Pore-scale modeling of electrical and fluid transport in Berea sandstone

Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. ABSTRACT The purpose of this paper is to test how well numerical calculations can predict transport properties of porous permeable rock, given its 3D digital microtomography ͑␮CT͒ image. For this study, a Berea 500 sandstone sample is used, whose ␮CT images have been obtained with resolution of 2.8 ␮m. Porosity, electrical conductivity, permeability, and surface area are calculated from the ␮CT image and compared with laboratory-measured values. For transport properties ͑electrical conductivity, permeability͒, a finite-difference scheme is adopted. The calculated and measured properties compare quite well. Electrical transport in Berea 500 sandstone is complicated by the presence of surface conduction in the electric double layer at the grain-electrolyte boundary. A three-phase conductivity model is proposed to compute surface conduction on the rock ␮CT image. Effects of image resolution and computation sample size on the accuracy of numerical predictions are also investigated. Reducing resolution ͑i.e., increasing the voxel dimensions͒ decreases the calculated values of electrical conductivity and hydraulic per-meability. Increasing computation sample volume gives a better match between laboratory measurements and numerical results. Large sample provides a better representation of the rock.