Experimental Investigation of Permeability Alteration Caused by in-situ Precipitation During Low Salinity Waterflooding in Carbonate Oil Reservoir
H. Park, Y. Park, Y. Lee and W. Sung
Event name: 79th EAGE Conference and Exhibition 2017
Session: IOR / EOR
Publication date: 12 June 2017
Info: Extended abstract, PDF ( 746.91Kb )
Price: € 20
When low salinity waterflooding is applied to carbonate reservoirs, oil recovery is enhanced through the main mechanisms of wettability alteration by performance of Potential Determinant Ions (PDI) of Ca2+, Mg2+, and SO42- and rock dissolution. The nearby seawater is usually used for low salinity water injection. As the seawater which contains high concentration of sulfate ion is injected into the reservoir saturated with high TDS formation water, the chemical equilibrium is broken causing in-situ precipitation and rock dissolution. Particularly, impurities such as alkaline earth metal ions (Ca2+, Mg2+, Sr2+, Ba2+, etc.) in the formation water react with SO42- and form in-situ precipitation which brings the permeability reduction and inhibit the EOR efficiency in carbonate reservoir. Among the alkaline earth metal ions, we paid attention to Ba2+ ion. The barium ion is toxic in the dissolved state. In the presence of sulfate, in-situ precipitation of barite occurs which is the least soluble barium salt. This barite that may cause scale problem is known to increase solubility with the reservoir condition of high temperature, pressure, and high ionic strength. In this study, we attempted to analyse the effect of in-situ Ba2+-precipitation on permeability alteration during low salinity waterflooding in carbonate reservoir.