Impact of Reservoir Heterogeneity on Microbial and Geochemical Reactions During Underground Hydrogen Storage

The study examines the effects of reservoir heterogeneity on microbial and geochemical reactions during underground hydrogen storage (UHS). As renewable energy technologies advance, efficient energy storage solutions are essential. Depleted gas reservoirs offer a promising option for hydrogen storage, but microbial and geochemical reactions induced by hydrogen injection can produce CH₄ and H₂S, affecting reservoir integrity and hydrogen quality. Using reactive transport modeling, the research analyses how reservoir heterogeneity, such as variations in porosity and permeability, influences hydrogen distribution and microbial activities. A coupled modeling approach combines a batch model in PHREEQC, focusing on microbial reactions, and fluid flow simulations using MRST. These models consider hydrogen, water, and other components' interactions in both homogeneous and heterogeneous systems under varying microbial reaction rates. Results indicate that reservoir heterogeneity enhances mixing between hydrogen and in situ gases, increases microbial activity, and reduces hydrogen recovery. In heterogeneous reservoirs, recovery rates were consistently lower, and microbial consumption of hydrogen higher, compared to homogeneous systems. The findings emphasize the importance of considering reservoir heterogeneity in UHS design and optimization to mitigate risks and improve efficiency. Enhanced interaction surfaces in heterogeneous systems amplify microbial hydrogen loss, underscoring their impact on storage performance.