Modified seawater EOR fluid for carbonate reservoirs

Low salinity of water flooding was studied as EOR fluid for carbonate and sandstone utilising its ability to interact with the rock surface. In this study, we introduced a chemical that can be applied in carbonate reservoirs to increase the oil recovery as alternative to low salinity or seawater flooding. A new method was employed the ability of a chelating agent to sequester metal ions in solution and prevent any solid precipitates in the reservoir. Seawater was used without desulphonation without any tendency to interact with the formation brine. The effluent samples from coreflooding were analysed to determine the dissolution caused by the chelating agents and its impact on the oil recovery. The increased recovery during coreflooding is attributed to dissolution of carbonate rock surface, liberation of oil, and IFT reduction due to the high pH injected fluid (pH > 11). Other mechanisms contribution was proved as well.