| 摘要 |
Rock detritus created by a drag bit cutter shearing subterranean formation material may flow under a cutter and attach itself to a side surface of a cutter barrel by differential pressure-induced sticking, and dilate. This attached material, confined by hydrostatic pressure, can create and strengthen a barrier between the cutter and virgin rock being cut. The detritus barrier absorbs bit weight and reduces cutter efficiency by impairing contact of the cutter with the virgin rock formation. Increasing friction between the rock detritus and the side surface of the cutter barrel inhibits detritus flow, reduces build up, and allows hydrostatic pressure to contribute to, rather than inhibit, the cutting process. Similar beneficial results may be obtained when hydrostatic pressure drilling fluid is permitted to communicate through holes in the side surface of the cutter, or through an otherwise permeable side surface alleviating detritus sticking due to differential pressure effects.
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