| 摘要 |
<p>A drilling apparatus for drilling a deviated bore, comprises a tubular outer member (12) having an offset and adapted for rotatably supporting a drill bit (24). The member has a gripping arrangement (20) for selectively engaging the wall of a bore to restrain the member against rotation. An inner member (32) is provided within the outer member for coupling to the drill bit at one end and to a drill string at another end. The apparatus has a first configuration in which the gripping arrangement is retracted and the inner member is coupled to the outer member such that rotation of the drill string provides for corresponding rotation of the inner and outer members, and a second configuration in which the gripping arrangement is extended and the inner member is rotatable relative to the outer member such that the outer member is restrained from rotation in the bore and rotation of the drill string provides for corresponding rotation of the inner member and the drill bit.</p> |
