Methods currently being used to measure the electrical conductivity of fluidsaturated porous media are, highly sensitive to various capillary andelectrical effects. If these effects are not taken into account when makingelectrical measurements on cores, large errors in the computed values of theresistivity 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] intervalsalong 6 inch [152.4 mm] Berea cores in order to observe electrical andcapillary end effects. Computerized Axial Tomography (CAT Scan) was utilized toexamine fluid distributions within the sandstone cores under water-wet primarydrainage conditions. When the CAT Scan data was combined with electricalresistivity data, the magnitude of electrical contact resistances between thecurrent electrodes and the core can be estimated as well as the saturationvariation due to the capillary end effect. It was found that the contactresistances are substantial at low water saturations and in oil-wet cores.