Analysis of Oil and Gas Accumulation Rule in Lishu Fault Depression and the Key Factors

Through fine structure interpretation based on three-dimensional seismics,the author has again divided tectonic framework of Lishu fault depression and analyzed basic mode governing oil and gas accumulation and the key factors.Dividing deep,intermediate and superficial sections into three reservoir combinations,there are two accumulation models: one model which is auto-product and auto-reservoir migrates toward the sides;the other which is lower product and upside reservoir migrates vertically.Dividing Lishu fault depression into six tectonic elements including Maochengzi and Xiaochengzi slope belts,Bawu upwarping zone,Xiaokuan,Shangshutai and Shuanglong depressions,it is believed that structure(fault-nose) reservoir occurs in slope belt;lithologic reservoir in main trough fault;structure reservoir,lithologic reservoir,buried hill reservoir or stratigraphic reservoir in central uplift zone;structure-lithologic reservoir in secondary trough fault.It is also found that the effective reservoir and conservation condition of Bawu upwarping zone contributes to the accumulation;oil and gas blocked off by unconformities and mud rock in Maochengzi and Xiaochengzi slope belts to the accumulation;effective reservoir and trap of Shangshutai depression slope zone to the accumulation.