Microbial impact on basalt-water-hydrogen system: Insights into wettability, capillary pressure, and interfacial tension for subsurface hydrogen storage

Hydrogen (H₂) fuel is assessed to be a major component of sustainable energy systems in the net-zero world. However, hydrogen storage is challenging and requires safe and environmentally friendly solutions like H₂ geo-sequestration. This study evaluates the effects of sulphate-reducing bacteria (SRB) on H₂ geological storage potential in the basalt rock. Fourier-transform infrared spectroscopy (FTIR) findings show the presence of significant components, that is, O-Si-O and organic functional groups, that is, aromatics, amine salts, alkane, and cyclohexane in the basalt rock immersed in the nutrient solution without SRB. However, we found that C-H stretching modes of organics with peaks at 1,465 cm⁻¹ were observed. Consequently, amine salt (N-H) (850–750 cm⁻¹), solvent impurities (C-H), and alkane spectrums are components of nutrient solutions and can be results of metabolic microbial activity that can influence on the surface of the basalt rock. Hence, these changes indicate the presence of microbial activity which might affect the surface chemistry of the rock leading to wettability alteration. We observed that the contact angle (θ) of brine-H₂ on the rock surface slightly changed from 500 to 4,000 psi pressure after the effect of bacteria at 50 °C. The wettability changed the surface of the rock from strong water-wet to weak or intermediate water-wet condition (i.e., θ < 75°) at 4,000 psi and temperatures 25 and 50 °C after the bacteria effect. The affiliation of brine water reduces on the rock surface with increasing temperatures and pressures, even without microbial influence. Additionally, we investigated interfacial tension and capillary pressure on SRB bacteria treated basalt which is not yet reported in the published work. Interfacial tension (IFT) and P_c of H₂ were reduced by 19% and 65%, respectively at 50 °C and 4,000 psi after the bacteria effect. Hence, the above findings could help to answer the key factors of the reservoir rock including wettability, capillary pressure, and interfacial tension to plan a field-scale H₂ geo-sequestration strategy under the influence of biotic life. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.