Complicated Fault Characterization and Its Influence on Shale Gas Preservation in the Southern Margin of the Sichuan Basin, China

Abstract The southern margin of the Sichuan Basin is characterized by strong structural deformation, complex fault structure styles and scales, multistaged geological evolution stages, which together have created various shale gas preservation conditions. Taking Jianwu (JW)–Luochang (LC)–Shuanglong (SL) synclines as an example, development characteristics Longmaxi Formation were studied based on fine seismic interpretation microscopic tests (rock acoustic emission experiments fracture-filling inclusion tests), effects stage, class scale, fracture degree conditions analysed. Basement-involved faults, detachment intraformational microfaults are mainly developed from southeast to northwest. These types affected JW Syncline in southeastern part, where faults bottom Cambrian Wufeng–Longmaxi Permian (Triassic). SL-LC region northwestern part dominated This NE-trending main control supplemented NW-trending, approximately EW-trending, SN-trending, other small-scale regulating faults. Fault can be divided into three corresponding early, middle, late Himalayan tectonic movements. In early a few EW-trending had little impact preservation. intermediate large number large-scale significantly impacted with high-filling degree, weak upwards penetration, relevant fractures, favourable for western northern parts I II low-filling large-scale, penetration related unfavourable During SN- NW-trending strike-slip reverse developed, shear zones formed near producing research has clarified characterization method stages established influence preservation, important reference value exploration evaluation reserves regions.