GB2403966A

GB2403966A - Cutting element arrangement for single roller cone bit

Info

Publication number: GB2403966A
Application number: GB0414707A
Authority: GB
Inventors: George Witman; Peter Wilson; Richard Butland; Dan Belnap; John Herman; Ronald Birne-Browne; Per Nese; Louis Loiselle
Original assignee: Smith International Inc
Current assignee: Smith International Inc
Priority date: 2003-07-01
Filing date: 2004-06-30
Publication date: 2005-01-19
Anticipated expiration: 2024-06-30
Also published as: US20050109543A1; CA2472730A1; GB2403966B; GB0414707D0

Abstract

A cutting element arrangement for a single roller cone bit 40 includes both at least one substantially non-planar cutting element 48 and at least one substantially planar cutting element 50. The substantially non-planar cutting element 48 is disposed on an inner row of inserts on the single roller cone and the substantially planar cutting element 50 is disposed on an outer row. With such an arrangement, the substantially non-planar cutting elements 48 effectively penetrate the formation while the substantially planar cutting elements 50 maintain the bore hole gage. The cutting elements are further defined with respect to their positional angle, their tip radius to extension ratio and their extension length from the surface of the roller cone.

Description

CUTTING ELEMENT ARRANGEMENT FOR SINGLE ROLLER

CONE BIT

CROSS-REFERENCE TO RELATED APPLICATIONS

00011 This application claims priority, pursuant to 35 U.S.C. ll9(e), of U.S. Provisional Patent Application No. 60/484,172 filed July 1, 2003. That Application is incorporated by reference in its entirety.

Background of Invention

Field ofthe lovention

00021 The invention relates generally to the field of roller cone ('Yock") bits used to drill wellbores through earth formations. More specifically, the invention is related to an anangement of cutting elements ("inserts") used in roller cone bits having a single roller cone.

Background Art

00031 Roller cone bits are one type of drill bit used to drill wellbores through earth formations. Roller cone bits include a bit body adapted to be coupled to a drilling tool assembly or "drill string" which rotates the bit as it is pressed axially into the formations being drilled. The bit body includes one or more legs, each having thereon a bearing journal. The most commonly used types of roller cone drill bits include three such legs and bearing journals. The roller cone is rotatably mounted to the bearing journal. During drilling, the roller cones rotate about the respective journals while the bit is rotated.

00041 The roller cones include a number of cutting elements (also referred to and known as "inserts" or "teeth"), which may be press fit cutting elements made from tungsten carbide and other materials, or may be milled steel teeth.

The cutting elements engage the formation in a combination of crushing, gouging, and scraping or shearing action that removes small segments of the connation being drilled.

00051 The cuffing elements on a cone of a three-cone bit are generally classified as inner-row cutting elements and gage-row cutting elements.

Inner row cuffing elements engage the bore hole bottom, but not the well bore wall. Gage-row cuffing elements engage the well bore wall and sometimes a small outer ring portion of the bore hole bottom. The direction of motion of cuffing elements engaging the rock on a two or three-cone bit is generally in one direction or a very small limited range of direction, i.e., 10 degrees or less.

00061 One particular type of roller cone drill bit includes only one leg, bearing journal, and roller cone rotatably attached thereto. The drilled hole and the longitudinal axis of this type of bit are generally concentric. This type of drill bit has generally been preferred for drilling applications when the diameter of the hole being drilled is small (e.g., less than about 4 to 6 inches [10 to 15 cm]) because the bearing structure can be larger relative to the diameter of the drilled hole when the bit only has one concentric roller cone. This is in contrast to the typical three-cone rock bit, in which each journal must be smaller relative to the drilled hole diameter.

00071 Similar to roller cones of a two-cone or three-cone rock bit, cutting elements are disposed around a surface of a single roller cone bit for penetrating into a formation. One type of cutting element that has been disposed around the surface of a roller cone is a substantially planar cutting element. Flat crested cutting elements are examples of substantially planar cutting elements. Figure 1 shows a flat crested cutting element 10.

Properties of the flat crested cutting element 10 include a relatively large surface area 12 for engaging a formation and sharp corners 14 for shearing action. Although substantially planar cutting elements 10 are effective in maintaining a gage of a bore hole, they are not effective in penetrating into hard formations.

00081 Another type of cutting element that has been disposed around the surface of a roller cone is a substantially non-planar cutting element (also referred to as "non-flat crested cutting elements',). Conical cutting elements and chisel cutting elements are examples of substantially non-planar cutting elements. Figure 2 shows a substantially non-planar cutting element 20.

Properties of the substantially non-planar cutting element 20 include a relatively more pointed surface area 22 for engaging a formation.

91 Such substantially non-planar cutting elements may be characterized, or otherwise defined, as having a particular tip radius to extension ratio. For example, Figure 3 shows how a conical cutting element 23 may be characterized in terms of a ratio of its tip radius 24 to its tip extension 26.

Similarly, Figures 4a and 4b, which show front and side views of a chisel insert 25, show how the chisel insert 25 may be characterized in terms of a ratio of its tip radius 27 to its tip extension 28. Those skilled in the art will understand that the tip radius to extension ratio of a particular cutting element allows for the characterization of the "aggressiveness" of the cutting element in a general manner.

Although substantially non-planar cutting elements 20 are effective in penetrating into hard formations, they wear quickly relative to substantially planar cutting elements 10 and are not effective in maintaining a gage of a bore hole.

00111 Accordingly, in situations in which the maintenance of bore hole gage is important, roller cones having all substantially planar cutting elements are used, and in situations in which penetration into hard formations is important, roller cones having all substantially non-planar cutting elements (including combinations of conical cutting elements and chisel cutting elements) are used.

Summary of Invention

00121 According to one aspect of one or more embodiments of the present invention, a roller cone drill bit comprises a bit body adapted to be coupled to a drill string, a bearing journal depending from the bit body, and a single roller cone rotatably attached to the bearing journal, where the single roller cone has a plurality of cuffing elements disposed at positions selected such that a majority of cuffing elements adapted to engage a bottom of a bore hole are substantially non-planar cutting elements and a majority of cutting elements adapted to engage a wall of the bore hole are substantially planar cutting elements.

00131 According to one aspect of one or more embodiments of the present invention, a roller cone drill bit comprises a bit body adapted to be coupled to a drill string, a bearing journal depending from the bit body, and a single roller cone rotatably attached to the bearing joumal, where the single roller cone has at least one inner row of cutting elements comprising at least one substantially non-planar cutting element and at least one outer row of cutting elements comprising at least one substantially planar cutting element.

00141 According to one aspect of one or more embodiments of the present invention, a roller cone drill bit comprises a bit body adapted to be coupled to a drill string, a bearing journal depending from the bit body, and a single roller cone rotatably attached to the bearing journal, where the single roller cone has at least one substantially planar cutting element and at least one substantially non-planar cutting element.

00151 Other aspects and advantages of the invention will be apparent from

the following description and the appended clauns.

Brief Descnption of Drawings 00161 Figure 1 shows a substantially planar cutting element.

00171 Figure 2 shows a substantially non-planar cutting element.

00181 Figure 3 shows a conical cutting element.

00191 Figure 4a shows a front view of a chisel cutting element.

00201 Figure 4b shows a side view of a chisel cutting element.

00211 Figure 5 shows a generalized cut away view of a single roller cone bit.

00221 Figure 6 shows a single roller cone bit in accordance with an embodiment of the present invention.

Detailed Description

0023l As discussed above, typical roller cones have either all substantially planar cutting elements or all substantially non-planar cutting elements depending on whether gage maintenance or formation penetration is more important. What is needed, however, especially with the use of a single roller cone bit, is a design that facilitates both gage maintenance and effective formation penetration.

00241 A general structure for a single roller cone bit which can be made according to various embodiments of the present invention is shown in cut away view in Figure 5. The bit includes a bit body 1 made of steel or other high strength material. The bit body 1 includes a coupling 4 at one end adapted to join the bit body 1 to a drill string (not shown) for rotating the bit dig drilling. The bit body 1 may include gage protection pads 2 at circumferentially spaced apart positions about the bit body 1. The gage protection pads 2 may include gage protection inserts 3 in some embodiments. The gage protection pads 2, if used, extend to a drill diameter 13 of the bit.

00251 The other end of the bit body 1 includes a bearing journal 1A to which a single, generally hemispherically shaped roller cone 6 is rotatably mounted.

In some embodiments, the cone 6 may be locked onto the journal 1A by locking balls 1B disposed in corresponding grooves on the outer surface of the journal 1A and the interior surface of the cone 6. The means by which the cone 6 is rotatably locked onto the journal 1A is not meant to limit the scope of the present invention. The cone 6 is formed from steel or other high strength material and may be covered about its exterior surface with a hardfacing or similar material intended to reduce abrasive wear of the cone 6.

In some embodiments, the cone 6 will include a seal 8 disposed to exclude fluid and debris from entering the space between the inside of the cone 6 and the journal 1A. Such seals are well known in the art.

00261 The cone 6 includes a plurality of cutting elements thereon at selected positions, which in various embodiments of the invention are cutting elements 5, 7 generally fit into corresponding sockets (not shown separately) in the outer surface of the cone 6.

00271 The journal 1A depends from the bit body I such that it defines an angle a between the rotational axis 9 of the journal 1A and the rotational axis 11 of the bit body 1. The size of this angle a will depend on factors such as the nature of the earth formations being drilled by the bit. Nonetheless, because the bit body 1 and the cone 6 rotate about different axes, the motion of the cutting elements 5, 7 during drilling can be roughly defined as falling within a wall contacting zone 10, in which the cutting elements 7 located therein at least intermittently contact the outer diameter (wall) of the wellbore, and a bottom contacting zone 12, in which the cutting elements 5 located therein are in substantially continuous contact with the earth formations, and generally do not contact the outer diameter (wall) of the wellbore during drilling. The cutting elements 7 in the wall contacting zone therefore define the drill diameter 13 of the bit.

0028] The cutting elements 5, 7 may be made from tungsten carbide, other metal carbide, or other hard materials known in the art for making drill bit cutting elements. The cutting elements 5, 7 may also be made from polycrystalline diamond, boron nitride, or other super hard material known in the art, or combinations of hard and super hard materials known in the art.

0029] Various embodiments of the present invention have a cutting element arrangement that uses substantially planar cutting elements having a range of motion falling within a bore hole wall contacting zone and substantially non planar cutting elements (e.g., conical and/or chisel cutting elements) having a range of motion falling within a bore hole bottom contacting zone.

10o3o] Figure 6 shows an exemplary single roller cone bit 40 in accordance with an embodiment of the present invention. As shown in Figure 6, an angular position of a cutting element of a single roller cone bit 40 may be defined as follows. A first angle 60 is defined as a journal angle from a horizontal plane 62. A second angle 64 is defined as the angle between an axis 66 of a single roller cone 54 and an axis of a cutting element. The sum of the first angle 60 and the second angle 64 can than be used to describe the angular position of a particular cutting element. Those skilled in the art will appreciate that the foregoing cutting elemant angular position description is applicable to describing an arrangement of cutting elanats in all three dimensions. other words, an angular position of a cutting elemant defined as the sum of the journal angle 60 from a horizontal plane 62 and an angle between an axis 66 of the single rolla cone 54 and an axis of a cutting elament applies to a three dimensional layout ofthe single rolla cone bit 40.

00311 With respect to the definition of cutting elemant angular position discussed above, substantially non-planar cutting elaments (e.g., conical and chisel cutting elements) 48 may be selected and disposed at an angle preferably anywhere substantially between O degrees and 120 degrees.

Substantially planar cutting elemants (e.g., flat crested cutting elements) 50 may be selected and disposed at an angle anywhere substantially between degrees and 175 degrees. Note that Figure 6 is not to scale with respect to the indications of the angle measurements.

2] Accordingly, a single rolla cone bit 40 is provided that has a cutting elament arrangement for penetrating into hard formations while maintaining a full gage of a bore hole. In this arrangement, the substantially non-planar cutting elements 48 are selected and positioned so as to support most of the weight of the single rolla cone bit 40. The shape of the substantially non planar cutting elements allows them to penetrate a hard formation effectively.

00331 The substantially planar cutting elements 50 are selected and positioned so as to maintain a substantially full gage of the bore hole. The shape of the substantially planar cutting elaments 50 provides greata carbide volume for increased wear resistance necessary to maintain bore hole gage.

Moreover, the sharp corners of the substantially planar cutting elements 50 allow the substantially planar cutting elemants 50 to cut with an efficient shearing action.

00341 In one or more embodiments of the present invention, a region for disposition or placement of the substantially planar cutting elements 50 may be at an angle anywhere substantially between about 125 degrees and about degrees.

00351 In one or more embodiments of the present invention, a region for disposition or placement of the substantially planar cuffing elements 50 may be at an angle anywhere substantially between about 135 degrees and about lSS degrees.

00361 In one or more embodiments of the present invention, a region for disposition or placement of the substantially planar cuffing elements 50 may be at an angle anywhere substantially between about 140 degrees and about degrees.

00371 In one or more embodiments of the present invention, a substantially non-planar cuffing element may be positioned such that a longitudinal axis of the substantially non-planar cuffing element 48 resides along the same path as the vertical axis 65 of the single roller cone bit 40.

00381 In a preferred embodiment of the present invention, the tip radius to extension ratio of a substantially non-planar cuffing element is substantially equal to 0.3. However, in one or more other embodiments of the present invention, the tip radius to extension ratio of a substantially non-planar cuffing element may be anywhere substantially between 0.2 and O.S.

00391 In one or more embodiments of the present invention, any of the substantially non-planar cuffing elements 48 and the substantially planar cutting elements 50 may be arranged to extend greater than or equal to 7/16 inches from the outer hemispherical surface of the single roller cone 54.

00401 In one or more embodiments of the present invention, any of the substantially non-planar cutting elements 48 and the substantially planar cutting elements 50 may be arranged to extend greata than or equal to 0. 55 inches from the outer hemispherical surface of the single rolla cone 54.

00411 In one or more embodiments of the present invention, any of the substantially non-planar cuffing elements 48 and the substantially planar cutting elements 50 may be arranged to extend greata than or equal to 1/2 inches from the outer hemispherical surface of the single rolla cone 54.

00421 In one or more embodiments of the present invention, any of the substantially non-planar cuffing elements 48 and the substantially planar cuffing elements 50 may be arranged to extend less than or equal to 0.6 inches from the outer hemispherical surface of the single roller cone 54.

00431 In one or more embodiments of the present invention, the substantially non-planar cutting elements 48 may have a structure in which an exterior material of the substantially non-planar cuffing element 48 is softer than an embedded region within the substantially non- planar cutting element 48. For example, the substantially non-planar cuffing element 48 may be embedded with a diamond insert. Such a structure in which a core harder than an exterior of a cuffing element is embedded within the cuffing element allows the substantially non-planar cuffing element 48 to be "self-sharpening" in nature, thereby increasing bit life and penetration effectiveness.

00441 The differing ranges of degrees with respect to the placement of the substantially non-planar cuffing elements 48 and the substantially planar cutting elements 50 may be defined by the regions on the single roller cone 46 designed to be the bore hole contacting zone and the wall contacting zone, respectively. In other words, when the single roller cone 46 shown in Figure 6 is in operation, a majority of the cuffing elements engaging a bottom of a bore hole are substantially non-planar cutting elements and a majority of the cutting elements engaging a wall of the bore hole (i.e., maintaining a gage of the bore hole) are substantially planar cutting elements.

00451 Moreover, the single roller cone 46 shown in Figure 6 may be described as having inner rows of cutting elements and outer rows of cutting elements. An inner row of cutting elements may be defined as a row of cutting elements falling within a particular range of degrees. Like with an inner row of cutting elements, an outer row of cutting elements may also be defined as a row of cutting elements falling within a particular range of degrees.

00461 In one or more other embodiments, an inner row of cutting elements may be defined as a row of cutting elements for penetrating into a formation, or cutting away from a bottom of a bore hole. In such embodiments, an outer row of cutting elements may be defined as a row of cuffing elements for cutting away from a wall of the bore hole, or maintaining a gage of the bore hole.

7] Advantages of the present invention may include one or more of the following. In one or more embodiments, a single roller cone bit has a cutting element arrangement effective in penetrating into hard formations and maintaining full gage of a bore hole. The cutting element arrangement includes substantially non-planar cutting elements positioned on a region of the single roller cone intended to engage a bottom of a bore hole and substantially planar cutting elements positioned on a region of the single roller cone intended to engage a wall ofthe bore hole.

00481 While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention.

Claims

Claims 1. A roller cone drill bit, comprising: a bit body adapted to be

coupled to a drill string; a bearing journal depending from the bit body, and a single roller cone rotatably attached to the bearing journal, the single roller cone having at least one substantially planar cutting element and at least one substantially non-planar cuffing element.
2. The roller cone drill bit of claim 1, wherein the at least one substantially non- planar cutting element is any one of a conical cutting element and a chisel cutting element.
3. The roller cone drill bit of claim I or 2, wherein the at least one substantially planar cutting element is a flat crested cutting element.
4. The roller cone drill bit of claim 1, 2 or 3, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element is formed of tungsten carbide.
5. The roller cone drill bit of any preceding claim, wherein the single roller cone is substantially hemispherical in shape.
6. The roller cone drill bit of any preceding claim, wherein an angular position of any cutting element is defined as the sum of (1) a journal angle from a horizontal plane and (2) an angle between an axis of the single roller cone and an axis of the cutting element.
7. The roller cone drill bit of claim 6, wherein the at least one substantially non- planar cutting element is disposed at an angle substantially between O degrees and degrees.
8. The roller cone drill bit of claim 6 or 7, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees.
9. The roller cone drill bit of claim 6 or 7, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 125 degrees and 165 degrees.
10. The roller cone drill bit of claim 6 or 7, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 135 degrees and 155 degrees.
11. The roller cone drill bit of claim 6 or 7, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 140 degrees and 150 degrees.
12. The roller cone drill bit of claim 6, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees, and wherein the at least one substantially non-planar cutting element is disposed at an angle substantially between O and 120 degrees.
13. The roller cone drill bit of any preceding claim, wherein the at least one substantially non-planar cutfflng element has a tip radius to extension ratio substantially equal to 0.3.
14. The roller cone drill bit of any preceding claim, wherein the at least one substantially planar cutting element has a tip radius to extension ratio substantially between 0.2 and 0.5.
15. The roller cone drill bit of any preceding claim, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends less than or equal to 0.6 inches from a surface of the single roller cone.
16. The roller cone drill bit of any preceding claim, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends greater than or equal to 7/16 inches from a surface of the single roller cone.
17. The roller cone drill bit of any preceding claim, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cuffing element extends greater than or equal to 0.5 inches from a surface ofthe single roller cone.
18. The roller cone drill bit of any preceding claim, wherein any one of the at least one substantially planar cuffing element and the at least one substantially non- planar cuffing element extends greater than or equal to O.SS inches from a surface of the single roller cone.
19. The roller cone drill bit of any preceding claim, wherein the at least one substantially non-planar cutting element is formed having a core harder than an exterior such that the substantially non-planar cutting element is self-sharpening.
20. A roller cone drill bit, comprising: a bit body adapted to be coupled to a drill string; a bearing journal depending from the bit body, and a single roller cone rotatably attached to the bearing journal, the single roller cone having a plurality of cutting elements disposed at positions selected such that a majority of cutting elements adapted to engage a bottom of a bore hole are substantially non-planar cuffing elements and a majority of cutting elements adapted to engage a wall of the bore hole are substantially planar cutting elements.
21. The roller cone drill bit of claim 20, wherein the at least one substantially non- planar cuffing element is any one of a conical cuffing element and a chisel cutting element.
22. The roller cone drill bit of claim 20 or 21, wherein the at least one substantially non-planar cutting element is formed having a core harder than an exterior such that the substantially non-planar cutting element is self-sharpening.
23. The roller cone drill bit of claim 20, 21 or 22, wherein the at least one substantially planar cutting element is a flat crested cutting element.
24. The roller cone drill bit of any of claims 20 to 23, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element is formed of tungsten carbide.
25. The roller cone drill bit of any of claims 20 to 24, wherein the single roller cone is substantially hemispherical in shape.
26. The roller cone drill bit of any of claims 20 to 25, wherein an angular position of any cutting element is defined as the sum of (1) a journal angle from a horizontal plane and (2) an angle between an axis of the single roller cone and an axis of the cutting element.
27. The roller cone drill bit of claim 26, wherein the at least one substantially non- planar cutting element is disposed at an angle substantially between O degrees and degrees.
28. The roller cone drill bit of claim 26 or 27, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees.
29. The roller cone drill bit of claim 26 or 27, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 125 degrees and 165 degrees.
30. The roller cone drill bit of claim 26 or 27, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 135 degrees and 155 degrees.
31. The roller cone drill bit of claim 26 or 27, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 140 degrees and 150 degrees.
32. The roller cone drill bit of claim 26, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees, and wherein the at least one substantially non-planar cutting element is disposed at an angle substantially between O and 120 degrees.
33. The roller cone drill bit of any of claims 20 to 32, wherein the at least one substantially non-planar cutting element has a tip radius to extension ratio substantially equal to 0.3.
34. The roller cone drill bit of any of claims 20 to 33, wherein the at least one substantially planar cutting element has a tip radius to extension ratio substantially between 0.2 and 0.5.
35. The roller cone drill bit of any of claims 20 to 34, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends less than or equal to 0.6 inches from a surface of the single roller cone.
36. The roller cone drill bit of any of claims 20 to 35, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends greater than or equal to 7/16 inches from a surface of the single roller cone.
37. The roller cone drill bit of any of claims 20 to 36, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends greater than or equal to 0.5 inches from a surface ofthe single roller cone.
38. The roller cone drill bit of any of claims 20 to 37, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends greater than or equal to 0.55 inches from a surface of the single roller cone.
39. A roller cone drill bit, comprising: a bit body adapted to be coupled to a drill string; a bearing joDal depending from the bit body; and a single roller cone rotatably attached to the bearing journal, the single roller cone having at least one inner row of cutting elements comprising at least one substantially non-planar cutting element and at least one outer row of cutting elements comprising at least one substantially planar cutting element.
40. The roller cone drill bit of claim 39, wherein the at least one substantially non- planar cutting element is any one of a conical cutting element and a chisel cutting element.
41. The roller cone drill bit of claim 39 or 40, wherein the at least one substantially planar cutting element is a flat crested cutting element.
42. The roller cone drill bit of claim 39, 40 or 41, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element is formed of tungsten carbide.
43. The roller cone drill bit of any of claims 39 to 42, wherein the single roller cone is substantially hemispherical in shape.
44. The roller cone drill bit of any of claims 39 to 43, wherein an angular position of any cutting element is defined as the sum of (1) a journal angle from a horizontal plane and (2) an angle between an axis of the single roller cone and an axis of the cutting element.
45. The roller cone drill bit of claim 44, wherein the at least one substantially non- planar cutting element is disposed at an angle substantially between O degrees and degrees.
46. The roller cone drill bit of claim 44 or 45, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees.
47. The roller cone drill bit of claim 44 or 45, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 125 degrees and 165 degrees.
48. The roller cone drill bit of claim 44 or 45, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 135 degrees and 155 degrees.
49. The roller cone drill bit of claim 44 or 45, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 140 degrees and 150 degrees. I
50. The roller cone drill bit of claim 44, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees, and wherein the at least one substantially non-planar cutting element is disposed at an angle substantially between O and 120 degrees.
51. The roller cone drill bit of any of claims 39 to 50, wherein the at least one substantially non-planar cutting element has a tip radius to extension ratio substantially equal to 0.3.
52. The roller cone drill bit of any of claims 39 to 51, wherein the at least one substantially planar cutting element has a tip radius to extension ratio substantially between 0.2 and 0.5.
53. The roller cone drill bit of any of claims 39 to 52, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends less than or equal to 0.6 inches from a surface of the single roller cone.
54. The roller cone drill bit of any of claims 39 to 53, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends greater than or equal to 7/16 inches from a surface of the single roller cone.
55. The roller cone drill bit of any of claims 39 to 54, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends greater than or equal to 0.5 inches from a surface of the single roller cone.
56. The roller cone drill bit of any of claims 39 to 55, wherein any one of the at least one substantially planar cutting element and the at least one substantially non- planar cutting element extends greater than or equal to 0.55 inches from a surface of the single roller cone.
57. The roller cone drill bit of any of claims 39 to 56, wherein the at least one substantially non-planar cutting element is formed having a core harder than an I exterior such that the substantially non-planar cutting element is self-sharpening.
58. A roller cone drill bit substantially as hereinbefore described with reference to the accompanying drawings.