Application and research progress of CO2 foaming system for oil displacement in oil and gas field development: A review and prospect

CO₂ foam system has the functions of oil displacement, plugging, and fracturing, and plays an important role in improving oil and gas production. In this paper, the effectiveness and mechanism of different surfactant systems for CO₂ foam and the methods to stabilize CO₂ foam are reviewed. The effectiveness and mechanism of ionic, nonionic, and Gemini surfactant systems for CO₂ foam were analyzed. The research status of CO₂ foaming agent system, gas-soluble CO₂ foaming agent system, and CO₂ intelligent response foaming agent system based on anionic, nonionic, and zwitterionic compounds was described. The mechanism of polymer and nanoparticles stabilizing CO₂ foam system was also discussed. Through investigation, it is found that the performance of CO₂ foam system compounded with various chemicals is better, and the research is relatively perfect and diversified, so we can pay attention to the refinement of the compounding process in the future. Sulfonation and modification of surfactants can further improve the properties of surfactants. The characteristics of Gemini surfactants, supercritical CO₂, and CO₂-sensitive surfactants can be used to make CO₂ foaming agent have the characteristics of easy recovery, sustainability, anti-corrosion, on–off control, and fluidity control. There is still room for development of such surfactants. Using polymers and nanoparticles to stabilize foam is the future development trend. This paper provides guidance for the further development and field application of highly effective CO₂ surfactant.