Underground hydrogen storage in saline aquifers: Impacts of hysteresis, wettability heterogeneity, and geological configuration

Underground hydrogen storage in deep saline aquifers is a promising option for large-scale energy buffering, yet its performance is strongly controlled by pore-scale flow behavior and reservoir architecture. This study applies a pore-to-reservoir workflow that links QSGS-based digital rock models, pore-network flow simulations and CMG-GEM compositional modeling. Five rock types with distinct porosity-permeability-wettability characteristics are upscaled into two conceptual aquifers, an isotropic random model and an anisotropic layered model, and six hydrogen injection-withdrawal cycles are simulated. Relative permeability hysteresis is identified as a first-order control: neglecting hysteresis yields hydrogen recovery factors approaching 97%, whereas including hysteresis reduces final recovery to about 91% and 87% in the isotropic and layered cases because of residual gas trapping. Wettability heterogeneity increases recovery by 2–3% and deepens plume penetration only in the isotropic configuration, while its influence remains minor in the layered system, where vertical low-permeability barriers dominate flow. The layered model also requires higher bottom-hole pressures, indicating stricter operational constraints than in the isotropic random model.