Interfacial tension between CO2 and brine (NaCl + CaCl2) at elevated pressures and temperatures: The additive effect of different salts

An extensive laboratory study was conducted to measure the interfacial tension (IFT) between CO₂ and brine consisting in equal molal concentrations of NaCl and CaCl₂. The experiments were repeated at various pressures, temperatures and salinities that are representative of conditions prevailing during CO₂ storage in deep saline aquifers. The dependence of CO₂/brine IFT on pressure and temperature is similar to that previously reported for the systems: CO₂/NaCl solution and CO₂/CaCl₂ solution. CO₂/brine IFT increases linearly with water salinity and the magnitude of this increase was found equal to the sum of the individual CO₂/NaCl solution and CO₂/CaCl₂ solution IFT increments, indicating a strong additive effect on IFT when the brine is composed of various salts.