Enhanced oil recovery performance and mechanism of a wormlike micelles flooding system with zwitterionic-anionic surfactants

Surfactant-based wormlike micelles (WLMs) have been proven to be efficient in improving oil recovery due to their high viscosity and low oil/water interfacial tension (IFT). In this study, a novel WLMs oil displacement system was developed by mixing zwitterionic surfactant (Erucylamido propyl betaine, EAPB) and anionic surfactant (Sodium dodecylsulfate, SDS) at the mass ratio of 1.5:1. The viscosity, IFT and emulsification properties were studied by rheometry, interfacial tensiometry and bottle testing, respectively. The core and etched glass micro-model oil displacement tests were conducted to investigate the oil recovery efficiencies and the related mechanism. The results show that the EAPB-SDS combination system exhibits shear thickening compared to that of sole EAPB system due to the electrostatic attraction between SDS and EAPB. The viscosity is first increased and then decreased with the increase in pH, temperature and salinity. The IFT is decreased with pH, while it is first decreased and then increased with the increase of temperature and salinity. The EAPB-SDS combination system with mass concentration of 0.3% can enhance oil recovery by 25.91% and 19.79% after water flooding in homogeneous and heterogeneous cores, respectively. The high viscosity makes the system to exhibit good mobility control ability, while the low IFT contributes to the peeling and emulsification of residual oil, thereby significantly improving the oil displacement performance.