Techniques for Measuring the Electrical Properties of Sandstone Cores

Abstract

ABSTRACT Methods currently being used to measure the electrical conductivity of fluid saturated porous media are highly sensitive to various capillary and electrical effects. If these effects are not taken into account when making electrical measurements on cores, large errors in the computed values of the resistivity index (I) and the Archie saturation exponent (n) can occur. Resistivity was monitored at 1 inch [25.4 mm] and 2 inch [50.8 mm] intervals along 6 inch [152.4 mm] Berea cores in order to observe electrical and capillary end effects. Computerized Axial Tomography (CAT Scan) was utilized to examine fluid distributions within the sandstone cores under water-wet primary drainage conditions. When the CAT Scan data was combined with electrical resistivity data, the magnitude of electrical contact resistances between the current electrodes and the core can be estimated as well as the saturation variation due to the capillary end effect. It was found that the contact resistances are substantial at low water saturations and in oil-wet cores.