Gas-liquid surface characterization and liquid film thinning of Non-Aqueous foam

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 could 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 are performed to investigate differences in the stabilization mechanism between aqueous and non-aqueous foams. The results show that a non-aqueous foam had excellent oil tolerance in a bulk foaming test. Then, the stabilization mechanisms of foams are 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 occurs at the maximum surfactant concentration used which was 5.0 wt% for this set of tests, which indicates that the liquid film of FS22 non-aqueous foam was more stable. In a foam film thinning experiment, the thinning time of an aqueous foam system is shortened but the liquid film thickness is 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 indicates that its stability in the presence of an oil phase is excellent. These results are meaningful for the understanding of the stabilization mechanisms of oil-based foams and the employment of nonaqueous foams for enhanced oil recovery.