borehole televiewer

1. n. [Formation Evaluation]
An ultrasonic logging device with a radially mounted rotating transducer that is used to scan the borehole wall. The transducer (in transmit mode) emits a high-frequency pulse that is reflected by the borehole wall back to the transducer (in receive mode). In openhole applications, it can be used to measure the borehole diameter (by measuring the acoustic transit time between transducer and borehole wall) and the amplitude of acoustic signals reflected by the borehole wall. The transducer is rotated to produce a cross section of the borehole size and images of the borehole wall. These are used to identify fractures, breakouts and other borehole features. In cased hole, they are used to identify internal corrosion.