U.S. patent application number 12/029197 was filed with the patent office on 2008-08-14 for rotary drag bit with increased back rake angle gauge cutter.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. Invention is credited to Michael L. Doster, Floyd C. Felderhoff, Robert M. Welch.
Application Number | 20080190670 12/029197 |
Document ID | / |
Family ID | 39530646 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080190670 |
Kind Code |
A1 |
Welch; Robert M. ; et
al. |
August 14, 2008 |
ROTARY DRAG BIT WITH INCREASED BACK RAKE ANGLE GAUGE CUTTER
Abstract
A fixed cutter rotary drill bit having gauge cutting elements at
large back rake angles are disclosed. The gauge is located at the
outer diameter side wall portion of the bit that extends from the
cutting end. The gauge and its cutting components contact the side
wall of the bore hole during drilling operations. The gauge cutting
elements may be configured at a back rake angle in a range of about
40.degree. to 70.degree..
Inventors: |
Welch; Robert M.; (The
Woodlands, TX) ; Felderhoff; Floyd C.; (Montgomery,
TX) ; Doster; Michael L.; (Spring, TX) |
Correspondence
Address: |
BRACEWELL & GIULIANI LLP
P.O. BOX 61389
HOUSTON
TX
77208-1389
US
|
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
39530646 |
Appl. No.: |
12/029197 |
Filed: |
February 11, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60889403 |
Feb 12, 2007 |
|
|
|
Current U.S.
Class: |
175/430 ;
175/431 |
Current CPC
Class: |
E21B 10/43 20130101 |
Class at
Publication: |
175/430 ;
175/431 |
International
Class: |
E21B 10/52 20060101
E21B010/52 |
Claims
1. A fixed cutter rotary drill bit, comprising: a bit body having a
bit axis and a cutting profile defined about the bit axis, the
cutting profile including a cone extending from the bit axis, a
nose adjacent the cone, a shoulder adjacent the nose, and a gauge
adjacent the shoulder, the gauge being adapted to engage a side
wall of a bore hole during drilling operations; and a plurality of
cutting elements extending from the cone, nose, shoulder and gauge
of the cutting profile, and at least one of the cutting elements
extending from the gauge has a back rake angle in a range of
40.degree. to 70.degree..
2. The fixed cutter rotary drill bit of claim 1, wherein the
cutting elements are selected from the group consisting of
polycrystalline diamond cutters (PDC), and impregnated and natural
diamond bit cutting elements.
3. The fixed cutter rotary drill bit of claim 1, wherein at least
some of the cutting elements extending from the gauge are ground
flat at an outer diameter of the bit body.
4. The fixed cutter rotary drill bit of claim 1, wherein each
cutting element has a cylindrical base that is secured in a pocket
in the bit body, a cutting element axis, and a cutting face with a
beveled edge.
5. The fixed cutter rotary drill bit of claim 4, wherein the
cutting face extends in a plane defining a back rake axis and a
side rake axis that is perpendicular to the back rake axis, with
both the back rake and side rake axes extending through the cutting
element axis, and the back rake axis being parallel to a surface of
the gauge and the bit axis, such that a positive back rake angle at
the gauge inclines the cutting face away from the bit axis.
6. The fixed cutter rotary drill bit of claim 5, wherein the back
rake angle is 40.degree..
7. The fixed cutter rotary drill bit of claim 5, wherein the back
rake angle is 65.degree..
8. A fixed cutter rotary drill bit, comprising: a bit body having a
bit axis, a threaded end for connection into a drill string, a
cutting end opposite the threaded end, and a cutting profile
defined about the bit axis, the cutting profile including a cone
extending from the bit axis, a nose adjacent the cone, a shoulder
adjacent the nose, and a gauge adjacent the shoulder and on a
radially outermost portion of the bit body relative to the bit
axis, the gauge being adapted to engage a side wall of a bore hole
during drilling operations; and a plurality of cutting elements
extending from the cutting end in the cone, nose, shoulder and
gauge of the cutting profile, and at least one of the cutting
elements extending from the gauge has a back rake angle in a range
of 40.degree. to 70.degree..
9. The fixed cutter rotary drill bit of claim 8, wherein the
cutting elements are selected from the group consisting of
polycrystalline diamond cutters (PDC), and impregnated and natural
diamond bit cutting elements.
10. The fixed cutter rotary drill bit of claim 8, wherein at least
some of the cutting elements extending from the gauge are ground
flat at an outer diameter of the bit body.
11. The fixed cutter rotary drill bit of claim 8, wherein each
cutting element has a cylindrical base that is secured in a pocket
in the cutting end, a cutting element axis, and a cutting face with
a beveled edge.
12. The fixed cutter rotary drill bit of claim 11, wherein the
cutting face extends in a plane defining a back rake axis and a
side rake axis that is perpendicular to the back rake axis, with
both the back rake and side rake axes extending through the cutting
element axis, and the back rake axis being parallel to a surface of
the gauge and the bit axis, such that a positive back rake angle at
the gauge inclines the cutting face away from the bit axis.
13. The fixed cutter rotary drill bit of claim 12, wherein the back
rake angle is 40.degree..
14. The fixed cutter rotary drill bit of claim 12, wherein the back
rake angle is 65.degree..
15. A fixed cutter rotary drill bit, comprising: a bit body having
a bit axis, a threaded end for connection into a drill string, a
cutting end opposite the threaded end, and a cutting profile
defined about the bit axis, the cutting profile including a cone
extending from the bit axis, a nose adjacent the cone, a shoulder
adjacent the nose, and a gauge adjacent the shoulder and on a
radially outermost portion of the bit body relative to the bit
axis, the gauge being adapted to engage a side wall of a bore hole
during drilling operations; a plurality of cutting elements
extending from the cutting end in the cone, nose, shoulder and
gauge of the cutting profile, each cutting element having a
cylindrical base, a cutting element axis, and a cutting face,
wherein the cutting face extends in a plane defining a back rake
axis and a side rake axis that is perpendicular to the back rake
axis, with both the back rake and side rake axes extending through
the cutting element axis, and the back rake axis being parallel to
a surface of the gauge and the bit axis, such that a positive back
rake angle at the gauge inclines the cutting face away from the bit
axis; and at least one of the cutting elements extending from the
gauge has a back rake angle in a range of 40.degree. to
70.degree..
16. A fixed cutter rotary drill bit according to claim 15, wherein
the cutting elements are selected from the group consisting of
polycrystalline diamond cutters (PDC), impregnated and natural
diamond bit cutting elements.
17. A fixed cutter rotary drill bit according to claim 15, wherein
at least some of the cutting elements extending from the gauge are
ground flat at an outer diameter of the bit body.
18. A fixed cutter rotary drill bit according to claim 15, wherein
the back rake angle is 40.degree..
19. A fixed cutter rotary drill bit according to claim 15, wherein
the back rake angle is 65.degree..
Description
[0001] This application claims priority to and the benefit of U.S.
Provisional Patent Application No. 60/889,403, which was filed on
Feb. 12, 2007, incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates in general to rotary drag bits
and, in particular, to an improved system, method, and apparatus
for a rotary drag bit having gauge cutting elements configured at
large back rake angles.
[0004] 2. Description of the Related Art
[0005] Earth-boring bits of the fixed cutter variety, commonly
referred to as drag bits, have no moving parts and employ an array
of hard inserts to scrape and shear formation material as the bit
is rotated in the borehole. Inserts on prior art fixed cutter bits
are typically aligned such that the inserts scrape the material
from the borehole bottom. For scraping to take place, the
longitudinal axis of the insert is typically at a small acute angle
(e.g., 0.degree. to 30.degree.) relative to the bit face. Such an
alignment places the cutting face of a cylindrically-shaped insert
nearly perpendicular to the borehole bottom. The contact area
between the cutting element and the formation starts out very small
but increases rapidly as penetration or depth of cut becomes
deeper.
[0006] High impact side-loading of drill bits during operation
results in non-compressive loading of the interface between the
diamond and tungsten carbide components on PDC cutters. This leads
to broken and/or chipped cutters in the upper shoulder and gauge
areas of the bit profile. High residual stresses are inherent in
this interface area as a result of varying planar and non-planar
geometries and the cutter manufacturing process. An improved
solution that overcomes these problems would be desirable.
SUMMARY OF THE INVENTION
[0007] Embodiments of a system, method, and apparatus for a fixed
cutter rotary drill bit having gauge cutting elements at large back
rake angles are disclosed. The gauge is located at the outer
diameter side wall portion of the bit that extends from the cutting
end. The gauge and its cutting components contact the side wall of
the bore hole during drilling operations.
[0008] In accordance with the invention, the gauge cutting elements
may be configured at a back rake angle in a range of about
40.degree. to 70.degree.. For applications where cutter damage is a
concern and side-cutting aggressiveness is a low priority, a very
high back rake angle helps ensure compressive cutter loading when
side impact forces are higher.
[0009] The foregoing and other objects and advantages of the
present invention will be apparent to those skilled in the art, in
view of the following detailed description of the present
invention, taken in conjunction with the appended claims and the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] So that the manner in which the features and advantages of
the present invention are attained and can be understood in more
detail, a more particular description of the invention briefly
summarized above may be had by reference to the embodiments thereof
that are illustrated in the appended drawings. However, the
drawings illustrate only some embodiments of the invention and
therefore are not to be considered limiting of its scope as the
invention may admit to other equally effective embodiments.
[0011] FIG. 1 is an isometric view of one embodiment of drill bit
constructed in accordance with the present invention;
[0012] FIG. 2 is a schematic representation of half of a cutting
profile of the drill bit of FIG. 1 and is constructed in accordance
with the present invention;
[0013] FIG. 3 is an illustration of cutter element
manipulation;
[0014] FIG. 4 is a side view of a cutting element showing a
conventional back rake angle;
[0015] FIG. 5 is a side view of one embodiment of a cutting element
showing a back rake angle constructed in accordance with the
present invention; and
[0016] FIG. 6 is a side view of another embodiment of a cutting
element showing a back rake angle constructed in accordance with
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring to FIG. 1, one embodiment of a fixed cutter rotary
drill bit 11 is shown. Bit 11 has a bit axis 12 and a threaded end
13 for connection into a drill string. A cutting end 15 at a
generally opposite end of the bit 11 is provided with a plurality
of hard cutting elements 17 (e.g., polycrystalline diamond cutters,
etc.) arranged about cutting end 15 to effect efficient
disintegration of formation material as bit 11 is rotated in a bore
hole.
[0018] As shown in the embodiment of FIG. 5, each cutting element
17 has a cylindrical base 19 with an axis 20, and is secured in a
preformed pocket 21 provided on cutting end 15 and a cutting face
23 that engages the formation material. As illustrated, cutting
element 17 may comprise a frustoconical cutting end that forms a
beveled edge adjacent the face 23. Cutting element 17 acts somewhat
like a plow that generally directs a high percentage of the
material of the formation up its flat face.
[0019] Referring now to FIGS. 1 and 2, the arrangement of cutting
elements 17 on bit 11 is configured in an overall cutting profile
25 (approximately half of which is shown in FIG. 2) about bit axis
12. Starting at axis 12 at the inner diameter of bit 11 and moving
toward the outer diameter of bit 11 (right to left in FIG. 2),
profile 25 comprises various areas, including a cone 27, a nose 29,
a shoulder 31, and a gauge or gauge pad or surface 33. The gauge 33
is on a radially outermost portion of the bit body relative to the
bit axis 12.
[0020] The gauge 33 essentially defines the flat, outer diameter
side wall portion of bit 11 that extends from cutting end 15 (FIG.
1). The gauge 33 and its cutting components are proximal to and
contact the side wall 34 (see FIG. 3) of the bore hole during
drilling operations with bit 11. As shown in FIG. 1, a plurality of
channels or grooves 35 (e.g., junk slots) extend from cutting end
15 through gauge 33 to provide a clearance area for the removal of
cuttings and chips formed by cutting elements 17.
[0021] As shown in FIG. 1, a plurality of cutting elements 17 are
provided on gauge 33 of bit 11. Active, gauge cutting elements 17
on gauge 33 provide the ability to actively cut formation material
at the side wall 34 (FIG. 3) of the bore hole to provide dynamic
stability and improved gauge-holding ability in earth-boring bits
of the fixed cutter variety. As FIG. 1 illustrates, at least some
of the gauge cutting elements 17 on gauge 33 may be ground flat at
the outer diameter of bit 11 for some types of applications. Bit 11
is illustrated as a polycrystalline diamond cutter (PDC) bit, but
cutting elements 17 are equally useful in other fixed cutter or
drag bits that include a gauge or gauge surface for engagement with
the side wall of the bore hole. Examples include impregnated and
natural diamond bit cutting elements.
[0022] Referring now to FIG. 4, one type of prior art cutting
element 117 for cutting formation is shown. Cutting element 117 is
a conventional PDC cutting element and is cylindrical in shape.
Cutting element 117 has an axis 120 and a diamond table on its face
123 with an essentially circular cross-section. Cutting element 117
has a cutter back rake angle 140 of 20.degree.. However,
conventional cutter back rake angles of 5.degree. to 30.degree.
also are known.
[0023] As shown in FIG. 3, the circle 23 represents the face of
cutting element 17 on the gauge 33. A back rake axis 42 is shown as
vertical in the drawing, and parallel to the gauge 33, bit axis 12,
and the bore side wall 34. A side rake axis 44 is perpendicular to
axis 42, gauge 33, the bit axis 12, and the bore side wall 34.
[0024] In a "nominal" position on the gauge 33, both the back rake
angle and the side rake angle of element 17 are zero. Thus, in one
embodiment of the nominal position, face 23 extends in the plane
defined by axes 42, 44, such that it is perpendicular to the gauge
33 and bore sidewall, and face 23 is parallel to axes 12, 42 and
44. Rotating the face 23 about axis 42 results in a modification to
the back rake angle. In the gauge area 33, a positive back rake
angle inclines the cutting face 23 away from the bit axis 12 and
toward the borehole 34. Rotating the face 23 about axis 44 results
in a modification to the side rake angle. A positive side rake
angle includes the cutting face 23 away from the drill string and
toward the bottom of the bore hole.
[0025] Referring again to FIG. 5, one embodiment of cutting element
17 in accordance with the invention is shown with a relatively
large positive back rake angle 42 of 40.degree., and a 0.degree.
side rake angle. In FIG. 6, another embodiment of cutting element
17 is shown at a 65.degree. back rake angle 42, and a 0.degree.
side rake angle. The invention may comprise back rake angles of
approximately 40.degree. to 70.degree..
[0026] For applications where cutter damage is a concern and
side-cutting (e.g., cutting with the gauge 33 of the cutting
profile 25) aggressiveness is a low priority, a very high back rake
angle help ensures compressive cutter loading when side impact
forces are higher. This is accomplished by lowering the y-component
force (see, e.g., FIGS. 5 and 6) that results from side loads.
[0027] For example, comparing FIGS. 4 and 5, lower back rake angles
result in higher loading in the y-direction, as depicted by the
vectors F.sub.y. This is detrimental to cutter integrity with
respect to the diamond/tungsten carbide interface where residual
stresses are high. Although the direction of overall force, F.sub.f
(which is normal to the bore side wall 34), will vary slightly with
dynamic events, the invention enhances the cutter integrity and
dynamic stability of fixed cutter drill bits.
[0028] While the invention has been shown or described in only some
of its forms, it should be apparent to those skilled in the art
that it is not so limited, but is susceptible to various changes
without departing from the scope of the invention.
* * * * *