Numerical Investigation of Hydrogen Storage Loss in Saline Aquifers

Abstract Underground hydrogen storage (UHS), a large-scale and long-term energy storage system, can augment decarbonization prospects and drive the renewable energy sector forward due to the attractive energy capacity and environmentally friendly features of hydrogen (H2). One of the primary concerns of UHS is the in-situ loss of the injected H2 via different rock-fluid interactions. This study uses numerical simulation models to investigate the loss of H2 associated with the effects of different rock-fluid interactions and mass transfer mechanisms. Sensitivity studies were conducted to understand the impact of various factors, including the relative permeability hysteresis, capillary pressure, dissolution, and diffusion of H2 in brine. Furthermore, we also evaluated the effect of uncertainty in capillary pressure curves on trapped H2 using the parameters generated from an extensive literature survey. Finally, we compared the reservoir behavior in a finite and infinite-acting reservoir. The results showed that almost 20% of the injected H2 gets trapped in the reservoir due to the impact of the relative permeability at variable brine saturations. Furthermore, the results demonstrated that the relative permeability hysteresis during the imbibition phase significantly reduces the recoverable H2 due to residual trapping. Additionally, capillary pressure and dissolution moderately impacted the amount of trapped H2 during UHS. However, diffusion showed negligible impact on the final amount of H2 produced from the reservoir. The H2 loss in an infinite reservoir was significantly higher compared to the finite reservoir. To summarize, by analyzing the different H2-Rock-Fluid interactions, this study provides novel insights into the flow behavior of H2 in subsurface porous media.