| 摘要 |
A drilling apparatus includes a tubular body including an upper connection and a lower connection with a drill bit disposed thereon, and an axial borehole therethrough, wherein the upper connection is configured to attach to a drillstring, primary cutter blocks coupled to the tubular body and configured to selectively expand radially therefrom. The drilling apparatus further includes backup cutter blocks coupled to the tubular body and configured to selectively expand radially therefrom, and an activation system configured to selectively expand and collapse the primary and backup cutter blocks in response to changes in weight applied to the primary and backup cutter blocks. |
