| 摘要 |
Methods and apparatus for downhole operations, such as under-reaming. An under-reaming tool (210, 310)comprises a body (214, 314) and a plurality of extendable cutters(372)mounted on the body(214, 314). The under-reaming tool (210, 310)is configured to be cycled between a first configuration in which the cutters (372)are retracted and a second configuration in which the cutters (372)are movable between retracted and extended positions. The under-reaming tool (210, 310)is configured to prevent extension of the cutters (372)by an external fluid in the first and/or second configuration/s. |
