Geological Structure And Shale Fracture Characteristics In Xuyong Areas,South Sichuan

The geological structure and shale fracture characteristics are the one of the important indicators to determine whether the shale gas reservoir has mining value.Based on the study of the geological structure characteristics,superimposed transformation rules and structure formation mechanism in the Xuyong area,southern Sichuan,the fracture deformation is systematically analyzed The characteristics and development rules further discuss the control effect of tectonic action on the development of shale fractures,and predict the shale fractures in the study area.The study shows that the stratum distribution and structural morphology in Xuyong area are controlled by NEE and NS.In the same direction,the folds developed in the same direction,and the folds developed in a barrier combination,and the near NS folds superimposed on the NEE folds to form secondary dome structures,basin structures,and saddle structures,and the fold deformation showed "South "Strong north weak,west strong east weak" characteristics.The fault structure is dominated by reverse faults,which are mainly NEE-near EW direction and NNW-near NS direction,and the multicutting of NNW-near NS faults breaks the development of NEE-near EW faults.According to the quantitative evaluation of structural deformation characteristics,fold structure curvature analysis and fault structure fractal analysis,the study area can be divided into folds of western strong superimposed structural deformation,northern weak basin-shaped deformation,mid saddle-shaped medium deformation,mid weak basin-shaped deformation,southern strong deformation,eastern strong deformation and eastern weak deformation zone of 7 structural divisions.The structure of the study area mainly experienced the compression of NNW-SSE direction deformation stage in the Indo-chinese epoch,the reconstruction of NS direction compression stage in the early Yanshanian,the tectonic compression of near EW direction and superimposed transformation stage in the late Yanshanian,and the weak compression of NS and reconstruction in the Himalayan period Stage 4 tectonic evolution stages.The fractures in the shale in the study area are consistent with the orientations in other stratas.There are four sets of dominant fractures in the NNE direction,NNW direction,NE direction and NWW direction,of which NE direction and NWW direction are the main ones.Shale fractures in the Longmaxi Formation are well developed,with three types of fractures including bedding fractures,high-angle oblique fractures and vertical fractures,and the vertical fractures in the Longmaxi Formation LM1-LM3 are most developed.The multifractual spectrum and singular spectrum of fractures have a good characterization of the complexity and heterogeneity of fracture distribution.Through the quantitative evaluation of the multifractual spectrum and singular spectrum of reservoirs,the distribution of fractured dense areas in the study area accounts for more than the sparse areas,the fracture heterogeneity is weak,and the fractures are more developed.In the Indo-Chinese epoch,the compression of near NS direction makes the NNE-direction and NNN-direction fractures generally develop near the NEE-direction fold core,while the compression of Yanshanian near EW direction and strong brittle deformation of the strata uplift have resulted in the development of NWW and NEdirectional fractures throughout the region..Close to the fold core and complex structure development area,fractures are densely developed and secondary structures are developed.In the fold's lims and simple structure area,the fractures are sparsely developed and the shale layer is intact.The paper has 98 pictures,21 tables,and 146 references.