Mechanisms And Models Of Deep Tight Sandstone Gas Accumulation In The Lishu Fault Depression,south Songliao Basin

Deep oil and gas resources in the Lishu Fault Depression(LFD)in the southern part of Songliao Basin have significant potential.However,due to the development of faults,interbedded layers and tight reservoirs,the mechanism of deep gas accumulation is still clear.In order to promote the exploration and development of deep tight gas in the LFD,the tight gas reservoir types,the gas accumulation mechanisms and the accumulation mode were studied in this thesis.Burial,thermal and hydrocarbon generation history of 12 wells in different regions of the LFD were simulated to study the gas generation center distribution.Porosity evolution process of the Ying-1 and Sha-2 Members in the LFD were confirmed.Based on petrographic and microthermometry of fluid inclusions,the oil and gas was found to charge in the Quantou period.The critical porosity of the Ying-1 and Sha-2 Members are8% and 6%,respectively.The tight gas types can be determined by coupling the porosity evolution and gas charge history.The Sha-2 Member is determined to be the “gas accumulation after reservoir tight",while the Ying-1 Member is the "gas accumulation before reservoir tight".Deep tight sandstone gas accumulation of the LFD is primarily controlled by factors including source rocks,paleostructure,pososity and preservation.In addition,the favorable regions of tight gas were predicted by matching the factors.Two accumulation mechanisms and modes of different types of tight gas reservoirs in the LFD were established.one is the LS1 mode with abnormal pressure as the charge mechanism,the other is the L8 mode with buoyancy as the accumulation mechanisms.Therefore,the processes of hydrocarbon charge can be realized.