Abstract Reference Was Made in Chapter 5.06 and 5.07 to the search for pe- troleum in modern sediments, sponsored by the American Petroleum Institute, and to the negative results of Trask’s monumental work. The search continued, however, and in 1952 P. V. Smith, Jr., of the Standard Oil Development Company, Esso Laboratories, Chemical Division, was able to announce that petroleum-like hydrocarbons are, indeed, being formed at the present time in sediments on the floor of the Gulf of Mexico.

Abstract Although the search for hydrocarbons in Indonesia was initiated about 8 decades ago, exploration work is still at a high level. Recent studies have resulted in a new understanding of the Tertiary sedimentary basins, and knowledge concerning offshore sedimentary basins has been updated significantly. More important, however, is the current knowledge of the mechanisms of basin formation which seems to enhance the validity and applicability of the new global tectonics to the geology of Indonesia. Recent exploration surveys and subsequent drilling have shown that the southern part of the Sunda Shelf consists of many sedimentary basins and intervening uplifts. Major faults are common throughout the area and clearly control the distribution and shapes of the basins. Block faulting apparently broke up the periphery of the Sunda Shelf at the beginning of Tertiary time. The chief crude oil production in western Indonesia is from the regressive and deeper trasgressive sandstone series of Oligocene-Miocene age, except in East Kalimantan, where producing zones range from Eocene to Pliocene. Prospective areas have changed considerably since oil and gas in economic amount have been proved from an interbedded limestone formation of Tertiary age. Additional reserves are anticipated in stratigraphic traps. Oil and gas discoveries within deltaic sandstones, notably in East Kalimantan, have upgraded significantly the onshore and offshore potentials of the area. Carbonate rocks are becoming a prime objective in the search for oil, especially in the East Java—Madura basinal area. Although eastern Indonesia was chiefly the site of late Paleozoic and Mesozoic sedimentation, oil has been proved only within the strata of Tertiary age, notably in the Salawati basin. Of particular importance was the recognition of the tremendous potential that reefs, particularly Tertiary reefs, possess as hydrocarbon reservoirs. A similar basin and environmental model is anticipated for the Bintuni basin. Recent scientific cruises have indicated the presence of several potential basinal areas between the Sunda and Sahul Shelves. The sedimentary basins in Indonesia can be classified as arc-front, foreland, and deltaic basins.

Abstract Lower California is an unknown and untested oil province; no deep wells have been drilled in search of oil and the oil potentiality is not predictable from available information. Despite limited quantitative information, the geological evidence is definitely favorable in three distinctive areas: (1) the Sebastian Vizcaíno embayment, (2) the Eugenia Abreojos Province, and (3) the Iray Purísima region. No oil seepages have been found in the area that extends southward from 28° to 24° North Latitude. However, the thickness and type of sediments encountered and the structure are attractive for oil possibilities.

Abstract Oil fields of the world with recoverable reserves more than 500 million bbl and gas fields with reserves more than 3.5 Tcf are analyzed to determine what characteristics they have in common and, on the other hand, reasons why some of these fields have unusual characteristics. Giant hydrocarbon accumulations require that there be a giant trap, formed more or less concurrently with generation of the hydrocarbons from the organic source materials, and abundant source beds rich in organic matter. Marine sediments are dominant as source beds, but non-marine beds also preserved the organic materials which supplied the hydrocarbons to many giant fields. Although argillaceous sediments generally trapped more organic matter, carbonates also can be sources. The reservoir rocks of most giant fields are very porous and permeable, but there are notable exceptions; in the exceptions, total reservoir volume compensates for deficiency in reservoir quality. The reservoir rocks must be interconnected with channels of migration, or carrier beds, from the source beds. An effective seal must be present to prevent escape of hydrocarbons from the reservoir; the most efficient seal is provided by evaporites. Evaporites, in addition to sealing many important reservoirs, also may be the primary agent responsible for the development of the structures of many large fields— generally through either diapirism or décollement. Un-conformities have had an important role in some fields in aiding trap development and in bringing carrier beds into juxtaposition with others through which hydrocarbons may migrate. Giant traps caused by lateral facies changes, changes in reservoir matrix, postdepositional dia-genetic changes, and paleogeomorphic factors are few, but their absence does not mean that they are scarce; most exploration has been directed toward the structural types of trap, and searches for other types of traps have been few. Though most giant-field reserves are in Mesozoic and Tertiary rocks, there is no preferred age of source beds or reservoir rocks. The important factor is the time when, during the sedimentational cycle of a basin, the largest amounts of organic matter were buried and preserved. It makes little difference if this time was Cambrian or Pleistocene. Higher than normal geothermal gradients probably resulted in greater efficiency of hydrocarbon generation in certain basins. The sources of gas include the same types of materials that generated liquid oil, but they also include other materials of vegetal origin that do not contribute significantly to the formation of oil. Hence gas can be derived from a greater variety of source materials. Volumes of gas and oil generally are inversely related to increasing depth. Downward increase of temperature results in the "phasing out" of oil and the dominance of gas. Liquids disappear and are replaced by gas in the range 5,640-8,380 m (18,500 27,500 ft); the actual depth depends on the geothermal gradient present in the field under study. The depths given are not necessarily the present overburden thicknesses; many reservoirs are affected by weight of overburden of an earlier geologic time, which today may no long exist because of subsequent uplift and erosion. We present for consideration a basin classification having different spatial relations with ciatons and continental borders, and having different evolutionary development. The type of basin having the largest number of giant fields is the basin which is, or was, a downwarp toward an oceanic area. Intermontane basins, developed either as geosynclinal-type basins between rising geanticlines or in transverse downwarps, generally are smaller in size, but many such basins contain clusters of very large fields. Interior cratonic areas exposed to long periods of erosion and tectonic and/or epeirogenic activity also contain numerous large fields, but a smaller percentage of giant fields. Giant hydrocarbon accumulations require that there be a giant trap, formed more or less concurrently with generation of the hydrocarbons from the organic source materials, and abundant source beds rich in organic matter. Marine sediments are dominant as source beds, but non-marine beds also preserved the organic materials which supplied the hydrocarbons to many giant fields. Although argillaceous sediments generally trapped more organic matter, carbonates also can be sources. During the past 15 years, deeper drilling and exploration of new basins have led to the discovery of an increasing percentage of Mesozoic vs. Tertiary giant fields. The greatest future prospects for discovery of giant fields are (1) in the continental shelves of the world; (2) onshore in Asia; (3) unexplored basins containing mainly continental strata; and (4) all areas of the world where deliberate exploration for obscure traps has not been carried out—i.e., stratigraphic, unconformity-associated, and paleogeomorphic traps.

Abstract Discoveries of natural gas in Alaska have resulted from the search for oil, which has continued intermittently since about 1898. In northern Alaska two gas fields and two prospective gas fields, as well as two oil fields and one prospective oil field, have been discovered in Mesozoic rocks. All other discoveries have been made in Tertiary rocks along the southern coast of Alaska. Except for a small shallow oil field at Katalla, all of these discoveries have been in the Cook Inlet subprovince, which contains a fully developed major oil field, an undeveloped oil field, two major natural gas fields, eight unevaluated or smaller gas fields, and important gas prospects. Alaska is grossly similar in geology, as well as in physiography, to the western part of the conterminous United States and western Canada. During Paleozoic and early Mesozoic time, it was a part of the Cordilleran geosyncline—the eugeosynclinal part over southern Alaska and the miogeosynclinal part over northern Alaska. In mid-Mesozoic time the bedrock surface of Alaska was warped into alternating geanticlines and geosynclines. The sediments that filled the geosynclines were predominantly clastic, and for the most part graywacke assemblages. Alaska has been largely emergent since the end of the Cretaceous Period. During the Tertiary Period, local downwarping formed several elongate basins that were filled with clastic sediments. Most of these were nonmarine, but marine invasions entered a few marginal basins at the southern and northern borders of Alaska. Areas considered for gas and oil possibilities include the Alaska Peninsula-Cook Inlet province, the Bristol Bay Tertiary province, the Pacific-margin Tertiary province, and the Bering Sea shelf in southern Alaska; the Arctic Slope province across northern Alaska; and the Yukon-Koyukuk and Yukon-Porcupine provinces of western and eastern interior Alaska, respectively. The Alaska Peninsula-Cook Inlet province consists of a long, narrow prism (more than 900 mi long and 5 to 60 mi wide) of slightly to moderately deformed late Mesozoic marine clastic rocks, whose composite thickness exceeds 30,000 ft. In the Cook Inlet subprovince, coal-bearing nonmarine, slightly to moderately deformed, Tertiary clastic rocks, whose composite thickness may exceed 25,000 ft, overlie the Mesozoic rocks. The Mesozoic rocks contain several gas and oil seeps and have produced shows of oil and gas in test wells, but no commercial production has been found. The Tertiary rocks contain the major known reserves and the only significant production of oil and gas in Alaska. The area considered to have petroleum possibilities is 5-60 mi wide and about 250 mi long. The Bristol Bay Tertiary province, about 250 mi long and as much as 30 or more miles wide, is underlain by poorly exposed marine and nonmarine Tertiary clastic rocks. No indications of petroleum have been reported, and three test wells were dry. Rocks of the Pacific-margin Tertiary province crop out along the coast from Icy Point in southeastern Alaska to Chirikof Island (southwest of Kodiak Island), and these rocks may extend offshore to fringe the entire Pacific margin and form a belt roughly 40,000 sq mi in area. Many oil seeps, gas seeps, and petroliferous beds occur in the Katalla-Yakataga area. Exploration has been without success, however, probably because of complex structure of asymmetric folds and north-dipping thrust faults, and the failure to find suitable reservoir rocks. Though little is known of the geology of the Bering Sea shelf, it should be considered for petroleum possibilities in view of its large size, possible extension across it of belts of late Mesozoic rocks, and possible Tertiary deposition along its outer edge. Except for the southern part of the Brooks Range, most of the Arctic Slope province, an area of about 125,000 sq mi, may be considered potentially petroliferous. It is underlain by calcareous and clastic miogeosynclinal rocks of Paleozoic and early Mesozoic ages and by clastic rocks of middle and late Mesozoic age. Structure, complex in the Brooks Range, decreases in complexity northward across the foothill belts and the Arctic Coastal Plain. Significant gas and oil reserves have been found in Cretaceous rocks. Gently deformed marine and nonmarine clastic Tertiary rocks crop out in limited areas in the northeastern part of the province. The Yukon-Koyukuk province in west-central Alaska has an area of about 85,000 sq mi. Large parts of the province are underlain by unmetamorphosed mid-Cretaceous rocks that may be locally petroliferous, although the great bulk of these rocks appear to be high-rank graywacke with poor reservoir characteristics. The Yukon-Porcupine province, an area of 15,000 sq mi, is underlain by a thick sequence of moderately deformed, largely unmetamorphosed Paleozoic and Mesozoic strata. Though no real evaluation can be made until test wells are drilled, the province appears to be relatively the most promising area in central Alaska.

Abstract Discoveries of natural gas in Alaska have resulted from the search for oil, which has continued intermittently since about 1898. In northern Alaska two gas fields and two prospective gas fields, as well as two oil fields and one prospective oil field, have been discovered in Mesozoic rocks. All other discoveries have been made in Tertiary rocks along the southern coast of Alaska. Except for a small shallow oil field at Katalla, all of these discoveries have been in the Cook Inlet subprovince, which contains a fully developed major oil field, an undeveloped oil field, two major natural gas fields, eight unevaluated or smaller gas fields, and important gas prospects. Alaska is grossly similar in geology, as well as in physiography, to the western part of the conterminous United States and western Canada. During Paleozoic and early Mesozoic time, it was a part of the Cordilleran geosyncline—the eugeosynclinal part over southern Alaska and the miogeosynclinal part over northern Alaska. In mid-Mesozoic time the bedrock surface of Alaska was warped into alternating geanticlines and geosynclines. The sediments that filled the geosynclines were predominantly clastic, and for the most part graywacke assemblages. Alaska has been largely emergent since the end of the Cretaceous Period. During the Tertiary Period, local downwarping formed several elongate basins that were filled with clastic sediments. Most of these were nonmarine, but marine invasions entered a few marginal basins at the southern and northern borders of Alaska. Areas considered for gas and oil possibilities include the Alaska Peninsula-Cook Inlet province, the Bristol Bay Tertiary province, the Pacific-margin Tertiary province, and the Bering Sea shelf in southern Alaska; the Arctic Slope province across northern Alaska; and the Yukon-Koyukuk and Yukon-Porcupine provinces of western and eastern interior Alaska, respectively. The Alaska Peninsula-Cook Inlet province consists of a long, narrow prism (more than 900 mi long and 5 to 60 mi wide) of slightly to moderately deformed late Mesozoic marine clastic rocks, whose composite thickness exceeds 30,000 ft. In the Cook Inlet subprovince, coal-bearing nonmarine, slightly to moderately deformed, Tertiary clastic rocks, whose composite thickness may exceed 25,000 ft, overlie the Mesozoic rocks. The Mesozoic rocks contain several gas and oil seeps and have produced shows of oil and gas in test wells, but no commercial production has been found. The Tertiary rocks contain the major known reserves and the only significant production of oil and gas in Alaska. The area considered to have petroleum possibilities is 5-60 mi wide and about 250 mi long. The Bristol Bay Tertiary province, about 250 mi long and as much as 30 or more miles wide, is underlain by poorly exposed marine and nonmarine Tertiary clastic rocks. No indications of petroleum have been reported, and three test wells were dry. Rocks of the Pacific-margin Tertiary province crop out along the coast from Icy Point in southeastern Alaska to Chirikof Island (southwest of Kodiak Island), and these rocks may extend offshore to fringe the entire Pacific margin and form a belt roughly 40,000 sq mi in area. Many oil seeps, gas seeps, and petroliferous beds occur in the Katalla-Yakataga area. Exploration has been without success, however, probably because of complex structure of asymmetric folds and north-dipping thrust faults, and the failure to find suitable reservoir rocks. Though little is known of the geology of the Bering Sea shelf, it should be considered for petroleum possibilities in view of its large size, possible extension across it of belts of late Mesozoic rocks, and possible Tertiary deposition along its outer edge. Except for the southern part of the Brooks Range, most of the Arctic Slope province, an area of about 125,000 sq mi, may be considered potentially petroliferous. It is underlain by calcareous and clastic miogeosynclinal rocks of Paleozoic and early Mesozoic ages and by clastic rocks of middle and late Mesozoic age. Structure, complex in the Brooks Range, decreases in complexity northward across the foothill belts and the Arctic Coastal Plain. Significant gas and oil reserves have been found in Cretaceous rocks. Gently deformed marine and nonmarine clastic Tertiary rocks crop out in limited areas in the northeastern part of the province. The Yukon-Koyukuk province in west-central Alaska has an area of about 85,000 sq mi. Large parts of the province are underlain by unmetamorphosed mid-Cretaceous rocks that may be locally petroliferous, although the great bulk of these rocks appear to be high-rank graywacke with poor reservoir characteristics. The Yukon-Porcupine province, an area of 15,000 sq mi, is underlain by a thick sequence of moderately deformed, largely unmetamorphosed Paleozoic and Mesozoic strata. Though no real evaluation can be made until test wells are drilled, the province appears to be relatively the most promising area in central Alaska.