| 摘要 |
A bottom hole assembly has a drill bit and an under-reamer on the up-hole side of the drill bit. In one aspect, the assembly further has a compliant element linking the drill bit to the under-reamer, the compliant element allowing displacement of the drill bit relative to the under-reamer in the axial direction of the assembly. In another aspect, the assembly further has a sensor element which is arranged to measure the weight-on-bit and/or the applied torque of the drill bit, and a transmitter for transmitting the weight-on-bit and/or applied torque measurements to the surface.
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