U.S. patent application number 12/355258 was filed with the patent office on 2010-07-22 for impregnated drill bit with diamond pins.
This patent application is currently assigned to BAKER HUGHES INCORORATED. Invention is credited to Bruce STAUFFER.
Application Number | 20100181116 12/355258 |
Document ID | / |
Family ID | 42336045 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100181116 |
Kind Code |
A1 |
STAUFFER; Bruce |
July 22, 2010 |
IMPREGNATED DRILL BIT WITH DIAMOND PINS
Abstract
A method of manufacturing a drill bit and several embodiments of
a drill bit for drilling a well in an earth formation. In one
embodiment, the drill bit comprises a diamond impregnated bit body
with one or more thermally stable pins embedded therein. More
specifically, the drill bit may include a diamond impregnated bit
body having a plurality of blades, with one or more of the blades
having a cone section, a nose section, a shoulder section, and a
gage section; a plurality of diamond impregnated cutters extending
from the blades; and one or more thermally stable polycrystalline
diamond pins embedded within, and possibly extending from, at least
some of the cutters. In some embodiments, each cutter includes an
embedded pin. Alternatively, the pin or pins may be located in the
cone, shoulder, nose, and/or gauge sections.
Inventors: |
STAUFFER; Bruce; (The
Woodlands, TX) |
Correspondence
Address: |
LOCKE LORD BISSELL & LIDDELL LLP;ATTN: IP DOCKETING
600 TRAVIS, SUITE 3400
HOUSTON
TX
77002-3095
US
|
Assignee: |
BAKER HUGHES INCORORATED
Houston
TX
|
Family ID: |
42336045 |
Appl. No.: |
12/355258 |
Filed: |
January 16, 2009 |
Current U.S.
Class: |
175/426 ;
51/295 |
Current CPC
Class: |
B24D 3/06 20130101; E21B
10/5673 20130101 |
Class at
Publication: |
175/426 ;
51/295 |
International
Class: |
E21B 10/56 20060101
E21B010/56; E21B 10/55 20060101 E21B010/55; E21B 10/46 20060101
E21B010/46; B24D 11/00 20060101 B24D011/00 |
Claims
1. A method of manufacturing a drill bit having a diamond
impregnated bit body and a plurality of cutters, such as for
drilling into an earth formation, the method comprising the steps
of: preparing a mold having at least one cutter cavity for the
cutters; placing at least one diamond pin in the cutter cavity; and
forming the cutter around the pin, such that the pin is embedded
within the cutter.
2. The method as set forth in claim 1, wherein the mold includes a
body cavity for a bit body, a plurality of blade cavities for a
plurality of blades extending beyond the bit body, and a plurality
of cutter cavities for a plurality of cutters extending beyond the
blades.
3. The method as set forth in claim 2, wherein the placing step
includes placing a pin in each cutter cavity.
4. The method as set forth in claim 2, wherein at least some of the
blade cavities have a cone section, a nose section, a shoulder
section, and a gage section and wherein the placing step includes
placing a pin in at least one cutter cavity in the cone
section.
5. The method as set forth in claim 2, wherein at least some of the
blade cavities have a cone section, a nose section, a shoulder
section, and a gage section and wherein the placing step includes
placing a pin in at least one cutter cavity in the nose
section.
6. The method as set forth in claim 2, wherein at least some of the
blade cavities have a cone section, a nose section, a shoulder
section, and a gage section and wherein the placing step includes
placing a pin in at least one cutter cavity in the shoulder
section.
7. The method as set forth in claim 2, wherein at least some of the
cutter cavities include pin cavities, and wherein the placing step
includes placing a pin in the pin cavity such that the pin extends
beyond the cutter.
8. The method as set forth in claim 2, further including the step
of selecting a pin long enough to extend through the cutter cavity
and into the blade cavity.
9. The method as set forth in claim 1, further including the step
of selecting a pin long enough to extend through the cutter cavity
and into a bit body cavity.
10. The method as set forth in claim 1, further including the step
of designing the mold to provide more pins in high wear areas of
the bit.
11. The method as set forth in claim 1, further including the step
of designing the mold to provide an optimum pattern of pins for a
type of formation.
12. A drill bit, such as for drilling into an earth formation, the
drill bit comprising: a bit body; a plurality of cutters; and at
least one diamond pin embedded within at least one of the cutters,
wherein the pin extends both above and below the cutter.
13. The drill bit as set forth in claim 12, wherein each cutter
includes an embedded pin.
14. The drill bit as set forth in claim 12, wherein the bit body
includes a cone section, a nose section, a shoulder section, and a
gage section, and wherein the pin is located in the cone
section.
15. The drill bit as set forth in claim 12, wherein the bit body
includes a cone section, a nose section, a shoulder section, and a
gage section, and wherein the pin is located in the nose section,
and wherein there are no pins in the cone section.
16. The drill bit as set forth in claim 12, wherein the bit body
includes a cone section, a nose section, a shoulder section, and a
gage section, and wherein the pin is located in the shoulder
section, and wherein there are no pins in the cone section.
17. The drill bit as set forth in claim 12, wherein the bit body
includes a plurality of blades, at least one of the blades having a
cone section, a nose section, a shoulder section, and a gage
section, and wherein at least one cutter in the cone section
includes the pin.
18. The drill bit as set forth in claim 12, wherein the bit body
includes a plurality of blades, at least one of the blades having a
cone section, a nose section, a shoulder section, and a gage
section, and wherein at least one cutter in the nose section
includes the pin, and wherein there are no pins in the cone
section.
19. The drill bit as set forth in claim 12, wherein the bit body
includes a plurality of blades, at least one of the blades having a
cone section, a nose section, a shoulder section, and a gage
section, and wherein at least one cutter in the shoulder section
includes the pin, and wherein there are no pins in the cone
section.
20. The drill bit as set forth in claim 12, wherein the pin extends
beyond the cutter.
21. (canceled)
22. The drill bit as set forth in claim 12, wherein there are more
pins in high wear areas of the bit.
23. The drill bit as set forth in claim 12, wherein the pins form
an optimum pattern for a type of formation.
24. A drill bit, such as for drilling into an earth formation, the
drill bit comprising: a diamond impregnated bit body having a
plurality of blades, at least one of the blades having a cone
section, a nose section, a shoulder section, and a gage section; a
plurality of diamond impregnated cutters extending from the blades;
and a thermally stable polycrystalline diamond pin embedded within
at least some of the cutters in the shoulder section, wherein the
pins extend through the cutters and blades in the shoulder section,
and wherein there are no pins in the cone section.
25. The drill bit as set forth in claim 12, wherein the pins extend
through the cutters and into the bit body.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This subject matter of this application is similar to the
subject matter disclosed in U.S. patent application Ser. Nos.
12/250,443, 12/250,445, 12/250,447, and 12/250,448, all filed Oct.
13, 2008, and U.S. patent application Ser. No. 12/274,709, filed
Nov. 20, 2008. The above mentioned patent applications are
incorporated herein by specific reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO APPENDIX
[0003] Not applicable.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] The inventions disclosed and taught herein relate generally
to drill bits for drilling wells; and more specifically relate to
diamond impregnated drill bits with super-abrasive cutting elements
for drilling wells in earth formations.
[0006] 2. Description of the Related Art
[0007] U.S. Pat. No. 4,190,126 discloses a "rotary abrasive
drilling bit disclosed herein is of a construction wherein teeth
are equipped on the fore part of a bit body attached to a rotary
drill pipe, each of said teeth is composed of a plurality of chips
which are made of cemented tungsten carbide and the matrix thereof
which is soft and inferior in abrasion resistance relative to said
cutting elements or chips, each chip is shaped like a thin stick
and extends along the cutting direction of said bit body, the
matrix surrounds said chips, and in the matrix of each tooth the
chips are orderly arranged to leave a desired interspace along the
direction of radius as well as the direction of circumference of
the bit body."
[0008] U.S. Pat. No. 6,095,265 discloses "a diamond impregnated bit
with an adaptive matrix in the ribs. The ribs have at least two
different areas of metal-matrix composite impregnated with diamonds
with different wear resistance such that during boring of
formation, the areas will wear at different rates and provide fluid
flow spaces across the surface of the ribs."
[0009] U.S. Pat. No. 6,296,069 discloses a "drill bit as used in
particular in the oil well drilling field comprising a central body
(2), cutting blades (3) protruding with respect to the body (2),
both at the front of this body according to a drill direction and
at the sides of this same body (2), and cutting elements (9)
divided over an outer front surface (10) and over an outer lateral
well sizing surface (11) comprised by each blade (3), wherein there
are provided as cutting elements: in a central area (13) of the
front surface (10), on at least one blade (3): at least one
synthetic polycrystalline diamond compact cutting disc (12), and in
a remaining area (14) of the front surface (10) of this blade,
situated beyond said central area (13) with respect to the rotation
axis, and on the other blades: thermally stable synthetic diamonds
and/or impregnated diamond particles."
[0010] U.S. Pat. No. 6,510,906 discloses a "drill bit employing a
plurality of discrete, post-like diamond grit impregnated cutting
structures extending upwardly from abrasive particulate-impregnated
blades defining a plurality of fluid passages therebetween on the
bit face. PDC cutters with faces oriented in the general direction
of bit rotation are placed in the cone of the bit, which is
relatively shallow, to promote enhanced drilling efficiency through
softer, non-abrasive formations. A plurality of ports, configured
to receive nozzles therein are employed for improved drilling fluid
flow and distribution. The blades may extend radially in a linear
fashion, or be curved and spiral outwardly to the gage to provide
increased blade length and enhanced cutting structure
redundancy."
[0011] U.S. Pat. No. 6,843,333 discloses a "drill bit employing a
plurality of discrete, post-like, abrasive, particulate-impregnated
cutting structures extending upwardly from abrasive,
particulate-impregnated blades defining a plurality of fluid
passages therebetween on the bit face. Additional cutting elements
may be placed in the cone of the bit surrounding the centerline
thereof. The blades may extend radially in a linear fashion, or be
curved and spiral outwardly to the gage to provide increased blade
length and enhanced cutting structure redundancy. Additionally,
discrete protrusions may extend outwardly from at least some of the
plurality of cutting structures. The discrete protrusions may be
formed of a thermally stable diamond product and may exhibit a
generally triangular cross-sectional geometry relative to the
direction of intended bit rotation."
[0012] U.S. Pat. No. 7,234,550 discloses an "insert for a drill bit
which includes a diamond impregnated body, and a shearing portion
disposed on said body is shown. In addition, a method for forming a
drill bit that includes (a) forming a shearing portion on a
diamond-impregnated insert body to form a cutting insert, (b)
forming a bit body having a plurality of sockets sized to receive a
plurality of the cutting inserts, and (c) mounting the plurality of
cutting inserts in the bit body and affixing the plurality of
cutting inserts to the bit body; wherein steps (a) (c) are carried
out such that a total exposure of the diamond-impregnated insert to
temperatures above 1000.degree. F. is greater than a total exposure
of the shearing portion to temperatures above 1000.degree. F."
[0013] Two Industrial Diamond Review (IDR) articles, one dated
March 1992, and the other dated June 1993, disclose thermally
stable pins (TSPs) in a diamond impregnated core bit.
[0014] European Patent No. 0391683 teaches "a rotatable crown for a
rotary drill".
[0015] The inventions disclosed and taught herein are directed to
an improved diamond impregnated drill bit with super-abrasive
cutting elements for drilling wells in earth formations.
BRIEF SUMMARY OF THE INVENTION
[0016] The invention relates to a method of manufacturing a drill
bit and several embodiments of a drill bit for drilling a well in
an earth formation. In one embodiment, the drill bit comprises a
diamond impregnated bit body with one or more thermally stable pins
embedded therein. More specifically, the drill bit may include a
diamond impregnated bit body having a plurality of blades, with one
or more of the blades having a cone section, a nose section, a
shoulder section, and a gage section; a plurality of diamond
impregnated cutters extending from the blades; and one or more
thermally stable polycrystalline diamond pins embedded within, and
possibly extending from, at least some of the cutters. In some
embodiments, each cutter includes an embedded pin. Alternatively,
the pin or pins may be located in the cone, shoulder, nose, and/or
gauge sections.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0017] FIG. 1 comprises an inverted perspective view of a first
embodiment of a bit of the present invention;
[0018] FIG. 2 is a top elevation of the bit of FIG. 1 after
testing, showing wear of discrete cutting structures and PDC
cutters;
[0019] FIG. 3 is an enlarged perspective view of an exemplary
cutting structure embodying certain aspects of the present
inventions;
[0020] FIG. 4 is an enlarged perspective view of another exemplary
cutting structure embodying certain aspects of the present
inventions;
[0021] FIG. 5 is a partial cut-away view of a mold embodying
certain aspects of the present inventions; and
[0022] FIG. 6 is another partial cut-away view of a mold embodying
certain aspects of the present inventions.
DETAILED DESCRIPTION
[0023] The Figures described above and the written description of
specific structures and functions below are not presented to limit
the scope of what Applicants have invented or the scope of the
appended claims. Rather, the Figures and written description are
provided to teach any person skilled in the art to make and use the
inventions for which patent protection is sought. Those skilled in
the art will appreciate that not all features of a commercial
embodiment of the inventions are described or shown for the sake of
clarity and understanding. Persons of skill in this art will also
appreciate that the development of an actual commercial embodiment
incorporating aspects of the present inventions will require
numerous implementation-specific decisions to achieve the
developer's ultimate goal for the commercial embodiment. Such
implementation-specific decisions may include, and likely are not
limited to, compliance with system-related, business-related,
government-related and other constraints, which may vary by
specific implementation, location and from time to time. While a
developer's efforts might be complex and time-consuming in an
absolute sense, such efforts would be, nevertheless, a routine
undertaking for those of skill this art having benefit of this
disclosure. It must be understood that the inventions disclosed and
taught herein are susceptible to numerous and various modifications
and alternative forms. Lastly, the use of a singular term, such as,
but not limited to, "a," is not intended as limiting of the number
of items. Also, the use of relational terms, such as, but not
limited to, "top," "bottom," "left," "right," "upper," "lower,"
"down," "up," "side," and the like are used in the written
description for clarity in specific reference to the Figures and
are not intended to limit the scope of the invention or the
appended claims.
[0024] Particular embodiments of the invention may be described
below with reference to block diagrams and/or operational
illustrations of methods. In some alternate implementations, the
functions/actions/structures noted in the figures may occur out of
the order noted in the block diagrams and/or operational
illustrations. For example, two operations shown as occurring in
succession, in fact, may be executed substantially concurrently or
the operations may be executed in the reverse order, depending upon
the functionality/acts/structure involved.
[0025] Applicants have created both a method of manufacturing a
drill bit and several embodiments of a drill bit for drilling a
well in an earth formation. In one embodiment, the drill bit
comprises a diamond impregnated bit body with one or more thermally
stable pins embedded therein. More specifically, the drill bit may
include a diamond impregnated bit body having a plurality of
blades, with one or more of the blades having a cone section, a
nose section, a shoulder section, and a gage section; a plurality
of diamond impregnated cutters extending from the blades; and one
or more thermally stable polycrystalline diamond pins embedded
within, and possibly extending from, at least some of the cutters.
In some embodiments, each cutter includes an embedded pin.
Alternatively, the pin or pins may be located in the cone,
shoulder, nose, and/or gauge sections.
[0026] The present invention includes both a method manufacturing a
drill bit and several embodiments of a drill bit 10 for drilling a
well in an earth formation. The bit 10 may be similar to those
disclosed in U.S. Pat. No. 6,843,333, the disclosure of which is
incorporated herein by specific reference in its entirety.
Referring now to FIGS. 1 and 2, a first embodiment of the bit 10 of
the present invention is depicted. In FIG. 1, the bit 10 is shown
inverted from its normal face-down operating orientation for
clarity. The bit 10 is, in one embodiment, 81/2'' in diameter and
includes a matrix-type bit body 12 having a shank 14 for connection
to a drill string (not shown) extending therefrom opposite a bit
face 16. A plurality of blades 18 extends generally radially
outwardly in linear fashion to gage pads 20 defining junk slots 22
therebetween.
[0027] The bit 10 may include a plurality of discrete cutters. In
one embodiment, the cutters include impregnated cutting structures
24 comprising posts extending upwardly from the blades 18 on the
bit face 16. The cutting structures 24 may be formed as an integral
part of the matrix-type blades 18 projecting from the matrix-type
bit body 12 by hand-packing diamond grit-impregnated matrix
material in mold cavities on the interior of a bit mold defining
locations of the cutting structures 24 and blades 18. Thus, each
blade 18 and associated cutting structure 24 may define a unitary
structure. It is noted that the cutting structures 24 may be placed
directly on the bit face 16, dispensing with the blades. It is also
noted that, while discussed in terms of being integrally formed
with the bit 10, the cutting structures 24 may be formed as
discrete individual segments, such as by hot isostatic pressing,
and subsequently brazed or furnaced onto the bit 10.
[0028] The discrete cutting structures 24 may be mutually separate
from each other to promote drilling fluid flow therearound for
enhanced cooling and clearing of formation material removed by the
diamond grit. The discrete cutting structures 24 may be generally
of a round or circular transverse cross-section at their
substantially flat, outermost ends, but become more oval with
decreasing distance from the face of the blades 18 and thus provide
wider or more elongated (in the direction of bit rotation) bases
for greater strength and durability. As the discrete cutting
structures 24 wear, the exposed cross-section of the posts
increases, providing progressively increasing contact area for the
diamond grit with the formation material. As the cutting structures
wear down, the bit 10 takes on the configuration of a heavier-set
bit more adept at penetrating harder, more abrasive formations.
Even if discrete cutting structures 24 wear completely away, the
diamond-impregnated blades 18 will provide some cutting action,
reducing any possibility of ring-out and having to pull the bit
10.
[0029] While the cutting structures 24 are illustrated as
exhibiting posts of circular outer ends and oval shaped bases,
other geometries are also contemplated. For example, the outermost
ends of the cutting structures may be configured as ovals having a
major diameter and a minor diameter. The base portion adjacent the
blade 18 might also be oval, having a major and a minor diameter,
wherein the base has a larger minor diameter than the outermost end
of the cutting structure 24. As the cutting structure 24 wears
towards the blade 18, the minor diameter increases, resulting in a
larger surface area. Furthermore, the ends of the cutting
structures 24 need not be flat, but may employ sloped geometries.
In other words, the cutting structures 24 may change cross-sections
at multiple intervals, and tip geometry may be separate from the
general cross-section of the cutting structure. Other shapes or
geometries may be configured similarly. It is also noted that the
spacing between individual cutting structures 24, as well as the
magnitude of the taper from the outermost ends to the blades 18,
may be varied to change the overall aggressiveness of the bit 10 or
to change the rate at which the bit is transformed from a light-set
bit to a heavy-set bit during operation. It is further contemplated
that one or more of such cutting structures 24 may be formed to
have substantially constant cross-sections if so desired depending
on the anticipated application of the bit 10.
[0030] The discrete cutting structures 24, blades 18, and/or bit
body 12 may comprise a synthetic diamond grit, such as, for
example, DSN-47 Synthetic diamond grit, commercially available from
DeBeers of Shannon, Ireland, which has demonstrated toughness
superior to natural diamond grit. The tungsten carbide matrix
material with which the diamond grit is mixed to form discrete
cutting structures 24 and supporting blades 18 may desirably
include a fine grain carbide, such as, for example, DM2001 powder
commercially available from Kennametal Inc., of Latrobe, Pa. Such a
carbide powder, when infiltrated, provides increased exposure of
the diamond grit particles in comparison to conventional matrix
materials due to its relatively soft, abradable nature. The base 30
of each blade 18 may desirably be formed of, for example, a more
durable 121 matrix material, obtained from Firth MPD of Houston,
Tex. Use of the more durable material in this region helps to
prevent ring-out even if all of the discrete cutting structures 24
are abraded away and the majority of each blade 18 is worn.
[0031] It is noted, however, that alternative particulate abrasive
materials may be suitably substituted for those discussed above.
For example, the discrete cutting structures 24 may include natural
diamond grit, or a combination of synthetic and natural diamond
grit. Alternatively, the cutting structures may include synthetic
diamond pins 28. Additionally, the particulate abrasive material
may be coated with a single layer or multiple layers of a
refractory material, as known in the art and disclosed in U.S. Pat.
Nos. 4,943,488 and 5,049,164, the disclosures of each of which are
hereby incorporated herein by reference in their entirety. Such
refractory materials may include, for example, a refractory metal,
a refractory metal carbide or a refractory metal oxide. In one
embodiment, the coating may exhibit a thickness of approximately 1
to 10 microns. In another embodiment, the coating may exhibit a
thickness of approximately 2 to 6 microns. In yet another
embodiment, the coating may exhibit a thickness of less than 1
micron.
[0032] Alternatively, or additionally, one or more of the blades 18
may carry cutters in the form of polycrystalline diamond compact
(PDC) cutting elements 26, in conventional orientations, with
cutting faces oriented generally facing the direction of bit
rotation. In one embodiment, the PDC cutting elements 26 are
located within the cone portion 34 of the bit face 16. The cone
portion 34, best viewed with reference to FIG. 1, is the portion of
the bit face 16 wherein the profile is defined as a generally
cone-shaped section about the centerline of intended rotation of
the drill bit 10. Alternatively, or additionally, the PDC cutting
elements 26 may be located across the blades 18 and elsewhere on
the bit 10.
[0033] The PDC cutting elements 26 may comprise cutters having a
PDC jacket or sheath extending contiguously with, and to the rear
of, the PDC cutting face and over a supporting substrate. For
example, a cutter of this type is offered by Hughes Christensen
Company, a wholly owned subsidiary of the assignee of the present
invention, as NIAGARA.TM. cutters. Such cutters are further
described in U.S. Pat. No. 6,401,844, the disclosure of which is
incorporated herein by specific reference in its entirety. This
cutter design provides enhanced abrasion resistance to the hard
and/or abrasive formations typically drilled by impregnated bits,
in combination with enhanced performance, or rate of penetration
(ROP), in softer, nonabrasive formation layers interbedded with
such hard formations. It is noted, however, that alternative PDC
cutter designs may be implemented. For example, the PDC cutting
elements 26 may be configured of various shapes, sizes, or
materials as known by those of skill in the art. Also, other types
of cutting elements may be formed within the cone portion 34 of,
and elsewhere across, the bit 10 depending on the anticipated
application of the bit 10. For example, the cutting elements 26 may
include cutters formed of thermally stable polycrystalline diamond
product (TSP), natural diamond material, or impregnated
diamond.
[0034] While PDC cutting elements, such as those discussed above,
are used in one embodiment, other cutters may be used alternatively
and/or additionally. For example, cutters made of thermally stable
polycrystalline (TSP) diamond, in triangular, pin, and/or circular
configuration, cubic boron nitride (CBN), and/or other
superabrasive materials may be used. In some embodiments, even
simple carbide cutters may be used.
[0035] An exemplary cutting structure 24 of the present invention,
as shown in FIG. 3 and FIG. 4, includes a TSP pin 28 of circular,
rectangular or other polygon, oval, truncated circular, triangular,
or other suitable cross-section. The TSP pin 28, exhibiting a
circular cross-section and an overall cylindrical configuration, or
shape, is suitable for a wide variety of drill bits and drilling
applications. The TSP pins 28 are preferably embedded within the
cutting structures 24. The TSP pins 28 may extend from the cutting
structures 24. Additionally, or alternatively, the pins 28 may be
embedded within, and may extend from, the blades 18 and/or bit body
12 themselves, with or without the cutters and/or blades 18. Thus,
the TSP pins 28 may extend from and/or through the cutters, blades
18, and/or bit body 12. As a result, as the TSP pins 28 retard wear
of the cutters, blades 18, and/or bit body 12. Furthermore, the TSP
pins 28 may stand out from the cutters, blades 18, and/or bit body
12, thereby giving higher point loading, before and/or after wear
of the cutters, blades 18, and/or bit body 12. In any case, the TSP
pins 28 may make the cutters, blades 18, and/or bit body 12 more
aggressive, thereby increasing ROP and/or decreasing the specific
energy required.
[0036] As shown in FIG. 5 and FIG. 6, the drill bit 10 may be
manufactured using a prepared mold 50. The mold 50 preferably has a
bit body cavity 52 and may have one or more blade cavities 54. The
mold 50 may also have a plurality of cutter cavities 56 extending
from the blade cavities 54 and/or bit body cavity 52, in cases
where the cutters are to be integrally formed with the bit body 12
and/or blades 18. In cases where the cutters are to be formed
separately, the mold 50 may only include one or more cutter
cavities 56. In cases where the blades 18 are to be formed
separately, the mold 50 may include a plurality of cutter cavities
56 extending from one or more blade cavities 54. Finally, in cases
where the pins 28 are to extend beyond the cutters, blades 18,
and/or bit body 12, the mold 50 may include one or more pin
cavities 58.
[0037] Once the mold 50 is properly prepared, the pins 28 are
placed therein. Then, a matrix material, such as a tungsten carbide
matrix and/or a diamond grit-impregnated matrix material is packed
into the mold 50. Finally, a binder material, such as liquefied
copper, is allowed to flow into the mold, thereby forming the
cutters, blades 18, and/or bit body 12.
[0038] It has been discovered that the blades 18 rarely wear
evenly. Therefore, it may be desirable to optimize the design of
the blades 18 and the distribution and/or spacing of cutting
material along the blades 18, to increase drill bit useful life and
minimize the required specific energy while maintaining an
acceptable rate of penetration and drilling efficiency. For
example, the bit 10 may be designed to have more cutters and/or
pins 28 in heavy, or high, wear areas. The bit 10 may also be
designed such that the cutters and/or pins 28 exhibit an optimum
bottom hole pattern for increasing ROP in one or more of types of
formations.
[0039] The blades 18 of modern drill bits often have three or more
sections that serve related and overlapping functions.
Specifically, each blade 18 preferably has a cone section, a nose
section, a shoulder section, and a gage section. As discussed
above, the cone section of each blade is preferably a substantially
linear section extending from near a center-line of the drill bit
10 outward. Because the cone section is nearest the center-line of
the drill bit 10, the cone section does not experience as much, or
as fast, movement relative to the earth formation. Therefore, it
has been discovered that the cone section commonly experiences less
wear than the other sections. Thus, the cone section can maintain
effective and efficient rate of penetration with less cutting
material. This can be accomplished in a number of ways. For
example, the cone section may have no or fewer cutters, cutting
structures 24, PDC cutting elements 26, and/or TSP pins 28, smaller
cutters, cutting structures 24, PDC cutting elements 26, and/or TSP
pins 28, and/or more spacing between cutters, cutting structures
24, PDC cutting elements 26, and/or TSP pins 28. The cone angle for
a PDC bit is typically 15-25.degree., although, in some
embodiments, the cone section is essentially flat, with a
substantially 0.degree. cone angle.
[0040] The nose represents the lowest point on a drill bit.
Therefore, the nose cutter is typically the leading most cutter.
The nose section is roughly defined by a nose radius. A larger nose
radius provides more area to place cutters in the nose section. The
nose section begins where the cone section ends, where the
curvature of the blade begins, and extends to the shoulder section.
More specifically, the nose section extends where the blade profile
substantially matches a circle formed by the nose radius. The nose
section experiences much more, and more rapid, relative movement
than does the cone section. Additionally, the nose section
typically takes more weight than the other sections. As such, the
nose section commonly experiences much more wear than does the cone
section. Therefore, the nose section preferably has a higher
distribution, concentration, or density of cutters, cutting
structures 24, PDC cutting elements 26, and/or TSP pins 28 with
respect to the cone section.
[0041] The shoulder section begins where the blade profile departs
from the nose radius and continues outwardly on each blade 18 to a
point where a slope of the blade is essentially completely
vertical, at the gage section. The shoulder section experiences
much more, and more rapid, relative movement than does the cone
section. Additionally, the shoulder section typically takes the
brunt of abuse from dynamic dysfunction, such as bit whirl. As
such, the shoulder section experiences much more wear than does the
cone section. The shoulder section is also a more significant
contributor to rate of penetration and drilling efficiency than the
cone section. Therefore, the shoulder section preferably has a
higher distribution, concentration, or density of cutters, cutting
structures 24, PDC cutting elements 26, and/or TSP pins 28 with
respect to the cone section. Depending on application, the nose
section or the shoulder section may experience the most wear, and
therefore either the nose section or the shoulder section may have
the highest distribution, concentration, or density of cutters,
cutting structures 24, PDC cutting elements 26, and/or TSP pins
28.
[0042] The gage section begins where the shoulder section ends.
More specifically, the gage section begins where the slope of the
blade is predominantly vertical. The gage section continues
outwardly to an outer perimeter or gauge of the drill bit 10. The
gage section experiences the most, and most rapid, relative
movement with respect to the earth formation. However, at least
partially because of the high, substantially vertical, slope of the
blade 18 in the gage section, the gage section does not typically
experience as much wear as does the shoulder section and/or the
nose section. The gage section does, however, typically experience
more wear than the cone section. Therefore, the gage section
preferably has a higher distribution of cutters, cutting structures
24, PDC cutting elements 26, and/or TSP pins 28 than the cone
section, but may have a lower distribution of cutters, cutting
structures 24, PDC cutting elements 26, and/or TSP pins 28 than the
shoulder section and/or nose section.
[0043] In one embodiment, a highest concentration of the cutters,
cutting structures 24, PDC cutting elements 26, and/or TSP pins 28
occurs near the border between the shoulder section and the gage
section. Alternative embodiments may include a highest
concentration of the cutters, cutting structures 24, PDC cutting
elements 26, and/or TSP pins 28, in the shoulder section and/or the
gage section.
[0044] Upon reading this disclosure, it can be appreciated that the
design of a drill bit includes consideration of many factors, such
as the size, shape, spacing, orientation, and number of blades; the
size, shape, spacing, orientation, and number of cutters, or
cutting elements; as well as the materials of the bit body, blades,
cutting tables, and substrates. All of these factors may be
considered in light of the materials of the earth formation(s) for
which the drill bit is designed and/or matched.
[0045] The bit 10 may employ a plurality of ports 36 over the bit
face 16 to enhance fluid velocity of drilling fluid flow and better
apportion the flow over the bit face 16 and among fluid passages 38
between blades 18 and extending to junk slots 22. This enhanced
fluid velocity and apportionment helps prevent bit balling in shale
formations, for example, which phenomenon is known to significantly
retard rate of penetration (ROP). Further, in combination with the
enhanced diamond exposure of bit 10, the improved hydraulics
substantially enhances drilling through permeable sandstones.
[0046] Other and further embodiments utilizing one or more aspects
of the inventions described above can be devised without departing
from the spirit of Applicant's invention. For example, the TSP pins
28 may be embedded within the PDC cutting elements 26 as well.
Additionally, or alternatively, the cutters, such as the
impregnated cutting structures 24 and/or PDC cutting elements 26,
with or without the TSP pins 28, may be formed separately from the
bit body 12, and later secured thereto, such as by brazing.
Similarly, the TSP pins 28 may be secured to, or within, previously
formed cutters, blades 18, and/or the bit body 12. Furthermore,
one, two, three, or more TSP pins 28 may be embedded within any one
or more of the cutters. Of course, the various methods and
embodiments of the drill bit 10 can be included in combination with
each other to produce variations of the disclosed methods and
embodiments. Reading this disclosure, it can be appreciated that
there are a number of ways to impact concentrations or
distributions of cutter and/or pin volume, such as by using
differently sized, shaped, and/or spaced cutters and/or pins.
Discussion of singular elements can include plural elements and
vice-versa.
[0047] The order of steps can occur in a variety of sequences
unless otherwise specifically limited. The various steps described
herein can be combined with other steps, interlineated with the
stated steps, and/or split into multiple steps. Similarly, elements
have been described functionally and can be embodied as separate
components or can be combined into components having multiple
functions.
[0048] The inventions have been described in the context of
preferred and other embodiments and not every embodiment of the
invention has been described. Obvious modifications and alterations
to the described embodiments are available to those of ordinary
skill in the art. The disclosed and undisclosed embodiments are not
intended to limit or restrict the scope or applicability of the
invention conceived of by the Applicants, but rather, in conformity
with the patent laws, Applicants intend to fully protect all such
modifications and improvements that come within the scope or range
of equivalent of the following claims.
* * * * *