A technique used for the determination of the electrical properties of a shaly core sample. The sample is flushed with brines of different salinities, and the conductivity determined after each flush. A plot of the conductivity of the sample (C₀) versus the conductivity of the brine (C_w) gives the excess conductivity caused by clays and other surface conductors. Then, using a suitable model (Waxman-Smits, dual water, SGS) it is possible to determine the intrinsic formation factor and porosity exponent, and the cation-exchange capacity.