Hydrocarbon Preservation Conditions and Evaluation of the Maokou Formation in the Leshan-Yibin Area, Southern Sichuan Basin, China

The southern Sichuan Basin is rich in natural gas and is a key area for hydrocarbon exploration. Due to multi-phase tectonic movements, structural characteristics and preservation conditions are critical for gas accumulation. Focusing on the Middle Permian Maokou Formation in the LY area, this study analyzes the regional and local structural framework to assess structural features and their impact on preservation conditions. Using indicators such as deformation intensity, caprock properties, formation water chemistry, and pressure coefficients, an evaluation system is established to identify favorable exploration zones. Results show that the LY area lies in the southern Sichuan low-steep structural belt, dominated by NE- and NWW-trending systems. Structural styles include back-thrust combinations, fault-propagation folds, and pop-up structures. Back-thrust and pop-up structures severely compromise preservation, while fault-propagation folds with small blind faults favor accumulation. Favorable preservation areas are mainly in Ziliujing and Kongtan, characterized by stable geology, thick caprocks, and younger exposed strata, indicating good sealing. Overall, the Maokou Formation exhibits favorable hydrocarbon accumulation conditions.