Research On The Effect Of Factors Affecting Of Polymer Flooding On Sub-layers Reservoir And Seepage Regular Of Daqing Oilfield

The polymer flooding technology in Daqing Oilfield has been widely used in the main reservoir since the industrial application in 1996,and has become an important technical means for the oilfield to increase oil precipitation.But with the polymer injection block gradually turn into subsequent water flooding in the main reservoir of Daqing Oilfield,the remaining oil and recovery rate decreased gradually in the reservoir,we need to study on the method of polymer flooding for sub-layers reservoir in order to sustainable development of oil fields.Compared to the main reservoir,the sub-layers reservoir in general showed the following characteristics: the sedimentary environment changed greatly,reservoir thickness is relatively small,and the development scale of channel sand decreased significantly,lower permeability,the flow ability of polymer solution becomes poor and heterogeneity is obviously enhanced,plane and vertical heterogeneity becomes serious.The current study of injection parameters of major reservoir polymer has a certain field practice experience and theoretical achievements;therefore,it is necessary to study the optimization of viscosity,speed,injection timing and the injection mode of the three kinds of injection parameters,in order to improve the oil displacement effect of polymer flooding recovery in the sub-layers reservoir.According to the reservoir classification guidelines of Daqing Oilfield,first analysis,the division,the sedimentary characteristics,the exploration degree and the development present situation and existing problems of sub-layers reservoir in Daqing Oilfield,and then use artificial cylindrical core under the condition of two kinds of effective permeability,conduct the indoor physical simulation experiment by two kinds of molecular weight and four kinds of polymer concentration and analyzed the matching and injection of the permeability of cores and the different polymer concentration,polymer molecular weight of sub-layers reservoir,on this basis,using inter layer and inner layer two artificial core simulation of heterogeneous reservoirs with polymer injection effect to study different viscosity,speed,injection timing of polymers different injection mode of the three kinds of injection parameters for enhanced oil recovery and preferably the best injection scheme under the conditions of an equal amount polymer solution,at last,the optimal scheme is applied to the seepage field of the well pattern model,and studied the variation law of the saturation field.The effect of viscosity showed that the injection method of gradient reducing viscosity in polymer flooding recovery stage increased the maximum extent,the recovery degree of inter-layer core was 28.58%,the recovery degree of inner layer core was 29.23%;The effect of speed showed that the inter-layer core at low speed of 0.15 ml / min in polymer flooding has the best effect of oil displacement with the recovery degree of 27.57%,while the inner layer core is the opposite that is at high speed of 0.45 ml / min in polymer flooding increased the maximum extent with the recovery degree of 27.37%;The effect of injection timing showed that the moisture content of 30% in preliminary water flooding has the best displacement effect in the displacement experiments of cores in inter-layer and inner layer,the recovery degree of polymer flooding were 32.61% and 29.79% respectively.The injection method of the parameters which were preferred applied to the well network model,the changes of injection pressure,water content and recovery rate trend along with the change of injection volume of the inter-layer and inner layer model by oil saturation distribution graph,the key to improve the oil recovery of polymer is efficient use of the low permeability layer.Through the optimization design of injection parameters in polymer flooding,can effectively improve the oil displacement effect of polymer flooding in Daqing Oilfield,and provide practical experience and theoretical basis for the further improvement of the implementation of oil recovery measures.