When anomalous oils in productive reservoirs are displaced by water residual undisplaced oil remains. For calculating the volume of the unrecovered oil, most studies have been of homogeneous reservoirs. In the present paper, the residual volume is assessed using an inhomogeneous-stratified-model. The inhomogeneity of the strata is described by the random distributions of Weibull or Pearson (gamma-distribution), which are characteristic of oilfields possessing anomalous properties. A parametric study is made of four known schemes of areal flooding: two-point (straight line), five-, seven-, and nine-point. The obtained estimates of the volume of the residual oil can be used for rational selection of the parameters for exploiting anomalous oilfields.