Semi-analytical estimates of permeability obtained from capillary pressure

Abstract

The objective of this research is to develop and test a new concept for predicting permeability from routine rock properties. First, we develop a model predicting permeability as a function of capillary pressure. Our model, which is based on the work by Purcell, Burdine and Wyllie and Gardner models, is given by: (Equation 1 - See PDF) Combining the previous equation and the Brooks and Corey model for capillary pressure, we obtain: (Equation 2 - See PDF) The correlation given by this equation could yield permeability from capillary pressure (and vice-versa). This model also has potential extensions to relative permeability (i.e., the Brooks and Corey relative permeability functions) - which should make correlations based on porosity, permeability, and irreducible saturation general tools for reservoir engineering problems where relative permeability data are not available. Our study is validated with a large range/variety of core samples in order to provide a representative data sample over several orders of magnitude in permeability. Rock permeabilities in our data set range from 0.04 to 8700 md, while porosities range from 0.3 to 34 percent. Our correlation appears to be valid for both sandstone and carbonate lithologies.