Study On The Influence Of Reservoir Physical Property Change On Oil Displacement Efficiency In The Late High Water Stage Cut Of Northern Xing District

After more than 40 years of development,the northern part Xingblock of Daqing Oilfield has entered the late stage of ultra-high water cut,and the comprehensive water cut rate has reached more than 95%,and the production is decreasing rapidly.In the late stage of extra high water cut,the "three major contradictions" are more prominent,and the reservoir physical properties and seepage characteristics are changed.It is necessary to study the seepage mechanism and oil displacement efficiency in the late stage of extra high water cut.In this paper,the Xingliu block of Daqing Oilfield is taken as the research object.Through the study on the changes of reservoir physical properties and the changes of seepage characteristics in the ultra-high water cut period,the changes of permeability and pore structure before and after long-term water flooding are clarified,and the different permeability is clarified.The conventional core,high-speed and high-magnification phase curves of the core are used to establish the relationship between the permeability-displacement condition and the displacement efficiency,which provides a theoretical basis for the efficient development of the oilfield in the later stage of ultra-high water cut.The research results are as follows:(1)In the mercury intrusion and nuclear magnetic resonance experiments,as the core air permeability decreases,the discharge pressure increases,the proportion of the smaller pore throat increases,the average pore throat radius and the enthalpy value become smaller,and the core storage capacity decreases.The fluidity of the fluid decreases,and the ability of the fluid to seep in the pore throat decreases.(2)In the study of high-strength scouring reservoir physical properties,long-term high-water scouring changes to some extent the rock indicates wettability,which is transformed from oleophilic to hydrophilic;in the oil scouring experiment,the core pore structure changes,and the medium-low permeability core is non-The homogeneity is enhanced and the permeability is reduced after flushing.The small pore throat of the high permeability core is enhanced by the seepage ability and the permeability is increased.(3)In the experiment of measuring the relative permeability curve between conventional and high-speed high-oil oil,the oil-water isotonic point shifts to the left with the increase of the air permeability of the experimental core sample,the oil phase permeability curve tends to be gentle,the slope decreases,and the residual oil state The water phase permeability is slightly increased,and the residual oil saturation of the high-speed high-phase phase permeability curve is reduced.(4)In the experiment of conventional oil displacement and high-speed high-speed flooding efficiency measurement,the oil displacement efficiency of different permeability cores is improved,and the average is improved.2.04%.Under the same displacement speed,increasing the displacement ratio has little effect on the oil displacement efficiency.Increasing the displacement speed is effective in the initial stage of speed increase,which can effectively improve the oil displacement efficiency.