PETROLEUM GENERATION, MIGRATION AND ACCUMULATION IN YINGER DEPRESSION, THE EASTERN JIUQUAN BASIN
Chen Jian-ping (Research Institute of Petroleum Exploration and Development, CNPC, Beijing, 100083)
There are two strata series of the Lower-middle Jurassic and the Lower Cretaceous potential source rock in Yinger depression, the eastern Jiuquan basin. Organic matter in the Lower Zhonggou formation, Lower Cretaceous, is the best in abundance and type and is low in maturity. Matured lower-middle Jurassic source rock is a very important potential source rock. Biomarkers in the two strata are quite different. Oils in Jurassic and Cretaceous reservoirs are two kinds of crude oils and derived respectively from its own potential source rock without long distance migration. Three abnormally overpressured zones occur in Yinger depression and strongly control the petroleum migration and accumulation. The difference in tectonic location results the different pattern of petroleum occurrence and accumulation between the eastern and the western Jiuquan basin. Oil and gas from the Lower-middle Jurassic source rocks are controlled by the faults trended in NNE and by the abnormally overpressured zones. The prospect of oil and gas exploration is better in the eastern region than in the western region divided by Heiliang fault, so that ChangshalingXiaheqing low uplift is the most potential area. The generation and accumulation of oil and gas from the Lower Cretaceous potential source rock are much favorable in the southern than in the northern in Yinger depression. This paper discusses the petroleum generation, migration and accumulation in Yinger depression, the eastern Jiuquan basin and makes a comparison with the western Jiuquan basin.