Optimization Design Of Polymer Flooding Scheme For Class Ⅱ Reservoirs In Block Y Of Sazhong Development Zone

At present,Daqing Oilfield has entered the stage of high water cut,high difficulty and high cost development.Polymer flooding blocks of main oil layers are gradually reduced,the reserve potential of oil fields is obviously insufficient,and the potential of stable production replacement is smaller.Therefore,polymer flooding development of class II oil layers becomes one of the main ways of oil field production replacement,which is an important guarantee to realize the sustainable development of oil fields.The optimization degree of the second-class oil displacement plan directly affects the final recovery rate of polymer flooding.Therefore,in this paper,according to the development characteristics of the second-class oil layer in block y of Sazhong Development Zone,combined with the development history of the block,the optimization design of polymer flooding plan is carried out.In this paper,the geological characteristics,development and distribution of remaining oil in block y of Sazhong development zone are systematically analyzed.On the basis of fine geological research,according to different parameter design methods,relying on laboratory experimental research results,and referring to the mature experience of other class II reservoir blocks that have been injected,the polymer flooding scheme of block y of Sazhong Development Zone is designed,The injection parameters of polymer flooding in the second type reservoir are determined as follows:The polymer injection system was prepared with clear water and diluted with clear water.The amount of polymer was 1020 mg/L·PV,and the pore volume was 1.0 pv.In pre profile control and water plugging section plug,the injected pore volume is 0.05-0.06 pv,high and medium polymer are injected,the average polymer concentration is 1050 mg/L,the injection viscosity is 50 m Pa·s,and the injection speed is 0.14-0.15 pv/a;In med-term displacement slug,medium polymer are injected,the average polymer concentration is 1000 mg/L,the injection viscosity is 40 m Pa·s,and the injection speed is 0.16-0.18 pv/a;In subsequent protection section plug,medium polymer are injected,the average polymer concentration is 1000-1050 mg/L,the injection viscosity is 40-45 m Pa·s,and the injection speed is 0.16-0.18 pv/a.Gptmodel modeling software is used to build a phase controlled geological model for 2307 wells in the work area.The geological model is divided into 232 grids in X direction with a grid step of 26.5m,140 grids in Y direction with a grid step of 26.5m and a total of 1883800 grids.The development indexes of polymer flooding are predicted.The results show that the water cut of Y block is 97.0% at the end of blank water flooding.When injected with 0.33 pv,the water cut drops to the lowest point of 90.2%.The recovery degree of polymer flooding is 13.2%,the final recovery rate is 56.1%,and the recovery rate is 11.7%.According to the results of numerical simulation and the estimation of the selection standard and interim method of economic evaluation parameters of Daqing Oilfield Co.,Ltd.,it is estimated that the after tax internal rate of return can reach 26.2%,which is far higher than the industry benchmark rate of return of 6%.Therefore,the scheme is feasible.