Pressure Evolution Mechanism of Marine Shale Reservoirs and Shale Gas Accumulation Model: Evidence from Fluid Inclusions in the Wufeng–Longmaxi Formation in the Basin Margin Structural Transition Zone in Northern Guizhou Province, China

The Wufeng–Longmaxi Formation in northern Guizhou Province is the dominant shale gas exploration and development strata China. This study investigates Shixi Daozhen synclines, which are located basin margin transition zone. region experienced complex tectonic stages superimposed transformations, resulting heterogeneous preservation conditions reservoir pressure evolution different units of Formation. Based on fluid inclusion analysis, types filling were determined by laser Raman analysis homogenization temperature salinity tests. It was found that density paleopressure each stage then restored. results confirm that: ① Both syncline reservoirs two phases, early Yanshanian late Yanshanian–Himalayan, respectively. In course evolution, synclines relief to some extent during aforementioned key charging periods but remained overpressurized states overall; ② Formations characterized high-density methane inclusions; ③ differences structural conditions, mechanisms Shales important period revealed. Furthermore, differential enrichment accumulation models established named “facing thrust sealing type (Shixi syncline)” “reverse fault lateral blocking (Daozhen syncline)”.