| 摘要 |
<p>Apparatus designed to cause the drill bit attached to a drilling pipe string to bore in a pre-determined azimuthal direction comprises means responding to an azimuthal direction detector mounted in the pipe string for exercising a lateral force on the drill bit when the drilling moves away from the pre-determined direction. This causes the bit to drill in a new direction returning the pipe string to its correct direction. Another device is provided for causing the azimuthal direction detector to rotate at a speed relative to the pipe string approximately equal to that of the latter but in the opposite sense so that the detector is at rest relative to the borehole itself.</p> |
