How ZrO2 nanoparticles improve the oil recovery by affecting the interfacial phenomena in the reservoir conditions?

Using nanoparticles (NPs) in certain base fluids is the method that has been recently introduced for enhanced oil recovery (EOR), which seems to be the key solution for rock wettability alteration in carbonate oil reservoirs. This research attempts to offer a better understanding of the ZrO2 NPs' role in the EOR methods, with a special focus on the interfacial tension (IFT) between oil and water, the zeta potential, the contact angle, and the water and oil viscosity measurements. The results of contact angle measurements in different concentrations of NPs illustrate the highest contact angle reduction for 0.008 mol/L of NPs which changed the rock wettability from strongly oil-wet to a moderately water-wet condition by overcoming the available disjoining pressure in the system. In this specific concentration, the zeta potential measurement was the highest (~− 55.4 mV) which agrees well with the contact angle results. In addition, the measurements were all above − 40 mV which indicates a good stability for NPs in formation water (FW). The IFT measurements indicate that the smallest IFT value for 0.006 mol/L of ZrO2 NPs at 80 °C and 8.273 Mpa. This reduction is due to the adsorption of large oil molecules onto the NPs surface which prevents asphaltene precipitation on the interface between two fluids. Finally, the viscosity measurements at 60 °C show the reduction and increase of oil and FW viscosity with increased concentration, respectively. The oil viscosity reduction results from the breakdown of CC bonds in the large oil molecules by NPs, which is intensified at higher temperatures.