| 摘要 |
A downhole tool 10 in a drill string 1 1 for mitigating hazards of a blockage in an annul us of the drill string 1 1. The downhole tool 10 can sense biockages and selectively recirculate flow from within the annulus back to surface. Further, the downhole tool 10 is made up of segments 14, 16 that are selectively detachable from one another, so that the segments above the point of detachment are removable from a wellbore 98. A bypass sub 22 recirculates flow and includes a sleeve 44 with openings 52 in its side; when the annulus reaches a set pressure, the sleeve 44 slides to a position so the openings 52 register with ports 52 formed through a side wall 26 of the sub 22 to allow bypass flow. A processor 74 in the downhole tool 10 senses movement of the string 11, and when the string 1 1 is axially stationary more than a designated period of time, the processor 74 emits signals to detach the segments. |
