domes that contain bodies of salt (Fig. 42). In some anticlines the lower rocks are thrust through the upper ones, complicating the structure by faulting (Fig. 43). Such is the case in Rumanian salt domes, where plugs of salt are

Garfias, V. R. : The Effects of Igneous Intrusions on the Accumulation of Oil in Northeastern Mexico. Jour, Geology, vol. 20, p. 666-672, 1912; The Oil Hegion ofNitf*neastem Mexico. Econ, Geology, vol. 10, pp. 195-224, 1915.

GarfasV. R., and Hawlet, H. J.: Funnel and Anticlinal Ring Structure Associated with Igneous Intrusions in the Mexican Oil Fields. Am. Inst. Min. Eng- Trans., vol. 67, pp. 1071-1082, 1917.

'Gabfias, V. R., op, cU, {Jour, Geology).

sss, Massci of rock salt

'Fig. 43. — Section of Baicoi oil field, Rumania. (A/ier Boiw&rih,)

Structural Features Of Reservoirs 137

thrust through clays and sands. The sands are sealed above by ! the central mass. The structure shown at the left in Fig. 43 is essentially a fault trap, but differs from monoclinal fault traps in its different arrangement of dips. Structure of this sort is probably developed where rd rocks alternating with unconsolidated weak rocks are deformed by strong pressure. Crystalline salt ia much more rigid than clay and sand. The thickness of the salt in some of the plugs is very great. In some places the salt beds are probably on edge. In the salt-dome fields of Texas and southern Louisiana the domes apparently occur along axes of deformation by folding and faulting.

Airangements of Anticlinal Folds That Form Reservoirs. — In acme regions oil lies in lines of pools that are elevated portions or

FiQ. 44. — Ideal sketch showing oil aceumulfttd principally on the lower anticline ortbe one on the bajinward side of the larger fold; the accumulation is greatest on the basinward limb of the anticline. represents oil and gas. ,

i nodes along anticlinal crests. On the Shoshone anticline, which least of the Wind River Mountains, Wyoming, four domes or elevated portions of the anticline yield oil or gas. Oil is found in several fields on high parts of the Coalinga anticline, California. Along the axes in the Yenangyaung and Yenangyat-Singu fields, in Burma, oil and gas have accumulated at several places where the crest of the anticlines are higher than elsewhere. In other regions the oil pools in domes or anticlines lie rudely in curved lines corresponding to axes of deformation. In still other places the pools are very irregularly distributed, owing doubtless either to deformation at two periods or to gentle deformation without much definition. As a rule the elevated crests that lie lower are more productive than the hher ones in the same series (Fig. 44). Thus in Oklahoma the Gushing field is more productive than the Barstow region, and the Glenn pool is more productive than the region about Muskogee. In the region near Red River, southern Oklahoma, the oil fields are grouped near the outer border

138 Geology Of Petroleum

of the Permian rocks, which dip southwestward along Red Biver and rise again south of the river, forming a deep salient or embayment. The Healdton dome, which is a basinward fold, is more productive than those which are higher up, including the Fox, Graham, and others. This relation is clearly shown in the Big Horn Basin, Wyoming (p. 400), where, as stated by Hewett and Lupton, the more productive anticlines are those which lie basinward. In this basin there are two circles of anticlines, of which the inner is much more highly productive than the outer. Tlius the Elk Basin, Byron, Greybull, Torchlight, and Bonanza domes are more productive than the Lovell, Spence, Midnight, Tensleep, and Bud Kimball, which yield a little oil or are barren. On the west side of the basin the Warm Springs, Grass Creek, Little Buffalo, Oregon Basin, and Cody anticlines are more productive than the Rawhide, Gooseberry, Wagonhoimd, and Hamilton. The oil evidently migrated upward from the basin into the elevated portions, and the gathering groimd on the basinward side is much greater than on the side toward the moimtains. Moreover, in the outer circle of anticlines, the groimd water doubtless has entered and in some places washed the beds clean of any oil they may have once possessed. Evidence of this Ues not only in oil springs, but also in the fact that some of the folds carry, below the oil, water that is not highly saline compared with waters of other fields.

A small dome near the center of a basin obviously has a small gathering ground and should not be expected to contain a large deposit.

Segregation of Oil on Basinward Sides of Folds. — In many fields the portion of the oil sand that carries oil and gas is not symmetrical with respect to the fold. As a rule it descends farther down the fiank of the gentle limb than it does down the steep flank. This is noteworthy in the Yenangyat-Singu field of Burma, where on a long, sharp unsymmetrical anticline (p. 556) practically all the wells are west of the crest of the fold, on its gentler flank. In the Big Horn basin, Wyoming, the basinward flank almost invariably has the greater accumulation. In the Salt Creek field (in the first Wall Creek sand) the oil blanket extends deeper on the northeast side of the dome, which has a greater gathering ground. In the Cushing pool the accumulation is greater on the basinward side, and some of the sands that yield oil on the west side of the dome yield gas only on the east side. These observations show, that in

Structural Features Of Reservoirs 139

many folds the gravitational separation is not perfect. BeaP suggests that the gas accumulates first and banks up near the crest of the fold and prevents the oil that collects on the side whete the gathering ground is greatest from passing over to the opposite side. In steep symmetrical domes, containing sands that are everywhere pemieable, the contact between oil and water would normally be flat. / If higher at one point than another, the water would descend by gravity and push the oil up where it is lowest. At many places however, where gravitational separation is clearly indicated by the position of the accimaulation with respect to the structure, the contact between the water and the oil is not level. This condition may be due to tightness of the sands in places, which prohibits free circulation of oil around the dome on nearly level lines. The maximimi accumulations of oil on the domes of Osage County, Oklahoma, are, according to Mason, on the north and northwest sides of the domes. The maximimi accumulations of oil and gas, however, are not all on the long limbs of the folds. In the Caddo and Crichton fields, Louisiana, according to Crider,* in certain areas short Umbs are most productive.

In the Cushing field, Oklahoma, in the Layton and Wheeler sands, the contact is gently incUned in the direction of the dip of the strata. This attitude may be due in part to differences in porosity or to differences in the size of the pores in the reservoir rocks.

Reservoirs In Monoclinbs

A considerable number of the world's oil and gas fields lie on monoclines that are sealed in various ways. Monoclines may be sealed where impervious rocks meet above the reservoir rock (Fig. 45), at impervious fault planes or where faults throw impervious rocks against the reservoir rocks (Fig. 46), where the sands become impervious by cementation of their interstices or where the interstices were filled with clay particles when the sands were deposited

*Beal, C. H. : Geologic Structure in the Cushing Oil and Gas Field, Oklahoma, and Its Relation to Oil, Gas, and Water. U. S. Geol. Survey BvU. 658, p. 44, 1917.

*Mason, S. L.: a Statistical Investigation of the Effects of StructiureUpon Oil and Gas Production in the Osage. Amer. Assoc, of Petrol. Geologists, vol. 3, pp. 407-417, 1919.

"Crider, a. F. : Oil and Gas Possibilities in Mississippi. BvlL of the Southwestern Assoc, of Petrol. Geologists, vol. 1, pp. 152-165, 1917.

Geology Of Petroleum

(Fig. 47), or where the oil itself at or near the surface, on drying hardens to form asphalt (Fig. 48). A few oil fields are formed where a tilted eroded petroliferous series is covered unconf ormably by a later series. ' If permeable strata such as conglomerates and

Fig. 45. — Sketch showing reservoir sealed by impervious rocks overlying and underlying the reservoir rock and joining above the reservoir.

sandstones are laid down upon the petroliferous strata, the beds of the later series may carry oil. If muds or clays cover the petroliferous bed, gas, oil, and water will probably be segregated in the lower bed. Reservoirs are found at unconformities in many fields. In the Maikop field, on the north flank of the Caucasus, Russia,

Fig. 46. — Sketch showing reservoir sealed by fault bringing oil sand against

impervious rocks.

oil has accumulated in a sand that was deposited upon an older hilly surface and in turn covered by a impervious bed so that it is effectively sealed (Fig. 57, p. 150) . In the Tampico-Tuxpam field, Vera Cruz, Mexico, petroliferous beds are sealed by igneous intrus-

FiG. 47. — Sketch showing reservoir sealed by tight sand. Black is oil and gas.

ives that cut across the beds. It is obvious that monoclines sealed by impervious rocks joining above the reservoir rock and monoclines sealed by local cementation and at unconformities are discovered with greater difficulty than monoclines sealed by other

Structural Features Of Reservoirs 141

Fio. 46. — Stereogram showing reservoir sealed by asphalt forming in oil sand near the surfaoe, Sunset-Midwajr field, California- (A/ter Fade, U, S- Geot, Svniej/.)

Geology Of Petroleum

processes. Oil pools in such positions are discovered, more often than otherwise, by "wildcat'' drilling or by wells sunk for water.

Monoclines Sealed By Overlying and Underljring Clays or Shales Joining Above Reservoirs. — Monoclines sealed by clays or shales are found at many places. In the Appalachian geosyncline, which includes many of the great oil pools of the United States, the

au Of Mikcs

0 10 ao M 40 90

I.I I I 1 1 i

—

Fig. 49. — Map showing location of "Clinton" gas field, Ohio. {After

Bownocker.)

sands generally thin out toward the west. The land mass that supplied the sediments during Paleozoic time was southeast of the oil field. At the end of the Paleozoic era the strata were folded and the great Appalachian geosyncline was formed. Pallel to the axis of the geosyncline there are many subordinate folds. Where the porous strata rise west of an axis of such a fold or west

o

Structural Features Of Reservoirs 143

of the axis of the great geosyncline, accumulations of oil and gas are likely to be found. In eastern Ohio (Fig. 49), where the *'Clinton" sand thins out up the dip, the shales above and below it come together. The upper part of this sand contains gas xmder great pressure. From Cleveland southward to Jackson County, a distance of 170 miles, wells producing gas are simk to this reservoir at many places. The general relations in the Appalachian field are illustrated by Fig. 50.

In Eastern Ohio oil and gas are found in the Berea sand, near the lower part of the Mississippian. The Sunbury shales lie above the Berea, and the Bedford shales below it. The Berea yields oil or gas in many coimties.

Approximately along the area indicated by the line X' Y in Fig. 51, there is, according to Panyity, a noteworthy change in the character of the sedimentary rocks. East of the line and parallel to it, where the sand is thin and lenticular, the most productive fields are found. These include the fields of Barnesville, Temperanceville, Summerfield, Macksburg, Dudley, and others. East of the gas fields, down the dip, are the most productive Berea oil pools. In places where anticlinal structure is present the positions of

'PANYmr, L. S. : Lithology of the Berea Sand in Southeastern Ohio and Its j:ffect on Production. Am. Inst. Min. Eng. BvU. 140, pp. 1317-1320, 1917.

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So

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fl o

is

So

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&

a

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d

Geology Of Petroleum

the gas, the oil, and the water are in accord with the structural theory (Fig. 52). The controlling factor in most of these pools, however, is, according to Panyity, the western limit of the sand. West of the line X- Y there is a water-bearing sand. Near Byesville small gas pools are developed on minor uplifts above the water. The only field of any considerable size developed west of the line is the Corning pool.

Fig. 51. — Sketch map showing position of certain oil pools in Berea sand in southeastern Ohio. Oil is found m sealed monocline east of line X-Y, {After Panyity.) For section along AB and CD see Fig. 52.

Monoclines Sealed By Faults. — Some faults afford channels along which fluids escape. Other faults are accompanied by finely ground clay that seals the opening, making the fault impervious. Faults that cross shaly strata or other soft rocks are generally impervious. Some oil pools are on monoclines sealed up the dip by faults. In the Appalachian fields no monoclines of this character have been described, nor have they been recognized in western Ohio, Indiana, or Illinois. In Kentucky the Irvine field is developed along a faulted anticline, but at most places the reservoir has been sealed by folding, or by folding and faulting together. (See Fig. 106, p. 241.) In QkloJioma, southeast of Gushing and §Quth*

Structural Features Of Reservoirs 145

west of the Glenn pool, oil has accumulated, probably in places where faults sealed the petroliferous sands above, but the details of the structure in this area have not been made public. Where a plunging anticline is faulted across the strike a 'fault trap*' is formed. In Wyoming part of the oil produced in the Big Muddy field was obtained on an anticline plunging away from a fault. In

f

5unbury shah

Shah "break" BarQa (pay sand)

Beolfard shalQs

Js'

30'

Zo' 3S'

Oil Wafer

(C)

Fig. 52. — Sketch showing (a) section of Berea sand and adiacent strata; (6) reservoir in Berea sand on monocline (Hne CDy Fig. 51) and (c) reservoir in Berea sand on monocline and gas in anticline (on line AB, Fig. 51.) All in southeastern Ohio. {After Panyity.)

the Los Angeles field, California, a fault has apparently sealed a petroliferous stratum (Fig. 184, p. 464). At Binagadi, Russia, the reservoir rocks are faulted (Fig. 53). Where faults bring permeable sands into juxtaposition, the seal is less likely to prove effective, as is shown by Fig. 54.

Geology Of Petroleum

Monoclines Sealed By Local Cementation of ttie Resenroir Rock. — Oil migrates up the dip. If it reaches a place where the reservoir rock ie impervious it will halt. The reservoir stratum may be made impervious by deposits of clay, calcite, iron oxide, or carbonate in the interstices between the grains. Some petrolif-

Fig. 53, — Section of Binagadi oil field, Russia. 6, Freshwater beds, Miocene; e, Lower Miocene; s, Spiralis beds. (_After Thompson.)

erous strata are impervious at places where clay was deposited when the strata were laid down. Whatever the cause, the impervious portion of the stratum will delay or stop migration and cause

Fia. 54. — Diagrammatic cross-section showing (at A) an accumulation of oil and gas caused by a fault and (at B) a possible condition under which a fault may not seal a reservoir. {AfUr-Falh.)

an accumulation. The famous Glenn pool, in Oklahoma, is on a

fluted monocline, and the accumulation of oil is believed to be due

in part to changes in the character of the sands above the oil pool.

Monoclines Sealed By Asphalt. — Some reservoirs on monoclines

Structural Features Of Reservoirs 147

are sealed above by tarry products that have resulted from hardening of materials in the oil (Fig. 55). Reservoirs containing the heavier asphaltic oils are more generally sealed in this maimer than reservoirs containing the lighter paraffin oils, although vents leading from reservoirs are known to contain both the asphaltic and the parafhn bitumens. This subject is treated in connection with a discussion of bituminous dikes (pp. 29 to 32). It is generally supposed that the tarry products result from partial oxidation of the oil or from reaction of the oil with ground water or from loss of gases and the lighter liquids by partial evaporation. At some places bituminous solids have formed at depths from 1,000 to 2,000 feet below the surface and it appears improbable that atmospheric

oxygen, under the conditions, should be effective at such great depths.

The best known fields of which the reservoir rocks are sealed by bitumens are the Coalinga field and the Sunset-Midway field of California. In both of these fields highly productive reservoirs are sealed by tar plugs. In the Sunset-Midway district ' the reservoirs containing the oil are sealed up by tarry oil or tar which is formed by the interaction of the mineralized waters and the hydrocarbons that compose the oil. It is a reaction which results in the

P*CK, R, W.: The Sunset-Midway Oil Field, California. U. S. Geol. Survey Pro/. Paper 116, p. 87, 1920.

Geology Of Petroleum

recMction of sulphate water to form sulphides and the addition of tihpEulphur or sulphides to the oil.

jcording to Pack 2, the reactions that result in the formation of tarry products may be divided into two classes, one that takes place near the surface; another at greater depth, in many places at the very base of the oil zone, below the beds containing the productive oil sands.

The reactions that take place close to the surface, particularly along the outcrop of the oil-bearing beds, result in sealing up the outcrop and preventing the escape of the oil. The extent to which the oil undergoes alteration is evidently far greater near the surface than it is at depth, for the deposits of tar and of sulphur are greater

Fig. 56A. — Sketch of section showing oil and gas (black) in porous deposits that rest unconf ormably on a tilted series of oil sands and carbonaceous shales.

Fig. 56B. — Sketch of section showing accumulation of oil and gas above water in a tilted bed overlain unconformably by an impervious bed.

there. The surface water characteristically contains more sulphates than the waters at greater depth, and the oxidation of the oil is aided to a large extent by other oxidized products in the rocks that lie close to the surface, or by exposure to the air itself. Not only are the oils at or near the surface changed more or less completely to tar, but the sulphate waters are changed so completely that great quantities of free sulphur are formed, and deposits of native sulphur such as the one occurring south of Old Sunset result. Sulphur is widely scattered along the foothills in which the oil sands crop out.

Rogers, G. S. : Chemical Relations of tht Oil-Field Waters in San Joaquin Valley, California (preliminary report). U. S. Geol. Survey Bull. 653, 119 pp., 1917.

*0p. cit., p. 88.

Structural Features Of Reservoirs 149

In the Midway region, according to Pack, There is clear evidence that oil has been hardened by surface water to depths 800 or 1,000 feet. The effect of the deeper waters on the oil is not so extensive as that of the surface waters, but it is evident none the less, for at many places where water is found in the oil sand a deposit of tar or heavy oil separates the portion of the sand occupied by oil from that occupied by water. The reason for the lesser effect of the deeper waters and thus for the smaller amounts of tar in the deeper sands is evidently the fact that the waters in the deeper sands contain normally a far smaller amount of sulphate than the surface waters.

Monoclines Sealed at Unconformities. — At many places tilted beds are covered by relatively flat-lying beds. Unconformities are favorable places for accimiulation, because the younger deposits commonly include coarse sandstone or conglomerate near the base (Fig. 56A). Some monoclines, it is said, are sealed by impervious beds that cover the tilted beds by overlapping them (Fig. 56B).

If the underlying older strata contain sands or other porous rocks covered by shales and the sands become saturated with petroleum and water the petroleum will rise toward the smface and be halted or diverted when it reaches the impervious cover. The line or zone of junction is rarely level, and accumulation is imequal at different places where the porous bed is covered. If the junction is sealed at the high end by warping or at a place where the reservoir rock is tight, a trap is formed in which the oil or gas or both may find lodgment.

In Brenning Basin, in the Douglas oil and gas field, near Douglas, Wyoming, the nearly flat White River (Tertiary) beds rest on tilted Cretaceous strata that include nearly all the beds of the Colorado and Montana groups (Cretaceous), which are productive elsewhere in Wyoming. Barnett* states that the petroleum in migrating upward along bedding planes and through porous sandstone finds a barrier when it reaches the White River formation, so that oil and gas accumulate near the contact. They penetrate the White River beds only where they encounter porous material or fault planes.

0p. cU,, p. 88.

*Baknbtt, V. F. : The Douglas Oil and Gas Field, Converse County, Wyoming. U. S. Geol. Survey BuU. 541, p. 69, 1914.

Geology Of Petroleum

The structural conditions are somewhat similar in the Healdtonl

pool, south of the Arbuckle Mountains, Oklahoma, where Pennsyl-

vanian strata rest on steeply tilted Ordovician beds.' A little of

the Healdton oil was probably originally in the Ordovician beds,

where they are covered by the Penn-

sylvanian shales. The principal part

of the output, however, is derived

from Penneylvanian rocks.

In the Madill pool, Oklahoma,

just south of the Arbuckle uplift,

folded Paleozoic sediments dip at

g. at high angles. Above them are Cre-

tuaoaiutat J taceous rocks that lie nearly fiat.

t- The lowest member of the Cre-

taceoua, the Trinity sand and

gravel, is saturated with oil that is

probably derived from the under-

3 lying Carboniferous strata,* which

are highly productive in this region,

In the McKittrick-Midway-Sun-

set region, California, the Monterey

(lower Miocene) and Santa Marga-

rita formations, which lie in a Con-

S formable series, are tilted, and the

° McKittrick (upper Miocene) over-

lies them unconformably. ' The

J oil is believed to have originated in

[ the diatomaceous shales of the

Monterey and to have migrated to

the sandy layers in the Monterey or

to the sands and gravels of the un-

FowERS, Sidney: The Healdton Oil

Field, Oklahoma. Eom. GeoUigy, vol. 12,

pp. 594-606, 1917.

. =Taff, J. A., and Reed, W. H.: The

Madill Oil Pool. -Oklahoma. U. S. Geol.

Survey Bull. 381, pp. 504-513, 1910.

Hutchinson, L. L.: Rock Asphall, Asphaltite, Petroleum, and Natural Gas

inOyahoma. Oklahoma Geol. Survey BmH. 2, p. 252, 1911.

'ARNor.D, Ralph, an A Garfiah, V. R. : and TcehnoloRy o( the California Oil Fitlds, Am. Inst. Min. Enn;. Bull. 87, pp. 383-470, 1*14;

Structural Features Of Reservoirs 151

conformably overlying McKittrick formation. With a few exceptions the productive sands of the region are at the base of the McKittrick, above the unconformity.

In the districts mentioned above oil has originated in the older series, below the unconformity, and has accumulated in the older series where it is sealed in or has passed into the porous beds of the younger series. Examples are known, however, where the oil has originated in the younger series and has accumulated in sandy beds of that aeries where they rest upon an old erosion surface that existed before the reservoir rocks were formed and where the reservoir rocks are sealed above by overlapping impervious rocks. The best known example is the Maikop field (Fig. 57), on the north side of the Caucasus Mountains, about 300 miles west of Grozny, Russia. Here Tertiary beds dip away from an erosion surface of Cretaceous rocks. The oO is accumulated in Tertiary sands, which are covered by later impervious beds, and in places it rises to the contact of the sands with the Cretaceous, as is shown in Fig. 57. The overlying beds extend farther over the ancient surface of the Cretaceous rocks, overlapping the petroliferous sands. As shown

in the sketch by Thompson,' the significant structural feature is not the fold in the Cretaceous rocks but the steep eroded surface of the Cretaceous, which is progressively overlapped by the Tertiary strata.

In Ontario, in Quebec, and probably also in northern New York, according to F. G. Clapp,* gas is found in based sandstones overlying crystalline rocks (Fig. 58). The structure of these beds has not been described in detail. The accumulations are probably due to the larger openings in coarser material near the base of the formation.

'Thompson, A. B.: The Rdation of Structure and to the Occurrence of Petroleum. Inst. Min. sndMet Trans., vol. 20, p. 258, 1911.

Trench, B. H. r Discussion of Thompson's Paper. Idem, p. 247.

'Clapp, F. G.: a Proposed Classification of Petroleum and {Natural Gas Fields, Based on Structure. Earn. Geology, vol. 5, p. 519, 1910.

Cloyi,n

Geology Of Petroleum

Monoclines Sealed By Igneous Intrusions. — In the Tampico- Tuxpam region, Mexico, oil accumulations are found in areas where

Fio. 60. — Hypothetical section, according to Garfias, illustrating basalt intruding the oil series of Mexico and reaching the surface. Btaelt represents the places that are favorable for oil accumulation. The plug is larger near the burtuce, where expansion is easier, owing to lighter load.

Structural Features Of Reservoirs 153

dikes or other igneous bodies cut across the petroliferous beds. As a rule the iDtnision appears to have been attended by uplifting of the strata into domes. Clapp described an occurrence where the strata are uplifted on both sides of a plug (Fig. 59). In an example illustrated by GarSas (Fig. 60) there is practically no doming of the strata.

Reservoirs In Flat-Lying Beds

Aclines. — Aclines are bodies of rock that lie essentially flat. In such rocks large accumulations of nil are rare. The Rivadavia field, Argentina, is on a broad monocline that dips east. The rocks are so nearly fiat that the field has been regarded as aclinal.

Fia. 61. — Ideal section of Gaines Pool, Pennsylvania, showing its retatioa to supposed change of depth. A, oil sand; B, brink of terrace where oil is supposed to have accumulated. {After Fuller.)

Fia. 62. — Ideal section showing position of oil accumulation on a trace. If the oil migrates upward aa it does in saturated rocks, it will accumulate near A. If it migrates downward it will accumulate near B,

Recently, however, it has been shown that the oil has accumulated in very shallow domes. (See p. 592.) In the New Plymouth field, New Zealand, no elevated structural features are

Terraces. — There is apparently a lower limit of inclination beyond which petroleum will not migrate up the dip. This hmit depends on the size of the openings, gas pressure, and the viscosity of the oil. Where there is a change from a dip up which oil will move to one up which oil will not move an accumulation is likely to take place (Fig. 61). If salt water is associated with the oil and

'Clapp, P. G. : Revision of the Structural Classification of Petroleum and Natural Gas. Geol. Soc. America Bull., vol. 28, p. 572, 1917.

Geology Of Petroleum

the movement is the dip the accumulation will be near the axis of iBexure, where the dip changes, . .nd in general the greatest accumulation will be near the lower edge of the terrace (Fig. 62). Such conditions exist in the Peru field, in southern Kansas. On the other hand, if little water is associated with the oil it tends to move downward, and accumulation may take place on the upper part of the flat limb of the terrace. These relations have been shown by experiments at the University of Minnesota (see p. 112).

tarrcf a

, Oil sand satvroiteef

] Pry oil sane/ Oil accumuloitian Oas etccumulorHom

Fig. 63. — Ideal sketch showing accumulation of oil and gas in Appalachian region. The higher sands are saturated and oil and gas rises to crests of anticlines. The lower sands are not saturated and the oil and gas is found low on the flanks of the anticlines or in synclines. {After Griswold and Munn.)

Reservoirs In Synclines

Oil is found in synclines in parts of the Appalachian region. In the Catskill strata in- Pennsylvania and West Virginia petroleum and gas are found in sands between shales. These beds are not saturated with water. Reeves states that these imsatiu'ated beds, which are land sediments, had dried out before they were submerged in the sea and that the spaces of their reservoirs were filled with air. Later when marine sediments were laid down above them, the oil evidently migrated into them, but not enough water to float the oil to the tops of folds. Some of the Mississippian sands above the Devonian in Pennsylvania are saturated, and in

Reeves, Frank: The Absence of Water in Certain Sandstones of the Appalachian Oil Fields. Econ. Geology vol. 12, pp. 254-278 1917.

Structural Features Of Reservoirs 156

them the oil and gas occur in anticUnes. These features are illustrated by Fig. 63.

At Urado, Colorado, in the Uinta Basin, near the Colorado line, oil has been produced from a tunnel driven in a flat-lying sand, the base of which is warped to form gentle sags in which the oil collects. Small amounts of oil have been obtained also near De Beque, in western Colorado, from wells sunk near the axis of a low minor anticline which is developed in a broad syncline. In southeastern Utah a little oil has been found in a syncline in the San Juan field. IntheMc- Kittrick district, California, a considerable concentration of oil is found in an overturned syncline (Fig. 64). In Galicia also oil is found in synclines in the Boryslaw field.

The large deposits of oil in well-defined synclines in consolidated rocks are in the Appalachian field. Most other fields in which large concentrations are found in synclines are in unconsoli-

u

a

o

S

a

Co

Os

§

o

o

a

W

Geology Of Petroleum

dated rocks that have been intensely deformed. Under such conditions as have akeady been noted, petroleum is apparently found in many different structural positions.

Some synclines are merely gentle sags near the crests of anticlines. Such sags may be saturated with oil or gas or both (Fig. 65). Others contain a little water near the axis of the sag.. In still others the sand may be filled with water.

Reservoirs Formed By Fissures

Practically all consolidated rocks are jointed, and many of them are appreciably fractured. The earlier investigators of oil reser-

-soo

"Vioo

.Oil and gas

Fig. 65. — Section of Gushing field, Oklahoma, showing ovl in a synclinal sag

near the crest of an anticline. {After Beal.)

voirs in the Appalachian region laid much emphasis on fissures as containers of oil and gas. Later, when great fields in unconsolidated rocks were developed in Russia, in California, and elsewhere it appeared less probable that fissures play so important a part, for in soft rocks fissures will close. - The effect of openings formed by solution, dolomitization, fracturing, and brecciation has been mentioned in connection with the discussion of reservoir rocks. Such openings doubtless add materially to the capacity of reservoirs in certain fields where oil occurs in Paleozoic rocks. In the unconsolidated rocks of some Tertiary fields they are generally less effective. The capacity of fissures is attested by those that are filled with bitumens — some containing many millions of tons. In some fields oil is recovered from fissures in shale.

Lauer, a. W.: Petrology of Reservoir Rocks and Its Influence on the Accumulation of Petroleum. Econ, Geology j vol. 12, pp. 435-465, 1917.

Lewis, J. O. : (Discussion of Lauer's Paper). Iderriy vol. 13, pp. 65-69, 1918.

Structural Features Of Reservoirs 157

At Florence, Colorado, according to Washburne, the principal reservoirs are fissures in the shale of the Pierre formation. This is a uniform shale, and in the lower part, which carries the petrolemn deposits, no sands are present. The fissured area is in a great synclinal basin, the Canyon City embayment, and the fissures are associated with small flexures and faults. The oil is not all floated on water, although some salt water appears in some of the deeper wells. The oil is associated with gas under pressure, and some of the wells are exploited for gas alone. The oil does not follow any bed or series of beds in the shale. As shown by the outcrop, the oil zone does not contain any sandstones or other porous beds capable of forming reservoirs. Evidence that the oil lies in joints and fissures consists (a) of a correspondence in direction of the major joints in the rocks at the surface with the alinement of wells which have interfered with one another; (b) of the fact that many wells have been drilled within a few feet of one another without encountering oil at the same depth; (c) of the fact that gas struck in a shallow well often immediately ruins an adjacent well several hundred feet deeper by tapping the source of pressure; (d) of the fact that many wells drain adjacent wells that are shallower; (c) of the indication of vertical connection between the oil bodies shown by the marked increase in maximum pressure with depth; and (/) of the dissimilar pressures in adjacent wells of the same depth.

In the Salt Creek field, Wyoming, considerable oil has been found in fissures in the Cretaceous shale. This region is a domatic uplift and yields oil of good grade from the Wall Creek sands of the Frontier formation. The oil in the sands is found in elevated portions of the dome. West of the dome there-is a great syncline with thick shale beds in which the oil sands carry only water. In nearly every well drilled in this field, according to Wegemann, some oil is found in the shale, a few wells having an initial production of as much as 1,500 barrels a day. The oil is not obtained from porous beds in the shale, and it is found in adjoining wells at different depths. The shale is so fine grained that it would not in itself constitute a reservoir for oil, as the openings between the

Washburne, C. W.: The Florence Oil Field, Colorado. U. S. Geol. Survey Bull. 381, pp. 517-544, 1910.

Wegeb4ANN, C. H.: The Salt Creek Oil Field, Wyoming. U. S. Geol. Survey BvU, 670, p. 36, 1917.

158 Geology Of Petroleum

particles are too small to permit oil to flow rapidly through them. The oil from the Wall Creek sand and the oil from shale are practically identical, the only difference being that the oil from the sand contains a Uttle more gas.

The shale wells start flowing under considerable pressure, and fragments of calcite are often ejected from the wells. The calcite is like that which fills or partly fills the fissures in the shale. Presumably the oil is derived from the Wall Creek sand below. Certain of the faults in the shale extend down to the sand and afford passages through which the oil in the sand, under great pressure, has been forced upward into the shale. As the fissures in the shale are not confined to the dome itself but extend into the adjoining syncline on the west, oil has been forced laterally through the fissures into the shale of the syncline. The Wall Creek sand, wherever it has been reached in this synclinal area, has produced water.

Shales that yield oil also yield gas. In some regions gas only is obtained from the shale reservoirs. In Cleveland, Ohio, and in the surrounding country wells have been sunk in the shale for domestic supply. As a rule the pressure is low and the yield small, but the wells have long life, so that farmers find the fuel suitable for domestic use. Some wells supply one or two farm houses.

Orton,2 describing the differences between shale gas and "reservoir gas/' notes that:

Shale-gas wells are generally of small volume, compared to wells deriving their gas from sand reservoirs. Moreover they lack uniformity of rock pressure. Wells drilled in close proximity and to the same depth may have very different pressures. In sand reservoirs, pressures are generally greater and more nearly uniform. In the wells yielding shale gas there is no definite horizon from which their gas supply is derived. The stratum that yields it may be several hundred feet thick, and gas is likely to be found at any point in the descent. Shale-gas wells, though in the same field, may be expected to show a considerable range in depth. Some shale-gas wells occur independently of oil production. Gas may be abundant, while petroleum is altogether wanting. Shale-gas

*Van Horn, F. R. : Reservoir Gas and Oil in the Vicinity of Cleveland, Ohio. Amer. Inst. Min. Eng. Bull 121, pp. 75-86, 1917.

*Orton, Edward: Geological survey of the Tola Gas Field. Geol. Soc. America BulLf vol. 10, p. 100, 1899,

Structural Features Of Reservoirs 159

wells are long lived. Weak flows are maintained for long periods. Shale gas is not dependent on the structural arrangement of the rocks which contain it. If it is not associated with oil or water, it can not be displaced nor crowded out by them.

Accumulation In Sands Of Irregular Pore Space

In many oil fields the oil-producing sands are irregular or ''spotted." Borings that yield neither oil, gas nor water may be

Fig. 66. — Sketch contour map showing accumulations of oil and gas in

sands that are only locally pervious.

sunk in a sand that contains oil or gas on all sides of it. Examination of fragments of the oil stratum in the boring may discover a tight sand in which the pore space is filled by calcite, pjrrite or other secondary minerals, or one that is filled with clay. On many domes and anticUnes, as already noted, a belt that

Geology Of Petroleum

yields oil is found below a disk of gas-filled sand. Some wells, however, that are sunk in the oil-producing belt may yield gas only. Examination may reveal a sand that is coarser grained and contains larger pores than the sands elsewhere in the oil-bearing area, for in some fields, gas tends to accumulate in the larger openings. Irregular and fantastic patterns of areas of production are displayed in pools containing ''spotted*' sands. Nevertheless, in the areas of porous rock that are surrounded by impervious rocks at the same horizon, the oil, gas, and water that are concontained in the porous rock are generally segregated in belts, the gas above the oil and the water below it, as is illustrated by Fig. 66. In such a field where pools are not connected by open spaces

Fig. 67. — Ideal sketch through a dome, showing accumulations of oil and gas in sand-filled channels, and directions of migration. (After Wallace Lee.)

in the petroliferous stratum the lines of contact between gas and oil and between oil and water may be found at widely different elevations.

Accumulations At Unconformities

Unconformities are favorable places for the acciunulation of oil and gas because the material laid down first along an advancing shore line is generally coarse. The strata formed at the bottom of a sedimentary series generally contain conglomerate and coarse sand. As a rule, such material has been washed over by waves and the fine clay has been removed from it. Thus the basal beds are likely to contain many large openings suitable for the accumulation of oil and gas. At some unconformities the surface on which the upper series was laid down is irregular, and the porous beds are likely to be distributed as small lenses. Thus the reservoirs formed by such rocks will be spotted. When such a reservoir is

Structural Features Of Reservoirs 161

thrown into folds the oil and gas will accumulate at the crests of the folds where the lenses of porous rock lie at the crests and in the Upper parts of the lenses that lie on the flanks of the folds (Fig. 67). In the Colmar district, IlUnois, oil and gas are found in the Hoing sand, at the base of the Niagara, which lies unconformably on the Maquoketa shale at places where it is locally developed.

Among the examples of reservoirs at unconformities are those of the McKittrick-Sunset district, California, were large accumulations are foundatthebaseof theMcKittrickbeds,whichoverlie older rocks unconformably. In the Coalinga district, California, oil-bearing beds are found at three unconformities. Some other examples of accumulation at unconformities are mentioned odl

pages 149-151.

Successions Of Petroliferous Strata

Oil reservoirs are almost invariably related to geologic structure* There is no better proof of this relation than the accimiulation of oil in different beds, one below the other, in the same field, and the absence of oil in commercial accumulations in the surroimding regions.

In many pools oil is found in more than one stratum. In some it is found in five strata or more. Where the structure is anticlinal and there is an accumulation of petroleum in the upper sand at the crest, it is reasonable to suppose that lower strata, if conformable, he in anticlines also, and that if they are porous they may contain additional reserves. In some districts the amplitude of folds increases with depth, and deeper accumulations, situated on the greater folds, are more productive than the shallow pools. Many fields have been revived again and again by deeper drilling.

Where petroliferous beds are steeply folded, as they are in the Grozny field, north of the Caucasus Range, Russia; in the Yenangyat-Singu field, Burma; and in other fields that contain accumulations of oil in Mesozoic and Tertiary rocks, where successive oil strata have been discovered, the planes that pass through the crests of folds or the ''crest loci," are not vertical but dip at high angles. In general, if not invariably, the crest locus will dip toward the gentle limb of an asymmetric fold, and accumulation on the gentle side of the fold as shown at or near the surface will be even more pronounced in depth.

In oil fields on monoclines regular successions of petroliferous

162 Geology Of Petroleum

strata are less likely to be discovered than on domes. Nevertheless, such series have been found at many places. Even some monoclinal traps that are formed by the porous sands tightening up the dip, either by changing to clayey strata or by cementation of porous sands, have been found to contain several accumulations, one below another. Sands wedge out away from shore lines, and many sands, one below another, may be related to the same shore line. Faults that bring impervious strata against sands and thus seal reservoirs may cross a series of sands providing conditions for accumulation at several horizons. Dikes or other intrusive bodies that seal one member of a petroliferous series are likely to seal others.

In oil fields on terraces more than one petroliferous bed may be found. Obviously, if the rate of dip changes in the higher beds, it will generally change also in the lower beds.

Distances Covered In The Migration Of Petroleum

In some regions there is evidence that petroleum has migrated considerable distances. / In Wyoming, where the dips are high, essentially all the petroleum recovered is found in small sharp domes or other uplifts. The gathering grounds are very large compared with the areas of accumulation. I'Some of the oil has probably moved several miles, perhaps a score of miles or more, to accumulate in the high structural positions. In this and other regions the contact with the salt water that lies below the oil — that is, the "edge water" — is not a level line but descends to lower levels on the side toward which the gathering ground is greatest. In the Salt Creek dome the base of the conical oil blanket descends about 100 feet on the northeast side, toward the great syncline that lies between the Big Horn Mountains and the Black Hills. In the Gushing field, Oklahoma, the oil descends to greater depths down the west side of the dome, which hes toward the basin, than it does on the east. In Lambton County, Ontario, there are noteworthy descents of the oil-saturated rocks of each of the great pools, and accumulations are greatest toward the areas where the gathering ground is greatest. On the Volcano anticline. West Virginia, the accumulation is concentrated on the west side of th axis. In these and many other regions the positions of the most productive sides of the domes with respect to the greatest gathering areas indicate clearly that migration of petro-

Structural Features Of Reservoirs 163

leura has been greatest where the area from which supplies could have come is greatest.

In many regions minor anticlines or domes are found one below another down the dip on great monoclines that slope away from mountain upUfts. The greatest accumulations are commonly on the lower folds — that is, on those that lie on the basinward side — which in general have greater gathering grounds than folds higher on the monocline. These relations are clearly shown in the Big Horn Basin, Wyoming, and at many other places.

Some accumulations are so great that the inference is warranted that they are drawn from large areas. In the famous Baku oil field of Russia accumulations that cover small areas are very large. More than one-tenth of the world's production of petroleum has been derived from an area of less than 3,000 acres in the Balakhany-Sabunchy-Romany field. It is improbable that such large accumulations could form only from strata near them. The oil doubtless has moved great distances to collect in the structurally favorable areas. ;

These observations tend to confirm the conclusion that oil has migrated considerable distances in some districts. , In northeastern Oklahoma, where the domes and anticlines are flat and closely spaced and saturation is high, the oil pools are near together, especially in the area east of Bartlesville, in Osage, Washington, and Nowata Counties. In this area the oil has probably migrated shorter distances. More definite statements are not warranted. An extreme view is expressed by McCoy, who believes that the oil of this area has been derived from materials near at hand and has entered the oil reservoirs themselves along faults connecting the sands and the shales. It is believed by Van Verveke that the petroleum of the Alsace field originated near the reservoir that contain it.

Minimum Inclination Necessary For Migration

The inclination necessary for migration varies with the porosity

and size of pores, gas pressure, and viscosity of the oil. Examples

are not rare where segregation has taken place in sands dipping less

Hewett, D. F., and Lupton, C. T. : Anticlines in the Southern Part of the ' Big Horn Basin, Wyoming. U. S. Geol. Survey Bull. 656, p. 44, 1917.

McCoY, A. W. : Notes on Principles of Oil Accumulation. Jour. Geology, vol, 27, p. 254, 1919.

Geology Of Petroleum

than half a degree. In the Lambton County field, Ontario, where the oil is found in a porous limestone, the segregation in pools at crests of folds is very clear. The beds in general dip less than 50 feet to the mile, and at many places the dips are much lower. In the Mid-Continent field, migration has probably taken place in beds dipping less than 20 feet to the mile. —Laboratory experi-

Fio. 68. — Sketches illustrating (a) ideal parallel, and (6) ideal similar folds.

{After Van Hise.)

ments at the University of Minnesota (p. 110) show that oil will move very readily through sands in tubes tilted less than one degree, when gas is present under low pressure in a closed system.

Behavior Of Folds In Depth

The zone of deformation affected by mountain-forming folds is comparatively shallow. Thus, in the region between Tyrone and Harrisburg, Pennsylvania, the depth involved as calculated by

Structural Features Of Reservoirs 165

R. T. Chamberlin is estimated to be 5.7 miles at one end of an earth element and 32.7 miles in the region affected at greatest depth.

In areas of deformation two types of folding are distinguished. In one type the beds are approximately parallel throughout. Such folds are known as parallel folds (Fig. 68, a). In the other type the curvatures of the beds tend to remain the same. In readjustment of beds to fit the fold, all parts of the bed are affected. Such folds are known as similar folds (Fig. 68, b). -Similar folds are characteristic of deformation at great depths, where beds are folded in the zone of flowage. Folding of this type is exhibited in the Vermilion iron range, in the Marquette iron-bearing district, and at many other places in the Lake Superior region, where it has been investigated by Van Hise, Leith, and others.

In areas of similar folding the folds persist vertically and may remain similar through great depths. In areas of parallel folding the deformation is less intense and the amplitude of the folds is likely to change with depth./ The highest bed represented in Fig. 68a, shows folds of very low amplitude; the amplitudes of the folds in the lower beds become greater but finally decrease again. This is the type of folding which is characteristic of many petroliferous areas in rocks older than the Mesozoic. In such areas, therefore, the ampHtude of folds may be expected to increase in depth where erosion has not removed the higher parts of the folded zone, exposing conditions illustrated in the lower part of Fig. 68a.

Where only one fold is developed such a fold also may become sharper with depth./ The conditions are illustrated by Fig. 69, which represents an experiment by Willis.* The fold was produced by force applied at the right end. The anticline shown in the lower sketch is sharper in the lower beds.

Pressure applied horizontally to bodies of strata is frequently

Chamberlin, R. T. : Appalachian Folds of Central Pennsylvania. Jour, Geology, vol. 18, pp. 228-251, 1910.

*Van Hise, C. R., and Leith, C. K. : Geology of the Lake Superior Region. U. S. Geol. Survey Mon, 62, p. 123, 1911.

Van Hise, C. R.: Principles of North American Pre-Cambrian Geology. U. S. GeoL Survey Sixteenth Ann. Rept., part 1, pp. 597-601, 1895.

'Leith, C. K. : Structural Geologj'. P. 107, New York, Henry Holt & Co.,

*WiLLi8, Bailbt : Mechanics of Appalachian Structure. U. S. Geol. Survey Thirteenth Ann. RepL, part 2, p. 247, 1893.

Geology Of Petroleum

relieved by faulting. The stresses are applied at considerable depths but are relieved upward because the rock bodies can most readily move upward. Frequently the stresses are relieved along an inclined plane, as is illustrated by Fig. 70. If the upper strata include shales or clays, as is common in oil fields, the upthrust is

partly taken up by compacting the shales. Thus in areas of relatively gentle deformation the fold originating in depth may tend to die out toward the surface.

In many oil fields of the earth the amplitudes of folds ii

Structural Features Of Reservoirs 167

with depth. That is true in certain European fields where folding occurred between the periods of deposition of the several petroliferous series./ It is illustrated in Rumania, where folding and deposition of strata that yield petroleum took place alternately through a long period in Miocene time. In the Oklahoma-Kansas field the increase in amplitude of folds with depth has bpen noted by many investigators. In northern Texas some very gentle half domes become closed with depth. In some folded areas the ampUtudes of folds increase with depth because the lower beds were

Fig. 70. — Sketch showing folds developed above a fault.

folded before the upper ones were laid down unconformably over

them.

The increase of folding with depth is illustrated in the Gushing

pool, Oklahoma. Fig. 71 shows contours on the out-cropping

Pawhuska limestone as mapped by Buttram. These contours

indicate folds of small amplitude. The contours on the Bartles-

ville sand as mapped by Conkling indicate folds of much greater

amplitude (Fig. 72). As shown by the cross section along the north

line of Sees. 8 and 9 (Fig* 73), the Tucker sand dips much more

steeply than the Bartlesville sand. The shale between the Bartles-

CoNKLiNG, R. A. : The Influence of the Movement in Shales on the Area of Oil Production. Atn. Inst. Min. Eng. BvU, 119, pp. 1969-1972, 1916.

Geology Of Petroleum

ville and the Tucker becomes thinner at the crest of the anticline. Ohem states that there is probably an unconformity below the Bartlesville sand in the Gushing region.

In Oklahoma, northern Texas, and Louisiana, gentle deformation has been going on until a very late geologic period, continuing, locally at least, well into the Tertiary, if not to recent times. It is obvious that, for the parts of this region where parallel folds have

R7 £

Fig. 71. — Sketch showing part of Gushing field, Oklahoma, with contours on

Pawhuska limestone. {After Buttram.)

formed and where erosion has not cut too deep into the deformed zone, the present surface is in the upper part of the deformed element, as illustrated in Fig. 68a, and that an increase of amplitude of folds with depth may be expected.

It is noteworthy that in the lower part of Fig. 68a the amplitudes of the upward folds decrease with depth. Toward the axes

Ohbrn, D. W.: The Influence of the Movement in Shales on the Area of Oil Production (Discussion of Paper by Richard A. Conklin, New York Meeting, Feb., 1917). Am. Inst. Min. Eng. BuU. 123, pp. 389-390, 1917,

Structural Features Of Reservoirs 169

R.7E.

Fig. 72. — Sketch showing part of Cushine field, Oklahoma, with contours on Bartlesville sand. Contour interval is ten feet. (After Conkling.)

of these folds the dip increases. Stigand states that when the dips increase toward an anticlinal axis on both sides, such anticlines "can rarely give good results.'* Such anticlines, he states, are found in Crimea.

Fig. 73. — Section showing top'of Bartlesville and Tucker sands in part of Gushing field, Oklahoma. The interval between the sands increases away from the crest of the anticline. (AJUr Conkling.)

Stigand, I. A. : Discussion of a Paper by Thompson in Inst Min. and Met. Trans, y vol. 20, p. 264, London, 1911.

Chapter Xi Deformation Of Petroliferous Strata

Defonnation in Unconsolidated Materials.-In many districts the petroliferous beds are covered by strata that include considerable thicknesses of unconsoUdated clay, marl, or clayey sand. Id such districts, even after extensive deformation by folding and faulting,, the reservoir rocks may retain large acciunulations of oil and gas. ) Some of the most productive oil fields are in areas of rocks that are largely unconsolidated where the beds lie in overturned folds or are greatly disturbed by complicated faults. In unconsolidated materials openings due to faulting and folding tend to close promptly, so that the oil remains in the reservoir. In such materials there is generally some leakage, however, and oil seeps, asphalt, gas seeps, mud volcanoes, brine springs, and other surface associates of oil or gas are generally found above the reservoirs. Many of the Tertiary oil fields are in highly deformed rocks. These include many districts in GaUcia, Rumania, Russia, Burma, Java and other fields of Oceanica, and the principal fields of California. These fields in general are marked by prominent surface indications of oil, and most of them are in areas of complicated faulting or folding. In consoUdated rocks that had undergone so much deformation the gas pressure would have driven the bulk of the available oil from its reservoirs. In consolidated rocks the most productive fields are f oimd in regions that have suffered only gentle deformation. Oil reservoirs in consolidated rocks have doubtless lost their stores by leakage attending thrust faulting and overturned folding. In consolidated rocks oil generally is in the simpler structural features only; in unconsolidated rocks it is often found in the most complicated ones, as is shown in many fields in California, Galicia and Rumania. In some of these fields folding probably took place after accumulation. In such strata the oil may be found in synclines or in any other position with regard to the structure.

Influence of Faulting on Reservoirs. — The shales that supply the so-called impervious covers to keep the petroleum confined within the sandstones are not absolutely impervious to fluids, otherwise the oil and gas could not pass from them to the porous beds in

I>.

Deformation Of Petroliferous Strata 171

which they are found. Fracturing doubtless facilitates the passage, however, by supplying more readily available openings. / In the Santa Clara, Summerland, Puente Hills, Los Angeles, and other California districts the fracturing appears to have aided accumulation by permitting the oil to move from lower to higher levels, where it is, of course, more readily accessible./ The oil accumulation in the dome near Jennings, Louisiana, is said to be related to a fault. In the Labarge and Spring Valley regions, Wyoming, the oil seeps are obviously related to planes of movement subsidiary to the great Absaroka fault. . In the Brunswick district, Oklahoma, several quarries of bituminous rock are opened on or near normal faults. Other asphalt and ozokerite deposits in fissures have been mentioned. It is clear that some faults have served as channels through which petroleum has moved.

As is well known by students of ore deposits the fissures that serve as channels of metalliferous waters and the openings that are filled by metalliferous ores are in general the fissures and faults of small throw rather than the great faults. Except in limestone a comparatively small number of veins are formed in faults of considerable tangential movement. Without doubt the gouge developed along the greater faults provides an impermeable barrier and prevents circulation. It is obvious that this principle will apply also in many districts that yield petroleum. The smaller faults may serve as channels for migration and escape of oil, whereas the greater faults may seal the reservoirs.

In many oil fields the beds are cut by faults along which neither asphalt nor oil seeps have been observed. In the Lander field, Wyoming, oil seeps and tar springs are found at the surface, but along a thrust fault over 2 miles long, with a throw of 1,180 feet, that penetrates the Little Popo Agie dome, neither oil seeps nor asphalt deposits were noted, although the oil flows from some of the wells and is under pressure.

The Irvine oil field, Kentucky, lies along a fault, as do also the Homer and Gusher Bend fields, Louisiana. According to McCoy

Eldridge, G. H.: The Asphalt and Bituminous Rock Deposits of the United States. U. S. Geol. Survey Twenty-second Ann. RepL, part 1, p. 306,

Woodruff, E. G.: The Lander Oil Field, Fremont County, Wyoming. U. S. Geol. Survey BtiU. 452. 1911.

172 . Geology Of Petroleum

small faults are present in many of the Oklahoma fields and appar" ently influence accumulation favorably.

In the southern California districts many strong faults cut the oil-bearing strata, but relatively few of these are marked by great oil seeps and asphalts. In the Santa Cruz district the Thurber, New, and Hole bituminous sandstone quarries are on faults, is also a prominent brea deposit in the Los Angeles district. Considering, however, the large amount of oil and of asphalt and bituminous rock in California, and the large number of faults that occur in the oil fields, the number of faults that carry large deposits of the natural hydrocarbons is small.

The Buckhorn district, Oklahoma, contains numerous faults and numerous areas of bitimiinous rock, yet there is no very obvious relation of some of the deposits of the bitimiinous rock to the greater fault planes. In the Uinta Basin, Utah and Colorado, the gilsonite veins, though remarkably uniform as to strike, apparently occupy fissures of little or no displacement,'* and so also do the wurtzilite veins in the Uinta district. The grahamite vein in Ritchie County, West Virginia, occupies a fissure along which very little if any displacement by faulting has been shown.

Eldridge, G. H.: Op. cit, p. 393. *Eldridoe, G. H. : Op, cit, p. 274. *Idem, p. 339.

*White, I. C. : Origin of Grahamite. Geol. Soc. America BvU,, vol. 10, p. 278, 1898. Eldbidgb, G. H. : Op. cit. p. 232.

Chapter Xii

METAMORPmSM OF PETROLEUM BY DYNAMIC

Agencies

Petroleums and the materials of which they are formed are changed by the heat and pressure that attend dynamic metamorphism of strata. In the Appalachian region and in the Mid-Continent field of the United States petroleum and gas are closely associated geographically with beds containing coals, and the degree of metamorphism of the coals affords a kind of index to the intensity of the metamorphic processes. In these regions the coals are altered progressively more toward the areas of intense deformation. The hydro-carbons are driven off and the coal becomes richer in fixed carbon. In the Appalachian region the amount of fixed carbon is greater in the most highly folded area and decreases toward the west, where the intensity of metamorphism is decreased. Petroleum and gas in reservoirs associated with the coals show differences corresponding to the alteration of the coals. This relation between the distribution of oil and the character of coal was first shown by David White and has been treated also by Fuller 2 and by Gardner.

In the Appalachian region, as stated by Fuller, neither oil nor gas, except in a few minor accumulations, has been found east of the west face of the outermost strong fold of the Appalachian Mountains (Fig. 74). Between this face and the hne of 60 per cent carbon coals there is much gas in the northern part of the field and some in the southern part, with an oil pool here and there, but the main oil field is west of the 60 per cent carbon line. (See Fig. 75.)

In the Ouachita-Arbuckle region, Oklahoma and Arkansas, according to Gardner, gas only has been found in the region near and northwest of the Choctaw fault. The main oil fields are 50

*Whitb, David: Some Relations in Origin Between Coal and Petroleum. Washington Acad. ScL Jour,, vol. 5, pp. 189-212, 1915.

*FuLLEB, M. L.: Appalachian Oil Fields. Geol. Soc. America BvU,, vol. 28, p. 643, 1917.

Gardner, J. H. : The Mid-Continent Oil Field. Geol. Soc. America BidL, vol. 28, pp. 685-720, 1917.

Geology Of Petroleum

miles or more northwest of the Choctaw fault, although there are 10 or more gas fields in this region.

Fig. 76 is a map showing isovols in Oklahoma, according to Fuller.' The maximum production has come from the zone

Fia 74 — Map of Appalachian region, showing relation of developed oil fields to the line of 60% fixed carbon in coals. (After FvUerm)

between the 50 and 55 isovols. Fuller states that the promise of the various zones is roughly as stated below:

Relative Chances of Finding OU

Zone of 50% to 55%* carbon ratios 100

Zone of 55% to 60% carbon ratios 10

Zone of 60% to 65% carbon ratios 1

,' *An isovol is a line connecting points where the coals have equal percentages of fixed carbon (and therefore of volatile matter). See White, David, Washington Acad. Sci. Jour., vol. 5, p. 198, 1915.

'Fuller, M. L. : Carbon Ratios in Carboniferous Coals of Oklahoma and Their Relation to Petroleum, Econ. Geology vol. 15, p. 232. 1920.

Metamorphism Of Petroleum

(

N

N /

N S

dUl'JCfi

'%

%.

oS

/

Geology Of Petroleum

Fig. 76.— IbovoI map of Oklahoma. (,Afler FuUer.)

Metamorphism Of Petroleum

In north-central Texas many of the oil pools are associated with strata that contain coals. The coals become richer in fixed carbon toward the east. Nearly all the oil pools lie between the 50 and the 55 per cent isovol (See Fig. 77). In the belts yielding coals

*

I I /fire

4. bv/'e

TOfi yoi

%

'm0*r

4H0Af*tt.

eA3rA4t/v.

%

r

m.

Six

COAfCO 4d

I:

t9*9

Fig. 77. — Sketch map showing isovols and relation of oil pools to carbon ratios

of coals in Northern Texas. (A/fer Fuller.)

that carry between 55 and 60 per cent of fixed carbon some oil is present, with considerable gas. East of the line showing 60 per cent fixed carbon no commercial accumulations have been developed.

Geology Of Petroleum

It is noteworthy that in southern California, Rumania, and Galicia oil pools are found in rocks that have been closely folded and intensely faulted. In such surroundings large quantities of petroleum, much of it of heavy grade, remain. In these regions the strata include unconsolidated clays or marls that have prob-

Relation op Oil and Gas to Carbon in Coal

Carbon Ratios

(Surface)

Prevailing

Characteristics

of Sands

Prevailing Water

Conditions (in Mixed

Formations)

Production'

Over 70

Hard and tight.

Tight, with a few porous spots.

Variable, with porous beds of limited extent.

Fairly continuous and open.

Softer, less firmly consolidated, and more continuous and porous.

Usually unconsolidated.

Water usually absent except near surface.

Water usually absent below 1,500 feet.

Water usually absent below 2,500 feet (often below 2,000 feet).

Water usually absent below 3,000 feet (often below 2,500 feet).

Water usually absent below 3,000-3,500 feet.

Sands usually saturated to all depths reached by wells.

No oil or gas, with rare exceptions.

Usually only "shows' ' or small pockets. No commercial production.

Commercial pools rare, but oil of exceptionally high grade when found. Gas wells common, but usually isolated rather than in pools.

Principal fields of light oils and gas of the world.

Principal fields of medium oils

Under 50

of Ohio-Indiana and Mid- Continent fields.

Fields of heavy Coastal Plain oils and of unconsolidated Tertiary or other fonuations.

"Fuller, M. L.: Relation of Oil to Carbon Ratios of Pennsylvanian Coals in North Texas. Econ. Geology, vol. 14, p. 538, 1919.

Unusually porous sands like the Dakota of the West and the St. Peter of the East carry water in quantities far above the average and to far greater depths and distances from the outcrops. Water is also carried in fissures.

''Statements of quality apply to oils from sandstones; oils from limestones are usually heavier.

ably sealed the faults as they were being formed. Deformation of the petroliferous strata probably took place under much thinner cover than in the Appalachian and Mid-Continent fields. As has been pointed out by Fuller, the fixed carbon in coals doubtless increases with depth, and in certain regions, as would be expected,

. Metamorphism Of Petroleum . 179

the oils are lighter and higher grade in the deeper sands. Intense

deformation probably does not result in metamorphism of oil to

form the higher grades and gas, unless there is a considerable cover

above the petroliferous strata.

Attempts have been made to ascertain whether the fixed-carbon content of carbonaceous shales shows a similar correspondence to the character of petroleum associated with the shales. According to Fuller, the results are inconclusive (1919).

Chapter Xiii

Gas Pressure And Oil Recovery

Gas Pressure. — Whenever petroleum is formed gas is probably generated. Oil absorbs gas, the amount absorbed depending upon the pressure. Whether the oil and gas are formed before or after deformation of the strata, the gas tends to accumulate in the highest parts of a closed fold. If, however, there ia enough oil to absorb the gas present at the prevailing pressure, it will be completely absorbed, and oil and gas will issue together from a boring sunk to the top of a high fold. At the temperature and pressure that prevail in most fields, methane and ethane are probably always in the gaseous state, though some of the heavier gases that issue in the gaseous state may be liquids in the reservoirs. Pen-

Fia. 78. — Sketch illustrating a gas pool with underlying water body in Band connected freely with surface. The level of ground water ia assumed to be at the surface. Theoretically the pressure should equal the weight of a column of water aa high as ab.

tane and hexane are liquid. They are the chief constituents of gasoline.

If the gas accumulates at the top of the fold it exerts a pressure on the oil and tends to drive it to a lower structural position. The oil in turn drives down the water. If the reservoir rock communicates with tiie surface of the earth at any place and is permeable the water will flow out of the reservoir. Thus the gas pressure will equal the weight of a column of water as hh as the difference between the elevation of the gas body and the surface opening where the reservoir rock crops out. (See Fig. 78.)

In New York, according to Orton, ' the gas pressure at many 'Orton, Edward: Petroleum and Natural Gaa in New York. New York State Mus. fiuii., vol, 6, No, 30, p. 488, 1899.

Gas Pressure And Oil Recovery 181

places is independent of depth. In Pennsylvania, according to I. C. White, the gas pressure generally increases with depth.

In Oklahoma, according to Gardner, the gas pressure in many wells is about that of a column of water eqtial in length to the depth of the well — or> in other words, 43.4 pounds to the square inch for each 100 feet of depth. The well pressure is usually somewhat more or less than this figure, owing partly to differences in weight of water due to differences of salinity. The gas pressure moreover, is evidently not everywhere a reactive pressure against a water head. A well at Gushing 2,600 feet deep gave a gas pressure of 1,120 figuring the theoretical hydrostatic pressure of 43.4 pounds per hundred feet gives 1,128.4 pounds. A well near Claremore, at a depth of 860 feet, gave a pressure of 375 pounds; the theoretical pressure as above calculated is 373.2. A well near CoUinsville, at a depth of 1,100 feet, gave a pressure of 495 pounds; the theoretical head at this depth is 477.4 pounds. These were closed pressures on new wells. On the other hand, some pressures are below what would be expected. Haworth reported a well in Kansas 1,000 feet deep with a pressure 250 pounds to the square inch, whereas one-half a mile away 900 feet deep showed 375 pounds.

Lenses of sand that are completely sealed may contain gas deposits under pressures that are independent of their depth. As deposits on monoclines are generally sealed above, and as many of them are also sealed below, gas deposits on monoclines are likely to exhibit pressures independent of depths. As pointed out elsewhere, petroleum is probably converted to gas by heat and pressure attending dynamic metamorphism. As stated by White and by Fuller, the amount of metamorphism sufficient to change coals so that their carbon ratio equals 65 per cent or more is probably sufficient to convert oil to gas. In general, heat and pressure increase with depth, so that the amounts of gas, and therefore the gas pressure, will increase. Thus an increase of gas pressure with depth may be expected, whether the gas pressure is balanced by hydrostatic pressure or not.

White, I. C. : The Mannington Oil Field. Geol. Soc. America Bull,, vol. 3, p. 196, 1892.

KARDNER, J. H. : The Mid-Continent Oil Fields. Geol. Soc. America Byll.f vol. 28, p. 702, 1916.

Geology Of Petroleum

Initial Gas Pressures At Different Depths in Several Gas Fields

(Prepared by Mills and Wells)

Name of Bed

Salt sand Biff lime sand

Keener sand

Big Injun sand

Berea sand

Butler gas sana

Hundred-foot sand . . Third sand

Fourth sand

Fifth sand

"Clinton" sand

Trenton limestone. .

Benson sand

(?)

(?)

(?)

(?)

Unconsolidated sand

Locality

Woodsfield, Ohio Southwest corner of Wayne Township, Belmont County, Ohio Southeast corner of Malaga Township, Monroe County, Ohio Wayne Township, Belmont County, Ohio Woodsfield, Ohio Woodsfield, Ohio Woodsfield, Ohio Summerfield, Ohio Sunsbury Township, Monroe County, Ohio Summit Township, Butler County, Pennsylvania Butler, Pennsylvania Butler, Pennsylvania Butler, Pennsylvania Butler, Pennsylvania Butler, Pennsylvania Butler, Pennsylvania Harrison Township, Knox County, Ohio

Cleveland, Ohio

Newberg, Ohio Findlay, Ohio Kokomo, Indiena Cleveland, Ohio Barbour County, West

Virginia West Virginia Havre, Montana Havre, Montana Louisiana Louisiana Loco, Oklahoma

Initial

Gas

Pressure

Depth

(Pounds

(Feet)

per

Square

Inch)

1,295

1,310

1,465

1,515

1,468

2,090

1,698

2,060

1,200

1,400

1,452

1,800

1,568

1,950

2,700

/2,500

1,100

3,000

4,500

4,090

1,800

2,989

1,420

1,370

1,650

1,800

Average Pressure

per

100 Feet

Depth

(Pounds

per Square

Inch)

Authority

Mills and Wells Do.

Do.

Do.

Do. Do. Do. Do. Do.

Do.

Do. Do. Do. Do. Do. Do. Do.

Rogers'*

Van Hom& Orton*

Do. Van Horn 6 I. C. White

Do. Stebinger*

Do. Knapp/

Do.a McMurray and Lewis*

''RoGEBS, Q. S.: The Cleveland Gas Field, Cuyahoga County, Ohio. U. S. Geol. Survey BuU. 661, p. 37, 1917

''Van Horn, F. R.: Reservoir Gas and Oil in the Vicinity of Cleveland, Ohio. Am. Inst Min. Eng. Trans., vol. 66, p. 839, 1917.

'Orton, Edward: The Trenton Limestone As a Source of Petroleum and Natural Gas in Ohio and Indiana. U. S. Geol. Survey Eighth Ann. Bept., p. 645, 1889.

Personal communication.

'Stebinger, Eugene: Po:>sibilitie3 of Oil and Gas in North-Central Montana. U. S. Geol Survey Bull. 641, p. 73, 1916.

Knapp, I. N.: Discussion of Paper by R. W. Johnson, The Rdle and Fate of Connate Water in Oil and Gas Sands. Am. Inst. Min. Eng. Trans., vol. 51, p. 593, 1915.

Knapp, I. N.: Discussion of Paper by W. H. Kobbb, The Recovery of Petroleum from Unconsolidated Sands. Idem, vol. 56, p. 825, 1917.

McMuRRAT, W. F., and Lewis, J. O.: Underground Wastes in Oil and Gas Fielda and Methods of Prevention. Bur. Mines Tech. Paper 130, p. 13. 1916.

Gas Pressure And Oil Recovery 183

The table, prepared by Mills and Wells, (p. 182) shows the gas pressures in many reservoirs and the depth of the wells. The fifth column shows the pressures per 100 feet of depth. The differences are noteworthy. In most of these districts, at least, it is highly improbable that the gas bodies are in equilibrium with a water column connecting with the surface. Evidently the reservoirs did not conmiunicate freely with the surface.

Behavior of Certain Wells That Yield Oil and Gas. — Some borings that penetrate reservoirs yield initially large amounts of oil that flows from the well and may be thrown under pressure high above the derrick floor. Such wells are termed "gushers" in the United States and "spouters" or "fountains" in foreign fields that are developed by the British. They are characteristic of fields that have reservoirs containing gas imder high pressure. Production may increase for a few days while drainage lines are being established in the reservoir, but almost invariably the initial production declines rapidly after a short period. The gas, under pressure, forces out the oil into the boring and causes it to rise vertically. Sand and gravel frequently rise with the oil and gas. A well that penetrates only the top of a sand reservoir may "drill itself in," or sink to the bottom of the reservoir while sand is being expelled with the oil. This process is conmionly attended by increased production dm'ing the early stages of the well's life.

Since the pressure of gas forces oil out of the rocks into the wells, its pressure is of great economic interest. In porous rocks the decline of gas pressure over a field is approximately uniform. Every thousand feet of gas that is lost in general tends to lower the pressure. The practice of allowing the gas to issue freely in open wells is now forbidden by law in many states. Good pressure in a field after a long period of production is looked upon as a favorable indication for its future.

Some wells that at first yield gas subsequently yield oil. Indeed, it is a common, though wasteful practice to allow gas to escape from a well in the hope that ultimately the well will produce oil. Not only is the gas wasted, but oil also is likely to be wasted, because the gas is the means by which the oil is expelled from the rocks. If a small pocket of gas has accumulated at some high

MiLLS, R. V. A., and Wells, R. C: The Evaporation and Concentration of Waters Associated with Petroleum and Natural Gas. U. S. Geol. Survey BuU, 693, p. 28, 1919.

184 Geology Of Petroleum

point in the roof of a reservoir and ia punctured by a drill gas will rise first and later oilj which is under pressure. This ia illustrated in Well 1, Fig. 79. If a gas well is on the flank of a fold near the contact of gas and oil, it is obvious that release of the gas pressure which holds the oil down will permit the oil to rise higher in the reservoir, or to be pushed up by water pressure. Thus in Well 2, Fig. 79, gas would issue first, and oil later. Some wells yield petroleum first and salt water later. Well 3, Fig 79, would be first a petroleum well, and as the pressure declined and petroleum was removed from the reservoir, salt water would rise to take ite place. Many petroleum wells become salt-water wells. A famous example is the Dos Bocas well, in Mexico, which after yielding oil at the rate of 100,000 barrels a day for 58 days, began to spout water in large quantities.

Many oil wells flow by heads, or spout periodically like geysers. The bore is gradually filled with oU, and gas accumulates below,

FiQ, 79. — Sketch ehowing gas wells (1 and 2,) that would become oil welb if, because of decreaae of pressure of gaa, the plane of contact of oil and gas were to rise. If the plane of contact between oil and water were elevated because of removaJ of gas or oil, well 3 would cease to flow oil and would flow

until the pressure is sufficient to cause the oil to overflow. As the oil flows out the casing head, pressure ia relieved and that allows the gas to expand suddenly and to raise the column of oil withforce.

Some flowing wells, after being capped and reopened will cease to flow. In other cases if the flow of the oil is stopped it may not be re-established in its original force. As a result many operators prefer not to shut off a well entirely, but to allow it to flow at a low rate during the period that preparations are made to dispose of the oil. In some cases the gas pressure has been reduced by other wells tapping the reservou- between the time of closing and reopening the well.

When a reservoir containing gas is pierced by a boring and the pressure is decreased by the issue of gas, a series of changes in

eAS PRESSURE AND OIL RECOVERY

r

f.

I'

s--

''

a

Flo. 81. — Composite decline curve for the Bartlesville field, Oklahoma. (Afta- Beal.)

Geology Of Petroleum

equilibrium results. Expansion lowers the temperature of the gas, and the salt-water spray which is commonly present in the issuing gas will be cooled. Gas under low pressure will .absorb more water than gas under high pressure, and evaporation results. As a result of the cooling and evaporation, much salt is deposited. The casings of wells and the interstices of sands may be filled with sodium chloride so that the well will cease to flow. Calcium carbonate, magnesium carbonate, iron carbonate, and calcium, barium, and strontium sulphates are deposited in casings and presumably also in interstices of sands in reservoirs.

Paraffin wax is commonly dissolved in oil. Cooling follows

:-

u

r ?oo

,

u u

rr

z

►

Year

Fig. 82. — Generalized decline curve of the wells in the eastern part of the

Osage Indian Reservation, Oklahoma. (After Beat.)

relief of pressure. In some wells the wax is deposited in quantities

so great as to retard production.

The life of most oil wells is comparatively short. Some start

flowing at high rates, many spouting 5,000 or 10,000 barrels a day

or more. As a rule they decline rapidly and steadily after they

have reached their maximum, which is generally during the first

few days. The first year's flow is usually much greater than the

yield of any other year. Curves showing the rates of decline for

several fields are given in Figs. 80 to 84. The numbers at yearly

'Mills, R. V. A., and Wells, R. C: The Evaporation and Concentration of Water Associated with Petroleum and Natural Gas. U. S. GeoL Survey Bidl, 693, pp. 44-50, 1919.

Gas Pressure And Oil Recovery

t CO

o

/

— -

r-Thif

i

-9-ir

S. zo

n

"

::

JO ZO 50 40 50 60 70 80 90 100 HO itO 130 140 150

Initial production (first Z4 hours)

Fig. 83. — Curve showing relation of initial production to average daily production per well during the first year in the Lawrence County field, Illinois. (After Beal.)

intervals on the curves of Figs. 81 and 84 represent the number of properties employed in determining averages of each year.

In estimating the future production of a field, two methods are employed. In one, curves such as those prepared by Beal are used.

Fig. 84. — Curves showing the decrease in daily production during the first year on several properties in the Bird Creek-Flatrock field, Oklahoma, and in the Lawrence County, Illinois, pool. The numbers on the curves show the number of wells used to obtain the data. (After Beal,)

Geology Of Petroleum

In the other the volume, porosity, and saturation of the sands and the amount of oil which may eventually be recovered are estimated from the data available. The latter method, which has been developed by Washburne and others, is a useful check on the curves showing decline of wells, but the results are not expected to be precisely accurate because the determinations are affected by many variable factors, and generally not all of these are known.

VOLXTME OF A HOJEtlZONTAL SaND, PER HECTARE AND PER ACRE''

Area

ThickneBs of Sand

Volume of Sand

Cubie Meters

Barrels of 42

United States

Gallons

1 hectare

r

1 meter

Ifoot

Ifoot

62 ,898

1 hectare

1 acre

''WAJSHBXTBm:, C. W. : The Estimation of Oil Reserves. Am. Inst. Min. Eng. Trans., voL 51. p. 646. 1916.

The figiires of the last column multiplied by the thickness of the sand, by the porosity, and by the relative saturation give the capacity of the sand in barrels per unit area. Thus, a sand 12 feet thick, with a porosity of 15 per cent and a relative saturation of 75 per cent, contains 12X0.15X0.75X7,758=10.473 barrels per acre. With an assiuned extraction factor of 60 per cent, each acre would produce 6,284 barrels.

The data showing decrease of yield of groups of wells in a district may be presented in many ways, as shown in a recently issued bulletin by Beal. Each method exhibits certain advantages imder certain sets of conditions. .

It is noteworthy that not only does the yield of individual wells diminish rapidly,but the initial yields and total production of wells generally diminish steadily as more wells are put down in the field.

Probably half the oil in some reservoirs remains in the rocks after the fields have ceased to yield. It adheres to sand grains, and in

*Beal, C. H. : The Decline and Ultimate Production of Oil Wells, with Notes on the Valuation of Oil Properties. U. S. Bur. Mines Bull, 177, pp. 1-215,

Gas Pressure And Oil Recovery 189

the absence of gas under pressure it can not be moved (Fig. 85). By proper management and conservation of gas pressure, the maximum yields may be obtained. If the gas is tapped above the oil and the gas pressure is wasted without allowing the gas to do its work, it may be impossible to obtain the principal part of the oil stored in the rocks. It is common practice to increase the flow by pumping the sands to a vacuum. Another method consists in driving water into the sands and floating the oil to points of issue. Thus water that is allowed to enter the sands in one well will make its way down the dip to another well, pushing the

oil ahead of it. A third method consists in pumping compressed air into the sands. Natural gas is used in some fields instead of air and has the advantage that it absorbs the gasoline, which may be recovered by condensing the gas after it has issued from the wells. These methods prolong the hfe and increase the production of a field, but they are generally not employed until the field b near exhaustion.

Linns, J. O. : Methods for Increasing the Recovery from Oil Sanda. U. S. Bur. Mines Bull. 148, pp. 1-128, 1917.

Chapter Xiv

Petroliferous Provinces And Petroleogenic

Epochs

Petrologists have long used the term "petrographic province" for a district or region that contains bodies of igneous rocks which, though differing somewhat in composition and character, nevertheless exhibit similar features that indicate similar generic [ relations. Similarly, the ore deposits of certain regions that have

conmion characteristics are grouped within a metallogenic province.

The term "petroliferous province,'' first used by Woodrufif, suggests a region containing accumulations of petroleum that are nearly related genetically and that have closely similar geologic surroundings.

Schuchert' classifies areas as regards petroliferous possibilities as follows:

1. The impossible areas for petroliferous rocks.

(a) The more extensive areas of igneous rocks and especially those of the ancient shields: exception, the smaller dikes.

(6) All pre-Cambrian strata.

(c) All decidedly folded mountainous tracts older than the Cretaceous; exceptions, domed and block-faulted mountains.

(d) All regionally metamorphosed strata.

(e) Practically all continental or fresh- water deposits; relic seas, so long as they are partly salty, and saline lakes are excluded from this classification.

*LiNDGREN, Waldemar: The Geological Features of the Gold Production of North America. Am. Inst. Min. Eng. Trans, y vol. 33, pp. 790-845, 1903; Metallogenetic Epochs. Econ. Geologijf vol. 4, pp. 409-420, 1909.

Emmons, W. H. : The Principles of Economic Geology, pp. 269-270, 1918.

Woodruff, E. G.: Petroliferous Provinces. Am. Inst. Min. Eng. BuU. 150, pp. 907-912, 1919.

*ScHUCHERT, Charles: Petroliferous Provinces; Discussion of Paper of E. G. Woodruff. Am. Inst. Min. Eng. Bull. 155, p. 3059-3060, 1919.

Petroliferous Provinces 191

(J) Practically all marine formations that are thick and uniform in rock character and that are devoid of interbedded dark shales, thin-bedded dark impure limestones, dark marls, or thin-bedded limy and fossiliferous sandstones.

(g) Practically all oceanic abyssal deposits; these, however, are but rarely present on the continents.

2. Possible petroliferous areas.

(a) Highly folded marine and brackish water strata younger than the Jurassic, but more especially those of Cenozoic time.

(6) Cambrian and Ordovician gently folded strata.

(c) Lake deposits formed under arid climates that cause the I waters to become saline; it appears that only in salty waters (not over 4 per cent?) are the bituminous materials made and preserved in the form of kerogen, the source of petroleum; some of the Green River (Eocene) continental deposits (the oil shales of Utah and Colorado) may be of saline lakes.

3. Petroliferous areas.

(a) All marine and brackish water strata younger than the Ordovician and but slightly warped, faulted, or folded; here are included also the marine and brackish deposits of relic seas like the Caspian, formed during the later Cenozoic. The more certain oil-bearing strata are the porous thin-bedded sandstones, limestones, and dolomites that are interbedded with black, brown, blue, or green shales. Coal-bearing strata of fresh-water origin are excluded. Series of strata with disconformities may also be petroliferous, because beneath former erosional surfaces the top strata have induced porosity and therefore are possible reservoir rocks.

(b) All marine strata that are, roughly, within 100 miles of former lands; here are more apt to occur the alternating series of thin- and thick-bedded sandstones and limestones interbedded with shale zones.

Perhaps the greatest petroliferous province is the Tertiary province of Eurasia, which includes all the important producing oil fields of the Old World, except England and Germany. In the

192 Geology Of Petroleum

producing fields of Alsace, Galicia, Rumania, the Caucasus, Turkey, Persia, Burma, Oceanica, and Japan, nearly all the petroleum is derived from Tertiary rocks, except some of that produced in Galician fields, which comes from the Upper Cretaceous. The greater part of the oil from the Tertiary beds is obtained from the Miocene and Oligocene. The oil is accumulated in raised structures except where there has been extensive folding and faulting of unconsolidated rocks near the surface. In general the rocks of this province are not thoroughly consolidated. Although some of the oil is a high-grade light oil, with paraffin base, a larger part of it is low-grade asphaltic oil. The characteristic structural features are domes and anticlines, although oil is found in faulted monoclines in Alsace, in synclines at Boryslaw, at an imconformity in Maikop, and in fault traps and near salt plugs in Rumania. Deformation affecting the petroliferous strata took place in all these areas in the later part of Tertiary time. There is not a continuous belt of Tertiary strata between the oil-bearing regions named. At some places the Tertiary has been eroded; at other places there were probably islands or larger land masses between the Tertiary seas. In general, however, this region between Alsace, Borneo, and Japan, with an arm extending from Borneo to New Guinea and thence possibly to New Zealand, was a site of deposition in early and middle Tertiary time and of extensive deformation later in the Tertiary.

In the Egypt tield, near the Gulf of Suez, oil is found in Tertiary beds that were deformed in late Tertiary time. This field is closely affiliated with the Eurasian province. On the other hand, in the English field, oil comes from Paleozoic strata that are thoroughly consolidated. The EngUsh field should not be included in the Eurasian province. Certain small fields in Germany produce oil from rocks older than the Tertiary.

In North America (Fig. 86) the Pacific coast fields and also the Gulf coast field of Texas and Louisiana are more closely affiUated with the fields of the Eurasian province than with the Appalachian and Mid-Continent fields. They derive their oil chiefly from Tertiary strata that were extensively deformed in late Tertiary time. The rocks are not consolidated, as they are in the Appalachian and most of the Mid-Continent fields. Most of the oil, like

iJt is reported that oil has recently been developed in the Cretaceous in Egypt.

Petroliferous Provinces 193

the greater part of that from the Eurasian field, is of low grade, with asphalt base.

The Appalachian fields, the Lima-Indiana field, and the Mid-

FiQ. 86. — Map of North Americia, showing petroliferoua provinces according to the interpretation of E. G. Woodruff. The hned areas are in the maiu unfavorable.

Continent field, except northern Louisiana and eastern Texas, supply oil from Paleozoic strata that are well consoUdated but not extensively deformed. In general the oil is of high grade, with a

194 Geology Of Petroleum

parafl, or paraffin and asphalt base. The Ontario fields of Lambton and Middlesex Counties supply oil of similar character from Paleozoic strata similarly deformed and constitute a part of the Appalachian province.

The northern Louisiana and eastern Texas fields, including those of the Balcones fault region, Texas, supply oil from Upper Cretaceous strata, from which also nearly all the oil produced in Wyoming, Montana, and Colorado is derived. These fields, though far apart, have certain common features. Each group constitutes a province nearly related to the other group.

In the Caribbean province, including the West Indies, Trinidad, the Gulf coast of Mexico, and the northern part of South America, oil is found in both Cretaceous and Tertiary rocks in various stages of consolidation. The grades of the oil show wide differences.

Petroleogenic epochs are those in which beds that contain oil were laid down. The most productive strata are those of Paleozoic, Cretaceous, and Tertiary age. Petroleogenic epochs are discussed in connection with the geologic age of petroliferous strata on pages 10 to 15.

Chaper Xv Appalachian, Lima-Indiana, And Michigan Fields

Introduction

The United States is divided into physiographic provinces which embrace the principal mountain ranges, plateaus, and plains (Fig. 87), The principal oil fields are in the Appalachian Plateau and interior plains; the Gulf Coastal Plain; the Rocky Mountains; and the California valley and Coast Range. The Appalachian Plateau lies west of and is parallel to the Appalachian Mountains and with

{After Blachi

the interior plains it constitutes the interior lowlands orographic element.' This element, which lies between the Appalachian Mountains and the Roclsy Mountains, contains many of the '"An orographio element U a region which is characterized by certain distinctive geologic features, particularly by a certain type of structure and a more or less uni6ed geologic history. . . . The orographic elemeDta tend to coincide with the physiographic provinces." — Blackweldbr, Elliott, United States of North America. Handbuch der Regionalen Geologie, Band S, Abt. 2, {Heft 11), p. 69, 1912.

Geology Of Petroleum

largest oil -fields in the United States. Among them are the Appalachian field, the Lima-Indiana field of Ohio and Indiana, the Illinois-Indiana field, and the Mid-Continent field except the Sabine uplift, which is included with the Gulf coast field in the Coastal Plain. The Rocky Mountain element includes the fields of Wyoming and Colorado. Some of these fields perhaps should

Symbols and Colors Assigned to Rock Systems in the United States'*

Era

Cenozoic

Paleozoic.

Proterozoic

System

Series

Quaternary

Tertiary

Cretaceous

Jurassic

Triassic

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

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Pliocene

Miocene

Oligocene

Eocene

Upper 1 Lower

Upper Middle

Lower

Upper

Middle

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Pennsylvanian

Mississippian

Upper Middle [Lower

(Cincinnatian Mohawkian I Lower

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Red-purple

Brick-red

Brownish red Gray-brown

'U. S. Geological Survey.

Appalachian, Iima-Ind., And Mich. Fields 197

198 Geology Of Petroleum

be included in the interior lowlands for they Ue on foothill folds of the Rockies much as the fields of the Appalachian geosyncline Ue with respect to the Appalachian Mountains. In accordance with the practice of the statistical branch of the United States Geological Survey, these are described with other fields in the Rocky Mountain division. The California valley and Coast Range embrace the fields of southern California.

Petroleum is found in the United States in rocks that range in age from Ordovician to Recent. Considerable oil is obtained from Paleozoic, Mesozoic, and Tertiary rocks. The general distribution of the strata is shown by Fig. 88.

In the interior lowlands the prevailing rocks are of Paleozoic age. The geologic structure is generally simple, the rocks dipping at low angles. The attitude of the rocks is influenced by the mountain ranges to the east and west of the lowlands and by the structural uplifts which lie between (Fig. 89). These areas of uplift are not much higher than the surrounding lowlands. They are anticlines, domes, or regions of close folding and some of them have a farreaching influence on the structure of the rocks in the lowland area around them.

The Appalachian Plateau is a geosyncline that strikes northeastward and parallels the Appalachian Mountains. On it are superimposed a number of parallel folds, the axes of which lie approximately parallel to the long dimension of the plateau and the Appalachian Mountains. The strata rise gently toward the Cincinnati geanticline, on which are developed the Cincinnati arch in Kentucky, Ohio, and Indiana and the Nashville arch in Tennessee. West of the Cincinnati arch the rocks dip west of north toward Indiana and Illinois, where they form the great coal basin in Illinois, Indiana, and western Kentucky. They rise again toward Missouri and Arkansas in the region of the Ozark Plateau. The strata dip away from the Ozark Plateau in all directions, rising toward the west in and near the foothill region of the Rocky Mountains and toward the south in the Ouachita Mountains.

The Ouachita Mountains, which lie in central Arkansas and southern Oklahoma, were formed at about the same time as the Appalachian Mountains and are regarded by some as an extension of that range. The Mississippi embayment, which contains rocks of much later age, separates the two ranges by about 300 miles.

Appalachian, Lima-Ind., And Mich. Fields 199

Close folding is characteristic of regions near the central axes of the Appalachian and Ouachita Mountains. In the Rocky Mountains the folding is generally less intense, yet the beds are steeply tilted, so that at many places they lie on edge or are overturned. The Cincinnati arch and the Ozark uplift cover wide areaa but are marked by low d

The Ouachita orographic element is not a continuous range but consists of a series of uplifts separated by rocks which are more nearly flat-lying. The Ouachita element extends westward from Hot Springs, Arkansas, into southern Oklahoma. It embraces the Ouachita Mountains in Arkansas, the Arbuckle Mountains, in

200 Geology Of Petroleum

south-central Oklahoma; and the Wichita Mountains, in southwestern Oklahoma. Between the Arbuckle and Wichita Moun- *tains the rocks dip at comparatively low angles.

South of the Ouachita Mountains, near the center of Texas, is the Llano uplift of ancient rocks. This uplift, although its surface is rather rugged, does not rise conspicuously above the surrounding country, but its influence on the attitude of the strata is apparent in the plains country far to the north, where in the north Texas field large deposits of petroleimi have been discovered.

In the interior lowlands the outcropping rocks are mainly Paleozoic sedimentary beds (Fig. 88). Pre-Cambrian rocks crop out in small areas in the Ozark Plateau, southeastern Missouri; in the Arbuckle and Wichita Mountains, Oklahoma; in central Texas; and in larger disconnected areas in southwestern Minnesota, extending into Iowa and South Dakota. At some places ancient igneous rocks, principally granite, have been encountered below the surface. A deep well at Rolla and also one in the Joplin district, Missouri, were sunk to granite, and farther west, in Kansas, a great belt of granite has been revealed below the surface by borings sunk for oil. Granite is found also in wells west of Minnesota and and east of the Rocky Mountains. Generally the granite is regarded as pre-Pennsylvanian and possibly pre-Cambrian. Gardner states that there is Uttle or no metamorphism of the overljdng sediments. Possibly some of the granite is Carboniferous or later, however, for Twenhofel found at the Silver City dome, Woodson County, Kansas, in the matrix of a limestone breccia, crystals of hornblende, epidote, and chlorite, suggesting the presence of an igneous rock near by.

The structure of the Appalachian Mountains resembles that of the Ouachita element in many respects,' and it has been suggested that the two areas are connected below the beds of Mississippi embayment by strata having similar structure. This correlation is not certain for the regions of intense deformation, because the mountain areas differ in strike. Both regions, however, are parallel

Gardner, J. H. : Mid-Continent Oil Fields. In Geol. Soc. America , vol. 28, p. 691, 1917.

*TwBNHOFEL, W. H. I The Silver City Quartzites. Geol. Soc. America , vol. 28, pp. 419-430, 1917.

Branner, J. C. : The Former Extension of the Appalachians Across Mississippi, Louisiana, and Texas. Amer, Jour, Sci, Series 4, vol. 4, pp. 357-371,

Appalachian, Lima-Ind,, And Mich. Fields 201

to the ocean deeps to the east and south and are evidently related in a broad way to them. There is, moreover, toward the lowland interior a continuous belt of less intense deformation, that is probably related to the mountain areas.

The correlation of Appalachian folds with those that strike through Kentucky was. first brought out by Gardner, who reviewed the work of other investigators, among them Campbell, Orton, Mimn, Muller, and Glenn. Later Reger, of the West Virginia Geological Survey, investigated the same structural features. He agrees that the Rough Creek uplift, the Irvine- Campton anticline, and the Chestnut Ridge anticline are in the same belt of deformation (Fig. 90). The Ozark uplift of Missouri appears to be connected by a belt of deformed rocks with the Appalachian Plateau, suggesting that the greater segments to the

f

h /

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Fig. 90. — Sketch map showing axes of deformation west of the Appalachian Mountains, and north of the Ouchita Mountains. {Data from Gardner, Siebenthai, and others.)

south — the Ouachita Mountains of Oklahoma and Arkansas — may be connected with the Appalachian Mountains, which he east of the Appalachian Plateau. As Siebenthal' shows, the Ozark axis extends into northeastern Oklahoma. (See Fig. 91.)

Gardner, J. H.: A Stratigraphic Disturbance Through the Ohio Valley Running from the Appalachian Plateau in Pennsylvania to the Ozark Mountains in Missouri. Geol. Soc. America Bull., vol. 26, pp. 477-483, 1915.

'Regeb, D. B. : The Possibilities of Deep-Sand Oil and Gas in the Appalachian Geosyncline of West Virginia. Am. Inst. Min. £ng. Trans. vol. 56, p. 856, 1916.

'SiEBENTHAL, C. E.: Origin of the Lead and Zinc Deposits of the Joplin Regions. U. S. Geol. Survey Bull. 606, p. 34, 1915.

Geology Of Petroleum

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Appalachian, Lima-Ind., And Mich. Fields 203

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Geology Of Petroleum

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Geology Of Petroleum

Igneous intrusive rocks are found at a few places along the line of deformation. Basic igneous rocks, generally as dikes, are found in Ste. Genevieve County, Missouri, intruding the Cambrian* between the area of pre-Cambrian rocks of the Ozarks and the Bald Hill uplift of southern Illinois. An area containing basic dikes and fluorspar veins is found in southern Illinois and western Kentucky.* Basic dikes are found also in eastern Kentucky, in southwestern Pennsylvania,* and in central New York.*

Fig. 91. — Map showing deformation of part of Ozark uplift. Figures on contours represent approximate elevation of base of Mississippian limestone above sea level; parts shaded with diagonal lines represent areas in which Pennsylvania shale is at the surface; areas with strokes and dots represent exposures of crystalline rocks.

Buckley, E. R. : Lead and Zinc Deposits of the Ozark Region, in Types of Ore Deposits, p. 105, San Francisco, 1911.

'XJlrich, E. O., and Smith, W. S. T.: The Lead, Zinc, and Fluorspar Deposits of Western Kentucky. U. S. Geol. Survey Prof, Paper 36, p. 26, 1905.

DiLLER, J. S. : Peridatite of Elliot County, Kentucky. U. S. Geol. Survey BuU, 38, pp. 1-29, 1887.

*HiCE, R. R. : Pennsylvania Geol. Survey Biennial Rept., 1910-12.

Blackwelder, Eliot: Op. ciL, p. 117.

Appalachian, Lima-Ind., And Mich. Fields 205

West of the Appalachian Mountains, in the great Appalachian geosyncline, there are many parallel folds. Most of these strike northeast, parallel to the Appalachian Mountains. The Burning Springs-Volcano anticUne, in West Virginia, however, strikes north, making a large angle with other Appalachian folds. This anticline is shorter but much steeper than the neighboring folds.

The Warfield-Campton-Rough Creek-Bald Hill-Ozark axis of deformation has been mentioned. It is probably the most persistent structural feature of the lowlands element. The LaSalle anticline of Illinois, the anticline that extends from the Black Hills into Kansas, and the Glendive anticline of eastern Montana and western North Dakota are noteworthy features.

The great synclines of the interior lowlands are the Appalachian geosyncline, the basin of the southern peninsula of Michigan, the Illinois-Indiana-Kentucky coal basin, and the great geosyncline lying east of the Rocky Moimtains, extending to Minnesota, Iowa, Kansas, and Oklahoma.

Besides the folds already mentioned there are a number of smaller imdulations in the interior of the lowland region, where the beds rise in domes, anticlines, and anticlinal noses. Such folds have supplied the gathermg grounds for petroleum and gas in many of the oil fields.

Faults are not nimierous in the interior lowlands, except in certain local areas. In western Kentucky and southern Illinois they are closely spaced in the fluorspar region along Ohio River. Faults are found also in the oil fields of eastern Kentucky. In the oil region- of Oklahoma faults of small throw are not uncommon, and in the eastern part of Oklahoma, in Cherokee, Adair, and Sequoyah Counties, faults with considerable throw are rather closely spaced. A few faults have been discovered also in the Joplin region, Missouri; in northeastern Oklahoma; and in the Sabine uplift, Louisiana and Texas. On the whole, however, the rocks of the interior lowlands are very gently deformed. This lowland region contains, indeed, one of the largest bodies of Paleozoic strata of the earth that has undergone so little deformation.

The Paleozoic strata of the lowlands are consolidated, but they are not much metamorphosed by pressure. They consist principally of shales, sandstones, and limestones. Muds, sands, and marls are generally lacking. Nowhere, except near the mountain

206 Geology Of Petroleum

uplifts are pronounced secondary Btructural features developed in the shales. They are rarely slates or schists. The sandstones may be locally altered to quartzite, through infiltration and cementation. The limestones are generally recryetallized somewhat, but away from the mountains they show very little evidence of deformation by pressure.

APPAIACHIAM on, field'

General Features.— The Appalachian field includes all the oil and gas producing districts in the United States east of central Ohio and northeast of central Alabama. These districts are in New York, Pennsylvania, West Virginia, southeastern Ohio,

Fig. 92. — Sketch showing the areal geology of part of the Appalachian geoeyncline; 11, Permian; 12, PennsylvanJan; 13, MissisEippian; 14, Devonian: 15, Silurian; 16, Ordovician, (After WUIm.}

Kentucky, Tennessee, and northern Alabama. This field, which was the first great oil field in the world to be extensively developed, still produces about 25,000,000 barrels annually.

Surface indications of oil are not numerous, although they are oresent at several places. Noteworthy among them are Oil

Appalachian, Lima-Ind., And Mich. Fields 207

Spring, Allegany County, New York; Oil Creek, Venango County, Pennsylvania; the gas seep at Burning Springs, Wirt County, West Virginia; and the grahamite dike in Ritchie County, West Virginia. The oil from seeps was gather'ed by Indians and by early settlers and used for medicinal purposes. In the early days oil was encountered in small amounts in many wells sunk for brine, but it was not generally regarded with favor because there was little use for it.

The Appalachian field is a great geosyncline that lies west of the

Fig. 93. — Structure contour map of part of the Appalachian geosyncline, showing contours on the Big Injun sand. (After Reeves,)

Appalachian mountain front and extends from southwestern New York to northern Alabama. On the west the strata rise to the Cincinnati geanticUne in Ohio, Kentucky, and Tennessee. The field is somewhat larger than the Appalachian coal basin, although some of the most productive parts of it are below the area occupied by that basin. A comparatively small portion of it yields oil. Puller estimates the oil-bearing areas to be as follows:

Fuller, M. L. : Appalachian Oil Field*. Geol. Soc. America Bull., vol. 28, p. 646, 1917.

Geology Of Petroleum

Area op Appalachian Oil and Gas Pools, in Square Miles

New York

Pennsylvania

West Virginia. . . . Southeastern Ohio

Kentucky

Tennessee

Alabama

ou

Gas

The strata that yield oil or gas in the Appalachian field (Fig. 92) include those of the Cambrian, Silurian, Ordovician, Devonian, and Carboniferous systems. The pools occur generally on axes and flanks of anticlines, parallel with the strike of the Appalachian Mountains, on minor terraces or other structural features associated with them, and in water-free sjmclines. The reservoir rocks are mainly sandstones or conglomerate layers. An exception is the Big lime (Greenbrier limestone), which contains oil in West Virginia.

The Paleozoic rocks of the region are mainly shales, sandstones, and limestones. The general structure is shown by Fig. 93. The contour interval on this map is not small enough to show the details of folding. The map does show, however, the great Burning Springs-Volcano anticline, in western West Virginia. Unlike the other minor folds of the geosyncline, which strike northeast, the Volcano fold strikes nearly north, across the regional strike of the country. (See also Figs. 97 and 98.) A section from eastern Ontario southward to West Virginia is given in Fig. 94. The strata vary in character so that a section taken at one place differs considerably from other sections. There are, however,

certain persistent and fairly constant strata that can be correlated.

) The Pittsburgh coal lies near the surface over much of this area.

It is a persistent member and because of its value its position has been determined with great accuracy. It therefore serves as a horizon marker and a key rock to the structure. Below the Pittsburgh coal are other coals, which also serve as keys to the structure. The section containing the coals is made up principally

Appalachian, Lima-Ind., And Mich. Fields 209

of sandstones, shales, and limestones. Another horizon marker is the Salt sand, which is the top of the Pottsville formation. Below the Salt sand is the Big lime. The Big Injun sand lies below the Big lime, and below it are the Gordon, Elizabeth, Bradford, and other sands. A section of the rocks is shown in Fig. 95. Other sections are given on pages 213 and 215.

Correlations in thb Appalachian Fibld (After Fuller; Figures Indicate Thickness in Feet)

Permian

o §

Peimsylvaniftn

Miasissippian

Penosylvania

and Northern

West

Virginia

(Rogersville

Folio,

Clapp) .

Upper barren

Upper productive

Lower barren

Lower productive

Conglom* erate

Southern

West Virginia (Buckhannon Folio, TafiF and Brooks)

Punki, 1100 ,

Mononga- h

hela, 400

Conemaugh.

Allegheny,

Pottsville,

Kentucky (London

Folio, Campbell)

'

Braxton, ' 700

Upshur,

Pugh.

Pickens,

Mauch

Greenbrier,

Pocono,

Devonian

Total

Catskill,

±

Chemung

Hamilton, kL 3500

Canaan

shale,

Lower coal

measures,

ijce,

Greenbrier

First,

Pocono,

Hampshire,

Pennington,

Tennessee

(Briceville

Folio,

Keith)

Coal

measures

(not

correlated),

Alabama, Warrior Coal Field (Birmingham Folio, Butts)

Lee,

Newman,

Waverly,

Jennings, 800 -t-

Qiattanooga

shale,

Pennington,

Newman,

Pottsville,

Pennington,

Greenbrier,

CSiattanooga

shale,

Chattanooga shale, (Frog Mountain sandstone?)

r

Geology Of Petroleum

New York, PenasylTania and West Virginia. — The great Appalachian syncHnorium is about 800 miles long. It is over 200 miles wide at the northeast end and 50 miles or less at the southwest end. The synclinorium embrace many minor anticlines and aynclines, which are of considerable amplitude in the eastern part of the £eld, near the mountains, but gradually die out or become flatter toward the northwest. Noteworthy folds are the Burning Springs-Volcano-Eureka anticline (Fig. 36, p. 131), the Wick anticline, the Arches Fork anticline, and the Chestnut Hidge and Laurel Hidge anticlines. In southern West Virginia the subordinate folds become less pronounced toward the northwest, the beds rising gradually toward the west, where they are exposed at the Cincinnati anticline in Ohio, eastern Kentucky, and eastern Tennrasee. As a rule the dips are gentle, commonly lees than 3°. Locally the strata, dip at higher angles, and exceptionally, as on the flanks of the Burning Springs-Volcano anticline, the dips rise to 10" or 20° or more. In New York, Pennsylvania, West Viiinia, and Ohio there is very httle faulting in the oil fields. In eastern Kentucky and Tennessee faults of, considerable magnitude are present.

Where the rocks are saturated with salt water, as a general rule the oil and gas occupy the anticlines, terraces, or domes, and the gas rises above the oil. According to Griswold and Munn,* this is true of deposits in the Salt sand and in the Big Injun sand below it, which belongs to the Focono of the

'Griswold, W. T., and , W. J.: Geology of Oil and Gas Fields in Steubensville, Burgettstown, and Claysville Quadrangles, Ohio, West Virginia, and Pennsylvania. U. S. Geol. Survey BvH. 318, 1907.

Appalachian, Lima-Ind., And Mich. Fields 211

Mississippian, The Btill lower Catekill sands are not fully saturated, and some of them are dry. The oil apparently has been let down from the higher structural poBitions ajid in some places is held up on the flanks of eyncUnes by water that remains in the beds. (See Fig. 63, p. 154). If no water remains the oil will be at

West Virgmia. (AJter Clapp.)

the bottom of the folds. The water content of the reservoir strata in the region south of Pittsbui a few years after Griswold and 'B examination was investigated by Reeves.' The Catskill, iResves, Fiukk: Absence of Water in Sandstones of the Appalachian Oil Fields. Earn. Gednry, voL 12, pp. 254-278, 1917.

212 Geology Of Petroleum

which is a terrestrial phase of the Devonian, is developed over a considerable area. It is a series of red shales and thin reddish or white sandstones. Eastward along the outcrop, the formation consists of 600 to 900 feet of alternating layers of shale and sandstone, red and green, which are unfossiliferous and in places sun-cracked and ripple-marked. The shale contains about 6 per cent of ferric oxide. These sands are not saturated.

Many wells in this field produce both oil and gas, and some produce both from the same stratimi. In many wells the gas carries considerable gasoline. In 1917, according to Northrop,* West Virginia marketed 32,668,647 gallons and Pennsylvania marketed 13,826,250 gallons of gasoline derived from natural gas.

Many of the folds yield gas only, and in general such folds lie east of the petroleum-bearing folds and nearer to the Appalachian Moxmtains. Where dynamo-chemical alteration has been sufficient to alter the coals so that they have a high carbon content, gas only is produced. This relation was first pointed out by David White' and was further developed by Fuller.* According to Fuller the occurrence of 65 to 70 per cent of fixed carbon in pure coals establishes a sort of dead line as regards commercial deposits of oil or gas. Where coals range from 60 to 65 per cent of fixed carbon, gas may be found in quantity, but little commercial oil. Where coals range from 56 to 60 per cent of fixed carbon, oils are found in abundance, with abundant gas. In the west part of the Appalachian field carbon ratios are lower. Some of the oil lies east of the gas.

The first serious attempt to develop the petroleum industry in the northern Appalachian region resulted from the drilling of a well ai Titusville, Pennsylvania, by E. L. Drake in 1859. Although it was not a large well, there was a sale for the oil and other wells were drilled, opening many oil pools. The first flowing well or gusher was one sunk near Rouseville in 1860, and several others yielding from 3,000 to 4,000 barrels a day were brought in

Babrell, Joseph: The Upper Devonian Delta of the Appalachian Geosyncline. Am. Jour. Sci., 4th ser., vol. 36, pp. 429-472, 1918; vol. 37, pp. 87-109, 225-253, 1914.

'Northrop, J. D.: U. S. Geol. Survey Mineral Resources, 1917, part 2, p. 1119, 1919.

'White, David: Some Relations in Origin Between Coal and Petroleum. Washington Acad. Sci. Jour. vol. 5, pp. 189-212, 1915.

Fuller, M. L.: Geol. Soc. America BtK., vol. 27, p. 649, 1917.

Appalachian, Lima-Ind., And Mich. Fields 213

i'-

Series

Oolamnar Motion

rhickneii

Total (feot)

Deaorlption

s

g

Uqo

Tarlcgated ibalea and gray landitonai with a faw thin coal beda

s

E

Mononsahela (Pittsburgh coal at base )

Qrajr iandtoai. gray ahafea, limoitonei, aii4 coal boda

Oonenutasli

21S0

Gray or brown aanditouefa gray and red ahalca, and coal bdi

Allecheny

Gray landitonoi, gray abaloi, and coal bedi

Sco

Mauch Chunk

4a

(Gordon group of oil aaadi)

Ohemimg

(Ho prodactlTe aanda in Weal Virginia)

Portase

(No productlTe aanda

in Weat Virginia)

Hamilton

(No prodactlTe aanda in Weat Virginia )

"llaroellns or Uomney 9m 1m OMo mad Katotkj

Unondasa" limeatone'

Orlakany

Salina, and Klagan

(Big lime of Ohio)

Olinton

edina wblte aaudatone OIlBlwi aO iMid ai Otto)

Medina shales

Martinsbnis or Olnolnnatl ahale (OntalM Bntoa mbA

) '4

Utioa

Trenton and other limeatonei (Oil and gai borison Of Boithara Ohio)

s&

ss

1S00(?)

800(?)

Ttt

r=c

:S

Ttt

50(?) 150(?)

5S

Ttt

X±Dc

s

Ttt

sas

3=r

i±r

1 ! I

Pia.

J

rrc

rzx

air

700(?)

300(?)

50(?)

SOOf?)

iaoo(?}

Gray landAtonea, and ahalei, with a few coal badi

Bed ihalDB with a few thin undatonei

Gray candatonea and gray ibalea

Brown landatonei and red ibalea

ahalei with aandatonai lantili

Gray ihalea with aabdatonei lentUa

Brown, ibalea with aandatone lentils

Brown, or black bilQaBlnoaa balaa with aanditone lentils

Dark flinty llmeitone

Gray aanditone

Limeatone

Variegated chalet

White landitone

Bed ibalea and thin landitonoB

Gray ifaalei with aandatone leutila

Black ahalei with landatone lentils

Limsitonea

96. — Columnar section for central part of West Virginia oil fields, Marion and surrounding Counties. {After Reger.)

P,

Geology Of Petroleum

during 1861. Development in this region thereafter was rapid, reaching a maximum in 1891, from which it has slowly declined. The oil is of high grade, is rich in lighter derivatives, has a paraffin base, and is essentially free from sulphur.

The most productive portion of the Appalachian field lies in New York, Pennsylvania, and West Virginia. Geologic sections

Fig. 97.— ;-Map showing axes of folds in part of Appalachian geosyncline. For sections along lines A-A', etc., see Fig. 98. (Baaed on map by Reger.)

for Pennsylvania and West Virginia are given in Fig. 95 (p. 211), and for the central part of the West Virginia in Fig. 96. The trends of the principal folds in these States are shown in Fig. 97, and cross sections are given in Fig. 98. The distribution of oil and gas pools in New York and Pennsylvania is shown by Fig. 99 and in West Virginia by Fig. 100.

Appalachian, Lima-Ind., And Mich. Fields 215 I I !

Fig. 98. — Croas-sectiona showing position of folds in part of Appalachian b synohne. For of sections, see Fig. 97. {A/Un- Ier.)

Geology Of Petroleum

In New York the greater part of the oil is derived from the Bradford sand, in the Chemung formation, or from other sands not far above or below it. Gas is produced from the Comif erous limestone of the lower Devonian; from the Guelph limestone, Niagara

Gas

Fio. 99. — Map of oil and gas producing areas of northern Appalachian region.

{After Munn.)

limestone, and Medina sandstone of the Silurian; from the Trenton limestone and Lorraine shale of the Ordovician; and from the Potsdam sandstone of the Cambrian.

Appalachian, Lima-Ind., And Mich. Fields 217

In the Pennsylvania-WeBt Virginia area oil is found both above and betow the Pittsburgh coal in the Penusylvanian aeries, and in the Mississippian and Devonian. Oil is produced from the Kane sand, in the Chemung, 3,770 feet below the Pittsbui coal. (See p. 219.) Spme of the formations that produce gas in New York will

Fia. 100. — Map showing principle oil-producing areas in West Virginia.

probably be found productive in Pennsylvania and West Virginia, where these formations lie at great depth.

The principal oil horizons in the Pennsylvanian and West Virginia districta are stated on pages 218-219.

218 Geology Of Petroleum

Oil Hobizonb of Pbmnbtlvanu- Virginia Disthict"

Carboniferous: ., ,

Distance Above ( +)

Pennsylvanian : or Below ( -) the

Pittsburgh Coal.

Monongahela formation (Upper Productive measures) : in Feet

Carroll sand (Uniontown sandstone), productive in West Virginia only + 300

Pittsburgh coal horizon.

Conemaugh formation (Lower Barren measures) :

Murphy, Shallow, Little Dunkard, or First Cow Rim sand

(Saltsburg sandstone) — 200

Big Dunkard or Cow Run sand (Mahoning sandstone) 500

Allegheny formation (Lower Productive measures) :

Second Cow Run sand (Freeport sandstone) — 600

Gas sand. — 800

Pottsville formation (Salt sand) :

Johnson Run sand (Homewood sandstone) - 900

Upper Salt sand (Lower Conoquenessing sandstone) — 950

Middle Salt sand (Lower Conoquenessing sandstone) -1,050

Lower salt (Sharon conglomerate) -1,150

Mississippian:

Mauch Chunk formation:

Maxton or Cairo sand (of West Virginia) -1,200

Greenbrier limestone (Big Hme) —1,250

Pocono formation (Big Injim sand):

Keener sand —1,300

First, Second, and Third Pay sands (Top) -1,400

Squaw sand —1,450

Wier sand -1,500

Upper Gas sand —1,550

Berea or Thirty-foot sand -1,750

Murrysville or Butler sand —1,800

Gantz, First, or Hundred-foot sand* -1,850

'Fuller, M. L.: Appalachian Oil Fields. Geol. Soc. America Bull. vol. 28, p. 633 1917. See also Clapp, F. G.: Outline of the Geology of Natural Gas in the United States. Earn. Oeology, vol. 8. pp. 520-521, 1913.

Rbgeb divides the Mississippian into Mauch Chunk, Greenbrier, and Pocono. See "Big. 96.

'FtTLLEB places the Upper Gas, Berea, Butler, and Hundred-Foot sands in the Catskill. Following recent United States Geological Survey practice here, I have placed -them in tiie Mississippian. — (W. H. E.)

Appalachian, Lima-Ind., And Mich. Fields 219

Devonian:

Catskill formation:

Fifty-foot sand -1,900

Nineveh, Thirty-foot, or Second sand -2,000

Gray, Gordon Stray, or Boulder sand -2,100

Gordon, Third, or Campbells Run (?) sand -2,150

Fourthsand (Gordon of West Virginia?) -2,20b

Fifth, sand (McDonald of West Virginia?) . , , . , . -2,250

; Bayard sand 7. . . . -2,400

emung formation:

' Elizabeth ox Sixth sand -2,600

I Warren First sand -2,700

; Warren Second sand -2,800

; Tiona sand. -2,900

I Speechley sand -3,000

Balltown or Cherry Grove sand. , . . . -3,120

i Sheffield or Cooper sand r -3,20

I Bradfordsand ,..'. .,:... -3,

j Second Bradford sand / -3,480

I Elk sand. -3,650

f Kane sand. -3,70

In southwestern Pennsylvania and northwestern West Virginia the sands in the Upper Devonian contain much oil and gas. Thee sands constitute the Venango oil-sand group, which is an importaiit oit-beiairing series in southwestern Pennsylvatiifi. Below the Catskill the Comiferous limestone is found at great depths in this field. A j well iear McDonald, Pennsylvania, penetrated the Lower Devonian limestone. At a depth of 6,260 feet a sandstone, possibly the Oriskany, was encountered which contained coiicentrated brine. Reeves states that the C9.skill sands are free from salt water because they were laid down under arid conditions. According to Reeves they have never been saturated with water, althou the marine sediments both above and below are saturated brine.

In matic of the oil sands the oil and gas occur in pockets, where

the sands are coarser (p. 115). In the Carboniferous rocks, which

are generally saturated with water, the oil at many places is on

high parts of the folds. A well-known example is the Volcano

dome of the Burning Springs-Volcano-Eureka anticUne in West

Virginia.

*Whitb, I. C. : Note on a Very Deep Well Near McDonald, Pennsylvania. Geol. Soc. America BuU., voL 24, pp. 275-282, 1913.

Geology Of Petroleum

The occurrence of oil and gas on anticlinal noses and terraces has been noted.

Because of its great gas production (see p. 142), extensions east* ward of the ''Clinton" sand have aroused much interest. The sand dips eastward from central Ohio at a low angle and rises again toward the west front of the Appalachian Mountains. As stated

Fio. 101. — Map showing location of certain wells and, by contouTB, the )proximate thicKness of tne Upper Devonian in part of the Appalachian oil

approximate tnicKness ot tne upper

field. (Redrawn from a map by /. C. White.)

by Bownocker, the small oil pools found in the sand contain no water, and he suggests that they may occur in small shallow basins rather than on anticlines. It is believed by some that large

Appalachian, Lima-Ind., And Mich. Fields 221

depoeits of oil will be found the gas in the deeper part of the basin. Many deep wells have been sunk in the Appalachian basin, but in the central part of the basin none of them have penetrated the "Clinton'' sand. These wells supply information concerning the strata in a large part of the Appalachian' field.

Fig. 101, after White, is a sketch showing the thickness of the Upper Devonian. The strata are measmd between the Berea sand and the top of the Comiferous limestone. The Upper Devonian shales are only 500 feet thick in the region near Columbus, Ohio, but their thickness becomes very great toward the central part of the basin. At the Martha O. Goff well, in northern West Virginia, which is one of the deepest wells in the world, the Upper Devonian is nearly 6,000 feet thick. The formations encountered in this well, below the Pittsburgh coal, which before erosion was not far above the casing head, are shown in the following table:

Depth

'Mississippian

Pittsburgh coal, base of Monongahela series

Conemaugh series 600M

Allegheny 290 yPennsylvanian

Pottsville 260 I

Mauch Chunk 260'

Mountain (Greenbrier) limestone. 65

Big Injun, Squaw, and Berea sand group 265

CatskUl, containing Venango oil sand group, to base of Bayard oil sand 770'

Chemung shales, containing Elizabeth, Speechley, Bradford (Benson) and Kane oil sands 2.190

Portage beds 1 .207

Genesee slate 288

Hamilton and Marcellus 1 ,368

Comiferous limestone to present bottom

Upper Devonian shales

7,686

Whitb, I. C. : Discussion of the Records of Some Very Deep Wells in the Appalachian Oil Fields of Pennsylvania, Ohio and West Virginia. West Virgim'a Geol. Survey County Repts,, Barboiir and Upshiir Counties, pp. xxv-lxv,

222 Geology Of Petroleum

The record of the well is stated : '

Native coal (Elk lick) 83- 86

Little Dunkard sand 170- 186

Big Dunkard sand , 305- 336

Gas sand 436- 446

First Salt sand 690- 815

Second Salt sand 860- 880

Maxton sand 1,025-1,040

Little lime 1,183-1,194

Pencil cave 1,194-1,210

Big lime; gas at 1,253 feet 1,210-1,275

Big Injun sand; water at 1,304 feet 1,275-1,394

Squaw sand 1,410-1,428

Berea sand. 1,612-1,640

Gantz sand consolidated with Fifty-foot

Fifty-foot sand; gas at 1,749 and 1,757 feet 1,748-1,886

Thirty-foot sand 1,900-1,980

Gordon Stray sand 2,090-2,097

Gordon sa4d 2,130-2,142

Fourth sand None

Fifth sand None

Bayard sand 2,300-2,310

Slate shells 2,310-2,830

Hard lime 2,830-2,893

Slate and lime shells . 2,892-3,125

Hard Ume 3,125-3,145

Slate shells 3,145-3,222

Hard lime 3,222-3,240

Slate shells 3,240-3,480

Hard sand 3,480-3,505

Slate 3,505-4,166

Lime shells (Benson sand) ; with puff of air (gas) 4,166-4,167

Slate 4,167-4,425

lime 4,425-4,500.

Slate and shells 4,500-4,790

Lime 4,790-4,850

Slate shells 4,850-5,200

Slate shells at ' 5,700

Slate shells at 6,775

Dark slate 5,840-5,996

Lime shells 5,995-5,998

Dark slate 5,998-6,210

Lightslate 6,210-6,235

Lime 6,235-6,265

Dark slate 6,265-6,272

Lime 6,272-6,280

White, I. C. : Op. cit.y pp. Ivi-lviii.

Appalachian, Lima-Ind., And Mich. Fields 223

Dark slate 6,280-6,294

Lime 6,294-6,304

Dark date 6,304-6,318

Lime 6,318-6,330

Dark slate 6,330-6,360

Lime 6,360-6,380

Dark slate 6,380-6,385

Lime 6,385-6,395

Dark slate 6,395-6,420

Lime 6,420-6,426

Darkslate 6,426-6,438

Lime 6,438-6,447

Darkslate 6,447-6,465

Lime 6,465-6,470

Darkslate 6,470-6,500

Blackslate. 6,500-6,505

Black lime. 6,505-6,510

Blackslate 6,510-6,532

Darkslate 6,532-6,580

Darkslate 6,580-6,625

Hard shells 6,625-6,627

Brown shale 6,627-6,640

Hard shells 6,640-6,645

Blackslate 6,645-6,660

Blackshale 6,660-6,676

Blacksand 6,676,680

Hard lime 6,680-6,690

Darkslate 6,690-6,714

Darklime 6,714-6,747

Hard shell! 6,747-6,750

Slate ' 6,750-6,755

Dark slate 6,755-6,775

Hard sand sheUs." 6,775-6,780

Blackshale 6,780-6,800

Blackslate 6,800-6,823

Hard lime 6,823-6,865

Slate widshells 6,865-6,950

Hard Ume 6,950-7,057

Lime sheUs 7,057-7,069

Hardsand 7,069-7,071

Hardlime 7,069-7,075

Lime 7,081-7,093

Hard lime 7,093-7,097

Hard lime 7,097-7,110

Slate and sheUs 7,110-7,150

Slate 7,150-7,160

Hard lime 7,160-7,162

Geology Of Petroleum

lime Bhells 7,162-7,176

Gritty shells 7,176-7,190

Slate 7,190-7,225

Slate 7,225-7,232

Hard aheU 7,232-7,245

Blackelate 7,245-7,251

Slate and shells 7,251-7,256

Hard lime 7,256-7,261

Darkhardlime 7,261-7,266

Blackslate 7,266-7,280

Hard shells 7,280-7,282

Slate 7,282-7,290

Soft slate 7,290-7,295

Soft black slate 7,295-7,300

Black slate 7,300-7,345

Gritty lime 7,345-7,363

Hard flinty limestone, Corniferous, to bottom. . 7,363—7,386

The R. A. Geary well at McDonald, Pennsylvania, west of Pittsburgh, was described by White* in 1913. The record is summarized as foUows, beginning at the base of the Pittsburgh coal, the horizon of which is estimated to be 130 feet above the derrick floor:

Conemaugh series 58Q'

Allegheny series 284 ) Pennsylvanian

Pottsville series 216

Mauch Chunk 3'

Big lime (Mountain, Greenbrier). 29 Mississippian Big Injun, Squaw, and Berea sands. 640 .Catskill, (including Venango oU-eand group), Chemung,

Portage, Hamilton, and Marcellus beds

Corniferous limestone

Oriskany sandstone

Helderberg

Salina salt series

Salina shales and Niagara (Clinton?)

Thickness

Feet

1,080

Depth

Feet

Whitb, I. C. : Note on a Very Deep Well Near McDonald, Pennsylvania, Geol. Soc. America BvU.y vol. 24, pp. 275-282, 1913.

Appalachian, Lima-Ind., And Mich. Fields 225

The Upper Devonian is 4,386 feet thick, which is somewhat thinner than in the Goflf well.

Eastern Ohio. — In Ohio there are three fields that produce oil or gas or both. In an extension of the Appalachian field in eastern Ohio the petroliferous strata developed in western Pennsylvania and West Virginia are present. West of this belt is the "CUnton" sand field, which yields much gas. Still farther west and extending into Indiana is the great Lima-Indiana field, in which oil and gas are derived from the Trenton limestone. This is not classed with the Appalachian oil fields but is related to the Cincinnati arch, which lies west of the Appalachian basin.

Principal Oil-Producing Rocks in Ohio and Indiana

(After Bownocker)

I Mitchell sand (Ohio). Macksburg 140-ft., or first Cow Run sand (Ohio). Macksburg 500-ft. sand (Ohio).

Mississippian. . . .

Huron sandstone (Indiana). Keener sand (Ohio). Big Injun sand (Ohio). Berea sand (Ohio).

Devonian Comiferous limestone (Indiana).

Silurian ''Clinton" sand (Ohio).

Ordovician Trenton limestone (Ohio and Indiana).

In eastern and southeastern Ohio oil and gas are found in low folds in Pennsylvanian and Mississippian rocks. The producing counties extend almost across the eastern part of the State. Monroe and Washington Counties have been the largest producers. The pools are numerous, but most of them are small, not more than two or three of them including more than ten square miles. Thousands of wells have been drilled. So many tests have been made that the chances of discovering large reservoirs are slight, and, according to Bownocker, the production of 5,586,433 barrels in 1903 will probably stand as the maximum.

iBowNOCKBB, J. A. : Petroleum in Ohio and Indiana. Geol. Soc. Americi ., vol. 28, pp. 667-67G, 1917.

Geology Of Petroleum

GENisitAiiiZBD Section of Cabbonifbbous Formations in ESabtern Ohio

(After Mills and Wells)

Group or FonnAtion

Waahington f ormation.'

Monongahela forination.

Gonemaugh formation.

Allegheny formation.

Pottsville formation.

-Unconformity Maxville limestone.

-Unconformity

Logan formation.

Black Hand formation.

Cuyahoga formation.

Sunbury shale.

Berea sandstone.

Thickness (Feet)

350-450?

Character

Non|>er8i8tent sandstone members with shale and clay of reddishbrown color. A few thin beds of coal ind limestone in lower portion.

Limestone, shale, and a littie sandstone. Contains the Pittsburgh, Pomeroy, Meigs Creek, Uniontown, and Waynesburg coal beds, all of more or less value in the Woodsfield quadrangle.

Driller's Description

Irregular members grading into shales, commonly of reddishbrown or variegated colors Upper and lower Httsburgh limestone members near top; Ames and Cambridge limestone members a little below middle. Mahoning sandstone member at the base, locally productive of oil.

Sandstone, shale, and important clay and coal beds, including the Lower Kittanning, Middle Kittwtining, and Lower and Upper Freeport.

Consists largely of sandstone and conglomerate, which rest with uneven contact on the eroded surface of the Mississippian beds. The sandstone is generally divided into several parts - by beds of clay shale, and coals also are locally present.

Dark-gray and bluish to light-gray limestone with interbedded shale and fine-grained sandstone.

Consists of sandstone, the Keener sand, interbedded with shale; a valuable source of oil and gas.

Includes First Cow Run, Buell Run, and Mahoning sands.

Includes Peeker, Macksburg 500-foot, and Second Cow Run oil sands named in descending order.

Includes Maxton sand.

Big lime; includes Big Ume sand.

Includes Keener oi sand.

Coarse sandstone interbedded with and grading laterally into sandy shale.

Mostly sandy shale in lower part, with a few beds of shaly sandstone.

Dark carbonaceous shale.

Berea sand, consisting of coarse to fine-grained gray to white sandstone. Lenticular in the Woodsfield and Summerfield quadrangles. Unconformity at base

Probably includes Big Injun and Squaw oil sands.

Includes Welsh oil sand.

Black shale.

Berea oil and gas sand.

'At places in eastern Ohio (he Greene formation of th Permian overlie the Washington.

Appalachian, Lima-Ind., And Mich. Fields 227

Gbnbrauzxd Sbction of Older Palbosoic Formations in Eastern Qmo

(After Rogen)

System

Group or Fomuttaon

Thickness (Feet)

Gharaeter

Driller's Description

Devonian or Carbonifer> out.

Bedford shale.

Mottled gray, reddish, and brownish shale.

O

CSeveland shale.

Massive hard black Intuminous, with a few bluish layers in lower portion.

Ohio shale, 1,100-8,000

treated as a unit in southcm Ohio.

Chsgrin shale.

850-1,200

Soft bluish-sray day shale, with some concretionary layers.

Deronian

Huron shale.

Black and bluish shale upper and lower portions, with a band of gray shale near middle.

OlentanicyT shale.

Gray calcareous shale.

Delaware limestone.

Blue and gray limestone, becoming dolomitio in lower part. Contains a 80 to 60- foot bed of white quarts sandstone, 360 to 460 feet below top.

Columbus limestone.

Big lime; includes Newburg sand and

Monroe formation.

some "stray" sands in lower

Salina formation.

400-00

Shale, dolomite, anhydrite or gypsum, and rock salt.

300 feet, 490- 1 ,826 feet.

Niagara limestone.

400-00

Dolomite and limestone.

BUurian.

"Clinton" formation.

Crystalline limestone of various light colors; calcareous shale and thin-bedded limestone, with sandstone layer in lower part.

Includes little lime, 75-150 feet.

"ainton" sand, 0-60 feet.

25-76 feet.

Medina shale.

Red clay shale, with thin layers of sandstone.

Medina red rock.

Shale and limestone of Cincinnatian ace.

760-1 ,250

Dark shale, with thin layers of limestone, especially in upper part.

Slate and shells.

Trenton (7) limestone.

(7)

Limestone.

Trenton lime.

228 Oeolooy Of Petroleum

One of the most persistent sands is the Berea, which lies near the lower part of the Mississippian, below the Sunbury shale and above the Bedford shale. The Berea yields gas or oil in several counties; its outcrop is practically continuous, and it is generally penetrated wherever the drilling is carried deep enough. Accumulations of oil and gas, as stated by Panyity, are found principally where the sand thins out up the dip. (See p. 145.)

In the Woodsfield quadrane, which includes parts of Behnont, Monroe, Noble, and Guernsey Counties, the rocks at the surface are of Pennsylvanian and Permian age and include in ascending; order the Conemaugh, Monongahela, and Washington formations. The dip or slope of the beds is in general southeastward. The most noteworthy productive sands, named in descending order, are the so-called Cow Run, Big lime. Keener Big Injun, and Berea. In the Bamesville oil and gas field, in the northwestern part of the Woodsfield quadrangle, the gas occupies the high portion of the anticlinal fold and is flanked by an oil-producing belt a little lower on the slope. The water table in the Berea sand is of local extent and probably has no relation to water tables in the same sand in other areas to the west and north. The partial saturation in this area does not signify that the quantity of salt water becomes less as the oil sand is followed up the dip. On the contrary, great quantities of salt water and also some oil are derived from the Berea all the way from the Woodsfield quadrangle northwestward to Wooster and beyond, where the sand is only a little below the surface.' The relations of accumulation to sands and water conditions, according to Condit, are varied and uncertain, although the productive belts in general follow structural contoims.

The Wooster region, in Wayne County, has recently been described by Bonine.* The Wooster field is a little west of the outcrops of the Pottsville and Allegheny formations (Carboniferous), which mark the northwestern limit of the Appalachian coal / basin. The rocks have a general dip to the east and southeast of

Pantitt, L. S. : Lithology of the Berea Sand in Southeastern Ohio, and Its Effect on Production. Am. Inst. Min. £ng. BuU. 140, pp. 1317-1320, 1917.

K>)NDiT, D. D.: Structure of the Berea Oil Sand in the Woodsfield Quadrangle, Ohio. U. S. Geol. Survey BvU, 621, p. 233, 1915. CoNDiT, D. D. : Op, cU,, pp. 246-246.

*BONiNB, C. A.: Anticlines in the "Clinton" Sand Near Wooster, Wayne County, Ohio. U. S, Geol. Survey BvU, 621, p. 95, 1915.

Appalachian, Lima-Ind., And Mich. Fields 229

about 50 feet to the mile. This dip has been flattened in many places, producing structural terraces. Cross folding of a more or less intense character has likewise taken place, producing folds at right angles to the strike of the formations. These folds are especially pronounced in the ''Clinton" sand and exist in a modified form in the Berea sandstone. The surface rocks near Wooster*are not well exposed, and consequently it is difficult to determine whether or not they are similar in structure.

The principal structural feature of the gas field is the steeply pitching anticline west and southwest of Wooster, along the crest and sides of which the gas has accmnulated.

The ''Clinton" gas field is one of the largest sources of natural 1/ gas in the world. In 1912 the output of natural gas in Ohio exceeded 56,000,000,000 cubic feet, and in 1913 it was 50,300,000,000 cubic feet. The value of the output in 1912 was nearly $12,000,000 and probably 90 per cent of this came from the "Clinton" sand. LThe name "Clinton" was early appUed to the gas sand at Lan- 'caster, Ohio, and it became well established. However, it was shown by Bownocker that the gas-bearing rock lies below the true Clinton formation and is of Medina age. Natural gas was discovered in this rock at Lancaster in 1887, and the field has been developed so that it now extends from the shore of Lake Erie southward almost to the Ohio River.

The position of the "Clinton" sand in deep wells is easily determined by the great Devonian and Silurian limestones (Big lime), the base of which usually lies from 90 to 150 feet above the sand. The sand itself Ues between shales. The "Clinton" sand is not everywhere present in this region. It is not found in the western half of Ohio. The sand thins out in the longitude of Columbus, and farther west its horizon is occupied by shales. The sand along its western border — that is, from Cleveland to Lorain and thence south to the Ohio River — is patchy and uncertain. The sand is thus a lens, or series of lenses, embedded in fine shales (see p. 143).

The thickness of the "Clinton" varies. Its maximum is placed by Bownocker at about 100 feet, but measurements of half that amount are known, and the usual thickness ranges from 10 to 40

'Bownocker, J. A.: Natural Gas in Ohio. Cleveland Engineering See. Bua,, vol 8, No. 6, pp. 322-332, 1916.

Geology Of Petroleum

feet. Its texture is rather coarse. The rock commonly has a light gray color, but in places it is brick-red. At many places it is impervious and barren.

Tlie initial pressure in the field was everywhere high and increases with the depth. In the southern part of the field it was about 700 pounds to the square inch; between Newark and Mount Vernon, 750 pounds; in Ashland County, 1,200 pounds; and in Cuyahoga County 1,050 pounds. The greatest pressure near Butler, Richland County, was 1,260 pounds.

The first large well in the "Clinton" was the Mithoff, at Lancaster, which yielded initially at the rate of 12,000,000 cubic feet a day. From Newark to Mount Vernon the largest wells yielded about 12,000,000 cubic feet, and in Ashland Coxmty 13,000,000 cubic feet. A well drilled in Congress Township, Wayne County, early in September, 1915, started flowing at the rate of 22,000,000 cubic feet a day. Many wells flow from 3,000,000 to 5,000,000 cubic feet.

Wells in the "Clinton" are long lived, for gas wells, as a result of the porous nature of the rocks and the high pressure of the gas. Difficulties in drilling are encountered because of brine in the Big lime, which lies a short distance above the gas rock. This brine 'has done great damage to many wells.

Record of a "Clinton" Oil Well Near Bremen, Fairfield Countt, Ohio

(After Bownocker)

Mantle rock

Cuyahoga and Sunbury sandstone and shales.

Berea sandstone

Bedford and Ohio shales

Devonian limestone

I Monroe limestone Niagara' limestone Clinton limestone

Shales %

"CUnton" sand ,

Bottom of well f,

Depth

Feet

1,735

Appalachian, Lima-Ind., And Mich. Fields 2Z1

Many wells have been drilled for oil in the "Clinton/* Oil in paying quantities was first obtained in this stratum in 1899, but no large pools were found until 1907, when the reservoir in eastern Fairfield County was discovered.

The oil, which has a density ranging from 35° to 46° Baume, I differs in no important way from the oils of Pennsylvania and West Virginia. Its occurrence is uncommon in Ohio, in that it appears to be free from water. From this fact the conclusion is reached that the oil Ues in shallow basins rather than on the slopes of anticlines. The production of the "CUnton" sand at its maximum was about 1,300,000 barrels a year.*

References on Appalachian Fields in New York, Pennsylvania, West Virginia

and Ohio

AsHBURNER, C. A. I The Production and Exhaustion of the Oil Regions of Pennsylvania and New York. Am. Inst. Min. Eng. Trans,, vol. 14, pp. 419- 427, 1886.

The Geology of Natural Gas. Idem, pp. 428-438.

Ashley, G. H., and Campbell, M. R.: Geologic Structure of the Punxsutawney, Curwensville, Houtzdale, Bamesboro, and Patton Quadrangles, Central Pennsylvania. U. S. Geol. Survey BviL 531, pp. 69-89, 1913.

BoNiNE, C. A.: Anticlines in the Clinton Sand Near Wooster, Wayne County, Ohio. U. S. Geol. Survey BuU. 621, pp. 87-98, 1916.

BowNOCKER, J. A. : Petroleum in Ohio and Indiana. Geol. Soc. America Bull, vol. 28, pp. 667-676, 1917.

Petroleum and Natural Gas in Ohio. Ohio Geol. Survey, 4th

ser., BuU. 1, 1903.

The Bremen Oil Field. Idem, BulL 12, 1910.

The CUnton Sand. Econ, Geology, vol. 6, p. 37, 1911.

Butts, Charles: Economic Geology of the Kittanning and Rural Valley Quadrangles, Pennsylvania. U. S Geol. Survey BuU. 279, pp. 1-198, 1906.

U. S. Geol. Survey Geol. Atlas, Rural Valley foUo (No. 125), 1906.

U. S. Geol. Survey Ged. Adas. Warren folio (No. 172), 1910.

and Leverett, Frank. U. S. Geol. Survey Geol. Atlas, Kittanning folio (No. 115), 1904.

Campbell, M. R. : U. S. Geol. Survey Geol. Atlas, Masontown-Uniontown folio (No. 82), 1902.

U. S. Geol. Survey Geol. AUas, Brownsville-Connellsville, folio

(No. 94), 1903.

Carll, J. F.: Oil-well Records and Levels. Pennsylvania Second Geol. Survey, vol. II, 1877.

BowNocKER, J. A. : Petroleum in and Indiana. Geol. Soc. America BiJl,, vol. 28, p. 672, 1917.

*BowNocKER, J. A.: Op. cit., p. 673.

232 Geology Of Petroleum

Carll, J. F. : Geology of the Oil Regions of WanenVeDangOy Clarion and Butler CountieSy Pennsylvania. Pennsylvania Second Geol. Surv, voL III, 1880.

Clapp, F. G. : U. S. Geol. Survey Geol. Atlas, Anaity folio (No. 144), 1907.

U. S. GeoL Survey Oed. AUaa, Rogeraville folio (No. 146), 1907.

Economic Geology of the Amity Quadrangle, Eastern Washington County, Pennsylvania. U. S. GeoL Siurvey BtdL 300, pp. 1-146, 1907.

The Nineveh and Gordon Oil Sands in Western Greene

County, Pennsylvama. U. S. Geol. Survey BvU, 286, pp. 262-266, 1906.

CoNDiT, D. D. : Oil and Gas in the Northern Part of Cadis Quadrangle, Ohio. U. S. CJeol. Survey BvU. 641, pp. 9-17, 1914.

Structure of the Berea Oil Sand in the Summerfield Quadrangle,

Ohia U. S. Geol. Survey BvU. 621, pp. 217-231, 1916.

Structure of the Berea Oil Sand in the Woodsfield Quadrangle,

Ohia U. S. Geol. Survey BvU. 621, pp. 233-249, 1916.

Fuller, M. L. : Appalachian Oil Fields. GeoL Soc. America BitU., vol. 28, pp. 617-664, 1917.

U. S. Ged. Survey Ged. AOaSy Gaines folio (No. 92), 1903.

The H3mer Gas Pool, Clinton County, Pennsylvania. U. S.

GeoL Survey BvU. 226, pp. 392-396, 1903.

Grimslet, G. p. : Petroleum and Natural Gas in the Panhandle Counties of West Virginia. West Virginia GeoL Survey County Repta., Ohio, Brooke, and Hancock Counties, pp. 238-274, 1906.

— Petroleum and Natural Gas in Pleasants, Wood, and Ritchie

Counties West Virginia GeoL Siu'vey County Repta., Pleasants, Wood, and Ritchie Counties, pp. 81-204, 1910.

Griswold, W. T., and Munn, M. J. : Geology of the Oil and Gas Fields in the Steubenville, Burgettstown, and Claysville Quadrangles, Ohio, West Virginia and Pennsylvania. U. S. GeoL Survey BvU. 318, pp. 1-196, 1907.

Hoeing, J. B. : The Oil and Gas Sands of Kentucky. Kentucky Geol. Survey BvU. 1, 1904.

HxTBBARD, G. D. : Gas and Oil Wells Near Oberlin, Ohio. Econ. Geology, vol. 8, pp. 681-690, 1913.

Matson, G. C: Water Resources of the Blue Grass Region, Kentucky. U. S. Geol. Survey Water-Supply Paper 233, pp. 1-233, 1909.

Mills, R. V. A., and Wells, R. C. : The Evaporation and Circulation of Waters Associated with Petroleum and Natural Gas. U. S. GeoL Survey BvU. 693, pp. 1-104, 1919.

Munn, M. J: U. S. GeoL Survey Ged. Alias, Sewickley folio (No. 176), 1911.

U. S. GeoL Survey Ged. Atlas, Claysville folio (No. 180), 1912.

Preliminary Report on the Oil and Gas Developments in Tennessee. Tennessee GeoL Survey BvU. 2-E, 1911.

Oil and Gas Fields of the Carnegie Quadrangle, Pennsylvania.

U. S. GeoL Survey BvU. 466, pp. 1-99, 1911.

Reconnaissance of the Oil and Gas Fields in Wayne and

McCreary Counties, Kentucky U. S. GeoL Survey BvU. 679, pp. 1- 106, 1914.

J

Appalachian, Lima-Ind., And Mich. Fields 233

Newland, D. H : The Mining and Quarry Industry of New York State, 1904. New York State Mus. Bml. 93, p. 943, 1905.

Obton, Edwabd: Petroleum and Natural Gas in New York. New York State Mus. Butt. 30, 1899.

Panyitt, L. S. : Lithology of the Berea Sand in Southeastern Ohio, and Its Effect on Production. Am. Inst. Min. £ng. BuU. 140, pp. 1317-1320, 1918.

The Southern Extremity of the Clinton Gas Pools iu Ohio. Am.

Inpt. Min. Eng. BuU,, June, 1917, pp. 963-966.

Reeves, FHank: The Absence of Water in Certain Sandstones of the Appalachian Oil Fields. Boon, Geology, vol. 12, pp. 354-375, 1917.

RiCHABDBON, G. B.: U. S. Geol. Survey Geol, Atlas, Indiana folio (No. 102),

Shaw, E. W., and Munn, M. J. : U. S. Geol. Survey Oeol Atlas, Burgettstown-Carnegie folio (No. 177), 1911.

Shaw, E. W., Lines, E. F., and Munn, M. J.: U. S. Geol. Survey Ged. Atlas, Foxburg-Clarion folio (No. 178), 1911.

Stone, R. W.: U. S. Geol. Survey Geol. AUas, Waynesburg folio (No. 121),

U. S. Geol. Survey Ged. AOas, Elders Ridge folio (No. 123), 1906.

Oil and Gas Fields in Eastern Greene County, Pennsylvania.

U. S. Geol. Survey BvU. 276, pp. 396-412, 1904.

and Clapp, F. G.: Oil and Gas Fields of Greene County, Pennsylvania. U. S. Geol. Survey BvU. 304, pp. 1-110, 1907.

Van Horn, F. R. : Reservoir Gas and Oil in the Vicinity of Cleveland, Ohio. Am. Inst. Min. Eng. Trans , vol. 66, pp. 831-842, 1917.

Whitb, I. C: Petroleum and Natural Gas. West Virginia Geol. Survey vol. la, 1904.

The Mannington Oil Field. Geol. Soc. America Bull., vol. 3,

pp. 187-216, 1892.

and others: West Virginia Geol. Survey County Repls,

WooLSET, L. H : Economic Geology of the Beaver Quadrangle, Pennsylvania. U. S. Geol. Survey BuU. 286, pp. 1-132, 1906.

Kentucky. — The rocks exposed in Kentucky* are Paleozoic, Cretaceous, and Quaternary. (See Figs. 102, 103.) The most prominent structural feature of this State is the Cincinnati anticline, which in Ohio and Indiana is termed the Cincinnati arch. (Seep. 201.) This anticUne extends southward from Cincinnati/ through east-central Kentucky and passes out of the State in thej eastern part of Monroe County. In Tennessee it expands into a great dome in the region of Nashville. From Tennessee it passes southward into Alabama.

HoEiNO, J. B. : Oil and Gas Sands of Kentucky. Kentucky GeoL Survey BvU. 1, 1904.

FoHS, F. J. : Oil and Gas Possibilities of Kentucky. Am. Inst. Min. Eng. BvU. 99, pp. 621-628, 1915.

Geology Op Petroleum

Appalachian, Lima-Ind., And Mich. Fields 2Z5

A zone of deformation knows In West Virginia as the Warfield anticline extends into Kentucky, where it is known aa the Campton anticline. (See Fig. 90.) This anticline crosses Kentucky from east to west and intersects the Cincinnati arch near the north border of Lincoln County.

The oldest formation in the State, the Mohawkian (Ordovician), ia ejcposed at the crest of this arch in Jessamine County. This portion has been termed the Jessamine dome. Around the Mohawkian ia a great area of. Cincinnatian rocks (Ordovician). Silurian, Devonian, Mississippian, and Pennsylvanian rocks occur in Buccession stratigraphically above the Ordovician central mass. The dip of the beds is essentially eastward to the West Virginia border; the Pennsylvanian coal measures in eastern Kentucky he on the west limb of the great Appalachian coal basin. In the coal region the rocks are thrown into gentle f olda like those in West Viiinia. West of the, Cincinnati antichne the bed dip westward below the western coal basin and rise again near th Cumberland River.

Most of the oil and gas pro-; duced in Kentucky* is derived' from Devonian Umestone, but some is obtained also from Ordo-

I1LL6ON, W. R. : The Oil and Gas Resources of Kentucky. Kentucky Dept. Geology and Poreatiy, sor. 5, voL 1, pp. 1-630, 1919.

Oeolooy Of Petroleum

f

i! f

t

Appalachian, Lima-Ind., And Mich. Fields 237

Field

1. Clover Port (g)

2. Rock Haven (g)

a Hartford (o)

4. Caneyville (o)

6. Leitchfield (o)

6. Bear Creek (g)

7. Diamond Springe (g)

8. Jewell (o)

9. Qaineville (o)

10. Butlereville (o)

11. Halfway (o)

12.

13. Adolphus (o)

14. Sootteville (o)

16. Steffy (o)

16. Oil aty (o)

18. Oekamp (o)

19. Wayne County (o)

County

System

Buck Creek (o)

Little Richland (Barbour-

vile) (o)

Bumins Springs (g)

Island Credc (o)

Frosen Creek (o)

Roae Creek (o)

Station Camp (p)

Irvine (o)

Big Sinking (o)

Ashley (fi)

Campton (o)

Stillwater (o)

Cannel City (o)

Menelee (g)

Olympia (o) Bagland (o) .

Fallsburg (o)

Buaeeyville (o) . . . GcOTges Creek (o). Laurel Creek (o) . .

40. Point Creek (o)

41. Ivyton (o)

42. Beaver Creek (o)

43. Beaver Creek (0>.

44. Ines (g)

46. Moulder (o)

46. Green Hill (o) . . .

47. Burksville (o) . . .

Breckinridge . Meade. Ohio. Grayson.

Do. Edmonson. Logan. AUen.

Do.

Do.

Do. Allen Allen. Alien. Barren. Barren. Barren. Barren. Wayne.

Lincoln.

Knox.

Clay

Owsley.

Breathitt.

Estill.

PoweU. Wolfe.

Do. Morgan. Menefee and

Powell. Bath. Bath and

others. Lawrence.

Do.

Do. tFohnson and

Lawrence. Johnson and

Morgan. Magoffin. Knott.

Knott.

Martin.

Warren.

Do. Cumberland.

M

D

Dt

M

M

D S. D

D S, D

S

s

Sd

D

M

S

S, D

O, S, M

P M D, M D D D

S. D D D D D

D D

D M M M

M

M

M

M, P

D, M, P

M D S, D O

Formation

Warsaw. Sand.

Do. Waverly.

Do.

Waverly, Cypress. Onondaga. Niagara, Onondaga . Onondaga. Niagara, Onocdaga. Niagaia.

Do. Niagara, Onondaga . Onondaga. Warsaw. Niagara.

Niagara, Onondaga . Many sands.

Onondaga.

Several. Big Injun.

(?)

Onondaga.

Onondaga.

Onondaga.

Niagara, Onondaga.

Niagara, Onondaga .

Onondaga.

Do.

Do.

Do.

Do. Do.

Do. Berea.

Do. Berea, Wier.

Do.

Wier.

Pottsville, Wier. Mauch Chunk,

Pottsville. Several.

Big lime. Big Injun. Onondaga. Niagara, Onondaga . Trenton?

.Structure

Dome.

(?) Anticline.

(?)

(?)

Dome.

Monocline.

Anticline.

Do.

Do.

Anticline.

(?) (?) Anticlines and

synclines. Anticline.

Anticline. Anticline. Anticline. Anticline. Anticline. Anticline. Anticline. Anticline.

Do.

Do.

Do.

Monocline. (?)

Monocline. Syncline. Monocline. Do.

Dome.

Dome. Dome. Syncline.

Anticline.

(?)

(?)

(?)

238 Geology Of Petroleum

vician, Silurian, Mississippian, and Pennsylvanian rocks. Any porous liinestone, where covered with shales, may serve as a reservoir. The reservoir limestones are not uniformly porous, and the production is therefore spotted.

Both east and west of the Cincinnati arch, at places not far from the coal measures, are areas of bituminous sandstones. These are shown on a map by Eldridge. They appear not to be closely connected with the oil pools.

General Sectign fob Kentucky Fields (Based on Sections by Hoeing, Matson and Jillson)

Pennsylvanian:

Pottsville conglomerate; alternating sands, shales, and coals, conglomerate at base; contains Beaver, Horton, and Pike sands in Floyd, Knott, and Pike Counties, and Wages, Jones, and Epperson sands in Knox County 60-1,000

Mississippian:

Chester and Mauch Chunk shales and sandstone, some limestone; contains Maxon sand. In eastern Kentucky 30 to 275 feet thick; in western Kentucky 300- 800

St. Genevieve; fine sands, oolitic white limestone (Big lime). Thickness in eastern Kentucky 20- 400

St. Louis; fine gray-white limestone. Thickness ii western

Kentucky 475-1,000

Waverly sandstones and shales. In eastern Kentucky 400 to 600 feet thick; contains Keener, Big Injun, Squaw, Wier, and Berea sands. In western Kentucky calcareous shales and limestone; contains amber oil of Barren, Warren and Simpson Coimties. Thickness in western Kentucky 400

Devonian system:'

Ohio shale; in shallow wells yields an abundance of highly mineralized water 150

"Corniferous limestone," usually a cherty magnesian limestone with some shale beds. Oil sand in Irving region 30

Silurian system:

Niagaran; blue shales and yellow limestones, in places containing chert; locally includes some sandstone. Oil in Allen County 60

Eldridge G. H. : Asphalt and Bituminous Hock Deposits of the United States. U S. Geo). Survey Twerdyiecond Ann. Repi, part 1, pi. 26, opp. p. 240, 1901.

'The section of the Devonian and older rocks represents the central Blue Grass region, after Matson, G. C, y. Sr Geol, Survey WaUr-Supply Paper 233, 1909.

Appalachian, Lima-Ind., And Mich. Fields 239

Ordoyician stem:

Richmond formation:

Upper division, heavy-bedded gray or blue arenaceous limestones, with about 10 feet of dense calcareous shale in

lower part; locally an impure sandstone 60

Middle division, blue shale, with some blue or dove-colored

limestone 125

Lower division, interbedded blue limestone and shale 80

Maysville formation; interbedded blue limestones and shales, the alternate layers usually thin and nodular; most of the

beds thin 230

Eden shale; mainly bluish shale, but upper part is commonly

sandy (Garrard sandstone) 200+

Winchester limestone; generally yields moderate amounts of

strong brines 60+

Lexington limestone: Upper division, gray, crystalline and cherty (Flanagan chert) ;

commonly yields much salt or saline-sulphur water 75

Middle division, light-drab argillaceous limestone, with shale beds; uppermost part, 20 to 60 feet thick, is commonly sandstone, with some phosphatic limestone; yields some

strongly mineralized water 194

Lower division, heavy bedded, coarse grained, crystalline,

and cherty 30

Highbridge limestone; mainly limestone, with shade lenses; little sandstone; yields moderate amounts of salt and salt-

sulphur water, especially from beds near the top 400

Unidentified limestone, similar to Highbridge limestone 100

St. Peter ''sandstone;'' a siliceous limestone, yielding large quantities of salt-sulphur water. Thickness unknown.

Most of the gas fields are in the northeastern part of the State, although there are a few along the Ohio River in northwestern Kentucky. The location of oil and gas pools is shown on Fig. 104 after Jillson.

The Campton oil pool is in Wolfe County, about 50 miles southeast of Lexington. The field as it was developed in 1909 is roughly crescent-shaped, with a length of about 3J miles and a maximum width oi miles. The rocks that crop out in the Campton field are of Pennsylvanian age, belonging to the lower part of the Pottsville group. The oil probably occurs in a sand layer of the

*Clapp, F. G. : Natural Gas in the United States. Econ. Geology, vol. 8, p. 522, 1913.

*MuNN, M. J.: The Campton Oil Pool, Kentucky. U, S, Qeoh Survey BuU. 471, p. 9, 1912.

240 Geology Of Petroleum

Devonian, which Mium considers as the Comiferous. The Campton sand has two pay streaks in which oil occurs in the northeastern part of the field. These are as a rule from 24 to 28 feet apart, and each probably ranges from 3 to 10 feet in thickness. In the central and southern parts of the field rarely more than one pay streak is found. This is from 1 foot to about 14 feet below the top of the sand. The field Ues on a monocline, on which is developed a plunging anticline. The south half of the field lies along the axis and sides of a broad, low secondary fold. Over part of the territory the contour on the oil sand 220 feet below sea level marks the dividing line below oil and salt water. As stated by Munn, salt wells form almost a semicircle around the south half of the district.

The Menifee gas field is in Menifee County, about 20 miles northeast of the Campton pool. The rocks are of Pennsylvanian, Mississippian, and Devonian age. The Devonian rocks, however, do not crop out. The gas is found in the Onondaga or Comiferous (Devonian) limestone just below the Ohio shale. On June 1, 1912, the production was reported to be approximately 25,000,000 cubic feet, and the gas had a closed pressure of about 60 pounds to the square inch. The Comiferous limestone is gas-bearing on a monocline between the 290-foot contour on the south side of the field and the 500-foot contour on the north side, the maximum difference in the height of the top of this bed in the field being more than 200 feet.

The Ragland oil field is about 15 miles northeast of the Menifee gas field. The surface rock is of Mississippian age, the beds being essentially the same as in the Menifee field. The Comiferous limestone carries the oil. This formation varies greatly in thickness. At some places it is absent; at Campton it is probably 200 feet thick; at Irvine, a pool some 20 miles southwest of Menifee, it is only 20 feet thick. The oil and gas bearing portion, or "pay streak," as it is called, varies greatly in position and thickness from well to well. Its porosity is due to numerous minute cavities, many of which are of microscopic size.

The Irvine oil field' is on the western edge of the Appalachian

MuNN, M. J.: The Menifee Gas Field and the Ragland Oil Field, Kentucky. IT. S. Geol. Survey BvU. 531, p. 9, 1913.

In this region the "Comiferous" is the Onondaga.

Shaw, E. W. : The Irvine Oil Field, Estill County, Kentucky. U. S. GeoL Survey BuU. 661, pp. 149-160, 1918,

Appalachian, Lima-Ind., And Mich. Fields 241

coal basin, a few miles east of the eastern border of the broad area of Ordovician limestones. A southeastward dip carries the Ordovician beneath successively younger rocks of Siliu'ian and Devonian age, which crop out inmiediately west of Irvine. To the east these rocks are overlain by rocks of Carboniferous age (Mississippian and Pennsylvanian).

lltVINB AMTICUNC

FiQ. 105. — Cross-section from Irving to Campton, Kentucky, showing the dip and thickening of formations to the east, the structural features on which oil and gas are found and the general attitude of the surface. (After Shaw.)

As a general rule the formations thicken toward the east. The top of the Mississippian series in the western part of the Irvine field averages about 640 feet above the oil sand or "Corniferous" limestone, whereas in the eastern part of the field it is about 700 feet above; in the Campton field, 20 miles to the east, it is about 850 feet; and in the east end of Wolfe County nearly 1,000 feet. This gradual eastward divergence of the Maxville (?) and Corniferous limestones is illustrated in Fig 105.

v!q

Fig. 106. — Profile of the oil sand across the Irvine field, Kentucky. (After

ShaWf U. S. Oed. Survey.)

A fault zone borders the crest of the Irvine anticUne on the northwest. The effect of the faulting is to drop a block of strata from half a mile to 2 miles wide and probably more than 20 miles long, 25 to 200 feet (Fig. 106).

The Irvine fault zone is nearly parallel to the axis of the Irvine anticline. It runs northeastward from Irvine, cares gradually to an east or slightly north of east course from Estill Furnace to High Rock, bends slightly south of east, and at Gln Cairn resume an eastward course.

Geology Of Petroleum

CoMBiMBD Section in Estill Coxtntt, Kentucky {After Shaw. The column showing depth has been recalculated to conform with

other sections)

Heavy sandstone

Shales and shaly sandstone

Black slate

Coal

Gray shales

Coal

Shales

Buff earthy limestones

Archimedes limestone

Gray limestone

Calcareous shales

Oolitic limestone

Buff limestone

SemiooUtic limestone

Gray limestones

Earthy buff limestone

Thin gray cherty limestones

Massive limestone

Blue limestone and shale

Earthy yellow limestone

Sandstones and shales

Black shale

Estill County oil sand

Blue and gray shales

Gray lime

Gray lime

Gray shale

Gray lime

Red lime

Gray lime

Brown lime

Gray lime

Greenish-white friable shaly sandstone

Hard fine-grained limestone, dark dove - color, with occasional bands of dark-blue hard limestone

Hard gray limestone

White fine-grained sand and lime.

Bottom of Whiteoak well.

Thiokneaa

Feet

Depth

Feet

1,069

1,094

1,239

1,244

1,269

1,279

1,287

1,297

1,314

1,354

2,193

2,203

2,628 2,773 2,788

Geologic Formation

Conglomerate measures.

Chester, 33 feet.

St. Louis, 150 feet.

Waverly, 490 feet- Devonian shales, 125 ft. Comiferous, 25 feet. 1 Niagara, 150 feet.

'Cilnton, 53 feet.

Lower Silurian (Qrdovician), Hudson and Trenton groups, 1,476 feet.

Calciferous( StPeter?).

Appalachian, Lima-Ind., And Mich. Fields 243

The "pay" or oil-bearing portion of the oil "sand," differs from the remainder of the limestone or dolomite in having larger pores and in being softer or less indm*ated. In places it is cavernous. As this character is due to recrystallization, it is extremely irregular in development. After penetrating the soft, more or less sticky clay shale that overlies the oil sand the drill commonly enters a rather hard limestone or cap rock, which here and there yields water and which ranges from a few inches to several feet in thickness. Below this rock is the soft brown sandy-textured magnesian limestone that constitutes the oil reservoir. In the eastern part of the field, where the whole "sand" is thicker, oil-bearing strata are found at more than one horizon.

Most of the wells in the Irvine field yield little gas. Salt water is probably present in the lower part of the oil sand throughout much of the field, particularly the southern half, and many wells bordering the field have yielded considerable quantities of water. Along the northern border, however, wells that fail to produce oil are commonly reported altogether dry.

Oil was first discovered in quantity in Knox County in 1840, when a well drilled for brine on Little Richland Creek, about 6 miles north-northeast of Barbourville, began flowing oil at a rate of probably 100 barrels a day from a shallow depth. All the outcropping rocks of Knox County belong to the Pottsville group. They consist chiefly of sandstone and shale but also include several beds of coal, clay, and probably limestone. The sands that have furnished oil and gas in paying quantities in Knox County, named in ascending order, are the Epperson sand, the Lower and Upper Jones sands, and the Lower and Upper Wages sands of Pottsville age. They are all white or gray sandstones, containing soft porous pay streaks in which oil and gas are found. The structure is said to be monoclinal, with small terraces locally developed. About 50 holes were drilled in Knox County in 1917, and some of them proved to be 50-barrel wells.'

In the Wayne County and McCreary County fields, in southern

Shaw, E. W. : Op. cU,y p. 176.

*MtTNN, M. J.: The Campion Oil Pool, Kentucky. U. S. Geol. Survey Biitt. 471, p. 19, 1912.

*Pbmberton, J. R. : a Rsum of the Past Year's Development in Kentucky from a Geological Standpoint. Am. Assoc. Pet. Geologists , 2, pp. 38-63, 1918.

244 Geology Of Petroleum

Kentucky, the oil is in Ordovician, Silurian, and lower Miasissippian rocks. At some places no salt water is present and the oil lies in synclines.

At Bussejrville, in Lawrence County, northeastern Kentucky, the oil is in a monocline and comes from Pottsville, Mississippian, and Devonian rocks at depths between 700 and 2,000 feet.

At Petroleum, in Allen County, oil is found in anticlines and synclines, in Silurian rocks, at depths of 80 to 300 feet.

In the Hartford field, Ohio Coimty, western Kentucky, the oil is found probably in the Devonian, in a broad anticline, at depths of 1,500 to 1,700 feet.

Tennessee. — Tennessee is divided into three geologic provinces (Fig. 107). In the eastern part of the State there is a broad belt of closely folded rocks ranging from Cambrian or older to Carboniferous. These rocks are extensively faulted and so far as known contain no oil or gas. The western part of the State is occupied by Cretaceous, Tertiary, and Quaternary rocks, which are apparently flat or dip at low angles. The central part of the State is lower in elevation than the eastern and western parts and is known as the central basin. The oldest rocks in this basin are of Ordovician age and consist of limestones and calcareous shales. Surrounding the Ordovician is a great belt of Devonian and Mississippian rocks. East of the Mississippian is a broad belt of Pennjsylvanian conglomerate, sandstones, shales, and beds of coal. The 'Pennsylvanian belt is only about 35 to 50 miles wide, and at some places the coal beds are eroded.

Although oil seeps of considerable size have been known in Tennessee for many years, the production is small. In the Spring Creek district, about 80 miles east of Nashville, oil in small quantities is produced from wells in the Fort Payne formation (Mississippian) at depths less than 30 feet. In the Superior and Riverton districts, northeast of the Spring Creek district, the lowest outcropping formation is the Fort Payne of Mississippian age, consisting of calcareous shale, a thin sandstone, some limestone, and bedded chert. Underlying the Fort Payne formation and entirely below drainage level is the Chattanooga shale (Devonian), ranging from 25 to 30 feet in thickness. The oil and gas are ir the Ordovician rocks below the Chattanooga shale, and are fourd

*MuNN, M. J. : Preliminary Report on the Oil and Gas Developments in Teonestee. Tennessee Geol. Survey BvU, 2-E, pp. 9-10, 1911.

Appalachian. Lima-Ind., And Mich. Fields 25

Co

g

o

o

o to

.a

o

M

Geology Of Petroleum

at numei'oiis horizons through more than 1,500 feet of strata, though most of the production comes from the upper 500 feet. Most of the oil is a heavy dark-green to black oil, but in a number of wells a light amber-colored oil of excellent quality has been found. A little salt water is present.

Record of Lacbt No. 1 Well, Spurrier, Tennessee

Shales, etc

Chattanooga shale

'Limestone and shale

Limestone, siliceous (brown) . . .

Shale, blue, soft

Limestone and shale alternating

Thiekn

Depth

Feet

Feet

1,000

In 1916 a well was drilled on the creek flats about three-quarters of a mile northwest of Glenmary, Scott County. Oil was encountered in a stratum in the St. Louis formation at a depth of 1,232 feet. The production was 10 to 20 barrels a day. The stratum is 8 feet thick and is reported by drillers to be a sand, but according to Glenn it is probably an oolitic limestone. The oil is dark green and of good grade. There was Uttle gas with the oil. The rocks at Glenmary are part of a long monocline that rises gently to the west or west-northwest. The rate of rise at Glenmary is between 30 and 40 feet to the mile. No evidence was found of any fold or flattening or other interruption of this general monocline.

There are numerous anticlines in western Tennessee in the Paleozoic rockSj but folds that inclose permeable rocks overlain by shales seem to be rare. Oil has also been reported to occur in the Eocene rocks at the west end of the State, but the report is unconfirmed. These rocks are similar in general character to some of the beds in the salt-dome region of the Gulf coast.

*Glenn, L. C: Recent Oil Development at Glenmary, Tennessee. Resources of Tennessee, vol. 7, p. 40, 1917.

APPALACHIAN, LlMA-lND., AND MICH. FIELDS 24? Recobd of Pbmbbbton No. 1, Glbnmaby, *

Feet

Sea 0-3

Hard white sand 35

Black slate 46-160

Hard white sand 160-305

Slate 306-436

Coarse loam sandstone; salt water at 606 feet 436-640 !

Black slate 640-647

Hard white sandstone, base of Lee 647-730

Slate and lime shells, top of Pennington 730-776

Red shale 776-796

Black slate 796-822

Dark lime ; . . . 822-896

Red shale 895-908

Dark lime 908-930

Black slate, base of Pennington. 930-60

Limestone, top of St. Louis; a little show of gas at 1046

feet 960-1048

White slate 1048-1061

Dark lime 1051-1144

Black slate 1144-1147

Gray sand 1147-1165

Hard white lime 1156-1232

Gray sand and small pebble, oil-bearing 1232-1240

Hard white lime 1240-1244

'GuBNN, L. C: Op. dt., p. 42.

Alabama. — The Fayette gas field is about 50 miles west of Birmingham, Alabama, in the western part of the Warrior coal field. Gas and some oil were found in 1909 in a drill hole put down for oil. Several wells dug later yielded large flows of gas with high pressure at about 1,400 feet. With the exception of a comparatively thick covering of sand, clay, and gravel, of Cretaceous and later age, the rocks penetrated by the drill in the Fayette district appear to belong entirely to the Pottsville formation, which consists of shales with included sandstone beds and coal.

The general structure of the Warrior coal basin, in which the Fayette gas field lies, is that of a broad, flat basin, gently tipped to the southwest. Several of the gas wells appear to tap the sands on the limbs of a gentle anticline. The data are not now sufficient to show the general relation of the gas sands to the structure.

'MuNN, M. J.: The Fayette Gas Field, Alabama. U. S. Geol. Survey Bull 471, pp. 30-65, 1912.

'248 Geology Of Petroleum

UMA'IflDLUIA OR TKENTON FIELD

The Trenton limestone oil and gas field of Ohio and Indiana

(Fig. 108) occupies alarge area that extends with interruptions

from Lake Erie to a point near Marion, Indiana-' The width of the field varies greatly; at some places it is sufficient for only a few BowNOCKER, J. A.; Petroleum in Ohio and Indiana. GeoL Soc. America Sua., vol. 28, p. 670, 1917.

APPALACHIAN, LIMA-IND., AND MICH. FIELDS 24d

rows of wells, but at others it is 20 miles or more. It is said that 30,000 wellff have been drilled in the Indiana portion of the Tren- ' ton field, and a larger number in Ohio. The output from the field in Ohio attained its maximum in 1896, exceeding 25,25000 barrels. The maximum production in Indiana was in 1904, when the yield was about 11,300,000 barrels. The pressure and production have greatly declined in recent years. The Trenton oil is sul- f phurous and has a paraflSn base. The gas is abotlt "92 |)er cent methane.

Surface indications of oil and gas are rare in this field. Neivertheless they led to its development. Prospecting was first cairied on in the vicinity of Findlay, Ohio, where gas seeps were common and where as early as 1838 gas was utilized in a small way for domestic heating. Gases, including sulphureted hydrogen, fif ling cisterns were so common as to be regarded as a nuisance, lliese seeps led to the development of the Findlay pool in 1865. {This pool was shown by driUing to be on a structural dome having a|)out 200 feet of closure. 1

The rock successions in Ohio and Indiana are shown by! the following well records.* i

Indiana I

Thickness (Feet)

Niagara limestone 153

Hudson River limestone ' 451

Utica shale

Trenton limestone at .

Ohio

Thickness (Feet)

Niagara limestone 167

Niagara shale and Clinton

limestone 108

Medina shale 47

Hudson River shale and hme-

stone 462

Utica shale 300

Trenton limestone at 1,092

So regular are the formations that approximately similar well records can be furnished by the thousands, though there is considerable variation in the depths of wells due to their position with reference to folding. In the Ohio fields the depth to the Trenton usually ranges from 1,000 to 1,500 feet, but in Indiana the depth is more uniform and, according to Blatchley, averages 1,000 feet.

*Orton, Edward: Ohio Geol. Survey, Vol 6, p. 112, 1888. Blatchlet, W. S.: Indiana Dept. Geology and Nat Res., Twenty-first Ann, Rept., p. 68, 1897. cU., p. 68.

Geology Of Petroleum

The principal ''pay rock" usually lies within 50 feet of the top of the Trenton, and in early days, in the Ohio part of the field, it was a general beUef among drillers that unless oil were found when the drill had penetrated 50 feet of the limestone it was useless to con-

FiQ. 109. — Map showing the structure of the Lima-Indiana, or Trenton limestone oil and gas field, Ohio and Indiana, by contours on tne top of the Trenton limestone. {After Orion,) Sections on fines AB, etc., are shown in Fig. 10.

tinue sinking. Later, however, a second and a third "pay;" were found, but these have proved of small value in comparison with the first. The structure of the Trenton limestone has a marked relation to

Appalachian, Lima-Ind., And Mich. Fields251

Fio. 110. — Sections through Lima-Indiana oil and gas field along tinea AB, CD, etc., Fig. 109. (Redrawn from sections by Edward Orton.}

252 Geology Of Petroleum

the production of oil. The region is a broad, flat-topped anticline tat has formed as a warping on the Cincinnati arch. The Cincikinati axis crosses the Ohio River a short distance east of Cincikinati. Northward from that place it bifiurcates, one arm extending Northwestward toward the south end of Lake Michigfin and tie other one east of north toward the west end of Lake Erie. In other words, the axis forms a Y, with the stem crossing the Ohio Biver near Cincinnati. In Ohio part of the richest territory has been found on this arch, but in Indiana it does not appear on the smnijiit of the arch, but on the north side, where the rock dips to the iiortbeast. The Trenton limestone nearly everywhere in these

r '

tTfo States contains brine below the oil.

jFig. 109 is contour map of the region redrawn from a map by Orton, issued in 1889. Sections are shown in figure 110. The extensions of the fields since 1889 are indicated by comparison with, Pig. 108, after a map by Bownocker, issued in 1917. As shown by these figures the oil and gas are at crests of the folds in tle region near Findlay and on the north slopes of the folds in western Ohio and eastern Indiana.

The fractured and dolomitized Trenton limestone, which con- t£|fins the oil and gas, underlies the Utica shale. Above the Utica ate Hudson River and Medina shales, then in ascending order the Canton limestone and the Niagara shale and Umestone. The siirface is practically flat, and on anticlines the Niagara crops out. In general the gas lies about 950 to 1,200 feet deep, and the oil a Uitle deeper, and both are near the top of the Trenton or generally not more than 100 or 200 feet down in it.

. The Trenton in the producing region has a high porosity, which, according to Orton, has been developed by dolomitization of limestone. He cites many analyses to show that the Trenton where oil-bearing is much richer in magnesium than where it is barren of oii. Orton's opinion of the origin of the fractures in the Trenton limestone was not shared by Phinney,' who maintained that the

iOiN, Edward: Ohio Geol. Survey, vol. 6, p. 46, 1888.

Orton, Edward: The Trenton Limestone as a Source of Petroleum and Inflanmiable Gas in Ohio and Indiana. U. S. Geol. Survey Eighth Ann. ,, part 2, pp. 475-662, 1889.

'Bownocker, J. A. : Op. cU., p. 672.

Phinnby, a. J. : The Natural-Gas Field of Indiana. U. S. Geol. Survey Eleventh Ann. RepL, part 1, p. 617, 1891.

Appalachian, Lima-Ind., And Mich. Fields25S

m

cavities in the Trenton limestone are due to "loss of substance and not to substitution" in the Indiana field. He says the roek is commonly hard, uniform in texture, and compact between the irregular ramifying cavities and pores interspersed through it.

Around the gas field salt water rises to nearly equal altitudes on all sides. Although the Trenton is porous on both sides of the arch over northern and central Indiana, in the southeastern part of the State it is more compact. The main body of the arch may be regarded, then, as a long inverted bifurcating trough having its

icaasbt.

A

t intuit f.

'S

inatUvoU'j

e.rioMts

Lake

Ij

I G Rao Win

Frdnuvrt . f 'i \rtNT i

?V I -

KdUniuoo] 'van BUIIH ;

Cunton

Orli

I

,BwU* I

Hibiaa

Tol.

Fig. 111. — Outline geolocal map of southern peninsula of Michigan. {After Smith). Section from Manistee through Petrolia, Ontario, is shown on Fig. 112. Roman numerals refer to formations listed on page 255.

south end closed and its north ends immersed in the salt water, which is forced up into and around it by the hydrostatic pressure of the water. Orton and also Phinney state that the pressure is due to the pressure of the water around the sides of the arch. The Cincinnati arch is a dome surrounded by a larger basin. The water descends down the slopes of the basin and rises in the arch.

264 Geology Of Petroleum

pushing oU and ga6 ahead of it, and equilibrium ia established by the back preasure of gas when it equals the water pressure.

Michigan Field

The southern peninsula of Michigan is Btructurally a great basin (Fig. Ill) whose long axis trends north.* The country is nearly everywhere deeply covered with glacial drift, and information pertaining to the underlying strata is obtained chiefly from well drillings. The area was a seat of depoeition through nearly al] of the Paleozoic era, and strata from the Ordovician to Pennsylvanian crop out or are discovered in drill holes. Shales are abundant in the section, limestones are numerous, and a few beds of sand are present. In the eastern part of the peninsula small

I f l! il il .! Ii !i ! !

folds are probably developed on the westward-dipping beds (Fig. 112). At Port Huron oil is obtained from the Dundee formation (Onondaga or "Comiferous"), which is chiefly limestone. This formation is also the source of oil ia Lambton County, Ontario, east of Port Huron. (Seep.476.) The Port Huron wells have produced oil since 1900, but the yield has never been lai and in 1919 was only a few barrels a day. The oil of Michigan is of good grade and rich in the lighter spirits. Gas and salt water are associated with it.

', R. a. :The Occurrence of Oil and Gas in Micb;aii. Michigan Ged. and Biol. Survey Pvh. 14, Gral. aer. 11, pp. 1-281, 1914.

Appalachian, Lima-Ind., And Mich. Fields255

Pennsylvanian:

I. Sacinaw formation (>er Pottsville) and Parma aandstone (lower Pottaville).

Missi88Ippian:

II. Grand Rapids group: Upper Grand Rapids. Basrport or MazviUe limestone (upper St. Louis), and lower Grand Rapids of Michigan series.

III. Marshall formation: (Kinderhook of Iowa, Black Hand and Logan of Ohio.) Upper Marshall or Napoleon and lower Marshall.

IV. Cdklwater shale and Berea sandstone.

Devonian:

V. Antrim shale.

VI. Traverse formation (Hamilton and Marcellus, Erian and Delaware of Ohio). VII. Dundee limestone (Corniferous and Ulsterian, and upper Heidelberg).

Silurian:

VIII. Monroe formation: Uppw Monroe or Detroit River series, middle Monroe or Sylvan* ian, and lower Monroe or Bass Island series.

IX. Niagara (Guelph and Lockport), Rochester shale, and Clinton.

Chapter Xvi

/ Illinois

Introduction. — The Illinois output of petroleum and gas comes mainly from the southeastern part of the State, nearly all of it from a district including parts of Clark, Cumberland, Lawrence, Jasper, Crawford, and Wabash Coimties (Figs. 113, 114, 115). 1 Although petroleinn was known in IlUnois at an earUer date, com- ' mercial quantities were not discovered until 1905. The maximum yield was reached three years later, when lUinois produced \33,686,238 barrels. Production has declined rapidly since then, and in 1917 the state yielded but 15,776,860 barrels. Illinois had in 1917, as estimated by Kay, 230 square miles of oil-producing territory. The oil is of high gravity and relatively free from sulphur.

Most of IlUnois is covered with glacial drift and surface indications of oil or gas are meager. Near Chicago bitumen is found in the Niagara limestone, and in Calhoun County there is an oil seep in that formation. Neither of these regions suppHes petroleum. In the first producing field the evidences were obtained by deep driUing for coal and by chance prospecting. In the Sandoval dome, in Marion County, oil seeps along a fault into a coal mine. Most of the recent discoveries have resulted from drilling areas mapped and recommended by the Illinois State Geological Survey.

/) The principal oil-bearing strata are in the Mississippian and (Pennsylvanian series. These series consist of sandstones, shales, and limestones, and there are six or more productive "sands" in the principal oil fields.

The sands are variable, some of them attaining a thickness of more than 100 feet in places, but the producing part is generally but a small percentage of the total thickness. The different lenses

*Kay, F. H. : Oil Fields of Illinois. Geol. Society America Bull., vol. 28, pp. 655-666, 1917.

Blatchley, R. S. : Oil Resources of Illinois, with Special Reference to the Area Outside the Southeastern Fields. Illinois State Geol. Survey Bull. 16, 1910; Oil in Crawford and Lawrence Counties. Illinois Geol. Survey BvU, 22, 1913.

Illinois

of the Robinson sand in Crawford County average about 25 feet in thickness, whereas the ''pay" sand averages only about 7 feet. In two of the pools the sand ranges from 25 to 40 feet and is saturated with oil throughout, but this condition is exceptional.

Total Production of Illinois Sands for Typical Areas to Jan. 1, 1917

(After Kay) .

Sand

Depth (Feet)

Period (Years)

Barrels

Casey

800-1,150 1,150-1,350, 1,350-1,650 1,750-2,000

f5,309.93

\2,919.37

"Robimsnn . ,

8,390.49

Pnchanan

36,233.98

Kirkwood

2,546.22

15,672.80

Structure sections of Illinois are shown in Figs. 114 and 115.

/

Section for the Area Lying South of a Line Drawn Eastward from

THE MoXTTH of the MISSOURI RiVER TO MARSHALL, ILLINOIS, AND THE

State Line (After Bain, with Some Additions and Changes after Kay. Made by W. H. E.)

Quaternary:

Glacial till, sand, and gravel; loess and alluvium. Present as surfacerocks everywhere except in northwest and extreme south. Thickness, 30 to 225+ feet.

Tertiary:

Lafayette, LaGrange and Porters Creek. Clays, sands, gravel, and ferruginous conglomerate. Occurs only in extreme south. Thickneite 250 feet.

Cretaceous:

Ripley. Clay and sand. Occurs only in extreme south Thickness 20 to 40 feet.

Pennsylvanian:

McLeansboro formation. Shales, sandstones, thin limestones and coals.

Rocks above top of Herrin (No. 6) coal. Thickness 500 to 1,000 feet. Carbondali formation. Coals, shales and sandstones. Rocks between

the base of Murphysboro (No. 2) coal and the top of the Herrin coal.

Thickness about 300 to 350 feet. Pottsville formation. Sandstone, some thin shales, and coals* Thick"

p?S9 $00 to 00 feet, i

Geology Of Petroleum

Fio. 113. — Map showing oil and gas fields of Illinois. Sections along lines A A and BE are shown on Fig. 114. Districts are numbered as follows: 1. Colmar; 2, Pike County; 3, Carlinville; 4, Staunton; 5. Greenville; 6, Main Illinois field; 7, Carlyle; 8, Sandoval; 9, Sparta; 10, litcnfield.

260 Geology Of Petroleum

Mississippian:

Chester. Sandstones, shale, and limestones in series, with unconformities at bases of sandstones. At many places six such series are shown. Thickness varies; at several places about 300 feet*"

Cypress. Sandstone, very irregular and usually thin in southeastern Illinois. The Cypress sandstone is absent in the oil fields of Lawrence County.

Unconformity.

Ste. Genevieve. Limestone, mostly ooolitic and very cross-bedded. Thickness, 80 to 100 feet.

St. Louis and Salem (Spergen). Limestone, dense becoming ooUtic in lower division. Thickness 300 feet.

Osage (Burlington, Keokuk and Warsaw). Shale above and coarsegrained limestone with chert below. Thickness 440 feet.

Kinderhook. Shale and shaly limestone, red. Thickness 60 feet.

Devonian:

Upper Devonian (Sweetland Creek). Shale. Thickness 50 to 60 feet. Hamilton. Limestone. Thickness about 100 feet. Onondaga (Grand Tower). Limestone. Thickness 155 feet.

Upper Oriskany (Clear Creek). Chert and hmestone. Thickness 200

to 240 feet. Helderberg (New Scotland). Limestone. Thickness 165 feet.

Silurian:

Alexandrian (Sexton Creek, Edgewood, Girardeau and Orchard Creek). Limestone and shale. Thickness 116 feet.

Ordovician:

Richmond (Cincinnatian). Thebes sandstone, Femvale limestone.

Thickness about 100 feet. Kimmswick-Plattin (Trenton). Nondolomitic limestone. Thickness

610 feet recorded. St. Peter. Sandstone. 120 feet recorded. Prairie du Chien group. Mostly dolomitic limestone with occasional

thin layers of sand and shale. 545 feet recorded.

aWelleb. 8.: The Chester Series in Illinois, Jour. Geol. Vol. 28, p. 408, 1920.

The producing sands of Illinois, as stated by Kay,* range in age from the top of the Carbondale formation of the Pennsylvanian series down to the upper part of the Trenton limestone. The output is derived principally from the sandstones of the Carbondale and Pottsville formations of the Pennsylvanian and the Chester group and Ste. Genevieve formation of the Mississippian. A sandstone at the base of the Niagaran produces some oil at Colmar, McDonough County, in western Illinois.

iKat, F. H. : Oil Fields of Illinois. Geol Soc. America BuU., vol. 28, pp. 655-666, 1917,

Illinois 261

The producing beds are sands with the exception of the so-called McClosky sand, which is in reality the oolitic Ste. Genevieve limestone, lying immediately beneath the Chester group. Of all the producing beds in the State, those of the Chester are the most regular. The sands of the Pennsylvanian are extremely irregular in thickness and character, and it is often impossible to correlate them from one well to another with certainty. The Hoing sand, at the base of the Niagaran in the Colmar field, is found in smaller areas than any other producing sand. It was deposited in depressions on the Maquoketa surface during the encroachment of the Niagaran sea. Outside of the small area at Colmar numerous drill holes in the western part of lUinois have discovered it, but it is productive only in the Colmar field.

Structurally Illinois is a spoon-shaped basin, the tip lying in the northwest corner and the deepest part of the bowl in Wajnie, Edwards, Hamilton, and White Counties, in the southeast comer. (Fig. 113.) The long axis of the spoon extends northwestward, parallel to the main oil fields. In the western and central parts of Illinois the dip toward the axis of the basin is commonly as low as 10 feet to the mile. From the main fields to the basin the dip is more pronoimced. On the sides of the basin there are longitudinal folds. The most prominent is the La Salle anticline, which runs from Freeport to a point just east of La Salle, and thence through the main oil field and into Indiana. From western Illinois the rocks dip gently eastward to the Duquoin anticlme. At the southern part of the basin the dips of the rocks into the basin are locally 100 feet or more to the mile. East of the main oil fields in Crawford and Lawrence Counties the strata rise gently in Indiana. In southern Illinois strong folds, faults, and igneous intrusions are present.

Crawford, Lawrencei and Adjoining Counties. — The principal oil fields in Illinois are in Crawford, Lawrence, Clark, Cumberland, and Wabash Counties, in the southeastern part of the State. This field, which was discovered in 1905, yielded oil very near the surface and was developed rapidly, reaching its maximum production three years after discovery. In the northern part of the field wells reached producing sands at depths of about 300 feet. The

Blatchlet, R. S. : Oil in Crawford and Lawrence Counties. Illinois State Geol. Survey BvU, 22. 1913.

262 Geology Of Petroleum

rocks that crop out in this field are of the Pennsylvanian series, and the oil is derived from the Pennsylvanian and Mississippian rocks.

Broadly considered, accumulation has taken place at the southeast end of the plunging La Salle anticline. The dip of the beds to the southeast along the axis of the anticHne is comparatively high. The lowest producing stratum, the McCIosky "sand" of the Ste. Genevieve limestone, lies within 350 feet of the surface at the northwest end of the Clark Coimty field, whereas in the Lawrence County district it ranges in depth from 1,700 to about 1,860 feet. Minor warpings extend from the La Salle anticline both east and west. As shown by contour maps drawn by Blatchley, the structure is very irregular. There are seven productive sands, and the contour maps for each sand present noteworthy differences. The rocks as a general rule are saturated with salt water, and the oil and gas accumulate on anticlines and terraces. The gas is rich in gasoline, which is recovered, but the gas production is comparatively small.

The crest of the La Salle anticHne in Crawford, Lawrence, and adjoining counties is very irregular. The part of the arch containing oil is 2 to 8 miles wide, and nearly 50 miles long. On the flanks of the fold the field is marked oflf by lines of salt water.* Some of the wells, particularly those in the McCIosky "sand,** were gushers.

The Robinson pool in Crawford County is about 7 miles wide, but narrows southwest of Robinson. The Crawford Coimty pools possess one general oil-producing zone, the Robinson sand, which is of Pennsylvanian age, lying at the top of the Pottsville. This sand is very irregular in distribution and ranges in thickness between 2 and 50 feet, the average being 25 feet. At some places the Robinson sand is a series of lenses with many streaks, tongues, and detached portions. The arch on which the oil is found is very irregular, with an undulating top and a mapped closure of about 100 feet. Although the sands are irregular in distribution and at places impervious, the yield has been large. According to Blatchley, of 2,370 wells mapped in this area all but 206 yielded oil or gas. Th initial daily production was between 1 and 1,600 barrels.

The field extends southward into Lawrence County, which contains its most productive portion. Oil or gas occurs in the Bridge-

Blatchlet, R S.: Op, cit., p. 143. Idcm, p. 100.

Illinois

port and Buchanan sands of the Pennsylvanian and in the Gas, Kirkwood, Tracey, and McClosky sands of the Mississippian. Blatchley has contoured each of these sands over the most productive portion of the Lawrence field. The McClosky sand does not produce oil throughout the length of the field, because of local irregularities in structure and the variable nature of the producing stratum. It is variable in thickness and averages not more than 10 feet over the entire field. Instead of being a single bed, it is probably a zone in the upper part of the Ste. Genevieve formation, the position of the oil being controlled by the porosity of the rocks. - Within the zone, which has a mftvinmm thickness of 80 feet, one

I —

Fio. 116. — Section across dome in oil field in Petty township, Lawrence County, Illinois. The surface of the ground is about 1,000 feet above the top of the section. {After BlatchUy.)

to three oil horizons are reported. Toward the north the sands play out or become thin and unproductive. At the south end of the oil field the structure of the McClosky, Tracey, and Kirkwood sands is different from that of the Buchanan and Bridgeport. (See Fig. 116.) The thickness of the beds between the sands varies , from place to place, and there is probably an unconformity near the base of the Buchanan.

In the northern part of Clark County the Trenton has yielded oil at a depth of 2,200 feet.

264 Geology Of Petroleum

The Allendale field is in Wabash County, 8 miles southwest of the Lawrence County field. Oil was discovered here in 1912. The first solid rocks penetrated are the Pennsylvanian, which consist of a series of shales alternating with sandstones and thin lenses of limestone. The sandstones and shales occur in beds of varying thickness, ranging from only a few feet to 200 feet or more. At the base of the Pennsylvanian is the Pottsville sandstone. The Chester group, of Mississippian age, consists of a series of thin limestones and shales with a few thin beds of sandstone, which increase in thickness toward the base of the section penetrated by the wells. The producing sand in the Allendale field, commonly known as the Biehl sand, has been correlated with the Buchanan sand of the Pottsville. The oil is found in a low dome at about 1,500 feet below the surface.

Central and Western Illmois. — In the Illinois Basin, well up on its sides, the Pottsville rocks are saturated with salt water. In the west-central part of the State, however, a few small domes produce conmiercial quantities of gas and a Uttle oil. Of these, the Staimton gas field, the Carlinville oil and gas field, and the Litchfield oil and gas field are the most important. In these fields oil and gas are found in lenses. Four productive horizons have been recognized, separated by small vertical intervals. Theoretically, a tilted porous sandstone lens should provide conditions for accumulation of oil and gas at its upper end; but in Illinois, as stated by Kay, the bedding planes of the Pottsville seem generally not impervious enough to prevent the lateral movement of oil and gas unless doming of the strata has capped the edge of the porous bed and prevented escape of the oil.

The oil and gas field near Carlinville, Macoupin Coimty, is one of small production. All the rocks belong to the coal measures, which consist of shales, sandstones, a minor amount of limestone, and several beds of coal. Three persistent beds are recognized— the Carlinville limestone, coal No. 6, and the oil and gas zone at the base of the Pennsylvanian. The intervening shales, although fairly constant in thickness, are changeable in character. Underneath the sands the drill usually strikes limestone, which is sup-

iRiCH, J. L. : The Allendale OU Field. Illinois Geol. Survey BtiU. 31, pp. 69-68, 1915.

Kat, F. H. : The Carlinville Oil and Gas Field. Illinois Geol. Survey BvU. 20, pp. 83-95, 1915.

Illinois 265

posed to be either the Ste. Genevieve or the St. Louis limestone, of Mississippian age. Tlie Chester shales, sandstones, and limestones, which underlie the area south of Carlinville and which include most of the producing sands of the main oil fields, are absent in this field. Although the productive sands are not invariably foimd at the same stratigraphic position, they lie near the base of the coal measures and are beUeved to constitute the Pottsville formation.

Gas has accimiulated at the top of the dome, oil occurs below the gas, and salt water lies below the oil.

The first valuable deposit of oil found in Illinois was discovered near Litchfield by the Litchfield Coal Co. in November, 1879. In an effort to find a lower coal seam sufficiently thick to be profitably mined, a hole was drilled in the bottom of the shaft which passed into oil-bearing sand at a depth of 225 feet below the coal and 682 feet below the surface. Salt water at first threatened to floQ the mine, but the hole was plugged, though oil leaked into the mine and was skimmed from the mine water for several years. The oil was a heavy lubricating oil and was associated with gas. The structure of the rocks of the area near Litchfield as indicated by that of the Herrin (No. 6) coal shows a distinct dome. The production of oil has not been large.

The oil pool at Carlyle, in Clinton County, southwestern Illinois, about 45 miles east of St. Louis, was discovered early in April, 1911. . The oil is found in the Carlyle sand, which belongs to the Chester group (Mississippian). The Carlyle sand on the whole a soft, porous sandstone of irregular thickness. Around the edges of the pool it is harder than in the center, and in one or two places it pinches out. Above the sand is about 30 feet of bluish shale containing locally red shale. Above the Chester is the Pottsville, which carries salt water and locally gas; this is overlain by Pennsylvanian sandstone, shale, limestone, and coal. The oil sand is practically horizontal. Outside the field the sand dips in all directions except north, and apparently it also pinches out in all directions except to the north.

Leb, Wallace: Oil and Gas in the Gillespie and Mount Olive Quadrangles, Illinois. Illinois GeoL Survev BvU, 31, pp. 71-107, 1915.

*Shaw, E. W. : Carlyle Oil Field and Surrounding Territory. Illinois Geol. Survey BvU. 20, pp. 43-80, 1915.

266 Geology Of Petroleum

The Greenville gas field ' is in Bond County, about 2 miles south of Greenville. The gas has accumulated in the crest of an anticline that is elongated in an east-west direction. It is found in two sands belonging to the Chester group — the Lindley No. 1 and Lindley No. 2. These sands are separated by a few feet of sbaly strata, and Chester shes he above the Lindley No. 1. The top of the dome is about 50 feet high, which ia somewhat above the elevation shown in the Henin (No. 6) coal. The fold has increased with depth.

Fio. 117. — Diagram eboWine UDConEoimities and spotted character of ana in Colmai field, Illinois. (After Morse and Kay.)

The Colmar oil field, in western Illinois, was discovered in 1914. The existence of a dome was first pointed out by Hinds from levels run on coal No. 2, which crops out. Oil was found in a sandstone at the base of the Niagaran, which was probably deposited in depressions on the Maquoketa surface during the encroachment of the Niagaran sea. The sand occurs as lenses separated by areas in which the limestone fies directly on the shale with no interven*

iBl&, R. 8. : Oil and Gas m Bond, Macoupin, and Montgomery Counties, Illinois. Illinoia Geol. Survey BvU. 28, p. 45, 1914.

Illinois

Gbnbralizbd Section of Rocks in Colbiab Oil Fibld and Subroundino

Territory (After Morse and Kay)

System

b

a S

%

Series

s

a

'S

o

O

Drillers' Interpretation

Oq

a

e

a

Hoing oil sand.

Formation

Carbondale.

Pottsville.

Unconformity. St. Louis. Unconformity .

Salem.

Unconformity . Warsaw.

Keokuk.

Burlington.

Kinderhook. Unconformity.

Unconformity

Hamilton.

Unconformity

Unconformity. Richmond. (Maquoketa) Unconformity

Kimmswiok- Plattin. (Trenton)

Character

Alluvium; confined to valley. Loess: most conspiououa along

bluffs of Illinois Kiver. Drift: mixed clay, audit sravel,

and boulders.

Principal coal-bearing formation of IlUnois. Shales, sandstones, thin beds of limestone, day and coal.

Includes beds from base of coal No. 2 to Misnissippian. Sandstone and shale, and some limestone, clay, and thin coal.

Limestone, breceiated, blue, weathers yellow in contains scattered corals.

Impure limestones of yellow tint, (ufficult to distinguish from limy sandstone; at places shale increases and the formation consists of limy shales, limy sand stone, and impure limestone.

Thin-bedded impure limestone and shales, fossililerous. Considerable blue clay shale is locally present.

Gray crystalline limestone, fossilif- a-ous. shaly toward top.

Limestone, generally cherty; not exposed.

Shale, bluish gray, limy.

Shale, light to dark; many spores of SpOTangitee, a minute reddish

Limestone, gray, small amount <rf sand, and some pyrite. Usually not magnesian.

Limestone, wxtVt crystalline, magnesian. Exists in separate lenticular masses; where it is not present. Hamilton rests on Maquoketa shale. Show of in places near base.

Sandstone, grains well rounded. In lenses with no connection. Probably accumulated in depressions on Maquoketa surface. Produdng bed of Colmar field.

Shales, bluish

St. Peter.

Limestone, gray, white, or brown. Crystalline in faces. Odor of oil not unusual. Not in Colmar field.

Sandstone; generally saturated with mineral water.

Thiokness

Feet Variable.

Average, 25.

In fiUed valleys, 100 -H.

0-140+

0-30 +

30 +

100 -h

(Average in C o Im a r field 14).

300-iOO

recorded.

268 Geology Of Petroleum

ing sand. As stated by Kay, no direct connection is apparent between the Hoingpool, where the sand lies 90 feet above sea level on a terrace at the northeast side of the dome, and the Hamm pool, on top of the dome, where the sand is 70 feet higher. The pool at the town of Colmar lies on the north side of the dome and probably has no direct connection in the sand with either of the other pools.

The Hoing sand, which carries the oil, is as much as 14 feet thick where present but is very erratic in occurrence. The lenses are surrounded by impervious beds. The oil pool lies on the flat part of the oil sand on the side of a low dome and is associated with salt water. Several domes have been discovered by contouring the base of coal No. 2, but the production is small. The anticline in the Canton-Avon region has been described by Savage.* (See Pig. 117).

At Sandoval, Marion County, a few miles north of Centralia, a dome has been contoured mainly by using data obtained in coal mining. This dome and an associated terrace yielded oil and gas in two sands below the coal. The area is faulted, and the oil was first noted at a seep into a mine through a fault.

Near Sparta, in Randolph County, western Illinois, gas and a little oil are found in the Chester (Mississippian). The gas occurs along a small synclinal fold, but the relations are uncertain. The field has produced little oil and is not now important.

In Pike County, western Illinois,* gas was discovered by drilling wells for water. The gas occurs along an anticline, the eastern limb of which is determined by the line separating the productive from the dry wells. The porous stratum forming the reservoir is a bed of yellowish-brown magnesian limestone which probably belongs to the Niagara. The thick bed of Kinderhook shales that overlies the Niagara limestone in this region 'provides the imper-

HiNDS, Henrt: Oil and Gas in the Colchester and Macomb Quadrangles. Illinois Geol. Survey BvU. 23 (extract), pp. 11-13, 1914.

'Savage,. T. E.: Geologic Structure of Canton and Avon Quadrangles. Illinois Geol. Survey BvU. 33, pp. 91-99, 1916.

Blatchlbt, R. S. : Illinois Geol. Survey Bull. 16, p. 146, 1910.

Lavage, T. E. : The Pike County Gas Field. Illinois Geol. Survey BulL 2, pp. 787, 1906.

WoRTHEN, A. H. : Illinois Geol. Survey, vol. 4, pp. 24-42, 1870.

Illinois 269

vious cover of the reservoir. The wells are all shallow, the gas being reached at depths of 75 to 350 feet, depending largely upon the inequalities of the surface. The production is small.

Geologic Formations of Pike County Gas Field

(After Worthen)

Pleistocene: Loess and drift 0-100

Pennsylvanian 20

Keokuk group (limestone and shale) 100-125

Burlington limestone 150-200

Kinderhook group (mainly shale) 100-120

Niagara limestone , 0-50

References to niinois Fields

Barrett, N. O.: Petroleum in Illinois in 1917 and 1918. Illinois Gcol. Survey Bull. 40, pp. 1-144, 1919.

Blatchlet, R. S.: Oil Resources of Illinois. Illinois Geol. Survey BvU, 16, pp. 42-176, 1910.

Oil and Gas in Crawford and Lawrence Coimties. Illinois Geol.

Survey Evil. 22, 1913.

Oil and Gas in Bond, Macoupin, and Montgomery Counties.

Illinois Geol. Survey BvU, 28, 1914.

Kay, F. H. : Carlinville Oil and Gas Field. Illinois Geol. Survey BvU. 20, pp. 81-95, 1915.

Petroleum in Illinois in 1914 and 1915. Illinois Geol. Survey

BvU. 33, pp. 71-90, 1915.

Petroleum in Illinois in 1914 and 1915. Illinois Geol. Survey

BvU. 33, pp. 71-90, 1916.

Notes on the Bremen Anticline. Illinois Geol. Survey BvU.

33, pp. 101-103, 1916.

Oil Fields of Illinois. Geol. Soc. America BvU., vol. 28, pp.

656-666, 1917.

Kirk, C. F.: Natural Gas in the Glacial of Champaign County. IlUnois Geol. Survey BvU. 14, pp. 272-275, 1909.

Lee, Wallace: Oil and Gas in Gillespie and Mount Olive Quadrangles. lUinois Geol. Survey BvU. 31, pp. 71-107, 1915.

Morse, W. C, and Kay, F. H. : Area South of the Colmar Oil Field. Illinois Geol. Survey Bull. 31, pp. 7-35, 1915:

The Colmar Oil Field — a Restudy. Illinois Geol. Survey BvU.

31, pp. 37-55, 1915.

Rich, J. L. : The Allendale Oil Field, Illinois Geol. Survey BvU. 31, pp. 57-68, 1915,

270 Geology Of Petroleum

Rich, J. L.: Ofl and Gas in tbe Birds'Quadrang Illmois GeoL Survey Buff. 33, pp. 105-145, 1916.

Oil and Gas in the Yinoennes Quadrangle. Illinois Gecd. Sur-

vey . 33, pp. 147-175, 1916. . Sbaw, E. W. : The Carlyle Qfl Field and Surrounding Territory. Illinois GeoL Survey BvU. 20, pp. 43-80, 1915.

Udden, J. A., and Sbaw, E. W. : U. S. GeoL Survey Geol, AUas, BeQeviUe- Bieese foUo (No. 195), p. 14, 1915.

Udden, Jon: Coal Deposits and Possible Oil Fields Near Duquoin. Illinois GeoL Survey BuU, 14, pp. 254-262, 1909.

Weller, Stuabt: Anticlinal Structure in Randolph County. Illinois CieoL Survey BuU. 31, pp. 69-70, 1915.

Chapter Xvii Mid-Continent Fields

General Features.The Mid-Continent oil fields include the oil-producing areas qf Oklahoma, Kansas, and Missouri,, the gasproducing region of Arkansas, and the fields of northern and central Texas and nhera Louisiana. The principal producing areas are in Kansas, Oklahoma, and northern Texas and Louisiana. In these fields oil is found mainly in Carboniferous and Cretaceous strata. In the principal fields of Kansas and northern Oklahoma the sand members associated with Cherokee shales produce nearly all the oil. In southern Oklahoma and northern Texas near Red River oil is obtained from sandstones of the Pennsylvanian and from sandstones that are correlated with the Permian (Red Beds) by some investigators and with the upper Pennsylvanian by others. These beds produce gas and oil in the Healdton and neighboring districts. In the Ranger region, northern Texas, oil is found in the Bend series (Mississippian). In east, central Texas and northern Louisiana ofl is found in Cret&ceous sandstones and chalks.

In the Mid-Continent fields oil and gas occur on domes, anticlines, structural noses, structural terraces, and fluted monoclines. On the whole the structural features are somewhat less accentuated than those in the Appalachian oil fields, and the porous rocks are more generally filled with salt water. The oil saturation is greater than in most other fields, and structural elevations with less than twenty feet of closure are searched for diligently and explored.

The major uplifts in this region (Fig. 118) are the Ozark dome, the Ouachita orographic element, including the Ouachita, Arbuckle, and Wichita mountains, the Llano-Burnet uplift of Texas, and the Sabine uplift. Although the Ouachita element is more highly deformed than the Ozark dome, the structure of the Ozark is more far-reaching, for the beds dip westward far away from the Ozark center, and southwestward within a comparatively short distance of the Ouachita element.

The OzarupUft is a low dome with rudely elUptical outline, lying in southern Missouri, northern Arkansas, southeastern

Geology Of Petroleum

Kansas, and northeastern Oklahoma. As stated by SiebenthaP it is roughly bounded on the north and northeast by Missouri and

H E B Ra S Ka

Fig. 118. — Sketch map showing geology of region containing Mid-continent oil field. The Pennsylvanian outcrops in the areas shown by dots, widely spaced. There are small outcrops of Silurian and Devonian rocks in the Ozark region. These are not shown in the sketch. The igneous rocks which are in the areas represented by small crosses, are older than the sedimentary rocks.

SiEBENTHAL, C. E.*. Origin of the Zinc and Lead Deposits of the Joplin Region, Missouri, Kansas, and Oklahoma, Ut St Geol, Survey BuU, W, p. 23, 1915,

Mid-Continent Fields 273

Mississippi Rivers, on the west by Spring and Neosho (Grand) Rivers, on the west and south by Arkansas River, and on the southeast by Black River and some of its tributaries. The uplift as a whole is a table-land bounded by long, low northern and western slopes whose inclination is generally imperceptible to the eye, and for much of its extent by an abrupt southern slope facing the open valley of Arkansas River. Near and parallel to its southern margin the uplift culminates topographically in the Boston Mountains, a long, narrow plateau rising to an elevation of 2,000 feet. The plains that surround the uplift have a general altitude of 500 to 750 feet. The central portion of the Ozarks is an upland lying somewhat below the crest of the Boston Mountains.

The Ozark uplift is a broad anticline in which the strata have no perceptible inclination except at the southern margin, where the Boston Mountains break off into a southward-dipping monocline. Superimposed upon the uplift are quaquaversal domes, of which the principal one is in the region of the St. Francis Mountains.

In the early history of the Ozark region parts of the crystalline rocks of the St. Francis Mountains were islands in an archipelago, and their erosion furnished the material that formed the Cambrian and Ordovician sandstones, and which, with that which formed the associated dolomitic limestones, was spread out over Missouri and the adjacent States. Silurian limestones and shales were deposited on the southern and northeastern margins of the Ozark region, but in the western part of the region there was no Silurian sedimentation. During Devonian time limestone was deposited on the northern and eastern borders of the region and sandstone on the southern border. The Chattanooga shale of the Devonian series underlies a triangular area in northwestern Arkansas, southwestern Missouri, and northeastern Oklahoma. After the Devonian period the Ozark region was submerged and the Mississippian limestones were laid down probably over the whole area. Elevation and erosion followed, during which the limestone land surface developed a sinkhole topography. This land was in tiun submerged and upon its irregular, bouldery, cherty surface was laid down a series of shales and sandstones of Pennsylvanian age, the lowest series being the Cherokee shale, which contains the principal oil sands of Kansas and Oklahoma. Until the end of Pennsylvanian time the crystalline area of the St. Francis Mountains was the stratigraphic nucleus of the Ozark region. At the end of the

Geology Of Petroleum

Fig. 119. — Index map of Oklahoma, showing mountain areas and certain oil

fields.

Mid-Continent Fields 275

Carboniferous period the Ozark region was raised almost to its present position, the highest place coinciding closely with the geographic center. The uplifted area has since been subjected to minor warping.

The Ouachita orographic element (Fig. 119) extends from east to west through western Arkansas and southern Oklahoma for a distance of 350 miles. This element may be subdivided into the Ouachita Mountains, the Arbuckle Mountains, and Wichita Mountains. None of these mountains are very high — indeed, the Boston Mountains, which lie north of and parallel to the Ouachita Mountains on the Ozark-monocline are higher than any part of the Ouachita element or the Missouri Ozarks. The Ouachita element is, however, a center of close foltling and is topographically for the most part a plateau rather than a mountain range. It represents the eroded remnant or roots of what was once probably a continuous lofty range.

The Ouachita Mountains of Arkansas and eastern Oklahoma are joined to the Arbuckle Mountains of Oklahoma by a broad area of folded rocks, and the two mountainous regions form structurally a single feature. In the Ouachita Mountains Paleozoic sediments, including those as late as Mississippian, are highly deformed. In Arkansas they are closely folded and in places overturned. In eastern Oklahoma' they are folded and also profoundly faulted. The Arbuckle Mountains, in their eastern part, where they coalesce with the plain, are only about 750 feet above the sea, but their elevation increases westward to 1,300 feet. The structural trend is about N. 70° W.

The Arbuckle Mountain region contains a thick series of rocks, chiefly limestones, which range from Middle Cambrian to Devonian. These are succeeded on the borders by an almost equal thickness of Carboniferous conglomerates, shales, and sandstones. In the central part of the district, unconformably beneath the Cambrian strata, there is a mass of granite, granite porphjrry, diabase, and associated crystalline rocks. Most of uplifting and folding of the region occurred before the deposition of the Permian

*SlEBENTHAL, C. E.I Op. cU.y pp. 11-12.

iMONDB, F. W., and Branner, J. C. : Arkansas Geol. Survey Rept. for 1888, vol. 4, p. u, 1891.

Tafp, J. A. : U. S. Geol. Survey Geol, Atlas, Coalgate folio (No, 74), 1901.

/

276 Geology Of Petroleum

Red Beds, which were laid down across its western part, but in places the Red Beds themselves are distinctly folded.

About 60 miles to the northwest are the Wichita Mountains, which are physiographically in marked contrast to the Arbuckle plateau, being composed of a range of rugged mountains and straggling peaks and hills, standing in a level plain. The Wichita uplift trends N. W. approximately in the same direction as the Arbuckle uplift. It consists of a central mass of igneous rocks, which is partly surrounded, unconformably, by a thick section of Cambrian and Ordovician sandstone and limestone. The stratigraphy is essentially similar to that of the Arbuckle uplift. The Cambrian and Ordovician strata, approximately 6,000 feet thick, bear no evidence that they were either folded or uplifted into land at any time during their deposition. The main Arbuckle uplift began near the middle and culminated near the end of Pennsyl> vanian time, prior to the deposition of the Red Beds. The Red Beds are only gently folded between the Arbuckle and Wichita Mountains.

The Criner Hills, which lie 15 miles south of the Arbuckle Mountains, consist of a faulted block of Paleozoic strata about 7 miles long, which trends northwefet. Structurally they are similar to the Arbuckle Mountains and they include the same Paleozoic strata. As stated by Taff , they are the Arbuckle Mountains in miniature.

/ Briefly stated the deformation of the Ouachita- Arbuckle-Wichita region has taken place during three periods. These are (1) Pre Pennsyl vanian, (2) Post Pennsyl vanian, and (3) Post_Pmian* In the Arbuckle region the major folding was Pre Pennsylvanian,' although in the Ardmore district south of the Arbuckles, the Pennsylvanian rocks are highly tilted. North of the Arbuckles also they are rather closely folded. There are also considerable deformation of the Ouachita Mountains in Post Pennsylvanian time.

Since Permian and also since Cretaceous time, minor warpings have taken place in the Mid-Continent fields, for strata of both Pennsylvanian and Cretaceous age are folded. Dips as great as

Tapp, J. A.: Preliminary Report on the Geology of the Arbuckle and Wichita Mountains. U. S. Geol. Survey Prof. Paper 31, p. 11, 1904.

Tafp, J. A.: Op. cit.y pp. 47-50.

Fuller, M. L.: Carbon Ratios in Carboniferous Coals of Oklahoma and Their Relations to Petroleum. Econ. Geology, vol. 15, pp. 187-224, 1920.

Mid-Continent Fields 277

5° have been noted on the limestones. In Cotton County, southeast of Healdton, Oklahoma, according to Wegemann, the adjustment of ndinor streams to folds is very exact, and it is possible that movements have continued till comparatively recent times.

The Llano-Burnet region of central Texas lies on the broad coastal slope that extends from the Cordillera to the Gulf of Mexico. 2 In this region erosion has exposed rocks of pre-Cambrian and Paleozoic age within and about the rim of an oval topographic basin which is nearly surrounded by Cretaceous rocks. The Llano-Burnet region is a structural uplift. It exhibits the remnants of an ancient mountain range that has been eroded. The influence of this uplift is reflected by the rock structure far to the north of the Llano-Burnet region.

The rocks of the Llano-Burnet region fall into three subdivisions — (1) pre-Cambrian schists, gneisses, and granites; (2) Paleozoic sandstones, limestones, and shales; and (3) Cretaceous sandstones, clays, and limestones. The Paleozoic strata, which completely surround the pre-Cambrian area, are folded and faulted and are separated from the pre-Cambrian by an unconformity representing a great time interval. The Cretaceous formations are nearly flat. They are separated from the Paleozoic rocks by a great erosional unconformity.

The Llano-Burnet region has been one of elevation and erosion through long geologic periods. The pre-Cambrian rocks were eroded almost to base-level, and on them were deposited Cambrian and Ordovician rocks. The Silurian, Devonian, Jurassic, and Triassic are lacking, showing probably that during much of Paleozoic time the region was above the sea. Near the end of the Paleozoic era and before the Mesozoic rocks were deposited, folding and faulting took place on a considerable scale. The Mesozoic rocks, which lie on the Paleozoic strata, are generally nearly horizontal in the Llano-Burnet region.

The Mid-Continent fields produce oil of high gravity as is shown by the following analyses:

Wegemann, C. H. : Anticlinal Structure in Parts of Cotton and Jefferson Counties, Oklahoma. U. S. Geol. Survey 602, p. 34, 1915.

*Paige, Sidney: Mineral Resources of the Llano-Burnet Region, Texas. U. S. Geol. Survey BuLL 450, 1911. See also U. S. Geol. Survey Geol. Atlas, folio (No. 183), 1912.

Hill, R. T.: Physical Geography of the Texas Region. U. S. Geol. Survey Topographic folio (No. 3), 1900.

Geology Of Petroleum

Analtsbs of Oils of Mid-Continent Fields'*

Field

Kansas

Chanute

Paola

Augusta

Oklahoma

Muskogee

Gushing

Bird Creek

Glenn Pool

Healdton

Texas

Petrolia (deep) Petrolia (shallow). .

Electra (deep)

Eleetra (shallow). . . Corsicana (light). . . Corsicana (heavy) . .

Louisiana

Caddo

Crichton

Baum£ Gravity

a4.5

Gasotine. Benzine,

Naphtha, Kerosene,

(Per Cent)

55 (kerosene)

Lubricating

Oil and Residuum (Percent

''Gabdnbr, J. H. : The Mid-Continent Oil Fields. Geol. Soc. America BuU., vol. 28, p. 719.

In general the crude petroleum of Kansas and Oklahoma is dark green by reflected light, brownish by transmitted light, and has a Baume gravity of about 34°. Muskogee furnishes oils that are yellowish green in reflected light or bright wine-colored in transmitted light and run as high, as 38° Baume. The Madill yields an

MID-CONTINENT FIELDS 27d

oil that has a dark olive color in reflected light or dark wine color in transmitted light and runs as high as 47.5° Baume. From Garber and Ingalls are obtained green oils of 43° Baume. Petroleum of slightly inferior grade comes from the Healdton field. It is a very dark oil, with an average Baume gravity of about 30°, and runs somewhat low in its content of light distillates. Petroleums from the deeper sands, as at Gushing and Blackwell, Oklahoma, or at Augusta, Kansas, average between 35° and 40° Baume and run relatively high in gasoline and other Ught products. Petroleums from the Petrolia and Electra fields, Texas, have a dark-brown color in reflected light, and range from 39° to 45° Baume but are not so high in many of the light distillates as petroleums from Kansas and Oklahoma. Petroleum from the Thrall field of Texas is rather light in gravity and has a brownish color somewhat similar to that of the better grades at Gorsicana and Moran, Texas, or at Caddo, Louisiana. Local areas in Texas, as, for instance, the Brownwood district, furnish petroleum running low in gravity and high in lubricating constituents, resembling in this respect oil from the Healdton field, although of lower gravity.

Although the Mid-Gontinent petroleums are rarely free from asphalt, this constituent is present in very small quantity, ranging / from practically nothing to 5 per cent.

Northeastern Oklahoma, Southeastern Kansas,

ARKANSAS, Ain> MISSOURI

General Statement. — The northeastern Oklahoma and southeastern Kansas fields are treated as a structural and stratigraphic unit. East of the area which includes them, extending from northem Missouri almost to Muskogee, Oklahoma, are found Mississippian and older rocks. From Muskogee Gounty, east and southwest to the Arbuckle Mountains is an area containing many gas fields, of which it is said that any oil present may have been vaporized or scattered by metamorphism attending the faulting of the Ouachita element (Fig. 76, p. 176). West of this area in Oklahoma f and Kansas the petroliferous rocks are covered by Permian beds, / and in that direction limits to the oil fields can not be set. On' account of the great depth of the oil sands, the character of the Permian beds, and the smaller amount of folding of the Permian, the structure is difiicult to interpret, and development is not rapid.

Gardner, J. H.: Op. dt, p. 718.

280 Geology Of Petroleum

Nevertheless the field is being slowly and laboriously extended westward. In northeastern Kansas Pennsylvanian rocks are found, but the territory is not known to be petroliferous.

The rocks that crop out in the area are Pennsylvanian and lower Permian. The beds strike about N10°-20° E. and dip west about 30 feet to the mile. Locally the dip increases, and on folds it becomes 100 feet to the mile or more. Reverse dips are rarely more than 1°. Faulting is common east, southeast, and south of the district. Faults are not rare in the Oklahoma portion of the oil-bearing area also, but as a rule the displacement of the faults is very small. On the whole deformation in the region is not intense.

The oil and gas are found in sands and very subordinately in thin-bedded porous limestones. Most of the productive sands are in the Cherokee shale series, above the Mississippian. Recently some oil has been foimd in the Mississippian limestone and in sands below it. The shales of the Cherokee are generally dark colored or black and carry bands of highly bituminous material.

/ The Bartlesville sand is by far the most productive, having ) supplied 90 per cent or more of the oil produced in Oklahoma and (Kansas up to 1919. It is a gray to brown sandstone, containing

usually a small amount of lime carbonate, enough to effervesce in 1 acid. In the Bartlesville region it is from 30 to 60 feet thick. It ' has an average porosity of 20 per cent. The thickest sands do

not contain oil in large quantities. McCoy states that the pay

sands where thickest show many partings of black shale. ; Oil and gas seeps are very rare in this area, and at most pools 1 they are lacking. East of the oil-bearing region, however, in

southeastern Kansas, southwestern Missouri, and northeastern ' Oklahoma, the Cherokee is marked at many places by asphalt bodies or oil seeps. Salt water is generally associated with the oil.

The Permian beds contain gas on the Blackwell anticline,' on the Garber dome, and on the Billings anticline. In the area where the Permian crops out the Pennsylvanian carries oil near the top.

K][ardner, J. H.: Mid-Continent Geology. OH and Gas Journal Suppl., May 30, 1919.

*McCoY, A. W. : Notes on Principles of Oil Accumulation. Jour. Geology, vol. 27, p. 252, 1919.

KjARDNer, J. H.: Mid-Continent Oil Fields. Geol. Soc. America BuU, vol. 28, p. 699, 1917.

Mid-Continent Fields 281

Oil residues are found in Oklahoma in Ordovician, Carboniferous and Cretaceous rocks.

The location of the fields in Oklahoma is shown by Fig. 120.

In the northeastern Oklahoma and southeastern Kansas field 1 the larger number of oil and gas bearing districts are on low domes or low anticlines, although a considerable number are on terraces. At least four are developed in lenses. Some of the productive folds are isolated structural features with clearly defined boundaries, like the domes of the Cushing field, Garber, and many others. Other fields are located on zones of gentle crumpling, like the Bartlesville area in Osage County and the areas in Washington County, to the east of it. Although these folds are gentle, many of them are easily recognized on account of numerous exposures. In many of the districts there is an abundance of salt water under strong pressure. In such districts the oil and gas lie above the water. Where the sands lie deep, segregation is more pronounced.

Oklahoma

Salient Features. — Oklahoma has produced a much greater proportion of the oil recovered from the Oklahoma-Kansas field than Kansas. The production in Oklahoma has come mainly from Nowata, Washington, Osage, Kay, Rogers, Tulsa, Pawnee, Garfield, Wagoner, Creek, Muskogee, and Okmulgee Counties. In the eastern part of the field the oil is obtained from shallower wells than in the western part, where the Cherokee series lies below great thicknesses of Pennsylvanian or of Pennsylvanian and Permian strata. In the eastern part of the field the pools are not all related to clearly defined folds, although production is generally controlled by slight cnmiples of the strata, by terraces, and by warpings. In this part of the field the regional dip of the Cherokee is considerably lower than it is in the western part. In Osage, Washington, and Nowata Counties, which lie along the northern boundary of Oklahoma, the dip is much less than it is in counties to the south and west. Apparently the oil traveled up the gradually flattening dip of the beds, and much of it lodged near tops of very gentle folds and local terraces, where the flattening beds checked migration. In the steeper part of the monocline, in Kay, Garfield, Noble, Creek, and Pawnee Counties, the greater concentrations are in clean-cut anticlines or on definitely closed folds that are

Geology Of Petroleum

a

w d a M

3Ss

00 Sq

w

p ja

5

p

5 k o

0 B fl fa's S"'H

FiQ. 120. — Index map showing principal oil and gas fields in Oklahoma.

(Data from Shanncm, and others.)

Mid-Continent Fields 283

superimposed upon the great monocline. Noteworthy among these features are thejCushingj Garber, and Ponca City folds.

McCoy states that pools which are not on anticlines or domes show a close relation to faults. Many of these faults do not crop out but are revealed by comparison of drill records. Some of the accumulations of oil appear to occur where sands are sealed by being faulted against shales.

The Cherokee formation, the principal oil and gas producing member of the Pennsylvanian series in Kansas and northeastern Oklahoma, contains the Squirrel, Skinner, Red Fork, Nemire, Bartlesville, Tucker, Dutcher, and other sands. In some districts five or six sands are productive.

The Cherokee formation in the Belton district, south of Kansas City, Missouri,* is about 430 feet thick. In southeastern Kansas' it is 450 feet thick. From the Kansas line southward the Cherokee formation gradually increases in thickness, so that it is 1,000 feet thick at Pryor Creek. In Kansas the Cherokee is above the Mississippian limestone and below the Fort Scott limestone, two easily recognized formations. Toward the south these limestones disappear, and correlations are less certain. In the Muskogee quadrangle the Winslow and Boggy formations, 1,500 feet thick, are correlated by Taff with the Cherokee, and in his report on the Coalgate quadrangle he correlated the Atoka, Hartshorn, McAlester, Savanna, and Boggy, which have a thickness of 9,000 feet, with the Cherokee. The formations toward the south are overlapped. The greater thickness of the Cherokee toward the south is due in part to the overlap, some of the beds being older than the Cherokee in Kansas.

The sea in which the Cherokee was deposited was probably supplied by sediments mainly from the Ouachita region, the sediments becoming thicker to the south. That the land mass existed toward the south in Pennsylvanian time is obvious also from the character of the sediments. The great shale and sandstone formations of Oklahoma thin out or decrease in thickness toward the north,

McCoT, A. W. : Notes on Principles of Oil Accumulation. Jour, Gedogyf 27, p. 262, 1919.

'Wilson, M. E. : Oil and Gas Possibilities in the Belton Area. Missouri Bur. Geology and Mines, 1918.

*Adams, G. I., GiRTY, G. H., and WnrrE, David: Stratigraphy and Paleontology of the Upper Carboniferous Rocks of the Kansas Section. U. S. Geol. Survey . 211, p. 65, 1903

284 Geology Of Petroleum

where the section contains thicker and more numerous limestone members and less sand and shale.

The Permian beds, which cover large portions of both Kansas and Oklahoma, thicken rapidly toward the west; in Roger Mills Coimty , on the western border of Oklahoma, they are 3,000 feet thick. Between the Arbuckle and Wichita moimtains several fields derive oil and gas from beds which some class with the Permian but which others have classified as Pennsylvanian. (See p. 320.)

There are no oil pools in the area of outcropping Mississippian and lower rocks in northeastern Oklahoma, nor in the region of older rocks south of the Choctaw fault. In the area between Fort Smith and Coalgate there is a belt of folded Pennsylvanian strata in which several gas fields are developed but which yield no oil. This condition is due to metamorphism, according to Gardner, who cites as evidence the coals of this belt, which run as high as 70 per cent carbon figured on an ash and moisture free basis.

General Stratigraphic Section in Main Oil and Gas District on

Northern Oklahoma

(Compiled from Sections by Taff, Aurin ard Gardner, with Economic Notes

Mainly from Gardner)

Permian series:

1. Unclassified shales, with thin limestone and sandstone mem- Feet

hers

2. Herington lifEiestone 18-20

3. Uncas shale 50

4. Winfield limestone 10-15

5. Doyle shale 22-35

6. Fort Riley limestone and other beds of thin limestone, sand-

stone, and shale down to the Neva limestone, inclusive.* Contains near base the shallow gas sands at Blackwell, Billings, and Garber , 500-600

7. Elmdale formation; included in Permian of Kansas by Beede

*AuRiN, Fritz: Geology of the Red Beds of Oklahoma. Oklahoma Geol. Survey Bull. 30, 1917.

Gardner, J. H. : The Mid-Continent Oil Fields, Geol, Soc. America

Bull, vol. 28, p. 699, 1916.

'Beal places the base of the Permian in the Gushing field 50 feet above the top of the Neva limestone.

Mid-Continent Fields

Pennsylvanian series:

Ralston group: Limestones and shale beds of Kansas section from Americus limestone to Lecompton limestone, inclusive. In Oklahoma consists of red and gray sandstone, red shale, and thin limestones. Contains the Garber oil sand.

1. Upper division down to Pawhuska limestone, inclusive. . . 650

2. Lower division down to top of Elgin sandstone 140

Sapulpa group:

1. Elgin sandstone. Probable horizon of shallow oil sand in

the Newkirk field and at Ponca City 20-150

2. Oread limestone 0-20

3. Buxton sandstone and shale. Horizon of main oil sand at

Ponca City and gas sand at Myers 700-1,000

4. Avant limestone 0-10

5. Ramona formation. Sandstone, shale, and thin limestone

beds. Includes Lost City limestone and Musselman oil

sands of the Cushing and Cleveland areas 300-400

6. Dewey limestone 15-25

7 Skiatook formation; sandstone, shale, and thin limestone beds. Includes Hogshooter limestone and Layton oil sand 350-400

8. Lenapah limestone. ,,,..,, 10-20

Tuba group:

1. Nowata shale; includes Wayside oil sand 75-150

2. Oolagah limestone or Big lime of the drillers 20-50

3. Labette shale (local coal bed, Dawson coal) 75-100

4. Claremore formation. Sandstone, shale, and beds of thin limestone. Contains at the base the Fort Scott or Oswego

limestone. Includes Cleveland and Peru oil sands 275-350

Muskogee group: Beds of shale, sandstone, and thin limestone correlated with the Cherokee shale (Boggy and Winslow formations at Muskogee). Includes the main oil sands of Oklahoma; the Red Fork, Bartlesville (Glenn), Tucker, Taneha, Booch, Morris, and Muskogee sands, the Muskogee lying at the unconformable base of the Pennsylvanian series. 450-1,500

Unconformity

Mississippian series:

1. Morrow limestone* 100-200

Unconformity.

2. Pitkin limestone 40-60

'BuiTH places the Morrow in the Glenn pool above the Mississippian. (See p. 293)

286 Geology Of Petroleum

3. Fayetteville formation; sandstone, shale, and limestone.

Contains the Mounds oU sand and a deep sand near

Sapulpa 20-200

Unconformity.

4. Boone formation; massive white limestone and massive beds

of chert 200-400

Devonian system:

1. Chattanooga formation; black fissile shale 30-50

2. Sylamore sandstone; clear quartz sandstone 0-25

Unconformity.

Ordovician system:

1. Tsrner formation; thin sandstone and limestone in shale. . . . 60-100

2. Burgen (St. Peter) sandstone; massive quartz sandstone. . . . 5-100

Cambrian system:

Massive limestone beds shown in Harrington well at Joplin,

Missouri 1,165

From Muskogee southward the lower portion of the Pennsylvanian series and the older rocks thicken at the rate of about 100 feet to the mile. The following is the general section for the McAlester-Coalgate-Atoka region:

General Stratigraphic Section in Eastern Oklahoma, North of

Arbuckle Mountains

(After Sections by Taff" and Gardner*)

Lower portion of Pennsylvanian: Feet

1. Seminole conglomerate 1-50+

2. Holdenville shale 260

3. Wewoka formation. Sandstone and shale with beds of

thin limestone 5OQ-8O0

4. Wetumka shale 120

5. Calvin sandstone. Approximate horizon of Oswego

limestone in northern area 140-240

6. Senora sandstone 140-485

7. Stuart shale 90-280

8. Thurman sandstone 90-280

9. Boggy shale, with beds of thin sandstone; limestone and

thin irregular coal at base 2,000-2,600

°Tafp, J. H.: U. S. Geol. Survey Geol. Atlas, Coalgate folio (No. 74), 1901.

Gardneb, J. H.: Mid-Continent Oil Fields. Geol. Soc. America BuU., vol. 28, p. 696, 1917

Mid-Continent, Fields 287

10. Savanna sandstone; massive sandstone strata with beds

of shale (horizon of Bar ties ville sand) 1,000

11. McAlester shale. Includes strata of sandstone. Coal ' beds of the McAlester-Coalgate region (Oklahoma coal

field) 1,800-2,000

12. Hartshorn sandstone 150

13. Atoka formation. Massive beds of sandstone with alter-

nating beds of shale 3,100

14. Wapanucka limestone. 100

Mississippian series: Caney shale 1,500

Devonian system: Woodford chert. 600

Ordovician and Silurian systems: Sandstone, shale, and limestone 5,000-7,000

Cambrian system: Reagan sandstone 100

Unconformity.

Pre-Cambrian granites.

Cushing Pooh — The Gushing oil pool is mainly in western Creek County but extends westward into Payne County. The field includes a number of subdivisions, among them Shamrock, Drumright, Dropright, and Mount Pleasant. The first well in this field was drilled in 1912 by C. B. Shaffer on the Jones farm, about 1 mile north of Drumright. The development was rapid, especially after the discovery of oil and gas in the Bartlesville sand. The production of the field reached about 300,000 barrels of oil a day, and at one time about 160,000 barrels of oil was produced daily by 160 wells from the Bartlesville sand alone.

The following table gives the geologic formations of the Pennsylvanian series as reported by Buttram in the vicinity of the Cushing field — the youngest at the top:

Neva limestone.

Sandstones and shales and thin limestones (556.5 feet).

Pawhuska limestone (provisional correlation). Is 2,340 feet above

Fort Scott limestone and 1,243 to 1,262 feet above Lost City

limestone. Shales and sandstones (134 feet). Elgin sandstone.

Buttram, Frank: The Cushing Oil and Gas Field, Oklahoma. Oklahoma Geol. Survey Bull 18, pp. 1-60, 1914.

Beal, C. H.: Geologic Structure in the Cushing Oil and Gas Field, Oklahoma, and Its Relation to the Oil, Gas, and Water. U. S. Geol. Survey BvlL 658, 1917,

Geology Of Petroleum

Interval.

Lost Cily limestone.

Interval (1,078 to 1,097 feet). Includes Layton sand at 700 to 810

feet above Wheeler sand. Fort Scott or Oswego limestones (75 feet) ( Wheeler sand). Interval. Bartlesville sand (in Cherokee shale.)

The most prominent outcropping stratum is a bed of limestone that is probably in part at least equivalent to the Pawhuska limestone of northern Oklahoma.

Oil is produced from six sands, the Layton, Jones, Wheeler, Skinner, Bartlesville, and Tucker. A sketch of the field is shown in Fig. 121 and a section in Fig. 122.

The dominant structural feature in the Gushing field, as stated by Beal, is a broad north-south anticlinal fold (Fig. 123) with

Sapulp

A8.

Cush/n po

0 f e 3 M/

1 I I I I

Glenn

Fig. 121. — Sketch showing structure in Gushing Pool, Oklahoma {ojitr Beal) and in Glenn Pool, Oklahoma (after Smith.) Gon tours show elevation of Pawhuska limestone above sea in Gushing Pool and of Fort Scott or Oswego limestone below sea in western part of the Glenn pool. Dots represent oil wells. Some scattered wells are not shown.

domes along its axis and many subsidiary folds and irregularities along its sides. This great fold is one of the largest structural features in northern Oklahoma. The contours of the three oil sands dififer locally from the contours of the surface rocks, although the general structural axes are practically identical. Each sand in the field exhibits small irregularities that apparently bear no definite vertical relations to one another — for example, the Bartles-

Mid-Continent Fields

Elevation in Feet op Highest Contoub on Crests of Four Folds in the Surface Bed, the Layton Sand, the Wheeler Sand, and the Bartlesville Sand, and the Dip in Different Directions From the Crests

(After Beal; +, Above Sea Level; -, Below Sea Level)

Dropright Dome

Shamrock Dome

Eleva-

Amount of Dip

Eleva-

Amount of Dip

tion

2H Miles

tion

of Crest

Northeast

IH Miles

H Mile

of Crest

Miles

of Crest

West of

East of

West of

East of

Along

Crest

Crest

Crest

Crest

Anticline

Surface beds. . . .

+ 1 .050

+1 .125

Layton sand. . . .

- 400

- 325

Wheeler sand. . . .

Bartlesvillesand.

Anticline

in North-

Mount Pleasant Dome

em Part of T. 16

N.. R

. 7E.

Amoimt of Dip

Eleva-

Eleva-

Amount

of Dip

tion of Crest

Miles West of

4 Miles West of

% Mile

South-

North-

tion of Crest

MMUe

East of

Crest

Crest

Crest

west of Crest

east of Crest

Surface beds

-f 1.100

+1.050

Layton sand. . . .

- 275

- 400

Wheeler sand. . . .

Bartlesville sand .

- 1 ,450

H75

-1,700

Part of vertical distance estimated.

Part of horizontal and vertical distances estimated.

Geology Of Petroleum

I 'I ' I ' I

Coo-

1,200

3=aE

eoo-ff=i£=j=

Fresh Water Freshwater

Fresh

SaH: Saltwater

Saltwater

layton lime"(somt ts) Break Layton sand (o* I)

i.eoo-|

t,200-

oaa

Jones sand

Cleveland sandCsomc 4"

Vhecler lime" Break Sandy member

ind

Skinner sand

Bart lew Smna

villain

cond My t water.

TticUr sand (oiQt watar in

Fig. 122. — Generalized geologic section showing the positions of oil and gas sands in Gushing field, Oklahoma. (After Beod.)

ville sand may show a small dome that has no counterpart in the Layton and Wheeler sands.

The distribution of oil and gas in the sands indicates that the source or gathering ground of the oil and gas was west or northwest of the field. The direction they took may be due in part to the fact that the dominant structural feature is an anticUne on a great monocline, the fold having a short east Umb and a long west limb. The gathering area is therefore practically all on the west limb. Gas first fills up the crest of the fold and acts as a barrier between the water on the east side and the oil migrating up the west limb. The oil, on account of its slower rate of movement through porous rocks, collects after the gas and forms a pool against the gas on the west or long limb. (See Fig. 123.) Below the oil is salt water. The plane between the two is not level, however, but in some sands the water surfaces on which the oil and gas rest are inclined and dip away from centers of anticlinal folds.

In the Gushing field proper there is very little

Mid-Continent Fields

J J J J Is§§

.kU.'JJJ

1 1 Ii 111

Geology Of Petroleum

Keet

S

1,000-

faulting. In the Bristow

"Lost City limestone." (Approximately 850 feet

below Tiger Creek quadrangle, however, which

sandstone.) ' '

bes to the southeast, there are many northwest faults.

Oheckerlioard lime

Dawaon ooal

aa

§

1,200.

l.twO-

o

s

;a:v:i-;i

.iii.ii.i'

f . I

1,800-

'I 1 1*' 1 1 I'M'

Big lime

Fori Scott llmeatone Sand

Sand Llanectontt

Bed Tork sand

Sand Glonn aand

2,000-

2,200-

o o

.4

2,400-

2,600

Squaw sand

Bhodos or Dutchcr sand

Morrow formation and V?

Pitkin limestone '

Mounds sand

Sand

Boone limestone ?

Fig. 124. — Composite skeleton section of the Glenn pool region, Oklahoma. (After Smith.)

Glenn Pool. — The Glenn pooP, which is southwest of Tulsa and about 30 miles east of the Gushing pool, is one of the most productive of the Mid-Continent field. It includes several minor pools known as the Taneha, Red Fork, and Ferryman. The pool was discovered in 1906.

The westward dip of the strata, which is about 50 feet to the mile, is interrupted by areas in which the formations lie flat or nearly so, whereas in other areas the dip is greater than normal. The structure is compUcated also by a system of folds whose axes roughly parallel the direction of general dip — sUghtly north of west. These folds are not well defined but are westwardplunging flutmgs. which merge

*Fath, a. E.: Structure of the Northern Part of the Bristow Quadrangle, Creek County, Oklahoma, with Reference to Petroleum and Natural Gas. U. S. Geol. Survey BuU. 661, pp. 69-99,

Smith, C. D.: The Glenn Oil and Gas Pool and Vicinity, Oklahoma. U. S. Geol. Survey BuU. 541, pp. 34-48, 1912.

Mid-Continent Fields 293

both to the east and west with the prevailing westward-dipping monocline.

The oil and gas occiu* in the several sands mentioned below, the field extending westward down the monocUnal dip. Where the strata are fluted on the monocline the wells are closely spaced on the minor warpings of the strata. Both upward and downward flutings carry oil. The monocline is believed to be sealed possibly by tighter sands above the productive portion of the field, or by shales coming together where sands play out.

Section Showing Formations Exposed in and to the East op the Glenn

Pool Area, Oklahoma

(After Smith) Carboniferous system:

Peimsylvanian series: Feet

Limestone, bluish gray; locally known as the Lost City limestone 1-40

Shale and sandstone 350

Limestone, bluish, hard; Checkerboard lime of the drillers

Shale, with variable beds of sandstone 215

Coal, Dawson l?i-2J

Shale, with irregular beds of sandstone 210-350

Limestone, massive, gray; Big lime of drillers 0-40

Shale, with irregular beds of sandstone 200

Limestone, Fort Scott; Oswego lime of drillers; bluish-gray

limestone with 3 to 5 feet of shale near middle 10-30

Shale, sandstone, limestone, and coal; Cherokee formation.. . . 1,000

Unconformity.

Blue to white limestone, with some shale and thin sandstone;

Morrow formation 100-120

Unconformity.

Mississippian series:

Limestone, blue and brown, locally sandy and shaly ; Pitkin 60

Black shale with thin beds of limestone and sandstone; Fayette-

ville formation 20-60

Unconformity.

Limestone, Boone; flinty Umestone and flint

The strata between the top of the Morrow and the top of the Boone merge into one formation in the southeast corner of Kansas, thus eliminating the Fayetteville, the Pitkin, and possibly the Morrow from the section, so that the Cherokee rests on the eroded

294 Geology Of Petroleum

surface of the Boone. The same conditions exist along the ninetysixth meridian, where well logs do not show these three formations more than a few miles north of the latitude of Tulsa, Southward from Tulsa the limestone beds in the Morrow and Pitkin probably become thicker and are likely to be mistaken for the Boone limestone. Sandstone beds occur at the top of the Morrow and the

Fig. 125. — Structural map of Glenn oil and gaa pool near Tulsa, Oklahoma. [After Smith.) The beds dip west. The structural contours show pceition of the surface of the Fort Scott or Oawego hmeatone, with reference to sea level For section along AB see Pig. 126.

top of the Boone. The geologic section is shown as Fig. 124, and a structural map as Fig. 125. A section across the field is shown as Fig. 126.

Mid-Continent Fields

Brisloiv Quadrangle. — The Bristow' quadrangle, in Creek County, is bordered by Bome of the most prolific oil fields of Oklahoma. The nearest wells of the east Gushing fiekl are only about IJ miles west of the Bristow quadrangle. About 9 miles east of the quadrangle is the Glenn pool, and in the area that lies between the Bristow quadrangle and the Glenn pool there are several minor fieWs. Several anticlines occur in this quadrangle. The strata exposed in the northern part of the quadrangle have an aggregate thickness of about 950 feet. They consist almost entirely of alternating sandstone and shale, the only exceptions being a few fimeatone beds in the eastern part of the area.

Nowata County Pods. — Nowata County is in the northeastern part of Oklahoma, bordering on Kansas. It contains all or parts of the following pools, many of which have been heavily productive: Adair, California Creek, Goody's Bluff- All uwe-Chelsea, Nowata (Glaett), Delaware-Childers, and South Goffeeville.

The surface of the county is in general a plain in which the streams have eroded wide valleys. It ranges in elevation from 600 to 926 feet. The surface rocks are Pennsylvanian shales, sandstones, and limestones.*

'Path, A. E.: Structure of the Northern Part of the Bristow Quadrangle, Creek County, Oklahoma, with Reference to Petroleum aod Natural Gaa. U. S. Geol. Survey BuU. 661, pp. 69-99, 1918.

Klklahoma Geol. Survey BuU. 19, part 2, p. 345, 1917.

Ij,i

i? , s

S'!

11

is

la

ii|

S

1 s

'.i 111

, "-la-j

(i

£

"1

nil

s Ss ;

5 la i

1 ,m

Geology Of Petroleum

The structure of Nowata County is in general that of a westward-dipping monocline upon which gentle crumpling is superimposed. In some places the normal dip is interrupted by a flattening or reverse dip to the east. An example of anticlinal folding is the Goody's Blufl-AIluwe-Chelsea field. Some other fields are not clearly related to well-defined structural elevations.

Washington County Pools. — Washington County is west of Nowata County, in northern Oklahoma. It lies entirely in the region of Pennsylvanian rocks and contains the Dewey-Bartlesville, Canary, Copan, Wann, Hogshooter, and Vera pools.

1903 1904 1905 1906 1907 1900 1909 19

Year

1915 1916

Fig. 127. — Curves showing yearly decrease in the first year's daily production (in barrels) of wells on several properties in the Glenn pool, Oklahoma, and (below) in the Bartlesville field, Oklahoma. The numbers show the number of wells in each group used to supply the data. (After Beat.)

Some of the wells drilled during its early period of development (1904-1906) had an initial production of 1,000 barrels a day. In 1906 the average initial production per well was about 73.2 barrels. The average gradually decreased from that time, and in 1914 it was only 10.4 barrels. At the end of 1914 there were 4,816 producing oil wells in this county.

The Dewey-Bartlesville field extends westward for several miles

Idem, p. 347.

Mid-Continent Fields

Fio. 128. — Generalized etrategraphic Hcction showinK rocka exposed in notthwestem part of Fawhuska quadrangle, Oklahoma, (After HeaM.)

into Osage County. The Copan pool, about 7 miles north of Dewey, is practically continuous with this field, as are also the Hchooter pool, to the southeast, and the Avant- Ochelata pool, to the southwest. The oil is found in Cherokee sands. The producing area seems in general to be closely associated with very gentle anticlinal folding, but the folds are low and generally lack sharp definition. The production of wells in this field is indicated by Fig. 127.

Oaage Couniy Pools. — Osage County adjoins Washington County on the west. The eastern and southern parts of the county have been drilled, and a number of pools have been discovered, among them the Back Creek, Nelagoney, Wynona, Big Heart, Delaware, Bird Creek, Flatrock, Hominy, and Cleveland (in part). Federal restrictions have checked development of a large area in this county, which is rarded as probably the most favorable for prospecting in Oklahoma. The area is now being surveyed (1919) by the United States Geolceal Survey, and structure contour maps of the townships are issued from time to time. Subsequently the land is auctioned by the Federal officers. Struc-

298 Geology Of Petroleum

turally the area is part of a monocline, on which many small domes, anticlines, and terraces are developed. There are many small faults, most of which strike northwest. The rocks that crop out are Pennsylvanian, and the oil and gas are found mainly in the Cherokee beds. In the Hominy field oil is said to be derived from the Mississippian limestone.

The Pawhuska quadrangle is in Osage County, just west of the Bartlesville field. The section is shown as Fig. 128. The general structure of the region is monoclinal. The rocks dip almost due west at an average rate of about 35 feet to the miles but the dip is not uniform. In some localities the rocks dip westward at triple the average rate, and in others the westward dip is very low. A number of small anticlinal folds are known, some of which yield oil and gas.

Kay County Pooh. — Ponca City, Newkirk, and Blackwell are in Kay County, near the Kansas line. The southwest corner of Kay County lies in the Permian Red Beds; the rest of the county is occupied by other Permian rocks. The Pennsylvanian series is found in normal development below the Permian, and the oil and gas are obtained in sands of the Cherokee formation. The Ponca City, Newkirk, and Blackwell fields are on domes or high places on an anticlinal axis. The oil and gas occur in several sands, as noted below:

BiUingSf Noble County, — The Billings field, in Noble County, lies about 20 miles southwest of the Ponca City field. The surface rocks are Permian shale, sandstone, and limestone, which together constitute 500 to 900 feet of beds above the Neva limestone. An anticline that plunges southwest carries a small dome on its southwest end; on this dome gas was encountered in 1916. Subsequently gas wells were brought in to the northeast, high on the anticline. This fold (Fig. 129) has approximately the same strike as the fold just south of Ponca City, and possibly both are on the same axis.

Heald, K. C. : Geologic Structure of the Northwestern Part of the Pawhuska Quadrangle, Oklahoma. U. S. Geol. Survey Bull 691, pp. 67-100, 1918.

Ohern, D. W., and Garrett, R E. : The Ponca City Oil and Gas Field, Oklahoma. Oklahoma Geol. Survey Bull 16, 1915. See also Petroleum and Natural Gas in Oklahoma. Oklahoma Geol. Survey , 19, part 2, pp. 248-280, 1917.

Fath, a. E. : An Anticlinal Fold Near Billings, Noble County, Oklahoma. U. S. Geol. Survey Bull 641, pp. 121-138, 1916.

Mid-Continent Fields

R.2W.

Legend

Outcrops of key beds used in determining structure; smalljercots irtdicate location inferred

Structure contours rep'-- r jj ing elevation above sea level or lowest prominent outcropping limestone bed; dashed line indicates location not certain

"7 I Approximate direction of

KAY 'county NOBlfTtOUNiy

Fig. 129. — Sketch showing the anticlinal fold near Billings, Oklahoma.

(After Faih.)

Geology Of Petroleum

Oil and Gas Sands in the Blackwell Field, Oklahoma

Name

Sand. . . .

Sand

Sand

Sand

Blackwell

Sand. . . .

Sand

Newkirk.

Sand

Sand

Ponca . . .

Sand

Sand. . . .

Sand

Sand. . . .

Sand

Sand

Sand. . . .

Swenson .

Thick-

Average

Character

neas

Depth

Feet

Feet

Gas.

Gas.

Gas.

Gas.

Gas.

Gas.

Gas.

Water and gas.

Gas.

Water.

Gas.

Showing of oil.

Gas, showing of

oil.

Water.

2,300

Gas, showing of

oil, water.

Water.

Gas, showing of

oil.

Gas, showing of

3,275

oil, water.

Oil.

Correlation

275-ft. sand at

Ponca City. 470-ft. sand at

Ponca City. 550-ft. sand at

Ponca City. 975-ft. sand at

Ponca City.

1 .550-ft. sand at Ponca City.

Lay ton of Gushing.

Cleveland.

Peru.

Oswego (Wheeler).

Garher, Garfield County. — The Garber field is in Garfield County a few miles southwest of Billings. The surface rocks are Permian Red Beds, and the structure is domatic. Gas and some oil were encountered in Permian beds and in the upper part of the Pennsylvanian series in 1916. Deeper drilling has revealed many productive sands, containing high-grade oil.

Muskogee County Pools, — The Muskogee oil field (Fig. 130) is

*Tapp, J. a., and Shaler, M. K.: Notes on the Geology of the Muskogee Oil Fields, Indian Territory. U. S. Geol. Survey BidL 260, p. 441, 1905.

Mid-Continent Fields 301

situated near and southwest of Muskogee. Oil was discovered here in 1894, when two wells were drilled. In one pf these wells oil was encountered in sand at a depth of 665 feet. This sand,

TopofasndBtcinelZOa Faulli OUwelli

Fig. 130.— Map of Muskogee oil field, Oklahoma. (Afler Taff and Shaler.)

after being shattered by an explosive, yielded 12 barrels of oil a day. Another sand, encountered at 1,100 feet, produced 60 barrels after shooting. The oil is of high grade {42° Be.) It is found

Geology Of Petroleum

LoQ OF Enid , in the Nobthwebt Corner of Sec. 30, T. 23 N., R. 6 W.,

Garfield Coitntt, Oklahoma**

Surface

Red sand and shale . .

Lime shell

Red and sandy shale

Shale

Lime

Shale

Lime shell

Slate and rotten shale

Lime

Slate

Lime

Slate

Lime shell

Slate

Sand

Red rock

White slate

Limestone

Red rock

Slate, white

Red rock

White slate

Red rock

Slate, white

Red rock

Lime

Lime, black

Slate, white

Lime

Slate, black

Thickness

Fdet

Depth

Feet 2,550 2,580 2,580 2,590 2,595 2,605

Red rock

Lime , . .

Red rock

Slate, white

Lime

Slate, white. . . .

Lime

Slate, white. . . . Slate cave, black Slate, white. . . .

Lime

Slate, white.. . .

Lime

Slate, white. . . .

Lime

Slate, white. . . .

Lime

Slate, white. . . . Lime shells. . . .

Slate

Lime shells. . . .

Slate.

Lime shells. . . .

Slate

Lime

Slate

Lime

Sand

Slate

Lime and slate . Water at

Thick-

Feet

Depth

Feet 2,685

<*Oklahoma Geol. Survey Bull. 19. part 2, p. 200, 1017.

in sandstones that occur near the base of the Pennsylvanian series. The productive sand is 19 feet thick.

Structurally the region is rather complex, although the rocks are not highly tilted. About 6 miles west of Muskogee and 2 miles

Mid-Contineut Fields 303

east of Taft gas is found in the lower part ol the Pennsylvanian, where the rocks are arched to form a .dome. Near Boynton, 6 miles southwest of Taft, oil is concentrated in a dome.

Via, 131. — Curves showing rafea of decline ot the Okmulgee-Morris district, Hamilton Bwilch field and ot Muskogee pool, Oklahoma. Inset map sbowiiw the location of 1, the Gushing field; 2, the Glenn pool; 3, the Hamilton Switch field; 4, the Okmuee-Moma diBtriet; 5, the Muskogee pool. {After Beat.)

304 Geology Of Petroleum

Okmulgee County FielcU. — From Muskogee the rocks dip estward to Okmulgee County, where several highly productive pools are developed. Some of these are on very low anticUnes. This region has recently come into considerable production. Decline curves for the Okmulgee-Morris district and the Muskogee pool are shown in Fig. 131.

According to report considerable oil has recently been encountered in or below the Mississippian linaestone in the Beggs pool.

References for Oklahoma

Adams, G. I.: The Carboniferous and Permian Age of the Red Beds of Eastern Oklahoma from Stratigraphic Evidence. Am. Jour. Sci.y 4th ser., vol. 12, pp. 383-386, 1901.

Lithologic Phases of the Pennsylvanian and Permian of Kansas,

Indiat Territory, and Oklahoma. Science new ser., vol. 15, No. 379, pp. 545-546, 1902.

AuRiN, Fritz: Correlation of the Oil Sands of Oklahoma. Oklahoma Geol. Survey Circular 7, pp. 1-16, chart, 1917.

Geology, of the Red Beds of Oklahoma. Oklahoma Geol. Survey Bull. 30, pp. 1-66, 1917.

Beede, J. W. : The Bearing of the Stratigraphic History and Invertebrate Fossils on the Age of the Anthracolithic Rocks of Kansas and Oklahoma. Jour. Geology, vol. 17, pp. 710-729, 1909.

Origin of the Sediments and Coloring Matter of the Red Beds of

Oklahoma. Science, new ser., vol. 35, No. 896, pp. 348-350, 1912.

Beal, C. H. : Geologic Structure in the Gushing Oil and Gas Field, Oklahoma, and Its Relation to Oil, Gas, and Water. U. S. Geol. Survey BvU. 658, pp. 1-64, 1917.

BuTTRAM, Frank: The Gushing Oil and Gas Field, Oklahoma. Oklahoma Geol. Survey BuU. 18, pp. 1-64, 1914.

Fath, a. E.: Structure of the Northern Part of the Bristow Quadrangle, Creek County, Oklahoma, with Reference to Petroleum and Natural Gis. U. S. Geol. Survey Bull. 661, pp. 69-99, 1918.

Gardner, J. H.: Oil Pools of Southern Oklahoma and Northern Texas. Econ. Geology, vol. 10, pp. 422-434, 1915; Geol. Soc. America Bull., vol. 26, p. 102, 1915.

The Mid-Continent Oil Fields. Geol. Soc. America Bull., vol.

28, pp. 685-720, 1917.

Gould, C. N. ; Stratigraphy of the McCann* Sandstone. Kansas Univ. Quart , pp 175-177, 1900

Notes on the Geology of Parts of the Seminole, Creek, Cherokee,

and Osage Nations. Am. Jour. Sci., 4th ser , vol. 11, pp. 185-190, 1901.

On the Southern Extension of the Marion and Wellington Formations. Kansas Acad. Sci. Trans., vol. 17, pp. 179-181, 1901.

Geology and Water Resources of Oklahoma. U. S. Geol. Survey

Water-Supply Paper 148, 1905.

Mid-Continent Fields 305

Gardner, J. H. : Petroleum and Natural Gas in Oklahoma. Econ. Geology , vol. 7, pp. 719-731, 1912.

Petroleum in the Red Beds. Econ, Geology, vol. 8, pp. 768-780,

' The Occurrence of Asphalt in the State of Oklahoma. Royal

Soc. Arts Jour., vol. 63, pp. 132-134, 1915.

Haoer, Dorset: Gas Pressures and Water Pressures in Oklahoma. Fud OH Jour., vol. 6, p. 64, April, 1915.

Geological Features of the Oklahoma Oil Fields. Western Eng.,

vol. 6, pp. 13-14, 1916.

Hutchinson, L. L. : Rock Asphalt, Asphaltite, Petroleum, and Natural Gas in Oklahoma. Oklahoma Geol. Survey Bull. 2, pp. 1-256, 1911.

Johnson, R. H., and Huntley, L. G.: The Equilibrium Theory of Gas Pressures, a Reply to Hager. Fuel Cil Jour., vol. 6, p. 76, May, 1915.

Kirk, C. T. : A Preliminary Report on the Contact of the Permian with the Pennsylvanian in Oklahoma. Oklahoma Geol. Survey Third Bienn. Rept, for 1903, pp. 6-14.

MuNN, M. J. : Reconnaissance of the Grandfield District, Oklahoma. U. S. Geol. Survey Bull. 647, pp. 1-86, 1914.

Ohern, D. W. : Stratigraphy of the Older Pennsylvanian Rocks of Northeastern Oklahoma. Oklahoma Univ. Research Bull. 4.

and Garrett, R. E. : The Ponca City Oil and Gas Field. Oklahoma Geol. Survey Bull. 16, 1915.

Powers, Sidney: Age of the Oil in Southern Oklahoma Fields. Am. Inst. Mm. Eng. Bull. 113, p. 1982, November, 1917.

The Healdton Oil Field, Oklahoma. Econ, Geology, vol. 12,

pp. 694-606, 1917.

Shannon, C. W., and others : Petroleum and Natural Gas. Oklahoma Geol. Survey Bull. 19, part 2, pp. 1-536, 1917.

Shannon, C. W., and Trout, L. E.: Petroleum and Natural Gas in Oklahoma. Oklahoma Geol. Survey Bull. 19, part 1, pp. 1-133, 1916.

Smith, C. D : Structure of the Fort Smith-Poteau Gas Field, Arkansas and Oklahoma. U. S. Geol. Survey Bull 641, pp. 23-33, 1914.

The Glenn Oil and Gas Pool and Vicinity, Oklahoma. U. S.

Geol. Survey Bull. 641, pp. 34-48, 1914.

Snider, L. C : Geology of a Portion of Northeastern Oklahoma. Oklahoma Geol. Survey BuU. 24, part 1, pp. 1-122, 1915.

Tafp, J a : U S. Geol. Survey Geol. AUas, Coalgate folio (No. 74), 1901.

— U. S. Geol. Survey Ged AUas, Tishomingo folio (No. 98), 1903.

Grahamite Deposits in Southeastern Oklahoma. U. S. Geol.

Survey BuU. 380, p. 286, 1909.

Tapp, J, A., and Shaler, M. K. : Notes on the Geology of the Muskogee Oil Field. U. S. Geol. Survey Bull 260, pp. 441-446, 1905.

Trout, L. E., and Myers, G H.: Bibliography of Oklahoma Geology. Oklahoma Geol. Survey Bull. 26, pp. 1-105, 1915.

Wallis, B. F. : The Geology and Economic Value of the Wapanucka Limestone of Oklahoma, with Notes on the Economic Value of Adjacent Formations, Oklahoma Geol Survey Bull 23, pp. 1-102, 1915.

306 Geology Of Petroleum

Wbgbmann, C. H. : The Duncan Gas Field, Stephens County, Oklahoma. U. S. Geol. Survey BvU. 621, pp. 43-60, 1915.

Anticlinal Structure in Parts of Cotton and Jefferson Counties,

Oklahoma. U. S. Geol. Survey BvU. 602, 1915.

The Loco Gas Field, Stephens and Jefferson Coimties, Oklahoma. U. S. Geol Survey Bull 621, pp. 31-42, 1915.

Wbgemann, C. H., and Heald, K. C: The Healdton Oil Field, Carter County, Oklahoma. U. S. Geol. Survey Bull 621, pp. 13-30, 1916.

Wbgemann, C. H., and Howell, R. W.: The Lawton Oil and Gas Field, Oklahoma. U. S. Geol. Survey Bull 621, pp. 71-86, 1916.

Arkansas

The Fort Smith-Poteau gas field is south of Fort Smith, in Arkansas and Oklahoma. Natural gas was discovered some years ago in Massard Prairie, 5 miles southeast of Fort Smith, and also about 2 miles southeast of Mansfield, Arkansas, and more recently it has been found 3 miles east of Poteau, Oklahoma.

The rocks are Pennsylvanian. The oldest formation in the region described by Smith is the Atoka, a series of alternating shales and sandstones 6,000 to 7,000 feet thick. The sandstone constitutes but a small part of the formation and lies in zones about 100 feet thick, separated by beds of shale 1,P00 to 1,200 feet thick. In some areas the formation consists almost entirely of shale; in others the beds of sandstone are thick and massive. Above the Atoka is the Hartshorn sandstone, from 100 to 200 feet thick, followed by the McAlester shale, from 2,000 to 2,500 feet thick. The Savanna formation, which overlies the McAlester, consists of three prominent zones of sandstone, each ranging in thickness between 100 and 200 feet, separated by masses of shale. Its total thickness is estimated at 1,200 to 1,500 feet. Above the Savanna is the Boggy shale, about 2,300 feet thick, which contains also about 400 feet of sandstone.

The country lies between the complexly folded and faulted Ouachita Mountains, to the south, and the gently tilted Boston Mountains, to the north. The rocks are thrown into rather steep

"Smith, C. D. : Structure of the Fort Smith-Poteau Gas Field, Arkansas and Oklahoma. U. S. Geol. Survey Bull 541, p. 23, 1914.

Collier, A. J. : The Arkansas Coal Field. U. S. Geol. Survey BuU. 326,

Taff, J. A., and Adams, G. I. : Geology of the Eastern Choctaw Coal Field, Indian Territory. U. S. Geol. Survey Twenty-first Ann, Repl, part 2, pp. 257-311, 1900.

k k

Mid-Continent Fields 307

folds; anticlines alternating with synclines. There are also strike faults.

Three areas in this region yield gas. Each is at the crest of an anticline. The principal reservoirs are the Hartshorn sandstone and the sands in the Atoka formation.

Kansas

In Kansas, which contains the northern part of the Mid-Continent field, the geologic conditions are essentially similar to those in Oklahoma, already described. The rocks that crop out in Kansas are all sedimentary beds. The oldest rocks are Mississippian strata, which are exposed only in the southeast corner of the State. To the west and north is a broad area of Pennsylvanian strata that extends to the north boundary. West of that is a belt of Permian beds, narrow at the Nebraska line and very broad at the Oklahoma line. West of the Permian belt is a broad area of Mesozoic and Cenozoic beds that extends to the west border pf the State.

The oil and gas are found mainly in the Cherokee formation, which is the principal producing formation in northern Oklahoma, and the fields exhibit similar structural features. In Kansas the production of gas is relatively important. The Kansas fields are near great industrial centers. The readily accessible market of Kansas City, Missouri, and the development of zinc-smelting, elay-buming, and glass and cement manufacturing plants in Kansas have greatly stimulated gas exploration in these fields.

The strata of Kansas dip northwest, away from the Ozark uplife, in general at the rate of 30 feet to the mile or less. The deposits are on the great westward-dipping monocline, and the minor structural features that localize the accumulations are mainly anticlines, domes, flutings on monoclines, or structural terraces.

'Haworth, Erasmus, and others: Special Report on Oil and Gas. Kansas Geol. Survey, vol. 9, pp. 1-586, 1908.

ScHRADER, F. C, and Ha worth, Erasmus: Economic Geology of the Independence Quadrangle, Kansas. U. S. Geol. Survey Bull. 296, pp. 1-74, 1906.

Adams, G. I., Ha worth, Erasmus, and Crane, W. R. : Economic Geology of the lola quadrangle, Kansas. U. S. Geol. Survey Bull, 238, pp. 1-83, 1904.

Orton, Edward: Geological Structure of the lola Gas Field. Geol, Soc. America BuU., vol. 10, pp. 99-106, 1899.

Adams, G. I.: Oil and Gas Fields of the Western Interior and Northern Texas Coal Measures and of the Upper Cretaceous and Tertiary of the Western Gulf Coast. U. S. Geol. Survey Bull, 184, pp. 1-64, 1901.

Geology Of Petroleum

In Kansas granite occurs at relatively shallow depths on some of the domes. At Elmdale, Onaga, Wabaunsee, and Zeandale granite is encountered at stratigraphic horizons as high as 1,000

Fig. 132. — Diagram showing limestones thinning out southwestward from Kansas to Oklahoma. (After Schroder arid Haworth.)

feet above the base of the Pennsylvanian series. At most places

there is no evidence of metamorphic action in the beds immediately

Taylor, C. H. : The Granites of Kansas. Southwestern Assoc. Petrol. Geologists BuU.f vol. 1, pp. 111-X26, 1917.

Mid-Continent Fields 309

overljring the granite. It is believed that the granite represents old knobs or probably ridges, that were submerged in the Pennsylvanian sea and ultimately covered by sedimentary material. At a later period these points, which were lines of weakness, became loci of movement so that the strata above them were folded. The dome at Elmdale, according to Gardner, shows a reverse dip of nearly 300 feet at angles as steep as 5°. The depth from the present surface to the top of the granite ranges from 950 feet on the fold at Zeandale to 2,500 feet on the dome near Cottonwood Falls or Elmdale.

In Kansas the Pennsylvanian contains more limestone than in Oklahoma. The limestones, as shown by Fig. 132, thin out toward the Oklahoma boundary.

General Stratigraphic Section in the Oil and Gas Region op Kansas (After Haworth, Adams, Schrader, Gardner, and Others)

Pennian series:

1. Red and gray sandstones with beds of red and vari-colored Feet

shale. Includes salt and gypsum in upper portion 1,000-1,500

2. Wellington shale 75-150

3. Marion limestone 100-200

4. Winfield formation; limestone and shale 20-30

5. Doyle shale 50-70

6. Fort Riley limestone; crops out at Augusta 40-50

7.- Florence flint 15-25

8. Matfield shale 60-70

9. Wreford limestone (base of Permian, according to Prosser

and to Adams) 35-55

10. Neosho formation and Florence shale or Garrison formation 140-150

11. Cottonwood limestone 5-10

12. Eekridge shale 30-40

13. Neva limestone 5-15

14. Elmdale formation; shale and limestone (base of Permian

according to Beede) 120-140

Pennsylvanian series:

1. Americus limestone 6-10

2. Admire shale; probably includes oil sand at a depth of about

650feetat Eldorado 275-325

3. fimporia limestone. 5-10

4. Willard shale 60-190

/Gardner, J. H. : The Mid-Continent Oil Fields. Geol. Soc. America BvU., vol. 28, p. 690, 1917. Op. cit., p. 691.

Geology Of Petroleum

Feet

5. Burlingame limestone &-12

6. Scranton shale 160-180

7. Howard limestone 2-7

8. Severy shale 40-60

9. Topeka limestone 20-25

10. Calhoun shale 0-50

11. Deer Creek limestone 20-30

12. Tecumseh shale 40-70

13. Lecompton limestone 15-30

14. Kanawa shale 50-100

15. Oread limestone 10-25

16. Lawrence shale; includes Chautauqua sandstone member,

which is the most persistent bed of sandstone in this portion of section. Probably to be correlated with the surface bed at Toronto. Occurs at 1,550 feet in wells at

Augusta and Eldorado 200-300

17. Kickapoo limestone 5-15

18. Le Roy shale 60-100

19. Stanton limestone 20-40

20. Vilas shale. 5-125

21. Allen limestone 6-75

22 Lane shale 30-150

23. lola limestone 2-44

24. Chanute shale 2G-30

25. Drum limestone 3-70

26. Cherryvale shale. About the'horizon of the oil sand occurr-

ing at 2,450 feet at Augusta and Eldorado {Gardner) . . . 40-50

27. Dennis limestone, Galesburg shale, and Mound Valley

limestone 80-100

28. Ladore shale 20-25

29. Bethany Falls limestone 15-25

30. Pleasanton shale 20-60

31. Coffeeville limestone 40-60

32. Wahiut shale 20-140

33. Altamont limestone 25-60

34. Bandera shale 60-110

35. Pawnee limestone. Horizon of Peru oil sand 10-65

36. Labette shale 25-30

37. Fort Scott (Oswego) limestone 20-70

38. Cherokee shale. Includes main oil sands of Kansas out-

side of Augusta and Eldorado regions. Contains Bar-

tlesville and Burgess sands 375-400

Mississippian series:

Limestone, calcareous shale and chert shown in Neosho well.

Boone formation 320

Mid-Continent Fields

Probably older than Mississippian:

1. Dolomitic limestone, sandstone, and chert in Neosho well. .

3. Conglomerate and shale in Neosho well

4. Sandstone, conglomeratic with pebbles up to three-quarters

inch in diameter; shown in Neosho weU

uJL., 11

:i..-J — .:i4,- JLf3_-l-— r' — — -L

5:

I §

I:

I ! I -;r-i

s

Feet

1,823

The structural features are in general similar to those of the Oklahoma fields. The principal fields are shown in Fig. 133, and sections are given in Fig 134.

312 Geology Of Petroleum

In the Peru region, lying mainly in Chautauqua County, but extending eastward into the western part of Montonaery County,

Mid-Continent Fields 313

oil is accumulated on a great structural terrace where the beds lie practically flat. For 25 miles down the dip the rocks dip 4 feet to the mile. West of this terrace for 25 miles the dip is about 50

giiy

Fio.. 135.— Map and section of Augusta and Eldorado fields, Butler County,

Kansas. Contours are based on outcrop of Fort Riley limostone. (After

Hager, Hales and Wider.)

314 Geology Of Petroleum

feet to the mile, and east of it for 25 miles it is about 30 feet to the mile.

In the Independence quadrangle, Montgomery County, which lies just east of the Peru pool, between Independence and Coffeyville, there is an extensive area yielding oil and gas which is situated on the crest and well down the flanks of a gentle anticlinal fold. In Wilson County (Fredonia pool) and in Woodson County, to the north, gas and some oil are found on subordinate folds that rise not more than 50 feet above the general plane of the monocline. In the lola quadrangle, Allen and Neosho Counties, accumulations occur on the monocline in gentle structural ravines and terraces with axes that strike approximately with the beds. In the lola and La Harpe field, in northern Allen County, there is a low anticline or terrace about 8 miles wide.

The Paola field, in Miami and Franklin Counties, is on a terrace where for 40 miles down the dip of the monocline the beds dip 5 feet to the mile. West of this area in Osage County, the dip is about 20 feet to the mile.

In the Eldorado and Augusta fields, Butler County (Fig. 135), the oil and gas have accumulated in well-defined domes that are superimposed on the monocUne.

Pools have recently been developed at Elbing, Peabody and

Florence.

Missouri

Small quantities of oil and gas have been produced near Kansas City, Missouri, in Cass and Jackson Counties, which lie on the west border of the State. The outcropping rocks are of Pennsylvanian age. These strata extend to depths of 650 to 875 feet or more. The series is divided into two groups of rocks classified as the upper or Missouri group and the lower or Des Moines group. The exposed strata belong chiefly to the upper group, but only its lowest formation, the Kansas City, is present. The limestone members of this formation crop out conspicuously over nearly all of the area.

The regional dip of the rock beds is northwest, off the flank of

the Ozark dome. This dip is, however, very low, the average

across Jackson and Cass Counties being only from 6 to 10 feet in

a mile.

Wilson, M. E. : Oil and Gas Possibilities in the Belton Area. Missouri Bur. Geology and Mines, 1918.

Mid-Continent Fields

1 —

Seriei Group

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Member

Section

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Character of Rock

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BatlwBT Falli Itmeftyne

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difisas.

I I I I I '~r"

155+

Chiefly alternating ahale and aandatone with thin non, peraiateut limeatonei

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Chiefly limestoue with chert

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Geology Of Petroleum

In the region near Belton and Hickman Mills there are a number of low anticlines, domes, monoclines, terraces, and synclines. Southwest of Belton there is a small area of complicated faulting. In several wells sunk to depths of about 400 feet oil or gas or both have been encountered. In 1909 five wells produced about 300 barrels a month of a heavy oil with paraffin base which commanded a good price for use as lubricating oil. The oil was obtained from sands near the bottom of a shallow syncline. A section of the rocks is shown in Fig. 136.

Red River Region, Oexahoma And Texas

General Features. — The Red RiVer region of southern Oklahoma and northern Texas (Fig. 137) includes parts or all of Carter, Love, Stephens, Jefferson, Cotton, and Comanche Counties, Oklahoma, and Clay, \ichita, and Wilbarger Counties, Texas. The

-T 1 1 1

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Fig. 137. — Index map of Red River region, Oklahoma and Texas.

Red River oil and gas pools include the Healdton, Fox, Graham, Loco, Duncan, and Lawton pools in Oklahoma, and the Electra, Burkburnett, and Petrolia fields of Texas. In this region, as shown by the contact of Pennsylvanian with Permian rocks (Fig. 118, p. 272) there is an embayment in the Permian outcrop south of the Arbuckle Mountains near the Red River. In the region of this embayment there is a great synclinal trough. The beds dip southward from the Arbuckle Mountains and northwestward from the Llano uplift, in the region south of the Red River. The axis of the syncline plunges west. Superimposed on the larger synclinal basin and probably crossing it, is the great Red River zone

Mid-Continent Fields 317

of deformation, which here has been identified, mainly by drilUng. It extends along Red River and through counties that border the river for over 100 miles. This great uplift is probably of pre- Pennsylvanian age, according to Hager, who states that minor anticlines and domes such as those that exist at Electra and Petrolia, are due to movements of readjustment along old lines of stress in highly folded Ordovician rocks beneath. The less intense deformation took place in Post Pennsylvanian time.

The surface rocks are of Permian age, and the oil and gas are produced mainly from underlying Pennsylvanian strata, although the lower Permian also supplies gas and some oil. Possibly some of the oil has come from strata lower than the Pennsylvanian.

General Stratigraphic Section South of the Arbuckle Mountains

IN Oklahoma'*

Lower Cretaceous (Comanche series) : Feet

1. Silo sandstone 200

2. Pennington limestone 10-15

3. Bokchito formation 140

4. Caddo limestone 60

5. Kiamichi formation 150

6. Goodland limestone 25

7. Trinity sand, which includes the sand yielding light oil in

MadiU field and the gas sand at Woodville 200-400

Unconformity.

Permian:

Red sandstone, varicolored shale, and beds of clay-iron conglomerate with thin lenses of limestone 400-1,500

Unconformity.

Pennsylvanian:

1. Franks conglomerate. Limestone (Wapanucka) at top.

Beds of chert, gravel, boulders, and sandstone; formation

of local extent near mountains . 500

Unconformity.

2. Glenn formation; blue shale with lenticular beds of sand-

stone. Probable horizon of the main oil sand, Healdton

field 1,000-3,000

Unconformity.

Hager, Lee: Red River Uplift Has Another Angle. Oil and Gas Jour., vol. 18, pp. 64-65, 1919.

'Tafp, J. A.: U. S. Geol. Survey Geol. Atlas, Tishomingo folio (No. 98), 1903; Some Economic Notes by Gardner. Geol. Soc. America BvUL, vol. 28, p. 697, 1917.

Geology Of Petroleum

Mississippian: Feet

1. Caney shale. Top is blue shale with sandy lentils and

lower portion is black fissile shale with concretions of

dark-blue fossiliferous limestone 1,500

2. Sycamore limestone 0-160

Devonian: Woodford chert 600

Silurian:

1. Hunton limestone O-200

2. Sylvan shale. Blue clay shale 50-300

Ordovician:

1. Viola limestone: white and bluish 750

2. Simpson formation; siliceous sandstone, bituminous sand-

stone, fossiliferous limestone, calcareous sandstone and shale. Possibly contains deep oil sand near center of Healdton field, according to Powers 1,600

Cambro-Ordovician :

Arbuckle hmestone; massive and thin bedded, white and light

blue limestone with cherty concretions 4,000-6,000

Cambrian:

Reagan sandstone; coarse dark brown sandstone with calcareous sandstone and shale at top 50-150

Pre-Cambrian: Granite.

General Stratigraphic Section in Northern Texas (After Paige, Hill, and Others, with Economic Notes by Gardner, Matteson,

and Others) Tertiary (Eocene): Feet

1. Cook Mountain and Mount Selman (St. Maurice of Louisi-

ana, Claiborne). Consists of clays, clay-iron conglomerates, and calcareous glauconitic beds.

2. Wilcox group (Sabine formation). Sands, clays, and con-

glomerates with beds of lignite 400-500

3; Midway group. Chiefly clays with some limestone 200-300

Upper Cretaceous (Gulf series) :

1. Navarro group. Clay marls and glauconitic sands. .

2. Taylor marls group. Beds of clay and sandy to calcareous

soft shale, with local lenses of sandstone. Contains Nacatoch gas sand of Caddo field, oil sands of Corsicana field, and oil-bearing igneous rock (tuflF?) of Thrall field 200-500

3. Austin group (Annona chalk and Brownstown marl). Con-

tains some oil and gas in Caddo field

Mid-Continent Fields

4. Eagle Ford group. Chiefly clays containing the Blossom Feet

oil sand of Caddo field 150-400

5. Woodbine sand. Massive soft sandstone with some shale.

Main oil sand of Caddo oil field. Occupies approximate time interval of Dakota sandstone in New Mexico and northward into Canada 60-100

Lower Cretaceous (Comanche series) :

1. Washita group. Impure limestone with beds of shale and

marl. Contains water sand locally at Paris, Texas; includes, in descending order, the Pennington limestone, Bokchito formation, Caddo limestone, and Kiamichi formation (Denison, Fort Worth, and Preston formations) 175-400

2. Fredericksburg group. Massive white limestone beds, in-

cluding the Goodland limestone (Edwards limestone and

Walnut formation) 25-200

3. Trinity sand. Contains the oil of the South Bosque field

in top member 200-400

Permian:

1. Double Mountain group. Sandstone, limestone, sandy

shale, red and blue clays, with beds of gypsimi and salt. 1,800-2,000

2. Clear Fork group. Thin-bedded sandstone, magnesian

and carbonaceous limestone, red and blue clay shale and irregular beds of cemented clay-iron concretions. Some gypsum 1,500-2,000

3. Wichita group. Sandstone of various colors. Red and

bluish clay shale and beds of clay-iron concretions or ''Mud-lump conglomerate." Beds of limestone rare east of Baylor County. Correlated with limestone and shale series known as the Albany formation in Baylor County 1,250-2,000

Pennsylvanian:

1. Cisco group. Sandstone, limestone, gray sandy shale,

dark-gray shale, and conglomerate. Contains coal 7. Includes upper oil and gas sands in Petrolia and Electra fields. . 800-900

2. Canyon group. Sandstone, dark-blue shale, conglomerate,

coal, and beds of massive escarpment-forming limestone. Includes lower oil and gas sands in Electra and Petrolia fields 800-950

3. Strawn group. Sandstone, clay, carbonaceous shale, and

chert conglomerate. Includes Millsap formations, or beds for 1,000 feet below coal 1. Contains oil and gas sands in Strawn, Ranger, Moran, and Brownwood fields 950-3,700 Unconformity.

320 Geology Of Petroleum

Mississippian (Bend series) : Feet

1. Smithwick shale. Black shale. Contains sand lenses

that according to Matteson, yield oil in Allen well, east

of Ranger, and in Black well, northern Stephens County 175-600

2. Marble FaUs limestone. Bituminous limestone, and some

shale. Oil and gas in Ranger and Electra fields and deep sands of Burkburnett pools. Contact with Smithwich yields oil in Ranger and Caddo pools 350-400

3. Lower Bend shale. Black shale 0-125

Unconformity.

Ordovician:

1. EUenberger limestone 400

Healdton, Oklahoma. — Healdton, Carter County, Oklahoma/ hes to the south of the Arbuckle-Wichita uplift and is about 12 miles southwest of the Arbuckle Mountains. Petroleum was discovered here in 1913, and the field was developed within three years to one of the most productive fields in Oklahoma, yielding daily over 60,000 barrels. The rocks at the surface are Permian Red Beds and consist of red aind gray shale, alternating with brown, white, and red sandstone and thin conglomerate beds. The beds, according to Wegemann and Heald, are at least in part of fresh-water origin. From the surface to a depth of 600 to 950 feet the strata are principally shales, with a few water-bearing sandstones. Below these beds is a zone 250 feet thick which contains four or more petroliferous sands separated by beds of shale. In some wells five sands contain oil. Most of the oil produced in 1915 came from sands 800 to 1,150 feet deep. The higher petroliferous strata are classified as Permian by Wegemann and Heald, and also by Aurin.' Powers, however, classes them as Pennsylvanian. The deeper oil-bearing strata are Pennsylvanian.

Structurally the field is an anticline on which several small domes are superimposed. The oil has accumulated at the top of

Wegemann, C. H., and Heald, K. C: The Healdton Oil Field, Carter County, Oklahoma. U. S. Geol. Survey Bull 621, pp. 13-30, 1915.

Powers, Sidney: The Healdton Oil Field, Oklahoma. Econ. Oeology, voL 12, pp. 694-606, 1917; Age of the Oil in Oklahoma Fields. Am. Inst. Min. Eng. Bull. 113, p. 1982, 1917.

Shannon, C. W., and others: Petroleum and Natural Gas in Oklahoma. Oklahoma Geol. Survey Bull. 19, part 2, pp. 79-101.

20p. city p. 24.

'Shannon, C. W., and others: Op, a7., insert table.

Mid-Continent Fields 321

the anticline, on the domes, and in the small structural depressions between them. On the flanks of the fold the beds carry salt water. Figs. 29 and 30 (pp. 124-125) are a structure map and a stereogram by Wegemann and Heald. Possibly a small part of the oil is derived from the Ordovician beds, which are covered by the Carboniferous beds. (See Fig. 138.)

Powers* states that an angular unconformity separates the Ordovician from the Pennsylvanian rocks, the former being tilted at considerably higher angles. The deeper sands, which have proved highly productive around the outer margins of the field, are lacking in its center, where pre-Pennsylvanian rocks only are found below the higher sands (Fig. 138).

At Fox and at Graham, which lie north of the Healdton field, the surface rocks are Permian. The Permian is thicker than at Healdton, and the oil-bearing strata lie at greater depths. The petroliferous beds are at approximately the same horizons. Anticlines are developed at Fox and at Graham (Fig. 138), but these

Heale/fvn

Fig. 138. — Cross section of the Healdton field, Fox and Wheeler anticlines. Oklahoma, showing the relation of the buried Healdton Hills composed of Ordovician strata to the overlying Pennsylvanian and Permian strata. Length of section 21 miles; vertical scale four times horizontal scale. {After Powers.)

pools, which lie farther from the basin, are much less productive than the Healdton field.

LocOy Oklahoma. — The Loco field is on the line between Stephens and Jefferson Counties, Oklahoma, about 3 miles southwest of the village of Loco and 10 miles northwest of the Healdton field. For many years asphalt deposits have been known to exist in the vicinity, but deep drilling was not begun until 1912. The first gas well was bored in the spring of 1913, about six months before the Healdton pool was discovered. Six other gas wells of capacities ranging from 6,000,000 to 20,000,000 cubic feet a day

Powers, Sidney: The Healdton Oil and Gas Field, Oklahoma. Econ, Geology, vol. 12, p. 604, 1917.

Wegemann, C. H. : The Loco Gas Field, Stephens and Jefferson Counties, Oklahoma. U. S. GeoL Survey BvU. 621, pp. 31-42, 1915.

322 Geology Of Petroleum

have been drilled. The rocks exposed in the Loco field are of Permian age and consist of sandstone, shale, and fine conglomerate. The structure is complicated, an anticline being crossed by a syncline. The gas occurs in sands, some of which are probably of Permian age. Recently some heavy oil has been discovered.

Dttncany Oklahoma. — The Duncan gas field, known also as the Hope field, is in Stephens County, Oklahoma, about 10 miles northeast of the town of Duncan The principal flow of gas is obtained at depths of about 850 feet, and the wells range in production from 3,000,000 to almost 18,000,000 cubic feet a day. A pipe line has been laid from the field to Duncan and supplies that town with gas.

The surface rocks in the Duncan field are Red Beds of Permian age. They consist of shale, sandstone, calcareous sandstone, and shale conglomerate. The shale is red or bluish gray in color. The sandstone is predominantly white or bufif but is in some places red. The cement of the sandstone is calcareous, and in some beds the lime content increases in amount until the rock is a calcareous sandstone.

The principal gas-bearing bed in the Duncan field, a sand from 7 to 19 feet thick, lies 800 to 900 feet below the surface. Showings of gas and heavy oil in small quantity are obtained in some of the wells in shallower sands. The gas accumulation lies in a steeply plunging anticline, which is about 2 miles broad by 5 miles long, and whose axis trends a few degrees west of north.

At Granite, Gotebo, and Wheeler oil or gas or both occur in or near the Red Beds close to the unconformity between the Pennsylvanian and the Permian.

Lawton, Oklahoma. — The Lawton oil and gas field, in Comanche County, Oklahoma, is near the east end of the Wichita Mountains, about 5 miles east of the city of Lawton. Oil was found in Lawton in 1901, in a well dug for water. The surface rocks are Red Beds, consisting of alternating layers of shale and sandstone and, associated with the sandstone, thin layers of shale conglomerate. The wells encounter red sandstone and shales.

Wegbmann, C. H. : The Duncan Gas Field, Stephens County, Oklahoma. U. S. Geol. Survey 621, p. 43, 1916.

*Wegemann, C. H., and Howell, R. W.: The Lawton Oil and Gas Field, Oklahoma. U. S. Geol. Survey BuU, 621, p. 71, 1915.

Mid-Continent Fields 323

The principal anticlinal aids in the Lawton field extends southeastward from the Wichita Mountaina and is interrupted by a narrow syncline, which crosses it almost at right angles.

Oil and gas are found in the wells of the Lawton field in three different sands, which are known in the field as the "200-foot," "400-foot," and "800-foot" sands. The "200-foot sand" is from 10 to 30 feet thick and lies at depths of 150 to 250 feet, according to the location of the well with reference to the Lawton anticline. This sand has been found in the greater number of the wells and generally carries at least a show of oil. Some wells are said to have obtained several barrels of heavy oil from this sand, and gas also is reported from it, though only in small quantity.

FiQ, 139.— Map showing geologic structure and distribution of wells in Cement field, Oklahoma. Contour lines show altitude of Cyril irypsum bed. Contour interval 50 feet. {After Clapp.)

In 1916 many wells were producing small amounts of oil. According to Wegemann and Heald, the oil is probably derived from Pennsylvanian strata, above which the Red Beds he unconformably.

Cement, Oklahoma.— The Cement field' is in Caddo County, Oklahoma, northeast of the Wichita Mountains and 60 miles

'Clapp, F. G. : Geology of Cement Oil Field. Min. and Met., No. 158, sec, 27, pp. 1-9, February, 1920.

324 Geology Of Petroleum

northwest of Healdton. It is in the Keeche Hills, which rise some 400 or 500 feet above the surrounding country. The field is on an anticline over 13 miles long and from 1 to 3 miles wide. The major axis trends N. 75 W. from the village of Cement, but east of the village appears to be deflected to about S. 45 E. (See Fig. 139.) The anticline has an undulatory crest, and several of the wells sunk at the high places on the crest have yielded much gas and some oil. The surface rocks are Permian Red Beds, with gypsmn. The base of the Permian series is thought to lie about 2,700 feet from the surface, but some place it at 1,700 feet. The oil and gas are found in the lower part of the Permian, in sandstones covered by shale.

Madilly Oklahoma. — The Madill pool, in Marshall County, Oklahoma, is just south of the Arbuckle uplift. The region includes the Tishomingo granite and Paleozoic and Cretaceous sediments. The Paleozoic sedimentary rocks rest unconformably on the eroded surface of the granite. They are folded and faulted and are overlain by the Cretaceous rocks, which are but slightly tilted. (See Fig. 140. ) The lowest and thickest Cretaceous formation is the Trinity sand. It is a compact but unconsolidated, moderately fine sand with a Uttle clay and bands of sandy clay.

Oil seeps and bituminous saturated sands are found in the region. The principal oU-bearing stratum is at or near the base of the Trinity sand, a little more than 400 feet below the surface at Madill. It is a porous bed of sand and gravel in which the particles and pebbles are not cemented.

Of four producing wells brought in to April 1909, one had an initial flow of several hundred barrels. The oil is very Ught, having a specific gravity of 47.5 B., and is rich in gasoline and kerosene. Taff and Reed believe that the oil and asphalt are derived from the Carboniferous strata which are tilted so that their edges project against the Trinity sand.

Wichita and Clay Counties, Texas. — The productive pools of Wichita County, Texas, include Burkbumett, Electra, Fowlkes, and Iowa Park. These pools are in areas of Permian rock, below which are strata of Pennsylvanian age.

Tapp, J. A. : U. S. Geol. Survey Geol Atlas, Tishomingo folio (No. 98), 1903. Tapp, J. A., and Reed, W. J. : The Madill Oil Pool, Oklahoma. U. S. GeoL Survey BvU, 381, pp. 504-513, 1910.

Mid-Continent Fields

Miflw

:§

i

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1—1

Scole:

326 Geology Of Petroleum

The Electra field is in the western part of Wichita County, neax the Oklahoma line. The first reported occurrence of oil in this field was in a well dug in 1900 for water, north of what was then Beaver station ; this well found oil at 147 feet. South of the station another well found a little oil at 205 feet. Since that date the area has been developed into a steadily productive field, yielding oil of high grade. The outcropping rocks are of Permian age, probably near the bstse of the Permian. The strata consist of shale and sandstone, with some limestone beds, and are referred to the Albany-Wichita by Udden. (See Fig. 141.) Below the Permian beds are Pennsylvanian shale, clay, and sandstone, with thin beds of limestone.

Oil and gas are found in the Permian (Wichita formation, as stated by Udden), in the Pennsylvanian, and possibly in the Mississippian. The structure of the district is that of a broad anticline with a wide, and at places nearly flat crest.

Burkburnett, which lies northeast of Electra, is one of the most productive fields in the Mid-Continent region. It is said to lie on a broad anticline, which at some places is probably complicated by faulting. It produces oil of good grade, rich in gasoline. A small part of the oil comes from beds that have been correlated with the Permian. The remainder is derived from deeper beds. In 1916 and later many wells yielding from 1,000 to 2,000 barrels a day in flush production were encountered between 1,700 and 2,000 feet. The details of the structural features of this district are not available to me. The broader features of theupUft are treated by Lee Hager. The Petrolia field (Fig. 142) is in the northern part of Clay County, 12 miles north pf Henrietta. The outcropping rocks are Red Beds of the Wichita formation and consist of shales and sandstones. These beds overlie the Cisco shale, of the Pennsylvanian, which consists of sandstones, clays, and shales and contains the oil and gds sands. As shown by Udden and Phillips, the structure

*Udden, J. A. : A Reconnaissance Report on the Geology of the Oil and Gas Fields of Wichita ai;id Clay Counties, Texas. Texas Univ. Bull, 246, 1912.

*Hager, Lee: Red River Uplift Has Another Angle. OU and Gas Jour., vol. 18, pp. 64-65, 1919.

Shaw, E. W. : Gas in the Area North arid West of Fort Worth. U. S. Geol. Survey BulL 629, pp. 1-75, 1916.

*Udden, J. A., and Phillips, D. McN. : A Reconnaissance Report on the Geology of the Oil and Gas Fields of Wichita and Clay Counties, Texas. Texas Univ. BuU. 246, 1912.

Mid-Continent Fields

s 1. CIttwi MbjMtcClaetr*

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Geology Of Petroleum

is anticlinal. There are three principal sands yielding gas or oil and gas. The average original pressure was 725 pounds to the square inch. Although the field has produced principally gas it has yielded also over 3,000,000 barrels of oil. The oil is light and of good grade. .

Fig. 142. — Structure contour map of Petrolia oil and gas field, Texas. {After

Shaw.)

North Central Texas Fields

The oil fields that lie entirely or partly in Texas (Fig. 143) are grouped as follows:

Red River region of northern Texas and southern Oklahoma.

2. North-central Texas fields, including Strawn, Allen, Duke, Caddo, Veale, Ranger, Breckenridge, Moran, Santa Anna, Brownwood, Trickham, Lohn, and others.

3. Fields in the Upper Cretaceous area east of the alcones fault.

4. Western part of Sabine uplift in Texas and Louisiana.

5. Gulf coast fields.

Mid'Continent Fields

The north-central Texas fields as developed in 1919 were practically coextensive with the belt of Pennsylvanian strata that extends northward from the Llano-Burnet uplift nearly to the Oklahoma Une. (See Fig. 144.) In nearly all the oil districts the outcropping rocks are Pennsylvanian. These generally dip northwest at low angles. Toward the east the Pennsylvanian is overlapped by the Trinity sand (Lower Cretaceous). Toward the west it is overlain by Permian strata. Below the Pennsylvanian is found the Bend series, which crops out in the Llano uplift but which is buried to the north. This series is unconformable with

SO too

5cale

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/. Humble

S.5atson SSpindlefvp 7. (hose Creek 0. tlarkham

10. Mora n

11. Sfrawn t2.GectrcfcmdBvrkk li.Pftrali'a f4.Cors/corro I&. Mexio Gets Fielct lb. of Caddo Field

n Orange l8Holiaay n.WilbargforCo. ZO.San Antonio ZlJrfckhanj n.Sartfa Anna tXffiir Gas Field illo U.Jonningi 0as Fiekf

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ZlBreckenridgo IS. Caddo P.O. 29Hondo 30.WIfrinmfOas Field 31. South Bosque 32J*yah

FiQ. 143. — Sketch map of Texas and Louisiana, showing location of certain oil and gas fields. {After Gardner.) For more detailed maps see Figs. 137., 150, 152, 155, 156 and 160.

the overlying Pennsylvanian, as is indicated by the section in Fig. 145. The general character of the Carboniferous formations is shown

'Hill, R. T. : Geography and Geology of Black and Grand PrairieSy Texas. U. S. GeoL Survey Twenty-first Ann, Bept., part 7, pp. 1-666, 1900.

Wegbmann, G. H. : a Reconnaissance in Palo Pinto Gounty, Texas. U. S. Geol. Survey BvU. 621, pp. 61-59, 1912.

Matteson, W. G. : a Review of the Development in the New Gentral Texas Oil Fields During 1918. Earn. Geology, vol. 14, pp. 95-146, 1919.

Hageb, Dorset: Geology of the Oil Fields of North-Central Texas. Am. Inst. Min. £ng. BvU, 133, pp. 1109-1118, 1918.

Geology Of Petroleum

in the sections on page 335. SandBtones are more abundant in the lower part of the series and toward the east. In the Canyon formation hmestonee increase toward the south. In the Cisco also limestones increase toward the west and south. In Pennsylvanian time the Arbuckle Mountains and some area toward the east and

Fig. 144.— map of Texaa. (After HiU, WUlia, Paige and others.

south, now buried, appear to have been the main sources of sediments of north-central Texas, rather than the Llano area. The region of what is now the Ouachita orographic element was doubtless a land area of large size, as it appears to have suppUed material

Mid-Continent Fields 331

for sedimeDts far to the north, toward the Ozarks, and far to the south, toward the Llano Mountains. Its influence on eedimentation was more far-reaching than that of the Ozark uplift or the Llano uplift. Its influence on structure, on the other hand, was more narrowly confined than that of either the Ozark or the Llano center. Mississippian and Pennsylvanian beds dip north from the Llano element to the northern parts of Young and Jack Counties.

The dominant structural feature in the northern Texas field is a monochne dipping northward from the Llano uplift at about 25 feet to the mile. On this monocline is superimposed a low arch that extends from the Llano-Burnet region northward about 150 mOes. This arch is more accentuated in the Bend series than in the overlying rocks, and has been designated the Bend arch. Its origin is uncertain. It is on the monocline that was formed by

Fia. 146. — Section of Bend arch, north-central Texas. {After Hager.)

the upthnist of the Llano element, and it extends northward from that element, but it is no more accentuated at the south end than it is 150 miles farther north. One hypothesis, based on data that are not as complete as might be wished, accounts for its origin, by assuming two periods of warping.

The vertical scale in Fig. 145 is exaggerated about 25 times. The dip of the Pennsylvanian strata is much lower than is indicated. Before the deposition of the Pennsylvanian the Bend formation was probably almost flat-lying or dipped gently northwest. After Cretaceous time the Bend was tilted eastward, as were also the Cretaceous beds.

The Bend arch (Figs. 146-149) has been the subject of much discussion. Maps of the structure are presented as expressed by

Geology Of Petroleum

S"W"™""* IMfnBwlBi. CntT*Bh

Fio. 148. — Geologic map of north-central Texas. {A/ler Hnger.) For along A-A, B-B and C-Csee Figs. 147-149.

MiD-coNTrnmr fields

FiQ. 147. — Section aezoaa Boutbernpart of Bend Arch, Texas, aloDg line A-A,

in

Fia. 149.— Section along axis of Bend Arch, Texas, along line C-C, F, 146.

Geology Of Petroleum

Hager and others. Pratt denies the existence of data showing the presence of the Bend arch farther north than Etland County.

l—H

Palo Pinto

Comanche

Fig. 150. — Sketch map of Eastland, Stephens and parts of adjoining counties, Texas, showing axes of oil and gas pools as interpreted by Matteson. Dashed outlines are not structural lines but indicate main oil-bearing areas as developed in spring of 1819. {After Matteson.)

Pbatt, W. E. : Geologic Structures and Producing Areas in North Texas Petroleum Fields, with Discussion by Hill, Schuchert, Fuller, Cubcmings, Beal, Pbpperberg, and others. Am. Assoc. Pet. Geol. Bull, 3, pp. 45-70,

Mid-Continent Fields

Jf—t 1U (H.Mi

i.Q; 151.— Logs of certwn welLi in north-central Teitaa fields. The termfl Marble Falls," "Black Lime," and "Bend Lime," are uaed synonymously Wfer UaUutm) "Present Production" means Spring, 1919.

336 Geology Of Petroleum

Briefly, the Ranger region is a broad monocline dipping northwestward, on which is superimposed the Bend arch, with its axis gently plunging north. At numerous places small wrinkles are found on the arch. Oil is concentrated below these wrinkles, especially below small open anticlines. Few of the anticlines close at the surface, but the folds become more acute below the surface, so that certain folds which do not close at the surface close in depth. Moreover, owing to the unconformities present, some folds found in depth may not be expressed at the surface, although those found at the surface are generally expressed in depth.

According to Matteson, the Bend arch is not marked by a single axis but consists of several closely spaced parallel folds. He states that in Stephens and Eastland Counties there are three axes (Fig. 150). On the east axis are the Strawn, Allen, and Duke pools. West of this and parallel to it is a second axis on which are the Caddo, Veale, and Ranger pools. Still farther west is a third axis on which are the well of Black Brothers, in the northern part of Stephens County, and the pool south of Breckinridge. Rfecords of the Black well and other wells in this area are shown in Fig. 151.

There is Uttle surficial evidence that petroleum exists in the strata underlying the area containing the Ranger and associated districts. Asphalt and oil seeps are rare or lacking. About 100 miles to the south, in the Llano-Burnet region, according to Paige, the Carboniferous strata have a strong petroliferous odor. A small oil seep in a spring near the town of Burnet has deposited at the surface asphaltic material in the cracks and interstices of the neighboring limestones. In Post Mountain also, just west of Burnet, a little oily residue is found about 20 feet above the base of the Cretaceous, and it is possible that oil has passed from the underlying Carboniferous into the porous Trinity sand and spread laterally. ,

Oil is obtained at eight horizons in north-central Texas. Of these, according to Matteson, one is at the base of the Canyon or top of the Strawn; another is in the middle of the Strawn; another comprises sand lenses in the Smith wick shale; another is at the contact between the Smith wick and the Marble Falls Umestone; and below that are four sands included in the Marble Falls. These

Paige, Sidney: Mineral Resources of the Llano-Burnet Region, Texas. U. S. Geol. Survey Bull. 450, p. 93, 1911. *Econ, Geology, vol. 14, pp. 132-134, 1919.

Mid-Continent Fields 337

sands are probably lenticular, and different sands are productive in different wells. Slight structural irregularities on the surface, such as noses, terraces, and minOT wrinkles, generally indicate more accentuated features at greater depths, and drilling them has frequently revealed oil. At some places drilling has revealed structural features that have no surface indications. Most of the wells yield gas, and in many of them the oil issues under high pressure. Salt water has been encountered in several wells. The initial production of many wells is large, and the oil is of exceptionally high grade.

Owing partly to the escape of gas in wells, the pressme has decUned in this region. The absence of sufficient gas to force the oil into the borings has resulted in an exceptionally rapid decline in the 3deld of oil wells in some of the fields that were originally highly productive.

The oil at Ranger and in other central Texas fields is a highgrade, light gravity (34M0** B.) crude oil of an oUve-green color. An analysis shows the following percentage of ingredients for Ranger crude:

Gravity 38.6** Baurn at F.

Gasoline 22.0 per cent, 69.9® gravity

Naphthas 3.8 per cent, 62. gravity

Kerosene 21 . 8 per cent, 43 . 9® gravity

Residue (lubricating and fuel oil not separated) 62.0 per cent, 27.9® gravity .

Fields East Of Balcones Fault

General Features. — The Balcones fault zone (Fig. 152) extends from Hunt County, northeastern Texas, southwestward to Bexar County, a distance of nearly 300 miles. The rocks involved are strata of the Lower and Upper Cretaceous series, of which a section is given on page 340. Oil or gas or both are found In the Navarro formation, Taylor marl, and Woodbine sand. In the Caddo field, Louisiana, the west edge of which extends into Marion County, Texas, much oil is obtained from the Woodbine sand. In some places in the Balcones region the Woodbine carries water that is only slightly saline but no oil.

Mattebon, W. G.: Op. cU,, p. 131.

338 Geology Of Petroleum

The fault zone, as stated by Hill, ' consiets of a number of nearly parallel step faults or small jc, the aggregate displacement of

Fig. 152. — Sketch map showing part of Balconea fault region, Texas. {Data from Hill, Mataon, HopHna and othera.)

'Hill, R. T.: Geography and Geolc of the Black and Grand Prairies, Texas. IT. S. Geol. Survey Ann. Kept., part 7, p. 382, 1001.

Mid-Continent Fields 339

which attains a maximum of 1,000 feet. This zone is limited nearly everywhere on the west by a larger fault, which at Austin has a downthrow of nearly 500 feet. This zone is a number of short faults overlapping en Echelon. The fault Une from the Nueces River to the Brazos River marks the dividing Une between the Black and Grand prairies. North of Waco it passes into the unconsolidated clays of the Black Prairie between Whitney and Aquilla.

The fault generally dips southeast, and the downthrow is on the southeast side. In the zone of deformation east of the fault there are small folds in which oil or gas or both are concentrated. In this zone is the Corsicana field, which embraces the Burke, Eden, Powell, and Chatfield pools and other small pools near by. South of the Corsicana field, in Limestone County, is the Mexia-Groesbeck gas field, west of which, in McLennan County, is the South Bosque field, and south of that the Thrall and Elgin fields. About 100 miles southwest of Elgin is a small field near San Antonio, where gas and heavy oil are found in the Nacatoch sand and the Annona chalk.

Corsicana Field. — The Corsicana oil and gas field, in Navarro County, extends from Corsicana eastward to Powell and from the vicinity of Angus northward to Chatfield. Productive pools having an aggregate area of nearly 50 square miles have been developed in a field that measures 20 miles from north to south and 10 miles from east to west. Oil was first discovered in the city of Corpicana, in a search for water supply. The field was gradually extended eastward and has been productive since 1895.

A section showing the strata in this field is given below.

*Matson, G. C, and Hopkins, O. B. : The Corsicana Oil and Gas Field, Texas. U. S. Geol. Survey BuU. 661, pp. 211-272, 1918.

Miller, T. D. : The Recently Developed Oil Field of Texas. Eng! and Min. Jour,, June 18, 1898, pp. 734-735.

Oliphant, F. H. : U. S. Geol. Survey Nineteenth Ann. Rept, part 6, continued, pp. 102-105, 1898.

Phillips, W. B.: Texas Petroleum. Texas Univ. Min. Survey BuU, 1, pp. 6, 36-42, 1900.

AdamSi G. I.: Oil and Gas Fields of the Upper Cretaceous and Tertiary Formations of the Western Gulf Coast. U. S. Geol. Survey BuU, 184, pp. 54-65, 1901.

Harris, G. D. : Oil and Gas in Louisiana. U. S. Geol. Survey BuU. 429, pp. 31, 34, 1910.

Geology Of Petroleum

Genbsauzed Section of Formations in trb Corsicana On. and Gas

FiEiiD, Texas' (After Matson and Hopkins)

System

Series

Group

Formation

Thickness (Feet)

Character

Quaternary.

Recent.

Alluvial depodta along streams.

Pleistocene.

Terrace depoeita.

Tertiary.

Eocene.

Midway formation.

Micaceous sandy dajra, fine argillaceous sands, and limestone concretions.

Gulf (Upper Cretaceous).

Navarro formation.

1 ,800-2 .000

Light to dark gray calcareous clay, sandy clay, and fine lenticular beds of sand.

Taylor marl.

Massive calcareous clay marl, little sand, and glauconite.

Austin chalk.

Gray to white chalky limestone containing some hard beds.

Eagle Ford shale.

Light to dark colored shale or clay and thinly laminated impure limestone.

Woodbine sand.

Sand, sandy lignitic day, sandstone, xemiginous sand, and clay.

Comanche (Lower Cretaceous).

Washita.

Denison formation.

Clay and limestone.

Cretaceous.

Fort Worth limestone.

Alternating beds of limestone and marl.

Preston formation.

Calcareous laminated clays and impure limestone.

Fredftricksburg.

Edwards limestone.

White chalky limestones, variously indurated, and in places find arenaceous beds.

Comanche Peak limestone.

Walnut clay.

Calcareous clara and impure marly and chalky limestones.

Trinity.

Paluzy sand.

Fine-grained sand and lenticular beds of clay.

Glen Rose limestone.

Impure limestone, marl, and calcareous shales.

Travis Peak sand.

Conglomerates sand sandstone, shales, and impure limestones.

"The formations below the Navarro formation crop out west of the Corsicana field and dip under it. The Upper Cretaceous formations have been penetrated by the drill in this field and are known from well records; the Lower Cretaceous formations have not been penetrated by the drill in this field but are known from outcrops and well records west of the field. The data relating to the Lower Cretaceous are taken largely from a report by R. T. Hill (Geography and Geology of the Black and Giand Prairies, Texas. U. S. Geol. Survey TwentiffirU Ann. Repi., part 7, 1901).

Mid'Continent Fields 341

The oil and gas in the Corsicana field are obtained from the upper part of the Upper Cretaceous, the light oil and the gas in the Corsicana oil pool and in the Chatfield and Edens gas pools near by, probably coming from the Taylor marl and the heavy oil and the gas in the other pools from the Navarro formation. The relation of the oil and gas to the geologic structure varies from place to place; as stated by Matson and Hopkins accimiulation is concentrated where there are well-developed anticlines, such as occur in some parts of the field that yield heavy oil. The distribution of oil and gas is also influenced by variations in the porosity of the sand, though these variations are not as numerous as in some other regions.

The strata in the Corsicana field dip in general to the southeast at a rate of 50 to 100 feet to the mile. The uniformity in direction and amount of dip is interrupted at a number of places by folds, none of which are continuous over large areas. The greatest dips observed on the folds are at the rate of 560 feet to the mile. The high dips are confined to small areas. The folds trend in two directions — one approximately parallel to the dip of the rocks and the other at right angles to it. There is no evidence of faulting.

The structure of the pool south of Chatfield shows an irregular anticline that trends northeast and is 2 miles long and about threequarters of a mile wide. The dips on its flanks are as much as 2. The accumulation of gas is in the crest of the anticline and is backed up on all sides by salt water.

The Witherspoon-McKie pool, southwest of Powell, Ues along the crest of a low, flat-topped anticUne that extends from the southeastern part of the Witherspoon tract southwestward IJ miles to the McKie tract. The depth to the highest productive sand is 825 to 875 feet, and to the lowest (1918) about 100 feet more. Oil and gas were present only along the crest of the anticline, and water was troublesome over practically the entire pool. Gas was present originally in both the upper and lower sands, but more abundantly in the lower. All the wells at the north end of the pool have been invaded by salt water and abandoned.

The Burke pool, 1 mile south of Powell, is associated with the most pronounced fold that has been found in the Corsicana field. This fold, which is probably a shortened anticline or dome, has dips of about 185 feet to the mile to the northwest, southwest, and southeast. Oil occurs in the upper part of the fold, where the

342 Geology Of Petroleum

upper sand is from about 400 to 480 feet below sea level. Where the sand is more than 480 feet below sea level it is generally saturated with brine, although in that area a niunber of wells have yielded some oil.

Mezia-Groesbeck Field. — The Mexia-Groesbeck gas field is in the east-central part of Limestone County, Texas, where it occupies an area having an approximate length of 123 miles and an approximate width of 0.9 mile.

Production began in 1912. Prior to the drilling of the first wells gas had been known in a few shallow water wells west of the field and had been exploited in the vicinity of Corsicana. Wells showing considerable volumes of gas had also been drilled between Corsicana and Mexia, but salt water interfered with development.

The wells in the Mexia-Groesbeck gas field pass through the lower Eocene Midway formation and penetrate a portion of the Upper Cretaceous Navarro formation. The Midway consists of clay, limestone, and sand. Layers of the Umestone are exposed on eroded surfaces, and where the surface is level the successive layers form bands that are roughly parallel.

The upper part of the Navarro formation, which underlies the Midway, is composed of clays and shales with thin beds of sand and sandstone.

The gas sand of the Mexia-Groesbeck field is the Nacatoch sand member of the Navarro formation, correlated with the Nacatoch sand of northwestern Louisiana and southwestern Arkansas. The Nacatoch sand in the Mexia-Groesbeck field, as shown by C. E. Van Orstrand, contains from 16.6 to 34.2 per cent of pore space, with an average of 25.5 per cent, which would amoimt to 2,331,057,000 cubic feet for the entire field. Only a small part of that amount belongs to the imdeveloped area, the largest part of it being in the developed areas. The entire pore space of the gas sand was probably occupied by gas, because the pressure when the field was first developed, 276 pounds to the square inch, was suflBicient to force the gas into minute pores. The generally uniform decline of pressure throughout the field, as stated by Matson, indicates a uniformly porous rock.

Matson, G. C. : Gas Prospects South and Southeast of Dallas. U. Sr Geol. Survey BvU. 629, p. 87, 1916. *Matson, G. C. : Op. cU., p 92.

Mw-Continent Fields 343

Thrall Field. — The Thrall oil field is about a mile southeast of Thrall, Williamson Coimty, Texas. Oil was discovered here in 1914 in a well sunk for water, and the district soon developed into a productive field. The outcropping rock is the Taylor marl of the Upper Cretaceous series, which dips east to southeast at 60 to 100 feet to the mile. The strata above the oil-bearing rock consist

Fig, 153. — Sketch showing the diatributton and production of wells, in the Thrall oil field, Texas. Cootour lines show position of upper surface of oilbearing rock in feet below sea level. (After Udden and Bybee. )

of shale and clay, with gypsum, calcite, glauconite, and marcasite. The oil-bearing formation is a porous, soft green rock found in the

'Uddbn, J. A., and , H. P. : The Thrall Oil Field. Texas Univ. Butt. 66, 1916.

344 Oeology Of Petroleum

Taylor marl at a depth of about 850 feet. It is brecciated and highly altered. Larsen, who examined specimens microscopicatly, states that some specimens appear to be a fine-grained tuff.

The top of the petroliferous body is arched to form a dome, and the oil accumulation is related to the dome.

The oil is of low specific gravity and has a paraffin base. It is heavier but in many respects resembles the oil of the Corsicana field which comes from a sand in the Taylor marl.

Many of the wells in this field (Fig. 153) produced some gas, and the gushing of the wells is ascribed to gas pressure. The oil deposits paraffin rapidly in pipes and casing, so that wells become plugged with it and cease to yield until treated.

Initial Production of Sssvbnty Wells in

The

Thrall Oil Field

Production (Barrela per Day)

Number of Wells

6,000 to 1,001

1,000 to 201

200 to 41

40 to 9

8 to 1

References for Texas Fields

Adams, G. I.: Oil and Gas Fields of Western Interior of Northern Tezaa Coal Measures, and of the Upper Cretaceous and Tertiary of the Western Gulf Coast. IT. S. Geol. Survey BuU. 184, pp. 1-64, 1901.

Beede, J. W. : Notes on the Structure and Oil Showings in the Red Beds of Coke County, Texas. Am. Assoc. Pet. Geol. BvU., vol. 3,.pp. 117-123, 1919.

Beede, J. W., and Waite, V. V. : The Geology of Runnels County, Texas. Univ. BuU. 1816, 1918.

Deubsen, Alexander: Geology and Underground Waters of the Southeastern Part of the Texas Coastal Plain. U. S. Geol. Survey Water-supply Paper 335, pp. 1-365, 1914.

DuMBLE, E. T. : The Occurrence of Petroleum in Eastern Mexico as Contrasted with Those in Texas and Louisiana. Am. Inst. Min. Eng. Bull., August, 1915, pp. 1623-38.

EcKES, C. R. : Description of CuUings from the Duffer WeUs, Ranger Field. Am. Assoc. Pet. Geol. BuU., vol. 3, pp. 39-43, 1919.

Udden, J. A., and Bybee, H. P. : Op. eit., p. 39.

Midontinent Fields S45

Fbnneman, N. M. : Oil Fields of the Texas-Louisiana Gulf Coastal Plain. U. a Geol. Survey BvU. 282, pp. 1-146, 1906.

Fobs, Julius: Geology of Texas Oil Fields. Oil and Gas Jour, SuppL., May, 1919, pp. 109-119.

GiBTT, G. H. : The Bend Formation and Its Correlation. Am. Assoc. Pet. GeoL BvU , vol. 3, pp. 71-81, 1919.

GoBDON, C. H. : Geology and Underground Waters of the Wichita Region, Texas. U. a GeoL Survey WaterSupply Paper 317, pp. 1-88, 1913.

Geology and Underground Waters of Northeastern Texas.

U. a GeoL Survey Water-Supply Paper 276, pp. 1-78, 1911.

Gould, C. N.: Geology and Water Resources of the Eastern Portion of the Panhandle of Texas. U. S. Geol. Survey WaterSupply Paper 154, pp. 1-64,

Habrib, G. D.: Oil and Gas in Louisiana, with a Brief Summary of Their Occurrence in Adjacent States. U. S. GeoL Survey BulL 429, pp. 1-192, 1910.

Hayes, C. W., and Kennedy, William: Oil Fields of the Texas-Louisiana Gulf Coastal Plain. U. S. GeoL Survey BuU. 212, pp. 1-174, 1903.

Hill, R. T.: Geology of Black and Grand Prairies, Texas. U. S. Geol. Survey TtoerUy-first Ann, RepL, part 7, pp. 1-666, 1900.

Hill, R. T , and Vaugban, T. W : U. S. Geol. Survey Geol, AUaa, Austin folio (No. 76), 1902.

Hopkins, O. B. : The Brennan Salt Dome, Washington and Austin Counties, Texas. U. S. Geol. BuU. 661, pp. 271-280, 1918.

The Palestine Salt Dome, Anderson County, Texas. U, S.

GeoL Survey Butt. 661, pp. 253-270, 1918.

Matson, G. C, and Hopkins, O. B. : The Corsicana Oil and Gas Field, Texas. U. S. GeoL Survey BvU. 661, pp. 211-252, 1918.

Matteson, W. G. : a Review of the Development of the New Central Texas Oil Fields During 1918. Ecm, Geology, vol. 14, pp. 95-146, 1919.

MooBE, R. C. : The Bend Series of Central Texas. Am. Assoc. Pet. GeoL BvU,, vol. 3, pp. 216-241, 1919.

Plummeb, F. B. : Preliminary Paper on the Stratigraphy of North-Central Texas. Am. Assoc. Pet GeoL BvU., vol. 3, pp. 132-150, 1919.

Paige, Sidney: Mineral Resources of the Llano-Burnet Region, Texas. U. S. GeoL Survey BvU. 450, pp. 1-103, 1911; Ged, AUaa, folio 183, 1912.

Pbillipb, W. B. : Oil Prospects in Texas. Oil and Gas Jour., vol. 13, p. 25, AprQ 15, 1915.

Pbatt, W. E.: Geologic Structure and Producing Areas in North Texas Petroleum Fields. Am. Assoc. Pet. GeoL BvU., vol. 3, pp. 44-70, 1919.

Sellabds, E, H. : Structural Conditions in the Oil Fields of Bexar County, Texas. Am. Assoc. Pet. GeoL BvU,, vol. 3, pp. 299-309, 1919.

Sbaw, E. W., Matson, G. C, and Wegemann, C. H.: Natural Gas Resources of Parts of Northern Texas. U. S. GeoL Survey BvU. 629, pp. 1-126,

Udden, J. A.: Oil-Bearing Formations in Texas. Am. Assoc. Pet. GeoL BvU., vol. 3, pp. 82-98, 1919.

Oil in an Igneous Rock. Econ. Geology, vol. 10, pp. 582-585,

346 Geology Of Petroleum

T Jdden, J. A. : Thrall Oil in Serpentine. Oil and Gas J&ur., vol 13, p. 27, April 22, 1915.

Subsurface Geology of the Oil Districts of North-Central Texas.

Am. Assoc. Pet. GeoL BvU., vol. 3, pp. 34-38, 1919.

and Philupb, D. McN. : Geology of the Qfl and Gas Fields of

Wichita and Clay Counties, Txas. Texas Univ. BidL 246, p. 16, 1912.

Bakeb, C. L., and Boss, Eiol: Review of the Geology of

Texas. Texas Univ; BvU. 44, with large map of Texas, 1916

Vaughan, T. W. : U. S. GeoL Survey Geol. AOas, Uvalde folio (No. 64), 1900. Wegemann, C. H.: A Reconnaissance for Oil Near Quanah, Hardenoan County, Texas. U. 8, GeoL Survey BvU. 621, pp. 109-115, 1915.

A Reconnaissance in Palo Pinto County, Texas, with Special

Reference to Oil and Gas. U. S. Ged. Survey BuU. 621, pp. 519, 1915.

Northwestern Louisiana And Northeastern Texas

General Features. — Northwestern Louisiana and northeastern Texas are covered with Tertiary and Quaternary deposits, which extend northward on both sides of the Mississippi River to Cairo, IlUnois. The country is fiat, and rock exposures are rare over considerable parts of the area. The rocks at the surface generally dip at low angles away from the older rocks that occur farther north. There is a gentle dip toward the Mississippi River, which is probably parallel to and not far from the axis of a gentle syncline or broad fluting on the monocline that dips south at a low angle. Superimposed on the monocline of the Mississippi embayinent (Fig. 154) are long and relatively narrow zones of deformation marked by faulting or by folding. These zones probably extend for hundreds of miles, although they are not continuously exposed.

One of these zones of deformation is the Red River fault zone

(Fig. 155). This zone, as stated by Hill, consists principally of

two nearly parallel major fault lines extending S. 60 E., or in a

direction perpendicular to that of the Balcones fault zone. Their

downthrows are in opposite directions, and between them is a strip

or block of uplifted strata, as seen between Red River north of

Denison and Cook Spring, to the south. The northern of these

faults follows Red River from Marshalls BlufiF, near Preston (old),

to the northeast corner of Grayson County. Its downthrow is

north, and it is occupied by Red River north of Denison. On the

north side of Red River the beds from the Woodbine formation

downward, are lowered. They face the Antlers sand and Groodland

HiLL, R. T. : Geography and Geology of Black and Grand Praunes, Texas. U. S. GeoL Survey Twenty-first Ann. Rept., part 7, p. 384, 1901.

Mid-Continent Fields 347

limestone on the south. The downthrow at Preston is about 626 feet, and north of Denison it is 617 feet.

Nearly parallel to this t&alt and from 5 to 7 miles south of it is the Cook Spring fault. (See Fig. 155.) This fault line paesea from the north edge of Grayson County south of east near Potta-

boro and through Cook Spring. Its downthrow consists of several steps to the south and amounts to about 200 feet near Fottsboro. At IJ miles northeast of Pottsboro the Dexter sands abruptly

34d GEOLOGY OF PETROLEUM

iermiiiate and the Eagle Ford clays are faulted down opposite the Fort Worth limestone and the basal Denison beds. In the northern part of Grayson County the rocks are folded along an antieline having a generaUy similar strike. Possibly anticlines in Cotton and Jefferson Counties, Oklahoma, and the Devol anticline in the Grandfield area may belong to the same zone of deformation.

In northwestern Louisiana the Red River zone of deformation is probably represented by a sharp flexure that dips north, away from the Sabine uplift. As mapped by Veatch this zone extends to the Mississippi River.

The Angelina flexure extends from Angelina County, Texas, northeastward into Louisiana and possibly to the Mississippi River. Along the flexure the rocks dip to the southeast at a high angle. Between the Red River zone of deformation and the Angelina flexure lies a great, broad dome — the Sabine uplift. From tUs dome the rocks dip northeast along the Red River zone of deformation, east to the Mississippi River, southeast along the Angelina flexure, and west in eastern Texas.

In this ron deformation has taken place in late time. According to Veatch, shoals on the Sabine River and a ridge across Angelina River are due to this flexure.' In the WUcoz formation of the Eocene, the rocks locally dip 10 or more.

Contour maps of the structure of the Sabine uplift, based on weU logs, show that the dome has an undulating crest. Three anticlinal axes are noteworthy. These are approximately parallel and strike northeast. On the north one are the oil fields of Caddo Lake. The central axis lies near Shreveport and extends northeastward, passing through the Homer field. South of this is a third axis which is developed in the De Soto-Red River field. It practically coincides with the Gusher Bend fault of that field. High points along the crests of these folds are essentially in line,

Stephenson, L. W. : A Contribution to the Geology of Northeastern Texas and Southern Oklahoma. U. S. Geol. Survey Prof. Paper 120, pp. 129-163,

'MuNN, M. J.: Reconnaissance of the Grandfield District, Oklahoma. U. S. Geol. Survey BvU. 647, pp. 1-85, 1914.

WsGBiiANN, C. H. : Anticlinal Structure in Parts of Cotton and Jefferson Counties, Oklahonui. U. S. Geol. Survey BuZZ. 602, pp. 1-108, 1915.

Veatch, A. C. : Geology and Underground Water Resources of Northern Louisiana and Southern Arkansas. U. S. Geol. Survey Prof. Paper 46, p. 68,

Mid-Continent Fields

suggesting a second series of folds striking northwestward across the axes of the northeast folds*

Fig. 155. — Map showing probable structural lines in Mississippi embayment

region. {After Harris.)

Geology Of Petroleum

The fields on the Sabine uplift that yield oil or gas or both include the Caddo, Shreveport, De Soto-Red Biver (Bull Bayou), Elm Grove, Pelican, Homer, Monroe, and others. (See Fig. 156.) he Caddo field yields gas and heavy oil from the Nacatoch sand $nd also from the Annona chalk of the Austin. It yields light oil (38° B.) from the Blossom sand member of the Eagle Ford clay and from the Woodbine sand. The Shreveport gas field yields gas from the Nacatoch. The Red River-De Soto gas field yields gas from the Nacatoch and much oil from the deeper sands near the bottom of the Upper Cretaceous. The Homer field probably yields oil from the same strata or from the Blossom. The Pelican field yields gas from the Nacatoch and oil from the Blossom. About 100 miles east of Shreveport, at Monroe, Ouachita Parish,

Harrison

Union

Xlaiborne

.X A, lit

FiQ. 156. — Sketch map showing oil and gas fields in northern Loiusiana and northeastern Texas. Bethany, Shreveport, Elm Grove and Monroe are gas fields. Caddo, Homer, Bull Bayou and Pelican are oil fields.

l '

fiOuisiana, a large gas field has recently been developed on a great anticline or dome. Practically all the fields yield gasoline, recovered from gas.

The Nacatoch sand is porous over wide areas and is gas-bearing in all the large fields in northwestern Louisiana, as well as in the JSalcones fault region, Texas. Its thickness ranges from 50 to 150 feet and averages 125 feet.

The oil in the deeper sands of the northern Louisiana fields is associated with much gas. Some of the wells are large gushers. Recently wells yielding 10,000 barrels a day have been brought in

Midontinent Fields

near Homer, on the east extension of the field. Salt water is found below the oil.

A section across this region is shown in Fig. 157.

Caddo Field. — The Caddo oil and gas field is northwest of Shreveport, mainly in Caddo Parish, Louisiana, and extends a short distance westward into Texas. The producing wells occupy an area extending northwestward from Mooringsport, Louisiana, for about 12 miles, and a long, narrow belt extending nearly 10 miles northeastward from the north end of the main field. Natural gas has been known at Shreveport for more than a quarter of a century, though its exploitation was not begun until 1912, after large gasproducing areas had been developed in the northern part of Caddo Parish. The area south, near the city of Shreveport, produces gas and some oil.

The country is flat with small hills rising a few feet above the surface. These hills, according to Matson, are not structural features, but are probably the work of ants.

Habbib, G. D. : Oil and Gas in Louisiana. U. S. GeoL Survey BitU. 429, 1910.

Matson, G. C. : The Caddo Oil and Gas Field, Louisiana and Texas. U. S. GeoL Survey BuU. 619, pp. 1-62, 1916.

Vbatch, a. C.: Geology and Underground Waters of Northern Louisiana and SoutHem Arkansas. U. S. Oeol Survey Prof. Paper 46, 1906.

UKkiSburg\ tihkftivr

HtdRmr Ibmrrkanen

5a/phvrJ?fvi

1%

A-

Hoffniijfspeti

Haifsfiela Uuisicma

StMn River}

§iff1mitkjk

o o

S

H

s

o

d

Geology Of Petbolevm

h

ir

It

Mid-Continent Fields

li'

imwd jiijil

I'

jljil

A

k

ini

Geology Of Petroleum

l:

Mid-Continent Fields 355

Oas seeps have been noted in water pools and in Caddo Lake, and these led to drilling. Oil or gas or both are found in the Nacatoch sand, the Annona chalk, the Blossom sand member of the Eagle Ford clay, and the Woodbine sand. The oil is of high grade, some of it 38 B. or higher. Some of the oil issues in gushers.

In the Caddo field shallow anticlines and synclines are developed on the Sabine upUft, and smaller folds are superimposed on these. The oil and gas are concentrated in the elevated portions of the folds.

De Soto*Red River Field. — The De Soto-Red River field is about 50 miles south of the Caddo field. The rocks are of Eocene and Upper Cretaceous age. The formations present at Caddo are noted also in this field. The principal oil sand is below the Brownstown marl, at depths between 2,450 and 2,750 feet. Gas and heavy oil are found in the Nacatoch sand, and light oil in the Blossom sand member of the Eagle Ford clay, which lies about 1,600 feet below the Nacatoch. It is not certain whether this is the Blossom or the Woodbine sand. It has been suggested that h may be older than the Woodbine.

A fault with a throw of 200 to 225 feet strikes northeast near the largest anticline. This is known as the Gusher Bend fault, from its occurrence near a bend in Red River where on a small dome numerous wells with large flow were drilled.

Pelican Field. — The Pelican field is about 50 miles south of Shreveport, in the northern part of Sabine Parish, Louisiana. The section is similar to that of the De Soto-Red River field, and the structure is domatic.

The Nacatoch sand is reached at a depth below sea level ranging from 900 feet in the northern part of the field to about 1,350 feet in the southern part. In this area it consists largely of hard sandy shale and sandstone with only a relatively small amount of loose sand. It has yielded gas and heavy oil.

The principal productive oil sand in this field is the Blossom sand, which occurs at a depth ranging from 2,800 feet in the northern part of the field to 3,200 feet in the southern part.

Matson, G. C, and Hopkins, O. B.: The De Soto-Red River Oil and Gas Field, Louisiana. U. S. GeoL. Survey BuU, 661, pp. 101-140, 1918.

Geology Of Petroleum

FoBMATioNS OP GuLF Series (Uppeb Cretaceoub) IN Db Soio-Rkd Riter

Oil and Gab Field, Louisiana

(After Matson and Hopkins)

Charaeter

Range in Depth

Aricadelphia clay.

Stiff, gummy clay, with some sandy layers in lower part.

Nacotch sand.

Sand, with some layers of clay and hard sandstone.

Prominent gas sand.

Top at 725-975 feet.

Marlbrook marL

Shale or marl above; white chalk below.

Some oily supposedly derived from lower formations through faults.

Top at 850-1 ,060 feet.

Annona chalk.

Chalk.

Brownstown marl .

Probably marl and chalk above; shale and sandy shale, with some sand, below.

Showings of oil and gas below base of chalk.

Eagle Ford shale.

Shales, sands, and probably limestone beds.

Principal oil sand of field; also deep gas sand.'

Oa sand at 2,450- 2 .550 feet; deep gas sand at 2,650-2,750feet.

Woodbine sand.

Not definitely recogstone beds.

'Exact correlation uncertain; may be older than indicated.

Stephensville, Arkansas. — A fifty-barrel well was brought in near Stephensville, Ouachita County, Arkansas, in 1920. The oil is in a sand of the Upper Cretaceous, probably the Woodbine or the Blossom sand.

Mid-Continent Fields 357

References for Louisiana Fields

Bates, Mowry : A Concrete Example of the Use of Well Logs. Am. Inst. Min. Eng. Bull. 137, 1918.

Berrt, E.. W. : The Lower Eocene Floras of Southeastern North America. U. S. Geol. Survey Prof. Paper 91, pp. 1-481, 1916.

DuMBLE, E. T. : The Age and Manner of Formation of Petroleum Deposits. Am. Inst. Min. Eng. Trans., vol. 48, pp. 54-532, 1915; Am. Inst. Min. Eng. BvU., 1915, pp. 1623-1638.

Gardner, J. H. : The Mid-Continent Oil Fields. Geol. Soc. America Bull., vol 28, pp. 709-714, 1917.

Harris, G. D.: Oil and Gas in Louisiana. U. S. Geol. Survey BvU. 429, pp. 1-192, 1910.

Harris, G. D., Perrine, I., and Hopper, W. E. : Oil and Gas in Northwestern Louisiana, with Special Reference to the Caddo Field. Louisiana Geol. Survey BuU. 8, pp. 1-48, 1909.

Lucas, A. F. : The Possible Existence of Deepeated Oil Deposits on the Gulf Coast. Am. Inst. Min. Eng. Bull. 139, 1918.

Matson, G. C. : The Caddo Oil and Gas Field, Louisiana and Texas. U. S. Geol. Survey BvU, 619, pp. 1-62, 1916.

Matson, G. C, and Hopkins, O. B. : The De Soto-Red River Oil and Gas Field, Louisiana. IT. S. Geol. Survey Bull 661, pp. 101-140, 1918.

SoMERS, R. E.: Louisiana Oil and Gas Fields. OH and Gas Jour. Supjd., May, 1919, pp. 125-129.

Vauohan, T. W. : a Brief Contribution to the Geology and Paleontology of Northwestern Louisiana. U. S. Geol. Survey Bull. 142, pp. 1-65, 1896.

Veatch, a. C. : Geology and Underground Water Resources of Northern Louisiana and Southern Arkansas. U. >S. Geol. Survey Prof. Paper 46, pp. 1-422, 1906.

CHAPTER XVIII PROSPECTS m MISSISSIPPI, ALABAMA AND GEORGIA

Mississippi. — The Vicksburg-Jackson area of Mississippi lies east of the Louisiana fields. The area is no more diversified topographically than other areas in the Coastal Plain where the maximum reUef does not exceed 300 feet, the maximum elevation above sea level is not greater than 500 feet, and there are only slight differences in hardness of rocks. The main features are the broad, flat valleys that cross the region in general from north to south and the interstream tracts, which in the western part of the area are much dissected and have angular topographic features and in the eastern part are flat or rolling plains.

The city of Jackson is near the center of a broad, gentle fold, which shows a domeUke arch in cross-section from northwest to southeast and a terrace-Uke form from northeast to southwest. Near the southwestern and southern parts of the anticline the dips are as much as 60 to 70 feet to the mile; in the northwestern and southwestern parts they are 30 feet or less to the mile. The northern extent of this fold has not been determined. No oil seeps are reported.

The presence of a porous stratum is probable, as sands ttpproximately the equivalent of those that are productive in Louisiana, the Ripley and Tuscaloosa, are known to dip imder this region, although their depth and nature in the Mississippi field are imperfectly known.

All the rocks of the Vicksburg-Jackson region are sedimentary in origin and relatively young, the exposed rocks ranging in age from Claiborne (Eocene) to Recent, as shown in the upper part of the following table. The formations below the Claiborne are below drainage level.

Hopkins, O. B.: Structure of the Vicksburg-Jackson Area, Mississippi U. S. Geol. Survey Bull. 641, pp. 93-120, 1917.

Crider, a. F. : Geology and Mineral Resources of Mississippi. U. S. GeoL Survey BuU, 283, 1906.

Crider, A. F.: Oil and Gas Possibilities in Mississippi. Southwestern Assoc. Pet. Geol. BuU. 1, pp. 152-155, 1917.

Prospects In Miss., Ala., And Georgia 36§

Sbction of Formations in Vicksburg-Jacxson Abba

(After Hopkins)

System

Series

Group or Formation

Thickness

Cbaraoter

Recent.

Alluvium.

Feet

streams.

Plebtocene.

Loess and yellow loam.

Clay, fine gray to buff, calcareous, and yellow to brown loam.

Alluvial terrace deposits.

Sand, gravel, and clay.

Pliocene.

Sand and gravel.

Terrace sand and gravel.

Oligocene.

Catahoula sandstone.

Unconsolidated sands, sandstones, gray siliceous clay, and some lig* nitic material.

Vicksburg limestone.

Marl and clay above, containing marine shells; limestone and impure limestone and marl below.

Tertiary.

Eocene.

Jackson formation.

250-500 (?)

Sand above, cross-bedded, green to yellow nonfossiliferous; gray clay weathering black below and sand beds at base. Both clay and sand beds contain marine shells.

Claiborne group.

500-1,000

Marls, sands, lignitic days, and lignite above; quartsite, clay stone, and marl below.

Wilcox group.

850-1 ,500 (7)

Lignitic clays and eands, with sand predominating in middle part.

Upper.

Midway group .

Clay, dark gray to black, and micaceous sandstone, with hard limestone and sandy marl below.

Ripley forma-

Sands, clays, marls, and impure limestones of marine origin.

Cretaoeoua.

Sdma chalk.

600-1,000

Chalky limestone with argillaceous and sandy beds.

Eutaw formation.

Sands, massive and cross-bedded.

Tuscaloosa formation.

Irregularly bedded sands, clays, and gravels, containing clay and lignitic layers at top.

Geology Of Petroleum

Genbbausebd Gbologic Section of

Western Alabama

Thick-

Geolosic Age

Group

Formation

neB8

Feet

Pliocene-

Lafayette.

Gravel, sands, clays.

Pleistocene.

Lower Mio-

Grand Gulf.

Soft sandstones and

cene.

clays.

Lower Oligo-

St. Stephens lime-

Unusually soft lime-

cene.

stone.

stone, easily cut with saw.

Gosport greensand.

Glauconitic sands.

Lisbon.

Calcareous clays and

Claiborne.

sandy clay.

Tallahatta buhr-

Aluminous sandstones

stone.

and siliceous clays.

Hatchetigbee.

Sandy clays and crossbedded sands.

Chickasaw

Bashi.

Sands and clays. Fos-

Eocene.

(Wilcox).

silif erous greensand.

Tuscahoma.

Gray and yellow croflsbedded sands.

Nanafalia.

Siliceous clays.

Naheola.

Gray sandy clays. Glauconitic clays.

Midway.

Sucamochee clay.

Dark-brown clay.

Clayton.

Impure limestone.

Ripley.

Calcareous and siliceous sands.

Upper Cre-

Selma chalk.

Argillaceous lime-

taceous.

stones.

Eutaw sands.

Glauconitic sands, cross-bedded.

Tuscaloosa.

Irregular bedded sands, clays, and gravels.

Alabama. — Gas and some oil have been discovered in the Pennsylvanian series in northwestern Alabama (see p. 247), but the

Prospects In Miss., Ala. And Georgia 361

production has not been large. In southern Alabama, according to Hager,' there are several localities where oil may possibly be found in the Cretaceous beds.

The Hatchetigbee fold (see Fig. 158), recently described by Hop- 'Haqeb, Dobsby: Poesible Oil and Gas Fields in the Cretaceous Beds of Alabaoia. Am. Inst Mia. Eng. BvU. 134, pp. 469-17d, 1918.

362 Geology Of Petroleum

kins, also by Hager, runs in a general southeasterly direction through portions of Choctaw, Clarke and Washington Counties and is about 20 miles long and 4 to 5 miles wide. Along the axis the Hatchetigbee formation crops out. This formation is about 550 feet lower stratigraphically than the St. Stephens limestone, which crops out on all sides of the fold. The reversal is not much less than 500 feet. The pitch of the strata away from the axis of the anticline ranges from to nearly 2®.

The Jackson anticline is in all probability a part of the same fold as the Hatchetigbee anticline. Along the axis of the Jackson anticline, rocks of the Claiborne group are exposed, and the reversal is not much less than that of the Hatchetigbee anticline, from which this fold is separated by a saddle.

Toward the east, according to Hager, no marked folding is noted imtil Geneva County is reached. In an area near Geneva, covering possibly 20 square miles, the Claiborne rocks are exposed at the surface, with the St. Stephens limestone surroimding them. The reversal on this fold is probably more than 100 feet. In this area exposures are meager, owing to the covering of the Grand Gulf and Lafayette formations.

East of Geneva, near Gordon, there is another anticlinal fold, on the Georgia State line. It has a reversal of 40 feet and covers 10 square miles.

The formations that are regarded by Hager as possible sources of the oil or gas are the Ripley, the Eutaw (Tombigbee sand), and the Tuscaloosa (Woodbine sand).

A well on the Hatchetigbee anticline is reported to have had showings of gas at 750 and 1,500 feet and of oil at 2,250 feet. The 750-foot gas horizon is probably in the Ripley formation, and the 1,500-foot horizon is in the Selma chalk. The oil at 2,250 feet is below the Selma chalk and probably in the Eutaw sands.

Georgia. — A seep of petroleum was reported to be found in 1919 about 1 mild south of Scotland, Telfair County, Georgia.* The

Hopkins, O. B. : Oil and Gas Possibilities of the Hatchetigbee Anticline, Alabama. U. S. Geol. Survey BuU. 661, pp. 281-313, 1918.

Hager, Dorse y: Op dt. p. 476.

'Vbatch, Otto, and Stephenson, L. W.: Preliminary Report on the Geology of the Coastal Plain of Georgia. Georgia Geol. Survey BvXL 26, pp. 60-61, 1911.

Hull, J. P. D., and Teas, L. P.: OH Prospect Near Scotland, Telfair County, Georgia. Georgia Geol. Survey, pp. 3-5, 1919.

Prospects In Miss., Ala. And Georgia 363

fM4J9i4uej94ifiun

surface deposits throughout the interstream areas in this region consist of 100 feet or less of irregularly bedded sandy clays and sands with subordinate interbedded layers of argillaceous sandstone. They are underlain by 100 feet or i— i — fli

more of soft sandy days and sands, in part water-bearing, with interbedded thin layers of sandstone and quartzite that belong to the Alum Bluff formation. The Alum Bluff formation is underlain by 500 feet or more of limestone with interbedded layers of calcareous sandstone and marl, which probably represent in descending order the Chattahoochee and Vicksburg formations of the Oligocene and perhaps the Jackson formation of the Eocene. These formations contain waterbearing beds. Beneath the limestones are sediments of Eocene and Cretaceous age, which probably have an aggregate thickness of 1,500 feet or more and which rest upon a basement of ancient L

SIIIAU09J9J.dp

crystalline rocks.

These also contain important water-bearing beds. The dip of the beds is southeastward and increases with the age

364 Geology Of Petroleum

of the beds from 4 to 5 feet to about 30 feet to the mile. The general stratigraphic relations of the formations are shown in Rg. 159.

Examination of the widerlying rocks where they come to the surface about 75 miles north of Scotland shows them to be largely of marine origin, with remnants of plant and animal life. These rocks belong to the Cretaceous system, which is oil-bearing in Louisiana and Texas.

It is not yet determined whether there is any favorable structure in the area.

Chapter Xix

Gulf Coast Fields Of Texas And Louisiana

Eastern Texas and Louisiana are underlain by Mesozoic and Cenozoic rocks, which crop out as broad belts in which the younger rocks lie successively nearer the sea. The younger beds extend farther north in the region of the Mississippi River than east or west of it. Structurally the region has been characterized as a gently pitching trough with its axis lying along the river. The beds in general dip at very low angles, though locally they are sharply flexed.

The country is approximately flat, and details of structure are derived principally from drill holes. At many places low mounds or hills rise above the generally level plain. On some of these there are small lakes from which gas bubbles escape. Sulphur, sulphur dioxide, sulphuric acid, saUne water, gas, oU, asphalt, or "paraflSn dirt" are sought for as evidences of oil-bearing areas. These indications are foimd also at some places where there is no mound or rise of the land. Drilling has shown that cores of salt with petroliferous beds underlie many of the mounds or the other places where one or more of the indications noted above are present. The distribution of the salt domes is shown by Fig. 160. A cross-section of a dome is shown by Fig. 42, p. 136. Some of them are described below.

At Spindletop, in southern Texas, about 3 miles south of Beau-

Harris, G. D. : CHI and Gas in Louisiana, with a Brief Summary of Their Occurrence in Adjacent States. U. S. Geol. Survey BvU, 429, 1910.

Fbnneman, N. M. : on Fields of Texas and Louisiana Gulf Coastal Plain. U. S. Geol. Survey BuU. 282, 1906.

Deussen, Alexander: Geology and Underground Waters of the Southeastern Part of the Texas Coastal Plain. U. S. Geol. Survey Water-supply Paper 336, 1914.

Vbatch, a. C: Geology and Undergroimd Water Resources of Northern Louisiana and Southern Arkansas. U S. Geol. Survey Prof, Paper 46, 1906.

Hates, C. W., and Kennedy, William: OU Fields of the Texas-Louisiana Gulf Coastal Plain. U. S. Geol. Survey BuU. 212, 1903.

Kennedy, William: Coastal Salt Domes. Southwestern Assoc. Pet, Geol. BvU.f vol. 1, pp. 34-59, 1917.

Geology Of Petroleum

Ckhosoic DEPOsm of thb Tbuw Coase&i. Plair

(After Deuaaen)

Rcoeiit.

Plewtocene.

Thidc-

litholoor mad Characteristie Foaeils

Beaumont clay.

Liflsie gravel.

-Unconformity-

Pliocene.

Highest Pleistocene terrace (farther inland).

-Unconformity-

Feet

max.

Thin to 903

o-:o

Uvalde formation (late Pliocene).

Fluviatile deposha, rnniaiiting of brown, red. or blade aaody ciay or ailt of tbe lov. overflow tcrof the streams; flood-plain materiala. inciudsand and grand bars. Reeoit buffalo bones, etc. Seawaid, tbeae flumtile deposits gnMie into intcntzeam deposits ronwiating of yellow and blue dys and ydlow wave-Conned sand. sand and ehdl bearhra. baza, and ins Bangia euneata and other fossils.

Bine, caleareooB day. with numerous time concretions about 1 inch through. Lenses of sand and sandy day. The clays carry Rangia ctmeata, etc.; embedded logs are eommon.

Graves and coarse sands, with small lenses and pockets of red day in places; limy class, gravels, and limy oonglomerates or "adobe" in others. The fossils include £quu9 emip'i.-atu8, M;alorxyx, etc.

Farther inland the lissiesravd and Beaumont clay are icpiuaented alone JJie stream valleys by the lowest and the middle of the three Pleistocene terraces.

Fluviatile deposits consisting of granitic graveb in and adjacent to certain drainage areas; flints, limestone debris, and limy conglomerates in others; ferruginous sands and silts, with fragments of iron ore, in still oths. In the streaui valleys these materials appear as terraces lying 200 to 225 feet above the levd of the inesent stream channels, and grading laterally into an inteptream or upland phase veneering the uplands with a sheet of g avel where the Y;ua and Jackson formations constitute the country rock, but thinning and disappearing south of the Yegua-Catahoula ot the Jackson-Catahoula boundary. No fossils.

Fluviatile deposits, consisting of flint gravel and limestone debris embedded in a clay matrix. In the plateau region west of the Coastal Plain the the formation appears as the uppermost terrace of the major streams, lying about 350 fe t above the levels of the present stream channels. Along the Cretaceous-Tertiary boundary, the traces grade laterally into an upland grand deposit, which caps the interstream areas, but thins and disappears a distance to east and south.

GULF COAST FIELDS OF TEX. AND LOUISIANA 367 Cenozoic Dbfosits or thb Tbxab CJoastal Plain — Continued

System

Series

Formation

lithoiogy and Characteristic Fossils

Feet

-Unconformity-

1,250-

Lacustrine and littoral deposits, consisting of cro8- bedded, coarse, gray, semi-indurated, highly calcareous sandstones. Lenses of clay in places. Aeeratherium and other fossils. East of the Bra- Bos these beds are almost completely overlapped by the Lissie gravel. Seaward, the time equivalent of the Dewitt formation is represented by

Dewitt forma-

1,500

about 800 feet of marine sands and clays, carrying

Miocene.

tion."

Area carolinentia and other upper Miocene marine

fossils and believed to involve some of the lower

Pliocene. These marine deposits do not outcrop

and are not a part of the lacustrine Dewitt forma-

tion, which also includes some deposits of early

k

Pliocene age.

Palustrine deposits, conasting of gray, white, and

Fleming clay.

bluish-white, bedded, calcareous clays, with nu-

-Unconformity-

merous small concretions of lime and some lenses of sand.

Oligocene.

Littoral deposits, consisting of hard, blue, semi-

Catahoula

quartsitic, noncalcareous sandstones, with inter-

cs

aandstone.

bedded lenticular masses of green days.

Jackson forma-

Marine deposits, consisting of calcareous blue days.

tion.c

with large limestone concretions. Carry Levi- /uau9 brannen and other Eocene forms.

Yua forma-

Palustrine deposits, consisting of green clays with

tion.

concretions of selenite; in places, lenses of sand and lignite.

Palustrine and marine deposits, consisting of lentic-

ular masses of yellow sand and clay; in places,

Cook Moun-

lenses of green calcareous, glauconitic, f ossilif erous

tain forma-

marl. Beds of limonite and lignite. Some of the

s

a

tion.

' clays carry fossiliferous calcareous concretions. Formation as a whole is decidedly ferruginous. Fossils: Ostrea sellaeformis, Ostrea divaricatA, Anomia ephippioidea, and others.

Palustrine and marine deposits, consisting of red.

Mount Sel-

ferruginous, indurated, and probably altered

man form-

greensand, with casts of shells, lenses of lignite

ation.

and clay, beds and concretions of limonite. The formation as a whole is conspicuously ferruginous.

Carries casts of Venericardia planicoata.

Geology Of Petroleum

Cknozoic Dbpositb of thb Texas Plain — Conduded

By torn

Formation

Thicknen

lithology and Charaeteristir Fossils

H

Eocene.

Wflcox formation

Feet

Palustrine* marine, and littoral deposits. The littoral deposits comprise the Queen City sand member, at the top of the formation, consisting of 50 to 200 feet of white, porous, loose, water-bearing sands, with some interstratified days. The palustrine deposits consist of lenticular maases of sand, clay, and lignite, carrying large, especially characteristic concretions (20 to 30 feet in diameter) of hard flintlike sandstone; the palustrine clays are leaf bearing, and in places carry teeth of Crocodylu9 grypua. The marine deposits consist of calcareous, glauconitio, fossiliferous maris, alternating with beds ci sand, clay, and lignite; they are exposed only on Sabine River. Characteristic fossils of the marine phase are /TeUia prima Natiea aperta, and Plewotoma silioola.

Midway formation.

Marine deposits, consisting of black and blue days with interbedded strata of limestone 'and some lenses of sand, which are somewhat rare north of the Brasos. Plona limoptis Endimatoeeraa idrichi, and other fossils.

What is here called the Dewitt formation is probably represented along the Sabine by the beds describe as the Fleming clay.

mont, a low mound covering about 225 acres rises some 15 feet above the surrounding flat country. Gas escapes in shallow pools of water, and these with sulphur incrustations in the soil were noted by A. F. Lucas. Prospecting for sulphur led to the sinking of the Lucas well, which at 1,139 feet proved to be one of the greatest gushers drilled in the United States, yielding 75,000 barrels a day. Other wells, closely spaced, were then sunk, and the field rapidly became very productive and very rapidly declined. The beds are Tertiary or later. The drill holes encounter about 1,000 feet of clay, sand, and gravel. In the lower portion of this series some limestone is found. A 20-foot bed of porous limestone below this series carries the oil. Below the porous limestone is a thick body of gypsum and rock salt; pyrite and sulphur abound. Some oil

Fbnnbman, N. M. : Oil Fields of the Texas-Louisiana Gulf Coastal Plain, y, S, Geol. Survey BvU. 282, pp. 1-146, 1906.

Gulf Coast Fields Of Tex. And Louisiana

53k

"1 t

/

/

*sr-.

w

Vsi

..A

/

4:h jll.

1: Ji; C ts S

r-

w

a

370 Geology Of Petroleum

has been obtained also from sands above the main limestone horizon. The structure of the area is domatic. According to Fenneman, there is an arching of about 200 feet in 4,000.

At Sour Lake, 20 miles northwest of Beaiunonti gas, oil, asphalt, and soiu: water at the smface led to drilling. The production, 8,000,000 barrels in 1903, rapidly declined. The wells encountered 1,600 feet of clays and sands, probably Eocene and Miocene, with some limestone and oil; salt and gypsum appeared below the clay. Deep drilling brought in heavy production again in 1915.

At Saratoga, 12 miles northwest of Sour Lake, gas, oil, and acid waters were noted at the surface. The general features are said to be similar to those at Sour Lake.

At Batson, 7 miles southwest of Saratoga, drilling was done on account of gas bubbles that were observed to rise from pools on a flat country.

At Dayton, about 25 miles southwest of Batson, gas escapes in springs. Below clays and sands about 600 feet deep limestone was encountered, and below the limestone salt and gypsiun.

Humble, about 25 miles west of Dayton and 18 miles northeast of Houston, is a highly productive field. An escape of gas led to drilling a hill on a low ridge, and a strong flow of oil was encountered at about 1,200 feet. Recently deep drilling has brought in a large production on flanks of the dome.

At the West Columbia dome, Brazoria County, Texas, wells yielding as high as 30,000 barrels were brought in July, 1920. The surface rises 18 feet above the surrounding country. Barren wells, sunk near the top of the dome, penetrated clay, the limestone cap rock, then salt. The cap rock is not productive. The first well was foimd on the southeast side of the dome, about 2,700 feet deep, in sands that rested against the steep slope of the salt dome.

At Goose Creek in Harris County, Texas, oil has been found in sands from 1,000 to 3,400 feet deep. No salt nor cap rock has been penetrated. It is not known whether the structure is domatic or not. Some of the wells yield as much as 3,000 barrels a day.

Damon Mound is one of the most conspicuous of the surficial mounds in the Gulf coast region, and the sulphur outcrops and gas showings attracted attention immediately after the discovery of Spindletop in 1901. Several wells were drilled at different points

Sbgall, Jxtlius: Oral Communication.

Gulf Coast Fields Of Tex. And Louisiana 371

on the hill m 1901-1903. These encountered oil and salt and other typical dome materials but were unprofitable. In 1917 a gas well came in with an estimated open flow of 10,000,000 cubic feet. The sand was apparently encountered at a depth of 1,447 feet. This well after being brought under control yielded gas for two months and then oil, about 5,000 barrels daily.

The Evangeline oil field,* which has been very productive, is about 6 miles northeast of Jennings, Louisiana. Jn this field there is a broad erosional depression about 10 feet above sea level, which occupies the side of a low mound some 32 feet above the sea. The productive area is about 1 square mile. Here, as at Spindletop, Texas, gas escaped from a spring in the mound. Because of the surface features, which are similar to those of Spindletop, a well was simk and struck oil at a depth of 1,822 feet. The beds are Miocene and Quaternary. Little limestone is present. The domatic structure is not so clearly shown as at Spindletop. According to Harris the oil has come up along a strong fault JBssure.

At Anse la Butte, Louisiana, gas bubbling on a small depression led to the development of a gusher. Structurally the area is probably a steep dome.

At Welsh gas bubbling in a well led to sinking a hole that developed a small oil area.

The New Iberia district' is in Iberia Parish, Louisiana, on Tete

Bayou, about 6 miles east of New Iberia. Pronoimced escapes of

petrolemn gas and so-called ''paraffin beds" were discovered in this vicinity in the smnmer of 1916, and these showings led to drilling and discovery. The production to 1918 was small.

The origin of the structure of the Gulf coast fields is one of the most perplexing problems in geology. Perhaps the most widely credited theory is that of Harris, who attributes the doming up to the force of crystallization. He maintains that salt water rose along faults and fissures and soUdified, pushing up and doming the weak clays. This force has been recognized by Becker and has

Hats, C. W., and , William: Op. cU.

Dbussen, Alexander: A Review of Developments in the Gulf Coast Countay. Am. Assoc. Pet. Geol. BuU,, V9I. 2, pp. 16-37, 1918.

'Harris, G. D. : Op. dt. p. 50. Fenneman, N. M. : Op. cU., p. 100.

'Deubsen, Alexander: Review of Developments in the Gulf Coast Country. Am. Assoc. Pet. Geol. Btitt., vol. 2, pp. 16-37, 1918. .

Harris, G. D. : Oil and Gas in Louisiana. U. S. GeoL Survey BvU. 429, pp. 1-192, 1910.

Geology Of Petroleum

Loo OF BouYAB No. 1 Well of New Iberia Oil Co., New Iberia, LotnsiANA

(After Deussen)

Blue surface clay

Gray sand; gas

Water gravel

Cnist of sand rock

Soft gumbo and boulder

Hard gumbo

Hard gumbo

Packed sand

CrystaUiBed sand; pyrite

Soft gumbo; streaks of crystallized sand and pyrite

Hard gumbo

Hard gumbo

Hard gumbo

Crystallized sand

Hard gumbo

Dry sand; gas j

Very hard gumbo

Oil sand

Hard blue gumbo

Hard gumbo

Sandstone; pyrite, oil and gas

Hard black gumbo

Sandstone; pyrite, oil and gas

Hard sandrock

Cap rock

Depth

Feet

1,008

been recently discussed by Taber in connection with metaUiferous deposits. Not all investigators have accepted this theory. Norton has come to the conclusion that the domes represent loci of hot solutions containing lime carbonate, sodium chloride, lime sulphate, etc., ascending through channels opened by faulting and depositing at the surface great masses of travertine and calcareous sinter at the time the sedimentary rocks were being deposited.

Tabbr, Stephen: Pressure Phenomena Accompanying the Growth of Crystals. Nat. Acad. Sci. Proc, vol. 3, pp. 297-30 J, 1917.

'Norton, E. G. : Origin of Louisiana and East Texas Salines. Am. lost. Min. £ng. Trans., vol. 51, pp. 502-513, 1915.

Gulf Coast Fields Of Tex. And Louisiana 73

Later they were covered up, and as compacting and subsidence took place the strata sagged away from the hard cores, while at the same time oil was concentrated along bedding planes, rising in the sandy or limy beds to the tops of the domes, which were obviously above the old salt deposits.

As many of the domes, at least, show quaquaversal structure, it is assumed that in this field the occurrences of salt and oil are generally in quaquaversals. However, there are many Gulf districts in which the dome structure has not been proved, and some where the principal structural features appear to be faults. , There is a fairly uniform occxurence of limestone or dolomite above the salt and gypsum; indeed in many districts it is this fractured dolomite that carries the oil. Its stratigraphic position suggests that the limestone is a sedimentJtry rock. One would not expect materials deposited from hot water at the surface of the earth to be as regularly layered as these. Nor does it seem probable that fissures in the soft clay capping of these zones would have let out salt water in sufficient quantities to deposit such enormous amoimts of salt. Moreover, if they had, and if the water could have escaped, it would seem probable that the oil would have escaped also. It is improbable that crystals would thrust up hundreds or thousands of feet of sedimentary rock and not fill the great cavities which were left in the Umestone that carries the oil. Solutions move to points of less pressure and by deposition fill any available openings already formed. These cavities had not been filled with salt, otherwise they could not have served as containers for the oil.

The domes of the Gulf Coast country have recently been discussed by Deussen, who recognizes three classes — shallow domes, domes of medium depth, and deep-seated domes. In the shallow domes the cap rock lies within 600 or 600 feet of the surface, and salt within 700 or 800 feet. Most of them are accompanied by superficial mounds, except where the mounds have been eroded. There is usually a Uttle oil in the cap rock, but these domes as a rule are not very profitable conunercially. They include Damon Mound, Pierce Junction, Blue Ridge, Hoskins Mound, Ba ber Hill and South Dayton.

The domes of medium depth have a cap rock about 1,000 to 1,200 feet below the surface, and salt at 1,200 to 1,600 feet. The mounds are not pronounced. The cap rock contains much oil; usually

'Deussen, Albxandeb: Am. Assoc. Pet. Geol. BvU.f vol. 2, pp. 16-37, 1918.

374 Geology Of Petroleum

gushers are developed in these domes. They include Spindletop, Hiunble, Sour Lake, and Saratoga.

The deepHseated domes have been drilled as deep as 3,000 feet, but no cap rock and salt have been encountered. Overlying mounds are absent. The oil] produced in these domes comes from sands above the level of the cap rock, possibly leaking out of it. The deep-seated domes include Goose Creek, Edgerly, Terry, and Welch. These may be simply anticlines, or there may be underlying salt domes that supply oil to the sands.

A grouping of the wells of these three classes shows that the shallow ones and those of medium depth occur near together, and that the deeper ones he southeast of the shallow ones, indicating a dip of the rock south and toward the Mississippi Biver. The persistence of limestone above the salt suggests that many of the deposits are at the same stratigraphic horizon* It is not unlikely that these salt beds are simply in anticlines and faulted flexures formed when the rocks of the region were less consolidated than they are now. The salt was probably folded and became thicker at the crests of anticlines, just as has been observed on the Englen anticline, at Stassfurt, and in other deposits of Germany. The limestone, being stronger than the mud or clay, probably broke up into blocks, and the shattered limestone supplied reservoirs for the oil.

Van per Gsacht, W. a. I. M. V. W. : The Saline Domes of Northwestern Europe. Southwestern Assoc. Pet. GeoL BuQ., vol. 1, pp. 86-92, 1917.

Rogers, G. S. : Intrusive Origin of Gulf Coast Salt Domes. Eeon. Geologyt vol. 13, pp. 447-485, 1918.

' ,

,'f,f

vl/

Chapter Xx

ROCKY MOXTNTAm FIELDS WYOMING

General Features. — Wyoming is made up of lofty moimtain ranges and intermontane basins. In the northern part of the State there are three great anticlinal ranges, between which lie two great syncUnal basins. The Black Hills, in the northeast comer, extend into Wyoming from South Dakota; west of them is the Big Horn Range; and west of it the Shoshone range of Yellowstone Park. Southwest of the Big Horn Mountains and nearly parallel to them is the Wind River Range. The Front Range, known in Wyoming as the Laramie Range, occupies a large area in the southeast quarter of the State. In the southwest comer is the Teton Range, about parallel to the Wasatch Range of northern Utah. The Owl Creek Mountains he southeast of the Shoshone Mountains. In the central and southern part of the State are the Rattlesnake and Sweetwater mountains.

The mountains are, in the main, anticlinal folds, the tops of which are eroded, so that in some of them the strata from the pre- Cambrian to the Tertiary are exposed (Fig. 161). On the flanks of the mountain folds and in the interiors of the basins there are many subordinate folds, and on these are the principal oil fields. There are altogether more than 100 anticlines and domes (Fig. 162). Many of these have been drilled without yielding oil or gas. About a score have proved productive, and more than half of these have produced oil and gas in considerable quantities. Noteworthy among them are the Salt Creek, Grass Creek, Big Muddy, GreybuU, Basin, Elk Basin, Pilot Butte, Byron, Rock River, Lost Soldier, Lance Creek, and Buck Creek fields.

A considerable part of Wyoming is underlain by Cretaceous beds, and these have suppUed nearly all the oil produced. The principal productive strata of the Cretaceous are in the Colorado group, which includes the chief oil-producing sands in central Wyoming and in the Big Horn Basin. In the region north of Lusk, oil has been produced recently from the Muddy sand, a

Geology Of Petroleum

PETBOLBnM Mabkxtes in trc Rockt Moontaut Pieu> a IN Babrbls

T-,

„,.

Wyomim

Uodiu*

121 ,231

6,234.137 8 .978 .680

44,917 99,399

Fig. 161. — Sketch map ot Wyoming.

short distance below the Mowry. Heavy black oil is found in the Embar of the Permian and Pennsylvanian. All the reservoir rocks are sandstones, except the Embar, which is a porous Umestone. The saturation of the rocks is lower than in Oklahoma, and the folds are steeper.

With a few exceptions only closed folds yield noteworthy amounts of oil. The closed folds are mainly domes. In one or two localities oil occurs in fault traps. In the Upton-Thornton field the oil is OD a terrace. A considerable number of plunging anti-

Rocky Mountain Fields

cUries, terraces, and monoclines of low dip have been drilled however, without finding oil.

The oil of the Douglas field, which is not very productive, has probably accumulated at or near an unconformity between steeply tilted Cretaceous rocks and flat-lying Tertiary beds. The Labarge and Spring Valley fields, in the southwestern part of the State, are along faults. None of these fields have produced much oil. Oil seeps are common, one or more being present in at least twelve of the fields.

Hopn

Johnson'

UNcb.LKr

. P Carter V'NTA.

muff a/9 aam/n

Arr//4*r///// O

(r cr

mof/MM

Carbou

K.AC/r

Campbell

Crook

QCa/Cr

Er9E

Oi/fMfL'Jt

Fia. 16i2. — Map of Wyoming showing position of oertpin oil and gas pools

(black dots) and prospects (circles.)

The! water on which the oil floats is not all saline, although high salinity is noteworthy in parts of the Salt Creek field. The low salinity in the Grass Creek field is unusual for a productive field. Fresh water below the oilin the same strata generally suggests communication with superficial sources, a condition which may permit leakage of oil and gas. A Uttle water, not highly saline, is found at a depth of 2,700 feet in a faulted area on the west edge of the Salt Creek dome. The strata dip steeply toward the Salt Creek field. Water circulating down the dip and rising in a fractured area would sweep the oil sand free of brine above that area.

Geology Of Petroleum

Petboleum Marketed, Valxte, and Average Price per Barrel im

Wtomino, 1914-1917, bt Districtb

Yew

Big Horn

Qaaatity (Bwrab)

Value

Prioe per

$1.00

Qnuitity

(Bwreb)

Value

Price per

fivrel

QoMitity (Bwreb)

3.421.325 3.971.128 3.933.403 3,910.511

Vafaie

$1,541,494 1.965.564 3.363.364 3.733.291

Fkiee per Bend

$0,451

Quantity (Barrels)

1.369.807 2.766,402

Vahie

$74,126 1,336,840 4,190,774

Ayerage

Price per

Barrel

$0,751

Quantity (Barreb)

720,968 1,530,264

Vafaw

$095,571 2,266.794

ATerage

Price per

Band

$0,965

Conwse

Qoaathy

(Barreb)

Vahie

n

$726,738

Avenge

Price per

Barrel

$1,092

Other Countiea

(Quantity

(Barrels)

Value

*15.477

120. 158

"l.OZS

''10. 146

*4,234

*7.617

Average

Price per

Barrel

$1,302

Total

Quantity (Barreb)

3.560.375 4.245.625 6.234,137 8.978.680

Vahie

$1,679,192 2.217.018 6.644.080

11.047.876

Avenge

Price per

Barrel

$0,472

'Included in "Other Counties." Converse, Crook, and Uinta Counties. 'Converse, Park, and Uinta Counties. ''Converse and Uinta Counties. 'Uinta County.

Rocky Mountain Fields

Sections Showing Occurrences of Oil and Gas in Sobcb of the Rockt

Mountain Fields

(After Hares. Correlations Approximate and Incomplete)

o, oil; g, gas; +, seeps or small production of oil or gas

Ssrstem or Series

Spring Valley and Labarge"

Grass Creek*

and Oregon Basin

Shoshone River.*

Tertiary.

Wasatch. +o.

Wasatch.

Wasatch.

Evanston.

Fort Union.

Fort Union.

Fort Union.

Tertiary (?).

Lance.

Ilo (Lance).

Ilo.

Cretaoeoua (Montana).

Adaville.

Meeteetse.

Meeteetse.

Montana, undifferentiated.

Mesaverde.

Gebo.

Eagle.

Hilliard.

Cody.

Colorado.

+ +

o. o.

Pierre.

Cretaceous (Colorado).

Basin.

Frontier, o.

Frontier, o.

Benton. Torchlight. Peay.

Aspen, o.

Mowry.

o. g.

Thermopolis. g.

Cretaceous.

Bear River, o.

Cloverly.

"Cloverly." g.

Cloverly. o. g. Greybull.

Beckwith.

Cretaceous (7).

Morrison.

Morrison, g.

Morrison.

Juraaste.

Twin Creek.

Sundance.

Permian.

Pennsylvanian.

"VsATCHt A. C: Geography and Geology of a Portion of Southwestern Wyoming, with Special Reference to Coal and Oil. U. S. Geol. Survey Prof. Paper 56, pp. 157-158, 1907. ScHULTz, A. R.: The Labarge Oil Field, Central Uinta County, Wyoming. U. S. Geol. Survery BuU, 340, p. 364, 1908.

*HawsTT, D. F.: The Shoshone River Section, Wyoming. U. S. Geol. Survey BuU. 541, pp. 89-113, 1914, and unpublished data.

nmx, F. F. : Basin and Greybull Oil and Gas Fields. Wyoming State Geologist's Office BuU. 10, p. 40, 1914 (1915).

Fig. 162 is an outline map showing the position of the principal mountain ranges, the oil and gas fields, and certain domes or other

Geology Of Petroleum

Sections Showing Occxtrrbncb of Oil and Gas in Some of thb Rocky

Mountain Fields — Continued (After Hares. Correlations Approximate and Sections Incomplete) o, oil; g, gas; +, seeps or small production of oil or gas.;

SysteiD or Beriflt

Tertiary.

Gretaoeous (Montana).

Cretaceous

Cretaceous.

Cretaceous (7).

Jurassic.

Triassic.

'Basin''

Lander*

Undifferentiated Fort Union and Lance.

Wind River,

Absent or concealed.

Mesaverde.

Mcsaverde.

Cody.

Mancos.

Frontier.

Torchlight. +

Peay. +g.

Mowry. +o.

+0.

Thermopolis. +

Dakota.

Cloverly.

Lower Cretaceous

Morrison.

Morrison.

Wyoming/

Wasatch. +

Laramie. Fort Union.

Fox Hills.

Fort Pierre.

Niobrara.

Fort Benton.

Permian.

Pennsylvanian.

/

Sundance.

Chugwater. +o.

Embar. o.

Como.

Shirley.

Triassic.

Permian. Carboniferous.

Central WyoiZLLQg0

White River.

+

Wind River.

+?

Fort Union.

Lance.

Lewis.

Mesaverde. Teapot. H- Parkman.

Steele. Shannon.

Niobrara.

Carlile.

Frontier.

Wall Creek. +

+ Peay. +

Mowry.

Thermopolis.

Lower Cretaceous.

&hale. . Conglomerate. +

Morrison. +

Sundance. +

Chugwater. +

Embar. '

Tensleep. +

Amsden.

''LuPTOir, C. T.: Oil and'Gaj Near Basin, Big Horn County, Wyoming. U. S. Geol. Survey Bull. 621, pp. 157-190. 1916.

*WooDBUFF, E. G.: The Lander Oil Field, Fremont County, Wyoming. U. S. Geol. Survey Bull. 452, 1911.

Knight, W. C: A Preliminary Report on the Artesian Basins of Wyoming. Wyoming Univ. Exper. Sta. Bull. 45, 1900. Knight, W. C, and Slobson, E. E.: The Dutton, Rattlesnake, Arago, Oil Mountain, and Powder River Oil Fields. Wyoming Univ. School of Mines, Petroleum ser., BuVi. 4, 1901.

'Habkb, C. J.: Anticlines in Central Wyoming. U. S. Geol. Sxuvey BuVL. 646, pp. 233-279.

*In a later paper (U. S. Geol. Survey 656, 1917) HEWXTrand Lupton place the Meettse above the Mesaverde.

Rocky Mountain Fields

381;

Sectioks Showing Occukrence of Oil and Gas in Some of the Rockt

Mountain Fields — Condvded

(After Hares. Correlations Approximate and Sections Incomplete)

o, oH; g, gas; seeps or small production of oil or gas

System or Series

Salt Creek and Powder River*

Douglasi

Moorcroft

and Newcastle*

Boulder, Colorado'

Florence, Colorado"

Tertiaiy.

White River, o. g.

Fort Union.

Fort Union.

Tertiary (?).

Lance.

Lance.

Laramie (7).

Fox Hills.

Fox Hills.

Fox Hills.

Fox Hills.

Trinidad. (7).

Cretaceous (Montana) .

Pierre. Parkman. Shannon, o.

Pierre. Parkman (7). Shannon (7). +

Pierre.

Pierre. Hygiene, o. g. o.

Pierre.

Niobrara, o.

Niobrara.

Niobrara.

Niobrara, o.

Niobrara.

Benton. Wall Creek. 0.

Mowry. +

Benton. +o. g. Wall Creek (?).

Mowry.

(o7)

Carlile.

Benton. o.7

Carlile.

Cretaceous (Colorado)

Greenhorn.

Greenhorn.

GraneroB. Mowry. o.

Graneros.

Cretaceous.

Dakota (?). +

"Cloverly." o. +

Dakota. +

Dakota.

"Dakota." -f

Fuson. +

Lakota.

Cretaceous(?).

Morrison. +

Morrison.

Morrison.

Morrison.

Morrison. +

Jurassic.

Sundance. +

Sundance.

Sundance.

Chugwater.

Lykinn.

Carboniferous.

Forelle (?). Satanka (?). + Casper.

Lyons. Fountain.

Wbqkmann, C. H.: The Salt Creek Oil Field, Natrona County, Wyoming. U. S. Geol. Survey Bull. 452, pp. 37-83, 1911 ; The Powder River Oil Field, Wyoming. U. S. Geol. Survey BuU. 471, pp. 66-75, 1912. Compare with later and more detailed correlations, page — and — .

'Babnbtt, V. H. : The Douglas Oil and Gas field, Converse Wyoming. U. S. Geol. Survey BulL 541, pp. 49-88, 1914.

Babnbtt, V. H.: The Moorcroft Oil Field and Big Muddy Dome, Wyoming. U. S. Qeol. Survey BtUl. 581, pp. 83-117, 1914. Dabton, N. H.: Preliminary Report on the Geology and Underground Water Resources of the Central Great Plains. U. S. Geol. Survey Prof. Paper 32, np. 334, 364. 379-388, 1906.

'Fenneman, N. M. : Geology of the Boulder District, Colorado. U. 8. GeoL Survey BuU, 265, pp. 76-98, 1905.

'"Wasbbubnb, C. W.: The Florence Oil Field, Colorado. U. 8. QeoL Survey . 881, pp. 517-644, 1910.

structural features that are barren or have not yet been fully tested. A number of fields yield gas or gas with relatively little oil. The gas fields include Oregon Basin, Buffalo Basin, Bonanza,

382 Geology Of Petroleum

Sand Draw, Sweetwater, Sheep Mountain, Oil Mountain, Pine Dome and North Casper.

Salt Creek. — The Salt Creek field is about 40 miles north of Casper and includes a productive area of 7 square miles. It is the most productive field in Wyoming and yields a high-grade paraffin oil, greatly prized on account of its gasoline content. Indications of oil in the Salt Creek field include several oil and gas seeps in shale, deposits of ozokerite along fault planes in shale, and oil seeps from the Shannon sandstone. Several oil and gas seeps from the shale were known prior to the drilling of the discovery well in the Salt Creek anticline.

Oil is found in four sands — the Shannon, of the Montana; and the first Wall Creek, second Wall Creek, and third Wall Creek of the Colorado. Each of these sandstones is capped by shale. The dominant feature of the structure is a broad anticline 18 miles long and about 6 miles wide on which there are two broad domes— the Salt Creek dome and the Teapot dome. The east limb of the anticUne has a gradual dip, the west limb is more abrupt. Several faults strike across the domes; most of them are normal faults and have displacements ranging from 5 to 100 feet. Some thrust faults are present.

The wells produce both oil and gas. Some are gushers. On three sides of the Salt Creek dome (Fig. 37, p. 131) the variation in position of the oil is not over 50 feet, but on the north end, as stated by Wegemann, the oil extends downward about 150 feet lower, probably because the gathering area was greater in that direction. The oil is under pressure, and much gas is dissolved in it rather than segregated in pools above the oil.

Oil has been found also in the second Wall Creek sand, which is about 25 feet thick and lies 250 feet below the first Wall Creek sand. Wegemann states that the productive area in this sand is probably larger than the productive area in the first Wall Creek sand. In nearly all wells drilled in the Salt Creek field some oil is encountered in shale. (See p. 157.)

The Teapot dome, to the south, is included in a naval reserve.

At the crest of the dome the first Wall Creek sand is reached at

a depth of about 1,000 feet. The first Wall Creek sand is about

iWbqbmann, C. H.: The Salt Creek Oil Field, Wyoming, U. S. GeoL Survey BvU. 670, 1917; also BvU, 452, pp. 37-84, 1911.

Rocky Mountain Fields

FoBMATioNS IN Salt Oil Field, Wtomino

(After Wegemann)

System

Series

Group

Formation

Character

Thickness (Feet)

Tertiary.

Eocene.

Wasatch formation.

Yellow sandstone, gray shale and coal.

2,400

Fort Union formation.

Fine-Gained bluishwhite sandstone and gray shale.

2,000

Tertiary (?)

(?)

Lance formation.

Concretionary bu£F sandstone and shale.

3,200

Cretaceous.

Lewis shale with thick sandstone at top and another sandstone in middle.

Sandstone, white to brown, and gray shale.

1,400

Mesaverde formation, including Parkman, and Teapot sandstone members.

Shale, sandstone, thin coal beds.

Steele shale, including Shannon sandstone member. Carries oil.

Buff sandstone and gray shale.

Colorado .

Li{(ht-c6lored shale, in parts somewhat arenaceous.

Cretaeeous.

d

Dark shale.

Wall Creek sandstone member and lower sands with interbedded shale. Carry oil.

Buff to white sandstone and gray shale.

Dark shale.

Mowry shale member.

Firm slaty shale, usually forming escarpment.

Weathers lieht gray and bears fish scales.

Dark shale.

Lower Cretaceous.

(Hoverly formation.

Thin sandstone and dark shale.

Conglomerate.

Cretaceous (7)

(?)

Morrison formation.

Variegated shale with several sandstone beds.

Juraasic.

Upper Jurassic.

Sundance formation.

Shale, limestone, and sandstone.

125 feet thick and consists of medium-grained dirty-gray sandstone containing thin calcareous beds and numerous lenses and layers of sandy shale ranging in thickness from a fraction of an inch to several feet. The distribution of the oil in the sand is dependent on

384 Geology Of Petroleum

differences in the porosity of the layers composing it, due to differences in the sizes of the sand grains and the amount of cementing material between them. The porosity of the sand in the several layers of the formation differs greatly. A specimen of massive sandstone from the upper part of the Wall Creek, collected by Wemann and tested by Van Orstrand, has a porosity of 25.8 per cent; another specimen, somewhat study, taken near the base of the formation, has a porosity of 20.4 per cent; and a specimen from one of the thin layers of calcareous sandstone, called the drillers "shells," has a porosity of only 7.6 per cent.

Owing to variations in the character of the sand, oil is encountered in the wells in pay streaks; in some places the "pay" is found at the very top of the sand; in others it is some distance below the top, only small amoimts of oil and gas being found when the sand is first struck. There are no dry holes within the known oil pool, some part of the sand being capable of commercial production wherever it is tapped.

The distribution of the oil about the Salt Creek dome is unusually regular. The line marking the contact of the oil pool with the water that occupies the sand on the flanks of the fold below the oil varies only about 150 feet in elevation in the entire circuit of the dome, lying between 3,425 and 3,575 feet above sea level.

The first conunercial wells in the Salt Creek field were drilled in the Sharmon pool, which is at the north end of the dome, about 3 miles north of the present town of Salt Creek. The oil is obtained from the Shaimon sand, which lies 2,000 feet above the Wall Creek and forms the rim rock of the Salt Creek pool. The Shannon sand is encountered in the wells at Shannon at depths ranging from 700 to 1,000 feet. It consists of two ledges separated by 30 or 40 feet of sandy shale. The upper ledge of sandstone is about 40 feet thick, and the lower one 50 feet. The oil is confined to the lower ledge, the upper being water bearing. The porosity of the sand, determined by Van Orstrand, is 26.7 per cent.

The Shannon wells are small, the average well producing daily from 5 to 15 barrels of heavy paraffin-base oil. The pool appears to contain not more than 160 acres. Some of the wells flowed slightly when first struck, but all of them were pumped. No oil is now being taken from them. The pool is on the pitching north

Wbgemann, C. H. : The Salt Creft Oil Field, Wyoming. U, S. GeoL Survey 670, p. 27, 1917.

Rocky Mountain Fields 385

end or "nose" of the Salt Creek anticline, at a place where the fold is narrowed abruptly. The oil extends farther down the end of this fold than it does on the western flank. The limits on the east are not accurately determined.

Powder River. — The Powder River or Tisdale field is a dome southeast of the Big Horn Mountains. The strata in which the oil occurs are lower in the geologic column than those which bear oil at Salt Creek. The oil of the Powder River field is a heavy lubricating oil.

The Powder River dome is roughly outlined in plan by the outcrop of the Wall Creek sandstone. The dome is a somewhat irregular oval 16 miles long from north to south and 10 miles wide from east to west, its axis trending approximately north. About 15 miles north and a little west of the highest point of the dome is a smaller but similar dome, which lies just west of the villagfeof Kaycee. The two domes are connected by a low anticUnal arch and may be considered parts of a single structural feature 30 miles long.

Oil has been found in five different beds in the Powder River field. Of these the lowest is in the Sundance, a small quantity of oil, along with brackish water, rising from the upper strata of that formation in the SW. sec. 33, T. 41 N., R. 81 W. A massive sandstone about 6 or 7 feet thick near the base of the Morrison formation contains a small quantity of oil in the NE. 34 sec. 33, T. 41 N., R. 81 W., where a tunnel has been driven into the sand,- stone. In Oil Canyon a small oil seep was noted in a sandstone near the middle of the Morrison. In the Mo wry shale member oil is reported in the well in Oil Canyon, where a few quarts was obtained at a depth of about 300 feet. The principal reservoir of oil in the field, however, is the coarse conglomeratic sandstone, 56 feet thick, which is probably the Cloverly. It has been prospected with results that are not encouraging.

The open wells in Trail Canyon, on the crest of a secondary fold, which here forms also the axis of the anticline, obtain oil from the Cloverly (?) sandstone. It has been suggested that the oil from the Embar formation has risen to the sandstone beds above.

. Wegemann, C. H. : Op, cU., p. 33.

Wegemann, C. H. : The Powder River OU Field, Wyoming. U, S, Gepl, Survey BvU, 471, p. 56, 1912,

386 Geology Of Petroleum

Big Muddy Dome. — Ilie Big Muddy dome is in Converse and Natrona Counties, near the North Platte River, about 15 miles east of Casper. The following generalized section shows the character and thickness of the Mesozoic and later formations and their relations to each other:

The Big Muddy dome is a slight arch of the strata extending over an area of about 72 square miles.

At the surface that part of the Pierre formation which lies below the Parkman sandstone member crops out. The outline of the dome is shown by the outcrop of the Teapot sandstone member. Oil is obtained from the Shannon sand, from a stray sand, and from the Wall Creek sand of the Colorado. The depth of the Shannon ranges from 950 to 1,150 feet; the Wall Creek is about 2,000 feet deeper.

In the field proper there are two anticlines — a northerly one trending east, on which oil is obtained, and another in the southwestern part of the field trending northeast and nearly east. These are separated by a shallow syncline. A well on the southwestern anticline obtained water. This fold may be out off by a fault to the southwest. - -

Douglas. — The Douglas oil and gas field (Brenning Basin) lies west of Douglas, in Converse County. Oil springs are found at many places in this region.

The White River formation in the Douglas field rests unconf ormably on the upturned edges of the older rocks, which include nearly all the beds of the Colorado and Montana groups, both of which are known to yield oil in the Salt Creek field and near-by areas. Hewett beUeves that the oil in migrating upward along bedding planes and through porous sandstone finds a barrier when it reaches the White River formation, so that oil and gas acciunulate near this line, penetrating the White River only where they encounter lenses of porous material or fault planes.

Two grades of oil are produced — a heavy lubricating oil and a light oil of good quaUty. The gas is rich in propane and butane. The field, though extensively prospected, has not made a large production.

Barnett, V. H. : Possibilities of Oil in the Big Muddy Dome, Converse and Natrona Counties, Wyoming. U. S. Geol. Survey , 581, pp. 105-117, 1915.

, D. F. : liie Douglas Oil and Gas Field, Converse County, Wyoming. U. S. GeoL Survey Bufl. 641, pp. 89-113, 1914.

Rocky Mountain Fields

Gboixxjic Fobmations in or Near Powder River Oil Field, WTOMma

(After Wegemann)

System

Series

Group

Formation

Description

Thickness (Feet)

Upper Cretaceous.

Montana (4.350 feet).

t

Fox Hills sandstone.

White sandstone and shale. Marine.

700?

g

Shale with several sandstone beds, indudins that which forms Little Pine Ridge. Marine.

1,000

P a r k m a n sandstone member.

Massive buff sandstone overlain by shale and thin cioal beds. Marine and fresh water.

Shale with sandstone stratum 250 feet above its base. Marine.

1,100

,

Shannon sandstone lentil.

Oil-bearing horison near base. Marine.

Gray shale. Marine.

1,025

Cretacseoos.

Colorado (2,405 feet).

Niobrara shale.

Light-colored shale, in parts somewhat arenaceous. Marine.

Dark shale, several calcareoys beds. Marine.

Wall Creek sandstone lentil

Buff sandstone, ripple marked and cross-bedded. Petrified wood, marine shells, and fish teeth. The principal oil sand of Salt Creek.

Dark shale, several sandstone beds. Marine.

Mo wry shale member.

Firm slaty shale, usually forming escarpment. Weathers light gray and bears fish scales. Marine.

Dark shale with one thin, persistent, strongly ripplemarked sandstone.

DakoU (?) sandstone.

Conglomeratic sandstone, oil bearing. Fresh water.

Jurassic (?).

Morrison formation.

Varienited shale with several sandstone beds which in certain localities bear oil. Fresh water.

Jurassic.

Sundance formation.

Shale and limestone in upper part; white sandstone in lower part.

This district has not produced profitable quantities of oil, and its importance is problematic.

Geology Of Petroleum

Generalized Section of Formations Involved in the Biq Muddy Dome,

Wyoming (After Bamett)

Sywtem

Series

O

Group

Formation*

and Member

Character

Type of Topography

Thickness (Feet)

at

e

-Unconformity- White River formation.

-Unconformity- Lance formation.

Alluvium, sravel, and sand.

Sand dunes, graveltopped hills, and valley fiats.

25 +

Clay, conslomeratc, and sandstone.

Flat-topped hills and gentle slopes; thin soil.

kl

e

o

0 Os

o

Friable sandstone and shale, with local beds of coal.

Rolling hills and broad gentle slopes; thin, sandy soil and alkali flats.

200 +

Montana .

Fox Uills forination, base uncertain.

Friable sandstone and shale with local coal beds near top.

Ridges of sandittone and valleys in shale; sandy soil.

s

eS

o fc!

Sandy shale.

Valleys; thin clay soil.

Teapot sandstone member.

Gray and bufif sandstone and carbonar ceous shale.

Low ridges, barren rock slopes, and pinenclad

Sandy shale.

Valleys; thin clay soil.

P ar k m a n siindstone member.

Friable sandstone and beds of shale and coal.

Ridges of some prominence and broad, grassy slopes.

Dark shale.

Broad valleys; thin soil.

Colorado .

>}iobrara shale .

Gray to buff calcareous shale.

Low rounded ridge& and brown slopes.

Od

Dark shale.

Narrow valleys; thin soil.

Wall Creek sandstone member.

Gray and buff sandstone and beds of shale.

Ledges and hogback ridges covered with small pines.

Dark shale including Mowry shale member.

Broad valley with low, rounded pineclad ridge of Mowry shale. Thin soil.

1,200

Cleverly formation.

Buff sandstone and shale with conglomerate in lower part.

Ledges, hogback ridges, and barren slopes of rock ; thin sandy soil.

o

if

c3 OS

Morrison formation.

Green, buff gray, and maroon shale and thin beds of sandstone.

Gentle slopes below ridges of Cloverly rocks.

Jurassic.

Sundance formation.

Greenish-gray limestone and sandstone.

Rocky Mountain Fields 389

Lander. — The Wind River Range lies southwest of the Big Horn Basin and its southwestern bordering range, the Owl Creek Mountains. The Wind River Range is an anticlinal uplift striking northwest. Northeast of it there is a foothOl fold, the Shoshone anticline, 40 miles or more long, that strikes northwest, parallel to the Wind River Range. This anticline has an undulating crest, developing four elongated domes. These from northwest to southeast are the Sage Creek dome; the Plunkett dome (Big Popo Agie), near Lander; the Dallas dome (Little Popo Agie) ; and the Sweetwater dome. Along the crest of the anticline the Red Beds (Chugwater), of Triassic age, crop out. Wells drilled on the crest encounter the Embar (Carboniferous), which yields a heavy oil. The Embar consists of limestone, some of it shaly and cherty, and of shale. Two members consist of very shaly sandstone containing a large percentage of lime carbonate and some bituminous matter which comes to the surface in oil seeps. Woodruff considers the Embar the main source of oil in the region, although oil is found also in overlying formations. The Chugwater (Red Beds), above the Embar, consists of red shales and sandstones nearly 1,500 feet thick. It contains lenses of gypsum. Above the Chugwater are Mesozoic shale, sandstone, and limestone.

The oil is found along the top of the anticline. On the Little Popo Agie dome there is a thrust fault miles long with a throw of about 1,180 feet. No springs occiu* along the line of the fault, and neither oil seeps nor asphalt beds were noted near it. The fault is believed to extend downward to the oil-bearing strata, but the abundant shale in the Chugwater formation has probably sealed the break and prevented the escape of gas or oil. Several oil seeps and tar springs, however, occiu* along the axis of the anticline. It is these springs, together with the anticlinal structure, that led to the prospecting for oil. Most of the wells show ga. The oil flows from several wells, but some are pumped. Th6il is a heavy oil with an asphalt base, and production is small.

Maverick Springs, Fremont Ceunty. — The Maverick Springs' district is in the Wind River Basin, just south of Owl Creek

WooDRUPP, E. G.: The Lander Oil Field, Fremont County, Wyoming U. S. Geol. Survey BuU. 452, pp. 1-36, 1911.

Op. cU.fp. 12.

'Collier, A. J.: Anticlines Near Maverick Springs, Fremont County, Wyoming. U. S. Geol. Survey BvU. 711-H, pp. 149-166, 1920.

390 Geology Op Petroleum

Mountains. Three domes are developed along an axis ihat strikes northwest.. These are, from northwest to southeast, the Circle Ridge Dome, the Big Dome, and the Little Dome.

On the Circle Bidge, the top of the Embar formation is exposed. In the Big Dome the Chugwater, composed of sandstones, shales, and gypsum, covers the Elmbar, which consists of limestone, shale, and phosphate rock, with some sandy layers (Fig. 163). The oil is found in a sand in the Embar group and is developed on the Big Dome which has several hundred feet of closure. It is a heavy asphaltic oil like that obtained at Lander.

Pilot Butte.— The Pilot Butte field is near the center of Fremont County,* in the west-central part of the State, about 40 miles southwest of Thermopolis and 26 miles north of Lander. It is on an elongated dome that lies a little east of north of the north end of the Shoshone anticline and is an Echelon fold or uplift on its basinward flank. The oil produced has a paraffin base and is obtained from Cretaceous sandstone. The oil is found in an interbedded sandstone about 1,500 feet above the base of the Pierre. A sandstone on Dry Creek in the Pierre about 1,450 feet above the base is correlated with the upper oil sand of Pilot Butte. The sandstone here is a friable, porous buff rock that has a few streaks of grit with grains as much as a quarter of an inch in diameter. It is overlain and imderlain by sandy shales, and the total thickness of the sandy zone is 40 feet; the sand proper is about 15 feet thick. This horizon is approximately the same as that of the Shannon sandstone, which produced oil in the Salt Creek and Big Muddy fields. Other sands should be encoimtered below.

Central Wyoming. — The city of Casper is the most important center of refining in Wyoming and the headquarters of many producing and prospecting companies. The Salt Creek field is northeast of Casper, and the Big Muddy dome is about 15 or 20 miles to the east. To the west of Casper for about 100 miles e3ctendiDg nearly to Lander, there is a broad belt of Cretaceous, Tertiary, and Quaternary rocks. The Cretaceous is thrown into folds nearly all of which strike northwest. These folds have been mapped and described by Hares.

ZncGLBB, Victob: The Pilot Butte Oil Field, Fremont County, Wyoming. Wyoming Geol. Survey BuU. 13, p. 143, 1916.

*Hare8, O. J. : Anticlines in Central Wyoming. U. S. Geol. Survey BuU, 641, pp. 233-279, 1917.

Rocky Mountain Fields

Fio. 163. — SectioDS of Big Dome and of Little Dome, Maveirick SpfeiBgB ron, Fremont County, Wyoming. (After Collier,) Oil is discovered on the Big Dome in the Embar formation.

393 Geology Of Petroleum

The Carboniferous and Cretaceous formations which produce oil in other Rocky Mountain fields are well developed in central Wyoming, and in places the oil seeps from them, but in only a few places are these formations covered by impervious shale and within reach of the drill in folds favorable for the accumulation of oil and gas. The noteworthy folds, according to Hares, are the Pine dome, the Oil Mountain ianticline, the anticUnes between Poison Spider and South Casper creeks, and the Emigrant Gap, Iron Creek, North Casper Creek, and Bates Hole anticUnes. The Cretaceous oil sands ar blow the surface in the Big Sand Draw anticline, in the anticline southwest of Powder Biver, and in the dome (?) on

Wallace CriekJ.

Rock River.— The Rock River field is near the eastern border of Carbon County. No reports showing the structure of this field have been published, but the stratigraphy and structure of areas between RawUns and Medicine Bow, which lie just west of it, have been described by Veatch.

- Lost Soldier. — The Lost Soldier field is in northeastern Sweetwater County. It lies on an anticline, on which the Niobrara is exposed. A light-gravity -oil is obtained from the Wall Creek sandstone oi the Frontier formation.

Moorcroft. — In eastern and northeastern Wyoming the regional dip is southward, away from the Black Hills uplift. The rocks outcropping are indicated in the accompanying table. At several places subordinate folds have been identified on the southwarddipping monocUne, and some of these have been prospected for oil.

The Moorcroft oil field lies 12 miles north of the town of Moorcroft. Seeps are found in the Fuson shale, the Dakota sandstone, and the Grdneros formation. Prior to 1888 oil was pumped from a well and gathered from oil springs and sold in mining towns of the Black Hills. , The district contains a heavy paraffin oil and also a heavy asphaltic oiL The sandstone of the Graneros shale (Benton) is the ijaain oil-bearing bed. Nuniierous test wells have failed to reveal commercial supplies (1919).

iVeatch, a. C: Coal Fields of East-Central Carbon County, Wyoming. U. S. Geol. Survey Bull. 316, pp. 244-263, 1907.

'ZiEQLERy Victor: Popular Oil Geology, p. 94, New York, 1918.

'BARNEJir, V. H.: The Moorcroft Oil Field, Crook County, Wyoming. U. S. Geol. Survey BuU. 581-C, pp. 83-105, 1915.

Rocky Mountain Fields

Genbrauzed Section of Rocks in the Moobcboft Ou< Fieu>, Wtoiuno

(After Barnett)

System

Series

Group

Formation

Character

Thickness (Feet)

Character of Topography and Soil

s

Montana.

Fox Hills sandstone.

Friable sandstone and sandy shale.

Rolling hills and roundedridges ;8andy soil with good grass.

Pierre shale.

Dark shale with calcareous concretions.

2,000

Wide plains with shallow valleys; thin, clayey, and not very fertile soil, supporting fair growth of grass.

Colorado.

Niobrarashale.

Gray calcareous shale.

Shale slopes; limy soil.

Carlile shale.

Gray shale with oval concretions and thin sandstones.

Rolling hills with thin clay soil, mostly covered with grass.

Greenhorn f or mation.

Shale with impure concretionary limestone.

Small bare ridges.

Cretao

Granerbs shale.

Black shale with concretions.

Hard ay shale containing many fish scales (Mowry shale member).

Sandstone, oil bearins.

Black shale with small concretions.

[Wide valleys containing eztenve alluvial deposits. .

Shaly ridges, partly

1 wooded.

Valleys with clay soil and badlands..

Dakota sandstone.

Gray to buff sandstone, mostly very massive; weatners reddish brown.

60+

Plateaus, canyons, and high clifTs with rocky slopes; thin sandy soil.

Lower Cretaceous.

Fuson shale.

Shale and sandy shale with local sandstone.

Slopes below cliffs of Dakota sandstone.

Lakota sandstone.

Light-colored coarse massive sandstone.

Canyons with cliffs; thin sandy soil.

Jurassic or Cretaceous.

Morrison shale.

Masdve pale greenishgray to maroon shale with limestone nodules.

Steep slop bel ow cliffs of Lakota sandstone; poor soil.

Newcastle. — The Newcastle field is about 50 miles southeast of Moorcroft. The Graneros shale, which contains sandstone lenses, crops out in the district, and in places a heavy paraffin oil exudes fi:om the sands. Drilling had not revealed commercial suppUes of petroleum until 1920, when a heavily producing well was drilled.

Knight, W. C, and Slosson, E. ]E. : The Newcastle Oil Field. Wyoming Univ. School of Mineis Pet. Series, Bull, 5, 1902.

394 Geology Of Petroleum

Uptoa-Thomton Oil Field.— The Upton-Thornton oil field is in Weston and Crook Counties, eastern Wyoming; The rocks outcropping are of Cretaceous age and lie on the southwest flank of the Black Hills Uplift. An anticline strikes northwest throu the district, and on its crest two domes are developed. One of them lies near Upton and the other about a mile southwest of Thornton. Neither of these domes produces oil. About three* miles northwest of Thornton a small oil field is developed on a monocline that dips southwest and which lies west of the anticline on which the domes are located.

The oil has accmnulated on or near a terrace-like slope where the dip of the monocline changes (Fig. 164). The oil occurs in the sandy members of the Colorado shale, one horizon being in the Graneros, another in the Carlile shale. The oil is obtained mainly from a sand which ranges in thickness from 29 to 47 feet and is reached at depths ranging from 448 to 843 feet. The oil near Thornton is light green in color and of light gravity. Northwest of the center of the dome, in sec. 4, T. 48 N., R. 66 W., several wells have been sunk to depths between 480 and 880 feet. These yield each from 5 to 10 barrels of light oil daily.* The wells are on a structural terrace, and the productive sand crops out within half a mile of the nearest producing well.

Buck Creek. — About 20 miles north of Lusk, near the center of Niobrara Coimty,* there is a well-defined structural terrace, which Trumbull designates the Buck Creek field. The beds, which lie flat in the western part of the area, dip steeply eastward east of Buck Creek. In this region oil is said to be obtained from the Muddy sand a short distance below the Mowry.

Mule Creek. — The Mule Creek oil field is in eastern Wyoming, four miles from the South Dakota line, about 35 miles northeast of the Lande Creek field. About 10 wells sunk on an anticline tested 125 to 150 barrels of high grade oil daily in the autmnn of 1919. The oil occurs in the Dakota sandstone of Cretaceous age,

Hancock, E. T. : The Upton-Thornton Oil Field, Wyoming. U. S. GeoL Survey . 716.B, pp. 17-34, 1920.

*Hancock, E. T. : The Upton-Thomton Oil Field, Wyoming. U. S. GeoL Survey BuU. 716, p. 31, 1920.

Trumbull, L. W.: Prospective Oil Fields. Wyoming State Geologist's Office . 5, p. 8, 1913.

Rocky Mountain Fields

SBcnoN OF Rock Fobmationb in thb Upton-Thobnton Field

Syatem

Series

Group

Formation and Member

Character

Thickness (Feet)

Upper Cretaceous.

s

Piexre sliale.

Dark shale including a sone of calcareous concretions near middle and a few thin beds of bentonite. Only lower 1,200 feet to top of sone of calcareous concretions is mapped.

2,500*

O

Niobrara shale.

Chiefly liffht-yellowish to cream-coTored calcareous shale, with some impure chalk, clay, and sand.

Carlile shale.

Dark shale with thin beds of soft sandstone mainly near the base.

Greenhorn limestone.

Impiue, slabby limestone.

Cretaceous.

a

g

Dark-gray to black shale, inoludinc many large calcareous concretions, especially in the upper part.

Mowry shale member*

Hard, lightgray, sandy shales containing numerous fish scales. Bentonite beds near the top and to some extent near the base.

Dark, sandy shale grading imwardintotypioalMowry

Reddish to liht-yellow sandcarbonaceous shale.

8 to 15

Dark-gray to black shale.

Dakota sandstone.

Thin-bedded to massive hard buff sandstone.

Lower Cretaceous.

Fuson formation.

Shale and thin-bedded sandstone. ,

Lakota sandstone.

Sandstone, in part conglomeratic, with some oou beds near the base.

(?)

Morrison formation.

Tight-gray pinkish shale.

Juraaeio.

Upper Jurassic.

Sundance formation.

Light-gray to dark greenishgray and pinkish, sandy shale with a 25-ft. sandstone near the base.

Triaasio (?).

Spearfish formation.

Gypsimi and red clay beds in alternating succession. Popularly known as the "Red Beds."

Permian

Minnekahta limestone.

Light-gray to pinkish or purplish limestone.

Gkrboniferous.

Opeche formation.

Red. sandy clay, purplish at the top.

Pennsylvanian.

Minnelusa sandstone.

Light gray to buff calcareous sandstone.

Mississippian.

White, pale-buff, pinkish, and gray limestone.

398*

Geology Of Petroleum

en]

Uj

0)

which lies about 1,400 feet deep. The Minnelusa sandstone (Carboniferous) which contains oil in the Old Woman anticline 15 miles away, is expected at a depth of 2,700 feet at Mule Creek wells.

Spring Valley. — The Spring Valley field,* Uinta County, southwestern Wyoming, is an area of Mesozoic and later sedimentary rocks deformed by faulting and folding. The oil field is in the Absaroka fault zone, which is marked by reverse faulting. Numerous oil springs are found in this region, among them the Brigham Young, Carter, and White springs, which occur along a secondary fault east of the main Absaroka fault. The Aspen tunnel of the Union Pacific Railroad, which was driven through the Cretaceous Frontier formation, crossed a secondary fault in the Absaroka fault zone, and at the fault there was a considerable seep of oil. Many weUs put down m this region found some oil, but not in paying quantities. The region is complexly deformed. At Milliard the strata are overturned. Most of the oil found in the Spring Valley wells comes from sandy layers in the Aspen shale. The oil-bearing beds carry little water.

Labarge. — The Labarge field is in Lincoln Coimty, about 80 miles north of the Spring Valley field. The county is an area of faulted and folded strata of Cretaceous and Tertiary age. The dominant structural feature is the Absaroka fault zone. In the vicinity of

iHancock, E T : U. S. Geol. Survey BvU, 716-C. Press BvU, U. S. Geol. Survey No. 455, August, 1920.

*Veatch, a. C: Geography and Geology of Southwestern Wyoming. U. S. Geol. Survey Pro}, Paper 66, p. 139, 1907.

'ScHULTZ, A. R. : The Labarge Oil Field, Central Uinta County, Wyoming. U. S. Geol. Survey BvU. 340, p. 364, 1907.

Rocky Mountain Fields 397

Labarge Ridge the oil formation is the Aspen (Mowry?), a division of the Colorado that consists of shale, sandstone, and limestone. Oil is supposed to have seeped from the deep-lying Aspen under the outcropping Tertiary beds. In a sketch of this field TrumbulP shows an anticUne in the Cretaceous which includes the Aspen, overlain by the flat-lying Tertiary beds.

Big Horn Basin. — The Big Horn Basin* is a depression nearly surrounded by high mountain ranges. On the east lie the Big Horn Mountains, on the south the Owl Creek and Bridger ranges, and on the west the Shoshone Mountains (Fig. 165). The structiu-e of the northeastern part has been described by Washbume, and that of the southern part by Hewett and Lupton.

The rocks dip from the mountains toward the center of the basin, where the* older formations are deeply buried. The Big Horn Basin may be separated into two parts — an inner or central part, in which the surface rocks belonging to the Wasatch and younger formations are almost horizontal, and an outer or border part adjacent to the mountains, in which the beds older than the Wasatch are thrown into small folds. The Wasatch and yoimger beds of the central part are only locally horizontal, however, for they dip slightly toward the middle trough, which trends roughly N. 40° W.

Near the mountains there are two almost completely circular chains of anticlines and domes, one inside the other (Figs. 166, 167). The inner circle has yielded almost the entire production of the area. All of the producing folds are elongated domes, or

Trumbull, L. W. : Wyoming State Geologist's Office BvU, 6, p. 13, 1913.

'Hewett, D. F., and Lupton, C. T. : Anticlines in the Southern Part of thei Big Horn Basin, Wyoming. U. S. Geol. Survey BuU, 656, 1917.

Hintze, F. F., Jr. : The Basin and Gray Bull Oil and Gas Fields, Wyoming. Wyoming State Geologist's Office BuU. 10, 1914.

Darton, N. H.: Mineral Resources of the Big Horn Mountain Region. U. S. Geol. Survey 285, pp. 303-310, 1906.

Fisher, C. A.: Geology and Water Resources of the Big Horn Basin, Wyoming. U. S. Geol. Survey Prof. Paper 63, 1906.

Washburne, C. W. : Gas Fields of the Big Horn Basin, Wyoming. U. S. Geol. Survey BuU. 340, pp. 348-363, 1908.

Hewett, D. F. : The Shoshone River Section, Wyoming. U. S. GeoL Survey Bull 641, pp. 89-113, 1912.

ScHXJLTZ, A. R. : Geology and Geography of a Portion of Lincoln County, Wyoming. U, S, Geol. Survey BvU, $43, 1914,

Geology Of Petroleum

anticlines plunging at both ends. Their axes are rudely parallel to the axes of the mountain ranges, which almost encircle the basin. The domes and anticlines have large closures; that of the Grass Creek anticline, the most productive in the basin, is over 2,000 feet. Many of the oil-bearing folds are faulted, but moderate amounts of faulting do not seem to influence accumulation adversely in this region. For a productive region that is so much

n Miics

Fig. 165. — Sketch map showing Big Horn Basin, Wyoming.

faulted, surface indications of oil are not numerous, although oil seeps have been found on or near the Bonanza, Sherard, and Lysite Mountain anticUnes, and near the base of the Chugwater formation on the Red Spring anticline. The oil-bearing strata are all or nearly all marine. Salt water is found in many of the folds, but in some of them it is not very salty. The water below the oil on both limbs of the Grass Creek anticline is neither sulphurous nor

Rocky Mountain Fields

FOBUATIONS OF' BlO HOBM BaSIN, WTOMINa

(After Hewett and Lupton)

Ssratem

Formation

Thickness (Feet)

Character of Rocks

Quaternary.

Alluvium.

Hot-sprioc deposits. Terrace gravels.

O-fiO

Valley and flood-plain deposits along streams.

Local deposits of calcareous tufa.

Gravels and boulders washed from adjacent mountains.

Vcdcanie rook.

(?)

Andesitic tuffs and flows on west side of basin.

Tertiary.

Wasatch.

Unconlormlty -r—

Fort Union.

Unconformity

Lance.

1,300 +

Red and drab day: buff and white sandstone with gravel lenses. Man areas of badlands around border of basin.

2.000-5,600

Buff and white gritty sandstone, with drab, red, and green clay; lenses of gravel and lenticular beds of coaL

Tertiary (?).

840-1,800

Buff and drab sandstone with drab and green shale. No red shale or coal beds.

Montana.

Meeteetse.

250-1,400

Soft gray and brown shale : gray and buff sandstone and lenticular beds of coal.

Mesaverde.

1 ,120-1 ,410

Buff and white sandstone, gray and brown shale and lenticular beds of ooal near base.

Cody.

1.900-3.400

Gray, green, and black shale, with cal-

with buff sandstone at top. No persistent sharply marked beds.

Colorado.

Cretaceoiu.

Frontier.

494-48

West side: Seven or more beds of gray and buff sandstone with gray and brown shale and bentonite.

East side: Two to six or more beds of sandstone.

Mowiy.

Hard fray shale containing fish scales with lenses of gravel-bearing sandstone.

Thermopolis.

Gray to black shale with one persistent sandstone, the Muddy sand of the drillers.

Cloverly.

110-00

Two beds of massive buff sandstone separated by ray or variegated shate. Upper sand is the Greybull.

Cretaceous (7).

Morrison.

Purplish and pale greenish-ray shales with sandstones interbedded. . 1 1

Juraaslc.

Sundance.

Greenish-gray sandstouM and shales with a little limestone interbedded.

Triaasic.

Chiiffwater.

700-1,100

Red Beds: Red sandstones and shales with a thick bed of gypsum near top.

Embar.

Gray limestone, with gray and red sandy shale and gyiMum interbedded. Limestone very thin on east side of basin.

Tensleep.

Carboniferous.

lasers of limestone.

Amsden.

Red sandy shales and sandstonest with layers of limestone and chert.

Madison.

600-1,000

Gray massive limestones.

Ordovician.

Bighorn.

Siliceous gray limestone, very hard and

massive.

Cambrian.

Deadwood.

Sandstone, shale, conglomerate, and limestone.

Geology Of Petroleum

Fio. 166. — Geologie map of southern part of Big Horn Basin, Wyoming. For section along line AB, see Fig. 167. Numbers refer to descriptions in table 9n opposite pe and page following [After Hew and Luplon.)

Rocky Mountain Fields

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Cloverly. Frontier, Mowry. Do.

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Geology Of Petroleum

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Rocky Mountain Fields 403

very salty, but is somewhat alkaline. Pre- -2

sumably the surface water has entered the oil- ;g

bearing sands down the dips of the beds and -

along faults and either diluted the water that S

had been stored in the sands or swept it out.

The beds that have yielded most of the oil -g

and gas are of Cretaceous age and are parts of E

the Cloverly formation, Tliermopolis shale, "I

Mowry shale, and Frontier formation. Gas is

reported also from a sand in the Morrison .

formation on the Shoshone anticline near Cody. „

It is uncertain whether any of the beds lower J

than the Cloverly formation will prove to be .3

important sources of oil or gas. Only one well ' i;

(on the Nieber anticline, has tested, under o °

favorable structural conditions, beds higher 1

than the Cody shale, which overlies the Fron- &!

tier formation. The prospect that any of these J&

higher beds will yield important quantities of gS

either oil or gas, according to Hewett and Lup- P

ton, is uncertain, .9

The sands of the Frontier formation yield the Ji

greatest part of the oil, and the sands of the fi g

Mowry shale and the GreybuU sand yield oil as EC "S

well as most of the gas now produced in the

basin. Where synclines or beds lying flat have -g

been drilled they have struck little oil or gas or C

none. " "

In the three most productive fields in the area — the Greybull, Torchlight, and Grass Creek — the zone in the prolific sands that yields the oil extends much lower along a part of the flat basin ward limb of the fold than on the steep mountainward limb. Thus at Grass Creek thg sands are prolific at a lower altitude in the southeastern part of the field than in the southwestern or western part. As stated by Hewett and Lupton, every tested field in the Big Horn Basin which has yielded appreciable quantities of oil and gas lies toward the principal trough of

pa

Geology Of Petroleum

the basin, and every tested upfold which is separated from this trough by other folds has either yielded water and the merest traces of oil and gas or is barren. The side of the anticline or elongated dome that is more nearly flat is in general more pro-

a MILKS

Structure contours (lines of equal altitude) on top of Greybull sand. Numbers show distance above sea level. Contour interval ZOO feet

Oil well .Gas well Ory hole

Fig. 168. — Structure concur map and section of Greybull dome, Wyoming.

{After Hewett and Lupton.)

ductive than the steeply plunging side. The flatter dips are generally toward the basin, from which the accumulations came.

The Elk Basin pool, in the northern part of the oil district, is on the boundary between Wyoming and Montana. Structurally the

Rocky Mountain Fields 405

field is a dome cut by cross faults. The oil is of light gravity and comes from sandstone of the Frontier formation.

The Byron dome, which lies southeast of Elk Basin, produces light oil that is refined at Cowley, near by. The productive sands are the Frontier, Mowry, and Morrison (?).

Greybull is southeast of Byron. It produces a high-grade parafiin-base oil and much gas. The Greybull sand is the upper sand in the Cloverly formation. Gas is found in the top of the dome, and oil lower down on the west and northwest sides (Fig. 168). Its accumulation there may be due in part to the presence of water in the Greybull sand close to the gas wells on the north, east and southeast sides, the water having pushed the oil toward the west and northwest. Water can easily enter the oil and gas sand at its outcrop around the south end of Sheep Mountain, 3 to 4 miles north of the Greybull dome.

The Torchlight dome (Fig. 169), also termed the Basin dome, is only about 10 miles southeast of the Greybull dome and 2 or 3 miles east of the town of Basin. It is an elliptical upfold in the rocks trending northwest, with its broad end facing southeast. It is about 3 miles long and 2 miles wide and is separated from the Lamb anticline by a shallow syncline, a depression in the rocks 200 to 300 feet deep. Along the crest of the dome the beds lie nearly flat, dipping gently outward. On the north limb the maximum dip of the rocks (11°) is reached about a quarter of a mile away from the crest line; beyond this the beds gradually flatten to the axis of the syncline. The dips are comparatively low, averaging 3° to 4° at the northwest and southeast ends of the dome. The rocks at the surface in the center of the Torchlight dome belong to the upper part of the Frontier formation, which in this locality is a little more than 550 feet thick. A prominent sandstone (the Torchlight) of this formation encircles the central part of the dome in a line of cliffs. A thicker and more prominent sandstone, the Peay, in the lower part of the Frontier formation, is not exposed in this dome but is well shown along Big Horn River near Greybull. Directly under the Frontier formation is the Mowry shale, which contains two sands — the Kimball and Octh Louie — that yield oil. The entire formation yields some oil. Under the Mowry shale is the Thermopolis shale, about 700 feet thick; the Muddy sand, which contains a little gas in some wells, is about 300 feet above its base. Directly beneath the Thermo-

Geology Of Petroleum

polis shale is the Cleverly formation, about 125 feet thick, the top

Fig.' 169. — Contour map and cross section of Lamb anticline and Torchlight dome, Bighorn Basin, Wyoming. Numbers with symbols refer to descriptions in U. S. Geol. Survey Bull. 656. {After Lupton.)

sandstone of which is about 20 feet thick and is known as the

Rocky Mountain Fields 407

Greybull sand. In the GreybuU field this bed of sand yields nearly all the oil and gas.

The Bonanza dome is about 18 miles southeast of Torchlight. Oil seeps from a sand in the Mowry shale exposed near the crest of the dome, and the oil was used by early settlers. The Thermopolis shale is exposed on the crest. The dome has yielded little or no oil. 2

The Warm Springs dome, southwest of Bonanza, on the opposite side of the basin, yields oil.

The Grass Creek anticline,' about 28 miles northwest of Thermopolis, is the most productive fold in the Big Horn basin. It plunges at both ends, giving ample closure. In three wells oil flowed over the casing, but none of the wells were strong gushers. Although most of the wells are pumped they have a long life. The water below the oil is no salty but is said to be alkaline. The outcropping rock is the Cody shale. The sandstones of the Frontier formation which yield the oil in this anticline do not outcrop but are struck in wells at a minimum depth of 365 feet.

The contours show a relatively simple but sharp anticline broken by a few faults. The fold is unsyminetrical, with a steep limb on the southwest wide and a very gently dipping limb on the northeast side. The dips on the northeast side increase from zero at the crest line to a maximum of 34° on the outcrop of beds of the Meeteetse formation, 4 miles distant. The rim rock of Mesaverde sandstone dips from 12° to 24° along the northeast limb. On the southwest side the beds descend sharply into the adjacent syncline and dip from 50° to 60° across a wide belt. The anticline is limited on the northwest by a short syncline, west of which is the Little Grass Creek dome.

The Buffalo Basin anticline is about 10 miles northwest of the Grass Creek field. The Cody shale crops out, and gas is found in the sands of the Frontier.

The Oregon Basin field is about 20 miles northwest of the Buffalo Basin field. It produces gas from sands below the Frontier.

The Cody field is northwest of the Oregon Basin field and produces some gas and a little light oil from sands below the Frontier.

Hewett, D. p., and Lupton, C, T. ; Op, cit.f pp. 76-77. 2/dem, p. 93. Idem, p. 153.

408 Geology Of Petroleum

References for Wyoming

Barnett, V. H.: The Douglas Oil Field, Converse County, Wyoming. U. S. Geol. Survey Bull 541, pp. 49-88, 1914.

The Moorcroft Oil Field, Crook County, Wyoming. U. S.

Geol. Survey BvlL 581, pp. 83-104, 1915.

Possibilities of Oil and Gas in the Big Muddy Dome, Converse

and Natrona Counties, Wyoming. U. S. Geol. Survey Bull. 581, pp. 105- 117, 1915.

Darton, N. H.: Preliminary Report on the Geology and Underground Water Resources of the Central Great Plains. U. S. Geol. Survey Prof. Paper 32, 1905.

— Mineral Resources of the Big Horn Mountain Region, Wyoming.

U. S. Geol. Survey Bull. 285, pp. 303-310, 1906.

and SiEBENTHAL, C. E. : Geology and Mineral Resources of the

Laramie Basin, Wyoming. U. S. Geol. Survey . 364, 1909.

Fisher, C. A. : Geology and Water Resources of the Big Horn Basin, Wyoming. U. S. Geol. Survey Prof. Paper 53, pp. 1-72, 1906.

Mineral Resources of the Big Horn Basin, Wyoming. U. S.

Geol. Survey BuU. 285, pp. 311-315, 1906.

Hares, C. J.: Anticlines in Central Wyoming. U. S. Geol. Survey BvU. 641, pp. 233-279, 1917.

Hewett, D. F. : The Shoshone River Section, Wyoming. U. S. Geol. Survey BuU. 541, pp. 89-113, 1914.

and LuPTON, C. T. : Anticlines in the Southern Part of the Big

Horn Basin, Wyoming. U. S. Geol. Survey Bull. 656, 1917.

HiNTZE, F. F.: The Basin and GreybuU Oil and Gas Fields, Wyoming. Wyoming State Geologist's Office BuU. 10, 1915.

Jamison, C. E. : The Douglas Oil Fields, Converse County, Wyoming; The Muddy Creek Oil Field, Carbon County, Wyoming. Wyoming State Geologist, ser. B., BuU. 3, 1912.

Knight, W. C. : A Preliminary Report on the Artesian Basins of Wyoming. Wyoming Univ. Exper. Sta. BuU. 45, 1900.

and Slosson, E. E. : The Dutton, Rattlesnake, Oil Mountain,

and Powder River Oil Fields. Wyoming Univ. School of Mines Pet. Ser., BuU. 4, 1901.

The Newcastle Oil Field. Wyoming Univ. School of Mines

Pet. Ser., Bull. 5, 1902.

LuPTON, C. T.: Oil and Gas Near Basin, Big Horn County, Wyoming. U. S. Geol. Survey Bull. 621, pp. 157-190, 1916.

ScHULTZ, A. R. : The Labarge Oil Field, Central Uinta County, Wyoming. U. S. Geol. Survey BuU. 340, pp. 364-373, 1908.

Geology and Geography of a Portion of Lincohi County, Wyoming." U. S. Geol. Survey BuU. 543, pp. 1-141, 1914.

Tritmbull, L. W. : Light Oil Fields of Wyoming. Wyoming State Geologist's Office BuU. 12, 1916.

Prospective Oil Fields. Wyoming State Geologist's Office BiM.

6, 1913.

Rocky Mountain Fields 409

Vbatch, a. C: Geography and Geology of a Portion of Southwestern Wyoming, with Special Reference to Coal and Oil. U. S. Geol. Survey Prof. Paper 56, 1907.

Coal and Oil in Southern Uinta County, Wyoming. U. S. Geol.

Survey BuU. 285, pp. 331-335, 1906.

Coal Fields in East-Central Carbon County, Wyoming. U. S.

Oeol. Survey Bull. 316, pp. 244-260, 1907.

Washburne, C. W. : Gas Fields of the Big Horn Basin, Wyoming. U. S. Geol. Survey Bull. 340, pp. 348-363, 1908.

Wegemann, C. H. : The Salt Creek Oil Field, Natrona County, Wyoming. XJ. S. Geol. Survey BuU. 452, pp. 37-83, 1911.

The Powder River Oil Field, Wyoming. U. S: Geol. Survey

Bull. 471, pp. 56-75, 1912.

The Salt Creek Oil Field, Wyoming. U S. Geol. Survey BuU.

670, 1917.

Woodruff, E. G.: The Lander Oil Field, Fremont County, Wyoming. U. S. Geol. Survey Bull. 452, pp. 7-36, 1911.

ZiEGLER, Victor: The Pilot Butte Oil Field, Fremont County, Wyoming. Wyoming State Geologist's Office Bull, 13, p. 143, 1916.

Popular Oil Geology, New York, Wiley & Sons, 1918.

Montana

General Features. — The Cretaceous and later rocks that cover extensive areas in Wyoming are present in force also in Montana. The mountain areas are in the main anticlinal, and as a rule igneous and metamorphosed rocks form their central masses, as in Wyoming. In Montana, however, there are larger and more numerous "bodies of post-Cretaceous igneous rocks, whereas in Wyoming the larger central mountain masses were formed in general before the Cretaceous sediments were laid down, and the sedimentary rocks rest upon the eroded igneous bodies. For that reason Montana contains more numerous metalliferous veins, which are associated with the great post-Cretaceous intrusive rocks. Such veins are very sparingly developed in Wyoming. The basin areas in Montana exhibit minor folds, like the basin areas of Wyoming, especially away from the centers of the basins and around their rims. Although the rocks present and the structure are favorable for oil and gas prospecting in Montana, the production thus far is very small. Some of the sands are tight. The State has not been fully prospected, however, and there are reasons for supposing that productive oil or gas fields may yet be discovered. The structure of the Big Horn Basin, Wyoming, extends northwestward into Montana. The outcrops of Cretaceous rocks expand in central

410 Geology Op Petroleum

and northern Montana, covering broad areas between the Rocky Mountain front and the great Tertiary areas in the eastern part of the State (Fig. 170). Here and there they are raised around small uplifts of older rocks, such as the Judith Mountains, and Little Rocky Mountains, and other outlying ranges.

Although few large fields have been discovered in Montana, the Elk Basin oil pool, about 55 miles south and a little west of Billings, lies partly in Wyoming and partly in Montana. The portion of this field lying in Montana produced 44,917 barrels of oil in 1917. Commercial quantities of gas have been found very near Baker and Glendive, Dawson County. Two oil wells were brought in in Devil's Basin,' near Roundup, Montana, in 1919. One of them, the Van Dozen well, yielded a heavy black oil of 23° Baume. In

eastern Fergus County, near Mosby, on the Cat Creek dome {Fig. 171),severalwell3 were brought in in 1920 that yielded a high gravity oil. One of these was reported to yield over 1,000 barrels a day.

A little oil was found, probably in the Ellis formation, of Jurassic age, in the Woman's Pocket. The Kootenai produces the high grade oil of Cat Creek dome and is generally regarded as a

'BowEN, C. F.: Coal Discovered in a Reconnaisaance Survey Between Muaselshell and Judith, Montana. tJ. S. Oeol. Survey . 641, part 3, pp. 328-337, 1914.

Rocky Mountain Fields

possible producer in many parts of the area. The Kootenai consists of an upper and a lower sandstone member separated and overlain by shale that is generally red. It is in general about 500 feet thick and the lower sand is 30 to 40 feet thick. The upper sand is water soaked and the lower one is oil bearing.

The Colorado shale, about 1,800 feet thick, Hes above the Kootenai. It is composed of black shale with a sandstone member at its base. In north central Montana it shows oil seeps, and in Wyoming it produces oil in the Big Horn basin, but thus far (1919) has not proved productive in Montana.

Chouteau

Q

1-lHu CiMk Mniaton* t'Anow CiMk-OoiM 4-Oancai Inw ft -out Edge DomM

t-Bomeldr r-'Bnah CtMk Dodm 8-CstCMekDome 9 -ButtoB IJutta Dose lO-DtTU's Bssio

U' OouIm IS-BIgWaUDoiM 18 -Willow CvMk U-BotoOiMk

Fig. 171. — Sketch of Fergus and parts of adjoining countries, Montana, showing position of domes, oil nelds and prospects. (After Freeman.)

Stillwater Basin. — In the Upper Stillwater Basin, southwest of Billings and northwest of Red Lodge, drill holes have been sunk for oil at several places. The rocks in this area range from the coal measures of lower Montana (Upper Cretaceous) age to the Fort Union formation (Eocene). Older sedimentary formations and crystalline rocks are exposed in the Beartooth Mountains, along whose north base there is a profound fault that brings Pale-

*Freeman, O. W. : Oil Fields in Central Montana. Eng, and Min, Jour., vol. 109, pp. 936-938, 1920.

*Calvebt, W. R. : Geology of the Upper Stillwater Basin, Stillwater and Carbon Counties, Montana. U. S. Geol. Survey Bidl 641, pp. 199-214, 1917.

Geology Of Petroleum

Geological Section in Central Montana

(After Freeman")

Quaternary (Travertine, terrace gravel, alluvium, glacial drift). Tertiary (Lance, shale and sandstone, 700 to 800 feet).

Mesozoic

Cretaceous

Feet 1,100

Jurassic

Bearpaw shale

Judith River formation (sandstone and

Montana shale) 250-500

Claggett shale 700

Eagle sandstone. . . . 200-300

Gas sand at Havre

Colorado shale with thin beds of sandstone (contains gas,

possibly oil 1,800

Kootenai sandstone, coal, and shale (lower sand oil bearing) 500 ± Morrison shale and sandstone. 125 ±

Paleozoic

Carboniferous

Cambrian .

Pre-Cambrian

Ellis formation, shale and sandstone (possibly contains oil) . .

Pennsvlvania — Quadrant shale . and sandstone (oil bearing) . 100-200

Mississippian — Madison limestone 800

Siluro-Devonian limestone 300

Alternating shale and limestone 500-700

Flathead quartzite and sandstone 100

Algonkian — Belt series — black and green shale 1,000 Archean — Gneisses and schists; exposed in

Little Belt Mountains

"Freeman, O. W.: Op. cit., p. 938.

ozoic rocks into contact with Tertiary formations south of Red Lodge and with successively older strata to the west. Drilling in 1916 was done on the axis of an anticline, but the absence of oil in the rock section in commercial amounts, according to Calvert, is inconclusive, because the holes were of insufficient depth and because they were put down on the pitching end of the anticUne. The absence of water in the drill holes, however, suggests that the beds penetrated are not charged with oil higher in the anticUnal arch. If oil is present at any horizon through which the drill has passed it has accumulated at that horizon lower down on the flanks of the anticline.

In sec. 32, T. 6 S., R. 18 E., according to Calvert, there is more justification for prospecting. Indications of oil were reported in

Rocky Mountain Fields 413

several holes, and it is said that in one hole small amounts of oil were obtained. At three points near by small pools of asphalt iiccur. These pools are augmented by asphalt oozing from the ground.

ma

Chiefly volcwiie

FiQ. 172. — Geologic sketch or key map showiriR relation of Lakp Ba<!in field, Montana to major structural features of the region. (After Willie, Hancock and others.)

Lake Basin. — The Lake Basin field is northwest of Billings, in

south-central Montana, and includes portions of Sweet Grass, Stillwater, Musselshell, and Yellowstone Counties. The rocks outcropping in this region (Fig. 172} are of Cretaceous and Tertiary age. The formations exposed and those that will probably be encountered in depth are as follows:

Ueology Of Petroleum '

Rocky Mountain Fields 415

There are in the field two dominating folds — the Big Coulee- Hailstone dome and the northwest end of the Big Horn Mountain anticline. The Broadview dome is a local uplift about 7 miles southwest of Broadview.

The most striking feature of the structure of the Lake Basin field is the long, narrow belt of shearing that crosses the field from the northwest corner southeastward about 8 miles north of Billings. The most intense shearing occurred along the steeply dipping south flank of the Big Coulee-Hailstone dome and around the southeast side of the Broadview dome.

In this field surface indications of petroleum are not prominent. There seems to be no evidence of oil or gas having escaped along any of the fault planes, but it is difficult to ascertain to what extent the lower sands have been faulted. It appears possible that welldefined sandstones such as those present in most of the productive Wyoming fields are lacking in the Lake Basin field. It may be, however, that the available drill records fail to represent the true nature of the Colorado sands and that future drilling will establish the existence of sandstones under parts of the Lake Basin field similar to those underlying certain portions of the Musselshell Valley, farther north.

The Huntley field, northeast of Billings, is in Yellowstone and Bighorn Counties, Montana, just east of Lake Basin field. The rocks are of Cretaceous and later ages, are thrown into folds, and are faulted.

The Colorado formations, that are productive in Wyoming, are under cover in this region. There are no pronounced oil seeps.

Porcupine Dome. — The Porcupine Dome, Rosebud County, Montana, lies north of Forsyth on the Chicago, Milwaukee & St. Paul Railway.

The formations exposed at the surface in this area extend from the Lance formation down to the upper part of the Colorado shale.

The dominant structure of this area is that of an elongate, roughly triangular dome whose outline is indicated by the inner margin of the Judith River formation. Within that margin the

Hancock, E. T. : Geology and Oil and Gas Prospects of the Huntley Field, Montana. U. S. Geol. Survey BulL 711-G, pp. 105-148, 1920.

*BowBN, C. F. : Possibilities of Oil in the Porcupine Dome, Rosebud County, Montana. U. S. Geol. Survey Bull 621-F, pp. 61-70, 1915.

Geology Of Petholevm

Rocky Mountain Fields

Geolooic Formations Exposbd in the Pobcupine Dome, Montana

(After Bowen)

System

Group

Formation

Thickness, Feet

Character

Quaternary

Alluvial sand, gravel, and silt along Yellowstone and Muaselshell rivers and some of the smaller streams.

Tertiary (?).

'

Lance formation.

Brown, irregularly bedded sandstone, alternating with "somber" gray shale.

Montana.

B e a r p a w shale.

900-1 .000

Dark, gray shale in which occur calcareous concretions containing marine invertebrate fossils.

Cretaceous.

Judith River formation.

100-200=

Upper sandstone member, -brown to lightgray massive sandstone. Middle member, lightgray to dark-gray shale. Lower member, sandstone which weathers brown and gives rise to large, boulder-like masses. The formation is of fresh-water origin in the western part of the field and of marine origin in the eastern part.

Claggett and Colorado shales.

Dark gray to black shale; upper part highly plastic when wet, and contains fossils characteristic of the Claggett formations; lower part slightly darker in color, more fissile and less plastic when wet, and contains fossils of Colorado age.

dome has a maximum north-south diameter of about 33 miles and a maximum east-west diameter of 27 miles. Along the east and north sides of the dome the Judith River formation dips away from the axis of uplift at angles ranging from 1° to 8°, the steeper dips being on the east side.

418 Geology Of Petroleum

No oil or gas seeps are known in this region. The sandstones of the Judith River formation are not probable receptacles of oil or gas, as these sandstones are well exposed in the field and show no indications of the presence of any bituminous substance. Oil or gas, according to Bowen, may or may not occur in the sandstones at the base of the Colorado and in the underlying Kootenai (?). Elsewhere sandstones at similar stratigraphic positions are oil bearing.

In 1920 oil was foimd in wells near Mosby on an anticline west of the Porcupine dome.

Musselshell Valley. — The Musselshell Valley, about midway between Billings and Lewiston, is occupied principally by Cretaceous rocks, with subordinate exposures of Tertiary sediments and of igneous rocks. The Cretaceous rocks are folded into gentle anticlines and synclines. Although no commercial production of oil in this region has been recorded, the region is regarded by Bowen as affording favorable prospects.

The same formations that produce the oil in the Mk Basin and Big Horn Basin of Wyoming are found here. In those fields the oil comes chiefly from the Mowry and Frontier formations, and at Basin, Wyoming, oil is obtained from the Greybull sand, the upper member of the Cloverly. Sections indicate that the sands in the Colorado shale in the Musselshell Valley occupy, in a general way, the same stratigraphic position as the productive sands in the Elk and Big Horn basins.

Sandstones that would serve as suitable reservoirs for the accumulation of oil occur at several horizons. (1) Near the top of the Colorado shale there is a transition zone of thin sandstones and sandy shale beds. (2) About 1,200 feet below the top of the Colorado a thick porous sandstone, slightly conglomeratic at the top, is well developed in the western part of the field but seems to be nearly or quite absent in the eastern part. This sandstone has approximately the same stratigraphic position as some of the sandstones in the Fronlier formation. (3) About 250 to 300 feet lower in the section is another sandstone of similar character but much thinner and more distinctly conglomeratic. (4) Associated with and imderlying the Mowry shale member, in the eastern part of

BowEN, C. F. : Anticlines in a Part of the Musselshell Valley, Montana. U. S. Geol. Survey Bull. 691, pp. 185-209, 1918; The Stratigraphy of the Montana Group. U. S. Geol. Survey Prof. Paper 90, pp. 95-153, 1916.

Rocky Mountain Fields

Generalizbd Section of Geologic Formations in a Part of the Musselshell Valley, Montana (After Bowen)

System

and Series

Quaternary.

Tertiary

Group

and

Formation

Tertiary(?)

Upper Cretaceous.

Alluvium. -Unconformity- Terrace gravels.

-Unconformity- Lance formation.

Average

Thickness

(Feet)

Not determined.

B e a r p a w

shale.

a

O bi M

Os B

s

§

Judith River formation

Claggett formation.

1,000

Eagle sandstone.

Colorado shale.

Lower Cretaceous.

Kootenai formation.

250 +

Characteristics

Unconsolidated deposits along stream courses.

Terrace gravel of well-rounded pebbles.

Yellowish-brown sandstones and bu£F to gray shales with a thick, massive sandstone at base.

Dark-gray to black marine clay shale containing large calcareous concretions. Heavy band of sandy concretions near base.

An upper part, chiefly sandstone and shale, forming ridges; a middle part, chiefly light-buff to gray or white clay shale with interbedded sandstone; a lower part, included in the Judith River because of lithologio similarity, chiefly sandstone with a thick bed of massive ledge-making sandstone at the base. The sandstones become andesitic in western part of field.

In eastern part of field a dark-drab shale, comes more sandy toward the west.

It be-

Three members. Upper member moderately thick sandstones interbedded with shale; middle member shale and thin-bedded sandstones; lower member (Virgelle sandstone) thick, massive white sandstone. In western part of field lower member is thinly bedded. The sandstones become andesitio toward the west.

In eastern part of field lower 400 to 500 feet contains three conglomeratic sandstones 5 to 20 feet thick, above which is 10 to 30 feet of sandy shale which contains fish remains. This represents the Mowry shale. The probable representative of the Frontier formation is a zone of thin shaly sandstones about 30 feet thick. Farther west, the Mowry shale can not be reccnized. The lower 700 or 800 feet of the formation consists of alternate ing black fissile shale and thin sandstones. Above this zone is the Big Elk sandstone member, 200 feet or more thick. Remainder of formation chiefly shale.

Mainly sandy shale, containing concretionary sandstone in the upper part. At the top is about 50 feet of thin-bedded sandstone in which are markings resembling worm trails; at base of exposed section is a coarse sandstone.

Geology Of Petroleum

the field, are several thin, finely conglomeratic sandstones. (5) At the top of the Kootenai there is 40 to 50 feet of platy, rather fine grained sandstone in approximately the same position as the GreybuU sand of the Big Horn Basin, Wyoming. (6) Near the base of the Kootenai there is another coarse, porous sandstone of undetermined thickness.

North-central Montana. — Interest has recently been attracted to northern Montana by a large gas well brought in near Havre, which is estimated to have had an initial yield of about 10,000,000 cubic feet, but proved short-lived. The rocks of north-central Montana are sedimentary beds lying almost flat that have been

Between Highwood Mts. '"'"o 'o of well neqr Central Fers Ca and Great Falls. Kevin, Toole Co

north of. Lewistown

From Jo of well in Sweetgrass Hills district

?2'Thinly bedded ss. contains fiah aco

6' Coarse raywh. brown sandstone"

100 Rwsty beds

Dark-gray ss. 20 Impure sandstone SO'Gray sandstone

led'Shaie with massive sandstone

10'.

lO' Black sandstone

25*

Scale

100 Ft.

lo'* Gray 88.,

SO'Gray ss.

and gray ss.

ipoo

50O

fieported to contain smolt f/ow of&s

Fig. 173. — Section showing sandstones in lower part of Colorado shale, northcentral Montana. {After Stebinger.)

Stebinger, Eugene : Possibilities of Oil and Gas in North-Central Montana. U. S. Geol. Survey Bull. 641, pp. 49-91, 1917: The Montana Group of Northwestern Montana. U. S. Geol. Survey Prof. Paper 90, pp. 61-68, 1915.

Fisher, C. A.: Geology of the Great Falls Coal Field, Montana. U. S. Geol. Survey Bull. 356, 1909; Geology and Water Resources of the Great Falls Region, Montana. U. S. Geol. Survey Water-Supply Paper 221, 1909.

Pepperberg, L. J.: The Milk River Coal Field, Montana. U. S. Geol. Survey Bull. 381, pp. 82-107, 1910; The Southern Extension of the Milk River Coal Field, Chouteau County, Montana. U. S. Geol. Survey BvU. 471, pp. 359-383, 1912.

Bo wen, C. F. : The Cleveland Coal Field, Blaine County, Montana; The Big Sandy Coal Field, Chouteau County, Montana. U. S. Geol. Survey Bull. 541, pp. 338-378, 1914.

Rocky Mountain Fields 421

intruded by igneous rocks and uplifted in isolated mountain groups. Faults are numerous. In the plains surrounding the Bearpaw Mountains for 30 to 40 miles on all sides there are many folds and faults in the Cretaceous rocks. These are irregular in their trend and distribution. The faulting is probably related to the igneous intrusions in the Bearpaw Mountains. The faults are all of the thrust type, older formations having been carried upward beside younger rocks that lie for the most part undisturbed. Some of these faults are about 12 miles long.

The strong flow of gas encountered at Havre, as stated by Stebinger, comes from the Eagle sandstone. The gas produced at Medicine Hat, in Alberta, according to some investigators, is found at the same horizon. Sections of the Colorado shale are shown on Fig. 173.

As shown by the tables given above differences between the geologic sections of the eastern and western parts of the region occur in the Montana group in the interval between the Virgelle sandstone and the Bearpaw shale. This is due to the fact that the marine invasion during which the Claggett shale was deposited in the east did not extend westward beyond the 112th meridian.

Birch Creek-Sim River Area. — The Birch Creek-Sun River area in northwestern Montana, lies adjacent to the front range of the Rocky Mountains, between Great Falls and Kalispell. The Cretaceous formations which have yielded oil and gas in Wyoming, Colorado, and at Medicine Hat, Alberta, are present in this area, where they are thrown into folds along axes parallel to the front range. Some wells have yielded gas, but no oil field has been developed. The section is stated below.

Blackfeet Reservation. — The Colorado shale and Kootenai formations are present also in the Blackfeet Reservation, where locally they are folded and faulted (Fig. 174). The Colorado and Bearpaw shales are of marine origin and were laid down in separate

Stebinger, Eugene: Oil and Gas Geology of the Birch Creek-Sun River Area, Northwestern Montana. U. S. Geol. Survey BvU. 691, pp. 149-184,

Stebinger, Eugene: Anticlines in the BlacMeet Indian Reservation, Montana. U. S. Geol. Survey Bull. 641, pp. 281-305, 1917; Possibilities of Oil and Gas in North-Central Montana. U. S. Geol. Survey BuU. 641, pp. 49-91, 1916; Geology and Coal Resources of Northern Teton County, Montana. U. S. Geol. Survey Bull. 621, pp. 117-156, 1916.

Geology Of Petroleum

Formations Exposed in the Plains of North-Central Montana East

OF the 112th Meridian

(After Stebinger)

Syttom

Series

Group and Formation

Thickness (Feet)

Character

Recent.

Alluvium.

Silt, sand, and gravel alone flood plains of larger streams.

Quaternary.

Pleistocene.

Glacial drift.

Q-200

Boulder clay, gravel, and lake silt and clay. Contains bouldera snd cobbles of granite, gneiss, Quartsite, etc., transported from the northeast.

Tftrtiary.

Eocene.

Fort Union formation.

Clay shale, sandstone, and coal beds. Present only in small areas. Poorly exposed.

Tfirtiary (7).

Eocene (7).

Lance formation.

Alternating gray clay shale and sandstone with irregular coal beds. Present in relatively small areas only.

Upper Cretaceous.

s

o o

Bearpaw shale.

Dark-gray clay shale with a few limestone concretions. Contains mair marine shells. Forms a subdued, rounded and gumbo soil.

Judith River formation.

Lif ht-gray clay and day shale with irregular beds of gray or brown sandstone, and'coal beds. Contains many oyster and other shells besides fossil bones.

Claggett shale.

Like the Bearpaw in character of rocks and fossils, except for the occurrence of sandy beds near the top.

Cretaceoiu.

Eagle sandstone with Virgelle sand stone member at base.

Upper part grav clav shale and sandstone with coaly shale and thin coal. Lower part white to bu£F thick-bedded, massive sandstone, Virgelle sandstone member. Contains gas in the Havre district.

Colorado shale.

1 ,600-1 ,700

Bluiflh-gray to black shale with a few limestone concretions. Contains many marine shells. Includes three or four sandy beds 5 to 70 feet thick in lower 800 feet Probably contains gas and oil in some localities of favorable structure.

Lower Cretaceous.

Kootenai formation.

Red clayey shale and irregular gray sandstone with a few thin beds of limestone. Contains coal near the base and fossil plant remains of fresh-water oriffin. Probably contains gss and oil in some localities of favorable structure.

Rocky Mountain Fields

FoBif ATioNB Exposed in the Plains of North-Central Montana West

OF the 112th Meridian (After Stebinger)

Bystem

Series

Group and Formation

Thickness (Feet)

Character

Recent.

Alluvium.

Silt, sand and gravel along flood plains of larger streams.

Quaternary.

Pleistocene.

Glacial drift.

Boulder clay, gravel, and lake silt and clay. Contains boulders and cobbles of granite, gneiss, quartzite, etc., transported from the northeast.

Upper Cretaceous.

a

Bearpaw shale.

Dark-gray clay shale with a few limestone concretions. Contains many marine shells. Forms a subdued, rounded topography.

Two Medicine formation.

1 ,900-2 ,100

Gray to greenish-gray clay and soft, irregular sandstone, which is most abundant in the lower 250 feet. In places thin beds of red clay and nodular limestone. Contains an abundant reptilian fauna of Judith River types, besides leaves and shells. Contains coal beds near the base and at the top.

Cretaceous.

Virgelle sandstone.

Gray to bufif coarse-grained, much cross-bedded massive sandstone, with many ferruginous concretions in upper half. In lower half slabby gray sandstone, becoming shaly toward the base.

Colorado shale.

1 ,600-1 ,760

Bluish-gray to black shale with a few limestone concretions. Contains many marine shells. Includes three or four sandy beds 5 to 70 feet thick in lower 800 feet. Probably contains gas and oil in some of the areas of favorable structure.

Lower Cretaceous.

Kootenai formation.

Shale, red in upper part, but remainder grayish to black. Contains irregular sandy beds up to 100 feet thick. Fresh water. Probably contains gas and oil in some of the areas of favorable structure.

Geology Of Petroleum

Formations Exposed in the Birch Creek-Sun River Area, Montana

(After Stebinger)

System

Quaterzuiry .

Tertiary.

Tertiary (?)

Series

Recent.

Pleistocene.

Pleistocene and late Tertiary.

Eocene (?).

Group and Formation

Alluvium.

Thickness (Feet)

Glacial drift.

Terrace gravels.

St. Mary River f or mation.

Cretaceous.

Jurassic.

Carboniferous.

Upper Cretaceous.

Lower Cretaceous.

Upper Jurassic.