Fluid Geochemical Features and Preservation Conditions of Marine Stratum in Typical Structure of Jianghan Plain Area

Many scholars carried out large quantity of researches on oil and gas preservative conditions of marine carbonate rocks from the aspects of cap rocks, faults, formation water, hydrodynamic, and tectonism. This article gives dynamic evaluation on oil and gas preservative conditions of marine stratum in Jianghan (江汉) plain of multiphase tectonic disturbance from the view of paleofluid geochemistry. The conclusion shows that there mainly existed fluid filling of two periods in the reservoir of Lower-Middle Triassic to Permian. The fluid filled in the earlier period came from Lower Palaeozoic. The interchange of fluid in Lower-Middle Triassic to Permian suggested the oil and gas in Lower Palaeozoic had been broken up. The fluid filled in the later period (Lower-Middle Triassic to Permian) came from the same or adjacent strata and lacked anatectic fluidogenous features coming from Palaeozoic. With good preservative conditions of bulk fluid at the time, the fluid of Lower-Middle Triassic to Permian and that of Lower Palaeozoic did not connect with each other. However, the hydrocarbon generation peak of marine source rocks had passed or the paleo-oil and gas reservoirs had been destroyed at that time and the marine stratum of Palaeozoic to Triassic in the research area did not put out commercial oil and gas flow.