A Rigorous Approach to Estimating Permeability from Capillary Pressure Curves

Abstract

The absolute permeabilities of porous media have been traditionally estimated from capillary pressure curves using Swanson parameter (S _nw /P _c)_A. Different correlations between permeability and the Swanson parameter have been proposed for mid-perm sand cores and tight gas sand cores. After examining the definition of the Swanson parameter, a new parameter called Capillary Parachor (S _nw /P _c ⁁2)_max is defined in this article. Excellent correlations between the absolute permeability and capillary parachor have been developed on the basis of mercury injection and water/air capillary pressure curves. It is concluded that permeability (in md) of a porous medium is directly proportional to the mercury-capillary parachor (in Atm⁻²) with a proportionality factor of 0.054474. The permeability is proportional to the brine/air-capillary parachor squared with a proportionality factor of 0.00007. Analytical methods have been developed in this study to accurately determine the Swanson parameter and capillary parachor for well-defined hyperbola-shaped capillary pressure curves.

Acknowledgments

The author thanks ChevronTexaco for providing Chevron I/Board of Regents support fund in Petroleum Engineering throughout this research. The author is also grateful to the Office of Faculty Development and Academic Planning at the University of Louisiana at Lafayette for providing Faculty Summer Research Awards to financially support this study.