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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 49 (1965)

Issue: 1. (January)

First Page: 114

Last Page: 114

Title: Petroleum Evolution: Progress and Problems: ABSTRACT

Author(s): Donald R. Baker

Article Type: Meeting abstract


The three-fold concept of the origin of hydrocarbons from organic materials in a source bed, their primary migration from the source rock during compaction, and their accumulation in traps, has been a part of geological philosophy since the early days of petroleum exploration. But except for adding some substantiating geologic evidence, it was not until the talents of chemists, biologists, and physicists were directed at these problems that new information with profound implications to concepts of petroleum evolution was obtained.

For example, studies of carbon isotopes in sediments and crude oils suggest that terrestrial plants, instead of marine plants and animals, may be the principal primary substance from which petroleum is derived. Further, the discovery of hydrocarbons in Recent sediments demonstrated the early formation and availability of petroliferous materials in depositional basins. However, characterization has revealed differences in the nature and abundance of hydrocarbons in Recent sediments compared with crudes and ancient rocks, indicating that modification and formation of hydrocarbons during diagenesis may be essential for the development of a source rock. Further, the distribution and character of hydrocarbons in ancient sediments indicate that some environments lead to the generation of mo e hydrocarbons than others, confirming the geologic opinion that there is a considerable range of variation in the nature of petroleum source beds. However, the recognition and evaluation of source rocks on the basis of absolute hydrocarbon content may be an oversimplification in that the hydrocarbons may not be indigenous, or may have formed subsequent to primary migration, or that some rocks may have yielded only a small part of their indigenous hydrocarbons. Finally, comparison of crude oil-source rock pairs indicates that the development of geochemical correlation techniques will be difficult and complicated by the likelihood that primary migration is inefficient, selective, and probably causes considerable modification of hydrocarbons en route.

Although contributions of non-geologists are essential, laboratory results will probably remain obscure unless interpreted in the light of a thorough knowledge of geological factors. The problem of petroleum evolution seems ripe for an integrated attack by geologists supported by physicists, chemists, biologists, and geochemists. The belief that an ultimate comprehension of petroleum evolution can only be developed by the interpretation of experimental and analytical data on a sound geological basis should be the underlying philosophy of future research on petroleum evolution.

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Copyright 1997 American Association of Petroleum Geologists