Abstract: A rotary drag bit includes a primary cutter row comprising at least one primary cutter mounted on a blade, at least some cutters in the primary cutter row having a portion of a cutting surface thereof covered by a portion of the blade. A backup cutter row comprising at least one cutter may also be included, and at least a portion of a cutting surface of at least some cutters in the backup cutter row is covered by a portion of the blade. Enhanced support for cutters is provided against impact loading.

Abstract: A rotary drag bit includes a primary cutter row comprising at least one primary cutter and a multiple backup cutter group. The multiple backup cutter group comprises a first and second trailing cutter row, 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 groups 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.

Abstract: A rotary drag bit includes a primary cutter row comprising at least one primary cutter, and at least two additional cutters configured relative to one another. In one embodiment, the cutters are backup cutters of a backup cutter group located in respective first and second trailing cutter rows, oriented relative to one another, and positioned to substantially follow the at least one primary cutter. The rotary drag bit life is extended by the backup cutter group, making the bit more durable and extending the life of the cutters. In other of the embodiments, the cutters are configured to selectively engage a subterranean formation material being drilled, providing improved bit life and reduced stress upon the cutters. Still other embodiments of rotary drag bits include backup cutter configurations having different backrake angles and siderake angles, including methods therefor.

Abstract: Earth-boring tools comprise a body including a face at a leading end thereof and a shank at a trailing end. At least one primary blade may extend radially outward over the face and may comprise a plurality of cutting elements disposed thereon. At least one secondary blade may also extend radially outward over a portion of the face and the at least one secondary blade may comprise a plurality of cutting elements disposed thereon only over at least a portion of an area of greatest work rate per cutting element. Methods of forming earth-boring tools and methods of designing earth-boring tools are also disclosed.

Abstract: Nozzles for a drilling tools, such as rotary-type drag bits and roller cone bits, a drilling tool and drilling assembly comprising nozzles, and methods of conveying drilling fluid through a nozzle for use in drilling subterranean formations are provided. A nozzle may include a substantially cylindrical nozzle body having an axis and an inlet port with a primary passage extending therethrough, and at least one secondary passage that diverges from the primary passage at an exit port.

Abstract: A rotary drag bit includes a primary cutter row comprising at least one primary cutter, and at least two additional cutters configured relative to one another. In one embodiment, the cutters are backup cutters of a cutter group located in respective first and second trailing cutter rows, oriented relative to one another, and positioned to substantially follow the at least one primary cutter. The rotary drag bit life is extended by the backup cutter group, making the bit more durable and extending the life of the cutters. In other of the embodiments, the cutters are configured to selectively engage a subterranean formation material being drilled, providing improved bit life and reduced stress upon the cutters. Still other embodiments of rotary drag bits include backup cutter configurations having different backrake angles and siderake angles, including methods therefor.

Abstract: A rotary drag bit includes a primary cutter row comprising at least one primary cutter and a multiple backup cutter group. The multiple backup cutter group comprises a first and second trailing cutter row, 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 groups 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.

Abstract: A rotary drag bit exhibiting enhanced cutting efficiency and extended life is provided. The rotary drag bit comprises a bit body having a face surface, and a plurality of cutters coupled to the face surface of the bit body. The plurality of cutters comprises at least one pilot cutter and a rotationally trailing larger, primary cutter at substantially the same radius and, optionally of slightly less exposure. The pilot cutter is sized and positioned to pre-fracture the formation and perform an initial cut, while the primary cutter removes weakened, remaining formation material along the same rotational path. A method to pre-fracture subterranean formations using a rotary drag bit having a pilot cutter configuration is also provided.

Abstract: A method for evaluating existing drill bits and drill bit designs includes measuring several desired characteristics of a bit, including the wear experienced in drilling a formation, such as an actual formation or a simulated formation or a laboratory test fixture. A computer model may be used to evaluate the work-force and/or the sliding-wear rates that cutting elements of the bit experience as compared with the rate-of-penetration and/or durability of the bit. This information may be used to design a new drill bit, which may involve modification of the cutting elements (e.g., moving the location, volume (size and shape) or number of cutting elements from areas of the bit that receive lower work-force and sliding-wear rates to those areas that experience relatively greater work-force and sliding wear-rates. This may permit the cutting elements to be oriented more aggressively relative to a formation to be drilled.