EVOLUTION OF THE STRUCTURAL STRESS AND ITS FUNCTION DURING OIL/GAS ACCUMULATION IN BOHAI SEA

Bohai Sea area covers Bozhong depression and the offshore part of Xialiaohe, Jiyang, Huanghua depressions and Chengning uplift. Unique sediments and structures of Bohai Sea were formed under regional dynamic setting in Bohai Bay basin. Its evolution has experienced early rifting stage and late down warping depression since Cenozoic. The main faults are NE-NNE trending,and then are EW and NW trending in the area. Based on the direction, magnitude and deformation parameters of structural stress, four structural successions are recognized in the Bohai Sea that are Paleocene, Eocene-Oligocene, Miocene-early Pleistocene, late Pleistocene-present. These four structural stages played an important role in the fault-controlling oil/gas in the Bohai Sea, especially for NNE-NE trending faults. After strike-slip activities, NNE-NE trending faults induced local traps and unsubstantial structure zone, which provide pathways for oil/gas migrating or accumulating.