Hydrogen Storage in Saline Aquifers: Experimental Observations of Viscous-Dominated Flow

Abstract

Abstract Hydrogen (H2) storage in the subsurface is a potential long-term energy storage solution for renewable energy; however, hydrogen flow in the subsurface is not well understood and studied in the context of conventional reservoir engineering. A quantitative understanding of the similarities and dissimilarities between the transport behavior of H2, CO2, and CH4 is necessary to assess the feasibility of underground hydrogen storage (UHS) as well as guide the design and optimization of the storage site. A multi-phase flow experimental setup is introduced to examine the behavior of H2 transport in a brine-saturated core under different flow rates and flow regimes. Analog fluids of nitrogen (N2) and viscosified brine were used in lieu of H2 to obtain capillary number (NCa) and viscosity ratios similar to H2/brine flow at reservoir conditions. X-ray computed tomography (CT) was used to image the flow during gas injection and compute average gas saturation across the core sample. The small NCa experiment showed behavior consistent with capillary fingering and stable displacement based on the piston-like gas saturation curve. The high NCa experiment showed a mixture of viscous fingering and capillary fingering tendencies, necessitating the need for a liquid-liquid pairing study that allows for distinct viscous fingering behavior.