Difference And Comprehensive Evaluation Of Shale Gas Preservation Conditions Of Longmaxi Formation In Changning,South Sichuan

In recent years,with the deepening of deep marine shale gas exploration,shale gas exploitation in Sichuan Basin has achieved good results.However,as a region with complex tectonic conditions,the shale gas content of Longmaxi Formation in Changning area is quite different in different regions.In this paper,the shale of Longmaxi Formation in Changning area of South Sichuan Basin is taken as the research object.Through experiments and summary analysis,the differences of material basis and preservation conditions in different tectonic units are obtained,and the influence of preservation conditions on gas content is summarized.The evaluation criteria and evaluation results of preservation conditions in different blocks of Changning area are summarized.The results show that the shale of Longmaxi Formation in Changning area has good material basis,and has the characteristics of ’ high TOC,high gas content and high evolution ’.The hydrocarbon generation conditions are superior,and the reservoir properties of low porosity and low permeability are presented.Complex tectonic evolution and tectonic conditions play a key role in controlling the accumulation and dispersion of shale gas in Longmaxi Formation.The activity period and intensity of faults and the complexity of stacking have a great influence on the preservation conditions of reservoirs.The closer the well with multi-stage fault activity is to the large fault,the more complex the fault stacking is,and the gas content is generally poor.The Longmaxi Formation shale in Changning area has good roof and floor conditions and self-sealing.According to the classification of tectonic conditions,the study area is divided into eight preservation condition evaluation units : Tiangongtang area,Loudong anticline,Shuanglong syncline,Luochang syncline,Jianwu syncline,Ning 233 well area,Gaomuding area and Changning anticline erosion area.Through the comparative analysis of the differences of preservation conditions and gas content of different tectonic units,the evaluation criteria of preservation conditions are established,and the corresponding evaluation results are obtained : the preservation conditions of shale gas in Changning area are generally medium-good,but the differences of each tectonic unit are large;the preservation conditions of Jianwu syncline and Ning 233 well area in Changning area are better,the preservation conditions of Tiangongtang anticline and Shuanglongluochang syncline are medium,and the preservation conditions of Shuanglong,Luochang syncline and Changning anticline are poor.