A review of hydrogen/rock/brine interaction: Implications for Hydrogen Geo-storage

Hydrogen (H2) is currently considered a clean fuel to decrease anthropogenic greenhouse gas emissions and will play a vital role in climate change mitigation. Nevertheless, one of the primary challenges of achieving a complete H2 economy is the large-scale storage of H2, which is unsafe on the surface because H2 is highly compressible, volatile, and flammable. Hydrogen storage in geological formations could be a potential solution to this problem because of the abundance of such formations and their high storage capacities. Wettability plays a critical role in the displacement of formation water and determines the containment safety, storage capacity, and amount of trapped H2 (or recovery factor). However, no comprehensive review article has been published explaining H2 wettability in geological conditions. Therefore, this review focuses on the influence of various parameters, such as salinity, temperature, pressure, surface roughness, and formation type, on wettability and, consequently, H2 storage. Significant gaps exist in the literature on understanding the effect of organic material on H2 storage capacity. Thus, this review summarizes recent advances in rock/H2/brine systems containing organic material in various geological reservoirs. The paper also presents influential parameters affecting H2 storage capacity and containment safety, including liquid-gas interfacial tension, rock-fluid interfacial tension, and adsorption. The paper aims to provide the scientific community with an expert opinion to understand the challenges of H2 storage and identify storage solutions. In addition, the essential differences between under-ground H2 storage (UHS), natural gas storage, and carbon dioxide geological storage are discussed, and the direction of future research is presented. Therefore, this review promotes thorough knowledge of UHS, provides guidance on operating large-scale UHS projects, encourages climate engineers to focus more on UHS research, and provides an overview of advanced technology. This review also inspires researchers in the field of climate change to give more credit to UHS studies.