Claims
- 1. A rotary drag bit for drilling a subterranean formation, comprising:
a bit body having a longitudinal axis and extending radially outward therefrom to a gage, the bit body further comprising at least a first region, a second region, and a third region radially intermediate the first and second regions extending over a face of the bit body to be oriented toward the subterranean formation during drilling; and a plurality of cutters located on the bit body in the first, second, and third regions, the cutters each comprising a superabrasive cutting face of a preselected geometry and including a preselected effective cutting face backrake angle with respect to a line generally perpendicular to the formation, as taken in the direction of intended bit rotation, and wherein the respective cutting faces of a majority of cutters located in the first region exhibit substantially more negative effective cutting face backrake angles than the effective cutting face backrake angles of the respective cutting faces of a majority of cutters located in the second and third regions.
- 2. The rotary drag bit of claim 1, wherein the first region lies within a cone of the face of the bit body, the second region extends over at least a flank on the face of the bit body, and the third region extends over at least a nose of the face of the bit body.
- 3. The rotary drag bit of claim 2, wherein the second region extends to the gage of the bit body.
- 4. The rotary drag bit of claim 1, wherein at least some of the superabrasive cutting faces are disposed on polycrystalline diamond compact tables.
- 5. The rotary drag bit of claim 4, wherein at least some of the polycrystalline diamond compact tables are supported by metallic substrates.
- 6. The rotary drag bit of claim 5, wherein at least some of the polycrystalline diamond compact tables are supported by tungsten carbide substrates.
- 7. The rotary drag bit of claim 1, wherein at least some of the plurality of cutters include cutting faces generally perpendicular to a longitudinal axis of the at least some of the plurality of cutters.
- 8. The rotary drag bit of claim 2, wherein at least about half of the plurality of cutters located in the first region exhibit an effective cutting face backrake angle within a range of approximately negative 10° to approximately negative 45°, at least about half of the plurality of cutters located in the second region exhibit an effective cutting face backrake angle not more negative than approximately negative 15°, and at least about half of the plurality of cutters located in the third region exhibit an effective cutting face backrake angle within a range of approximately negative 5° to approximately negative 30°.
- 9. The rotary drag bit of claim 2, wherein at least about one half of the plurality of the cutters located in the first region exhibit an effective cutting face backrake angle within a range of approximately negative 15° to approximately negative 30°, at least about half of the plurality of the cutters located in the second region exhibit an effective cutting face backrake angle not more negative than approximately negative 10°, and at least about half of the plurality of the cutters located in the third region exhibit an effective cutting face backrake angle within a range of approximately negative 10° to approximately negative 20°.
- 10. The rotary drag bit of claim 2, wherein at least about half of the plurality of cutters located in the first region exhibit an effective cutting face backrake angle of approximately negative 30°.
- 11. The rotary drag bit of claim 2, wherein at least about half of the plurality of cutters located in the second region exhibit an effective cutting face backrake angle of approximately negative 10°.
- 12. The rotary drag bit of claim 2, wherein the plurality of cutters located in the second region exhibit an effective cutting face backrake angle not more negative than approximately negative 15°.
- 13. The rotary drag bit of claim 2, wherein at least about half of the plurality of cutters located in the third region exhibit an effective cutting face backrake angle of approximately negative 20°.
- 14. The rotary drag bit of claim 2, wherein at least about half of the plurality of cutters located in the first region exhibit an effective cutting face backrake angle of approximately negative 30°, at least about half of the plurality of cutters located in the second region exhibit an effective cutting face backrake angle of approximately negative 10°, and at least about half of the plurality of cutters located in the third region exhibit an effective cutting face backrake angle of approximately negative 20°.
- 15. The rotary drag bit of claim 2, wherein at least about half of the plurality of cutters located in the second region exhibit an effective cutting face backrake angle of approximately negative 15°.
- 16. The rotary drag bit of claim 2, wherein at least about half of the plurality of cutters located in the first region exhibit an effective cutting face backrake angle of approximately negative 20°.
- 17. The rotary drag bit of claim 2, wherein approximately at least about half of the plurality of cutters located in the third region exhibit an effective cutting face backrake angle of approximately negative 10°.
- 18. The rotary drag bit of claim 2, wherein the respective cutting faces of a majority of cutters located in the second region exhibit less negative effective cutting face backrake angles than the effective cutting face backrake angles of the respective cutting faces of a majority of cutters located in the third region.
- 19. The rotary drag bit of claim 18, wherein at least about half of the plurality of cutters located in the first region exhibit an effective cutting face backrake angle of approximately negative 20°, at least about half of the plurality of cutters located in the second region exhibit an effective cutting face backrake angle of approximately negative 15°, and at least about half of the plurality of cutters located in the third region exhibit an effective cutting face backrake angle of approximately negative 10°.
- 20. The rotary drag bit of claim 2, wherein the first region comprises a plurality of cutters having chamfers, the second region comprises a plurality of cutters having chamfers, and the third region comprises a plurality of cutters having chamfers wherein the plurality of first region cutters include chamfers oriented at negative chamfer backrake angles more negative than chamfer backrake angles of the chamfers of the plurality of second and third region cutters having chamfers.
- 21. The rotary drag bit of claim 20, wherein the bit body further includes a plurality of generally radially oriented blades extending generally longitudinally over the bit face toward the gage, and wherein the first region cutters, the second region cutters, and the third region cutters are located on the blades.
- 22. The rotary drag bit of claim 20, wherein the effective cutting face backrake angles of the plurality of cutters are determined at least in part by cutter backrake angles of the cutters.
- 23. The rotary drag bit of claim 20, wherein at least one first region cutter, at least one second region cutter, and at least one third region cutter each include a chamfer having a preselected chamfer backrake angle at a cutting face periphery, and wherein the chamfer backrake angles of at least one first region cutter, the at least one second cutter region, and at least one third region cutter are mutually different.
- 24. The rotary drag bit of claim 20, wherein each of the plurality of cutters include a respective longitudinal axis, and the chamfers of the first region cutters having chamfers, the second region cutters having chamfers, and the third region cutters having chamfers are disposed at substantially equal angles to their respective longitudinal axes.
- 25. The rotary drag bit of claim 24, wherein the chamfers of the first, second, and third region cutters having chamfers are disposed at approximately 45° with respect to their respective longitudinal axes.
- 26. The rotary drag bit of claim 20, wherein at least some of the cutters of the first region having chamfers exhibit chamfer widths substantially larger than at least some of the chamfers of the cutters in the second region having chamfers.
- 27. The rotary drag bit of claim 26, wherein at least some of the cutters of the third region having chamfers exhibit chamfer widths intermediate chamfer widths of at least some of the cutters in the first and second regions having chamfers.
- 28. The rotary drag bit of claim 26, wherein at least some of the cutters of the first region having chamfers exhibit chamfer widths within a range of approximately 0.030 of an inch to approximately 0.060 of an inch.
- 29. The rotary drag bit of claim 26, wherein at least some of the cutters of the second region having chamfers exhibit chamfer widths within a range of approximately 0.005 of an inch to approximately 0.020 of an inch.
- 30. The rotary drag bit of claim 28, wherein at least some of the cutters of the second region having chamfers exhibit chamfer widths within a range of approximately 0.005 of an inch to approximately 0.020 of an inch.
- 31. A rotary drag bit for drilling a subterranean formation, comprising:
a bit body having a longitudinal axis and extending radially outward therefrom to a gage, the bit body further comprising a first region radially proximate the longitudinal axis, a second region radially proximate the gage, and third region radially intermediate the first and second regions, and a plurality of circumferentially spaced blade structures wherein at least some of the plurality of blade structures extend longitudinally along the face of the bit from generally the first region through the third region to generally the second region; a plurality of cutters having preselected cutter backrake angles carried by at least some of the plurality of blade structures and being positioned within each of the three regions of the bit body, the plurality of cutters each comprising a longitudinal axis and at least one primary superabrasive cutting face having a preselected size and geometry and being positioned substantially transverse to a direction of cutter movement during drilling; and wherein a plurality of the cutters located in the first region are oriented within a first range of relatively more aggressive cutter backrake angles, a plurality of the cutters located in the second region are oriented within a second range of relatively less aggressive cutter back rake angles, and a plurality of the cutters located in the third region are oriented within a third range of relatively intermediately aggressive cutter back rake angles.
- 32. The rotary drag bit of claim 31, wherein the first range of cutter backrake angles includes cutters having a backrake from approximately negative 5° to approximately negative 15°, the second range of cutter backrake angles includes cutters having a backrake not more negative than approximately a negative 45°, and the third range of cutter backrake angles includes cutters having a backrake from approximately negative 10° to approximately negative 30°.
- 33. The rotary drag bit of claim 31, wherein the first range of cutter backrake angles includes cutters having a backrake from approximately negative 5° to approximately negative 15°, the second range of cutter backrake angles includes cutters having a backrake not more negative than approximately a negative 30°, and the third range of cutter backrake angles includes cutters having a backrake from approximately negative 10° to approximately negative 20°.
- 34. The rotary drag bit of claim 31, wherein a majority of the cutters located in the first region have a cutter backrake angle of approximately negative 7°, a majority of the cutters located in the second region have a cutter backrake angle of approximately negative 15°, and a majority of the cutters located in the third region have a cutter backrake angle of approximately negative 10°.
- 35. The rotary drag bit of claim 31, wherein a majority of the cutters located in the first region have a cutter backrake angle of approximately negative 10°, a majority of the cutters located in the second region have a cutter backrake angle of approximately negative 20°, and a majority of the cutters located in the third region have a cutter backrake angle of approximately negative 15°.
- 36. The rotary drag bit of claim 31, wherein the superabrasive cutting faces are disposed on polycrystalline diamond compact tables.
- 37. The rotary drag bit of claim 36, wherein the polycrystalline diamond compact tables are supported by metallic substrates.
- 38. The rotary drag bit of claim 37, wherein the metallic substrates comprise tungsten carbide.
- 39. The rotary drag bit of claim 31, wherein at least some of the plurality of cutters exhibit superabrasive cutting faces having at least a substantial portion thereof generally perpendicular to the longitudinal axis of the at least some of the plurality of cutters.
- 40. The rotary drag bit of claim 31, wherein the first region comprises a plurality of cutters having chamfers, the second region comprises a plurality of cutters having chamfers, and the third region comprises a plurality of cutters having chamfers wherein the plurality of first region cutters having chamfers include chamfers oriented at negative chamfer backrake angles less negative than chamfer backrake angles of the chamfers of the plurality of second and third region cutters having chamfers.
- 41. The rotary drag bit of claim 40, wherein at least some of the superabrasive cutting faces exhibiting chamfers exhibit at least one of differing chamfer widths and differing chamfer angles in relation to the region in which the cutting faces exhibiting chamfers are located.
- 42. The rotary drag bit of claim 40, wherein the bit body further includes a plurality of generally radially oriented blades extending generally longitudinally over the bit face toward the gage, and wherein the first region cutters, the second region cutters, and the third region cutters are located on the blades.
- 43. The rotary drag bit of claim 40, wherein effective cutting face backrake angles of the plurality of cutters are determined at least in part by cutter backrake angles of the cutters.
- 44. The rotary drag bit of claim 40, wherein at least one first region cutter, at least one second region cutter, and at least one third region cutter each include a chamfer having a preselected chamfer backrake angle at a cutting face periphery, and wherein the chamfer backrake angles of at least one first region cutter, the at least one second cutter region, and at least one third region cutter are mutually different.
- 45. The rotary drag bit of claim 40, wherein each of the plurality of cutters include a respective longitudinal axis, and the chamfers of the first region cutters having chamfers, the second region cutters having chamfers, and the third region cutters having chamfers are disposed at substantially equal angles to their respective longitudinal axes.
- 46. The rotary drag bit of claim 45, wherein the chamfers of the first, second, and third region cutters having chamfers are disposed at approximately 45° with respect to their respective longitudinal axes.
- 47. The rotary drag bit of claim 40, wherein at least some of the cutters of the first region having chamfers exhibit chamfer widths substantially smaller than at least some of the chamfers of the cutters in the second region having chamfers.
- 48. The rotary drag bit of claim 47, wherein at least some of the cutters of the third region having chamfers exhibit chamfer widths intermediate chamfer widths of at least some of the cutters in the first and second regions having chamfers.
- 49. The rotary drag bit of claim 47, wherein at least some of the cutters of the first region having chamfers exhibit chamfer widths within a range of approximately 0.005 of an inch to approximately 0.020 of an inch.
- 50. The rotary drag bit of claim 47, wherein at least some of the cutters of the second region having chamfers exhibit chamfer widths within a range of approximately 0.030 of an inch to approximately 0.060 of an inch.
- 51. The rotary drag bit of claim 49, wherein at least some of the cutters of the second region having chamfers exhibit chamfer widths within a range of approximately 0.030 of an inch to approximately 0.060 of an inch.
- 52. A method of drilling a subterranean formation comprising:
providing a rotary drag bit comprising:
a bit body having a longitudinal axis and extending radially outwardly therefrom to a gage, the bit body configured to comprise at least a first region radially proximate the longitudinal axis, a second region radially proximate the gage, and a third region radially intermediate the first and second regions; a plurality of cutters located on the bit body in the first, second, and third regions, the cutters each comprising a superabrasive cutting face having preselected geometry and exhibiting a preselected effective cutting face backrake angle with respect to a line generally perpendicular to the formation, as taken in a direction of intended bit rotation, wherein the respective cutting faces of a majority of the cutters located in the first region exhibit effective cutting face angles which are substantially less aggressive than the effective cutting face backrake angles of the respective cutting faces of a majority of cutters located in the second and third regions; orienting a face of the bit body toward a subterranean formation; rotating the bit body at a selected rotational speed while applying a weight upon the rotary drag bit; and engaging the subterranean formation with cutters located on at least one of the first, second, and third regions of the bit body so as to penetrate the subterranean formation at a greater rate of penetration and at a lower torque-on-bit as compared to a rate-of-penetration and a torque-on-bit generated by a conventional rotary drag bit drilling the same subterranean formation at approximately the same rotational speed.
- 53. The method of claim 52, wherein providing a rotary drag bit further comprises configuring the bit body to comprise a plurality of blade structures, each of the blade structures extending generally longitudinally along the bit body from generally the first region through the third region and at least generally to the second region.
- 54. The method of claim 53, wherein configuring the bit body to comprise a plurality of blade structures further comprises configuring the blade structures to carry the plurality of cutters thereon.
- 55. The method of claim 54, wherein providing a rotary drag bit further comprises configuring the respective superabrasive cutting faces of the plurality of cutters to include a chamfer of a preselected width and to exhibit a chamfer angle with respect to a longitudinal axis of each of the plurality of cutters.
- 56. The method of claim 55, wherein providing a rotary drag bit further comprises providing a rotary drag bit comprising at least some of the plurality of cutters having superabrasive cutting faces comprising polycrystalline diamond compact tables being supported by tungsten carbide substrates.
- 57. The method of claim 52, wherein providing a rotary drag bit further comprises orienting a majority of the cutters located generally in the first region to have a backrake angle within a first range of cutter backrake angles, orienting a majority of the cutters generally located in the second region to have a cutter backrake angle within a second range of cutter backrake angles, and orienting a majority of the cutters generally located in the third region to have a cutter backrake angle within a third range of cutter backrake angles.
- 58. The method of claim 57, wherein orienting a majority of the cutters respectively located in the first, second, and third regions comprises orienting a majority of the cutters located in the first region to exhibit backrake angles ranging from about negative 10° to about negative 45°, orienting a majority of the cutters located in the second region to exhibit cutting face backrake angles not more negative than about negative 15°, and orienting a majority of the cutters located in the third region to exhibit cutting face backrake angles ranging from about negative 5° to about negative 30°.
- 59. The method of claim 57, wherein orienting a majority of the cutters respectively located in the first, second, and third regions comprises orienting a majority of the cutters located in the first region to exhibit cutting face backrake angles ranging from about negative 15° to about negative 30°, orienting a majority of the cutters located in the second region to exhibit cutting face backrake angles not more negative than about negative 20°, and orienting a majority of the cutters located in the third region to exhibit cutting face backrake angles ranging from about negative 10° to about negative 20°.
- 60. The method of claim 57, wherein orienting a majority of the cutters respectively located in the first, second, and third regions comprises orienting at least some of the majority of the cutters located in the first region to exhibit a cutting face backrake angle of approximately negative 30°, orienting at least some of the majority of the cutters located in the second region to exhibit a cutting face backrake angle of approximately negative 10°, and orienting at least some of the majority of the cutters located in the third region to exhibit a cutting face backrake angle of approximately negative 20°.
- 61. The method of claim 57, wherein orienting a majority of the cutters respectively located in the first, second, and third regions comprises orienting at least some of the majority of the cutters located in the first region to exhibit a cutting face backrake angle of approximately negative 20°, orienting at least some of the majority of the cutters located in the second region to exhibit a cutting face backrake angle of approximately negative 15°, and orienting at least some of the majority of the cutters located in the third region to exhibit a cutting face backrake angle of approximately negative 10°.
- 62. The method of claim 52, wherein providing a rotary drag bit comprising a plurality of cutters located thereon comprises selectively varying each of the preselected effective cutting face backrake angles of the cutters located on the bit body in the first, second, and third regions by selectively varying at least one of a cutter backrake angle, providing a cutting face having a preselected geometry comprising configuring the cutting face to include a chamfer of a preselected width and chamfer angle, and varying the respective cutting face angles in relation to the radial distance from the longitudinal axis in which the cutter bearing the respective cutting face is located.
- 63. A method of drilling a subterranean formation comprising:
providing a rotary drag bit comprising:
a bit body having a longitudinal axis and extending radially outwardly therefrom to a gage, the bit body configured to comprise at least a first region radially proximate the longitudinal axis, a second region radially proximate the gage, and a third region radially intermediate the first and second regions; a plurality of cutters located on the bit body in the first, second, and third regions, the cutters each comprising a superabrasive cutting face having preselected geometry and exhibiting a preselected effective cutting face backrake angle with respect to a line generally perpendicular to the formation, as taken in a direction of intended bit rotation, wherein the respective cutting faces of a plurality of the cutters located in the first region are on cutters oriented within a first range of relatively more aggressive cutter backrake angles, a plurality of the cutters located in the second region are on cutters oriented within a second range of relatively less aggressive cutter back rake angles, and a plurality of the cutters located in the third region are on cutters oriented within a third range of relatively intermediately aggressive cutter back rake angles. orienting a face of the bit body toward a subterranean formation; rotating the bit body at a selected rotational speed while applying a weight upon the rotary drag bit; and engaging the subterranean formation with at least one of the first, second, and third regions of the bit body so as to penetrate the subterranean formation at a greater rate of penetration and at a lower torque-on-bit as compared to a rate-of-penetration and a torque-on-bit generated by a conventional rotary drag bit drilling the same subterranean formation at approximately the same rotational speed.
- 64. The method of claim 63, wherein providing a rotary drag bit further comprises configuring the bit body to comprise a plurality of blade structures, each of the blade structures extending generally longitudinally along the bit body from generally the first region through the third region and at least generally to the second region.
- 65. The method of claim 64, wherein configuring the bit body to comprise a plurality of blade structures further comprises configuring the blade structures to carry the plurality of cutters thereon.
- 66. The method of claim 65, wherein providing a rotary drag bit further comprises configuring the respective superabrasive cutting faces of the plurality of cutters to include a chamfer of a preselected width and to exhibit a chamfer angle with respect to a longitudinal axis of each of the plurality of cutters.
- 67. The method of claim 66, wherein providing a rotary drag bit further comprises providing a rotary drag bit comprising at least some of the plurality of cutters having superabrasive cutting faces comprising polycrystalline diamond compact tables being supported by tungsten carbide substrates.
- 68. The method of claim 63, wherein providing a rotary drag bit further comprises orienting a majority of the cutters located generally in the first region to have a backrake angle within a first range of cutter backrake angles, orienting a majority of the cutters generally located in the second region to have a cutter backrake angle within a second range of cutter backrake angles, and orienting a majority of the cutters generally located in the third region to have a cutter backrake angle within a third range of cutter backrake angles.
- 69. The method of claim 68, wherein orienting a majority of the cutters respectively located in the first, second, and third regions comprises orienting a majority of the cutters located in the first region to exhibit backrake angles ranging from about negative 5° to about negative 15°, orienting a majority of the cutters located in the second region to exhibit cutting face backrake angles not less negative than about negative 10°, and orienting a majority of the cutters located in the third region to exhibit cutting face backrake angles ranging from about negative 10° to about negative 20°.
- 70. The method of claim 68, wherein orienting a majority of the cutters respectively located in the first, second, and third regions comprises orienting a majority of the cutters located in the first region to exhibit cutting face backrake angles ranging from about negative 5° to about negative 20°, orienting a majority of the cutters located in the second region to exhibit cutting face backrake angles not less negative than about negative 15°, and orienting a majority of the cutters located in the third region to exhibit cutting face backrake angles ranging from about negative 10° to about negative 30°.
- 71. The method of claim 68, wherein orienting a majority of the cutters respectively located in the first, second, and third regions comprises orienting at least some of the majority of the cutters located in the first region to exhibit a cutting face backrake angle of approximately negative 7°, orienting at least some of the majority of the cutters located in the second region to exhibit a cutting face backrake angle of approximately negative 15°, and orienting at least some of the majority of the cutters located in the third region to exhibit a cutting face backrake angle of approximately negative 10°.
- 72. The method of claim 68, wherein orienting a majority of the cutters respectively located in the first, second, and third regions comprises orienting at least some of the majority of the cutters located in the first region to exhibit a cutting face backrake angle of approximately negative 10°, orienting at least some of the majority of the cutters located in the second region to exhibit a cutting face backrake angle of approximately negative 20°, and orienting at least some of the majority of the cutters located in the third region to exhibit a cutting face backrake angle of approximately negative 15°.
- 73. The method of claim 63, wherein providing a rotary drag bit comprising a plurality of cutters located thereon comprises selectively varying each of the preselected effective cutting face backrake angles of the cutters located on the bit body in the first, second, and third regions by selectively varying at least one of a cutter backrake angle, providing a cutting face having a preselected geometry comprising configuring the cutting face to include a chamfer of a preselected width and chamfer angle, and varying the respective cutting face angles in relation to the radial distance from the longitudinal axis in which the cutter bearing the respective cutting face is located.
- 74. A rotary drag bit for drilling a subterranean formation, comprising:
a bit body having a longitudinal axis and extending radially outward therefrom to a gage, the bit body further comprising at least a first region, a second region, and a third region radially intermediate the first and second regions extending over a face of the bit body to be oriented toward the subterranean formation during drilling; and a plurality of cutters located on the bit body in the first, second, and third regions, the cutters each comprising a superabrasive cutting face of a preselected geometry and including a preselected effective cutting face backrake angle with respect to a line generally perpendicular to the formation, as taken in the direction of intended bit rotation, wherein at least one cutting geometry characteristic selected from the group consisting of cutter backrake angle, effective cutting face backrake angle, chamfer angle, chamfer width, and chamfer backrake angle of at least one first region cutter, the at least one second cutter region, and at least one third region cutter are mutually different and wherein the bit exhibits a lower torque-on-bit for a given rate-of-penetration as compared to a torque-on-bit generated by a conventional rotary drag bit drilling the same subterranean formation at approximately the same rotational speed.
- 75. The rotary drag bit of claim 74, wherein the rotary drag bit exhibits directional drilling behavior substantially equal to that of the conventional rotary drag bit.
- 76. The rotary drag bit of claim 74, wherein at least about half of the plurality of cutters located in the first region exhibit an effective cutting face backrake angle more negative than the cutters in a corresponding region of the conventional rotary drag bit, at least about half of the plurality of cutters located in the second region exhibit an effective cutting face backrake angle less negative than the cutters in a corresponding region of the conventional rotary drag bit, and at least about half of the plurality of cutters located in the third region exhibit an effective cutting face backrake angle less negative than the cutters in a corresponding region of the conventional rotary drag bit.
- 77. The rotary drag bit of claim 76, wherein the rotary drag bit exhibits directional drilling behavior substantially equal to that of the conventional rotary drag bit.
- 78. The rotary drag bit of claim 74, wherein at least about half of the plurality of cutters located in the first region exhibit a chamfer backrake angle more negative than the cutters in a corresponding region of the conventional rotary drag bit, at least about half of the plurality of cutters located in the second region exhibit a chamfer backrake angle less negative than the cutters in a corresponding region of the conventional rotary drag bit, and at least about half of the plurality of cutters located in the third region exhibit a chamfer backrake angle less negative than the cutters in a corresponding region of the conventional rotary drag bit.
- 79. The rotary drag bit of claim 78, wherein the rotary drag bit exhibits directional drilling behavior substantially equal to the conventional rotary drag bit.
- 80. The rotary drag bit of claim 74, wherein at least about half of the plurality of cutters located in the first, second, or third regions exhibit a smaller chamfer width than the cutters in a corresponding region of the conventional rotary drag bit and at least about half of the plurality of cutters located in the first, second, or third regions exhibit a chamfer backrake angle less negative than the cutters in a corresponding region of the conventional rotary drag bit.
- 81. The rotary drag bit of claim 80, wherein the rotary drag bit exhibits directional drilling behavior substantially equal to the conventional rotary drag bit.
- 82. The rotary drag bit of claim 74, wherein at least about half of the plurality of cutters located in the first region exhibit a larger chamfer width than the cutters in a corresponding region of the conventional rotary drag bit, at least about half of the plurality of cutters located in the second region exhibit a smaller chamfer width than the cutters in a corresponding region of the conventional rotary drag bit, and at least about half of the plurality of cutters located in the third region exhibit a smaller chamfer width than the cutters in a corresponding region of the conventional rotary drag bit.
- 83. The rotary drag bit of claim 82, wherein the rotary drag bit exhibits directional drilling behavior substantially equal to the conventional rotary drag bit.
- 84. A rotary drag bit for drilling a subterranean formation, comprising:
a bit body having a longitudinal axis and extending radially outward therefrom to a gage, the bit body further comprising a face to be oriented toward the subterranean formation during drilling; and a plurality of cutters located on the bit body over the face, the cutters each comprising a superabrasive cutting face of a preselected geometry and including a preselected effective cutting face backrake angle with respect to a line generally perpendicular to the formation, as taken in the direction of intended bit rotation, wherein at least one cutting geometry characteristic selected from the group consisting of cutter backrake angle, effective cutting face backrake angle, chamfer angle, chamfer width and chamfer backrake angle of at least some of the plurality of cutters are selected to enable the bit to exhibits a lower torque-on-bit for a given rate-of-penetration as compared to a torque-on-bit generated by a conventional rotary drag bit drilling the same subterranean formation at approximately the same rotational speed.
- 85. The rotary drag bit of claim 84, wherein the rotary drag bit exhibits directional drilling behavior substantially equal to that of the conventional rotary drag bit.
- 86. The rotary drag bit of claim 84, wherein at least some cutters of the plurality exhibit ever-greater aggressiveness in a progression extending substantially from cutter locations radially proximate the longitudinal axis to cutter locations radially more distant therefrom.
- 87. The rotary drag bit of claim 86, wherein the ever-greater aggressiveness is manifested through decreasing cutter backrake angle.
- 88. The rotary drag bit of claim 86, wherein the ever-greater aggressiveness is manifested through decreasing effective cutting face backrake angle.
- 89. The rotary drag bit of claim 86, wherein the ever-greater aggressiveness is manifested through decreasing chamfer angle.
- 90. The rotary drag bit of claim 86, wherein the ever-greater aggressiveness is manifested through decreasing chamfer width.
- 91. The rotary drag bit of claim 86, wherein the ever-greater aggressiveness is manifested through decreasing chamfer backrake angle.
- 92. A method of designing a rotary drag bit for drilling a subterranean formation, comprising:
selecting a configuration for a bit body having a longitudinal axis and extending radially outward therefrom to a gage, the bit body further comprising a face of the bit body to be oriented toward the subterranean formation during drilling and exhibiting a profile along which a plurality of cutters are to be placed; and selecting a plurality of cutters to be located on the bit body over the face and along the profile, the cutters of the plurality each comprising a superabrasive cutting face, the selecting further comprising selecting at least one cutting geometry characteristic for at least some of the cutters of the plurality from the group consisting of cutter backrake angle, effective cutting face backrake angle, chamfer angle, chamfer width and chamfer backrake angle to enable the bit to exhibit a lower torque-on-bit for a given rate-of-penetration as compared to a torque-on-bit generated by a conventional rotary drag bit drilling the same subterranean formation at approximately the same rotational speed.
- 93. The method of claim 92, further comprising selecting the at least one cutting geometery characteristic to enable the rotary drag bit to exhibit directional drilling behavior substantially equal to that of the conventional rotary drag bit.
- 94. The method of claim 92, further comprising selecting at least some cutters of the plurality to exhibit ever-greater aggressiveness in a progression extending substantially from cutter locations radially proximate the longitudinal axis to cutter locations radially more distant therefrom.
- 92. A method of altering a torque response of a rotary drag bit for drilling a subterranean formation, comprising:
selecting a configuration for a bit body having a longitudinal axis and extending radially outward therefrom to a gage, the bit body further comprising a face of the bit body to be oriented toward the subterranean formation during drilling and exhibiting a profile along which a plurality of cutters are to be placed; selecting a plurality of cutters to be located on the bit body over the face and along the profile, the cutters of the plurality each comprising a superabrasive cutting face, wherein each cutter of the plurality exhibits at least one cutting geometry characteristics selected from the group consisting of cutter backrake angle, effective cutting face backrake angle, chamfer angle, chamfer width and chamfer backrake angle; and modifying at least one cutting geometry characteristic of at least one cutter of the plurality.
- 93. The method of claim 92, wherein modifying at least one cutting geometry characteristic of at least one cutter of the plurality comprises altering at least one cutting geometry characteristic of some of the cutters of the plurality.
- 94. The method of claim 92, wherein modifying at least one cutting geometry characteristic of at least one cutter of the plurality comprises enabling the rotary drag bit to exhibit a lower torque-on-bit for a given rate-of-penetration as compared to a torque-on-bit generated by the rotary drag bit drilling at approximately the same rotational speed without the modification of the at least one cutting geometry characteristic of the at least one cutter of the plurality.
- 95. A method of altering a torque response of an existing rotary drag bit for drilling a subterranean formation, comprising:
providing an existing rotary drag bit including:
a bit body having a longitudinal axis and extending radially outward therefrom to a gage, the bit body further comprising a face of the bit body to be oriented toward the subterranean formation during drilling and exhibiting a profile along which a plurality of cutters are placed; and a plurality of cutters located on the bit body over the face and along the profile, the cutters of the plurality each comprising a superabrasive cutting face, wherein each cutter of the plurality exhibits at least one cutting geometry characteristics selected from the group consisting of cutter backrake angle, effective cutting face backrake angle, chamfer angle, chamfer width and chamfer backrake angle; and replacing at least one cutter of the plurality with another cutter exhibiting at least one different cutting geometry characteristic.
- 96. The method of claim 95, wherein replacing at least one cutter of the plurality comprises replacing at least some cutters of the plurality.
- 97. The method of claim 95, wherein replacing at least one cutter of the plurality with another cutter exhibiting at least one different cutting geometry characteristic comprises enabling the rotary drag bit to exhibit a lower torque-on-bit for a given rate-of-penetration as compared to a torque-on-bit generated by the rotary drag bit drilling at approximately the same rotational speed without the replacement of the at least one cutter of the plurality.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of copending U.S. patent application Ser. No. 09/854,765 filed May 14, 2001, which is a continuation of Ser. No. 08/925,525, filed Sep. 8, 1997, now issued U.S. Pat. No. 6,230,828, the disclosures of each of which are hereby incorporated herein by reference.
Continuations (1)
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Number |
Date |
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Parent |
08925525 |
Sep 1997 |
US |
Child |
09854765 |
May 2001 |
US |
Continuation in Parts (1)
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Number |
Date |
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Parent |
09854765 |
May 2001 |
US |
Child |
10233329 |
Aug 2002 |
US |