Developmental mechanism of advantageous Xixiangchi Group reservoirs in Leshan–Longnüsi palaeohigh

The Leshan–Longnüsi palaeohigh in the Sichuan Basin controlled by basement uplift underwent multistage or multicyclic syndepositional uplifting and denudation uplifting during evolvement. Carbonate reservoirs are developed in the Lower Upper Cambrian Xixiangchi Group in this area. The reservoirs are compact and have low matrix porosity and permeability. But porous and dissolution layers exist locally, and porous layers commonly occur in pinhole and coarse textural dolomites. Fracture growth may improve the reservoir penetration conditions. Karstification in the depositional and weathering stages is the main diagenesis of the reservoirs. The main developmental zones of excellent reservoirs are palaeo-karst crust of weathering and the area where karst ramps and structural fractures coexist.