Abstract:

Previously [1], we examined the potential formation water (FW) Mg2+ for low-salinity (LS) EOR effect, where the incensement in divalent cations in FW was lowering the effect of LS water. In this paper, we demonstrate the importance of the same divalent cations in the injected water (both FW and LS water). We also try to relate the percentage of the divalent cations in the injected water to that in the FW to engineer the optimum concentration of the injected water and obtain the maximum oil recovery from sandstone reservoirs. Berean sandstone cores were successfully flooded with FW and LS water at 90°C. While injecting both brines, samples of the effluent were analyzed for pH. Oil recovery experiments with a double Ca2+ and Mg2+ concentration showed a lower LS water effect, meaning that the cores became more water-wet; however, the LS water effect was much greater when the amount of Ca2+ and Mg2+in the HS water was decreased by half. The results of this work relate oil recovery with LS water chemical compositions, temperature, ion exchange, and pH.