Abstract
Among all gas geo-storage sites, basaltic formations have attracted limited attentions in recent years, specially for large-scale storage of CO2. However, the suitability of the basaltic formations for large-scale H-2 storage is completely unknown. Wettability of these geological formations is an important parameter for gas geo-storage process as it determines the capacity of gas to spread throughout the pore matrix. To comprehend the wetting characteristics of natural and ideal basaltic rocks in geological conditions, we have measured the basalt-H-2-brine contact angles with and without presence of organics under various physio-thermal conditions (5-20 MPa and 308-343 K). Further, H-2 column heights which can be safely stored in basaltic formations were calculated based on the contact angle experimental data. Moreover, acquired hydrogen wettability data was compared with that of CO2 for validation purposes. The results showed that the basalt-H-2-brine system was strongly water-wet at lower pressures (5 and 10 MPa), but it turned to weakly water-wet at higher pressures (15 and 20 MPa). The increase in temperature and organic acid concentrations also showed negative effect so that basalt-H-2-brine system completely turned to intermediate-wet. The H-2 column height calculations have suggested that unlike CO2 which may show leakage above depth of 1100 m, H-2 could be safely trapped in basaltic formation even up to 2000 m. The presented data in this work is highly crucial, which will aid in the successful implementation of H-2 storage in basaltic formations.