CT coreflood study of foam flow for enhanced oil recovery: The effect of oil type and saturation

We present a CT coreflood study of foam, both pre-generated and generated in-situ, displacing oil, as a function of oil type and saturation. Foam generation and propagation are reflected through sectional pressure measurements. Dual-energy CT imaging monitors in-time phase saturations. With an oil less harmful to foam (hexadecane), injection with and without pre-generation of foam exhibits similarities: propagation of a foam bank through a core and later refinement of foam texture. In contrast, with an oil destabilizing to foam (with 20 wt% oleic acid in the hexadecane), pre-generation of foam behaves very differently from co-injection, suggesting very-different effects on foam generation and propagation. Without pre-generation, strong-foam generation is very difficult even at residual oil saturation (about 0.1); generation finally starts from the outlet (likely a result of the capillary-end effect). This strong-foam state propagates upstream very slowly. Pre-generated foam shows two stages of propagation, both from the inlet to outlet. First, weak foam displaces most of the oil, followed by a propagation of stronger foam at lower oil saturation. This dependence on injection method with harmful oil is not represented in currently applied foam models, which need further improvements for reliable prediction of foam for enhanced oil recovery.