Role of Emulsification and Interfacial Tension of a Surfactant for Oil Film Displacement

The oil film after water flooding is a very important type of microscopic residual oil for an oil-wet reservoir. In this study, an artificial oil film model was designed to simulate the micro residual oil absorbed on the rock surface. Numerous experiments were carried out to explore the detachment mechanisms of two kinds of crude oil films and oil recovery performances in different fluid media with the flow rate. The results show that the increasing flow rate positively affects the oil film detachment but is still limited in the action area and displacement efficiency. It is also found that surfactants with different interfacial tensions (IFTs) and emulsification behaviors all can promote the dislodging of the oil film. The results show that the most important factor contributing to the detachment of the oil film is the emulsification rather than IFT reduction. Strong emulsification is useful to lessen the thickness of the oil film and disperse the oil droplets into a smaller size without considering the flow rate. This paper also provides evidence that, for the case of a higher proportion on heavy components of crude oil, strong emulsification capability is the chief driver for the oil enhancement mechanism for surfactant flooding.