On the effectiveness of increasing oil recovery factors with ASP flooding and polymer flooding under the limit water-cut conditions

Taking the Xing'erxi ASP flooding test as an example,the paper discusses the issue of increasing oil recovery factor by ASP flooding under the condition of residual oil being dominant in reservoirs with a long-time 100% water-cut.After the ASP flooding,the oil recovery factor in the central well area of the Xing'erxi reservoir is increased by 19.46%,indicating that the ASP flooding is suitable for reservoirs with a high water flooding oil recovery factor and the remaining oil dominated by residual oil.The mechanism of ASP flooding is to improve oil-displacing efficiency by reducing interfacial tension and expanding its sweeping area.Whereas the polymer flooding can only increase oil recovery factor through enlarging the swept volume but cannot improve the oil displacement efficiency.Oilfield data and the numerical simulation of the Xing'erxi reservoir show that the polymer flooding can only enhace slightly the oil recovery in this type of reservoirs.