Improving oil recovery from carbonate rocks by low salinity water injection (LSWI) is recognized as an eligible technique, but it may cause severe problems due to complex reactions in both aqueous and mineral phases. In general, the principal mechanisms that show the effects of LSWI are not fully understood, but it is believed that changes in wettability and interfacial tension are the reasons for improving oil recovery from carbonate reservoirs, but the other factors which affect the porosity and absolute permeability are need to be monitored. While it is shown in simulations by injecting sea water, with high concentration of sulphate ions, the recovery of oil is considerably increased, but Mixing of this water with formation water could cause precipitation of calcium sulphate and barium or strontium sulphate (due to concentration of calcium, barium and strontium ions in formation water). Mineral scale deposition in petroleum reservoir is one of the problems when two incompatible waters are mixed. This work presents a comprehensive study that covers both scale precipitation effects and wettability and interfacial tension alteration by using CMG-GEM simulator.

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