| 摘要 |
<p>An injection sub for use with a string of dual concentric drill pipe, having inner and outer tubular members concentrically arranged to mate with the inner and outer pipes of the drill string to provide continuous isolated annular and central passageways, is particularly characterized by an annular chamber in the inner member. Ports permit the flow of fluid from the annular passageway to the chamber, and apertures permit fluid flow from the chamber to the central passageway. An annular check valve in the chamber cooperates with the ports to prevent flow from the chamber to the annular passageway.</p> |
