ABSTRACT: The Influence of Pressure on Petroleum Generation and Maturation as Suggested by Hydrous Pyrolysis
L. C. Price, L. M. Wenger
Because fluid pressures in sedimentary basins fluctuate over geologic time, their effect on hydrocarbon (HC) generation and maturation is difficult to determine and is a source of much controversy. Assuming that hydrous pyrolysis reactions simulate HC generation and maturation in nature, then laboratory experiments of such reactions offer an excellent way to study any possible influence of pressure. Such experiments carried out on shale of the Permian Phosphoria Formation (type II-S organic matter) at different constant temperatures demonstrate that increasing pressure significantly retards both HC generation and maturation reactions. This conclusion is derived from quantitative analysis of the generated C1-C4 HC gases, C4-C7 ga oline-range HCs, and C8+, bitumen; pyrolysis-gas chromatography of asphaltenes; Rock-Eval and pyrolysis-gas chromatography of the Soxhlet-extracted, reacted rock; and many detailed, qualitative gas chromatographic and mass spectrometric analyses of the various generated products. If hydrous pyrolysis does mimic natural HC generation and maturation, then these data have relevance to HC generation, accumulation, and destruction in nature, specifically regarding the influence of abnormal fluid pressures and the factors that create and disrupt such pressures.
AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990