Insights into the Role of Microbial Dynamics and Distribution Heterogeneity on the Performance of Underground Hydrogen Storage Using Reservoir-Scale Biogeochemical Modelling

This research explores the role of microbial activity and its spatial distribution in influencing the performance of underground hydrogen storage (UHS) systems. By employing reservoir-scale reactive transport simulations using the CMG-GEM platform and incorporating biochemical kinetics derived from laboratory studies, the study investigates how the presence and localization of microbial populations can affect hydrogen retention and the formation of biogenic by-products such as methane, hydrogen sulfide, and acetate. The simulations consider different scenarios of microbial distribution, from homogeneous to spatially heterogeneous distributions, to understand both general and localized effects on system performance. Microbial processes are found to be most active during the initial operational stages, where substrates such as electron acceptors and carbon sources are still available. Over time, these microbial effects decrease as essential nutrients are consumed and not replenished, leading to a natural decline in biological reactivity. Despite localized impacts near microbial hotspots, the long-term hydrogen storage efficiency is only moderately influenced by microbial distribution. The spatial positioning of microbial biomass affects the timing and persistence of microbial by-products in the production stream but does not dramatically compromise cumulative hydrogen recovery under realistic subsurface conditions. Overall, this study highlights the importance of integrating microbial dynamics and spatial heterogeneity into UHS modeling approaches. It demonstrates that while microbial activity can shape short-term system behaviour, its impact at the reservoir scale is mitigated by nutrient limitations and geological complexity. These insights are critical for supporting safe and effective design and monitoring strategies in future hydrogen storage operations.