Experimental Study of Salinity Effects on Interfacial Tension between Carbon Dioxide and Brine

Water-Alternating-Gas (WAG) process has been an increasing interest for Enhanced Oil Recovery (EOR) to improve sweep efficiency by injecting water and gas such as carbon dioxide (CO2) alternately into oil reservoirs. Sequestration of CO2 is a method with great potential for reducing greenhouse gases emissions. An experimental study was conducted to measure the interfacial tension (IFT) between CO2 and brine of equal molar concentrations consisting of MgCl2 and NaCl. The experiments were conducted at various pressures (500, 1000 and 2000 psi), temperatures (27, 71 and 100˚C) and brine salinities corresponding to molarities, m= 0.045, 0.1 and 0.5 of each salt, representing the conditions of CO2 storage in deep saline aquifers. CO2/brine IFT increases with salinity and temperature but decreases with pressure. The sum of the individual IFT increments due to each salt contained in the brine is the total increase of CO2/brine IFT assuming an analogous behavior for other salts which indicates a strong additive effect on IFT when brine contains various salts. The IFT also increases due to cation valence. IFT 700 is used to measure the CO2/brine IFT. It computes the drop shape image and computes the IFT from solving algorithm based on the Laplace equation.