New advances in surfactant EOR mechanism: micellar solubilization and <italic>in-situ</italic> emulsification

Abstract

Reducing the oil-water interfacial tension (IFT) to ultra-low is believed the primary mechanism for the surfactant-based enhanced oil recovery (EOR) process. Field trials, however, have demonstrated that low-concentration surfactant flooding can also improve oil recovery without ultra-low IFT, and the evolution of surfactant solution after contact with crude oil in porous media has not been explored. In the preliminary work, our team conducted extensive research at the micro-and nano-scale, and proposed new mechanisms of "micellar solubilization and emulsification carrying". The solubilization capacity of micelle to oil was evaluated through light absorbance strategy, small-angle neutron scattering and transmission electron microscopy. The results indicate that micelle solubilization plays an important role in surfactant EOR. Microfluidics was used to view in-situ emulsification during surfactant flooding. The results show that in-situ emulsification improves oil recovery mainly through blocking and entrainment effects. Results from those works aid in understanding the interaction between surfactant solution and oil at low surfactant concentration, which is helpful for designing a surfactant-based displacing system for the EOR process.