Conditions for hydrocarbon reservoirs formation of lithologic trap inwall- corner-type steep slope belt: A case on the Paleogene Dongying Formation of BZ3 block in middle part of Shinan steep slope belt,Bohai Bay Basin
Yang Bo, Xu Changgui, Niu Chengmin
Bohai Oilfield Exploration and Development Research Institute， China National Offshore Oilfield Corporation Limited-Tianjin，Tanggu 300452，Tianjin
Abstract：The western steep slope belt of BZ3 block is located in the middle part of Shinan steep slope belt，Bozhong Sag of Bohai Bay Basin.It was formed at the joint zone of Shijiutuo Uplift and its pitching end is a complex wall-corner-type steep slope with several step-fault zones formed by two intersected faults of Shinan 1 and Shinan 2.According to the theories of high resolution sequence stratigraphy，there are three base level cycles of 4-5 th order in the lower submember of Member 2 of Dongying Formation(lower Ed2)，and the upper and lower parts of the base level cycle controlled the formation of the braided fluvial delta.By analyses of formation mechanism and structural evolution of wall-corner-type steep slope，the ancient tectonic background was favorable for the water convergence in the lower Ed2，there were multi-stage braided fluvial delta deposits along the down-throw side of the boundary fault from the provenance of Shijiutuo Uplift.Then the sandbody boundary is portrayed by the seismic phase，seismic attributes and seismic inversion methods.The study result shows that the 1st and 2nd base level cycles are favorable for sandbody enrichment，which pinchout to southwest and form lithological traps.They have big trap area and good reservoir-seal conditions.Because these traps were formed attaching to the boundary fault，facing to the western subsag of Bozhong Sag and relying on the Shijiutuo Uplift，the accumulation condition is favorable，and will be the exploration targets of lithological traps in the Bozhong Sag.
. Conditions for hydrocarbon reservoirs formation of lithologic trap inwall- corner-type steep slope belt: A case on the Paleogene Dongying Formation of BZ3 block in middle part of Shinan steep slope belt,Bohai Bay Basin[J]. JOPC, 2011, 13(4): 434-442.
