Hydrogen wettability in carbonate reservoirs: Implication for underground hydrogen storage from geochemical perspective

Hydrogen has been considered as a promising renewable source to replace fossil fuels to meet energy demand and achieve net-zero carbon emission target. Underground hydrogen storage attracts more interest as it shows potential to store hydrogen at large-scale safely and economically. Meanwhile, wettability is one of the most important formation parameters which can affect hydrogen injection rate, reproduction efficiency and storage capacity. However, current knowledge is still very limited on how fluid-rock interactions affect formation wettability at in-situ conditions. In this study, we thus performed geochemical modelling to interpret our previous brine contact angle measurements of H-2 -brine-calcite system. The calcite surface potential at various temperatures, pressures and salinities was calculated to predict disjoining pressure. Moreover, the surface species concentrations of calcite and organic stearic acid were estimated to characterize calcite-organic acid electrostatic attractions and thus hydrogen wettability. The results of the study showed that increasing temperature increases the disjoining pressure on calcite surface, which intensifies the repulsion force of H-2 against calcite and increases the hydrophilicity. Increasing salinity decreases the disjoining pressure, leading to more H-2-wet and contact angle increment. Besides, increasing stearic acid concentration remarkably strengthens the adhesion force between calcite and organic acid, which leads to more hydrophobic and H-2-wet. In general, the results from geochemical modelling are consistent with experimental observations that decreasing temperature and increasing salinity and organic acid concentration increase water contact angle. This work also demonstrates the importance of involving geochemical modelling on H-2 wettability assessment during un-derground hydrogen storage. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Hydrogen is regarded as a promising renewable energy source to replace fossil fuels and achieve net-zero carbon emissions. Underground hydrogen storage is attracting more attention due to its potential for safe and economical large-scale hydrogen storage. This study used geochemical modeling to interpret the fluid-rock interactions and formation wettability in the H-2 -brine-calcite system. The results showed that temperature, salinity, and organic acid concentration have significant effects on the wettability of hydrogen, providing insights for assessing hydrogen wettability during underground hydrogen storage.