Effects of Fracture Formation Stage on Shale Gas Preservation Conditions and Enrichment in Complex Structural Areas in the Southern Sichuan Basin, China

Fractures have significantly impacted the preservation, enrichment, and productivity of shale gas in Longmaxi Formation complex structural area southern Sichuan Basin. Based on outcrop, core, imaging logging, inclusion analysis, acoustic emission experiments, burial thermal evolution history data, formation stage, preservation conditions fractures were comprehensively studied. Shear are main features tectonic origin characterized by small widths, wide spacing, high filling degrees. The can be divided into three groups terms their stage. first-stage formed middle-late period Yanshanian movement (86.2–68.5 Ma), when palaeotectonic stress was 68.33–71.82 MPa; homogenization temperature fluid inclusions corresponding fracture fillings is 150–178°C. second-stage at end -early Himalayan (68.5–35.2 85.2–100.5 123–148°C. third-stage during (35.2–0 55.6–63.8 scarce these fractures, but measured 90–110°C. Shale affected maximum horizontal crustal stress, fault scale, depth, pressure coefficient, etc. Three types favourable identified. Type I target low slope middle syncline, which occurs more than 2.0 km from fault. research results guiding significance for evaluation deep study similar areas.