Method and apparatus for creating an image of an earth borehole or a

Abstract

An acoustic logging tool, useful for creating a circumferential image of an earth borehole or well casing, which includes one or many acoustic transceivers mounted in substantially the same plane, in a drill string sub. The mounting receptacles are located in blocks, flexibly mounted in fixed inserts within the interior of the drill string sub. Each of the transceivers is structured to provide temperature and pressure compensation. The echo signals received by the transceivers are digitized and processed to eliminate extraneous noise created by the ringing of the transducers, by the signals reflected from the material backing the transducer ultrasonic element, and by any other sources inherent to the drilling environment. Digitization and further processing also allows for signal enhancement, thus allowing detection of signals in the presence of substantial noise. Temperature and pressure determinations are used to correct the acoustic velocity of the waves passing through the drilling fluid, 'on-the-fly', as the drilling process continues.