Comparative analysis of carbon dioxide and hydrogen plume migration in aquifers inspired by the FluidFlower benchmark study

Abstract

Large-scale geological storages of hydrogen (H${}_2$) and carbon dioxide (CO${}_2$) in saline aquifers present feasible options for a sustainable energy future. We compared the plume migration of CO${}_2$ and H${}_2$ in aquifers using the FluidFlower benchmark, incorporating the state-of-the-art thermophysical and petrophysical properties. The H${}_2$ plume, with its higher buoyancy and mobility compared to CO${}_2$, remains predominantly in the gas phase due to its lower solubility, increasing the chances of escaping through fractures or migration to distant regions. This additionally leads to a higher pressurized reservoir, which, along with higher buoyancy, increases the chance of caprock penetration. Dissolution trapping of CO${}_2$ into brine increases over time due to its fingering, while H${}_2$ does not show fingering. Our findings show that while geological carbon storage (GCS) benefits significantly from all structural, dissolution, and residual trapping, underground hydrogen storage (UHS) relies mainly on structural trapping, making the integrity of sealing elements of the system a key factor in its performance.