Determining the caliber of a borehole

摘要

To measure the caliber of a borehole while drilling, a borehole compensated downhole measuring apparatus (30) comprises a transmitter (32) which generates a signal which is received after passing directly and through the surrounding rock to at least one spaced receiver (34,36). The time/phase of the received signal relative to the transmitted signal is indicative of the borehole caliber. ……