Study On Emulsification Properties And The Oil Displacement Efficiency Of Surfactant-polymer System

Surfactant-polymer flooding is a kind of EOR technology that exerting the effect ofsurfactant and polymer sufficiently. The technique can both expand swept volume andimprove oil displacement efficiency. In the process of Surfactant-polymer flooding, theemulsion formed under the shearing action of rock pores after the injected agent contactingwith residual oil. Plenty of field tests and laboratory physical simulation experimentsindicated that emulsification can improve the oil displacement efficiency to some extent.Based on laboratory experiments, this paper researched the stability of emulsion underdifferent preparation conditions and the influence factors on the emulsion properties ofsurfactant-polymer system. At the same time, the interfacial tension, interfacial viscoelasticityand rheological properties between the flooding system and oil has been studied to make athorough analysis of the emulsion rules. A serious of core displacement experiments withdifferent water-cut were conducted in order to investigate the laws of surfactant-polymer/oilemulsification, and the influence of emulsification on displacement efficiency was discussed.The results indicated that: the stability of emulsion was enhanced with the increase ofstirring speed, the critical value of stirring speed is10000r/min. When the emulsifying timewas under10min, as the increase of emulsifying time, the droplets were smaller and moreuniform, and the emulsion became more stable. The stability of emulsion was enhanced withthe decrease of water content ratio by volume，there is a low phase transition point of theemulsion around the water-cut of30%, after phase transition point the type of emulsiontransforms from O/W to W/O. The emulsion becomes unstable along with the increase oftemperature. The oil/water interfatial films have been strengthened and the stability ofemulsion was improved as the increase of polymer molecular weight, polymer concentrationand surfactant concentration. The result of cores displacement experiment shows that, at thesame condition of water-cut, the emulsification of produced liquid was more apparently inlow-permeability cores than that in high-permeability cores. Compared with that inhigh-permeability cores, emulsification appears later and the droplets were smaller and moreuniform in low-permeability cores, but the enhance oil recovery effect was slightly poor. Inthe conditions of50%water-cut, emulsion system can enhance oil recovery by3%~6%, andin the conditions of90%water-cut, emulsion system can enhance oil recovery by2%~5%.