| 摘要 |
A coring device includes a primary and a secondary bit that drill a first and second depth into a formation, respectively. The first and second bits are positioned on telescopically arranged mandrels that are rotated by a suitable rotary drive. The coring tool also includes a drive device that extends the first bit and the second bit a first depth into the formation and extends only the second bit a second depth into the formation. In arrangements, the actuating device can include a first hydraulic actuator applying pressure to extend the second bit into the formation and a second hydraulic actuator applying pressure to retract the second bit from the formation. The advancement and retraction of the first and second bits can be controlled by a control unit that uses sensor signals, timers, preprogrammed instruction and any other suitable arrangement.
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