Main Controlling Factors and Favorable Zone Selection for Thin Carbonate Reservoirs-the Case of Permian Qixia Formation Gas Reservoir in Gaoshiti Block

In recent years, the Permian Qixia Formation in the Gaoshiti Block of the central Sichuan Basin has frequently yielded high-productivity industrial gas wells, establishing it as a key target for exploration and development. However, challenges such as strong heterogeneity in thin layers, unclear distribution patterns, and undefined controlling factors of the Qixia Formation reservoirs have constrained further development planning and deployment. This study employed core observation, microscopic analysis, logging, and seismic data to investigate reservoir characteristics. Results indicate that the Qixia Formation reservoirs are predominantly composed of crystalline dolomite, with reservoir spaces dominated by intercrystalline pores, intercrystalline dissolution pores, and caves, locally enhanced by fractures. Reservoir development is primarily controlled by high-energy sedimentary facies zones, constructive diagenesis, and fault systems. The reservoirs exhibit poor continuity in the north-south direction but significantly better continuity in the east-west direction, with faults substantially improving seepage capacity. The study established a composite reservoir control theory of “sedimentation determines the framework, diagenesis controls physical properties, and fractures optimize seepage,” which strongly supports the identification and delineation of favorable zones for gas reservoir development in the Qixia Formation and provides a novel approach for evaluating similar carbonate reservoirs.