Numerical Comparison of Hydrogen and CO2 Storage in Deep Saline Aquifers from Pore Scale to Field Scale

Underground hydrogen storage (UHS) and carbon dioxide capture and storage (CCS) have been the frontiers of energy transition of petroleum and coal industries. The similarities and differences of UHS and CCS are the key focus of this work. We first investigate the H-2/CO2-brine flow characteristics in Berea sandstones applying our proposed pore-scale network modeling methods, emphasizing on the hysteresis of nonwetting phase. Then, the cap rock sealing capillary pressure curves are generated by scaling with the shale-gas-brine wettability conditions. Finally, the field-scale numerical models of H-2 and CO2 injection processes are implemented based on the pore-scaled results, where the storage capacity and sealing security are focused. The simulation results imply that CO2 storage process has more potential of leakage happening, while the H-2 storage is much safer since the cap rock sealing capillary pressure remains higher. Moreover, due to the extremely low viscosity and buoyancy effect, the gas front of H-2 is sharper than that of CO2. The maximum injection volume of H-2 is much lower than that of CO2 because H-2 is less compressible at the subsurface conditions. In terms of storage capacity of finite saline aquifer, CO2 exhibits superiority over H-2 storage. This study attempts to undertake the essential comparison of UHS and CCS in the way of multiscale numerical simulation methods and to propose the general rules of thumb for the related researchers.