Defining the optimum properties of chelating agents to be used as EOR fluid for sandstone reservoirs

Many laboratory core flood investigations proved the increase in the oil recovery by applying low salinity water. However, till now the main mechanism of the oil recovery is debated. Recently chelating agents have been proposed as chemical enhanced oil recovery fluids that can be used along with the sea water to recover oil from sandstone and carbonate reservoirs. Chelating agents have the ability to decrease the salinity of the injected water and increase the recovery better than low salinity water flooding with low cost compared to diluting the sea water. In this paper we will define the optimum pH, concentration, and type of the chelating agent by conducting series of core flooding experiments. First, we changed the pH of chelating agent between 10.7 and 12.2 and the oil recovery was determined for each experiment. Second, the optimum concentration was identified by changing the concentration of the injected fluid and comparison of the recovered oil achieved for each experiment was conducted. Finally, the best chelating agent was selected by comparing between the oil achieved by two different types. The results showed that high oil recovery up to 30% of the original oil in place was achieved by EDTA chelating agent diluted from an initial concentration of 40 wt% using raw sea water has the same composition of Arabian Gulf sea water. The optimum pH value should be greater than 12. In addition, a concentration of 5wt% or greater should be used. EDTA-based chelating agents yielded higher recovery compared to HEDTA-based chelating agents.