CALCULATION OF MIXED FORMATION WATER RESISTIVITY IN WATER FLOODED LAYER AT DIFFERENT WATERFLOOD STAGES

The mixed formation water resistivity in water flooded layer is a required parameter in the evaluation of residual oil saturation. Due to the ion exchange between injected water and original formation water in the middle-late stages of development, parallel conductance model can not be used to calculate the mixed formation water resistivity. A more appropriate method is needed. Firstly, the calculation method of resistivity for different mixed formation water is determined, in terms of the two different conditions of non-ion exchange and complete ion exchange. Then considering the actual injection process, the calculation model of dynamic mixed formation water resistivity is confirmed, which use ion exchange rate, calculated by the rock-electric experiment data and Archie Formula, to show the change rule of mixed formation water resistivity at different stages. Finally, the saturation calculation method of mixed formation water resistivity is presented to provide programming ideas for quantitative logging-interpreted mass data processing.