Stability improvement of CO2 foam for enhanced oil-recovery applications using polyelectrolytes and polyelectrolyte complex nanoparticles

CO2 foam for enhanced oil-recovery applications has been traditionally used in order to address mobility-control problems that 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 because surfactants dynamically leave and enter the foam interface. We discuss the addition of polyelectrolytes and polyelectrolyte complex nanoparticles (PECNP) to the surfactant solution to stabilize the interface using electrostatic forces 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 in determining 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 was slightly better than the surfactant-generated CO2 foams. Core-flood experiments were conducted in the absence and 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 by the injection of nanoparticles. It was observed that the PECNP-surfactant system produced 58.33% of the residual oil, while the surfactant system itself produced 47.6% of the residual oil in place. Most importantly, the PECNP system produced 9.1% of the oil left after the core was flooded with the surfactant foam system. This proves that the PECNP system was able to extract more oil from the core when the surfactant foam system was already injected. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44491.