Integrity Investigation of Macroscopic and Microscopic Properties of Non-Aqueous Foams for Enhanced Oil Recovery

Foam flooding is a crucial enhanced oil recovery technique for profile control during the oil displacement process. The stability of the foam is the key factor for the success of foam flooding, but typical aqueous foams generally lose their stability in the presence of hydrocarbons because of their low oil tolerance. Non-aqueous foams possess outstanding stability in the presence of hydrocarbons as a result of their unique properties. However, few studies have been conducted on the stabilization mechanisms of non-aqueous foams in the presence of hydrocarbons. In this study, comparative experiments were performed to investigate differences in the stabilization mechanism between aqueous and non-aqueous foams. The results showed that a non-aqueous foam had excellent oil tolerance in a bulk foaming test. Then, the stabilization mechanisms of foams were investigated in terms of surface dilatational viscoelasticity and liquid film thinning. For a non-aqueous foam system, the maximum viscoelastic modulus of 55 mN/m occurred at a surfactant concentration of 5.0 wt%, which indicated that the foam was more stable. In a foam film thinning experiment, the thinning time of an aqueous foam system was shortened but the liquid film thickness was increased by crude oil, whereas crude oil increased the thinning time of a non-aqueous foam system but decreased its liquid film thickness. In a non-aqueous foam system, the film could remain stable for hours before rupturing, which indicated that its stability in the presence of an oil phase was excellent. These results are meaningful for the understanding of the stabilization mechanisms of oil-based foams and the employment of non-aqueous foams for enhanced oil recovery.