Study On Oil-water Seepage Law Of Low Permeability Reservoir Based On NMR And Relative Permeability Experiment

Based on the existing problems in XL oilfield water injection development,this paper studied the microscopic occurrence of reservoir fluid,oil-water seepage law and displacement mechanism through nuclear magnetic resonance?NMR?test and oil-water relative permeability test.Combined with the development characteristics of the oilfield and the main influencing factors of the water displacement law,point out the development potential of this type of reservoir in,and provided theoretical basis and suggestions for the next step in formulating plans to improve the development effect.The study results showed that:1.The heterogeneity of reservoir pore structure in XL Oilfield is relatively strong.According to the core NMR T₂ spectrum conversion,the pore size distribution of the core in this block is obtained,and on this basis,the occurrence location and storage amount of movable fluid and residual oil are quantitatively characterized.2.The influence of pressure gradient,injection multiple,permeability and reverse displacement on microscopic oil-water occurrence was studied by NMR test.The effects of injection speed,pressure gradient,injection multiple,permeability and water cut on core flooding efficiency are studied by indoor relative permeability test.On the basis of the study of water flooding law combining micro and macro,the development potential of this kind of low permeability reservoir is pointed out,and the measures and suggestions to improve the development effect are put forward.3.XL Oilfield reservoir facies permeability curves are mainly divided into two types:water-phase upward concave type and water-phase linear type.The relative permeability curve of XL reservoir is normalized by the average saturation method,and the empirical formula of phase permeability curve in different development stages of the reservoir is established.4.The relative permeability curves of cores at different development stages in XL Oilfield are slightly different,but generally show similar characteristics:narrow two-phase region,high irreducible water saturation,and low final value of water relative permeability.Comparing the characteristic parameters of normalized permeability curve between the initial development stage and the later encryption stage,it shows that the initial development effect is slightly better than the latter.5.According to the normalized relative permeability curve,dimensionless index curves of XL Oilfield at the initial stage of development and the later stage of infilling are calculated.Dimensionless oil production index is close to linear decline.Dimensionless liquid production index begins to rise in the middle water cut stage,and increases rapidly in the high water cut stage,with a small final value.The analysis shows that the potential of liquid extraction in this oilfield is small,and it is relatively difficult to achieve stable production by liquid extraction.