Document Type: Research Paper
REPSOL SINOPEC BRASIL
Tuned water (brine with designed compositions) has proved to influence the oil recovery factor. One of the hypothesis to understand this technique involves decreasing the oil-water interfacial tension (IFT) and the rock’s wettability alteration, which can be indicated by contact angle (CA) measurements. There is a lack of experimental data in the literature 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 work 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 from 0, 0.25, 0.5, 0.75 and 1 times the quantity in a seawater sample. After identifying the best concentration of NaCl (75% of NaCl in original seawater), the following step was to modify, in this brine, the amount of magnesium from 0, 0.5, 1, 2 and 4 times. Finally, the same proportions of sulphate were tested. The behavior of IFT and CA in function of these various concentrations was also investigated and discussed. The results reveal that, by increasing the salinity, the behavior of IFT was not predictable, increasing at times and decreasing at others. This property probably depends more on the compounds in the brine, than on the total salinity. The images used to gauge the CA show a greater tendency toward water-wet conditions when the sulphate concentration decreases and present the opposite effect for magnesium.