| A certain oilfield is one of the earliest in China to carry out polymer flooding technology.With the continuous deepening of polymer injection in the first class oil layers of the oilfield,it is facing the problem of a decrease in the main oil layer blocks suitable for polymer injection year by year,a rebound in water content in the already injected blocks,and a decrease in production.In order to increase and stabilize the production of the oil field,it is necessary to develop Class Ⅱ oil layers.Although polymer flooding has been industrialized in the main oil layer of the oilfield,it is still in the exploratory stage of developing Class Ⅱ oil layers.According to the development data of the oilfield,most of the remaining oil that can be used currently exists in the non-main oil layers of the oilfield.However,the non-main oil layers are generally reservoirs with a large number of small layers,low permeability,thin thickness,and stronger heterogeneity,and the geological environment is relatively complex.Therefore,it is urgent to carry out new research technologies for polymer flooding development of such oil layers.Polymer flooding mainly utilizes polymers to increase the viscosity of injected water,reduce the oil-water mobility ratio,and thereby improve oil recovery.Optimizing the injection parameters of polymers can efficiently tap out the remaining oil in non-main reservoirs.Therefore,analyzing the flow of polymer solutions in Class Ⅱ reservoirs under different conditions is crucial for optimizing injection parameters.This article is based on the guiding principle of oil layer classification in a certain oilfield,and statistics are made on the classification and development status of Class Ⅱ oil layers in Block B of the oilfield.Subsequently,a plan is developed for indoor simulation experiments.Firstly,the start-up mechanism of oil layers under different permeability is studied,and flow experiments are conducted using five parallel artificial cylindrical cores.The flow patterns of constant velocity method and constant pressure method are compared,and the conclusion is that under constant pressure conditions,The resistance of cores with different permeability remains unchanged.Based on this,under constant pressure conditions,the flow of polymer solutions under different injection parameters such as concentration,molecular weight,and water quality were compared,and the relationship map between injection parameters and reservoir compatibility was obtained.Through comparative analysis of the layout,it was found that under the conditions of a relative molecular weight of 15 million polymers,diluted water quality as sewage,and a configuration concentration of 500mg/L,the polymer solution has the strongest flowability and adaptability.Then,polymer flooding experiments were conducted in a homogeneous core model for different water qualities to study the effect of diluting polymer solutions with different water qualities on oil displacement under certain concentration or viscosity conditions.The results showed that selecting polymer solutions with low mineralization water and medium water quality had the best oil displacement effect.Finally,a constant pressure and constant speed comparative experiment was conducted to study the impact of two oil displacement methods on oil displacement efficiency.The results showed that under the same molecular weight,concentration,and diluted water quality conditions,using constant speed oil displacement improved oil recovery higher than using constant pressure oil displacement.The experimental results obtained through qualitative and quantitative analysis of polymer flooding solution injection parameters can effectively improve the oil displacement effect of Class Ⅱ oil layers in Block B of a certain oilfield,providing theoretical basis and technical guidance for the adjustment plan of measures to further improve the recovery rate of the block. |
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