| 摘要 |
Directional drilling apparatus (26) for location on a drill string (20) comprises a stabiliser (32) having a mandrel (38) for connection to the drill string (20) and an eccentric non-rotating element (46) mounted on the mandrel (38) for offsetting the string (20) in the bore (22) and a non-rotating offset mass (34) for maintaining the element (46) at a selected orientation relative to the bore (22) as the drill string (20) rotates.
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