A Comparison Between Two Anionic Surfactants for Mobility Control of Super Critical CO2 in Foam-Assisted Miscible EOR

Abstract

Abstract Carbon Dioxide (CO2) flooding is one of the most globally used EOR processes to enhance the oil recovery. However, the low gas viscosity and density result in gas channeling and gravity override which lead to poor sweep efficiency. Foam application for mobility control is a promising technology to increase the gas viscosity which leads to lower mobility and better sweep efficiency inside the reservoir. Foam is generated inside the reservoir by co-injection surfactant and gas. Although there are many surfactants that can be used for such purpose, their performance with Supercritical CO2 (ScCO2) is weak which leads to poor or loss of mobility control. This experimental study evaluates a newly developed surfactant (CNF) that was introduced for ScCO2mobility control in comparison with a common foaming agent, anionic Alpha Olefin Sulfonate (AOS) surfactant. Experimental work was divided into three stages: foam static tests, interfacial tension measurements, and foam dynamic tests. Both surfactants were investigated at different conditions. In general, results showed that both surfactants are good foaming agents to reduce the mobility of ScCO2 with better performance of CNF surfactant. Shaking tests in presence of crude oil showed that foam life for CNF extends to more than 24-hr but less than that for AOS. Moreover, CNF features lower CMC, higher adsorption and smaller area/molecule at the liquid-air interface. Furthermore, entering, spreading, and bridging coefficients interpretations indicated that CNF surfactant produces very stable foam with light crude oil in both DI and saline water, whereas AOS was stable only in DI water. At all conditions for mobility reduction evaluation, CNF exhibited stronger flow resistance, higher foam viscosity, and higher mobility reduction factor than that of AOS surfactant. In addition, CNF and ScCO2 simultaneous injection produced 8.83% higher oil recovery than that of the baseline experiment and 7.87% higher than that of AOS. Pressure drop profiles for foam flooding using CNF was slightly higher than that of AOS indicating that CNF is better in terms of foam-oil tolerance which resulted in higher oil recovery.