| 摘要 |
A drilling apparatus 100 includes a tubular body including an upper connection and a lower connection with a drill bit 120 disposed thereon, wherein the upper connection is configured to attach to a drillstring. Primary cutter blocks 130 are coupled to the tubular body and configured to selectively expand radially therefrom. The drilling apparatus further includes backup cutter blocks 132 coupled to the tubular body and configured to selectively expand radially therefrom. An activation system is configured to selectively expand and collapse the primary 130 and backup cutter blocks 132 in response to changes in weight applied to the primary and backup cutter blocks. The activation system may be hydraulic. |
