50 Chapter V Conclusion V.1 Conclusion Various investigations were carried out in this study to understand the effect of the addition of TiO 2 NPs on various brine salinity conditions. From this study, we can conclude that: 1. The pH value decreases as increasing brine salinity and TiO 2 concentration and the conductivity increases as increasing brine salinity and TiO 2 concentration. 2. The zeta potential of nanofluids decreases with the increased concentration of TiO 2 in various tested salinities. We attribute this behaviour to the pH solutions of nanofluids becoming more acidic with increasing TiO 2 concentration, hence promoting the protonation reaction of TiO 2 in the solution. In addition, increasing TiO 2 concentration as dispersed materials lowers the interparticle distance and reduces the repulsive force between particles, thus increasing the average particle size. 3. The interfacial tension value decreases with increasing salinity level and TiO 2 concentration. The highest IFT reduction is achieved by the combination of 32000 ppm NaCl + 100 ppm TiO 2, with decreasing value from 6.68 x 100 mN/m (using 500 ppm pure NaCl brine) to 1.14 x 100 mN/m. However, the decrease in IFT was insignificant. 4. The wettability shifts to a more water-wet condition as the salinity level decreases and the TiO 2 concentration increases. The highest contact angle reduction is achieved by the combination of 500 ppm NaCl + 100 ppm TiO 2, with decreasing value from 63.51⁰ (using 32000 ppm pure NaCl brine) to 27.92⁰. 5. The zeta potential of nanofluids relates to the measured contact angle of the crude oil-nanofluids-rock system, in which a higher negative zeta potential value yields a higher measured contact angle. This phenomenon suggests that the lowering negative zeta potential as a response to higher TiO 2 concentration promotes more TiO 2 adsorption on the rock’s surface and 51 results in a more water-wet rock condition while in contact with crude oil and nanofluid. V.2 Recommendation Some recommendations may be useful for the next experiments to complete this research: 1. It is necessary to examine the surface roughness on the thin section after the oil-brine interaction occurs on the thin section to determine the surface roughening phenomenon. 2.