Stress-dependent anisotropic flow in bedding-controlled shale: Computed tomography evidence of pore–fracture connectivity, triaxial fracturing, and imbibition effects

Fluid transport in shale reservoirs is strongly controlled by the organization and mechanical evolution of pore–fracture networks, which determine permeability anisotropy and flow efficiency under reservoir conditions. This study investigates the coupled structural and mechanical controls on stress-dependent anisotropic flow in Dongyuemiao shale cores from well X2 using bedding-parallel horizontal cores and bedding-perpendicular vertical cores. Unlike previous studies that mainly characterize fracture morphology or permeability evolution separately, this work integrates computed tomography reconstruction, porosity measurements, stress-dependent permeability tests, triaxial fracturing, and long-duration imbibition treatment to reveal the dynamic evolution of flow pathways. The results demonstrate that permeability anisotropy is governed primarily by directional fracture–pore connectivity rather than porosity alone. Horizontal cores generally exhibit higher permeability because bedding-parallel fractures and connected pathways provide preferential flow channels, whereas vertical cores are restricted by discontinuous cross-bedding connectivity. Triaxial fracturing significantly enhances low-confinement permeability by generating or activating conductive fracture pathways, but these pathways exhibit strong mechanical compliance and rapidly lose conductivity under increasing confinement. Imbibition produces dual effects by either blocking effective flow channels or reactivating previously isolated microfracture pathways, depending on the initial pore–fracture architecture. These findings reveal that shale permeability evolution is controlled by the competition among bedding-guided connectivity, fracture creation, fluid-induced alteration, and stress-driven aperture closure, providing new insight into the coupled structural–hydraulic–mechanical behavior of anisotropic shale systems.