A Critical Review of Underground Hydrogen Storage in Porous Media: Focus on Fluid–Fluid and Rock–Fluid Interactions
Yue Shi, Yujia Guo, Ningwei Tai, Kishore K. Mohanty
Abstract
Underground hydrogen storage (UHS) is a key technology for achieving net-zero emissions. While salt caverns are commonly used, their limited geographic distribution and capacity constrain large-scale H 2 storage. In contrast, saline aquifers and depleted gas reservoirs offer broader applicability, higher volumetric capacity, and economic advantages. However, these porous media involve more complex fluid–fluid and rock–fluid interactions, especially under deep formation conditions (higher pressure and temperature, native gas presence, organic matter, and potential biotic/abiotic reactions). Given the recent surge in experimental studies on UHS, a timely review and critical evaluation of the data reliability is essential to guide future research. Based on the review, H 2 ’s density, viscosity, solubility, interfacial tension for H 2 –brine system, and the bulk phase diffusion coefficient have been extensively studied under various conditions. Yet, mechanisms of H 2 viscous fingering and diffusion into fluid-saturated porous media remain understudied. H 2 is generally nonwetting toward rock surfaces unless a high content of organic components is present on the mineral. The weak H 2 -wetness observed at high pressures in some studies may, at least in part, result from limitations in contact angle measurement techniques rather than actual wettability alteration. Hysteresis effects in hydrogen storage have been primarily investigated under shallow saline aquifer conditions, with a fitted linear trapping coefficient of 0.55, while its phenomenon in depleted gas reservoirs remains insufficiently explored. The abnormally low H 2 relative permeability reported may result from the failure to account for possible nonuniform saturation along the core. Under typical UHS conditions, abiotic reactions are not expected to play a significant role, whereas biotic reactions can be complex and severe if microbes are present and carbon sources are available.