Hydrogen-wettability alteration of Indiana limestone in the presence of organic acids and nanofluid

This study focuses on the wettability alteration (changing from a hydrophobic state to a hydrophilic state) of Indiana limestone for hydrogen (H2) geological storage. We examine the effect of hexanoic acid C6, lauric acid C12, and stearic acid C18, on the wettability of Indiana limestone at ambient (298 K and 0.1 MPa) and reservoir (323 K and 8.27 MPa) conditions. The effects of silica nanofluids (silica with deionized water) at various concentrations (0.1 wt%, 0.25 wt%, and 0.5 wt%) on the wettability reversal of stearic-aged samples were tested at ambient and reservoir conditions. The results revealed increased H2-wetness (hydrophobicity) of the rock exposed to these organic acids in reservoir conditions. However, this hydrophobicity significantly decreased with the nanofluid treatment of the stearic-aged samples. This wettability reversal may increase the H2 storage capacity and containment security and lead to successful large-scale geological storage operations if H2 residual trapping is minimized.