Characterization of Macro-Micro Heterogeneity in Shale Reservoirs Based on Full-Diameter Core CT Scanning─A Case Study of Jurassic Lianggaoshan Formation Shale in Well Ping’an 3, Sichuan Basin

Abstract Continental shale reservoirs exhibit strong vertical heterogeneity in lamellar fracture development and pore–fracture systems, yet continuous core-scale characterization remains limited. This study presents a hierarchical characterization of four Jurassic Lianggaoshan Formation intervals from Well Ping’an 3, Sichuan Basin, based on full-diameter core computed tomography (CT) scanning combined with convolutional neural network (CNN)-based image segmentation, 3D reconstruction, and pore-scale seepage simulation. The results show that (1) reservoir heterogeneity increases vertically from siltstone to shale intervals, with average lamina/interlayer volume percentages of 11.12%–12.81% and lamina densities of 130–2185 strips/m in shale intervals; (2) lamellar fractures predominantly develop along bedding interfaces, with average fracture porosity of 0.4%–0.7% and strong vertical heterogeneity; (3) within the CT resolution limit, pore–fracture seepage assemblages are classified into pore-dominated, transitional, and fracture-dominated types, with reservoir connectivity jointly influenced by fracture density, aperture, and matrix pore coupling. This study provides a continuous macro–micro integrated characterization workflow for micron-scale pore–fracture features at the CT-resolvable scale (>150 μm), bridging the gap between plug-scale microanalysis and interval-scale geological evaluation. The nanopore system requires complementary methods such as scanning electron microscopy (SEM) and mercury intrusion capillary pressure (MICP) for full characterization.