--> Abstract: Oil and Gas Systems of Ordos Basin in China, by Guoli Wang, Yongpei Wei, and Yi Wang; #90039 (2005)

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Oil and Gas Systems of Ordos Basin in China

Guoli Wang1, Yongpei Wei2, and Yi Wang2
1 China Petroleum & Chemical Corporation (Sinopec Corp.), Beijing, China
2 Exploration & Production Research Institute, SINOPEC, Beijing, China, Beijing, China

Ordos basin, the second largest sedimentary basin located in the central part of China, was transformed into westward declination monocline with only about 2-3° dip angle in later Cretaceous where a large amount of oil and gas resources have been found. It is concluded that the tectonic evolution in Ordos basin can be divided as the following several stages: rift, composite craton depression, large inland depression and margional faulted depression. This unique structural evolution of the basin leads to the relative independent oil and gas systems. As a result, mesozoic oil system and paleozoic gas system distribute in the southern and north-central part of the basin respectively. The mesozoic oil system distributes around the hydrocarbon-generating center of Yanchang formation in Triassic, whose source rock is lacustrine shale rock which enter the peak of hydrocarbon generation and expulsion in later cretaceous and tertiary, the key moment of accumulating oil in the triassic and jurassic sandstones in the south-central basin. Upper paleozoic gas system, controlled by north-south delta sedimentary bodies, distributes in the northern basin with the carboniferous-permian coal series source rocks reaching the generating hydrocarbon peak from later jurassic to early cretaceous. It has been proved that the permian distributary channel rocks reformation and the cap rocks sealing ability formation also occurre in this period. The lower paleozoic gas system, controlled by the paleo carst at the top of Ordivician, distributes in the northern central basin, in which carboniferous-permian coal series and marine carbonate rocks in over maturation stage reached the peak of generating and expulsing hydrocarbon in the middle age of Yanshan movement. It is concluded that over mature gases from coal series and carbonate rocks migrated from upward and accumulated in the carst dolomite rocks with rich porosity and fracture.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005