Microfluidic dynamic contact angles of hydrogen mixtures – Brine at conditions relevant to shallow UHS

Hydrogen storage in depleted gas reservoirs is a promising large-scale option for intermittent green energy, yet the influence of resident natural gas on storage performance remains poorly understood. We report dynamic contact angles for hydrogen, methane, and 50 mol % mixtures in a hydrophilic glass chip at 58.6 bar and 20–50 °C. During drainage, hydrogen exhibits strongly water-wet angles (12-25°), becoming more intermediate-wet with increasing methane content (22-48°). In-situ mixing resulted in 1/4 reduction in dynamic angles alongside up to 12 % reduced initial gas saturation. Increasing temperature to 50 °C augments dynamic angles. Similarly, higher methane content increases contact angles during imbibition with lower gas trapping, while elevated temperature yields mixture angles of ∼42–44° with 70 % less trapping. Our results indicate that increasing methane content leads to more weakly water-wet angles exhibiting a beneficial effect on storage from a wettability standpoint. • Dynamic contact angles for hydrogen, methane, and 50 % mixtures. • More intermediate-wet receding angles with higher methane content (H 2 : 18°, CH 4 : 35°). • 25 % reduction in receding angles as a result of in-situ mixing. • Increase of 10° in advancing angles with 50 mol % CH 4 percentage. • Higher advancing angles (∼5°) as temperature rises to 50 °C.