Pore-Scale Modeling of Hydrogen-Brine Relative Permeability in Underground Hydrogen Storage

Abstract

Abstract Hydrogen is poised to become one of the most promising alternative clean sources of energy for climate change mitigation. The development of a sustainable hydrogen economy depends on the global implementation of safe and economically feasible intersessional hydrogen storage and recovery. However, the current body of literature lacks comprehensive numerical characterization of the multiphase flow of hydrogen-brine and how geological parameters at the pore scale influence the multiphase flow. This study presents a pore network simulation of hydrogen-brine and cushion gas-brine relative permeabilities. Initially, the generated pore network model was validated against the characteristics of the core sample, such as porosity, permeability, and pore size distribution. In addition, the model was adapted to replicate the results of the drainage capillary pressure curves and relative permeability curves observed in the laboratory experiment. Furthermore, a sensitivity analysis was conducted to quantify the effects of fluid and rock properties on the relative permeabilities of the fluids. The results indicate that the capillary pressure and the relative permeability of the hydrogen and brine are sensitive to the distribution of the surface contact angle. The relative permeability of hydrogen phase decreases as the frequency of pores with stronger water-wet contact angle values increases. The relative permeability endpoint (residual saturation) was also significantly influenced by pore and throat shape, pore and throat size distribution, and pore connectivity. Simulations of different cushion gases revealed that the relative permeabilities of CH4 and N2 are similar to hydrogen. This research offers a comprehensive pore-scale prediction of the relative permeability of hydrogen and brine systems and presents the parameters and cushion gases to consider in the selection of geological storage sites for hydrogen storage.