U.S. patent application number 10/871605 was filed with the patent office on 2005-05-26 for cutting element arrangement for single roller cone bit.
Invention is credited to Belnap, Dan, Birne-Browne, Ronald, Butland, Richard, Herman, John, Loiselle, Louis, Nese, Per, Wilson, Peter, Witman, George.
Application Number | 20050109543 10/871605 |
Document ID | / |
Family ID | 32853636 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050109543 |
Kind Code |
A1 |
Witman, George ; et
al. |
May 26, 2005 |
Cutting element arrangement for single roller cone bit
Abstract
A cutting element arrangement for a single roller cone bit
includes both at least one substantially non-planar cutting element
and at least one substantially planar cutting element. The
substantially non-planar cutting element is disposed on an inner
row of the single roller cone and the substantially planar cutting
element is disposed on an outer row of the single roller cone. With
such an arrangement, the substantially non-planar inner row cutting
elements effectively penetrate formations while the substantially
planar outer row cutting elements maintain bore hole gage.
Inventors: |
Witman, George; (Sugarland,
TX) ; Wilson, Peter; (Norman, OK) ; Butland,
Richard; (Calgary, CA) ; Belnap, Dan;
(Pleasant Grove, UT) ; Herman, John; (Airdrie,
CA) ; Birne-Browne, Ronald; (Calgary, CA) ;
Nese, Per; (Calgary, CA) ; Loiselle, Louis;
(Edmonton, CA) |
Correspondence
Address: |
OSHA & MAY L.L.P.
Suite 2800
1221 McKinney
Houston
TX
77010
US
|
Family ID: |
32853636 |
Appl. No.: |
10/871605 |
Filed: |
June 18, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60484172 |
Jul 1, 2003 |
|
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|
Current U.S.
Class: |
175/365 |
Current CPC
Class: |
E21B 17/1092 20130101;
E21B 10/16 20130101 |
Class at
Publication: |
175/365 |
International
Class: |
E21B 010/08 |
Claims
What is claimed is:
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
cutting 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 1, wherein the at least one
substantially planar cutting element is a flat crested cutting
element.
4. The roller cone drill bit of claim 1, 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 claim 1, wherein the single roller
cone is substantially hemispherical in shape.
6. The roller cone drill bit of claim 1, 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 0 degrees and 120 degrees.
8. 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.
9. The roller cone drill bit of claim 6, 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, 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, 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 0 and 120 degrees.
13. The roller cone drill bit of claim 1, wherein the at least one
substantially non-planar cutting element has a tip radius to
extension ratio substantially equal to 0.3.
14. The roller cone drill bit of claim 1, 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 claim 1, 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 claim 1, 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 {fraction (7/16)} inches from a surface of the single
roller cone.
17. The roller cone drill bit of claim 1, 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.
18. The roller cone drill bit of claim 1, 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.
19. The roller cone drill bit of claim 1, 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 cutting 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 cutting element is any one of a conical
cutting element and a chisel cutting element.
22. The roller cone drill bit of claim 20, 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, wherein the at least one
substantially planar cutting element is a flat crested cutting
element.
24. The roller cone drill bit of claim 20, 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 claim 20, wherein the single
roller cone is substantially hemispherical in shape.
26. The roller cone drill bit of claim 20, 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 0 degrees and 120 degrees.
28. 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.
29. The roller cone drill bit of claim 26, 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, 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, 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 0 and 120 degrees.
33. The roller cone drill bit of claim 20, 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 claim 20, 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 claim 20, 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 claim 20, 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 {fraction (7/16)} inches from a surface of the single
roller cone.
37. The roller cone drill bit of claim 20, 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.
38. The roller cone drill bit of claim 20, 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 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 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, wherein the at least one
substantially planar cutting element is a flat crested cutting
element.
42. The roller cone drill bit of claim 39, 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 claim 39, wherein the single
roller cone is substantially hemispherical in shape.
44. The roller cone drill bit of claim 39, 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 0 degrees and 120 degrees.
46. 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.
47. The roller cone drill bit of claim 44, 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, 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, wherein the at least one
substantially planar cutting element is disposed at an angle
substantially between 140 degrees and 150 degrees.
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 0 and 120 degrees.
51. The roller cone drill bit of claim 39, 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 claim 39, 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 claim 39, 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 claim 39, 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 {fraction (7/16)} inches from a surface of the single
roller cone.
55. The roller cone drill bit of claim 39, 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 claim 39, 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 claim 39, 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.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority, pursuant to 35 U.S.C.
.sctn. 119(e), of U.S. Provisional Patent Application No.
60/484,172 filed Jul. 1, 2003. That Application is incorporated by
reference in its entirety.
BACKGROUND OF INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to the field of roller cone
("rock") bits used to drill wellbores through earth formations.
More specifically, the invention is related to an arrangement of
cutting elements ("inserts") used in roller cone bits having a
single roller cone.
[0004] 2. Background Art
[0005] 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.
[0006] 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
formation being drilled.
[0007] The cutting elements on a cone of a three-cone bit are
generally classified as inner-row cutting elements and gage-row
cutting elements. Inner row cutting elements engage the bore hole
bottom, but not the well bore wall. Gage-row cutting elements
engage the well bore wall and sometimes a small outer ring portion
of the bore hole bottom. The direction of motion of cutting
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.
[0008] 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.
[0009] 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. FIG. 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.
[0010] 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. FIG. 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.
[0011] Such substantially non-planar cutting elements may be
characterized, or otherwise defined, as having a particular tip
radius to extension ratio. For example, FIG. 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, FIGS. 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.
[0012] 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.
[0013] 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
[0014] 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 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 cutting elements and a
majority of cutting elements adapted to engage a wall of the bore
hole are substantially planar cutting elements.
[0015] 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 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.
[0016] 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.
[0017] Other aspects and advantages of the invention will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 shows a substantially planar cutting element.
[0019] FIG. 2 shows a substantially non-planar cutting element.
[0020] FIG. 3 shows a conical cutting element.
[0021] FIG. 4a shows a front view of a chisel cutting element.
[0022] FIG. 4b shows a side view of a chisel cutting element.
[0023] FIG. 5 shows a generalized cut away view of a single roller
cone bit.
[0024] FIG. 6 shows a single roller cone bit in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION
[0025] 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.
[0026] 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 FIG. 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 during 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.
[0027] 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.
[0028] 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.
[0029] The journal 1A depends from the bit body 1 such that it
defines an angle .alpha. between the rotational axis 9 of the
journal 1A and the rotational axis 11 of the bit body 1. The size
of this angle .alpha. 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
10 therefore define the drill diameter 13 of the bit.
[0030] 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.
[0031] 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.
[0032] FIG. 6 shows an exemplary single roller cone bit 40 in
accordance with an embodiment of the present invention. As shown in
FIG. 6, an angular position of a cutting element of a single roller
cone bit 40 may be defined as follows. A first angle .alpha. 60 is
defined as a journal angle from a horizontal plane 62. A second
angle .theta. 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 .alpha. 60 and the second angle .theta. 64 can then
be used to describe the angular position of a particular cutting
element. Those skilled in the art will appreciate that the
foregoing cutting element angular position description is
applicable to describing an arrangement of cutting elements in all
three dimensions. In other words, an angular position of a cutting
element defined as the sum of the journal angle 60 from a
horizontal plane 62 and an angle between an axis 66 of the single
roller cone 54 and an axis of a cutting element applies to a three
dimensional layout of the single roller cone bit 40.
[0033] With respect to the definition of cutting element angular
position discussed above, substantially non-planar cutting elements
(e.g., conical and chisel cutting elements) 48 may be selected and
disposed at an angle preferably anywhere substantially between 0
degrees and 120 degrees. Substantially planar cutting elements
(e.g., flat crested cutting elements) 50 may be selected and
disposed at an angle anywhere substantially between 120 degrees and
175 degrees. Note that FIG. 6 is not to scale with respect to the
indications of the angle measurements.
[0034] Accordingly, a single roller cone bit 40 is provided that
has a cutting element 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 roller cone bit 40. The shape of the substantially
non-planar cutting elements allows them to penetrate a hard
formation effectively.
[0035] 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 elements
50 provides greater 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 elements 50 to cut with an efficient
shearing action.
[0036] 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 165 degrees.
[0037] 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 135 degrees and about 155 degrees.
[0038] 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 140 degrees and about 150 degrees.
[0039] In one or more embodiments of the present invention, a
substantially non-planar cutting element may be positioned such
that a longitudinal axis of the substantially non-planar cutting
element 48 resides along the same path as the vertical axis 65 of
the single roller cone bit 40.
[0040] In a preferred embodiment of the present invention, the tip
radius to extension ratio of a substantially non-planar cutting
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 cutting element may
be anywhere substantially between 0.2 and 0.5.
[0041] 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
greater than or equal to {fraction (7/16)} inches from the outer
hemispherical surface of the single roller cone 54.
[0042] 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
greater than or equal to 0.55 inches from the outer hemispherical
surface of the single roller cone 54.
[0043] 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
greater than or equal to {fraction (1/2)} inches from the outer
hemispherical surface of the single roller cone 54.
[0044] 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
less than or equal to 0.6 inches from the outer hemispherical
surface of the single roller cone 54.
[0045] 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
cutting element 48 is softer than an embedded region within the
substantially non-planar cutting element 48. For example, the
substantially non-planar cutting element 48 may be embedded with a
diamond insert. Such a structure in which a core harder than an
exterior of a cutting element is embedded within the cutting
element allows the substantially non-planar cutting element 48 to
be "self-sharpening" in nature, thereby increasing bit life and
penetration effectiveness.
[0046] The differing ranges of degrees with respect to the
placement of the substantially non-planar cutting 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 FIG. 6 is in
operation, a majority of the cutting 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.
[0047] Moreover, the single roller cone 46 shown in FIG. 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.
[0048] 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 cutting elements for cutting away from a
wall of the bore hole, or maintaining a gage of the bore hole.
[0049] 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 of the bore hole.
[0050] 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
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
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