Correlations of physical properties of porous media

Abstract

The physical properties of porous media are important to the petroleum engineer and geologist in making evaluations of subsurface formations. Determining these physical properties is a problem because many of the determinations must be made by indirect measurement. A heterogeneous and complex pore structure together with the presence of clay in most naturally occurring porous media add to the magnitude of the problem. Being able to predict the physical properties of subsurface formations from other physical properties of the rock which could be measured accurately would be advantageous. These relationships between the physical properties have net been predicted accurately by theory or laboratory models. The approach to this problem in this investigation was to measure the physical properties of a large number of subsurface core samples and then to relate the physical properties by use of regression analysis. The physical properties measured were porosity, permeability, electrical formation factor, capillary pressure, and sonic velocity. Measurements were made on 568 samples composed of 478 sandstones and 90 carbonates. Prediction equations were developed for porosity, permeability, and electrical formation factor. The average per cent deviations obtained in these prediction equations are low enough that the equations have application in log interpretation and formation evaluation.