Speaker
Description
Capillary trapping and hydrogen recovery efficiency in underground hydrogen storage (UHS) systems are governed not only by fluid properties and wettability but also by the detailed geometry of pore spaces. We hypothesise that the onset of capillary entry pressure is controlled by a critical pore diameter—referred to as the effective pore throat—below which interfacial forces increase sharply and dominate gas–liquid displacement.To test this hypothesis, a series of single tapered-capillary experiments were performed to simulate two-phase gas–brine displacement under controlled conditions. The experimental variables included capillary diameter, gas type (H₂, CO₂, N₂, CH₄, air, He), brine composition (deionised water, NaCl, CaCl₂), and CO₂ equilibration of the aqueous phase. Pressure evolution and dynamic contact angles were measured to decouple the effects of pore geometry, fluid composition, and interfacial properties. The results demonstrate that capillary entry pressure becomes significant only when the pore diameter falls below a critical threshold, confirming the relevance of the effective pore throat concept. Gas type exerted minimal influence on capillary behaviour due to comparable gas–water interfacial tensions. In contrast, brine chemistry—particularly the presence of divalent cations—and CO₂ equilibration substantially reduced capillary pressures, thereby enhancing hydrogen mobility. These findings provide a mechanistic framework for improving pore-scale modelling, optimising injection strategies, and tailoring brine conditions to enhance hydrogen recovery in UHS applications.
| Country | United Kingdom |
|---|---|
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