Dielectric well logging system and method with error correction

Abstract

A dielectric well logging system includes a logging tool adapted to be passed through a borehole traversing an earth formation. The logging tool includes a transmitter which induces electric energy into the earth formation at a radio frequency. Two receivers in the logging tool spaced a predetermined distance apart provides intermediate frequency signals corresponding to the electrical energy received from the earth formation. The intermediate frequency signals are transmitted by way of a cable to the surface. Surface electronics include zero crossing detectors, each detector receives a different intermediate frequency signal from the cable and provides a detector signal whose change in amplitude is representative of the intermediate frequency signal passing through zero. A source provides clock pulses at a frequency substantially greater than the frequency of the intermediate frequency signals. A logic circuit receiving the detector signals and the clock pulses provides groups of clock pulses in accordance with the detector signals. The number of clock pulses in each group corresponds to the dielectric constant of the earth formation.