| 摘要 |
<p>A landing sub for a wiper, the wiper being adapted for internal removal of drilling mud from a drill string during its pull-out from a borehole, wherein the landing sub is mountable in the drill string, the landing sub comprises a longitudinal bore for through-flow of drilling mud and a landing seat for receiving the lower end of the wiper during pumping of drilling mud through the drill string, and the landing seat is equipped with at least one duct or passage for through-flow of drilling mud past the lower end of the wiper during continued pumping of drilling mud in the drill string.</p> |
