Tuned water (brine with designed compositions) has proved to influence the oil recovery factor. One of the hypotheses supported to understand this technique involves decreasing the oil-water interfacial tension (IFT) and the rock’s wettability alteration, indicated by contact angle (CA) measurements. The literature lacks experimental data regarding the interfacial tension in oil-brine and contact angle in oil-brine-carbonate systems at reservoir conditions considering pressure and temperature, and reservoir rocks. The objective of this study is to obtain new data, at 5,000 psi and 63 °C, on brines with different concentrations. The experiments were carried out in three steps. First, the concentration of sodium chloride was varied 0, 0.25, 0.5, 0.75, and 1 times which is the quantity in a seawater sample. After identifying the best concentration of NaCl (75% of NaCl in original seawater), steps were taken to modify the amount of magnesium 0, 0.5, 1, 2, and 4 times, in the brine. Finally, the same proportions of sulfate were tested. The behavior of IFT and CA towards the function of these various concentrations was also investigated and discussed. Furthermore, the results reveal that the behavior of IFT was not predictable, as the salinity increases at times and decreases at others. This property probably depends more on the compounds in the brine than on the total salinity. Also, the images used to gauge the CA show a greater tendency toward water-wet conditions when the sulfate concentration decreases,and when the magnesium concentration decreases, the images present the opposite effect .