Effect of relative permeability hysteresis on reservoir simulation of underground hydrogen storage in an offshore aquifer

Underground hydrogen storage (UHS) in porous media is proposed to balance seasonal fluctuations between demand and supply in an emerging hydrogen economy. Despite increasing focus on the topic worldwide, the understanding of hydrogen flow in porous media is still not adequate. In particular, relative permeability hys-teresis and its impact on the storage performance require detailed investigations due to the cyclic nature of H2 injection and withdrawal. We focus our analysis on reservoir simulation of an offshore aquifer setting, where we use history matched relative permeability to study the effect of hysteresis and gas type on the storage efficiency. We find that omission of relative permeability hysteresis overestimates the annual working gas capacity by 34 % and the recovered hydrogen volume by 85 %. The UHS performance is similar to natural gas storage when using hysteretic hydrogen relative permeability. Nitrogen relative permeability can be used to model the UHS when hysteresis is ignored, but at the cost of the accuracy of the bottom-hole pressure predictions. Our results advance the understanding of the UHS reservoir modeling approaches.

Automated summary

Underground hydrogen storage in porous media is proposed as a solution to balance seasonal fluctuations in supply and demand. However, there is still insufficient understanding of how hydrogen flows in porous media, specifically regarding relative permeability hysteresis and its impact on storage performance. This study focuses on reservoir simulation and shows that neglecting relative permeability hysteresis leads to overestimation of working gas capacity and recovered hydrogen volume. The study also highlights the importance of accurate modeling of hysteresis for predicting bottom-hole pressures in underground hydrogen storage.