The Study And Application About The Reasonable Pressure Boundary Of Polymer Flooding Of Class?reservoir In The East Part Of South ?,Xing ? Block

In the Pu?oil layer of class?reservoir in the east part of South ?,Xing ?Block,the body of channel sand is becoming smaller,reservoir conditions are becoming worse,the general water cut,recovery percentage and the proportion of water flooded thickness in the stage of water flooding show high value.There are three aspects of problems existed since polymer flooding are applied: first problem is slow responding time,non-equilibrium response,low proportional response;second one is high viscosity reduction,high proportion of well with high backpressure and high submergence;third one is that parts of well fields have low pressure gradient and high flow pressure,which is unfavorable for expanding sweep area,impacts the development effect of polymer flooding.Since there is a close correlation between injection/production pressure gradient and development effect of polymer flooding,it is especially important that how to build a reasonable pressure gradient of polymer flooding.In this study,to figure out the effect factors and variation characteristics in the development of polymer flooding,we will build 3D refined geological model,proceed history matching by using numerical simulation software,research the relationship between reservoir pressure and the parameters of polymer flooding(such as the viscosity of polymer solution,injection intensity,injection speed,injection-production ratio,flow pressure of production well,submergence and production intensity of liquid),and summarize the variation characteristics of reservoir pressure in different stages,then finally build reservoir pressure forecasting model.Meanwhile,this study will discuss the mathematical model of inflow performance relationship(IPR)in different displacement stages and establish reasonable flow pressure boundary in different stages.The IPR of polymer flooding is the foundation of the analysis about production performance,the key of reasonably designing lifting mode and production systems.During the process of polymer flooding,production fluids which include polymers present obvious non-Newtonian flow characteristic,the rheological property of reservoir fluid changes greatly due toshear and degradation action.Therefore,general IPR model of water-flooding production well is not suitable for determining the IPR of this type of well.The research about reasonable flow pressure in polymer-flooding mechanical production well is rare at home and aboard currently,polymer-flooding production fluids present pseudoplasticity,fluid properties are influenced greatly by polymer concentration and water cut.Combining the rheological properties of the fluids in different stages of polymer flooding,under the premise of ensuring the maximum production rate,this paper will investigate the effect of high/low flow pressure to recovery factor enhancement,and determine the most reasonable flow pressure consequently.The flow pressure is 4.5~6MPa in the beginning of the polymer injecton,the flow pressure is 3.4~4.5MPa in the stage of water cut down,the flow pressure is 4~5.5MPa in the stage of water cut rising.According to the study about the relationship between injection-production parameters and injection-production pressure drawdown in classified well group,in order to maximizing production rate,this study will determine the boundary of reasonable pressure gradient in different stages of polymer flooding and the injection-production parameters required to get this boundary,and then optimize the adjustment of injection wells' parameters,enlarge the working parameters of production wells properly,improve the proportion of polymer existed in reservoirs,expand the sweep area of polymer in the reservoir.The result of this study is about indicating direction of the next step adjustment about the reservoirs,improving the effect of polymer flooding,and providing the references to the exploration adjustment of other polymer-flooding areas simultaneously.