Work

Time-resolved 2D and 3D imaging of hydrogen and brine displacement processes in porous Clashach sandstone

Year: 2025

Type: article

Abstract: Hydrogen (H₂) storage in porous geological formations offers a promising means to balance supply and demand in the renewable energy sector, supporting the energy transition. Important unknowns to this technology include the H2 fluid flow dynamics through the porous medium which affect H2 injectivity and recovery. We used time-resolved X-ray micro-computed tomography to image real-time unsteady and steady-state injections of H2 and brine (2 M KI) into a Clashach sandstone core at 5 MPa and ambient temperature.In steady-state injections, H₂ entered the brine-saturated rock within seconds, dispersing over several discrete pores. Over time, some H2 ganglia connected, disconnected and then reconnected from each other (intermittent flow), indicating that the current anticipation of a constant connected flow pathway during multiphase fluid flow may be an oversimplification. Pressure oscillations at the sample outlet were characterized as red noise, confirming observations of intermittent pore filling. At higher H2 fractional flow the H2 saturation in the pore space increased from 20-22% to 28%. Average Euler characteristics were generally positive over time at all H2 flow fractions, indicating poorly connected H2 clusters and little control of connectivity on the H2 saturation. In unsteady-state injections, H₂ displaced brine in sudden pore-filling events termed Haines jumps, which are key to understanding fluid dynamics in porous media. Our results imply a lower H2 storage capacity in aquifers with higher hydrodynamic flow and suggest a low H2 recovery. For more accurate predictions of H2 storage potential and recovery, geological models should incorporate energy-dissipating processes such as Haines jumps.

Source: Journal of Colloid and Interface Science

DOI: 10.1016/j.jcis.2025.137704