Abstract: A method and device are disclosed for determining the impedance of the cement bond between a borehole casing and its wellbore. The invention uses a predicted resonance response as a baseline for determining from the observed resonance response the approximate impedance of the cement. Corrections are made to account for various defects in the casing by normalizing the received resonance response.

Abstract: A borehole televiewer system is disclosed which includes a sonde adapted to be suspended in a borehole containing borehole fluids. A variable speed brushless DC motor within the sonde is utilized to drive a rotatable mount at selected speeds in order to maintain a rotational speed in proportion to the linear speed of the sonde through the borehole. A "quick-disconnect" transducer head, including diametrically opposed acoustic transducers, is mounted to the rotatable mount in direct contact with the borehole fluids and is utilized to repetitively transmit energy pulses at the wall of the borehole throughout each rotation. Receiver circuitry is then utilized to determine the amplitude and transit time for each reflected pulse in order to determine parameters of interest for the borehole wall. In a preferred mode of the present invention, the reflected pulses are then utilized to generate a video representation of the borehole wall in addition to providing a graphic plot.