A study in induced polarization

Abstract Induced polarization in pyritic sandstone arises in part from overvoltage effects and in part from electrolytic polarization. Because induced-polarization measurements are commonly used to search for sulfides, the electrolytic polarization is an undesirable background effect. Pyrite in sandstone can be located only when overvoltage polarization substantially exceeds electrolytic polarization. Laboratory measurements indicate this is true only if there is ten percent or more pyrite in a rock. However, overvoltage polarization is much larger when low current densities are used, particularly if the matrix resistivity is high. Field measurements indicate that at low current densities as little as one or two percent pyrite may provide sufficient overvoltage polarization to be recognizable in the presence of electrolytic polarization.