International Journal of Hydrogen Energy
School of Engineering
Underground hydrogen (H2) storage (UHS) and carbon dioxide (CO2) geo-storage (CGS) are prominent methods of meeting global energy needs and enabling a low-carbon global economy. The pore-scale distribution, reservoir-scale storage capacity, and containment security of H2 and CO2 are significantly influenced by interfacial properties, including the equilibrium contact angle (θE) and solid-liquid and solid-gas interfacial tensions (γSL and γSG). However, due to the technical constraints of experimentally determining these parameters, they are often calculated based on advancing and receding contact angle values. There is a scarcity of θE, γSL, and γSG data, particularly related to the hydrogen structural sealing potential of caprock, which is unavailable in the literature. Young's equation and Neumann's equation of state were combined in this study to theoretically compute these three parameters (θE, γSL, and γSG) at reservoir conditions for the H2 and CO2 geo-storage potential. Pure mica, organic-aged mica, and alumina nano-aged mica substrates were investigated to explore the conditions for rock wetting phenomena and the sealing potential of caprock. The results reveal that θE increases while γSG decreases with increasing pressure, organic acid concentration, and alkyl chain length. However, γSG decreases with increasing temperatures for H2 gas, and vice versa for CO2. In addition, θE and γSL decrease, whereas γSG increases with increasing alumina nanofluid concentration from 0.05 to 0.25 wt%. Conversely, θE and γSL increase, whereas γSG decreases with increasing alumina nanofluid concentration from 0.25 to 0.75 wt%. The hydrogen wettability of mica (a proxy of caprock) was generally less than the CO2 wettability of mica at similar physio-thermal conditions. The interfacial data reported in this study are crucial for predicting caprock wettability alterations and the resulting structural sealing capacity for UHS and CGS.
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