CO2/CaCl2 solution interfacial tensions under CO2 geological storage conditions: Influence of cation valence on interfacial tension

The effectiveness of CO2 storage in deep saline aquifers and hydrocarbon reservoirs is governed, among other factors, by the interfacial tension between the injected CO2 and formation water (brine). Experimental data on CO2/water and CO2/NaCl solution have revealed that the interfacial tension depends on the pressure, temperature and water salinity. However, there is still a lack of data for other salts (such as MgCl2 and CaCl2) which are also present in aquifers and carbonate reservoirs. In the present work, the interfacial tension (IFT) of the system CO2/CaCl2 solution is measured under pressures, temperatures and salinities which are relevant to storage conditions. The evolution of CO2/CaCl2 solution IFT with pressure and temperature is similar to that reported for CO2/water and CO2/NaCl solution systems and increases linearly with salinity. When correlating the measured IFT with the salt concentration, it looks that the IFT increase, due to salt concentration, is proportional to the cation valence.