The Experimental Research On Foam Compound Flooding To Enhance Oil Recovery Further After Polymer Flooding

After a stage of very high water cut of exploiting about 40 years in Daqing Oil-Field, it is more and more difficult to stable the production of this oil field. Therefore, several projects for EOR have being carried out. Polymer flooding becomes one of the measures to stable the production. But there is still a mount of remaining oil after polymer flooding. How to enhance oil recovery further after polymer flooding becomes a hot spot to be discussed.Through the experimental research, foam compound flooding system is selected with the function of ultra low interfacial tension. The influences factors to the foamability of foam compound flooding system has been discussed, such as the concentration of surfactants, polymer and alkali, salinity, temperature and the exist of crude oil. This flooding system has the strongest foamability which the concentration of alkali reaches 0.3 percent. Alkali is benefit to low the interfacial tension, but it has a bad effect on the foamability of this system, so it must reduce the amount of alkali in the condition the extra low interfacial tension. Through the flow test of the compound flooding system, we can conclude that foam can reach the dynamic balance of debubble and regeneration in the process of advance movement, this foam compound flooding system is easy to reaches to the bigger pore path, and it can keep higher resistance, which shows that foam has ability of selective blockage.This paper emphasizes the experimental research of the foam compound flooding system implemented in the nonhomogeneous cores, considering with gas-liquid ratio, rate of advance, permeability coefficient of variation of cores, viscosity of crude oil, and the influences of shear to the effects of this compound flooding system. The result shows that the more gas-liquid ratio and the higher flooding rate, the more the oil recovery of this compound flooding increases. With the certain gas-liquid ratio, the recovery increases on the basis of the recovery of polymer flooding as the coefficient of variation increases in the range from 0.6 to 0.8. As the coefficient of variation reaches 0.72, the extent of recovery enhanced reaches the max value, which shows the selectivity of foam flooding system to the nonhomogeneous oil layers. To sum up, foam compound flooding system can enhance oil recovery notably, which is 15-20 percents after polymer flooding. Foam compound flooding which is a new ternary recovery method is developed on the base of ternary compound flooding, and it concentrates the merits of ternary compound flooding and common foam flooding, so it can enhance oil recovery notably and has a widely developmental foreground.