The Hanai‐Bruggeman equation is applied to a model of a conductive rock matrix immersed in water. The result is a general two‐component equation which relates the electrical properties of a formation to the electrical properties of the rock matrix and the water at any frequency. The low‐frequency limit is compared with previous theoretical and experimental work on sand formations. From a comparison of the three‐resistor model of Wyllie and Southwick, the Waxman‐Smits model, the dual water model of Clavier et al (1977) and the proposed model, it is found that the only representation which is viable, conceptually sound, and in agreement with experiment, is the last one.