Experimental study on the interfacial tensions of CO2-water binary mixture for CO2 storage safety

CO2 capture and geological storage (CCS) is an effective method to solve the problem of greenhouse gas emission. The CO2 storage in saline aquifers has a promising future with huge storage capacity compared to other storage candidates. The storage in saline aquifers is feasible technically but storage safety is of the main concerns. In this paper, the seal mechanisms of cap rock was analyzed which showed the seal performance is much related to the interfacial tensions (IFT) of CO2-water binary mixture in a given reservoir. The influence of temperature, pressure, salinities and CO2 solubility on the IFT was investigated using Tracker rheometer. With increase of temperature and salinity, the IFT becomes higher. On the contrary, the IFT decreases as the pressure increases. Storage in saline aquifers with high salinity may have better seal performance of cap rock in terms of salinity influence on the IFT. By Spearman correlation coefficient analysis method, it shows good negative correlation between CO2 solubility and IFT with the value of -0.91, which indicates that the storage capacity and seal performance of cap rock should be taken into consideration at the same time during the selection process of CO2 storage locations.