Effects of MgO, γ-Al(2)O(3), and TiO(2) Nanoparticles at Low Concentrations on Interfacial Tension (IFT), Rock Wettability, and Oil Recovery by Spontaneous Imbibition in the Process of Smart Nanofluid Injection into Carbonate Reservoirs

[Image: see text] Recently, some nanoparticles have been used to upgrade injected water into oil reservoirs to enhance oil recovery. These nanoadditives can be used in a variety of injectable waters, including smart/engineered water with special salinities. In this study, the performance of smart water containing different concentrations of magnesium sulfate (MgSO(4)) and calcium chloride (CaCl(2)) and 500 ppm of titanium dioxide (TiO(2)), γ-alumina (γ-Al(2)O(3)), and magnesium oxide (MgO) nanoparticles in interfacial tension (IFT) and contact angle reduction and oil production under imbibition of the chemical fluids was investigated. Based on the results, the IFT decreased more when ions and nanoparticles were present in the system. An optimum IFT of 4.684 mN/m was recorded for the nanofluid containing 2000 ppm of MgSO(4) + 500 ppm of MgO. The results of contact angle tests demonstrated improved saline water capabilities in the presence of nanoparticles and showed that a very effective reduction was accessible and highly hydrophilic wettability was obtained when using smart water with stable nanoparticles as a minimum contact angle of 18.33° was obtained by the optimal fluid containing nano-γ-Al(2)O(3). Finally, an ultimate oil production of 64.1–68.7% was obtained in six experiments with smart water and stable nanoparticles.