Chemo-Mechanical Coupling in Fractured Shale With Water and Hydrocarbon Flow

Abstract

The transport of chemically reactive fluids through fractured clay-rich rocks is fundamental to many subsurface engineering technologies. Here, we present results of direct-shear laboratory experiments with simultaneous imaging by X-ray Computed Tomography in Opalinus claystone with subsequent fluid injection to unravel the interplay between mechanical fracture deformation, fluid sorption, and flow. Under constant radial stress (σc = 1.5 MPa), the average mechanical aperture (Formula presented.) increases with shear displacement. Upon brine injection, (Formula presented.) is reduced by 40% relative to initial conditions ((Formula presented.) μm) and fluid-sorption induces a divergent displacement of the two sample halves (Δh = ±50 − 170 μm) quantified by digital image correlation. None of these changes are observed in a control experiment with decane, indicating that creep is subordinate to swelling in sealing the fracture. Swelling-induced changes in permeability within the fracture are heterogeneous and largely affect the fracture flow field, as computed using numerical simulations.