| 摘要 |
<p>A borehole surveying method for drilling substantially horizontal crossings under barriers such as rivers, highways, buildings, airstrips etc., comprises a sensor, or sonde, 120 located on the end of the drill string just behind the drill bit. The sensor includes a gyroscope 136 and two accelerometers 138, 140. The gyro has a spin axis aligned with the instrument axis and two further sensitive axes orthogonally related to the spin axis and to each other. The accelerometers have sensitive axes aligned orthogonally to each other. The gyro data and accelerometer data are returned to the surface via a wireline cable 114 and are converted into a plot of the well borehole river crossing.</p> |
