Evaluation on the Basis and Application Performance of a Modified Surface Active Oil-displacing Agent

The oil development has entered the water flooding stage in Changqing Oilfield. Due to the low reservoir permeability and the high oil viscosity, the water-flooding does not achieved the desired effect. A large amount of oil is retained in the reservoir due to the high water surface tension and oil-water interfacial tension. Currently, the performance of an oil-displacing agent is suitable for Changqing oilfield to mitigate this situation, but with high application cost due to its synthesis in an organic solution. In this study the oil-displacing agent is modified, and an amphiphilic oil-displacing agent is synthesized through aqueous polymerization. With addition of the oil-displacing agent, the surface/interface activity of water and oil changed significantly. The surface tension of water and oil reduces from 69mN/m to 25mN/m and from 21mN/m to 7.8mN/m respectively in the 1500mg/L oil-displacing agent at 60℃, and the oil-water interfacial tension reaches the ultra-low level. In addition, the oil-displacing agent has the good oil emulsification ability, and the emulsion shows stable performance. The core flooding experiment shows that the 2000mg/L oil-displacing agent can increase the oil recovery by 20% compared with the water flooding, and this meets the production needs in the oilfield. Since the oil-displacing agent contains a large number of chelating functional groups, so it can also chelate the heavy metal ions in the reservoir to prevent precipitation with incompatible anions in the injected water.