Experimental Study of Biochemical EOR in Oil-wet Fractured Carbonate Reservoirs

Most fractured carbonate reservoirs are characterised by a highly permeable fracture zone surrounded by a low permeability oil-wet matrix. These features make the displacement of oil from the matrix into the fracture almost impossible during water flooding. This study aims to present the results of core flooding with the biopolymer ‘Xanthan Gum (XG)’ in combination with a biosurfactant to enhance water imbibition into oil-wet fractured carbonate rocks. Scanning Electron Microscopy (SEM) also was employed to confirm the existence of the biopolymer and biosurfactant at the surface of the rock slice as a result of chemical flow through the system. The results showed that ultimate oil recovery levels from oil-wet fractured carbonate cores for the aforementioned system was ۷-۹ %, which can be attributed to the drive mechanisms of temporary fracture plugging (reducing fracture permeability by ۱۸.۳%) as well as mobility ratio improvement due to the biopolymer and wettability alteration by the biosurfactant.

Keywords:

Fractured carbonate reservoir , EOR , Core flooding , Biopolymer , Biosurfactant , SEM.