Geochemical reactions-induced hydrogen loss during underground hydrogen storage in sandstone reservoirs

Abstract

Underground hydrogen storage (UHS) appears to be an important means as a large-scale and long-term energy storage solution. A primary concern of UHS is the in-situ geochemical reactions-induced hydrogen loss. In this context, we performed geochemical modelling to examine the hydrogen loss associated with hydrogen dissolution and fluid-rock interactions using PHREEQC (Version 3) as a function of temperature and pressure. We also performed geochemical modelling with kinetics to investigate the potential hydrogen loss in two commercial gas storage reservoirs (Tubridgi and Mondarra) in Western Australia against the reservoir mineralogy, fluid properties, depth and temperature.Our results show that increasing pressure and temperature only slightly increases hydrogen solubility in brines without minerals. Increasing salinity slightly decreases the solubility of hydrogen in brines. The saturated hydrogen aqueous solution almost does not react with silicate and clay minerals, which is favorable for underground hydrogen storage in quartz-rich sandstone reservoirs. However, unlike silicate and clay minerals, carbonates like calcite triggers up to 9.5% hydrogen loss due to calcite dissolution induced hydrogen dissociation process. Kinetic simulations show that Tubridgi only leads to 0.72% of hydrogen loss, and Mondarra causes 2.76% of hydrogen loss as a result of reservoir calcite dissolution and hydrogen dissociation in brines in 30-year time. Nearly over 87% of calcite cement from Mondarra may be dissolved in 30-year, suggesting potential risks associated with wellbore stability. In conclusion, geochemical reactions-induced hydrogen loss would be minor for UHS in porous media, and we argue that deep calcite-free reservoirs together with calcite-free caprocks would be preferable for underground hydrogen storage.