Abstract: Modified natural carboxylate/buffer base/polymer flooding was studied for the Gudao River Shoal Oil of the Shengli Oil Field after polymer injection flooding. First, interfacial activating and the influence of modified natural carboxylate , i.e., SDCM-2 was systematically investigated. Then, the effects of water flooding, polymer flooding and buffer base ASP flooding were studied by laboratory physical simulation experiments. When the concentration of mixed alkali (m(Na2CO3)∶m(NaHCO3)=1∶1) is 1.5% and the concentration of SDCM-2 is 0.1%, the oil-water interfacial tension reaches to a ultra-low level. The flooding efficiency of buffer base ASP flooding is 18％OOIP after polymer injection flooding. Finally, a visualized microscopic simulation flooding experiment was developed and the flow pattern of fluid in porous media was directly observed. Results show that the binding residual oil after polymer flooding deforms to be thinner and longer, then forms an oil bank through the capillary throat and moves to exit when the ASP system is added into the model. It is also shown that buffer base ASP flooding can improve flooding efficiency apparently by enlarging the swept volume and advances washing oil efficiency. Buffer base ASP flooding is one of the efficient methods to enhance recovery efficiency.

Key words: polymer flooding , microscopic simulation, laboratory simulation flooding, buffer base, ASP flooding