Title: Fundamental Studies on the Influence of Adding Surfactants into Injection Water in Water Flooding
Abstract: Because of the high interfacial tension between water and oil, the injection pressure of water in water flooding is fairly high and the subsequent oil displacement efficiency is rather low. Then the improvement was aimed for the reduction of injection pressure and the efficient displacement by adding a small amount of surfactant into the injection water. Surfactants used were Polyoxyethylenenonylphenylether HLB=17.1 and 12.6 as nonionic, and SDBS as anionic. These were separately used as water solutions of 300ppm in concentration without any additives like alcohols as co-surfactants.Results are summarized as follows.(1) Adding a surfactant into the injection water can reduce the injection pressure surprisingly even if the concentration of the surfactant is as low as 300ppm, which is 1/50 to 1/100 of that in the low concentration surfactant flooding. Results were correlated with the capillary number as shown in Fig. 10.(2) 300ppm surfactant-water solution was able to increase the oil recovery. This may be caused by the snap-off mechanism proposed by ARRIOLA et al.(3) krw/kro decreases with decreasing the interfacial tension, that is to say, the oil gets to flow easily compared to the water as the interfacial tension decreases. This effect was related to the shift of residual oil saturation with the interfacial tension.