CO2-Responsive Foam Coupled With Nanoparticles for Enhanced Oil Recovery

CO2 foam is widely used in tertiary oil recovery and can increase oil production and reduce greenhouse gas emissions. However, separation of the oil and water phases in the fluid produced by foam flooding is often difficult. CO2-responsive surfactants can control reversible changes in the molecular structure or properties of surfactants through addition of CO2 or N2, thereby turning the foaming ability of solvents either off or on. However, traditional CO2-responsive foam has poor stability, and good results are difficult to achieve in oilfield applications. In this work, through the use of micro-etching models, the morphological changes and flow properties of foam in porous media were observed. The effectiveness of the C12A-N20 foam in plugging and enhancing recovery in porous media was investigated using sand-packed materials. Finally, the demulsification effects of the foam flooding fluid before and after the N2 addition were compared. The experimental results showed that nanoparticles can effectively inhibit the coalescence of foam and enhance its stability. After the introduction of C12A-N20 foam into the sand-packed mixture, a significant enhancement of 14.1% in oil recovery rate was observed compared to that achieved with the injection of C12A foam, and the demulsification rate of the fluid produced by C12A-N20 foam flooding was greatly improved.