INFLUENCE OF DISPLACEMENT VELOCITY ON THE EFFECT OF THE ENHANCED OIL RECOVERY OF BINARY COMPOSITE FLOODING IN LONG CORE

In recent years, basic research and field tests on the application of chemical composite flooding technology have made great progress. The ultra-low interfacial tension of the composite flooding system can improve the oil washing efficiency and the viscosity can be enlarged to expand the volume and improve the heterogeneity. However, the low interfacial tension system will exacerbate interlayer heterogeneity after breakthrough in the formation, which is mainly affected by the injection rate of the composite system. Aiming at the common polymer/surfactant binary system, a three-pipe parallel heterogeneous long core with a big permeability difference was used to investigate the influence of injection speed on the oil displacement effect of the composite system. Three injection speeds (1m/d, 2m/d and 5m/d) were used in the experiment and the water flooding speed remains the same at 2m/d. The experimental results show that the increase of the injection rate and the increase of the injection pressure of the binary composite system will help to improve the recovery factor within a certain range. However, when the injection speed is too high, the channelling of the high permeability layer will be intensified, the heterogeneity will be strengthened, and the effect of improving the recovery factor will be reduced. When the injection speed is 1m/d, the best recovery enhancement effect can be obtained, which is 18.09%. The enhanced recovery efficiency mainly affects the medium and high permeability layers.