Study On Influence Of Chemical Oil Displacement Agents On Produced Liquid's Stability

Surfactant/Polymer-Flooding is one of the most applied chemical flooding technologies of tertiary oil recovery in many countries all over the world, which has the advantage of improving the recovery of remaining crude oil. But the produced fluid flooded by surfactant and polymer is a complicated and mixed emulsion, which consists of different kinds of stable emulsions, such as O/W,W/O and W/O/W emulsions, resulting in a difficult oil/water separation.In this paper, the effect of polymer and surfactant on apparent viscosity, droplet size and oil-water interfacial dilational viscoelasticity and the stability, demulsification has been studied by using laboratory prepared W/O emulsion simulating on-site produced liquid. The results show: The stability of W/O emulsion is closely related to the prepared critical shear strength. The emulsifying extent of emulsion prepared with speed 1600r·min-1and mixing time of 10min is close to the actual situation. Polymer and surfactant can increase the viscosity of W/O emulsion, thereby enhancing the stability of the emulsion. The viscosity of emulsion reaches a maximum value when the concentration of polymer is 400 mg·L-1, while the emulsion viscosity increases with the surfactant concentration increasing. The increasing of the concentration of polymer and surfactant can lead to droplets size in W/O emulsion decreasing and distribution concentrating. The effect of surfactant on the particle size is greater than the polymer's. Polymer and surfactant can change the rheological of interfacial films, increase dilational modulus of oil-water interface, and enhance the intensity of interfacial films and the stability of the emulsion. The results obtained from this study illustrate that the effect of polymer and surfactant on the emulsification of crude oil is synergetic effect. Based on the above laws, heating method is been used to study the stability of the emulsion, and found that J211 is a better-demulsifier. The final dehydration rate of emulsion are over 90% and the effect of demulsification is satisfying when the heating temperature is 50℃and the concentration of J211 is 60mg·L-1.