Coal is widely considered as a potential source for gas, but some coals may generate sizeable amounts of oil as well. Routine analytical tools, particularly pyrolysis, make possible geochemical logs that are the basis for screening samples and for interpreting other analyses. Among optical techniques, the major subjects of discussion concern the nature of amorphous organic matter, which may encompass different chemical types of kerogen, and the applicability of vitrinite reflectance techniques to type I and II kerogens. Following important advances in identification of biological markers in sediments and crude oils, these markers are used for oil-source rock correlation, and proposed for recostruction of depositional environment and subsequent thermal evolution. The importance of a hydrocarbon-phase migration is widely recognized. Overpressuring of pore fluids is mainly responsible for expulsion of petroleum. Geologic models of basin evolution (subsidence, compaction, thermal history) and geochemical models (hydrocarbon generation and migration) become progressively available.--Modified journal abstract.

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