HYDROCARBON ACCUMULATION CONDITIONS OF THE ORDOVICIAN BURIED HILLS IN THE SLOPE ZONE OF THE JIZHONG DEPRESSION

According to the firsthand data and new geological study, the structural framework and the forming condition of buried hill reservoirs are analysed at the slope zone in the Jizhong depression. The obverse and reverse normal fault forms the horst buried hill zone. The block buried hills zone is covered by the Carboniferous Permian strata, which have the pools conditions with the neosource paleosource and paleoreservoir mesoblocking. Source rocks are composed of the Carboniferous Permian coal bearing rocks and Paleogene mudstone. Unconformities, fractures and SW faults act as the oil gas channels. The development of reservoirs are controlled by dolomitization, karstification and fracturing. The Himalayan karstification results from the action between the dissoluble rocks and water induced by active faults. So the match between rocks with rich porosity, fractures and active faults is the key geological factor of the formation of the buried hills reservoir. The oil gas accumulation is influenced by reservoirs condition. The distribution of oil gas is controlled by long term active faults. Paleo weathered crust is not the unique factor to control the development of reservoirs. The evaluating about these buried hill reservoirs should link the structures with strata.