Study On Relative Permeability Inversion For Radial Flow Under Different Scales

As an important data in oil field development, oil water relative permeability curve canreflect the oil water two phase flow law in porous media. At present, the relative permeabilitycurve is mainly obtained based on unidirectional seepage flow theory, while the near wellborearea of the actual reservoir is radial flow. Two flow patterns is different, which lead toinaccuracy for applying the current calculation theory of relative permeability curve to filedcondition. As a result, it's necessary to establish inversion methods of relative permeabilitycurve in radial flow, which is helpful to improve the accuracy of relative permeability curve,so as to further accurately predict the reservoir development performance.In this paper, relative permeability curve inversion is studied from core and field scales.Under core scale, according to the Darcy equation and Buckley Leverett displacement theoryin radial flow, radial JBN method is derived, Considering the adaptability of JBN method tocore size, through introducing G function, JBN method is deformed and improved JBNmethod is established.Selecting the weight ratio of pressure and production data as 5:1 to establish theobjective function, seleting the cubic uniform B spline function as the model of relativepermeability curve, the numerical inversion method of relative permeability curve isestablished for radial core model. Compared with analytical method by application example,the results indicate that a wide range of saturation is obtained by numerical inversion, averageabsolute error of the water and oil phase relative permeability is respectively 0.0081,0.0151,which is far higher than the inversion accuracy of the analytical method.Based on the numerical inversion method, the influencing factors research on the relativepermeability curve inversion effect is developed for the first time. Influences of ignoring theneglected factors and changing the displacement conditions on relative permeability curveinversion results are determined, the relationship between the influencing factors level andinversion precision is obtained, which is compared with unidirectional flow, the sensitivitydifferences of the same factor in different flow patterns is get, the corresponding relationshipof the same factor in different flow patterns is established. The results show that compared with unidirectional flow, the influence of the core shape factor on inversion effect becomesweaker in radial flow, the sensitivity of the remaining factors changes little.Based on the filed production datas, field scale inversion method for the relativepermeability curve in radial flow is established by using statistical analysis method. Thismethod not only can be used to calculate the mean relative permeability curve of a largereservoir, but also compute relative permeability curve around the single well area, relativepermeability curve obtained can reflect the actual rock and fluid properties, as well as theheterogeneity within the entire flow region, which is more representation of reservoircharacteristics and more practical.