After many years' development, La,Sa & Xin oil fields in Daqing Placanticline have entered into extra high water cut stage. Polymer flooding has been widely applied in the fields. Along with polymer agent injection, physical property and fluids distribution of reservoirs have changed. This challenges the qualitative and quantitative interpretation of watered out zone in high water cut stage. So the present logging interpretation method for water flooded zone is difficult to meet the needs of logging interpretation of reservoir by polymer flooding in extra high water cut stage. In this paper, based on the logging response characteristics of polymer flooded reservoir and guided by reservoir petrophysical experiment, the method of distinguishing effectively flooded layer by polymer solution from ones by water flooding through log response characteristic analysis has been established. And on the base of symmetrical anisotropic effective medium conductance theory and according to the reservoir petrophysical experiment data, the paper gives a saturation calculating model for the reservoirs by polymer flooding. The new model can recognize the fluid connectivity of pore space and rock wettability change factor resulted by polymer flooding in saturation calculation. The comparison result with sealed coring analysis data shows that the water saturation calculation precision of new model is higher with average absolute error of 6.4%, which can meet the need of production. The saturation model provides a new technical means to calculate remaining oil saturation for polymer flooded reservoir in extra high water cut stage.

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