Empirical forms of Relative Permeability
The following models have been proposed to attempt to generalize a rock property, that by its very nature, alludes generalization. The laboratory data will undoubtedly be the best source of estimates. However, for identifying trends, and better classifying groups of similar properties, these models have value.
The general form of "Power Models", requires saturations to be normalized and then a best fit can be determined. Linear regression of the log of the variables can determine the exponent, n.
As stated in Reference 1, other models have been proposed. This area is closely tied to three phase relative permeability which I hope to ad in the near future.
1. Christiansen, R., Relative Permeability and Capillary Pressure, Petroleum Engineering Handbook, Vol I-747.