An Experimental Study of Surfactant Alternating CO2 Injection for Enhanced Oil Recovery of Carbonated Reservoir

Core flooding experiments were conducted with the objective of evaluating near miscible surfactantalternating CO2 injection and the effect of surfactant concentrations on gas-oil and waterdisplacements in porous media. The core samples were provided from a low permeability mixed wetoil reservoir at 156 °F and 1900 psia. In addition, very few studies of surfactant adsorption oncarbonate minerals have been conducted. Hence, the surfactant adsorption on carbonate rock wasdetermined by core flooding and crushed tests. It was found that for the crushed rock, the requiredequilibrium time is approximately five hours, while it is more than four days for the flow-throughtests. Hysteresis effects demonstrated that the irreducible water saturations were 5 to 10% higher thanthe initial connate water saturation after drainage cycles during 5000 ppm surfactant solution.Furthermore, near-miscible surfactant alternating CO2 injection process led to a 4-17% increase in therecovery factor in comparison to water alternating gas process.