Several correlations have been proposed for prediction of three-phase relative permeability from two-phase data or from saturation/capillary-pressure relationships. These include the models of Stone, Hirasaki, Corey et al., Naar and Wygal, Land, Aleman, and Parker et al. This paper compares predictions of these models with predictions of two additional models (saturation-weighted interpolation and true-linear interpolation). The comparison is made using all the published three-phase experimental relative permeability data complete enough for application of the models.

The comparison shows that the models are often not very good predictors of the experimental data. This points out a need for better relative permeability models in cases where three-phase flow may have a significant effect. In most cases, straight-line interpolation or saturation-weighted interpolation between the permeabilities at the two-phase boundaries of the three-phase flow region provided a better fit of the experimental data than did the theoretically-based models.

The paper also demonstrates the utility of comparing the effects of different relative permeability models before using them in a reservoir simulation. Sometimes the result of a simulation can be heavily biased by the choice of relative permeability model used.

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