Although CO2 foam flooding is a proven technology to improve oil recovery; it has been criticized for lack of long term stability in saline environment and in the presence of crude oil. To generate a more stable foam front in the presence of crude oil and to overcome the capillary forces destabilizing the foam lamella, polyelectrolyte complex nanoparticles (PECNP) conjugated with surfactant oligomers were introduced to the lamella generated by high salinity aqueous phase to improve the EOR performance and produced water compatibility of supercritical CO2 (scCO2) foams. The formation of vesicular structures containing electrostatically hinged complexes of PECNP and surfactant was verified via transmission electron microscopy (TEM) while the structural changes associated with molecular complexation were identified using Raman spectroscopy. Accordingly, optimized ratios of PECNP: surfactant were employed to generate the most stable scCO2 foam in high salinity produced water and to improve the recovery of the foam flooding process. Conducting core-flooding experiments in wide range of salinities indicated that the highest incremental oil recovery and the lowest residual oil saturation were achieved by prioritizing PECNP: surfactant scCO2 foam flood.
Keywords enhanced oil recovery, nanoparticles, foam film stability, produced water, CO2 storage