The Formation Of Primary Oil And Gas Pools Orignated From Carboniferous And Permian In Bohai Bay Basin

Through thirty years petroleum exploration in Bohai Bay Basin, oil reserves that have been found mainly exist in Neogene and Eogene buried less than 3500m deep. According to the resoults of second national oil resource estimation, the oil resource formed in Bohai Bay Basin is 18.8 billion tons and the gas resource is 2.12×1012m3,which means there are still prolific resources. So the further oil exploration should focus on new series and strata, besides on Neogene and Eogene. The discovery of Suqiao,Koucun and Konggu4 Oilfield indicates nice potentials of Upper Paleozoic.After the source rocks had deposited in Paleozoic area, the Bohai Bay Basin had undergone several complicated tectonic changes, and the coal-measure source rocks experienced such actions as inhomogeneous uplift, deformation, burial, and magma effect resulting in a discontinuity and in stages for the generation and evolution of hydrocarbon. Based on coal-measure resource rock estimation standards, Carboniferous and Shanxi formation reach good-better resource rock standard. The kerogen type in samples is sapropelic mainly and is up to high maturation degree. Hydrocarbon regenerations exist obivious lagging. The five pools that originated from the Upper Paleozoic coal-measure source rocks are analyzed in details. Based on analysis of geological, seimic and logging data, their tectonic evolutions are reconstructed using balanced cross section technology. According to fluid inclusion data their reservoir filling histories are conformed. In the light of burial history, thermal history and hydrocarbon generation history reconstruction, the petroleum pool-forming simulations are done using basin simulation technology. It is concluded that the main controlling factors of pool-forming process include hydrocarbon generation intensity and paleostructure. Hydrocarbon generations control the distributions of the pools and the areas with high secondary generation intensity since Cenozoic are the main distribution area of the pools. Long-term paleostructures in basin or depression are suitable for hydrocarbon accumulations. The paper summarizes four formation medels that include Suqiao-Wenan-type, Wenliu-type, Wumaying-type and Wangjiahe-type. Based above discussions the favorable places for further exporalation are proposed...