The Influence of Different Ions on the Performance of Low Salinity Water Flooding

In the recent decade, low salinity water flooding attained remarkable attention as a pioneering method for recovering oil. However, this method has several risks. To decrease the potential risk of conflict between injected water and rock /brine/crude oil system, the ion concentrations in injection water should be optimized. In this work, injection water composition during low salinity water flooding in a core model of carbonate reservoirs was simulated based on maximizing wettability change and minimizing compatibility. The optimum ion concentrations in injection water were obtained from geochemical software (PHREEQC) which was coupled with ECLIPSE software and a genetic algorithm. The optimum conditions of injection water were provided in low concentration of sodium ion (186 ppm) and high concentration of sulfate ion (7064 ppm). The optimization process based on the genetic algorithm was stopped after 764 times running of scenarios. The average recovery factor was obtained near 0.141 and the results presented that the average recovery factor was not dependent on calcium and chloride ions concentration ranges. Hence, these ions were not effective in the optimization process. However, the average recovery factor had a strong relation to sodium and sulfate ion concentrations.