Irreducible Water Saturation from Capillary Pressure and Electrical Resistivity Measurements

This paper presents the results of capillary pressure and electrical resistivity measurements for three kinds of core specimens: Berea sandstone, Quartz and Limestone. Experimental data of resistivity index, formation resistivity factor, tortuosity, capillary pressure, and water saturation exponent in the air/brine system for these cores are reported. The electrical resistivities data are evaluated using the modified Archie's law. Capillary pressure and electrical resistivity versus brine saturation results show the existence of two irreducible water saturations corresponding to two different physical phenomena. The two values of irreducible brine saturations yield upper and lower limits that can be used to estimate the production capacity of porous media. The detailed analysis of the data has also shown a change in the value of the saturation exponent. This change would be also be observed at the irreducible brine saturation as obtained with capillary pressure data.