Exploring Coupled Processes in Underground Hydrogen Storage: Insights from Reactive Flow Experiments

Underground hydrogen storage (UHS) in porous reservoirs is a promising solution for large-scale renewable energy storage. However, significant uncertainties remain regarding the impact of cyclic hydrogen injection and withdrawal cycles on reservoir geochemistry and hydraulic properties, particularly in depleted gas reservoirs, containing residual methane or CO2. Recent studies have highlighted the complex interplay of coupled thermo-hydro-mechanical-chemical and microbiological (THMCB) processes that could influence key reservoir properties such as porosity, permeability, and mechanical integrity during UHS operations.

This talk will explore some of these uncertainties by reviewing the coupled THMCB processes at play and presenting findings from recent reactive flow experiments conducted under reservoir-relevant conditions. The experiments aim to elucidate changes in reservoir properties and fluid chemistry, focusing on the impact of hydrogen-brine-rock reactions and the role of hydrogen trapping. Additionally, the presentation will discuss the significance of changes in redox potential (Eh) observed in hydrogen-saturated brine as a potential indicator of hydrogen-induced geochemical reactions.