CHEMICAL FLOODING OF OIL-RESERVOIRS .2. DISSOCIATIVE SURFACTANT-POLYMER INTERACTION WITH A NEGATIVE EFFECT ON OIL-RECOVERY

The presence of polymer and surfactant in injection water will improve the oil recovery during a water flood. The flooding method is termed low tension polymer water flood. During the flooding process both chemicals are present in the aqueous microemulsion phase. This paper gives a discussion of possible synergistic effects between the surfactant and the polymer in a dynamic flood situation. Core flood experiments were conducted using an alkyl xylene sulfonate, xanthan, model oil (n-heptane), NaCl brine, and Berea sandstone cores in the two-phase region at 50 degrees C. Surprisingly, at low surfactant concentration, the flooding behaviour of the surfactant is influenced by the presence of polymer in a negative way regarding oil recovery, even though a dissociative surfactant-polymer interaction is observed in static experiments. The polymer appears to have a negative effect of the flow performance of the surfactant in the porous media possibly owing to very large micellar aggregates.