A REVIEW OF THE CURRENT STATE OF SUBSURFACE HYDROGEN STORAGE IN THE UNITED STATES

The interest in hydrogen as an energy source has grown rapidly over the past few years along with the development of renewable energy technologies. Power-to-gas technology is an alternative to store surplus energy, where electricity is converted into hydrogen gas via electrolysis and stored in underground geologic formations, remaining trapped until needed as an energy source. Commercial hydrogen storage began in the United States in the 1980s, when it was injected into solution-mined caverns in salt formations. Since then, the use of these formations for geologic hydrogen storage has proven efficient: the high impermeability of anhydrite prevents diffusion of hydrogen out of the formation while also decreasing the risk of contamination of the gas. Three salt cavern facilities are currently operational as underground hydrogen storage facilities in the Gulf Coast Basin in Texas. However, the geographical distribution of salt formations is the main limitation of this domestic geologic energy storage option, as suitable salt formations are typically located in the Gulf Coast basin. Thus, non-potable aquifers, and depleted oil and gas reservoirs in siliciclastic formations should be studied as alternatives for storing hydrogen in the subsurface in areas lacking salt deposits. Siliciclastic formations have therefore been targeted due to their widespread storage potential; however, studies have shown that chemical reactions between hydrogen and the host-rock can lead to petrophysical changes that impact reservoir properties, such as porosity and permeability. Furthermore, microbial communities in the siliciclastic formation water can trigger hydrogen loss via methanogenesis, acetogenesis, and sulfate reduction processes. The purpose of this work is to provide an update on current underground hydrogen storage research in the United States, to showcase current data gaps and challenges implementing hydrogen storage, and to highlight the critical parameters that need to be investigated when assessing the resource potential of siliciclastic formations to serve as hydrogen storage media.