CO2 foam for enhanced oil recovery applications has been traditionally used in order to address mobility control problems occur during CO2 flooding. However, the supercritical CO2 foam generated by surfactant has a few shortcomings such as loss of surfactant to the formation due to adsorption, and lack of a stable front in the presence of crude oil. These problems arise due to the fact that surfactants dynamically leave and enter the foam interface. We discuss the addition of polyelectrolytes and polyelectrolyte complex nanoparticles to the surfactant solution in order to stabilize the interface using electrostatic forces with a view to generate stronger and longer lasting foams.

An optimized ratio and pH of the polyelectrolytes was used to generate the nanoparticles. Thereafter we studied the interaction of the polyelectrolyte-surfactant CO2 foam and the polyelectrolyte complex nanoparticle-surfactant CO2 foam with crude oil in a high pressure, high temperature static view cell. The nanoparticle-surfactant CO2 foam system was found to be more durable in the presence of crude oil. Understanding the rheology of the foam becomes crucial to determine the effect of shear on the viscosity of the foam. A high pressure high temperature rheometer setup was used to shear the CO2 foam for the three different systems and the viscosity was measured with time. It was found that the viscosity of the CO2 foams generated by these new systems of polyelectrolytes were slightly improved than the surfactant generated CO2 foams. Core flood experiments were conducted in the absence and the presence of crude oil to understand the foam mobility and the oil recovered. The core flood experiments in the presence of crude oil show promising results for the CO2 foams generated by nanoparticle-surfactant and polyelectrolyte-surfactant systems. This paper also reviews the extent of damage if any, that could be caused due to the injection of nanoparticles.

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