| 摘要 |
A method of drilling a borehole into a subsurface earth formation, using a tubular drill string which includes at its lower end a bottom hole assembly comprising a drill bit, a drill steering system, and a surveying system, wherein the drill string includes a passageway for an auxiliary tool from a first position interior of the drill string above the bottom hole assembly t o a second position wherein at least part of the auxiliary tool is exterior of the drill string below the bottom hole assembly, which passageway can be selectively closed, and which method comprises drilling so as to progress th e drill string into the earth formation, until a tool operating condition is met; opening the passageway; passing an auxiliary tool from the first positi on through the passageway to the second position, and operating the auxiliary tool at the second position.
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