Chemo-Mechanical Coupling In Fractured Shale With Water And Hydrocarbon Flow

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 (sigma(c) = 1.5 MPa), the average mechanical aperture d over bar CT increases with shear displacement. Upon brine injection, d over bar CT is reduced by 40% relative to initial conditions (d over bar CT0=140-250 mu m) and fluid-sorption induces a divergent displacement of the two sample halves (Delta h = +/- 50 - 170 mu m) 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.