Research Of Improving The Development Effect Of Subsequent Water Flooding For Polymer-surfactant Flooding Reservoir

Relying on the polymer to improve water-oil mobility ratio and the surfactant to decrease oil-water interfacial tension,polymer-surfactant flooding has been widely performed in Shengli oil field and achieved favorable development performance.Some regions have come into the stage of subsequent water flooding after the end of injecting polymer and surfactant.According to the production data of these regions,oil increment of subsequent water flooding can account for over thirty percent of whole polymer-surfactant flooding.In order to improve the development effect of polymer-surfactant flooding,it's necessary to analyze the dynamic change law,study the influence factors of injection and production and form the effective injection and production adjustment model of subsequent water flooding.Based on the field data of polymer-surfactant typical region in Shengli oil field,injection and production dynamics including injection pressure,water injectivity index per meter,liquid production and water cut are analyzed.In addition,the quantitative characterization models of water cut and oil increment are established and applied in the six regions of Shengli oil field which are under the state of subsequent water flooding.Compared with Gudong region,Gudao region is poor in material basis as it was developed with polymer flooding rather than water flooding before polymer-surfactant flooding.As a result,Gudong region has achieved a better performance with larger decreasing range of water cut,longer effective time and more oil increment.After optimizing the typical polymer-surfactant flooding development region,reservoir numerical simulation model of polymer-surfactant flooding is established on the basis of geological and development characteristic.On the other hand,a concept model which can represent the region characteristic is also designed to study the change law of liquid production and water injectivity index.With that model,the index charts of different influencing parameter are drawn after making the sensitivity analysis.On the basis of reservoir numerical simulation model,the influence of adjustment measures including well pattern infilling,separate layer water injection,well pattern sparsing,liquid increment,oil well to injection and production and injection proration on the development effect of subsequent water flooding is studied.From the aspect of economical benefit,financial net present values of every measure are calculated at various oil prices.Finally,the optimal injection and production adjustment model is formed.For the polymer-surfactant flooding reservoir which is under the stage of subsequent water flooding,combined measures including production and injection proration,liquid increment and well pattern sparsing are recommended at low oil price.On the other hand,combined measures including production and injection proration,liquid increment and well pattern infilling and sparsing are preferred at high oil price.