New Flow Simulation Framework for Underground Hydrogen Storage Modelling Considering Microbial and Geochemical Reactions

The widespread use of hydrogen as an energy source relies on efficient large-scale storage techniques. Underground Hydrogen Storage (UHS) is a promising solution to balance the gap between renewable energy production and constant energy demand. UHS employs geological structures like salt caverns, depleted reservoirs, or aquifers for hydrogen storage, enabling long-term and scalable storage capacity. Therefore, robust and reliable predictive tools are essential to assess the risks associated with geological hydrogen storage. This paper presents a novel reactive transport model called “Underground Gas Flow simulAtions with Coupled bio-geochemical reacTions” or “UGFACT”, designed for various gas injection processes, accounting for geochemical and microbial reactions. The flow module and geochemical reactions in the UGFACT model were verified against two commercial reservoir simulators, E300 and CMG-GEM, showing excellent agreement in fluid flow variables and geochemical behaviour. A major step forward of this model is to integrate flow dynamics, geochemical reactions and microbial activity. UGFACT was used to conduct a simple storage cycle in a 1D geometry across three different reservoirs, each with different mineralogies and water compositions: Bentheimer sandstone, Berea sandstone, and Grey Berea sandstone, under three microbial conditions (“No Reaction”, “Moderate Rate”, “High Rate”). The findings suggest that Bentheimer sandstone and Berea sandstone sites may experience severe effects from ongoing microbial and geochemical reactions, whereas Grey Berea sandstone shows no significant H2 loss. Additionally, the model predicts that under the high-rate microbial conditions, the hydrogen consumption rate can reach to as much as 11 mmol of H2 per kilogram of water per day (mmol / kg⋅day) driven by methanogenesis and acetogenesis.