H2−brine interfacial tension as a function of salinity, temperature, and pressure; implications for hydrogen geo-storage

Hydrogen as a clean fuel source compared to hydrocarbons has attracted many attentions to mitigate anthropogenic greenhouse gas emissions and meet global energy demand. However, high volatility and compressibility of hydrogen make a challenge for its storage. In this regard, the surface-based hydrogen storage facilities (e.g. aerospace, cryogenic tanks, high-pressure gas cylinders, etc.) have been in operation for decades. Moreover, H2 geo-storage is an effective way to store vast volume of hydrogen in deep underground formations where it can be withdrawn again to generate energy when the need arises. The interaction between the injected hydrogen and resident formation fluids (e.g. water), can strongly influence the H2-flow pattern and storage capacity. In this regard, interfacial tension (γ) between hydrogen and brine is a key parameter that influences hydrogen displacement within the geological porous medium. As there is a serious lack of literature on this important subject, we measured H2-brine interfacial tension at various geo-storage conditions for a wide range of pressure, temperature, and brine salinity, using the pendant drop technique. The results of the study indicate that γ declined linearly with increasing pressure when temperature and salinity are kept constant. Moreover, a linear reduction in γ with increasing temperature was observed under constant salinity and pressure conditions. The results also clearly demonstrate that γ increased linearly with brine molality over the whole range investigated. An empirical equation was also developed with which γ as a function of pressure, temperature, and brine molality can be predicted. The predictions for data points of this work had a maximum deviation of 2.13% from the experimental data. This work thus provides fundamental data for H2 geo-storage projects, and aids in the implementation of an industrial-scale hydrogen economy.