| 摘要 |
<p>Measurement of the caliper of a borehole, and/or of the standoff of a drilling tool from the walls of a borehole, during a drilling operation is made using an apparatus which includes three or more sensors (48), such as acoustic transducers, arranged circumferentially around a downhole tool (30) or drill collar. The transducers transmit ultrasonic signals to the borehole wall through the drilling fluid surrounding the drillstring and receive reflected signals back from the wall. Travel times for these signals are used to calculate standoff data for each transducer. The standoff measurements may be used to calculate the caliper of the borehole, the eccentricity of the tool in the borehole, and the angle of eccentricity with respect to the transducer position. The eccentricity and angle computations may be used to detect unusual movements of the drillstring in the borehole, such as sticking. banging, and whirling. <IMAGE></p> |
