Control of Complex Structural Deformation and Fractures on Shale Gas Enrichment in Southern Sichuan Basin, China

The research on the differential enrichment mechanism of shale gas under the complex tectonic background is a key problem to be solved currently. The southern Sichuan Basin is taken as the research object, and the geochemical experiment, overburden porosity and permeability experiments, direction test of a ground stress experiment, and seismic interpretation method are used to clarify the structural deformation characteristics and fault characteristics under different structural styles and structural parts and summarize the differences of shale gas preservation critical conditions in different structural units. The results show that (1) the fracture level controls the boundary and scale of shale gas reservoirs. The primary/secondary faults within 3 km greatly influence shale gas reservoirs, and the complex combination of fault systems will cause obvious indigenous damage to shale gas reservoirs. (2) The angle between the fault strike and the direction of the maximum principal stress determines the sealing of the fault, and the angle greater than 45 degrees can effectively inhibit the loss of shale gas. (3) The coupling effect of burial depth and dip angle controls the migration of shale gas along the strata. The greater the burial depth and the smaller the dip angle, the better the page sealing and preservation conditions. Based on the enrichment factors of shale gas in different tectonic units, three enrichment models of syncline, anticline, and slope are established, and the enrichment favorable areas are optimized, which has important guiding significance for shale gas exploration and development in Sichuan Basin.