Performance of CO2/N2 Foam in Enhanced Oil Recovery

Abstract

Carbon dioxide (CO2) flooding is one of the attractive enhanced oil recovery process. Although it has several advantages, it suffers from early gas breakthrough due to low mobility ratio. The early breakthrough and mobility ratio can be improved by foaming CO2 gas. But CO2 is unable to generate the foam especially at supercritical condition (1100 psi at 31.10C) which is generally found in the reservoir. The CO2 foam gets weaker and weaker with an increase in pressure. It reduces the macroscopic sweep efficiency and hence the ultimate recovery. The difficulty of generating CO2 foam is overcome by adding N2 in a small fraction to enhance the foam generation of CO2 at supercritical conditions. This study shows how the addition of small quantity of N2 helps in generating the CO2 foam and performance of the novel CO2/N2 mixture foam in enhanced oil recovery. The goal of this study is to evaluate the oil displacement process by a novel foam system in which the CO2 and N2 mixture constitutes the gaseous phase. The experiments were carried out by flooding the core with CO2/N2 foam by imposing the condition above the supercritical CO2. The supercritical CO2 becomes denser and unable to generate the foam. To generate foam nitrogen is added to carbon dioxide to improve the CO2 ability for generating CO2 foam at supercritical conditions. The CO2/N2 foam performance is evaluated by comparing displacement efficiency of CO2 foam with CO2/N2 foam. In addition, the effect of foam quality by fixing the injection rate were investigated on CO2/N2 foam flooding performance.