Stabilization of CO2 foam using Nanoparticles and Polymers for EOR applications

Foam Flooding is a promising Enhanced Oil Recovery technique dedicated for maximizing oil recovery by altering the wettability in favorable conditions and more importantly to improve the mobility ratio. Also foam flooding significantly can improve the macroscopic sweep efficiency by lowering the gas mobility. Limited stability of conventional surfactants for foam generation is one of the reasons why foam is not being widely used as a common EOR technique. Some of the anticipated approaches for foam stabilization is the addition of polymers, so called polymer enhanced foam and nanoparticles. The oil recovery by foam flooding mainly depends on the stability of the foam. At severe reservoir conditions, CO2 foam becomes more unstable due to water drainage and gas diffusion through the lamella. The petroleum industry is using several foaming agents to produce and stabilize the CO2 foams. These are mainly water-soluble surfactants, CO2 soluble surfactants, nanoparticles, and water-soluble polymers. The objective of this thesis is to analyze the synergic effect of surfactants, polymers and nanoparticles on foam stability. In this work, the CO2 foam stability was assessed using several novel polymers and nanoparticles. The foam was generated using alpha olefin sulfonate surfactant initially at different concentration and salinity to obtain optimum surfactant concentration. Later on, 8 different polymers were used at different concentration to analyze their effect on stability of foam. Foam stability was assessed by analyzing the half-life and texture of the foam during its life. Foam decay was studied to compare the destructive mechanisms between surfactant and polymer foam. These polymers were mainly acrylamide-based sulfonated and associative polymers that contain thermally stable monomers that increase the salt tolerance and thermal stability. In the last, nanoparticles were used to get the synergic effect of polymers and nanoparticles on foam stability at different concentrations. The foamability, foam stability, foam diameter, bubble count per unit area of the different foaming system was measured using dynamic foam analyzer. Results showed that the addition of polymers increases the viscosity of the foam which reduces the coalescence phenomena and film thinning however, the liquid drainage was not much controlled by polymer addition. Nanoparticles performed the best job in controlling the liquid drainage and enhanced the foam stability up to large extent when used in combination of polymers. The novel sulfonated polymers showed much better performance compared to the conventional partially hydrolyzed polyacrylamide (HPAM) polymer. For HPAM, the viscosity of the solution reduced at high temperature in presence of salts. However, associative polymers maintained a reasonable high viscosity in presence of salts that resulted in less film thinning so will play key role in refining mobility ratio. Hence foam stability could be enhanced up to large extent if a proper combination of surfactant, polymer and nanoparticles are used. The foam stability is also assessed using foam structure analysis and effect of salinity on CMC of surfactant is also investigated. This study helps in understanding the role of polymer molecular structure, molecular weight, degree of hydrolysis, and addition of nanoparticles on stabilization of surfactant foam for CO2 EOR.