Characteristics and Controlling Factors of Pore Structure and Connectivity in Wufeng–Longmaxi Shales of the Southern Sichuan Basin

ABSTRACT Pore connectivity (PC) links shale storage capacity to fluid accessibility, but its dependence on pore scale and wettability remains difficult to quantify. We investigated 31 Wufeng–Longmaxi (WF–LMX) shale samples from three wells in the southern Sichuan Basin using field‐emission scanning electron microscopy (FE‐SEM), CO 2 /N 2 adsorption, mercury intrusion capillary pressure (MICP), nuclear magnetic resonance (NMR), and spontaneous imbibition. Seven lithofacies were identified, and organic‐matter pores constitute the dominant observed pore population. Mesopores contribute most of the pore volume (PV), whereas micropores dominate the specific surface area (SSA). MICP‐derived permeability and tortuosity indicate restricted matrix connectivity. Joint NMR–MICP estimates yield PC ratios of 5.75%–23.35%, with greater accessibility in the larger pore‐size (PZ) intervals. Imbibition slopes are higher parallel to bedding than perpendicular to bedding, and n ‐decane generally gives higher slopes than deionized water. These fluids probe pore networks with different wetting characteristics under laboratory conditions. Connectivity depends on the combined effects of organic matter (OM) pore development, mineral‐framework support, pore‐throat geometry, spatial associations, and wettability. Bulk porosity, PV, and SSA alone provide incomplete predictions because they do not describe the continuity of transport pathways. The integrated approach distinguishes storage‐space abundance from fluid‐accessible pore networks while highlighting the method‐dependent nature of quantitative connectivity estimates.