Storage Area Assessment for Underground Hydrogen Storage (UHS) - Material Integrity Concerns

Abstract As hydrogen is becoming a key source for transitioning the existing energy system toward decarbonized sources, one of the remaining challenges for the large-scale deployment of hydrogen is the development of safe and efficient storage systems. Geological reservoirs, such as depleted oil and gas fields or saline aquifers, have been discussed as a large-scale storage option that could provide the volume capacity needed for large-scale underground hydrogen storage (UHS). While underground gas storage (UGS) has been safely used for CH4 storage for decades, the experience is not directly transferable in the UHS considering the differences between the two systems. Differences include: the cyclic loading and frequency restrictionsthe purity limitationsdifferent properties of hydrogen such as diffusivity, dissolution, and surface/interfacial tension, which can lead to different physiochemical behaviors in the reservoir.microbial activity, which will be more significant during UHS considering that molecular hydrogen is one of the main electron donors for microbial respiration in the subsurface. Therefore, a UHS assessment should include a subsurface microbial biosphere review of the native bacteria and archaea as well as those introduced during drilling, pumping and mining. The assessment should also consider the effect of other contaminants like pyrite (FeS2) and other sulfur containing compounds, water, CO2 and organic acids, which could potentially cause corrosion and adversely impact integrity. This paper discusses these issues and provides a pathway to a storage assessment for UHS from the material integrity perspective.