The use of surfactants in enhanced oil recovery: A review of recent advances

Currently, there is a widespread interest in the different methods of chemical enhanced oil recovery (EOR) as a result of the continuous decline in the conventional oil reserves and the accelerated increase in the global energy demand. Surfactant flooding is a well-established method of chemical EOR. This method has proven successful as it increases oil recovery through a combination of mechanisms. These include interfacial tension (IFT) reduction, wettability alteration, foam generation and emulsification. Despite its popularity, surfactant flooding is still challenged by issues including instability under harsh (or normal) reservoir conditions and excessive adsorption. These issues affect the expected oil recovery and thereby reduce the economic returns of EOR projects. Nevertheless, surfactants can be properly selected according to reservoir conditions and rock type. This is usually carried out using surfactant screening methods, which impose limits related to the IFT, surfactant adsorption and other factors under given temperature and salinity conditions. This paper reviews surfactant characterization and phase behavior, the role of surfactants in oil recovery, surfactant adsorption onto reservoir rock, and the application of surfactants in EOR on both laboratory and field scales. Finally, the review presents current research trends and future prospects based on recently published studies in the area of surfactant flooding.