Underground hydrogen storage in sandstone reservoirs: Effects of geochemical reactivity of hydrogen on reservoir performance

Underground hydrogen storage in porous rocks is a promising method to stabilize renewable energy fluctuations. However, data on the geochemical reactivity of hydrogen with reservoir rocks and its potential effects on reservoir performance are limited. This study investigates the geochemical reactivity of hydrogen with Buntsandstein reservoir sandstones from northern Germany, collected at a depth of about 2.5 km. Experiments were performed at 100 °C and 150 bar hydrogen partial pressure for four weeks, examining scenarios with dry hydrogen, synthetic saline fluid with hydrogen, synthetic saline fluid with helium (as a control), and an oxidation environment (air). We measured permeability, porosity, magnetic susceptibility, and fluid element concentration before and after the experiments. Results showed no significant mineral changes attributed to hydrogen. Magnetic susceptibility indicated no formation of magnetic minerals, such as magnetite and pyrrhotite. Minor variations in permeability and porosity were attributed to anhydrite dissolution from fluid chemistry nonequilibrium. Overall, our findings suggest hydrogen interactions with Buntsandstein sandstone (no pyrite content) at temperatures up to 100 °C do not risk hydrogen loss or reservoir performance degradation.