Solution Properties and Displacement Characteristics of in situ CO2 Foam System for Enhanced Oil Recovery

Carbon dioxide (CO₂) foam flooding has been shown to enhance oil recovery. However, large-scale adoption has been restricted by issues with transportation of CO₂ and equipment corrosion. In situ CO₂ foam generation can possibly overcome these issues. In this article, a CO₂ sustained-release system was first optimized for the CO₂ production rate and production efficiency. Then, the dissolution capacity and plug-removing ability of the sustained-release system were evaluated. Visual experiment and parallel sand pack flooding tests were conducted to verify the formation, propagation of in situ CO₂ foam, and the feasibility of this technique. The results indicated that the sustained-release system had benign ability to lower injection pressure and improve injectability. Moreover, in situ CO₂ foam flooding could obtain high oil recovery due to favorable mobility control ability, interfacial tension reduction capacity, and heterogeneity improvement. All the experiments demonstrated that the in situ CO₂ foam technique has great potential for enhanced oil recovery in the Bohai oilfield.