U.S. patent application number 11/747780 was filed with the patent office on 2007-11-22 for percussion drill bit and method of drilling a borehole.
This patent application is currently assigned to SMITH INTERNATIONAL, INC.. Invention is credited to Ronald G. Schmidt, Lance D. Underwood.
Application Number | 20070267226 11/747780 |
Document ID | / |
Family ID | 38710984 |
Filed Date | 2007-11-22 |
United States Patent
Application |
20070267226 |
Kind Code |
A1 |
Underwood; Lance D. ; et
al. |
November 22, 2007 |
PERCUSSION DRILL BIT AND METHOD OF DRILLING A BOREHOLE
Abstract
A percussion drill bit includes a bit body having a central axis
and a bit face. A plurality of inserts is disposed on the bit face.
A plurality of gauge row inserts is disposed on a periphery of the
bit face. At least some one of the plurality of gauge row inserts
is enhanced with a super hard material and oriented on the
periphery of the bit face at an angle between about 36 degrees and
about 40 degrees relative to the central axis of the bit body.
Inventors: |
Underwood; Lance D.;
(Cypress, TX) ; Schmidt; Ronald G.; (Tomball,
TX) |
Correspondence
Address: |
OSHA, LIANG LLP / SMITH
1221 MCKINNEY STREET
SUITE 2800
HOUSTON
TX
77010
US
|
Assignee: |
SMITH INTERNATIONAL, INC.
Houston
TX
|
Family ID: |
38710984 |
Appl. No.: |
11/747780 |
Filed: |
May 11, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60799782 |
May 11, 2006 |
|
|
|
Current U.S.
Class: |
175/418 ;
76/108.1 |
Current CPC
Class: |
E21B 10/36 20130101 |
Class at
Publication: |
175/418 ;
076/108.1 |
International
Class: |
E21B 10/36 20060101
E21B010/36 |
Claims
1. A percussion drill bit, comprising: a bit body having a central
axis; a bit face; a plurality of inserts disposed on the bit face a
plurality of gauge row inserts disposed on a periphery of the bit
face, wherein at least one of the plurality of gauge row inserts is
enhanced with a super hard material and oriented on the periphery
of said bit face at an angle between about 36 degrees and about 40
degrees relative to the central axis of the bit body.
2. The percussion drill bit of claim 1, wherein at least one of the
plurality of gauge row inserts is bullet-shaped.
3. The percussion drill bit of claim 1, wherein at least one of the
plurality of gauge row inserts is semi-spherical.
4. A method of designing a percussion drill bit comprising a bit
body having a central axis and a bit face, the method comprising:
modeling a gauge row insert comprising a wear pattern; performing
finite element analysis ("FEA") on the modeled gauge row insert,
wherein the modeled gauge row insert is oriented at a first angle
relative to the central axis of the bit body; repeating the
performed FEA with the modeled gauge row insert at a second angle
relative to the central axis of the bit body; selecting an angle
for a plurality of gauge row inserts from the performed FEA.
5. The method of claim 4, wherein the wear pattern is a cat eye
pattern.
6. The method of claim 4, wherein the first angle and the second
angle are between about 36 degrees and about 40 degrees relative to
the central axis of the bit body.
7. A percussion drill bit designed using the method of claim 4.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This applications claims benefit, under 35 U.S.C. .sctn.
119, of U.S. Provisional Application Ser. No. 60/799,782 filed on
May 11, 2006 and entitled "Percussion Drill Bit and Method of
Drilling a Borehole" in the name of Lance Underwood and Ronald
Schmidt, and incorporated herein by reference in its entirety.
BACKGROUND
[0002] The disclosure herein generally relates to earth boring bits
used to drill a borehole for applications including the recovery of
oil, gas or minerals, mining, blast holes, water wells and
construction projects. More particularly, the disclosure relates to
percussion hammer drill bits. In percussion hammer drilling
operations, the bit impacts the earth in a cyclic fashion while
simultaneously rotating. In such operations, the mechanism for
penetrating the earth is of an impacting nature rather than
shearing. A typical percussion drill bit comprises a drill body,
means at one end of the drill body for connecting the bit to a
percussive unit such as a down hole hammer, and at the other end, a
bit face including a plurality of inserts for impacting and
fracturing earthen formations.
[0003] Inserts are typically disposed on various portions of the
bit face. For example, in FIG. 3, inserts are shown disposed on the
central portion 19 of the bit face 14 in the proximity of the
central axis 13 of the bit 10, and inserts 20, 22 are disposed in
numerous circumferential rows on the bit face 14, such as a first
row 72, second row 74, third row 76 and gauge row 70. The term
"gauge row" as used herein refers to the row 70 extending around or
adjacent, the periphery, or edge, 15 of the bit face 14. Gauge row
inserts 20 are positioned around the periphery of gauge row 70. The
bit face 14 also included one or more fluid flow openings 16 and
flow channels 18 for allowing the flow of circulation fluid (not
shown) from within the bit 10 to the exterior 44 of the bit 10.
[0004] An example of a typical hammer bit connected to a rotatable
drill string is described in U.S. Pat. No. 4,932,483, incorporated
herein by reference in its entirety. The down hole hammer comprises
a top sub and a drill bit separated by a tubular housing
incorporating a piston chamber there between. A feed tube is
mounted to the top sub and extends concentrically into the piston
chamber. A piston is slideably received within the housing and over
the feed tube. Fluid porting is provided in the feed tube and the
piston to sequentially admit fluid in a first space between the
piston and top sub to drive the piston towards the drill bit
support and to a second space between the piston and the drill bit
support to drive the piston towards the top sub.
[0005] Rotary motion is provided to the hammer assembly and drill
bit by the attached drill string powered by a rotary table
typically mounted on the rig platform. The drill bit is rotated
through engagement of a series of splines on the bit and driver sub
that allow axial sliding between the components but do not allow
significant rotational displacement between the hammer assembly and
bit.
[0006] The gauge row inserts typically comprise a cemented carbide
body having a rear mounting portion embedded in the bit head and a
front end protruding from the bit head. A super hard material, such
as polycrystalline diamond layer, is provided on the protruding end
of the carbide body, the material having an end edge disposed in
the vicinity of the maximum diameter of the insert.
[0007] Known drill bits that are provided with gauge inserts
enhanced with a super hard material often have a disadvantage in
that premature failures occur due to fatigue or chipping of the
super hard material. A reason for the failure is that the point of
contact between the wall of the bore and the gauge insert is close
to, or on, the rear edge area of the super hard material coating.
The coating is very thin at that area and thus has a comparatively
poor resistance to wear. The known drill bits more or less drill
the bore diameter with the thinnest part of the gauge insert since
their gauge inserts are inclined by about 35 degrees. Other know
bits, such as those described in U.S. Pat. No. 5,575,342 to
Hedlund, disclose inserts that are inclined by about 41 degrees to
about 51 degrees, and preferably about 45 degrees. While angling
these inserts with a 41 to 51 degree range increase the distance
between the rear edge of the super hard material coating and the
borehole, the increased angle results in increased stresses on the
gauge row inserts resulting in premature wear and failure.
[0008] Different places on the bit head may see different
conditions during. A need exists for a drill bit with inserts at
different orientations on the bit head to better match the varying
conditions or applications of different places on the bit head.
[0009] The embodiments of the present disclosure described herein
provide opportunities for improvement in percussion bit service
life and rate of penetration. These and various other
characteristics and advantages will be readily apparent to those
skilled in the art upon reading the following detailed description
of the preferred embodiments of the disclosure, and by referring to
the accompanying drawings.
SUMMARY OF THE DISCLOSURE
[0010] In one aspect of the present disclosure, a percussion drill
bit for percussive drilling in a formation is provided that
includes a bit body having a central axis and a bit face. A
plurality of inserts is disposed on the bit face. A plurality of
gauge row inserts is disposed on a periphery of the bit face. At
least some one of the plurality of gauge row inserts is enhanced
with a super hard material and oriented on the periphery of the bit
face at an angle between about 36 degrees and about 40 degrees
relative to the central axis of the bit body.
[0011] In another aspect of the present disclosure, a method of
designing a percussion drill bit including a bit body having a
central axis and a bit face is provided. The method includes
modeling a gauge row insert comprising a wear pattern, performing
finite element analysis ("FEA") on the modeled gauge row insert,
wherein the modeled gauge row insert is oriented at a first angle
relative to the central axis of the bit body, repeating the
performed FEA with the modeled gauge row insert at a second angle
relative to the central axis of the bit body, and selecting an
angle for a plurality of gauge row inserts from the performed
FEA.
[0012] Other aspects and advantages of the disclosure will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a more detailed description of the preferred
embodiments, reference will now be made to the accompanying
drawings, wherein:
[0014] FIG. 1 is a cross-section of a percussion hammer drilling
assembly;
[0015] FIG. 2 is an elevational view of a percussion drill bit;
[0016] FIG. 3 shows a front view of a percussion drill bit.
[0017] FIG. 4A shows a sectional view of a percussion hammer bit
according to the present disclosure.
[0018] FIG. 4B shows a sectional view of a gauge insert according
to the present disclosure, in relation to a borehole wall;
[0019] FIG. 5 shows a table with calculated stresses exerted on a
gauge row insert in relation to the inserts orientation according
to angle A; and
[0020] FIG. 6 is a graphical representation of the data shown in
FIG. 5.
[0021] FIG. 7 is a finite element analysis of a gauge row insert,
illustrating areas of stress on the insert after it has begun to
wear.
DETAILED DESCRIPTION
[0022] Referring first to FIG. 1, a cross-section of a typical
percussion drilling assembly 200 is attached to a drill string 210.
Assembly 200 comprises a top sub 220 threadably connected to a case
230, which is threadably connected to a driver sub 240. A bit 10 is
slideably engaged with driver sub 240, and a retainer sleeve 250 is
disposed between case 230 and bit 10. Top sub 220 further comprises
a check valve 225 and a feed tube 235 that extends from check valve
225 to a piston 245 that is slideably engaged with a guide sleeve
255.
[0023] During operation, drill string 210 rotates, thereby rotating
percussion drilling assembly 200. In addition, piston 245 travels
back and forth in an axial direction so that it cyclically impacts
bit 10. A series of engaged splines 265 on bit 10 and driver sub
240 allow bit 10 to slide axially relative to driver sub 240 while
also allowing driver sub 240 to rotate bit 10. As described
previously, this allows the cutting elements or inserts 20, 22 (not
shown) of bit 10 to be "indexed" to fresh rock formations during
each impact of bit 260, thereby improving the efficiency of the
drilling operation.
[0024] Referring now to FIG. 2, a percussion bit 10 for
earth-boring applications comprises a body 90 with a drill string
end 12 (nearest a drill string, not shown) and a bit face 14. A
plurality of splines 30 are disposed on body 90 between a threaded
portion 40 and a recessed portion 50. Body 90 further comprises a
collar 60 near drill string end 12 and a flared portion 70 near bit
face 14.
[0025] In FIG. 3 there is shown a top view of the bit face 14 of a
drill bit 10 according to the present disclosure, the bit being
generally symmetrical about its central axis 13. Provided in a bit
face 14 of the drill body 90 is a number of inserts. The inserts
are made of cemented carbide and secured into the face of the bit.
A number of gauge row inserts 20 is positioned at the periphery of
the bit 10, the radially outer portions of which define the
diameter of the bit and thus the diameter of the bore being
drilled.
[0026] As shown in FIG. 4A, the gauge row inserts 20 are tilted in
such a way, that a longitudinal center line (center axis) 77 of
each insert 20 diverges by an angle A from the central axis 13 of
the drill bit 10 in a forward direction of the bit. Several gauge
row inserts 20 may be embedded in the bit face 14. Each insert 20
comprises a cemented carbide body having a cylindrical grip or
mounting portion 71 embedded in the drill body and a front end
protruding from the drill body. A super hard material, such as a
polycrystalline diamond layer 72 is provided on the front end of
the carbide body to define the cutting end of the insert 20. As
shown in FIG. 4B, the layer 72 has a rear edge 75 substantially
lying in a plane P. The plane P preferably forming an acute angle
with the center axis 13, that angle being equal to the
above-mentioned angle A. The edge 75 is disposed preferably at or
in the vicinity of the maximum diameter of the insert. The central
axis 13 of the drill bit 10 and the longitudinal center line 17 of
the inserts 20 define the angle A there between.
[0027] When calculating stress on a new insert, stresses will
generally be linear with respect to center line 17; however, once
an insert begins to wear, points of higher stress are observed. To
predict these stresses, in one embodiment, a "cat eye" wear pattern
is modeled on the insert for the percussion drill bit. After
modeling the worn insert, finite element analysis ("FEA") is
performed on the worn insert to determine stresses. The FEA
performed by the present inventors on the worn insert revealed that
the relationship between angle A and the stress is nonlinear,
unlike the linear relationship between stress and angle A for the
new insert. Particularly, the point of highest stress will occur
along the bottom of the cat eye wear pattern as shown in FIG. 7.
FIG. 5 displays the highest calculated stress once wear begins to
occur on the inserts depending upon the orientation of inserts 20
in relation to angle A. For example, when angle A is 30 degrees,
the stress on insert 20 is calculated to be 9,639 psi. When angle A
is 42 degrees, the stress on insert 20 is calculated to be 11,021
psi. When angle A is 38 degrees, stress on insert 20 is calculated
to be 8,783 psi. FIG. 6 illustrates the corresponding stress in psi
relative to angle A in a graphical manner, illustrating the
nonlinear calculated stresses on inserts, once wear has begun.
[0028] In a preferred embodiment, the angle A is in the range of at
least 36 degrees to about 40 degrees, in order to space the edge 75
by a distance L from the wall of the bore during drilling. More
preferably, the angle A is about 37 degrees to 39 degree and most
preferably is about 38 degrees. The distance L is at least 0.020
inches, and more preferably greater than 0.025 inches.
[0029] The present disclosure further relates to a method of
maintaining the diameter of a drill bit during percussive drilling
of a bore in a rock material. The method comprises the following
steps: providing a drill bit having the geometry described above,
connecting the bit to a percussive unit and drilling a bore, while
spacing the rear edge of the diamond layers of the gauge inserts
from the wall of the bore during drilling so as to maximize the
duration of the life of the bit.
[0030] The disclosure can be varied freely within the scope of the
appended claims. For example the shape of the cutting end of the
insert can be semi-spherical or bullet-shaped.
[0031] Although the present disclosure has been described in
connection with a limited number of embodiments, it will be
appreciated by those skilled in the art that additions, deletions,
modifications, and substitutions not specifically described may be
made without departing from the spirit and scope of the disclosure
as defined in the appended claims.
[0032] While various preferred embodiments of the present
disclosure have been shown and described, modifications thereof can
be made by one skilled in the art without departing from the spirit
and teachings of the disclosure. The embodiments herein are
exemplary only, and are not limiting. Many variations and
modifications of the methods and apparatuses disclosed herein are
possible and within the scope of the disclosure. Accordingly, the
scope of protection is not limited by the description set out
above, but is only limited by the claims which follow, that scope
including all equivalents of the subject matter of the claims.
* * * * *