Alkaline assisted CO2-foam for improving heavy oil recovery

Dissolution of CO2 in heavy oil results in a significant reduction in the oil viscosity. However, CO2 injection in viscous oil reservoirs lacks acceptable sweep efficiency due to a very high mobility of CO2. Co-injection of CO2 and an appropriate surfactant can generate CO2 foam in situ and provide a means of controlling CO2 mobility, improving sweep and hence oil recovery. Foam injection has been studied extensively in the past, but in the majority of these studies, foam has been investigated in absence of crude oil. It is known that the stability of foam is adversely affected by crude oil and this problem has been a major obstacle in application of foam injection for enhanced oil recovery (EOR). In
this paper, we present the results of a comprehensive series of sight glass experiments on foam stability in the presence of different heavy crude oil samples. Through these experiments, we have evaluated and compared the performance of a number of surfactants for foam generation. We have also tested the impact of three different alkalis (NaOH, Na2CO3, and borate) on foam
stability.