Reservoir Characteristics and Main Controlling Factors of the Permian Maokou Formation Carbonates in the Southern Sichuan Basin

ABSTRACT The carbonate reservoir of the Permian Maokou Formation (MF) in the southern Sichuan Basin represents a key target for regional hydrocarbon exploration. However, current understanding of its reservoir characteristics and controlling factors remains insufficient. To address this knowledge gap, a systematic study was conducted using a suite of analytical techniques, including scanning electron microscopy, 3D computed tomography scanning, nuclear magnetic resonance, whole‐core porosity and permeability measurements, carbon–oxygen isotope analysis, and rare‐earth element analysis. Research findings indicate that the reservoir lithology of the MF in southern Sichuan is relatively uniform, dominated by sparry bioclastic‐algal limestone with local development of micritic limestone. Microscopic analysis reveals that the reservoirs are dominated by dissolution pores, microfractures, and intercrystalline pores/fissures within the powder‐crystal calcite. The pore system in the study area is predominantly composed of micropores and mesopores, accompanied by minor macropores and nanopores. It features relatively low effective porosity and generally poor pore‐throat connectivity. Reservoir development is jointly controlled by Permian‐aged faults and epigenetic karstification. High‐quality reservoirs are mainly isolated fracture‐cavity reservoirs, primarily developed in paleo‐slopes and paleo‐highlands. This study can provide exploration guidance for analogous isolated or poorly connected carbonate reservoirs globally, offer reliable technical approaches for hydrocarbon production and development, and improve overall exploration efficiency.