Critical Review of Interfacial Tension of CO₂-brine Systems: Implications for CO₂ Storage

Carbon capture utilization and storage (CCUS) constitute promising underground storage techniques to address the challenge of climate change. Subsurface storage of carbon dioxide depends on several factors like injectivity, formation characteristics, sealing integrity etc. One critical parameter is the interfacial tension (IFT) of the fluid-fluid system in question e.g., CO₂-brine IFT for CO₂ geo-storage. Importantly, the IFT influences the capillary pressure of the seal, which, in turn, controls fluid leakage. In addition, different fluid-fluid IFTs give rise to distinct relative permeability curves and residual saturations of the fluids, thereby impacting residual trapping characteristics. Successful application of EOR techniques is also dependent on the IFT of the carbonated water (CO₂+water/brine) and the oil in place given that the IFT controls fluid miscibility and flow. Numerous researchers investigated the IFT of fluid-fluid systems and its effect on capacity estimates for CO₂/H₂ storage as well as the expected performance EOR techniques. Associated trends, however, have not been critically analyzed before. Thus, this paper presents a critical review of published data sets on CO₂-brine IFTs. The significance of IFT for underground gas storage and EOR applications is detailed. IFT depends primarily on pressure, temperature, and salinity. The influence of pressure, temperature, and salinity on IFT and associated trends are analyzed. In addition, latest developments pertaining IFT measurements for sequestration purposes are discussed from a risk managing perspective. Finally, this study elucidates research gaps and presents a future outlook.