Application of Polyelectrolytes and Polyelectrolyte Complex Nanoparticles to Improve the Stability of CO2 Foam in Enhanced Oil Recovery

Abstract

This research focusses on the application of polyelectrolytes and polyelectrolyte complex nanoparticle system along with a nonionic surfactant to stabilize the CO2 foam used in enhanced oil recovery applications. The ratio and pH of the polyelectrolytes are optimized in order to generate nanoparticles that are stable. The interaction of the polyelectrolyte-surfactant CO2 foam and the polyelectrolyte complex nanoparticle (PECNP)-surfactant CO2 foam with crude oil in a high pressure, high temperature static view cell was studied. The view cell apparatus was useful in understanding the interfacial properties and stability of the CO2 foam in the presence of different crude oils. The PECNP-surfactant CO2 foam system was found to be more durable in the presence of crude oil. Additionally, the influence of polyelectrolytes on the critical micelle concentration of surfactants was also observed through the view cell tests. A high pressure high temperature rheometer setup was used to study the bulk rheology of the foam under shear 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 compared to the surfactant generated CO2 foams. Foam mobility tests were conducted through the design of a high pressure high temperature core flood apparatus. The setup was designed to include various flow paths for testing the durability and mobility of the foam. The different CO2 foam systems were tested in the presence of crude oil to determine the incremental oil recovery obtained by each system. Sequential flooding that involved a series of CO2 foam tests on a particular core presented results that further corroborated the results obtained during the view cell tests. The PECNP-surfactant foam proved to be the most stable foam in the presence of Mississippian crude oil and resulted in the highest incremental oil recovery compared to the other CO2 foam systems. It is imperative to understand the effect of PECNP injection on the core and this was tested by injecting the PECNP solution into a new 3 inch core. The recovered permeability was measured and the damage to the core was found to be insignificant. Through this research, a stable PECNP-surfactant CO2 foam was developed and proved to enhance the oil recovery by more than 50% after water flooding.