CHEMO-MECHANICAL EFFECTS IN ROCK FRACTURE GROWTH

Although fundamental processes of chemically assisted rock fracture are well established, fracture growth under subsurface and near-surface conditions is still viewed as a primarily physical process in an elastic medium. Field and core observations, high-resolution compositional SEM imaging, and laboratory tests specifically designed to evaluate chemo-mechanical effects increasingly demonstrate the significance of chemical water-mineral interactions in controlling key aspects of rock fractures such as fracture shape and aperture distribution. We find that: 1.) Under a wide range of subsurface conditions, natural fracture growth occurs at rates that are similar to mineral dissolution and growth rates suggesting that chemical reaction and transport kinetics control rates of natural fracture growth; 2.) Changes in fluid chemistry and chemical water-rock interaction can alter rock fracture mechanical properties even over short laboratory timescales and for fast fracture growth rates, either enhancing or impeding fracture propagation; 3.) Fluid-mineral and mineral-mineral reactions can drive fracture growth even in the absence of externally applied mechanical loading stresses. Chemo-mechanical fracture processes can affect fracture network geometry and fracture resistance through changes in pore-fluid chemical environment with implications for hillslope stability and rock failure with climatic changes; caprock integrity of subsurface reservoirs for stored CO2 and hydrogen, and induced fracture connectivity in enhanced geothermal systems and unconventional oil and gas operations.