Experimental study on surface-active polymer flooding for enhanced oil recovery: A case study of Daqing placanticline oilfield, NE China

Experiments on surface-active polymer flooding for enhanced oil recovery were carried out by detection analysis and modern physical simulation technique based on reservoirs and fluids in Daqing placanticline oilfield. The experimental results show that the surface-active polymer is different from other common polymers and polymer-surfactant systems in molecular aggregation, viscosity and flow capacity, and it has larger molecular coil size, higher viscosity and viscosifying capacity, and poorer mobility. The surface-active polymer solution has good performance of viscosity-increasing and viscosity retention, and has good performance of viscoelasticity and deformability to exert positive effects of viscosifying and viscoelastic properties. Surface-active polymer can change the chemical property of interface and reduce interfacial tension, making the reservoir rock turn water-wet, also it can emulsify the oil into relatively stable oil-in-water emulsion, and emulsification capacity is an important property to enhance oil washing efficiency under non-ultralow interfacial tension. The surface-active polymer flooding enlarges swept volume in two ways: Microscopically, the surface-active polymer has mobility control effect and can enter oil-bearing pores not swept by water to drive residual oil, and its mobility control effect has more contribution than oil washing capacity in enhancing oil recovery. Macroscopically, it has plugging capacity, and can emulsify and plug the dominant channels in layers with high permeability, forcing the injected fluid to enter the layer with medium or low permeability and low flow resistance, and thus enlarging swept volume. Key words: high water-cut oilfield, reservoir, surface-active polymer, oil-washing efficiency, swept volume, plug by emulsification, enhanced oil recovery