GIFT F Mrs. W. Barstow - PRACTICAL OIL GEOLOGY McGraw-Hill BookCompatiy Electrical World The Engineering and Mining Journal Engineering Record Engineering News Railway Age Gazette American Machinist Signal Engineer American Engineer Electric Railway Journal Coal Age Metallurgical and Chemical Engineering Power PRACTICAL OIL GEOLOGY THE APPLICATION OF GEOLOGY TO OIL FIELD PROBLEMS BY DORSEY HAGER PETROLEUM GEOLOGIST AND ENGINEEB SECOND EDITION THOROUGHLY REVISED AND ENLARGED SECOND IMPRESSION McGRAW-HILL BOOK COMPANY, INC, 239 WEST 39TH STREET. NEW YORK LONDON: HILL PUBLISHING CO., LTD. 6 & 8 BOUVERIE ST., E.G. 1916 COPYRIGHT 1915, 1916, BY THE McGRAW-HlLL B.OC/5 CpiVlipA.NY, INC. THE MAPLE. PRESS* YORK. PA Go tbc PRACTICAL OIL MAN OF AMERICA, WITH THE HOPE THAT THIS BOOK WILL BRING HIM TO A BETTER UNDER- STANDING OF THE RELATION OF THE GEOLOGIST TO THE PETROLEUM INDUSTRY M100495 PREFACE TO SECOND EDITION In making a revision of the first edition the author wishes especially to thank Messrs. Johnson and Huntley of Pittsburgh, and Fred Pack on the United States Geological Survey, for their published criticisms of the first edition of " Practical Oil Geology." He also wishes to thank his many friends and fellow geologists and engineers, especially Mowry Bates and J. W. Lewis of Tulsa, for their suggestions. The industry is so extensive and the work of the geologist is so broad that the writer feels he has but touched on the many uses of geology in oil-field practice, but he hopes the book will prove useful. Certainly it has already more than fulfilled the writer's expectations for which he is deeply appreciative to the reading public. DORSET HAGER. TULSA, OKLA. November, 1916. vii PREFACE TO FIRST EDITION In the preparation of this book the author aimed to furnish the oil man with a clear, concise, and practical work on the occurrence of oil, and its geology. There are several works on petroleum but none of them is in handbook form. Three of the works are by English authors who give the practice of the East Indian and the Russian oil fields rather than that of America. However the elements of oil-field geology are the same the world over, though the best chances for study are afforded by develop- ments in America. It seemed more than fitting, therefore, that American oil men should have a book treating more particularly of American methods. As the author has gained his experience in these fields it necessarily follows that he gives the Ameri- can viewpoint, which will perhaps be a just basis for criticism by those who have had a world-wide experience. The author has, however, drawn the data for this book from European as well as American sources and hopes thus somewhat to overcome a natural bias. The material in this book is derived from the following sources : (1) The standard text books on general geology such as those by Geikie, Le Conte, Chamberlin and Salisbury, and Kemp. (2) The bulletins of the U. S. Geological Survey, the technical papers of the U. S. Bureau of Mines and the bulletins of the California, Oklahoma, Illinois, Louisiana, Pennsylvania and Ohio geological surveys. (3) The articles appearing in the numerous technical journals on mining and on oil, especially papers by Lakes, Clapp, Gordon Sur, Lee Hager, Breger, Arnold, Garfias, Dumble and others. (4) The following English books: "Petroleum Mining" by A. Beeby Thompson, "Petroleum and Its Sources" by Sir Bover- ton Redwood, and "Oil Finding" by E. H. Cunningham Craig. ix x PREFACE (5) The catalogues of several oil-well supply companies. The author is also greatly indebted to his good friends among the operators and drillers for many valuable suggestions, and for their assistance in helping him to obtain facts. Thanks are also given to Messrs. M. J. Munn, J. H. Jenkins, Fohs and Gardner, R. A. Conkling, E. D. Bloesch, Frank But- tram, E. Thomas, Valerius, McNutt and Hughes, and A. T. Patrick for their kindness in affording suggestions and additions to make the work more complete. Special recognition is due to H. Foster Bain, and to Leon Pep- perberg for their criticisms and suggestions, and to F. J. Basedow of Adelaide, Australia, for his assistance in correcting manuscript. As is the case in all sciences, there is much valuable material which it is difficult to trace and to credit to the originators. The author has made free use of this knowledge, for the facts it presents are among the most valuable we possess. DORSET HAGER. TULSA, OKLA. April, 1915. CONTENTS PAGE PREFACE TO SECOND EDITION vii FOREWORD , xiii CHAPTER I. Petroleum Its Origin and Accumulation 1 II. Petroleum Physical and Chemical Properties 14 III. Stratigraphy 30 IV. Structural Geology 48 V. Prospecting and Mapping 69 VI. Locating Drill-Hole Sites 94 VII. Factors in Oil- Well Drilling 108 VIII. Factors in Oil Production 132 IX. Water, the Enemy of the Petroleum Industry 151 X. Natural Gas 165 XI. Cautions 174 INDEX .... 175 XI FOREWORD Oil Geology Applied Common Sense There is at present a rather vague idea in the minds of many men as to just what constitutes an oil geologist. Some people associate him with the " crooked stick" or " peach tree twig" men, others think he uses some hocus-pocus, and as yet com- paratively few of the operators see the geologist as a clean-cut, clear-thinking engineer, who is just as much an expert in his line as is the driller or railroad surveyor. The geologist simply uses engineering methods in arriving at results. Engineering instruments such as transits, levels, barom- eters, alidades and plane tables are employed, all of which re- quire a mind trained in mathematics for their accurate use. The pick of the geologist, the test-tube and the chloroform bottle are also his working tools. Added to the above instruments, in fact of primary importance, is a mind trained in the reading of surface forms (topography) , a knowledge of the ages of forma- tions and their means of identification (stratigraphy), a knowl- edge of the various folded structures that are important as oil reservoirs, and above all, the ability to recognize such folds in the field. By studying rock exposure at the surface, by using drill hole records, either of water or oil tests, by readings in mines, etc., the geologist arrives at his conclusions. Of course where all exposures are covered up, and no well records exist, the geologist is "up a stump," and can only say, "I do not know." The geologist knows from the history of proven oil fields that the surface folding is generally an index to underground condi- tions. Enough holes "have been drilled, enough well logs have been plotted to prove this very important point, and it is upon xui xiv FOREWORD this fact that the science of oil geology is based. Recognition of the fact that underground folding is reflected at the surface and that such surface folding can generally be seen meant the beginning of a new era for the oil man. The work of the oil geologist really simplifies itself into the problem of finding folds. When he has found this folding, then he has a basis upon which to work. The following points must be emphasized : First, That all folds do not carry oil ; second, a geologist cannot tell whether a fold will carry oil, unless wells are already drilled upon it. A geologist does know, however, that the majority of folds, within certain defined limits, do carry oil, and he can reason from this that the chances are in favor of a well-defined fold being productive, if it occurs within certain boundaries. In the last few years sand conditions were found to play an important part in oil pools, though not as important as folding. Also many of the largest wells in the world are on faults and not connected in any way with folding. The work of the geologist does not end with outlining pro- spective oil lands. His province extends into the fiejd of drilling and of actual oil-field development. To limit geology to pro- spective territory alone is a great loss, for as one will find from the following pages, there is a wide and varied application of geology to the needs of the oil men in nearly every phase of oil- field work. PRACTICAL OIL GEOLOGY CHAPTER I PETROLEUM ITS ORIGIN AND ACCUMULATION Much has been written about the conditions under which oil is found in nature (the structure favorable for the accumulation of petroleum, the age of the formations in which oil occurs, and the technology of drilling, producing, and marketing petroleum), but as yet little positive knowledge regarding the origin of oil has appeared in print although the subject has been discussed very fully from a theoretical viewpoint by many geologists, chem- ists and engineers. Some of the many theories are discussed below. CLASSIFICATION OF THEORIES Theories pertaining to the origin of petroleum may be classified under three main divisions as follows: (A) Inorganic theories; (B) Organic theories; and (C) Combi- nations of Inorganic and Organic theories. Inorganic Theories. By inorganic is meant any chemical re- actions that take place without the aid of living organisms. There are three principal inorganic theories: (1) The carbide theory; (2) the limestone, gypsum, and hot water theory; and (3) the volcanic theory. 1. The carbide theory is based upon the fact that in the chemical laboratory carbides of calcium, iron, and several other elements give hydrocarbon products when in contact with water. It is assumed that great quantities of calcium, aluminum, iron and other similar carbides exist deep underground and that the action 1 2 PRACTICAL OIL GEOLOGY of hot water upon these carbides forms liquid and gaseous hydro- carbon .compounds, .that rise upward through fissures and other vents in the .earth, and, collect in the sedimentary beds above. This theory Jias been strongly supported by some able chemists but it Is not Advocated by .many geologists. 2. The limestone, gypsum, and hot water theory is advocated by some writers. According to this theory the action of heated water upon limestone (CaCO 3 ) and gypsum (CaSO 4 ), which in nature are closely associated, give as products the constituents of petroleum. The exact chemical processes have not been fully explained, but it is certain that limestone, gypsum and water contain all the necessary elements for the production of petro- leum. Under certain conditions of heat and pressure, it is not impossible that oil may be formed as thus postulated. 3. The volcanic theory is based upon the fact that gases given off from some volcanoes carry small percentages of hydrocarbons. These gases are supposedly of deep-seated origin, and carry the products of chemical reactions that occur in the earth. It is assumed that the gases are condensed before reaching the surface by coming in contact with cooler formations near the surface and thus form petroleum. As a laboratory theory the volcanic idea is plausible but it by no means explains most of the occur- rences of oil as seen by the field geologist. Organic Theories. By organic is meant any chemical process that takes place by assistance of living organisms such as bacteria, decomposing vegetation, or animal matter. Some scientists assert that oil is of animal origin, others that it comes from vege- table matter. There have been numerous discussions as to which is the more likely source. A compromise view asserts that petro- leum may come from either source alone, or from a combination of the two. It has been claimed that oils having an asphaltic base are derived from animal matter and that oils with a paraffine base are derived from vegetable matter. Again it is boldly stated that all oils are derived from the same material but that the dif- ferences are due to capillary division, differences in the heat and the pressure to which the oil has been subjected, to migration, etc. PETROLEUM 3 There are three organic theories as follows: (1) Animal theo- ries; (2) vegetal theories; and (3) combinations of animal and vegetal theories. In discussing the following theories the source of the material is alone considered. The subject of the derivation of petroleum from organic matter is treated in another place. 1. ANIMAL THEORIES. One theory explains that oil is derived from the decomposition of the bodies of marine animals such as fish, oysters, scallops, mollusks, and corals. Some bays and coasts literally teem with marine life at present, and it is assumed that in past ages marine life was just as plentiful, as is evidenced by the great quantities of fossils that are found today. The death of such animals and their subsequent burial in the marine sedi- ments gave material sufficient for the formation of oil. According to another theory, microscopic organisms called foramim'fera, which are today found in great quantities in some places along sea coasts, furnished the material for oil. These small organisms were certainly existent in great quantities in past ages. The microscope shows that beds many hundreds of feet thick are in large part formed of these organisms. 2. VEGETAL THEORIES. The vegetable theories may be classi- fied under the following heads : (a) The sea-weed theory; (6) the land-plant theory; (c) the diatom theory; and (d) the coal theory. (a) The sea-weed theory also has received much support. The great kelp beds that line some sea coasts, notably the Pacific Ocean and the Sargossa sea lend strength to this theory. Cer- tainly there is material enough along the coasts to produce a tremendous quantity of oil if properly distilled. Supposing that in the past ages as large quantities of material existed, and were buried in sediments, one has a basis for a strong theory. (6) The land-plant theory is based upon the occurrence of great quantities of plants found in land-locked embayments, in swamps, and in low marshes and lake beds. It has been clearly established that coal is formed from plants that grew in great swamps, and it is assumed that similar beds of material under different condi- tions of heat and pressure gave rise to petroleum instead of to 4 PRACTICAL OIL GEOLOGY coal. Certainly plants have all the constituents necessary to form petroleum so that such a theory is not at all unreasonable. (c) The diatom theory, especially advocated by California geolo- gists, is based upon the study of the microscopic plants that are plentiful in many parts of the seas and oceans. Many carbona- ceous shales, of great age geologically, contain large quantities of these minute organisms. The presence of petroleum in these diatomaceous shales is so general that many geologists believe the oil originated in the shales. It of course could only come from the microscopic organisms. (d) The coal theory is based upon the fact that lignitic and bitu- minous coals when distilled in the laboratory yield hydrocarbons similar to those in petroleum. It is thought that similar results are obtained in nature by distilling great masses of coal under proper conditions of heat and of pressure. The presence of coal in many oil fields lends support to this view but like all other theories nothing definite has been established. COMBINATION OF ANIMAL AND VEGETAL THEORIES. In some cases one finds the remains of animal and vegetable material in the same bed or stratum. It is very likely where such has been the case that petroleum has been derived from both sources. This view at least reconciles the animal and the vegetable theories, and in no way conflicts with known facts. Formation of Oil from Organic Material. The formation of petroleum from either animal or vegetable matter is considered to be as follows: 1. The organic matter is first laid down in clays and sands which have been deposited under water along sea coasts, in swamps, bays, or in lakes. 2. Other beds of material are deposited upon those carrying the organic matter, until a thick covering is formed. 3. The water and the overlying sediments protect the organic matter from rapid destruction by oxidation, and especially where the water is salt, it acts as a pickling brine. 4. In time the pressure of the overlying beds, and the action of heat, which is supposedly generated by the pressure of the over- PETROLEUM 5 lying sediments or by the action of plutonic masses of rock which have been intruded into the sediments, causes a distillation of the organic matter to form petroleum products which are later ac- cumulated into so-called " pools" or fields of oil. Combination of Organic and Inorganic Theories. Several theories combining the organic and the inorganic ideas have been offered by scientific men. The principal idea of all these theories is that gases from deep-lying igneous masses pass upward through fissures or vents in the earth's surface, and coming in contact with sediments containing organic matter form hydrocarbon products. There is little positive evidence for such theories ex- cept the presence of volcanic intrusions in a few oil fields. So far as known the organic theories seem the most reasonable and by far the most popular with scientific men. THE ACCUMULATION OF PETROLEUM INTO COMMERCIAL DEPOSITS The origin of oil is one problem, its accumulation into economic deposits a-n entirely different one. More is known about the accumulation of oil than about its origin. The following facts are important to bear in mind as in them one finds the key to many other valuable points of applied geology as related to petroleum. 1. Commercial oil and gas deposits occur in the higher parts of folds or wrinkles of the earth's surface called anticlines, domes, monoclines, etc. 2. Water is always found in the same stratum as the oil but in the lower part of the fold. 3. All commercial deposits so far have occurred in sedimentary or water-laid deposits such as sands, sandstones, conglomerates, shales, and limestones. 4. All oil and gas deposits, so far as known, are capped or covered by practically impervious beds of shale, sandstone, or limestone; also such deposits are underlaid by impervious beds. The discussion of these points is given under the following 6 PRACTICAL OIL GEOLOGY headings: (1) The anticlinal theory; (2) water and compression in accumulation; (3) capillarity; (4) reservoirs for petroleum; and (5) impervious beds capping and underlying the oil and gas deposits. The Anticlinal Theory. Anticline is the name given to the type of fold that is arched as shown in Fig. 1. Further reference is made to this type of fold in Chapter III. As the anticline is the most common form of fold found in the oil fields the theory of oil accumulations in folds was given the name anticlinal theory, although several other types of folds also act as oil reservoirs. Originally the sedimentary strata were laid down along sea coasts, in swamps, lakes, etc., as flat or horizontal beds. Suppose a large flat bed of sand, sandstone, conglomerate, shale, or lime- stone, carrying oil, gas, and water throughout it, to lie buried FIG. 1. Illustration of ideal anticlinal conditions. 1 under a mass of sediments which are impervious or nearly so; suppose also that this stratum is underlaid by impervious beds. Conditions such as assumed above are common along many sea coasts, in bays, and in gulf regions. In such a flat stratum it is found that the gas and oil will rest upon the top of the water due to the differences in specific gravity, gas and oil being lighter than water. In drilling through such a flat stratum the drill will encounter first a layer of gas, then a layer of oil and last a layer of water. However, in such flat strata oil will not be found in pay- ing quantities. To obtain commercial production another con- dition is essential. There must be a sufficient quantity of oil and gas to pay for its extraction, and such accumulations are found 1 For symbols used in this book, see Fig. 53, p. 89. PETROLEUM 7 where the flat strata have been thrown into arches or folds like that shown in Fig. 1. As will be noticed in studying Fig. 1, the same stratified or layer-like relations of the gas, oil and water occur as they would in perfectly horizontal beds. At the top of the arch or anticline is gas, below the gas is oil, and at the base of the fold is the water. This is the theoretical condition and is closely approximated in nature. Under certain conditions, how- ever, oil and gas both occur at the top of the arch, and under most conditions there is more or less gas in the oil on the flanks or sides of the structure. The above practically covers the anticlinal theory. Water and Compression in Oil Accumulations. In discussing the anticlinal theory one notices that the water was not assumed to be under pressure, but that the oil merely floated upon the top of the water due to differences in specific gravities, much the same as a cork floats upon water. The water occupies the lower parts of the folds because of its tendency to seek its level, a well- recognized truism. Normally under such conditions water occurs in the basins or depressions called synclines, the opposite of anticlines. Suppose 2 however, that there are several parallel anticlines or several domes on one anticline (see Fig. 42, Chapter V) . The lower arches are under the hydraulic pressure of the oil and the water in the higher arches. In such a case water will occupy the lower anticlines wherever the hydraulic pressure is great enough to drive the oil higher on the slope. Note that the lowest anticline carries no oil. The oil at the top of the struc- ture is not under pressure to any appreciable extent. In the above theory the water is not static or stationary, but is meteoric or rain water, which enters the outcropping sands, and works its way downward into the oil stratum. Also the movement of the water may be due to the rising or falling of the whole land mass. Thus a rising region would result in lowering the water level, and a sinking region would result in raising the water level. Where faults or where unconformities occur (see Chapters II, III and IV), water by driving oil from the lower sands will force it to enter strata above. Such traveling of oil is called migration 8 PRACTICAL OIL GEOLOGY which, however, is not dependent alone upon water pressures. Other factors such as compression discussed below, and capillarity discussed under specific gravity, also assist in migration of the oil from one formation to another. The part that compression plays in oil accumulation would seem to merit more careful atten- tion than has heretofore been accorded the subject. Many shales are saturated with petroleum. If these shales were under suf- ficiently great pressure the oil would be forced from them. Tremendous pressures are set up by earth folding. Such being the case it is not at all unlikely that the shales in the tops and at the bottoms of the folds may be so compressed that part of their petroleum content would be squeezed out of the shale body. If porous sands or sandstones are above or below the shale, the oil would be forced to migrate into the porous beds. Sand and sand- stones are generally more porous than shales and they form better reservoirs than do the shales. One of the important features of accumulation is the porosity of the beds at the top of the fold. If the beds at the top of the fold are not porous, due either to their being hard compact shales or sandstones little or no accumulation will take place. CAPILLARITY (After WASHBURNE) "Extract from Washburne Letter" "The only matter which I consider as practically proven by my study of the geophysics of petroleum is the control of capillarity upon the distribution of gas, oil, and water within the rocks. Since water has about 50 per cent, higher surface tension than oil, it tends to be drawn into the finest capillaries with half again as much force as that drawing oil into the fine openings. Every slight movement of the various fluids in the rocks tends to move water from sandstone into shale with greater ease than the reverse tendency from shale into sandstone. Likewise, it tends to move gas from shale into sandstone with greater ease than from sandstone into shale. The net result of this tendency, which has operated continuously since the formation of the strata, is to cause the concentration of gas and oil into coarse spaces of rocks, that is, in fis- sures or sandstone layers in shale, in conglomeratic or other coarse layers in sandstone, etc., leaving the water within the shale. I believe that PETROLEUM ' 9 this exchange of gas and water between sandstone layers and shale is one of the causes of the apparent dryness of the deep sands of the Appala- chian and Mid-continent oil fields. These sands were originally full of water, but in the course of geologic time this water has been exchanged for nitrogen, methane, and carbon-dioxid of the adjacent shales through the operation of capillary forces." Reservoirs for Petroleum. As shown above, the higher parts of folds act as great collecting reservoirs for oil. A study of the strata making up such reservoirs will prove of value. The best reservoirs for oil are coarse sands, conglomerates, and porous dolomitic limestones. (See Chapter III for definitions.) Sand- stones and shales often carry oil, but they are not the most favor- able for reservoirs, as in most sandstones the cementing material binding the sand grains together fills the pores so that the rock can hold only a small quantity of fluid. Shales also have very fine pores and hold only small quantities of oil, except where the shales have been broken into fragments due to intense crushing as is the case with some of the California shales, especially the silicified Monterey shales at Santa Maria. y The percentage of voids in the various kinds of strata varies considerably. Sands may contain from 15 to 25 per cent, voids; sandstones, 5 to 15 per cent, voids; conglomerates may contain as high as 30 per cent, voids; shales, from 2 to 10 per cent., and some dolomitic limestones are reported to contain as high as 35 per cent, voids. The factors above are so variable that one must not take the material in one field to be a criterion or measure of material in other fields. The following discussions on the quantity of oil in the sands, saturation, and drainage areas are all interesting and pertinent to the above discussion on voids. QUANTITY OF OIL IN SANDS. Many people think of lakes of oil lying underground. Such is not the case, by any means. It is entirely unnecessary to call such a theory into use to explain the oil reservoirs. The small voids in the sands afford plenty of space in which oil may accumulate. Some sands contain 20 per cent, voids. If these voids were full of oil, each 100 cu. ft. of sand would contain 20 cu. ft. of oil. A bed 100 ft. thick and covering an acre 10 PRACTICAL OIL GEOLOGY of land would then contain the following number of barrels of oil (42 gallons per barrel 7.5 gallons per cu. ft.) : 43,560 X 7.5 X 20 - = loOjOoo barrels. SATURATION OF OIL SANDS. By oil saturation is meant the percentage of oil present by volume in a cubic foot of oil sand. If the voids are 20 per cent., and the sand is filled with petro- leum, then the saturation is 20 per cent . l However, this method is only a rough approximation, as the amount of oil that a formation holds depends not only upon the porosity but upon the tempera- tures of the earth, the hydrostatic and the rock pressures. Only when all these factors are known can one obtain an accurate idea of the saturation. The U. S. Government in its estimates takes 10 per cent, as the saturation. Other estimates allow 1 gallon of oil to each cubic foot of sand (13.3 per cent.), or approximately 1000 barrels per acre-foot. By 10 per cent, saturation is not, however, meant that 10 per cent, of the oil is recoverable. The amount of recov- erable oil may only be 50 per cent, of the saturation or it may be as high as 75 per cent, varying with the porosity of the sand, gas pressure, etc. This will be discussed in Chapter VII. As one can readily appreciate, it is entirely unnecessary to assume lakes to account for the oil below the ground. In some places where the sands are 200 to 300 ft. thick enormous quanti- ties of petroleum are found; in others where the beds are but 10 ft. thick a correspondingly less quantity of oil is found, though this holds true only under certain conditions. A sand 100 ft. thick fully saturated with oil will produce more 011 than one only 10 ft. thick, provided, of course, the size of sand grain and per cent, of saturation are the same, and the gas pres- sure and dips are constant in both cases. Some thin sands have been very rich producers where coarse grained, producing for a time much larger quantities of oil than thicker beds which were finer grained. 1 Some scientists call the complete saturation 100%. If but 10% of the voids of the sand were filled the saturation would be 50%. PETROLEUM 11 Porous beds under heavy gas pressures give up their oil very rapidly. A thin bed of sand or limestone which is of coarse tex- ture may then be expected to have a short life compared with thick beds of finer grained material. The longevity of a well does not determine its productivity, as one well may produce in one month as much oil as others could produce in a lifetime of 15 or 20 years. The great gushers like the Lucas gusher of Spindle Top, Texas, and the Lakeview gusher of California are examples of great productivity. Such wells produced phenomenally for comparatively short periods of time, but soon exhausted themselves. DRAINAGE AREAS. It has been explained above how oil accumulates and some idea was given as to the quantities in oil strata. In conclusion it is well to touch on the size of the areas from which the oil collects. Drainage area is rather a misnomer as oil does not generally travel downward, but is displaced by water and thus rests upon it. However, the term expresses the same idea as drainage and will be used here to mean that area from which the oil has collected. NaturaDy the size of folds varies greatly. Such being the case it follows that the larger the fold, the more oil it should hold, other conditions being equal. The measurement of a fold is not a difficult matter once the basins or depressions are deter- mined. If an anticline is 25 miles long and 10 miles wide, the drainage area is not 25 X 10, or 250 square miles, but will be greater, depending upon the shape of the fold. A fold shaped like that in Fig. 10a would not cover as large an area as the fold in 106 or in lOc (all shown in Chapter III), if the folds were flat- tened out. A few folds measured by the writer had relative areas of 300, 80, 5, and J square miles. The large folds give large acreages of available oil land, while the smallest fold would not pay to prospect. It must not be thought that all of the area carries oil. The proportion of oil land in average oil-field drain- age areas varies from 1 to 20 per cent, of the total drainage area; however, 5 per cent, would be a large proportion for most oil fields. The areas given above on a 5 per cent, basis would 12 PRACTICAL OIL GEOLOGY furnish available acreages of 9600, 2560, 128 and 4 acres re- spectively. One cannot, however, figure on such an average for the true areas were approximately 5000, 500 and 100 acres re- spectively. The smaller area was not tested. From these few notes one can appreciate that each field is a problem by itself. Impervious Beds, Capping and Underlying the Oil Strata. Oil strata are overlaid or capped, and underlaid by strata prac- tically impervious to oil. These beds may consist of compact shales, hard, closely cemented sandstones, and compact limestones. In all cases the overlying strata must be tight enough to effec- tually seal in the oil. Where the strata have been eroded leaving exposed sands, the more volatile oils will escape unless asphaltic or paraffine deposits coat the faces of the strata, and act as seals to keep in the remaining oil. However, as explained under "Effects of Migration," there are conditions where oil may work its way upward through the overlying beds. Also were it not for the compact, overlying beds, water would work its way downward from the surface of the earth and flood the oil strata. It is just as essential to have a compact underlying bed of material to retain the oil as it is to have a capping. If it were not for such beds the oil would gradually escape downward from the stratum in which it originally occurred. It seems highly probable that such has been the case in some instances. How- ever, water in the lower beds would stop migration, for petroleum will not escape through a rock saturated with water. This applies whether or not the water stratum is above or below the oil stratum. In such saturated rocks the water is held by friction and capillary attraction to the small grains of sediment and the oil has not sufficient pressure to overcome these factors. If for any reason the rocks below lose their water the oil will under some conditions travel downward. PETROLEUM 13 DYNAMIC HEAT GENERATED BY INTENSE FOLDING AND ITS EFFECT ON OIL FIELDS A theory advanced by David White seems to be applicable in the oil-fields of the Appalachian and Mid-Continent regions. Briefly stated, the theory is that as one approaches the lines or centers of intense folding the heat generated by the intense folding has been sufficient to volatilize the hydrocarbons in the oil and change them to a more stable gaseous form. Metamorphism has affected the coals to the extent that the closer the coal is found to the centers of lines of uplift the more anthracitic the coal becomes, i.e., contains more fixed carbon and less volatile water. This is particularly the case in the Appalachian fields and holds without any question in the southeastern Oklahoma and Arkansas gas fields. Vast quantities of gas are formed with but small traces of oil. The theory is certainly entitled to serious consideration, and in Oklahoma and Arkansas it has formed an excellent working guide to petroleum geologists. CHAPTER II PETROLEUM PHYSICAL AND CHEMICAL PROPERTIES DIFFERENCES IN SPECIFIC GRAVITY OF VARIOUS OILS Specific Gravity. The specific gravity of any fluid is the rela- tion the fluid bears by weight to the same volume of water. Water has a specific gravity of 1. As petroleum is lighter than water, its specific gravity is expressed by decimals less than unity. Gravity is also expressed in degrees Baume, a method employed by a French chemist to measure the comparative weight of fluids. The greater the degrees Baume the lighter the fluid. The relation between the two methods is shown and explained in Table I. The instruments used are a hydrometer and a standard ther- mometer. The hydrometer, which is a glass column marked with graduations from 10 to 100, was invented by Antoine Baume, a French chemist, and the scale on the instrument has always borne his name. The hydrometer when placed in a jar or a bottle of oil sinks to the point on the scale which indicates the gravity in degrees Baume. The basis of temperature for testing oil is 60 F. and for oil at a greater or less temperature, variations must be calculated. Hydrometers are usually provided with a special scale for figuring temperature variations. The specific gravity is found by dividing 140 by 130 plus the Baume* de- grees, for example: if the hydrometer registers 30, this added to 130 equals 160, which divided into 140 shows specific gravity 0.875. 14 PETROLEUM 15 Following is a table showing Baume degrees, specific gravity, and weight per gallon of oil. TABLE I. SPECIFIC GRAVITY OF CRUDE OIL AND METHOD OF FINDING IT Degrees Beaum6 $ >> Ml I'S g| Degrees specific gravity a& C S c >> M d t* 0><1) c olfe |+9 00 I ^ a~o 10 1 . 0000 8.33 32 0.8641 7.20 54 0.7608 6.34 11 .9929 8.27 33 .8588 7.15 55 .7567 6.30 12 .9859 8.21 34 .8536 7.11 56 .7526 6.27 13 .9790 8.16 35 .8484 7.07 57 .7486 6.24 14 .9722 8.10 36 .8433 7.03 58 .7446 6.20 15 .9655 8.04 37 .8383 6.98 59 .7407 6.17 16 .9589 7.99 38 .8333 6.94 60 .7368 6.14 17 .9523 7.93 39 .8284 6.90 61 .7329 6.11 .18 .9459 7.88 40 .8235 6.86 62 .7290 6.07 19 .9395 7.83 41 .8187 6.82 63 .7253 6.04 20 .9333 7.78 42 .8139 6.78 64 .7216 6.01 21 .9271 7.72 43 .8092 6.74 65 .7179 5.98 22 .9210 7.67 44 .8045 6.70 66 .7142 5.95 23 .9150 7.62 45 .8000 6.66 67 .7106 5.92 24 .9090 7.57 46 .7954 6.63 68 .7070 5.89 25 .9032 7.53 47 .7909 6.59 69 .7035 5.86 26 .8974 7.48 48 .7865 6.55 70 .7000 5.83 27 .8917 7.43 49 .7821 6.52 75 .6829 5.69 28 .8860 7.38 ' 50 .7777 6.48 80 .6666 5.55 29 .8805 7.34 51 .7734 6.44 85 .6511 5.42 30 .8750 7.29 52 .7692 6.41 90 .6363 5.30 31 .8695 7.24 53 .7650 6.37 95 .6222 5.18 To account for the differences in specific gravity of petroleum a number of theories have been presented, as shown below. It is especially important to note the economic side of the ques- tion as classified under that head. EFFECTS OF MIGRATION. Oil is not generally indigenous to the formation in which it is found, but has migrated from other formations. The migration, or travel, of petroleum from one formation to another undoubtedly affects its specific gravity. Petroleum is a mixture of hydrocarbons, each having different 16 PRACTICAL OIL GEOLOGY specific gravities. If petroleum occurs in a sand, portions of it may work upward or downward through the capping above or the bottom formation underlying the sand. If the cappings or bottoms are very fine grained, only a very small proportion of the hydrocarbons will escape. If shale overlies the sand the lighter part of the hydrocarbons will work its way through the shale to the strata above. The heavy constituents will be left in the sand below, some lighter constituents will be found in the shale, and still lighter constituents in the formations above. If the migration is downward, the oils below will be lighter than those above. A very thick oil will not penetrate fine-grained clay nor shale, so there is a limit to the amount of petroleum that will escape from the original formation. Where there are faults or breaks in the formations, allow- ing the escape of hydrocarbons from deep-lying carbonaceous formations to overlying strata, the lighter constituents may es- cape from the lower beds and be found above. Water as- cending along these fault planes may carry the petroleum with it. Necessarily the petroleum that is mixed with water will be heavier than the original petroleum. ECONOMIC ASPECT OF SPECIFIC GRAVITY. As it is known that petroleum in strata of different ages varies, it is of course ad- visable to know the quality of the oil desired and bore for that stratum. For that reason, if no other, it is often important to know the ages of the formations through which the drill is to penetrate. It is generally true that the high-gravity oils occur in formations that are much younger than those containing the low^gravity oils, although there are exceptions to this rule. The position of a well on the fold is most important as regards the gravity of the oil to be encountered. In a closed structure such as that in Fig. 1, the lightest oil will occur near the gas line and the heavier oil near the water line, for petroleum is not x On the Baumc scale the gravity decreases with the number of degrees. High gravities would be smaller numbers than low gravities (see Table 1, p. 13). PETROLEUM 17 a homogeneous fluid but a mixture of a number of hydrocarbons which separate in a vessel according to their specific gravities. Where, however, there is an open structure like that in Fig. 4, Chapter II, the oil near the outcrop will be heavy, due to the escape of the volatile constituents; the oil a little further down the dip will be lighter, and then heavier oil will be encountered near the water line. Where faulting exposes the beds or allows the escape of oil along the fault plane, heavy oil may be expected in proximity to the fault. CHEMICAL COMPOSITION OF PETROLEUM 1 Natural gas, petroleum, bitumen, and asphaltum are all essentially compounds of carbon and hydrogen, or, more precisely, mixtures of such compounds in bewildering variety. They con- tain, moreover, many impurities sulphur compounds, oxidized and nitrogenous substances, etc. whose exact nature is not always clearly defined. The proximate analysis of a petroleum or bitumen consists in separating its components from one another, and in their identification as compounds of definite constitution. All of the hydrocarbons fall primarily into a number of regular series, to each of which a generalized formula may be assigned, in accordance with the following scheme: 1. C n H 2ll+2 6. C n H 2n _8 2. C n H 2n 7. C n H 2n _io 3. C n H 2n _ 2 8. C n H 2n _ 12 4. C n H 2n _ 4 - 5. C n H 2n _ 6 18. C n H 2n _ 32 Members of the first eight series have been discovered in petro- leum. These expressions, however, have only a preliminary value, although they are often used in the classification of petroleum. Each one represents a group of series homologous, isomeric, or polymeric, as the case may be and for precise work these must be taken separately. The first formula, for example, represents what are known as the paraffine hydrocarbons, which begin with 1 After Clark, Data of Geo. Chemistry. 2 18 PRACTICAL OIL GEOLOGY marsh gas or methane, CH 4 , and range at least as high as the compound C 35 H72. Even these are again subdivided into a number of isomeric series the primary, secondary, and tertiary paraffines which, with equal-percentage composition, differ in physical properties, by virtue of differences of atomic arrangement within the molecules. Each member of the series differs from the preceding member by the addition to the group CH 2 , and also by the physical characteristics of greater condensation. Methane, CH 4 , for example, is gaseous; the middle members of the series are liquids, with regularly increasing boiling points; the higher members are solids, like ordinary paraffine. These hydrocarbons are especially characteristic of the Pennsylvania petroleum, from which the following members of the series have been separated. To the list in Table II, the isomeric secondary paraffines, iso- butane, isopentane, isohexane, and isooctane must be added, and even then the list is probably not complete. For instance, the solid paramnes C 2 7H 56 and C 30 H 6 2 have been found in petroleum. Natural gas consists almost entirely of paramnes, mainly of methane, with quite subordinate impurities. In six samples from West Virginia, analyzed by C. D. Howard, the total paramnes varied between 94.13 and 95.73 per cent.; methane, from 79.95 to 86.48 per cent, and ethane, from 7.65 to 15.09. The fol- lowing analyses from other sources may be cited more in detail. (See Table III. ) The analyses of Pennsylvania gases by S. P. Sad tier gave some- what different results. In gas from four different wells he found the following: CH 4 , 60.27 to 89.65 per cent.; C 2 H 6 , 4.39 to 18.39; and H 2 , 4.79 to 22.50. The high figures for hydrogen are unusual and suggest a resemblance to coal gas. In all cases, however, methane is the preponderating constituent, the characteristic hydrocarbon of natural gas. In the natural gas of Point Abino, Canada, F. C. Phillips found 96.57 per cent, of paramnes and 0.74 of H 2 S. Hydrocarbons of the form C n H 2n are, as constituents of pe- troleum, of equal importance to the paraffines. These again fall into several independent series, which vary in physical properties and in their chemical relations, but are identical in percentage PETROLEUM 19 TABLE II. PARAFFINES FROM PENNSYLVANIA PETROLEUM Name Formula Melting point Boiling point 1. Gaseous: Methane CH 4 c. -186 c. 164 Ethane -172.1 - 84.1 Propane . . . C 3 H 8 .. - 37 Butane C 4 H 10 . ' -f- 1 2. Liquid: Pentane 37 Hexane 69 Heptane 98 Octane 125 Nonane Decane CgH^O' - - - 51 - 31 150 173 Endecane Dodecane CnH.24- - 26 - 12 195 214 Tridecane Tetradecane Pentadecane . CuHao. . + 4 252 Hexadecane 18 3. Solid: - Octodecane Eicosane 37 Tricosane 48 Tetracosane Pentacosane C24H 60 . . 50-51 53-54 Hexacosane 55-56 Octocosane Nonocosane C2sH 5 8. C H 60 62-63 Hentria contane r H 66 Dotriacontane Tetratriacontane C 32 Hc6. C H 67-68 71-72 ::::::::: Pentatriacontane 1 CssH^. . 76 1 For a description of these higher, solid paraffines, see C. F. Mabery, Am. Chem. Jour., vol. 33, p. 251, 1905. The literature of these substances is so voluminous that I cannot attempt to give exhaustive references. C. Hell and C. Hagele (Ber Deutsch. chem. Gesell., vol. 22, p. 504, 1889) have described an artificial hydrocarbon, C 6 oHi 22 . 20 PRACTICAL OIL GEOLOGY TABLE III. ANALYSES OF NATURAL GAS A B C D * E F CH 4 ... 93.36 97.63 Paraffines 1 C 2 H 4 , etc 96.36 98.90 87.27 93.56 28 22 CO 53 1 32 C0 2 H 2 3.64 none 0.40 none 0.41 none 0.14 none 0.25 1 76 0.22 none N 2 none .70 12.32 6.30 3.28 0.60 H 2 S none none none none 0.18 O 2 . . none none none none 29 trace 100.00 100.00 100.00 100.00 99.93 100.00 A. From Creighton, Pennsylvania. B. From Pittsburg, Pennsylvania. C. From Baden, Pennsylvania. D. From Vancouver, British Columbia. Analyses A to D by F. C. Phillips, Am. Chem. Jour., vol. 16, p. 406, 1894. Selected from a table of seventeen analyses to show extreme variations. E. Mean of four gases from Indiana and three from Ohio, analyzed by C. C. Howard for the United States Geological Survey. Cited by W. J. McGee, Eleventh Ann. Kept., U. S. Geol. Survey, pt. 1, p. 592, 1891. F. From Oswatamie, Kansas. From a table of seven analyses by E. H. S. Bailey, Kansas Univ. Quart., vol. 4, p. 1, 1895. According to H. P. Cady and D. F. McFarland (Trans. Kansas Acad. Sci., vol. 20, p. 80, 1907), the natural gas of Kansas contains helium. It was found in forty-four samples, in amounts from 0.01 to nearly 2 per cent. composition. One series, the olefines, is parallel to the paraffine series, and the following members of it are said to have been iso- lated from petroleum. Table (IV) is probably exact in an empirical sense, but not so constitutionally. Hydrocarbons of the indicated composition have undoubtedly been found, and some of them are certainly olefines. According to C. F. Mabery, however, the true olefines, or "open-chain" series, are present in petroleum at most in very small amounts. In Canadian petroleum Mabery and W. 0. Quayle identified hexylene, heptylene, octylene and nonylene. largely CH 4 , with more or less ethane. CO not found by Phillips. PETROLEUM 21 In other cases, and notably in the Russian petroleums, the com- pounds C n H2 n are not olefines, but cyclic hydrocarbons of the polymethylene series, which were originally called naphtenes. They were at first supposed to be derivatives of the benzene series, and it is only within recent years that their true consti- tution has been determined. In Russian oils they are the princi- pal constituents, and according to C. F. Mabery and E. J. Hudson they also predominate in California petroleum. TABLE IV. SO-CALLED " OLEFINES" ISOLATED FROM PETROLEUM Name Formula Melting point Boiling point 1. Gaseous: Ethylene . . C 2 H 4 103 Propylene C 3 H 6 .. 18 Butylene .... C 4 H 8 5 2. Liquid: Amylene C H - + 35 Hexylene 68 Heptylene 98 Octylefte. . 124 Nonylene Decylene CgHig.. . P TT 153 172 Undecylene Duodecylene CnH 2 2. . 195 216 Tridecylene . r TT 232 7 Cetene C 16 H 32 275 3. Solid: Cerotene 65-66 Melene CsoHeo- . 62 Members of the series from C 7 Hi 4 to Ci 5 H 30 were isolated from the California material. Mabery and S. Takano also found that Japanese petroleum consisted largely of C n H 2n hydrocarbons. Other similar occurrences are recorded in the treatises of Hofer and Redwood. 22 PRACTICAL OIL GEOLOGY The series C n H 2n -2 is often called the acetylene series, after its first member, acetylene, C 2 H 2 . The lower members of this series have not been found in petroleum, but several of its higher members are characteristic of oils from Texas, Louisiana, and Ohio. In oil from the Trenton limestone of Ohio, Mabery and O. H. Palm found hydrocarbons having the composition Ci 9 H 3 6, C2iH 4 o, C 22 H 42 , and C 24 H 4 e. With these compounds were also members of the next series, C n H 2n _ 4 namely, C 23 H 4 2, C 24 H 44 , and C 25 H 46 . In petroleum from Louisiana, C. E. Coates and A. Best found the hydrocarbons Ci 2 H 22 and Ci 4 H 2 e. These, together with Ci 6 H 30 , were also separated by Mabery from Texas oils. These oils are furthermore peculiar in containing free sulphur, which separates in crystalline form. Table V shows the average chemical composition of a number of petroleums. Table VI gives the commercial values of the same petroleums. ANALYSES TABLE V. ELEMENTAL ANALYSES 1 Nos. Field Specific gravity at 15 C. Heating value per gram Hydro- gen Carbon Nitro- gen Sul- phur Unde- ter- mined 545 Kern River Calories Per cent. Per cent. Per cent. Per cent. Per cent. composite 2 . . 0.9670 10,312 11.27 86.36 0.74 0.89 0.74 535 Coalinga .9505 10,400 11.30 86.37 1.14 .60 .59 542 McKittrick. . . .9600 10,186 11.41 86.51 .58 .74 .76 543 Midway .9580 10,314 11.61 86.58 .74 .82 .25 544 Sunset .9705 10,233 11.37 85.64 .84 1.06 1.09 1 The samples were dried by filtering twice through about 2 cm. of anhy- drous sodium sulphate before analysis. 2 See Table VI. PETROLEUM 23 (ji3io jauiuioo ) uinq.[Bu_dsy CO CO k I OS i>! -* co o co <*< co < 00 00 CO CO t>^ CO IO O CO * T< IO remer andBicknell. * Composed of 40 grams each of laboratory Nos. 84-99, 165. 369, 475 482. LI, 13, 15, 18, 26, 27, Composed of 40 grams eachof laboratory Nos. 100-108, -410. 454, 456-474. 6 Composed of 50 grams each of laboratory Nos. 109-124, 446-453, 367. ^suinivna d ' T- ' r-I . . . . sjsso[ auiuga'jj OS 00 00 r-1 CO ~ 6"- 10 10 co 10 ; 10 10 (pauuaa) o co O t~- '(MO * co co t^ r-l 00 ' CO *< & m oo o (paugaa) auijosBQ $ : : : BOP"* 10 10 OS OS OS OS OO 00 OS OS OS OS OS os t^ os OS OS OS OS (pauijaaun) : : ; jnudmg CO OS vO OO OO OS O ' OO !< IO CO t~ t>- CO - ^ (ajeos J9|3u3') 'O QZ V* A-HsooeiA CO O lO O O t*- -l OS (M ao U B3 aad ^3^ aj ' co co |J oo oo S3 |S t>l t>I oo oo ^ 00 00 OS os os ; o o tI t^I 00 OO uoip3 jaj o o ON CO O CO CO t^ 00 * * ' T-< CO rH CO O 00 OO . 00 CO OO OO . OS OS e? punod aaj "S CO (M H lO CO lO lO t~ o oo us (M N O CO t~ t>- 10 CO CO IO ' OO OS i Calculated, Chemical and Metallurgical Handbook, C 2 Composed of 30 grams each of laboratory Nos. 126- 3 Composed of 20 grams each of laboratory Nos. 6, 9, ] 30, 44, 49, 51, 52, 54, 59, 63, 67, 69, 70, 71, 74, 76, 372 : 2 2 OO 00 . 00 00 oo" oo . oo oo" w t^ (M 3 ill o o oo oo >*<< N 1-H ^ -^ co co * T^ ' O CO CO CO ' '. "S. ' S S 2 c a e a co c cc f3 OS S i "5 3 o c > o g^oj^o ON -qi kO lO CM *" IO US O O "5 24 PRACTICAL OIL GEOLOGY TABLE Via. AVERAGE ANALYSES SHOWING COMMERCIAL VALUES OF OKLAHOMA OILS Location Specific gravity, (at 15 C.) Degrees Baum6, (60 F.) Calories per gram B.t.u. per pound Viscosity at 20 C. (Engler scale) Water (per cent.) Sul-, phur per cent.) Avant . 8617 32 49 10 828 19 490 2 ^ l 17 Bald Hill .8465 35 40 10905 19 629 2 3 1 17 Bartlesville Bigheart Checotah .8604 .8547 .8610 32.71 35.58 32 60 10,883 10,904 10 910 19,585 19,589 19 638 2.3 2.3 3 5 .0 1 .14 .16 H Cleveland Collinsville- Clare- more. Gushing .8388 .8585 8389 36.94 33.10 37 00 10,921 10,846 10911 19,658 19,524 19 639 1.7 2.6 2 .0 .0 o .21 .20 07 Flat Rock Glenn Pool Gotebo .8635 .8445 .8595 32.14 35.83 32 89 10,804 10,879 10,925 19,448 19,582 19,665 3.0 1.8 2 9 .0 .2 i .26 .28 25 Hamilton Switch . . . Henrietta Hominy Creek Madill... .8439 .8720 .8585 8504 35.92 30.55 33.09 34 64 10,907 10,761 10,838 10893 19,633 19,370 19,508 19 608 2.0 3.3 2.7 3 7 .0 J .1 o .18 .35 .20 16 Mounds .8635 32.14 10,826 19,488 3 5 22 Musk ogee Nelagony Nowata .8304 .8615 .8525 38.60 32.51 34.22 11,009 10,827 10,920 19,817 19,489 19,656 1.5 2.4 1 8 .0 i 1 .10 .19 14 Okmulgee Oresa Osage City Pawhuska Ponca City .8530 .8665 .8472 .8710 8144 34.13 31.58 35.30 30.73 41 91 10,850 10,836 10,879 10,807 10998 19,531 19,506 19,506 19,453 19 797 2.6 3.0 2.0 6.6 1 2 .1 .3 .0 .1 o .20 .18 .24 .23 10 Red Fork Salt Creek Sapulpa . . . .8457 .8511 8635 35.57 34.52 32 14 10,928 10,881 10826 19,670 19,585 19 486 1.9 2.6 2 7 .0 .0 o .24 .17 25 Schulter .8600 32.84 10,840 19,513 2 8 .0 .23 Turley .8772 29 67 10,790 19,422 7 2 o 23 Wheeler 9166 22 76 10554 18998 40 2 6 1 20 Grand average .8544 33.96 10,870 19,567 3.9 .0 .23 1 Trace. PETROLEUM 25 > g-C o oooe-oosi 000 00 000 d * c o S3 1 T-t d fc c 5 eptuo 00 CO 00 MOO * CD O O ,_( _| ,_, CO,-! ,H ^H CO (^uao jad) ja^ra^ ;;;;;; ! s (}uao aad) ^Budsy lO t> CO OO CO O t-J W ' C,uaoaad)u a ,^ tl ^ t co o >o co co ^ o C S 1COCOCO'^C S ^ iN^O !O Distillation by Engler's method 3 3 ffl E1 -uao'o^o CO I> -*<* i-l IN O OS N. CO iO 1O >O CO OS OS CO OS OS OS OSOS OS OS OS OS ouioadg 73 -H OO i 1 lO CO CO OOOS !O CO CO IN CO lO 00 CO >O i-l O O i-l IN O i-l O CN -! OS OS OS OSOS OS OS OS OS d 1 -STo^So CO CO t^ OSOS i-H cN O OS J> 00 O> Os'cO IN O CO l^ ^ ouioadg O O OS OSOS O OS I OS 00 00 t* t^ t^ 00 !> OO l^ d 1-1 -uao oiqn^) OOO OO OOO O COCOCO' N OOO lO OO t- O (N i-t (N^H rH ^H . ^H d i H -nao oiqnQ OOO'O^O O O t^lNO.COCQO CO CO 'Oo W II OC I ^ suiSag CO 10 O COO 10 O O CO ^ co 10 o co co co t>- t> Physical properties o 73 0} P-i *^J odd do do d -"^"i" 1 5! ^i 1^11 *! i ^ I F o 9 umB 9 CN t> t OO (N O d t^ oupadg CO "* ^ 00O 00 CO ^ 00 00 lO >O OCO t>- CO CN -^ Oi^iHT^C^iH i ( O CO OO 00 00 OOOO 00 00 OS 00 d (;aaj) IP M jo q^da a . 1 3 26 PRACTICAL OIL GEOLOGY *" ,Q Doooc-oosi o o o o o ^ i-I OJ 05 ^ ^ apnao * W CO i * r-I CO CO iH O5 CO ^ CO CO iO Ouao aad) aa, BM : h H H H : ((juao jad) ^Bqdey O t^ O * 10 O O : ! d ('Itiao aad) uig'e.i'Bj o o o o o (^uao jad) jnqd[ng g : : : : : '. (N i-! Distillation by Engler's method By volume 1 IP O5O O OO 05 "* "# Ob- Residuum at'3 ,- : : : : 5 S J: *JH Tj< ^ CO IO ! I * " o I'Pi CD b-00 b-b- b 1 lib 05 , b- b- IH i-i b- O C^ IO rH O3 (N CD b- i Sb? 00 00 00 00 00 00 d ' ll^ IN. QO O O Ob-0 b- 05CO . . C^^COC^ COb- i 1 OO5 *OCO j-H'rJiTttTtt CON CO MrH IMCN To 150 C. s*b oj'3 {I"- 1 . CO 1C :1 : S : : : : : : :d ' : : : : i.2'"* 3 i 2 10 CO b O 1C b i< O O 05 b-' 06 Tj! 1-J co --I Physical properties 'Oo ' B IIP 8 !? 1 smSag iO 1C b- iO O O5 00 00 O b- 1 O ; i LLJilAi! 3 : 44 3% ^S ^ 6 d - : S2 3 2^ &S' ^ s & * Q ^ ^v* Q W rt Ssco auimjg ocoiNb. I-HIO -^ oco i ~; t> : 00-ib^OO O5(N -^ i-lOO COOS o Distillation by Engler's method By volume |||| * IN * CO i-< ^ >o 06 d 06 co OS OS OS OS OS Residuum 11 03 M d .S-i " 3 s I OS (N OS I i-l ^ OS >O CO CO 1-1 6 CO 1 CO M 1-1 t 00 t^- * d ||| o >c o o o o CN CO i-l * CO i-l IN IN IN N (N -* u | 11 co w 1 ! I S-i " ill 10 O O iC 10 O (N (N 0 00 t~ OS tN OS O O t^ Physical properties ,0,00 >^ o . a 1 1 - o- d o S 05 J___ o I S3 1 O 1 (N M< 10 * o -^ C^ CO CO CO T^ < X X X x X X~X> xxx xxx xS x; X X X x x x X/ * X X X X X "X/7 x x x x x x x^ x;X x x x x xy x^X X x X X X/ x X X X x X yl Boulders xx x x x x A/ Sa , nd vX x X x Xjoo o^Ss_ / Sea Level Y * \ x [ igneous Eock |o oo o | Gravel J Sand IL-T^-TZJ Clay, Shale x x x x x x^uS^rfiS^orr-?^ ^ _ x -x - >< n^^s^^^^^^- Clay KXXXXXXXXXX x^^^?^^^ ^. xxxxxxxxxx xx x >S^^|So-?^ |^^^^v^_^ Shale ^XXXXXXXXXXXXXX Xx~2^~^ yXxXXXXXxXxXXXXXXXXXX x ^~^ V , in Fig. 3, are also conformable. TTrn-i-rrr-: -"^r-^^ FIG. 3. Illustrates conformity, erosional and angular unconformity Where the beds have been pushed above water and exposed to erosion, then have sunk again and other beds formed upon them, one finds an erosional unconformity, as shown at A 7 in Fig. 3. Where beds have been deposited, then upheaved, and folded, later eroded and have then sunk again, and still later beds depos- ited on them, a condition similar to that at E in Fig. 3 results. This condition is called an angular unconformity. 3 34 PRACTICAL OIL GEOLOGY Fig. 4 illustrates a condition by no means uncommon. The lowest formation is older than the upper and was tilted before the upper bed was deposited on top. Wells at 1, strike sand A ; at 2, A and B; at 3 A ; at 4, A and C. FIG. 4. Illustrates angular unconformity, its relation to migration of petroleum, also relation of wells on such a structure. FIG. 5.- Unconformity between tilted Monterey shale and horizontal Pleistocene sand and gravel in Californiac (Bull. 322, tL S. G. S.) STRATIGRAPHY 35 OVERLAP. If beds are deposited along shore lines while the Coast is slowly sinking, the first beds, A, laid down (see Fig. 6) are covered by material that is in turn covered and hidden by later beds, B, C and D. The higher beds progressively lap over the lower beds. Fig. 6 shows an overlap and also an unconform- ity between the crystalline rocks and the sedimentaries. ii^^-x x * X X X X X X X : x x :- == Z==-~X XXXXXXXXXXXXX XXXXXXXXXXXXXXXX ,.;;^dlliiHi^iliiii FIG. 6. RELATIVE AGES OF FORMATION Order of Superposition. The relative ages of beds depend primarily upon the order of their deposition. Normally the older beds -are beneath the younger. This simple law is the basis for determining the ages of beds. However, folding and faulting may change the position of certain beds but not their age. Hardness of Formations. The older the formations, the harder they are, generally. Sand grains when cemented become sand- stones, shales become compressed and cemented to form slates. Jointing also becomes more pronounced in the older rocks. Lithologic Similarity. Many times attempts have been made to correlate or classify rocks in a region according to their color, texture, or mineral composition. Such means of correlating do not hold good under all conditions, and serious mistakes are sometimes made by correlating certain beds which in reality may be some distance apart. The surest test of working out any structure is to "walkout" the beds, that is, follow one known bed in all its rising and falling. In some places such 36 PRACTICAL OIL GEOLOGY procedure cannot be accomplished, in others it is not necessary as the structure can be clearly seen. A sandstone of Cretaceous age may look exactly like one of Miocene age in color and in texture. Sands of both ages often appear identical. However, in some cases, where marked dis- similarity appears over a district, certain formations may be readily correlated. If a thick red shale occurs in a region it may extend over several hundred square miles and act as a horizon marker. Conglomerates, due to terrestrial or near-shore conditions, are not reliable markers as they may die out within 1 or 2 miles. Some sandstones are very persistent. They mark old beach conditions; and often cover entire counties. Limestones are also very persistent horizon markers. It is essential to discover the peculiarities of any forma- tion, for where fossil evidence is lacking such peculiarities are often of value in checking up formations within the limited ra- dius of 2 to 3 miles. Fossils. The proper correlation of beds is best accomplished by the use of fossils. It has been found that when certain classes of fossils occur in a stratum, the age of the stratum is fixed definitely and its position above or below others is determined. However, fossil evidence must be used very carefully and only by experienced workers. Fossils, such as oyster shells, scallops, gasteropods and micro- scopic organisms (foraminifera and diatoms), form the chief basis for stratigraphic classification. Fossils may be of great value to the geologist and practical man, but it is important, however, to know the fossils that are characteristic of certain horizons. In some regions beds of known ages carry oil and all others may be ruled out. The ages are determined by the order of superpositions as explained above, and by fossil evidence. Where beds are overturned as in Fig. 7, fossil evidence gives a clue to the true condition. The fossils in A are younger than those in B. Normally A would overlie B as at /. At // the STRATIGRAPHY 37 order is reversed while at /// the order is normal again. The true order of the beds is then as shown at / and ///. Other evidence, as dips and curvatures, generally bear out such condi- tions, and in some cases actual folds in miniature show the true condition. in FIG. 7. Illustrates the use of fossils in correlating formations. By means of fossils one may often correlate oil-bearing forma- tions many miles apart. Fig. 8 shows the application of fossil evidence-- At / oil occurs under the beds carrying certain fossils, as oysters and scallops. At II the same fossils occur FIG. 8. Illustrates the use of fossils in correlating formations. which would lead one to believe that the same oil strata under- lie the fossil beds occurring at this point. Oil operators from Pennsylvania will see certain formations in California, say a sandstone, that looks very much like a bed in Pennsylvania. Immediately the operators will call the bed 38 PRACTICAL OIL GEOLOGY the same age, when in reality there is absolutely no connection between the two. The California oil formations are millions of years later than the Penn- sylvania oil formations. The lowest California oil is in the topmost Cretaceous, and the highest Pennsylvania forma- tions are in the Carboniferous system. Table VIII shows the difference between the East- ern and Western oil horizons. These differences are worked out by correlating the fossil evi- dence throughout the United States. Geologic Column. A geo- logic column (see Fig. 9) is often of great assistance. By means of such a column one knows the formations that must be penetrated by the drill, the thickness of each for- mation, the depth to oil, etc. These vertical sections en- able the contractors and drill- ers to choose drilling rigs, and to determine the depths, hard- ness of formations, etc. Such a column is merely a graphic representation of the stratig- raphy of a region. One col- umn does not hold good over a very large area, so new sec- tions must be made for dif- ferent parts of a region to take into account local changes in thickness, character, etc. G=> < = , <__., <= . *-^~* CO O o a ^200 Gravel ~ ~ _-_-_-. 175 Gray 975 'J Fernando - rrzL. lied rr^jrrzL^l Shale Clay \ Lnc I 500 onforinity Conglomerate Granite Pebbles ~ ~^ ^^ - U' Water Sand I860' ^rE^-^rL loo Petroliferous UOO Shale . . (Brown) : v:V". : :-:^":V : .- ; -'-':V. 1.200 Oil -Sandstone / ^B I 250 { Unc '175' Oil -Sand (Coarse) onformity Blue Sand Stone . . . 300 Black Shale 725' Vaqueros 150' Oil Stained Oil Sand (.100 \ Un 7150' Blue S.S. onformity Blue Shale 450' - : ;'v': : ^v^0iv:!:: : - } 100 Blue S.S. Sespe 1 ^200 ">, 2 Lower coal measures. Lower Cow Run sand S. W. Penna., W. Va. & S. E. Ohio. 600 c Bridgeport sand Bridgeport, 111. U Carbonif- erous 700 and 800 ft. Macksburg sands S. W. Penna., W. Va., S. E. Ohio & Ky. 850 & 925 H $ Salt sands 1 Gas, sand / S. W. Penna., W. Va., S. E. Ohio & Ky. 950 to 1080 Pottsville Cherokee sand- Kansas & Oklahoma. group. stones Buchanan sand- stone Casey & Robinson (400 ft.) 111., and Princeton, Ind. Benoist sand Sandoval, 111. I11.& Oakland City, Ind. 1 Keener sandstone S. E. Ohio & W. Va. 1275 s c 99 Big Injun sand \ Squaw sand J S. W. Penna., W. Va., S. E. Ohio & Ky. 1340 1425 C. 1 Pocono Berea grit S. W. Penna., W. Va., S. E. Ohio & Ky. 1700 J r? First, 100 ft. or Gantz sand W. Penna., W. Va. & S. E. Ohio. 1850 50 ft. sand W. Penna. & W. Va. 1885 Second or 30 ft. sand W. Penna. & W. Va. 2000 46 PRACTICAL OIL GEOLOGY TABLE VIII. GEOLOGICAL FORMATIONS OR "SANDS" IN WHICH OIL AND GAS ARE FOUND IN THE UNITED STATES AND CANADA (Continued) Era Geological system Geological series or group Producing forma- tion or sand Locality where productive Approxi- mate depth below Pittsburg coal. Feet Stray or Bowlder sands. W. Penna. & W. Va. 2050 Third or Gordon W Pa W Va & Ohio 2130 sands. Fourth, fifth and sixth sands S. W. Penna. & W. Va. 2200, 2260 & 2590 First, second and third Warren sands N. W. Penna. 2700, 2815 &2900 Tiona sand N. W. Penna. 2950 Speechley sand N. W. Penna. 3020 Cherry Grove sand N. W. Penna. & W.N.Y. 3150 Bradford sand N. W. Penna. & W.N.Y. 3460 Elk County sands N. W. Penna. & W.N.Y. 3650 Hamilton formation Petrolia & Oil Springs, Ontario. 5330 U Corniferous lime- stone N. E. & Central Ohio.W New York & Ontario. 5625 w )J < PH Niagara group. Oriskany sandstone New York, So. Ind. & Ont. 5660 Guelph limestone Ontario & W. New York. 5700 Niagara limestone W. New York, Ontario & Indiana. 5820 Clinton limestone ) Clinton sandstone } Cen. Ohio & Welland Co., Ontario. 5985 6025 Medina red sand- \ stone Medina white sands ) W. New York & Wel- land Co., Ontario. 6085 6200 Trenton limestone, upper. N. W. Ohio, Ind. & Ky. 8700 Trenton limestone, lower N. W. Ohio, W. New York & Ontario. 9200 N Y , Ga., Ala & On- Potsdam sandstone tario. Quebec group Newfoundland. New Brunswick. 9230 STRATIGRAPHY 47 STRATIGRAPHICAL DISTRIBUTION OF PETROLEUM PRODUC- TION TO 1913 It is interesting to note the ages that produce the oil of America. The table presented below, after Clapp (Petroleum and Natural Gas Resources of Canada, Vol. I) shows which ages have been productive. Tertiary Upper Cretaceous. . Pennsylvania!! Mississippian Upper 'Devonian. . . Devonian Ordovician . . 1,935,763,780 bbls. 42,548,025 bbls. 343,843,256 bbls. 726,815,070 bbls. 540,304,235 bbls. 14,099,053 bbls. 318,095,570 bbls. California, Gulf Coast; Foreign except Canada. Marion Co., Corsicana to Powell, Texas; Wyoming; Colorado. Electra and Henrietta, Texas; Oklahoma; Kansas. Illinois; one-half of the Appala- chian field. One-half of the Appalachian field. Canada. Lima-Indiana. NOTE. In Oklahoma there is some question as to whether or not the Permian is an oil-producing horizon of importance. It is certainly an impor- tant gas producing horizon but the petroleum side has not been established definitely. ^The recent find at Garber, Oklahoma, is apparently Permian, close to the Pennsylvanian contact. CHAPTER IV STRUCTURAL GEOLOGY OIL FIELDS ON FLANKS OF GREAT MOUNTAIN UPLIFTS One great truth that must be emphasized is the occurrence of oil-fields on the flanks of the great centers or lines of uplifts. Thus all the American oil-fields at least, and most European fields, occur in the folded regions contiguous to centers or lines of disturbance. The centers of these uplifts show the older granitic rocks, and necessarily do not carry oil, but minor folds affecting the sedimentary rocks form favorable conditions for accumula- tion. The California fields occur both on the east side of the Coast range, and the west side of the Sierras Nevada. Again, the Utah fields, Wyoming fields, and Colorado fields occur on the flanks of the Rocky Mountains. The north Oklahoma and the Kansas fields occur on the west flank of the Ozark uplift, the western Illinois fields be on the east flank of the Ozark uplift. The LaSalle uplift affects the central Illinois and Indiana oil- fields. The Cincinnati uplift controls part of Indiana, Ohio and Kentucky. The West Virginia and east Pennsylvania fields occur on the West side of the Alleghenies. The southern Okla- homa oil-fields center around the Arbuckle uplift. The Sabine uplift controls the northwestern Louisiana fields, and the Burk- burnett uplift in Texas controls the north Texas fields. In Mexico the oil fields occur on the eastern flank of the Mountains. Nearly every oil field in the world occurs in close relationship to some earth curve or fold. Underground structure is one of the most important features of oil-field geology. So much de- pends on favorable structure that a careful study of the various types of oil-field structure is necessary. Below is a classification that is sufficient for all practical purposes: 48 STRUCTURAL GEOLOGY 49 Anticlines . . Syiiclines. . . f Single [ Compound f Single \ Compound Symmetrical Asymmetrical Overturned Symmetrical Asymmetrical Overturned 3. Monoclines ... Terraces 4. Combinations of 1, 2 and 3 5. Domes. (a) Anticlinal (6) Saline (c) Volcanic 6. Faulted forms of any of the above. 7. Stratigraphic forms lenses, fracture planes, etc. Every fold is part of an earth curve and must be considered as continually changing in dip or slope. The cause of folding is problematic. It is thought to be the result of the contraction of the earth's surface due to internal cooling. In places the crust of the earth is forced by folding into arches, and sags or basins. The results of such folding are structures called anticlines, syn- clines, domes and monoclines. Breaks or faults may affect all the above forms and make still more complicated structures. Where masses of igneous rocks force the strata upward, folds very similar to domes are formed. Volcanic necks or plugs may thus lift the formations around them, forming arched structures that are important factors in the accumulation of petroleum. Another form of arching such as the Saline domes of Texas and Louisiana is thought to be due to recrystallization of salt masses. The folds generally decrease with depth. Folding is near-sur- face phenomenon, as is often noticed the folds become more con- tracted toward the center and flatten with depth. 1. Anticlines. The distinction between anticlines and domes is at present loosely drawn. In this book anticlines will be differentiated from domes as follows: An anticline is a long, relatively narrow fold with the dips or slopes of its sides inclining away from a line of folding called an axis. Such a fold will eventually disappear due to gradual 50 PRACTICAL OIL GEOLOGY flattening or to faulting, merging with other folds, etc. When the fold flattens out, the ends of the fold plunge or dip along the line of the axis resulting in what is designated a plunging anticline. An anticline takes its type name from its cross-section. Fold- ing is not only along a plane vertical or inclined to the horizon, but is also sinuous on the surface. Where folds curve sharply the beds on the inside of the curve are compressed; those on the outside are under tension. This results in local- izing the oil at those portions of the fold which are opposite the point of greatest compres- sion. The simple anticline has but one high place or apex. If two or more high places form on the long fold such high places are designated anticlinal domes. The low places on the anticlines be- tween such domes are called " saddles." Other names for anticlinal domes and saddles are " structural highs" and " structural lows" respec- tively. A fuller discussion of anticlinal domes is given later in this work. Two other types of domes are also found which will be discussed later. Anticlines are of many forms of types: Symmetrical anti- clines are those anticlines in which the inclinations or dips on both sides of the axis are equal. (See Fig. 10 a, b, and c.) Asymmetrical or inclined anticlines occur when one of the limbs or flanks has a greater dip than the other. (See Fig. lla, FIG. 10. Forms of symmetrical anti- clines. STRUCTURAL GEOLOGY 51 116 and 12.) Asymmetrical anticlines are the most common type of fold. Folds are overturned when the axes of the folds fall over, as in Fig. 14 also as in Fig. 7 in Chapter III. Isoclines belong to a peculiar type of symmetrical anticlines. Such folds are not very common but occasionally occur. Compound anticlines consist of a system of parallel anti- clines which often cover a large area. The California and Penn- sylvania oil fields clearly illustrate this condition. Dry Hole FIGS, lla and 116. Types of asymmetrical anticlines. 2. Synclines. A syncline is a structure the reverse of an anticline, and receives its name because its beds incline toward a common central line. Synclines are as varied as anticlines, and for every anticline one will nearly always find a similar syncline. Three examples of synclines are shown in Figs. 15, 16 and 17. \ 52 PRACTICAL OIL GEOLOGY Fia. 12. Inclined fold Temescal Ranch, Ventura County. (After Watts, Calif. Mining Bureau, Bull., 19.) FIG. 13. View of South Mountain anticline near Santa Paula, Calif. STRUCTURAL GEOLOGY 53 When the basins are filled with water, oil may be found on the flanks of synclines. When little or no water occurs in the basin, oil may be found close at the bottom of the depression. (Figs. 15, 16 and 17.) FIG. 14. Steeple-shaped anticline overturned at top. FIG. 15. Illustrates possibility of finding oil in synclines. FIG. 16. Illustrates an asymmetrical syncline. Deformation. The amount of arching is called the deformation of the structure. It is measured from the bottom of the syncline to the top of the anticline. (See Fig. 18.) 54 PRACTICAL OIL GEOLOGY In California, Wyoming, and other steeply folded areas, deformations of 500 to 5000 ft. are known. In Oklahoma and Kansas deformations of 10 to 200 ft. are known, but by far the larger proportion of structures show only 40 to 60 ft. deformation. Gushing, the most productive of all Dry Hole FIG, 17, Illustrates complex folding. (After U, S. G- S.) Oklahoma pools, shows 160 ft. from the syncline to the top of the dome. Such low deformations usually occur in distances of half a mile to a mile. An East dip 160 ft. in a distance of 6 miles occurs near Onaga in Pottawatomie County, Kansas. KANSAS-OKLAHOMA-TEXAS FIG. 18. 3. Monoclines. A monocline is a structure with one slope or inclination. Its name comes from mono, one, and clino, sloping. Monoclines are simple structures as shown in Fig. 19. They are often limbs or flanks of giant anticlinal folds or of giant domes, where but one side of the fold is apparent and that dipping in one direction. The northeastern Oklahoma oil-fields are located STRUCTURAL GEOLOGY 55 on minor folds that occur on a great northwestern dipping monocline. Normal Dips. In all regions of uplift the dip of the beds is naturally away from the center or line of the uplift. The great X X X X <. X XX X X X X X C X XX X X X X X XXXXXXXX XXXXXXXXXXXXXXXX Xxxxxxxxxxxxxxxxxxxxxxxxxxx XXXX XXXX