| 摘要 |
<p>A tool (10) is provided for use in retrieving a drill string from a bore. The tool includes a body (12) which, in use, is suspended from a travelling block. A fluid inlet (16) communicates via a passage (18) with an outlet (20) in communication with a drill string (11). A coupling (22) is provided for selectively engaging the drill string (11). A one-way valve (26) is located in the passage (18) in order to regulate fluid flow through the passage (18). When fluid flow is interrupted, the normally closed valve (26) maintains fluid pressure on the coupling (22), so retaining the coupling (22) on the drill string (11).</p> |
