Nowadays, the use of enhanced oil recovery methods, such as chemical flooding, is increasingly felt. Given the rapid developments in nanotechnology and its high efficiency, the rise of oil recovery through nanotechnology is the main idea of this research. Early water breakthrough in the producing well, and the unfavorable conditions of oil reservoirs such as high temperatures, the presence of different types of salts, incorporation of a variety of shear stresses into the polymer and the surfactants in the reservoir, limited the use of these solutions. In this study, the effect of silica nanoparticles on the performance of surfactant-polymer solution in the chemical flooding process was investigated. Two types of fluids including one solution of polymer-surfactant in water and another suspension of nanoparticles and a polymer-surfactant solution were evaluated using a physical model (sand pack) and flooding at different temperatures and salinities. The optimum concentration of the nanoparticle was determined (0.3). In addition to measuring the recovery factor, the main phenomena associated with flooding in the porous medium, including wettability and surface tension, were also investigated. The results of the experiments showed that flooding as 2PV with nanoparticle suspension increased 11% of oil production, compared to the non-nanoparticle polymer-surfactant flooding. It also converts the wettability of the reservoir rock from lipophilic to hydrophilic properties, due to the presence of nanoparticles. Also, measuring the interfacial tension showed that the solution with nanoparticles further reduce the interfacial tension between the water and the reservoir's oil, and consequently increase microscopic displacement efficiency.
