The Research Of Polymer Flooding Reasonable Pressure System In Class-? Reservoir

Daqing oilfield of polymer flooding in Class-? reservoir has been industrial application since 2003.This reservoir is characterized by many layers,thin thickness,complex plane phase change,serious heterogeneity,connectivity variation and small injection production distance and so on.The development boundaries in Class-? reservoir differ greatly from the main ones.And different water cut stage has different requirements for injection production pressure system.Therefore,it is urgent to study the reasonable pressure system of polymer flooding in Class-? reservoir.The limit of formation pressure,injection pressure and oil well flow pressure in different development stages are determined,which guides the development of polymer flooding process in Class-? reservoir.In this paper,the Fault-East blocks of Class-? reservoir have been selected as the research object in the North Area.The reservoir engineering method and numerical simulation method are applied to study the influence of formation pressure,flow pressure and injection pressure on the polymer flooding under different injection speed.This study is based on the analysis of the changing regulations of water content,liquid production,oil production and dissolved gas oil ratio in different pressures of polymer flooding.The polymer flooding consists of five stages: the blank water flooding,the water cut down period,the water stationary period,the water recovery period and the subsequent water flooding.In order to determine the reasonable formation pressure of polymer flooding,the size relation between formation pressure and saturation pressure of blank water flooding and polymer flooding stage has been researched to analysis the variation law of development index under different formation pressure.Finally,the optimum formation pressure is determined near the saturation pressure(8.9MPa).The control standard is used to determine the reasonable range of oil well flow pressure and injection pressure,which includes the level of strata pressure,injection pressure is lower than breakdown pressure,water ratio of middle-low permeability reservoirs and polymer concentration rising speed.Finally,the reasonable flow pressure chart of polymer flooding at different stages is plotted.