What Makes a Good Underground Hydrogen Storage Reservoir? Insights From Existing Gas Storage Fields, Classic Petroleum Systems, and Geologic Principles

The realization of hydrogen (H2) as a viable low-carbon energy carrier, especially as an additive or substitute in natural gas applications, will require a significant infrastructure transformation. This transition will occur over decades and will require the full spectrum of energy storage options from technologies currently under development to traditional methods like above ground tanks and underground gas storage (UGS). If hydrogen is to replace most fossil fuel-based energy systems, it is likely that significantly more UGS will be needed. The existing UGS infrastructure was built ad hoc over many decades to buffer industrial and residential energy demand. While underground hydrogen storage (UHS) will be needs-based, a more strategic deployment will reduce costs and accelerate the transition to a low-carbon future. Enabling this deployment will require a systematic understanding of the geologic requirements for UHS facilities.

To understand the general characteristics of viable underground gas storage facilities, we characterize existing UGS facilities and summarize their key properties. We analyze storage volume, working gas volume, storage/delivery rates, number of wells, operating pressure, and temperature. Geologic principles and rock properties (e.g., mineralogy, petrophysical properties) also provide insight into the viability of storage systems. Thus, we also identify the types of caprocks, reservoirs, and structural trappings at existing UGS facilities. Natural analogs such as accumulations of helium, carbon dioxide, and (the few examples of) H2 are also considered along with existing UGS facilities that store town gas (a blended gas containing H2). Finally, we consider the unique properties of H2 and how they may influence geologic requirements of a UHS facility. For example, the lower energy density of H2 may require higher flow rates to meet the same energy demand, the smaller molecule size of the gas may allow for easier leakage, and introduction of H2 ­could spur microbial and geochemical interactions that result in asset loss. This work cross-cuts these topics to constrain what key properties operators should look for when prospecting for new UHS sites.