Residual trapping is an important trapping mechanism that affects the efficiency of cyclic storage and withdrawal of hydrogen in geological media. In this study, we made the first attempt to conduct pore-scale modeling to investigate the effects of pore geometry and injection rate on the occurrence and percentage of residual trapping via two major mechanisms: bypassing and snap-off. We started our theoretical and numerical analyses from a single rectangular pore to understand the key controls in bypassing. We further investigated two factors on bypassing: (a) a continuous cycle of injection-extraction of H₂, and (b) varied pore geometry. To understand snap-off as the other mechanism, we used a three-end single asymmetric pore. Based on our pore-scale simulations, we found that: (a) A higher pore height/width ratio (h/w) and a higher injection rate cause more residual trapping, which is unfavorable for withdrawing H₂ if starting from 100% H₂; (b) the trapping percentage increases with the h/w first in the imbibition-dominated regime and then decrease after h/w reaches 0.5 in the drainage-dominated regime; (c) A converging-shaped pore can result in less trapping volumes. Both our theoretical and numerical results show that snap-off occurs when the other forces outbalance the capillary force. Through a theoretical comparison between H₂ and CO₂ and a discussion of these trapping mechanisms for engineering applications, we concluded that the mechanisms that we found from this study are applicable for CO₂ residual trapping and can be useful for developing engineering controls of H₂ storage.

The dataset contains the input files for CFD simulation of H₂-water flow in dead-end pore geometry.

OpenFOAM, an open-source PDE solver.