U.S. patent application number 12/147179 was filed with the patent office on 2009-01-01 for cutter pocket having reduced stress concentration.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. Invention is credited to Marc W. Bird, Andy Oxford.
Application Number | 20090000827 12/147179 |
Document ID | / |
Family ID | 40159018 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090000827 |
Kind Code |
A1 |
Bird; Marc W. ; et
al. |
January 1, 2009 |
CUTTER POCKET HAVING REDUCED STRESS CONCENTRATION
Abstract
A method for forming a drag bit using displacements having a
rounded end that creates a cutter pocket having a rounded rear
portion. The displacement may comprise an insert on the rounded end
that remains in the drag bit during and after formation. A cutter
element may then be attached to the upper portion of the insert.
The rounded shape of the insert provides a more even force
distribution.
Inventors: |
Bird; Marc W.; (Houston,
TX) ; Oxford; Andy; (Magnolia, TX) |
Correspondence
Address: |
Bracewell & Giuliani LLP
P.O. Box 61389
Houston
TX
77208-1389
US
|
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
40159018 |
Appl. No.: |
12/147179 |
Filed: |
June 26, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60946300 |
Jun 26, 2007 |
|
|
|
Current U.S.
Class: |
175/432 ;
76/108.4 |
Current CPC
Class: |
E21B 10/573 20130101;
B22F 2005/001 20130101; E21B 10/55 20130101 |
Class at
Publication: |
175/432 ;
76/108.4 |
International
Class: |
E21B 10/46 20060101
E21B010/46 |
Claims
1. A method of forming a bit body for an earth boring drill bit
comprising: combining bit body raw materials and a displacement
having a rounded end into a bit body casting form; orienting the
rounded end of the displacement to extend into the bit body
materials; and processing the materials in the casting form to form
a bit body, wherein the presence of the displacement extending into
the bit body raw materials during the step of processing the
materials forms a cutter pocket in the bit body.
2. The method of claim 1 further comprising, removing the
displacement from the cutter pocket.
3. The method of claim 1, wherein the displacement comprises an
insert portion not removable from the bit.
4. The method of claim 1, wherein the displacement comprises a
portion formed from an erodible material and an insert portion
comprising the rounded end.
5. The method of claim 4, wherein the insert is integrally formed
in the bit body, the method further comprising removing the
removable portion, and affixing a cutting element to the
insert.
6. The method of claim 1, wherein the raw materials comprise
tungsten and a binder.
7. The method of claim 2 further comprising, affixing a cutting
element into the cutter pocket.
8. The method claim 1, further comprising combining a plurality of
displacements into the casting form to thereby form a plurality of
cutter pockets.
9. The method of claim 1, wherein the cutter pocket rounded bottom
end has a shape selected from the group consisting of
hemispherical, elliptical, and frusto-conical.
10. The method of claim 1, wherein the displacement comprises an
erodible material.
11. The method of claim 10, wherein the displacement comprises
material selected from the group consisting of graphite and
silicone carbide, refractory materials, compressed particles, and
combinations thereof.
12. The method of claim 1 further comprising, removing at least a
portion of the displacement from the formed bit body, affixing a
cutting element within the cutter pocket, coupling the bit body
with insert to a drill pipe, boring a wellbore with the bit body
and drill pipe.
13. An earth boring bit formed using a casting process, the b it
attachable to a drill string for forming a subterranean wellbore,
the bit comprising: a bit body; a blade extending from the bit
body; and a cutter pocket having a rounded bottom end formed in the
blade during the casting process, wherein the rounded bottom end is
formed using a displacement having a rounded end.
14. The earth boring bit of claim 13, wherein the displacement is
formed using an erodible material.
15. The earth boring bit of claim 13, wherein the displacement
comprises an insert on the rounded end.
16. The earth boring bit of claim 13, wherein the displacement
comprises a mid section and a rear portion having a rounded
end.
17. The earth boring bit of claim 13, wherein the displacement
rounded end is orientable in a bit body casting mold to form a
cutter pocket having a rounded bottom.
18. The earth boring bit of claim 16, wherein the displacement mid
section and rear portion comprises an erodible material.
19. The earth boring bit of claim 13, wherein the displacement
comprises material selected from the group consisting of graphite
and silicone carbide, refractory materials, compressed particles,
and combinations thereof.
20. The earth boring bit of claim 13, wherein the rounded end has a
shape selected from the group consisting of hemispherical,
elliptical, and frusto-conical.
Description
RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of
co-pending U.S. Provisional Application Ser. No. 60/946,300, filed
Jun. 26, 2007, the full disclosure of which is hereby incorporated
by reference herein.
BACKGROUND
[0002] 1. Field of Invention
[0003] The disclosure herein relates to contoured cutting teeth for
use with a drilling bit. More specifically, the present disclosure
concerns inserts having a spherical shaped rear portion disposed in
a correspondingly formed pocket, wherein the pocket is situated on
the cutting surface of a drag bit. The present disclosure also
concerns a method for forming the pockets on the face of a drill
bit.
[0004] 2. Description of Prior Art
[0005] Earth boring bits for drilling wellbores into subterranean
formations include roller cone bits and drag bits. The earth boring
bits are typically connectable to a drilling system via a threaded
connection disposed on the bottom portion of the bit. Drag type
bits includes blades formed on the lower surface of the bit. The
blades comprise a raised portion of material having a generally
rectangular cross-section extending roughly from the center portion
of the bit surface and radially outward along a side of the bit.
Cutter pockets are formed on the upper surface of the blade,
wherein the respective axes of the pockets are generally parallel
with other pockets on the individual blade. Typically, the pockets
comprise a hollowed out trough portion of the upper surface of the
blade, wherein the pockets are formed to receive a cutting element
therein.
[0006] The cutting elements can be attached in any number of ways,
such as welding and brazing or other attachment means. The cutting
element has a generally cylindrical shape with a cutting face on
one end and planar on its other end. It is well known in the prior
art to add polycrystalline diamond compact, i.e., PDC, on the face
of the cutting element. The cutting element body is typically
formed of a relatively hard material such as sintered tungsten
carbide. The PDC layer may be mounted directly on the mounting body
or on an intermediate carrier also generally made from a sintered
tungsten carbide.
[0007] The bit body is usually comprised of either a tungsten
carbide matrix or various forms of steel. Drilling systems
typically utilize the weight on bit to press down into the rock
that combined with the torque crushes the rock which causes the
drilling action. Continued turning of the drill string pushes the
teeth through the rock by the combined forces of the weight on bit
and the torque.
[0008] Known displacements have planar ends that form cutter
pockets with corresponding flat bottoms. During use of bit bodies
having flat bottom cutter pockets, the geometry produces high
stresses in the bit body adjacent the cutter pocket bottom. The
high stresses can initiate cracking in the bit body thereby
reducing bit life.
SUMMARY OF INVENTION
[0009] Disclosed herein is a drag bit and a method for creating a
drag bit. In one embodiment, the drag bit comprises a blade on its
cutting face, with a series of pockets on the blade formed using
displacements. In one embodiment, the displacement comprises an
insert on one end with removable displacement material on the
other. The insert end opposite the displacement is rounded and
oriented to be at the cutter pocket bottom while forming the bit.
The insert and displacement converge at a planar surface. After the
displacement material is removed from the insert, a cutting element
may be attached to the end of the insert. Optionally, the
displacement may comprise only removable displacement material with
one or more rounded ends. A method is included herein for forming
the pockets on the blade of the drag bit. The method involves
forming the cutter pocket with the displacement having an insert
with a rounded shaped end to form a rounded cutter pocket bottom,
cleaning the removable portion of the displacement, and adding a
cutting element to the end of the insert. Optionally, a method is
disclosed wherein a fully removable displacement is used to form a
cutter pocket with a rounded bottom. After casting a bit body using
the displacement, the displacement(s) can be removed and a cutting
element having a rounded bottom corresponding to the cutter pocket
bottom can be affixed in the cutting pocket.
BRIEF DESCRIPTION OF DRAWINGS
[0010] Some of the features and benefits of the present invention
having been stated, others will become apparent as the description
proceeds when taken in conjunction with the accompanying drawings,
in which:
[0011] FIG. 1 is a bottom view of a drill bit shown during the
formation process.
[0012] FIG. 2 is a side view of an example of a displacement for
forming a cutter pocket.
[0013] FIG. 3 is a side view of a displacement for forming a cutter
pocket having an insert on one end.
[0014] FIG. 4 is a partial cutaway view of a displacement forming a
cutter pocket having an insert.
[0015] FIG. 5 is a partial cutaway view of a cutting element
comprising an insert on one end.
[0016] FIG. 6 is a partial sectional view of a displacement in a
bit body having an elliptical end.
[0017] FIG. 7 is a partial sectional view of a displacement in a
bit body having an elliptical end.
[0018] FIG. 8 is a partial sectional view of a displacement in a
bit body having a frusto-conical end.
[0019] FIG. 9 is a partial sectional view of an example of a
drilling system employing a drill bit having a cutter pocket with a
rounded bottom.
[0020] FIG. 10 is a partial cutaway view of a cutting element with
a rounded end in a bit body.
[0021] While the invention will be described in connection with the
preferred embodiments, it will be understood that it is not
intended to limit the invention to that embodiment. On the
contrary, it is intended to cover all alternatives, modifications,
and equivalents, as may be included within the spirit and scope of
the invention as defined by the appended claims.
DETAILED DESCRIPTION OF INVENTION
[0022] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings in which
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the illustrated embodiments set forth
herein; rather, these embodiments are provided so that this
disclosure will be through and complete, and will fully convey the
scope of the invention to those skilled in the art. Like numbers
refer to like elements throughout.
[0023] It is to be understood that the invention is not limited to
the exact details of construction, operation, exact materials, or
embodiments shown and described, as modifications and equivalents
will be apparent to one skilled in the art. In the drawings and
specification, there have been disclosed illustrative embodiments
of the invention and, although specific terms are employed, they
are used in a generic and descriptive sense only and not for the
purpose of limitation. Accordingly, the invention is therefore to
be limited only by the scope of the appended claims.
[0024] Disclosed herein is a device and method regarding forming
cutter pockets and cutting elements of a drag bit. In one
embodiment, a cutter pocket is formed using a displacement
comprising removable displacement material and a non-removal insert
having a rounded end. The displacement is oriented within a bit
body casting form so when the bit body is formed, the rounded ended
of the insert is integral within the bit body with the removable
displacement between the insert and the bit outer surface. After
removing the displacement material from the insert a cutting
element can be attached to the insert's free end. Another way to
form a rounded cutter element to bit body interface is to form a
bit body using a rounded end displacement, wherein the entire
displacement comprises removable material. In one embodiment, the
cutter element(s) to bit body interface describes the contact
surface between the cutter element and the bit body. The cutter
element(s)/bit body interface also describes the forces and/or
force distributions transferred between the cutter element(s) and
the bit body. The interface can describe a single cutting element
and bit body, a plurality of cutting elements and the bit body, or
all cutting elements and the bit body. After casting the bit and
then cleaning the displacement from the cutter pocket, a cutting
element with a correspondingly rounded bottom can be affixed in the
rounded bottom cutter pocket. One of the advantages of having a
rounded cutter element to bit body interface is the forces
experienced by the cutting element during cutting are transferred
to the bit body through the insert (or cutter element) rounded end.
A rounded interface has a greater area than traditional planar or
flat bit body/cutting element interfaces, thus stresses imparted by
the cutting element to the bit body are more evenly distributed
throughout the bit body. More even stress distribution thereby
minimizes stress concentrations in the bit body. Additionally, the
improvement disclosed herein removes sharp corners in the cutter
pocket rear portion. In contrast, some diamond fixed cutter bits
have experienced primary cutter pocket cracking, especially for the
cutters located proximate to the bit axis. These cracks initiate
from the joint of the cutter pocket seat and propagate down towards
the nozzle and/or front blade root.
[0025] FIG. 1 illustrates a bottom view of an example of a bit body
10 being formed in accordance with the present disclosure. In this
embodiment, the bit body 10 comprises a series of blades 12 formed
on the bit face 14, wherein the blades 12 radially extend outward
from the center towards the outer radius of the bit face 14. Cutter
pockets 13 are generally formed along the upper or outer edge of
the blade for receiving cutting elements within the pockets.
Displacements may be used in forming these cutter pockets by
positioning the displacements inside a form as the bit body is
being cast. One example of this novel process is provided in FIG. 1
where displacements 16 were situated in a casting form before bit
body raw materials were added. The displacements 16 were kept in
place in the casting form during the casting process and integrated
with the bit body 10. Examples of bit body raw materials include a
hard material, such as tungsten or tungsten carbide, and binder
constituents. Binder constituents include copper, nickel, other
soft metals, and combinations thereof. Processing the bit body raw
materials within the casting form may comprise heating to soften
and/or melt the binder enabling the softened binder material to
migrate within the hard material, and when cooled will bind the
hard materials together. However the scope of the present
disclosure is not limited to a high temperature forming process,
but instead other processing methods can be employed with the
forming method described herein, such as a high pressure forming
process, or a combination of increased pressure and increased
temperature.
[0026] In one embodiment, the displacements 16 in FIG. 1 comprise a
material that retains its shape during the bit casting process, but
are removable and can be cleaned away after the bit body 10 is
removed from the form. Examples of materials for the displacements
16 include generally, graphite silicon carbide, refractory
materials, compressed particulate matter, combinations thereof, and
similar substances. Sand blasting is one example method that can be
employed for cleaning displacement material from within the cutter
pocket 13. Accordingly the displacement(s) 16 may optionally
comprise erodible materials removable with some applied impact,
such as by particles (for example sand), water, air, or any other
stream comprising matter directed at the displacement. In this
embodiment, one end of the displacement 16 is shown protruding away
from the cutter face. The rearward end, or the displacement rear
portion 18 (forming the cutter pocket 13) is shown in a dashed
outline on the blade face 12. Optionally, use of the stress
minimizing cutter pockets can be limited to the portions of the bit
face having cutters exposed to localized high stresses.
[0027] FIG. 2 provides a side view of an embodiment of a
displacement 24 such as used to form a cutter pocket 13 in the bit
body 10 of FIG. 1. The displacement 24 comprises a rear section 26,
a front section 28, and an indicator groove 30. A groove 30, formed
proximate to the front 28 circumscribes the displacement 24 outer
periphery. The displacement 24 rear section 26 is rounded for
forming a shaped cutter pocket with a rounded bottom. Optionally,
the rear section 26 of this displacement 24 may be hemi-spherical,
oval, or have any radial shape, with or without tapers. Examples of
displacements 24 having an end with an elliptical shape are
provided in a side partial sectional view in FIGS. 6 and 7. An
example of displacements 24 having an end with a frusto-conical
shape is provided in a side partial sectional view in FIG. 8. In
other embodiments, the front section 28 may be flat, elliptical,
chamfered, or have a chisel shape. The present method also includes
orienting a displacement having a rounded end within a bit body
casting form so the rounded end is used to shape the bottom end 15
of a cutter pocket 13. The optional groove 30 is formed to indicate
displacement position and to allow manufacturing personnel to
properly align displacements 24 with the face of the blade 14.
Optionally, the cutter can be formed as a uni-body assembly having
a rounded rear portion, in this embodiment the cutter would not
have an added insert.
[0028] FIG. 3 provides a side view of an alternative displacement
42 embodiment. The displacement 42 of FIG. 3 comprises an insert 46
rounded on its free or bottom end (i.e. the end inserted into a
rounded bottom cutter pocket 13). The displacement 42 further
includes a cylindrically shaped mid section 45 attached to the
insert 46. A front section 44 is shown on the mid section 45
opposite the insert 46. The mid section 45 and front section 44 may
comprise above described displacement material such as graphite or
silicon carbide. The insert 46 may be glued to the mid section 45
prior to being placed in the mold. Forming a bit body 10 with the
displacement 42 of FIG. 3 includes removing the front portion 44
and mid section 45 after the casting process. The step of removing
may include the displacement cleaning/removal method as described
above. Removing the mid section 45 leaves the insert 46 within the
cutter pocket 13. As discussed below and illustrated in FIG. 5, a
cutter element having a rounded end and a cutter face can be
affixed to the insert 46 within the cutter pocket. Typical methods
of adhering cutter elements in formed pockets exist, such as
welding, brazing and possibly gluing. Accordingly, using the insert
46 results in cutter forces being more evenly distributed from the
cutter element to the cutter blades 12 and bit 10. The insert 46
may comprise mild carbon steel, such as 1018 carbon steel, tungsten
carbide, alloys, sintered tungsten carbide, low carbon alloy
steels, or combinations thereof. Cutter pockets formed using
displacements 42 that comprise an insert 46 may optionally be
described as extending from the flat or planar surface of the
insert 46 to the cutter pocket opening on the bit body surface.
When described in this fashion, the insert 46 would not be in the
cutter pocket and the cutter pocket would have a flat bottom
defined by the insert 46 upper surface. Optionally, the cutter
pocket can be described as extending to the rounded interface
between the insert 46 and bit body 12, thus the insert 46 would be
in the bottom of the cutter pocket. Irrespective of how a cutter
pocket is described, inserts 46 having a rounded end provide a
rounded cutting element to bit body interface.
[0029] FIG. 4 illustrates a side partial sectional view of the
displacement 42 of FIG. 3 disposed in a bit body 12 cutter pocket
13. This illustrates an example of a displacement 42 combined with
the bit body 12 during the casting process. The front portion 44 is
removable, such as by using the above described process, thereby
leaving the insert 46 within the pocket 13. The cutter pocket
bottom 15 rounded configuration with the correspondingly contoured
insert 46 forms a rounded cutter element to bit body interface to
better distribute bit body 12 stress than the traditional flat or
planar cutter element to bit body interfaces. Unlike the bit bodies
having high stress concentrations from flat bottom cutting
elements; earth boring bit bodies formed using the displacements
(24, 42) described herein will experience a substantially equal
cutter element to bit body stress distribution. Reducing stress
concentration in the bit body reduces a likelihood of crack
initiation and/or crack growth, thereby increasing useful bit
life.
[0030] After removing the front portion 44 of FIG. 4, a cutting
element 35 may be secured onto the insert 46. One example is
provided in FIG. 5 that illustrates a side view of the cutting
element 35 comprising a cutter body 36 secured to the insert 46
within the cutter pocket 13. Here the cutting element 35 is
attached to the insert 46 within the cutter pocket 13 created by
the mid section 45 (FIG. 4) and includes a cutter tip 38 on its
outwardly facing surface. As is known, the cutter tip 38 may be a
polycrystalline diamond compact (PDC) and include hard or super
hard materials.
[0031] With regard to the displacement 24 shown in FIG. 2, after
forming a bit body 10 using a casting process, then blast removing
the displacement material, a cutting element 31 (FIG. 10) having a
rounded bottom 32 and a cutting tip 33 is illustrated attached in
the rounded bottom pocket 13. Brazing or some other means of
attachment can be employed for securing the cutting element 31
within the pocket 13.
[0032] FIG. 9 illustrates an embodiment of a drilling system 50
comprising the bit body 10 having a cutter pocket 13 with a rounded
bottom. Here the bit body 10 is deployed on a drill string 52 and
connected to a top drive 58 for rotating the drill string 52 and
bit 10.
* * * * *