Development of a Geological Hydrogen Storage Simulator For Cyclic Injection and Withdrawal Processes: Coupled Flow and Geomechanics With Capillary Hysteresis

Abstract We have developed a high-fidelity, coupled flow and geomechanics simulator specifically designed for geological hydrogen storage. This simulator integrates non-isothermal multiphase multicomponent flow of hydrogen and water with geomechanics, accounting for elastoplastic behavior such as Mohr-Coulomb failure, essential for maintaining the geomechanical integrity of storage reservoirs. Additionally, the simulator addresses capillary hysteresis resulting from repeated drainage and imbibition cycles induced by periodic hydrogen injection and production. To model capillary hysteresis robustly, we employ a thermodynamically consistent return mapping algorithm utilizing the van Genuchten model for the capillary pressure curve. The coupling between flow and geomechanics is achieved through the fixed-stress sequential method. We validated our simulator using three test cases (1D, 2D, and 3D) to assess its numerical stability and capabilities. In the 1D case, we evaluated numerical stability during repeated hydrogen injection and production, where both capillary hysteresis and geomechanical failure occur simultaneously. The results demonstrated stability, accurately capturing Mohr-Coulomb failure and capillary hysteresis curves. For the 2D and 3D cases, which focused on wellbore integrity and field-scale simulation, respectively, the simulator consistently provided reasonable and stable results for capillary hysteresis and effective stress, confirming its applicability to real field scenarios.