Abstract Discovery. Geologic factors. Economic factors. Personal factors. THE PETROLEUM GEOLOGIST is the center pier in the foundation of the petroleum industry. The industry is completely dependent upon a continuing discovery of new pools, or extension of old pools, for maintenance of its supply of crude oil and thereby of itself; and most certainly “the discovery and production of oil is a geological enterprise.” 1 Because of its dependence upon geologists to guide it in its search for petroleum, the industry has entrusted many geologists with much greater business and management responsibilities than fall to the lot of the average scientifically trained person. This is in part because the geologist is accustomed to thinking in terms of many variables, and the management of the oil industry, possibly more than that of most others, must deal in variables, many of which are not known. It is also because the geologist understands better than anyone else the hazards upon which much of the exploration money and effort is spent, and can therefore better appraise the chances of its bringing in a fair return. The result is that the petroleum geologist is now the key in a complex interlocking of many specialized abilities, ranging from those of persons doing wholly scientific work to those of persons engaged wholly in management. The final chapter of this book is therefore devoted to an analysis of the place of the geologist in the petroleum industry and to some of the factors involved in the end point of his effort—the discovery of new pools or the extension of old ones. These factors might be thought of as centering on the petroleum prospect, which is that combination of geology, economics, and personal opinion that justifies the drilling of a test well. DISCOVERY The discovery of petroleum generally follows a more or less similar pattern. First, a prospect is located that is thought to be worth drilling; second, a test well is drilled into the potential reservoir rocks. The answers to the questions “What is a prospect?” and “What makes a prospect worth drilling?” combine not only geology but also economics and many personal attitudes in an almost infinite number of combinations and variations. Each prospect is unique. In giving thought to the various factors that go to make up a petroleum prospect, it should be remembered, first of all, that a favorable prospect is the immediate objective of the petroleum geologist and is a prerequisite for every wildcat well that is drilled. But the value of a prospect is partly determined by the varying needs of operators. Each prospect has a different value and appeal to each operator who might consider spending time and money in testing it. What seems like a good drilling prospect to X Company, for example, may hold no interest for Y Company with its different experience and needs. And what makes a first-class drillable prospect to an individual may have no appeal to a major company. It should also be remembered that many prospects are found, and that many pools have been discovered, without the benefit of formal geology. By the very nature of the occurrence of oil and gas, especially in areas of stratigraphic traps, if enough holes are poked into the ground, discoveries will be made—even as the plum will be found if enough cuts are made into the pudding. Some of these discoveries come from what might be termed “magic geology”: the area “looks like Pennsylvania,” the creek “makes a bend like the one at Walnut Bend,” or “any prospect near a town named Eldorado is good enough for me—remember the rich oil fields at Eldorado, Kansas, El Dorado, Arkansas, and Eldorado, Texas?” Others come from the thinking of the “lay geologist,” who knows he should drill on a “high” or “get up against a show of oil” and remembers that “twenty years ago ole Joe Doakes said there was an oil field under the pile of rocks in the far forty”; and other discoveries come from the advice of “doodle-buggers”—those persons of mystery who continually seem to have some new method of locating oil and gas pools(?). The efficiencies of these methods are low; that is, the ratio of dry holes to discoveries is three or four times higher than with the orthodox methods of geology and geophysics; but in the aggregate they find many pools and furnish many needed well records for more scientific work. The discovery of oil is very much like fishing: you have to keep a baited hook in the water to catch fish, and you have to drill wells to find oil. Whenever a wildcat well * is drilled, it means that someone, for some reason or other, has located a prospect that he believes worth testing. The fact that most wildcats result in dry holes is not a deterrent to the effort, just as the real fisherman is not discouraged if he doesn’t get a fish every time he goes fishing. For many years, the record in the United States has been that one out of every nine new-field wildcat wells produced some oil or gas. Of more significance, however, is that during the past 18 years it has required 38 new-field wildcat wells for the discovery of one oil field containing one million barrels or more. 2 A field containing a million barrels would supply only about one-tenth of the daily demand for the United States and for the operator may be either nonprofitable or barely profitable. The continuing need for locating many new prospects is readily seen. While the petroleum prospect is first and fundamentally a geologic feature, the ultimate decision whether it justifies drilling depends upon many economic and personal factors along with the geologic factors. These three kinds of factors are useful headings for examining the question of what constitutes a prospect.

Abstract Delhi field is located in northeastern Louisiana at the updip limit of the Tuscaloosa producing trend. The accumulation occurs in Cretaceous sandstones that subcrop near the southern edge of the Monroe uplift and locally form a trap by lateral pinchout. Recognition of substantial northward thinning in the Cretaceous section of the area led to a joint exploration venture by C. H. Murphy, Jr., and Sun Oil Company in 1943. This team drilled one dry hole about 12 mi (19 km) east of what is now the field area and then conducted a fairly extensive reflection seismic survey near the town of Delhi. The survey revealed a 700-acre structural closure on which Murphy-Sun drilled their second wildcat and discovered the 13,590-acre field. Discovery of the field is attributed primarily to pursuit of an idea based on broad-scale subsurface information.

Abstract Productive oil and gas reservoirs of Cretaceous age underlie the large inner part of the Gulf Coastal Plain from the Rio Grande toFlorida at depths within practical reach of thedrill. Productive Jurassic formations are accessible in a narrower belt of the same region. Thegross structural framework, reduced to simplestterms, consists of (1) a complex system of normal faults rimming the Gulf Coast geosynclinefrom southwest Texas across northeast Texas, southern Arkansas, and Mississippi into Alabama, (2) the Sabine uplift centering near thenorthwestern corner of Louisiana, and (3) “interior” salt basins in northeastern Texas, northern Louisiana, and southern Mississippi—southwestern Alabama (Fig. 15-1). Local structuralfeatures in the basins are due mostly to saltmovement. A regional unconformity which is ofslight consequence in southwest Texas introduces a large angular discordance betweenUpper Cretaceous and older formations northeastward from the Sabine uplift. In 1920, the only important oil productionwas on the Sabine uplift and the nearby Homerdome in northwestern Louisiana (see Chap.8.2 and 8.4). The Monroe gas field in northeastern Louisiana (see Chap. 8.3) with reserves of 7 trillion cubic feet, was supplying avoracious carbon-black industry (Meyerhoffand Forgotson, 1968; Shreveport GeologicalSociety, 1968). Full development of the vastMonroe reservoir was delayed for several yearsuntil pipelines were laid to distant markets(Fergus, 1935). A momentous discovery at Mexia, Texas, in December 1920 initiated exploitation of the prolific Wnr“ina_. gand andopened the important fault-zone territory. Thefirst producing well in southern Arkansas wascompleted near El Dorado in January 1921, and a large oil field was proven at Haynesville