Effect of Sodium Oleate Surfactant Concentration Grafted onto SiO₂ Nanoparticles in Polymer Flooding Processes

The nanotechnology has been applied recently to increase the efficiency of enhanced oil recovery methods. The main objective of this study is to evaluate the effect of SiO₂ nanoparticle functionalization with different loadings of sodium oleate surfactant for polymer flooding processes. The sodium oleate surfactant was synthesized using oleic acid and NaCl. The SiO₂ nanoparticles were functionalized by physical adsorption using different surfactant loadings of 2.45, 4.08, and 8.31 wt % and were characterized by thermogravimetric analyses, Fourier-transform infrared spectroscopy, dynamic light scattering, and zeta potential. Adsorption and desorption experiments of partially hydrolyzed polyacrylamide (HPAM) polymer solutions over the unmodified and surface-modified nanoparticles were performed, with higher adsorption capacity as the surfactant loading increases. The adsorption isotherms have a type III behavior, and polymer desorption from the nanoparticle surface was considered null. The effect of nanoparticles in the polymer solutions was evaluated through rheological measurements, interfacial tension (IFT) tests, contact angle measurements, capillary number, and displacement tests in a micromodel. The surface-modified SiO₂ nanoparticles showed a slight effect on the viscosity of the polymer solution and high influence on the IFT reduction and wettability alteration of the porous medium leading to an increase of the capillary number. Displacement tests showed that the oil recovery could increase up to 23 and 77% regarding polymer flooding and water flooding, respectively, by including the surface-functionalized materials.