| 摘要 |
<p>Drilling pipe for making of a drill string, in particular for deviation drilling, comprising an outer tube (1) and an inner tube (2) connected to heads (4, 5) on each end, in such a manner that the inner tube communicates with apertures through each head, and in such a manner that a closed cavity is constituted between the tubes (1, 2), said cavity contributing to give the drilling pipe and the drill string a buoyancy in the bore hole.</p> |
