Numerical Modeling of Transport Properties and Comparison to Laboratory Measurements

Abstract

Transport properties, such as permeability and electrical conductivity, are important in many geophysical and petroleum applications. The microstructure of a porous medium and physical characteristics of the solid and the fluids that occupy the pore space determine the macroscopic transport properties of the medium. The computation of macroscopic properties from the rock microtomography is becoming an increasingly studied topic. The transport properties are especially difficult to determine at the microscopic scale. The purpose of this paper is to test the applicabilities to numerically calculate the geometrical and transport properties (electrical conductivity, permeability, specific surface area and surface conductivity) of porous, permeable rocks, given the digital CT microtomography images. To better address the relationship between geometrical properties and transport properties, we use a number of artificial low, medium- to high-porosity Finney’s (1970) sphere packs. Numerically calculated transport properties are compared with analytical and empirical equations on the Finney pack. In particular, numerically computed permeability on the Finney pack agrees well with the permeability calculated from the computed formation factor using an empirical relationship on the same structure. This illustrates the consistence of resolving different transport properties on the same structure and the possibility of multiphysics coupling in the future. We also apply all the numerical simulations on the 3D X-ray microtomography of 23.6% porosity Berea Sandstone with 2.8 micron resolution. Numerical calculations of electrical conductivity, permeability and specific surface area on mm[superscript 3] image will be compared to the laboratory measurements with those parameters on cm[superscript 3] core samples. The upscaling issue will be discussed when we compare the numerical results with laboratory measurements at a different scale. We also analyze the image resolution impact on different properties to better understand the discrepancy between numerical computations and laboratory measurements. This paper provides a complete work on the numerical simulations on different physics at different scales. Numerical calculations are compared with analytic, empirical rock physics equations and laboratory measurements.