| Summary: | Nowadays, the addition of nanoparticles to polymer solutions would be of interest; however, the feasible property of nanoparticles and their impact on oil recovery has not been investigated in more detail. This study investigates the rheology and capillary forces (interfacial tension and contact angle) of nanoparticles in the polymer performances during oil recovery processes. Thereby, a sequential injection of water, polymer, and nanoparticles; Nanosilica (SiO<sub>2</sub>) and nano-aluminium oxide (Al<sub>2</sub>O<sub>3</sub>) was performed to measure the oil recovery factor. Retention decrease, capillary forces reduction, and polymer viscoelastic behavior increase have caused improved oil recovery due to the feasible mobility ratio of polymer–nanoparticle in fluid loss. The oil recovery factor for polymer flooding, polymer–Al<sub>2</sub>O<sub>3</sub>, and polymer–SiO<sub>2</sub> is 58%, 63%, and 67%, respectively. Thereby, polymer–SiO<sub>2</sub> flooding would provide better oil recovery than other scenarios that reduce the capillary force due to the structural disjoining pressure. According to the relative permeability curves, residual oil saturation (S<sub>or</sub>) and water relative permeability (K<sub>rw</sub>) are 29% and 0.3%, respectively, for polymer solution; however, for the polymer–nanoparticle solution, S<sub>or</sub> and K<sub>rw</sub> are 12% and 0.005%, respectively. Polymer treatment caused a dramatic decrease, rather than the water treatment effect on the contact angle. The minimum contact angle for water and polymer treatment are about 21 and 29, respectively. The contact angle decrease for polymer treatment in the presence of nanoparticles related to the surface hydrophilicity increase. Therefore, after 2000 mg L<sup>−1</sup> of SiO<sub>2</sub> concentration, there are no significant changes in contact angle.
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