1. n. [Formation Evaluation]
The ability of a formation to resist electrical conduction, as derived from the reduction in amplitude of the electromagnetic wave generated in a propagation resistivity measurement. At the frequencies used and within the range of measurement, the attenuation depends almost solely on the resistivity, so that the former can be transformed to the latter with a simple algorithm. The transform also depends on transmitter/receiver spacings and tool design. For a 2-MHz measurement, a typical measurement range is 0.2 to 50 ohm.m. Above 50 ohm.m, the dependence of attenuation on resistivity is too small to measure accurately.