Experimental investigation of mixed-salt precipitation during smart water injection in the carbonate formation

Abstract

Smart waterflooding is a novel enhanced oil recovery method to increase oil production, which have myriad advantages over conventional waterflooding. The success of smart water flooding is deeply dependent on a thorough understanding of the interaction mechanisms among reservoir rock, formation water, and the injection water. Most of the performed researches into increasing sulfate ions concentration during the smart water injection process is from an enhanced oil recovery point of view, and a few works mention the single salt precipitation in this process. The main objective of this research is to experimentally examine the mixed salts precipitation as a field challenge, which may occur during smart water injection in a carbonate formation.For this purpose, several lab methods are conducted to evaluate the benefits and challenges in low salinity and smart water injection process. The water compatibility tests are performed to investigate the scaling potential in different injection/formation brine mixtures at 80 °C and ambient pressure. Moreover, the zeta potential is measured for carbonate particles dispersed in brine solutions to assess the wettability alteration due to interactions between water ions and rock surface. The results indicated that high concentrations of sulfate within smart water lead to the formation of sulfate scales, when mixing smart water with formation water. Therefore, using the optimum concentration of sulfate ions through smart water shall be considered. Moreover, the findings highlighted that the usage of SM2S within the injection water could be taken into account as the optimum case due to emerging acceptable scale tendency, wettability alteration, and incremental oil recovery potential in comparison to the other injection water.