ROTARY DRAG BIT

摘要

A rotary drag bit (110) includes a primary cutter row (143) comprising at least one primary" cutter (11) and a multiple backup cutter, group (153). The multiple backup cutter group comprises a first and second trailing cutter row (154, 155), each comprising at least one cutter positioned to follow the at least one primary cutter. The rotary drag bit life is extended by the multiple backup cutter group, making the bit more durable and extending the life of the cutters. Further, the cutters of the multiple backup cutter group are configured to selectively engage a subterranean formation material being drilled, providing improved bit life and reduced stress upon the cutters. Other embodiments of rotary drag bits are provided.