Overpressure retardation of organic-matter maturation and petroleum generation: A case study from the Yinggehai and Qiongdongnan Basins, South China Sea
Journal Article
·
· AAPG Bulletin
OSTI ID:75400
- China Univ. of Geosciences, Wuhan (China)
- Institute of Petroleum Exploration and Development, Zhanjiang (China)
Three superimposed pressure systems developed in the Yinggehai Basin, South China Sea, as indicated by seismic data, well logs, and direct pressure measurements. The organic maturation profile is nonlinear, with three nonparallel segments that correspond to the shallow, normal-pressured system; the intermediate, overpressured system; and the deep, strongly overpressured system respectively. The intermediate and deep overpressured systems have abnormally low R{sub 0} gradients. The organic maturity of these overpressured rocks is significantly lower than the maturity of normal-pressured source rocks in nearby wells with similar thermal histories and does not math the thermal histories of the rocks. Such an organic maturity anomaly is distinctly different from those caused by variation in activation energies, conductivity contrasts, and hydrologic effects, and is confirmed to be the result of overpressure retardation. The degree to which the organi-matter maturation is retarded, expressed as the difference between predicted and measured vitrinite reflectance, increases exponentially with increasing fluid pressure, confirming that pressure increases the activation energies of organi-matter maturation reactions. Overpressure retardation has been proven to be conditional and quite important for clearly understanding petroleum generation, migration, and accumulation in overpressured sedimentary basins.
- OSTI ID:
- 75400
- Journal Information:
- AAPG Bulletin, Journal Name: AAPG Bulletin Journal Issue: 4 Vol. 79; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
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