Impact of formation conditions and well configurations on underground hydrogen storage

Converting surplus renewable energy into hydrogen is considered an efficient technique to balance renewable energy generation and demand, which necessitates large-scale underground hydrogen storage (UHS) in geological formations. While the H-2 trapping mechanisms and fluid flow behavior have been rigorously reported in past studies, the performance of UHS is strongly influenced by the formation conditions and well configurations, which have not been explored thoroughly. To this end, this study investigated the sensitivity of UHS efficiency to variations in formation temperature, brine salinity, well placement, and well perforations. For each scenario, key aspects such as plume migration dynamics, residual trapping, dissolution trapping, structural trapping, H-2 recovery factor, and water production were thoroughly analyzed. The results indicate that factors such as formation temperature, brine salinity, and well perforations have a negligible impact on the shape of the overall H-2 plume. However, these significantly influence local H-2 saturations. Formations with higher temperatures, central dome well placement, and production wells in the top layers exhibit a higher H-2 recovery factor (as high as 69.93 %), whereas salinity plays a minor role in H-2 trapping and withdrawal (maximum change observed is similar to 1.7 % and similar to 1.4 % for trapping and withdrawal respectively with a 20 wt % increase in salinity). In addition, brine production is strongly influenced by the formation conditions and well configurations (e.g., similar to 3965 m(3) brine produced under at 343 K and similar to 26,000 m(3) for non-central well placement), due to variations in H-2/brine properties, such as density and viscosity, and the extent of H-2 accumulation.