U.S. patent application number 14/427978 was filed with the patent office on 2015-08-20 for downhole mills and improved cutting structures.
This patent application is currently assigned to National Oilwell DHT, L.P.. The applicant listed for this patent is NATIONAL OILWELL DHT, L.P., Harold A. SRESHTA, Jiinjen Albert SUE, Charles Leonard WRIGHT, II. Invention is credited to Harold A. Sreshta, Jiinjen Albert Sue, Charles Leonard Wright, II.
Application Number | 20150233188 14/427978 |
Document ID | / |
Family ID | 49322734 |
Filed Date | 2015-08-20 |
United States Patent
Application |
20150233188 |
Kind Code |
A1 |
Wright, II; Charles Leonard ;
et al. |
August 20, 2015 |
Downhole Mills and Improved Cutting Structures
Abstract
A drill bit for cutting through a downhole metal structure
includes a bit body having a central axis and a bit face. The bit
body is configured to rotate about the central axis in a cutting
direction. In addition, the bit includes a cutting structure
disposed on the bit face. The cutting structure includes a
plurality of circumferentially spaced blades and a plurality of
primary cutter elements mounted to each blade. Each primary cutter
element has a forward-facing primary cutting face. Each primary
cutter element is made of a whisker ceramic composite.
Inventors: |
Wright, II; Charles Leonard;
(Spring, TX) ; Sreshta; Harold A.; (Conroe,
TX) ; Sue; Jiinjen Albert; (The Woodlands,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WRIGHT, II; Charles Leonard
SRESHTA; Harold A.
SUE; Jiinjen Albert
NATIONAL OILWELL DHT, L.P. |
Spring
Conroe |
TX
TX |
US
US
US
US |
|
|
Assignee: |
National Oilwell DHT, L.P.
Conroe
TX
|
Family ID: |
49322734 |
Appl. No.: |
14/427978 |
Filed: |
September 25, 2013 |
PCT Filed: |
September 25, 2013 |
PCT NO: |
PCT/US2013/061556 |
371 Date: |
March 12, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61705271 |
Sep 25, 2012 |
|
|
|
Current U.S.
Class: |
175/62 ;
175/431 |
Current CPC
Class: |
E21B 10/006 20130101;
C04B 35/488 20130101; E21B 10/55 20130101; E21B 7/046 20130101;
C04B 2235/5244 20130101; C04B 2235/5276 20130101; E21B 10/43
20130101; E21B 29/06 20130101; C04B 35/117 20130101; E21B 10/46
20130101; E21B 10/5735 20130101; C04B 35/803 20130101 |
International
Class: |
E21B 10/573 20060101
E21B010/573; E21B 7/04 20060101 E21B007/04; E21B 10/43 20060101
E21B010/43 |
Claims
1. A drill bit for cutting through a downhole metal structure, the
bit comprising: a bit body having a central axis and a bit face,
wherein the bit body is configured to rotate about the central axis
in a cutting direction; a cutting structure disposed on the bit
face, wherein the cutting structure includes a plurality of
circumferentially spaced blades, a plurality of primary cutter
elements mounted to each blade, and a plurality of secondary cutter
elements mounted to each blade, wherein the primary cutter elements
on each blade lead the secondary cutter elements on the same blade
relative to the cutting direction, wherein each primary cutter
element has a forward-facing primary cutting face and each
secondary cutter element has a forward-facing secondary cutting
face; wherein each primary cutter element has an extension height
that is greater than an extension height of each secondary cutter
element; wherein each secondary cutter element comprises a
substrate and an ultrahard table mounted to the substrate; wherein
each primary cutter element is made of a whisker ceramic composite;
wherein the whisker ceramic composite is configured to cut the
downhole metal structure and the ultrahard table is configured to
cut a subterranean formation adjacent the downhole metal
structure.
2. (canceled)
3. The drill bit of claim 1, wherein the primary cutter elements on
each blade are arranged in a row extending along the blade; and
wherein the secondary cutter elements on each blade are arranged in
a row extending along the blade.
4. (canceled)
5. (canceled)
6. The drill bit of claim 1, wherein each primary cutter element is
made of a ceramic matrix and a plurality of silicon-carbide
whiskers distributed throughout the ceramic matrix.
7. The drill bit of claim 6, wherein the ceramic matrix is an
aluminum-oxide or zirconium oxide.
8. The drill bit of claim 1, wherein each primary cutter element is
brazed to the corresponding blade or pre-cast with the bit
body.
9. The drill bit of claim 1, wherein each primary cutter element is
secured within a sleeve by an interference fit, and wherein each
sleeve is brazed to the corresponding blade.
10. A cutting device for milling a downhole metal structure, the
cutting device comprising: a body having a central axis, a first
end coupled to a pin, and a second end defining an annular cutting
face; a plurality of circumferentially-spaced cutter elements
mounted to the cutting face, wherein each cutter element comprises
a whisker ceramic composite.
11. The cutting device of claim 10, wherein each cutter elements
has a cylindrical or rectangular geometry.
12. The cutting device of claim 10, wherein the body includes a
throughbore extending axially therethrough from the first end to
the second end.
13. The cutting device of claim 10, wherein each cutter element is
made of a ceramic matrix and a plurality of silicon-carbide
whiskers distributed throughout the ceramic matrix.
14. The cutting device of claim 13, wherein the ceramic matrix is
an aluminum-oxide or zirconium oxide.
15. The cutting device of claim 10, wherein each cutter element has
a base portion secured to the body and a cutting portion with a
cutting surface, wherein the cutting surface of each cutter element
includes a plurality of steps.
16. The cutting device of claim 15, wherein each cutter element is
disposed at a backrake angle between 5.degree. and 20.degree..
17. The cutting device of claim 10, wherein each cutter element has
a base portion secured to the body and a cutting portion with a
cutting surface, wherein the cutting surface of each cutter element
includes a plurality of parallel teeth.
18. The cutting device of claim 10, wherein each cutter element is
brazed to the body or removably mounted to the body with a
bolt.
19. A method for sidetracking from a borehole, the method
comprising: (a) coupling a drill bit to a lower end of a
drillstring, wherein the drill bit comprises: a bit body having a
central axis and a bit face; a cutting structure disposed on the
bit face, wherein the cutting structure includes a plurality of
circumferentially spaced blades, a plurality of primary cutter
elements mounted to each blade and a plurality of secondary cutter
elements mounted to each blade, wherein the secondary cutter
elements on each blade trail the primary cutter elements on the
same blade; wherein each cutter element has an extension height and
a forward-facing cutting face, and wherein the extension height of
each primary cutter element is greater than the extension height of
each secondary cutter element; wherein the forward-facing cutting
face of each primary cutter element is made of a whisker ceramic
composite configured to engage and cut casing lining a borehole;
wherein the forward-facing cutting face of each secondary cutter
element is made of an ultrahard table mounted to a substrate,
wherein the ultrahard table is configured to engage and cut a
borehole in an earthen formation; (b) lowering the drill bit into a
borehole lined with casing; (c) rotating the bit about the central
axis in a cutting direction; (d) engaging the casing with the
cutting structure during (c); (e) milling the casing with the
primary cutter elements during (d); (f) cutting a hole through the
casing with the drill bit; (g) advancing the drill bit through the
hole in the casing; and (h) drilling a borehole in an earthen
formation with the secondary cutter elements.
20. (canceled)
21. The method of claim 19, further comprising sacrificing the
primary cutter elements during (h).
22. The drill bit of claim 1, wherein the whisker ceramic composite
of each primary cutter element comprises a ceramic matrix embedded
with a plurality of distributed fibers, wherein at least some of
the plurality of distributed fibers are oriented perpendicular to
the primary cutting face.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a 35 U.S.C. .sctn.371 national stage
application of PCT/US2013/061556 filed Sep. 25, 2013 and entitled
"Downhole Mills and Improved Cutting Structures," which claims
benefit of U.S. provisional patent application Ser. No. 61/705,271
filed Sep. 25, 2012, and entitled "Downhole Mills and Improved
Cutting Structures," both of which are hereby incorporated herein
by reference in their entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND
[0003] The invention relates generally to downhole cutting devices.
More particularly, the invention relates to mills and bits with
improved cutting structures for cutting through downhole metal
structures such as casing.
[0004] In some cases, previously drilled and cased wellbores become
non-productive. When such a wellbore becomes unusable, and there
are sufficient hydrocarbon reserves in the surrounding formation to
justify continued production, a new borehole may be drilled in the
vicinity of the existing cased borehole or alternatively, a new
borehole may be sidetracked near the bottom of a serviceable
portion of the cased borehole. Sidetracking from an existing cased
borehole can also be used to access multiple production zones from
a common wellbore.
[0005] Sidetracking is often preferred because it reduces drilling,
casing and cementing needs, as well as associated costs.
Sidetracking is typically accomplished by either milling out an
entire section of casing followed by drilling a lateral borehole
into the exposed borehole sidewall, or by milling through the side
of the casing with a mill guided by a wedge or "whipstock"
component followed by drilling a lateral borehole through the hole
in the casing.
[0006] Drilling a side tracked hole through casing made of steel is
challenging and often results in unsuccessful penetration of the
casing. In addition, if the window is improperly cut, a severely
deviated dog leg may result rendering the sidetracking operation
unusable.
[0007] One conventional approach to drilling through steel casing
for sidetracking is to employ a bit or mill including a plurality
of cutter elements. The cutter elements are typically formed of
extremely hard materials and include a layer of polycrystalline
diamond (PCD) or other superabrasive material such as cubic boron
nitride, thermally stable diamond, polycrystalline cubic boron
nitride, or ultrahard tungsten carbide. The mill is rotated and
urged against the inside of the steel casing, thereby allowing the
cutter elements to engage, penetrate, and shear small chips of the
steel casing. This process is continued until the mill completely
penetrates the steel casing.
[0008] The performance of conventional cutter elements cutting
steel typically declines over time. In particular, thermal loads
negatively impact cutter element life, and the development of wear
flats on conventional cutter elements reduces cutting efficiency
and effectiveness. Decreases in cutting performance typically
results in an increase in milling time and associated costs.
BRIEF SUMMARY OF THE DISCLOSURE
[0009] These and other needs in the art are addressed in one
embodiment by a drill bit for cutting through a downhole metal
structure. In an embodiment, the bit comprises a bit body having a
central axis and a bit face. The bit body is configured to rotate
about the central axis in a cutting direction. In addition, the bit
comprises a cutting structure disposed on the bit face. The cutting
structure includes a plurality of circumferentially spaced blades
and a plurality of primary cutter elements mounted to each blade.
Each primary cutter element has a forward-facing primary cutting
face. Each primary cutter element is made of a whisker ceramic
composite.
[0010] These and other needs in the art are addressed in another
embodiment by a cutting device for milling a downhole metal
structure. In an embodiment, the cutting device comprises a body
having a central axis, a first end coupled to a pin, and a second
end defining an annular cutting face. In addition, the cutting
device comprises a plurality of circumferentially-spaced cutter
elements mounted to the cutting face. Each cutter element comprises
a whisker ceramic composite.
[0011] These and other needs in the art are addressed in another
embodiment by a method for sidetracking from a borehole. In an
embodiment, the method comprises coupling a drill bit to a lower
end of a drillstring. The drill bit comprises a bit body having a
central axis and a bit face. The drill bit also comprises a cutting
structure disposed on the bit face. The cutting structure includes
a plurality of circumferentially spaced blades, a plurality of
primary cutter elements mounted to each blade and a plurality of
secondary cutter elements mounted to each blade. The secondary
cutter elements on each blade trail the primary cutter elements on
the same blade. Each cutter element has an extension height, and
the extension height of each primary cutter element is greater than
the extension height of each secondary cutter element. Each primary
cutter element is made of a whisker ceramic composite. In addition,
the method comprises (b) lowering the drill bit into a borehole
lined with casing. Further, the method comprises (c) rotating the
bit about the central axis in a cutting direction. Still further,
the method comprises (d) engaging the casing with the cutting
structure during (c). Moreover, the method comprises (e) milling
the casing with the primary cutter elements during (d).
[0012] Embodiments described herein comprise a combination of
features and advantages intended to address various shortcomings
associated with certain prior devices, systems, and methods. The
foregoing has outlined rather broadly the features and technical
advantages of the invention in order that the detailed description
of the invention that follows may be better understood. The various
characteristics described above, as well as other features, will be
readily apparent to those skilled in the art upon reading the
following detailed description, and by referring to the
accompanying drawings. It should be appreciated by those skilled in
the art that the conception and the specific embodiments disclosed
may be readily utilized as a basis for modifying or designing other
structures for carrying out the same purposes of the invention. It
should also be realized by those skilled in the art that such
equivalent constructions do not depart from the spirit and scope of
the invention as set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a detailed description of the preferred embodiments of
the invention, reference will now be made to the accompanying
drawings in which:
[0014] FIG. 1 is a perspective view of an embodiment of drill bit
in accordance with the principles described herein for milling a
metal structure;
[0015] FIG. 2 is an enlarged cross-sectional view of one of the
primary cutter elements of FIG. 1 illustrating the microstructure
of the whisker ceramic composite forming the primary cutter
elements of FIG. 1;
[0016] FIG. 3 is a graphical illustration of an embodiment of a
method for performing a sidetracking operation with the drill bit
of FIG. 1;
[0017] FIG. 4 is a side view of an embodiment of a cutting device
in accordance with the principles described herein for milling a
metal structure;
[0018] FIG. 5 is a partial cross-sectional view of the cutting
device of FIG. 3;
[0019] FIG. 6 is an end view of the cutting face of FIG. 3;
[0020] FIGS. 7A-7D are schematic side views of embodiments of
cutter elements in accordance with the principles described herein
comprising whisker ceramic composites and having different,
exemplary geometries; and
[0021] FIGS. 8A-8G are enlarged partial cross-sectional views of
cutting devices illustrating exemplary techniques for attaching
cutter elements comprising whisker ceramic composites thereto.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The following discussion is directed to various exemplary
embodiments. However, one skilled in the art will understand that
the examples disclosed herein have broad application, and that the
discussion of any embodiment is meant only to be exemplary of that
embodiment, and not intended to suggest that the scope of the
disclosure, including the claims, is limited to that
embodiment.
[0023] Certain terms are used throughout the following description
and claims to refer to particular features or components. As one
skilled in the art will appreciate, different persons may refer to
the same feature or component by different names. This document
does not intend to distinguish between components or features that
differ in name but not function. The drawing figures are not
necessarily to scale. Certain features and components herein may be
shown exaggerated in scale or in somewhat schematic form and some
details of conventional elements may not be shown in interest of
clarity and conciseness.
[0024] In the following discussion and in the claims, the terms
"including" and "comprising" are used in an open-ended fashion, and
thus should be interpreted to mean "including, but not limited to .
. . . " Also, the term "couple" or "couples" is intended to mean
either an indirect or direct connection. Thus, if a first device
couples to a second device, that connection may be through a direct
connection, or through an indirect connection via other devices,
components, and connections. In addition, as used herein, the terms
"axial" and "axially" generally mean along or parallel to a central
axis (e.g., central axis of a body or a port), while the terms
"radial" and "radially" generally mean perpendicular to the central
axis. For instance, an axial distance refers to a distance measured
along or parallel to the central axis, and a radial distance means
a distance measured perpendicular to the central axis.
[0025] Referring now to FIG. 1, an embodiment of a cutting device
10 for cutting or drilling through a downhole metal structure
(e.g., steel casing, a packer, etc.) is shown. In this embodiment,
device 10 is a fixed cutter bit, sometimes referred to as a drag
bit. As will be described in more detail below, cutting device 10
can also be used to drill through an earthen formation such as
immediately after cutting through casing during sidetracking
operations. Accordingly, cutting device 10 may also be referred to
as a mill or a bit. In this embodiment, cutting device 10 is a
"torpedo" style fixed cutter bit, however, embodiments described
herein are not limited to that specific type of fixed cutter
bit.
[0026] Bit 10 includes a body 12, a shank 13 and a threaded
connection or pin 14 for connecting bit 10 to a drill string (not
shown), which is employed to rotate the bit in order to drill the
metal structure. Body 12 includes a bit face 20, which supports a
cutting structure 15 generally disposed on the end of the bit 10
that is opposite pin 14. Bit 10 has a central axis 11 about which
bit 10 rotates in the cutting direction represented by arrow 18.
Body 12 may be formed in a conventional manner using powdered metal
tungsten carbide particles in a binder material to form a hard
metal cast matrix. Alternatively, the body can be machined from a
metal block, such as steel, rather than being formed from a
matrix.
[0027] Body 12 may include bores and/or passages that permitting
fluid (e.g., lubricating fluid, drilling fluid, etc.) to flow from
the drill string into bit 10, and out of drill bit 10 through ports
or nozzles disposed in bit face 20. Such bores and passages may
serve to distribute fluid around cutting structure 15 to flush away
metal cuttings during milling or formatting cuttings during
drilling through the formation, and to remove heat from bit 10.
[0028] Referring still to FIG. 1, cutting structure 15 is provided
on face 20 of bit 10 and includes a plurality of blades 16
extending along bit face 20. In this embodiment, the plurality of
blades 16 are uniformly circumferentially-spaced about the bit face
20. Blades 16 are integrally formed as part of, and extend
perpendicularly outwardly from body 12 and bit face 20. In
addition, blades 16 extend generally radially across bit face 20
and longitudinally along a portion of the periphery of bit 10. Each
blade 16 has a first or radially inner end 16a at or proximal axis
11 and a second or radially outer end 16b opposite end 16a proximal
shank 13. Blades 16 are separated by fluid flow courses 19.
[0029] Each blade 16 on bit face 20 provides a cutter-supporting
surface 17 to which a plurality of cutter elements are mounted. In
this embodiment, a plurality of primary cutter elements 40 having
cutting faces 44 are mounted to cutter-supporting surface 17 of
each blade 16, and a plurality of secondary cutter elements 50
having cutting faces 54 are mounted to cutter-supporting surface 17
of each blade 16. Primary cutter elements 40 are generally arranged
in rows extending along each blade 16, and secondary cutter
elements 50 are generally arranged in rows extending along each
blade 16. However, secondary cutter elements 50 are positioned
behind the primary cutter elements 40 provided on the same blade
16. Thus, when bit 10 rotates about central axis 11 in the cutting
direction 18, secondary cutter elements 50 trail the primary cutter
elements 40 provided on the same blade 16. Thus, as used herein,
the term "secondary cutter element" is used to describe a cutter
element that trails any other cutter element on the same blade 16
when bit 10 is rotated in the cutting direction represented by
arrow 18. Further, as used herein, the term "primary cutter
element" is used to describe a cutter element provided on the
leading edge of a blade 16. In other words, when bit 10 is rotated
about central axis 11 in the cutting direction 18 a "primary cutter
element" does not trail any other cutter elements on the same blade
16. As will be described in more detail below, primary cutter
elements 40 are sized, positioned, and configured to mill a window
in steel casing, whereas secondary cutter elements 50 are sized,
positioned, and configured to drill through the formation after
milling through the casing.
[0030] In general, primary cutter elements 40 and secondary cutter
elements 50 need not be positioned in rows, but may be mounted in
other suitable arrangements provided each cutter element is either
in a leading position (e.g., primary cutter element 40) or trailing
position (e.g., secondary cutter element 50). Examples of suitable
arrangements may include without limitation, rows, arrays or
organized patterns, randomly, sinusoidal pattern, or combinations
thereof.
[0031] In the embodiment shown in FIG. 1, primary cutter elements
40 and the secondary cutter elements 50 are mounted so that their
cutting faces 44, 54, respectively, are forward facing. As used
herein, "forward facing" is used to describe the orientation of a
surface that is substantially perpendicular to or at an acute angle
relative to the cutting direction 18 of bit 10. For instance, a
forward facing cutting face 44, 54 may be oriented substantially
perpendicular to the cutting direction of bit 10, may include a
backrake angle, and/or may include a siderake angle.
[0032] Primary cutting faces 44 have a greater extension height
than secondary cutting faces 54. As used herein, the term
"extension height" is used to describe the distance a cutting face
extends perpendicularly from the cutter-supporting surface of the
blade to which it is attached. Thus, primary cutting faces 44 will
contact the object being milled/drilled prior to secondary cutting
faces 54, and generally provide a greater depth-of-cut than
secondary cutting faces 54.
[0033] In this embodiment, each backup cutter element 50 is a
conventional cutter element. In particular, each backup cutter
element 50 comprises an elongated and generally cylindrical support
member or substrate which is received and secured in a pocket
formed in the surface of the blade 16 to which it is fixed, and
each cutting face 54 comprises a forward facing disk or
tablet-shaped, hard cutting layer of polycrystalline diamond or
other superabrasive material is bonded to the exposed end of the
corresponding support member.
[0034] In this embodiment, primary cutter elements 40 are generally
cylindrical and mounted to blades 16, but are not conventional
cutter elements and are not made of conventional cutter element
materials. Rather, each primary cutter element 40 is made of a
whisker ceramic composite 60 shown in more detail in FIG. 2.
[0035] Referring now to FIG. 2, an enlarged view of the
microstructure of whisker ceramic composite 60 used to form cutter
elements 40 is shown. Although whisker ceramic composite 60 is used
to form cutter elements 40 of FIG. 1, in general, whisker ceramic
composite 60 can be used to form other embodiments of cutter
elements described herein as well as other types of cutter elements
and cutting structures.
[0036] In general, a whisker ceramic composite comprises a ceramic
matrix embedded with a plurality of distributed fibers or whisker
reinforcements. As shown in FIG. 2, whisker ceramic composite 60
comprises a ceramic matrix 61 embedded with a plurality of
distributed whiskers 62 that reinforce ceramic matrix 61. In
embodiments described herein, ceramic matrix 61 preferably
comprises aluminum-oxide or zirconium-oxide, and whiskers 62
preferably comprise silicon-carbide. In general, whiskers 62 can be
uniformly distributed throughout ceramic matrix 61 or layered
within the ceramic matrix 61. In addition, whether uniformly
distributed or layered, whiskers 62 can be "oriented" parallel to
the cutting plane, perpendicular to the cutting plane, or at an
acute angle relative to the cutting plane. The orientation relative
to the cutting plane can be varied between different layers as
desired. As used herein, the term "cutting plane" refers to a plane
oriented perpendicular to the cutting face (e.g., cutting face
44).
[0037] Experimental data and known material properties indicate
that whisker ceramic composites including whisker ceramic composite
60 offer the potential for improved strength and toughness (e.g.,
resistance to fractures), improved resistance to thermal shock, and
overall improved performance and durability cutting metals (e.g.,
steel) as compared to conventional cutter element materials such as
polycrystalline diamond, cubic boron nitride, thermally stable
diamond, polycrystalline cubic boron nitride, and tungsten carbide.
For example, conventional cutter elements (e.g., secondary cutter
elements 50) typically exhibit significant decreases in cutting
effectiveness following the development of wear flats. However,
cutter elements having cutting faces made of whisker ceramic
composites (e.g., primary cutter elements 40) exhibit the ability
to continue cutting effectively even after wear flats develop. In
other words, whisker ceramic composites exhibit a "self-sharpening"
characteristic that can continue to effectively cut metals even
after significant wear. For instance, for testing purposes, an
extremely large wear flat was intentionally formed on a cutter
element cutting face made of a whisker ceramic composite, yet the
cutter element continued to use the remaining material as a cutting
edge. In addition, as previously described, conventional cutter
elements (e.g., secondary cutter elements 50) include a cylindrical
substrate and a forward facing tablet of hard cutting material
bonded to the exposed end of the corresponding substrate. Thus, the
effective volume of cutting material on a conventional cutter is
limited to the tablet of hard cutting material. However, in
embodiments described herein, the cutter elements are preferably
entirely made of a whisker ceramic composite to increase and
maximize the total volume of cutting material. For example, primary
cutter elements 40 previously described and shown in FIG. 1 have a
cylindrical body made of a homogenous whisker ceramic
composite--the entire volume of each cutter element 40 is made of
whisker ceramic composite 80.
[0038] As shown in FIG. 1, cutting faces 44 of whisker ceramic
composite primary cutter elements 40 are planar. However, in other
embodiments, the cutting faces of the whisker ceramic composite
cutter elements (e.g., cutting faces 44) can have other geometries.
Moreover, cutter elements made of whisker ceramic composites are
particularly suited to a variety of different geometries as
experimental data suggests that any exposed portion of a whisker
ceramic composite cutter element can function as a cutting edge. In
conventional cutter elements such as secondary cutter elements 50,
the relatively thin table of ultrahard material forming the cutting
face (e.g., cutting face 54) is bonded to the underlying substrate.
Such a bonded connection between the table and the substrate can
lead to delamination and chipping issues, particularly in cases
where unconventional and exotic geometries are employed for the
cutting face--residual stresses from processing the bonded layered
composites limits it service loading. However, whisker ceramic
composite cutter elements such as primary cutter elements 40, do
not include layers bonded together, and thus, offer the potential
for a greater variety of cutting face geometries.
[0039] Referring now to FIG. 3, an embodiment of a method 70 for
sidetracking from a cased borehole with bit 10 of FIG. 1 is shown.
In this embodiment, method 70 starts in block 71, where bit 10 is
connected to the lower end of a drillstring and lowered downhole
through the casing. Mill 10 is lowered into the cased borehole to
the depth at which sidetracking is desired. Moving now to block 72,
at the desired depth, mill 10 is employed to drill or mill through
the casing to the surrounding formation. More specifically, mill 10
is rotated in cutting direction 18 while simultaneously being
guided by a wedge or whipstock to engage the inside of the metal
casing with cutting face 20. In this embodiment, whisker ceramic
composite cutter elements 40 perform all or substantially all of
the cutting of the metal casing, while the conventional secondary
cutter elements 50 perform little, if any, cutting of the metal
casing. In particular, whisker ceramic cutter elements 40 have
extension heights greater than secondary cutter elements 50, and
thus, engage the casing before secondary cutter elements 50.
Consequently, the casing is cut primarily by the whisker ceramic
composite cutter elements 40, whereas secondary cutter elements 50
do little cutting of the casing and are substantially preserved for
drilling through the formation after milling through the
casing.
[0040] Next, in block 73, bit 10 continues to cut through the metal
casing, relying substantially or completely on whisker ceramic
cutter elements 40, until a window is formed in the casing. In
other words, bit 10 mills completely through the casing and into
the surrounding formation. Bit 10 is designed to both mill through
the casing, and then drill through the formation surrounding the
casing without tripping. Thus, as shown in block 74, in this
embodiment of method 70, bit 10 continues to be rotated in cutting
direction 18 to engage the formation surrounding the casing with
cutting face 20. As previously described, whisker ceramic composite
cutter elements 40 have a greater extension height than secondary
cutter elements 50. Thus, at least initially, whisker ceramic
composite cutter elements 40 bear a significant cutting duty in the
formation. Although whisker ceramic composite cutter elements 40
have improved toughness and are well-suited to cutting metals, they
are generally less suited to cutting abrasive materials (e.g., the
subterranean formation) as compared to secondary cutter elements
50. Thus, whisker ceramic composite cutter elements 40 quickly wear
while drilling in the formation, thereby transferring the formation
cutting duty to secondary cutter elements 50. Thus, secondary
cutter elements 50 are preserved during milling of the metal casing
in order to be used for drilling through the formation, and primary
cutter elements 40 are used to mill the metal casing and sacrificed
during drilling of the formation. In this manner, bit 10 leverages
primary cutter elements 40 made of whisker ceramic composites,
which provide enhanced performance in cutting metals, to mill the
metal casing, and leverages secondary cutter elements 50 made of
conventional cutter element materials to cut through the
formation.
[0041] Although cutting device 10 is shown as a "torpedo" style
fixed cuter bit, the use of whisker ceramic composite cutter
elements 40 described herein is not limited to that particular type
of fixed cutter bit. In general, embodiments of whisker ceramic
composite cutter elements (e.g., primary cutter elements 40) can be
used on any type of fixed cutter bit or mill known in the art.
Although whiskers have been disclosed for use in a ceramic matrix,
whiskers can also be used with other types of materials. For
example, whiskers can be included in cubic boron nitride cutter
elements more adept at cutting rock and earthen formations.
[0042] Referring now to FIGS. 4-6, an embodiment of a cutting
device 100 for cutting or drilling through a downhole metal
structure (e.g., steel casing, a packer, etc.) is a mill shoe. In
this embodiment, cutting device 100 is designed to mill a downhole
metal object or structure such as casing or a packer. Cutting
device 100 has a central or longitudinal axis 105 and includes a
body 110 and a threaded connection or pin 14 for connecting cutting
device 100 to a drill string (not shown), which is employed to
rotate device 100 about axis 105 in a cutting direction 108. Body
110 has a first or upper end 110a attached to pin 14, a second or
lower end 110b opposite end 110a, and a through bore or passage 111
extending axially between ends 110a, b. Lower end 110b defines an
annular cutting face 112, which supports a cutting structure 113
designed to engage and cut a downhole metal structure or object. In
this embodiment, body 112 is general cylindrical, however, in other
embodiments, the body (e.g., body 112) may have other shapes. In
general, body 110 can be formed using powdered metal tungsten
carbide particles infiltrated with a binder material to form a hard
metal composite cast matrix or is machined from a metal block, such
as steel.
[0043] During milling operations, fluid (e.g., lubricating fluid,
drilling fluid, etc.) is pumped down the drillstring, through pin
14 and bore 111, and out of body 110 at end 110b. Such fluid is
distributed around cutting structure 113 and serves to flush away
metal cuttings during milling and to remove heat from cutting
device 100.
[0044] Referring still to FIGS. 4-6, cutting structure 113 is
provided on cutting face 112 and includes a plurality of
circumferentially adjacent cutter elements 120 mounted to lower end
110b. Cutting elements 120 extend axially from face 112 and lower
end 110b, and are designed to engage, cut, shear, and chip the
metal being milled. In this embodiment, cutter elements 120 are
rectangular prisms, however, as will be described in more detail
below, other geometries can also be employed such as cylindrical,
triangular, etc. In addition, cutter elements 120 are not made of
conventional cutter element materials such as polycrystalline
diamond or tungsten carbide. Rather, each cutter element 120 is
made of a whisker ceramic composite. More specifically, in this
embodiment, each cutter element 120 is made of whisker ceramic
composite 60 previously described. A variety of exemplary methods
for securing whisker ceramic cutter elements 120 to metal or metal
matrix body 110 will be described in more detail below. As
previously described, the ceramic matrix 61 of whisker ceramic
composite 60 preferably comprises aluminum-oxide or
zirconium-oxide, and the whiskers 62 of whisker ceramic composite
60 preferably comprise silicon-carbide. In general, the whiskers 62
in each cutter element 120 can be uniformly distributed throughout
the ceramic matrix 61 or layered within the ceramic matrix 61. In
addition, whether uniformly distributed or layered, the whiskers 62
in each cutter element 120 can be "oriented" parallel to the
cutting plane, perpendicular to the cutting plane, or at an acute
angle relative to the cutting plane. The orientation relative to
the cutting plane can be varied between different layers as
desired. As previously described, experimental data and known
material properties indicate whisker ceramic composites such as
composite 60 offer the potential for improved strength and
toughness (e.g., resistance to fractures), improved resistance to
thermal shock, and overall improved performance and durability
cutting metals (e.g., steel) as compared to conventional cutter
element materials such as polycrystalline diamond, cubic boron
nitride, thermally stable diamond, polycrystalline cubic boron
nitride, and tungsten carbide.
[0045] Referring now to FIGS. 7A-7D, exemplary whisker ceramic
composite cutter elements 130, 140, 150, 160 that can be used in
place of cutter elements 120 on cutting device 100 previously
described, or with other types of cutting devices, drill bits, and
mills are shown. Each cutter element 130, 140, 150, 160 is shown
moving in a cutting direction 121 to engage and cutting an
exemplary metal structure 122. In these embodiments, each cutter
element 130, 140, 150, 160 is made from whisker ceramic composite
60 previously described, however, it should be appreciated that
other whisker ceramic composites can be used to form cutter
elements 130, 140, 150, 160.
[0046] Referring first to FIG. 7A, whisker ceramic composite cutter
element 130 has a central axis 135, and includes a base portion 131
and a cutting portion 132 extending therefrom. Cutting portion 132
includes a cutting surface 133. Collectively, base 131 and cutting
portion 132 define the overall height of cutter element 130. In
this embodiment, cutter element 130 is generally a rectangular
prism although other geometries can be employed. Base portion 131
is secured to the cutting device (e.g., cutting device 100) such
that cutting portion 132 and cutting surface 133 extend beyond the
body of the cutting device for engaging the metal structure 122. In
this embodiment, cutting portion 132 includes a plurality of
elongate parallel spaced grooves or recesses 134 that define a
plurality of elongate parallel cutting teeth 136 therebetween along
cutting surface 133. Grooves 134 and teeth 136 are oriented
perpendicular to cutting direction 121. Each tooth 136 has a height
H.sub.136 measured axially from base portion 131 to the outermost
tip of the tooth 136. In this embodiment, H.sub.136 is preferably
between 0.020 in. and 0.040 in.
[0047] Spaced teeth 136 define a plurality of laterally spaced
apart parallel cutting edges 137 along cutting surface 133. Such
edges 137 are arranged one-behind-the-other relative to the cutting
direction 121. During cutting operations, the leading cutting edge
137 (relative to the cutting direction 121) shears metal structure
121, and the trailing cutting edges 137 (relative to the cutting
direction 121) help break up the shaved cuttings and chips from
metal structure 121. Further, in the event the leading cutting edge
137 gets damaged, breaks, or chips, the next cutting edge 137
(relative to the cutting direction 121) can take over the primary
cutting duties. In this sense, cutter element 130 is
self-sharpening. The internal corners within grooves 134 as well as
the external edges of teeth 136 (e.g., cutting edges 137) can be
radiused (preferably at least a 0.1 mm radius) as desired to reduce
stress concentrations and enhance durability in service.
[0048] Referring now to FIG. 7B, whisker ceramic composite cutter
element 140 is substantially the same as cutter element 130
previously described. Namely, cutter element 140 has a central axis
145, and includes cutting portion 132 as previously described and a
base portion 141 from which cutting portion 132 extends. However,
in this embodiment, base portion 141 includes a flange 142 opposite
cutting portion 132. Flange 142 extends radially outward and
extends along the entire periphery of base portion 141. As will be
described in more detail below, flange 142 functions as a retention
mechanism for securing cutter element 140 to the associated cutting
device (e.g., cutting device 100). The intersection between flange
142 and the remainder of base portion 141 and the radially
outermost edge 143 of flange 142 can be radiused (preferably at
least a 0.1 mm radius) as desired to reduce stress concentrations
and enhance durability in service.
[0049] Referring now to FIG. 7C, whisker ceramic composite cutter
element 150 has a central axis 155, and includes a base portion 151
and a cutting portion 152 extending therefrom. Collectively, base
151 and cutting portion 152 define the overall height of cutter
element 150. Cutting portion 152 includes a cutting surface 153. In
this embodiment, cutter element 150 is cylindrical, and thus, has
an outer diameter D.sub.150 that is preferably between 10.0 and
15.0 mm. In this embodiment, diameter D.sub.150 is 13.0 mm.
Although cutter element 150 is cylindrical in this embodiment, in
general, the cutter element (e.g., cutter element 150) may be
formed in a variety of shapes other than cylindrical. In this
embodiment, cutter element 150 is disposed at a backrake angle
.alpha.. In general, the backrake angle of a cutter element is the
angle formed between the central axis of the cutter element and the
normal vector of the surface of the material being cut (i.e., the
vector oriented perpendicular to the surface of the material being
cut). Thus, backrake angle .alpha. of cutter element 150 is the
angle measured between axis 155 of cutter element 150 and the
normal vector V of the surface of material 122 being cut. In this
embodiment, backrake angle .alpha. is preferably between 5.degree.
and 20.degree.. In more demanding applications, the backrake angle
.alpha. can be greater than 20.degree..
[0050] Base portion 151 is secured to the cutting device (e.g.,
cutting device 100) such that cutting portion 152 and cutting
surface 153 extend beyond the body of the cutting device for
engaging the metal structure 122. In this embodiment, cutting
portion 152 includes a plurality of steps 154 that define a
plurality of cutting edges 156a, b. The inner corners between steps
154 and cutting edges 156a, b can be radiused (preferably at least
a 0.1 mm radius) as desired to reduce stress concentrations and
enhance durability in service. Leading step 154 and corresponding
cutting edge 156a extends to a height H.sub.156a measured axially
from base portion 151, and trailing step 154 and corresponding
cutting edge 156b extends to a height H.sub.156b measured axially
from leading step 154. In general, height H.sub.156a and height
H.sub.156b can be the same or different. In this embodiment, height
H.sub.156a and height H.sub.156b are each 0.5 mm. Further, in this
embodiment, each step 154 has a length L.sub.154 measured
perpendicular to axis 155 equal to 1.0 mm.
[0051] Cutting portion 152 and cutting surface 153 define a total
depth-of-cut (DOC) D.sub.t, however, the total DOC D.sub.t is
divided and shared between cutting edges 156a, b. In other words,
leading cutting edge 156a engages metal structure 121 to a first
DOC D.sub.1, and trailing cutting edge 156b engages metal structure
121 to a DOC D.sub.2, and thus, neither cutting edge 154
experiences the total DOC D.sub.t.
[0052] Referring now to FIG. 7D, whisker ceramic composite cutter
element 160 has a central axis 165, and includes a base portion 161
and a cutting portion 162 extending therefrom. Cutting portion 162
includes a cutting surface 163. In this embodiment, cutter element
160 is generally a rectangular prism although other geometries can
be employed. Collectively, base 161 and cutting portion 162 define
the overall height of cutter element 160. Base portion 161 is
secured to the cutting device (e.g., cutting device 100) such that
cutting portion 162 and cutting surface 163 extend beyond the body
of the cutting device for engaging the metal structure 122.
[0053] In this embodiment, axis 165 is parallel to the normal
vector V, and thus, cutter element 160 is not disposed at a
backrake angle. However, cutting surface 163 is generally sloped
relative to the surface of material 122 being cut, thereby
resulting in an effective backrake. In particular, moving in the
opposite direction of cutting direction 121 from a leading side
160a of cutter element 160 to a trailing side 160b of cutter
element 160, the height of cutting surface 163 measured axially
from base portion 161 generally increases, thereby creating the
effective backrake. However, between sides 160a, 160b, cutting
surface 163 includes a random arrangement of recesses 166 and peaks
167 defining a plurality of cutting edges for engaging and cutting
metal structure 122. As any peak 167 becomes damaged or break,
another peak 167 and associated cutting edge can take on cutting
duties. The random arrangement of cutting edges of cutter element
160, and associated random cutting effect, may be particularly
suited for use in connection with impregnated bits. As is known in
the art, an impregnated bit, or simply an "impreg" bit, is a bit
having a cutting face impregnated with a plurality of diamonds that
engage and cut a material by a grinding action as opposed to a
shearing action. As an alternative to or in addition to diamonds
mounted to the cutting face of an impreg bit, a plurality of cutter
elements 160 can be secured to the impreg bit with cutting surfaces
163 extending from the bit face for engaging and grinding the
material being cut.
[0054] As previously described, whisker ceramic composite cutter
elements 40 are securely attached to blades 16 and whisker ceramic
composite cutter elements 120 are securely mounted to lower end
110b of cutting device 100. In general, embodiments of cutter
elements comprising whisker ceramic composites (e.g., cutter
elements 40, 120, 130, 140, 150, 160) can be secured to the body of
the underlying cutting device by any suitable means known in the
art. For example, embodiments of whisker ceramic composite cutter
elements described herein can be securely attached to an underlying
metal using known techniques for brazing ceramics to metals such as
microwave brazing techniques and metallising and active braze
techniques. Additional techniques for securely attaching cutter
elements comprising whisker ceramic composites to an underlying
cutting device are schematically illustrated in FIGS. 8A-8E. In
general, any of the attachment means disclosed in FIGS. 8A-8F and
described in more detail below can be employed to secure any cutter
element described herein, such as any of cutter elements 40, 120,
130, 140, 150, 160 previously described, to a cutting device (e.g.,
drill bit, mill, etc.).
[0055] Referring first to FIG. 8A, a cutting device 200 (e.g., a
mill or a drill bit) includes a body 201 and a cutter element 210
rigidly secured to the underlying body 201. In this embodiment,
cutter element 210 includes a metal (e.g., steel) substrate or base
211 and a whisker ceramic composite cutting layer 212 attached to
base 211. In addition, in this embodiment, cutting layer 212 is
made of whisker ceramic composite 60 and is rigidly and securely
mounted to base 211 via known brazing techniques. Base 211 includes
a throughbore 213 extending therethrough, and cutting layer 212
includes a throughbore 214 extending therethrough and coaxially
aligned with bore 213. A bolt 215 is advanced through bores 213,
214 and is threaded into a mating internally threaded receptacle in
body 201, thereby removably securing cutter element 210 to body 201
of cutting device 200. Use of bolt 215 to attached cutter element
210 to body 201 enables cutter elements 210 to be serviced and
maintained with relative ease as worn or damaged cutter elements
210 can be removed and replaced by unbolting them from body 201 and
then bolting new cutter elements 210 to body 201. This may also
provide a means to retrofit existing cutting devices with cutter
elements comprising whisker ceramic composite materials.
[0056] Referring now to FIG. 8B, a cutting device 300 (e.g., a mill
or a drill bit) includes a body 301 and a whisker ceramic composite
cutter element 310 rigidly secured to the underlying body 301 with
a metal sleeve or jacket 311. In this embodiment, cutter element
310 is made entirely of whisker ceramic composite 60 and is secured
within jacket 311 via interference fit. A combination of press
and/or shrink fit can be used to obtain desired interference. For
example, the metal sleeve 311 can be heated, the cutter element 310
slidably disposed therein, and then the metal sleeve 311 allowed to
cool and shrink into engagement with cutter element 310. In this
embodiment, an interference of about 0.5 mm. between cutter element
310 and sleeve 311 is provided. The exposed end of cutter element
310 defines a cutting surface or face 312. Metal jacket 311 is
preferably made of hardened steel (e.g., 4140 H.T with a yield
strength greater than 110 ksi), tool steel (e.g., A2 or H2), a
superalloy (e.g., Inconel), or heavy metal (e.g., Mo and W).
[0057] It should be appreciated that the interference fit desirably
places the whisker ceramic composite 60 forming cutter element 310
in compression, which offers the potential to enhance impact
resistance. With cutter element 310 securely disposed within sleeve
311, sleeve 311 is brazed to body 301 of cutting device 300 using
conventional brazing techniques. In this embodiment, sleeve 311 has
an open end 311a that receives cutter element 310 and a closed end
311b against which cutter element 310 is seated. Closed end 311b
includes a relief port or hole 313. However, in other embodiments,
the metal sleeve is opened at both ends.
[0058] Referring now to FIG. 8C, a cutting device 400 (e.g., a mill
or a drill bit) includes a body 401 and a whisker ceramic composite
cutter element 410 rigidly secured to the underlying body 401 with
a metal sleeve or jacket 411. In this embodiment, cutter element
410 is made entirely of whisker ceramic composite 60 and is secured
within jacket 411 via interference fit. Sleeve 411 is the same as
sleeve 311 previously described except that, in this embodiment,
both ends 411a, 411b of sleeve 411 are open, and further, sleeve
411 covers the entire periphery of cutter element 410. In other
words, cutter element 410 does not extend from sleeve 411. Cutter
element 410 has a cutting surface or face 412 at one end 411a of
sleeve 411 and a back face 413 at the opposite end 411b of sleeve
411. With cutter element 410 securely disposed within sleeve 411,
sleeve 411 is brazed to body 401 of cutting device 400 using
conventional brazing techniques.
[0059] Referring now to FIG. 8D, a cutting device 500 (e.g., a mill
or a drill bit) includes a body 501 and a whisker ceramic composite
cutter element 510 rigidly secured to the underlying body 501 with
a metal sleeve or jacket 511. In this embodiment, cutter element
510 is made entirely of whisker ceramic composite 60 and is secured
within sleeve 511 via interference fit. Sleeve 511 is the same as
sleeve 411 previously described except that, in this embodiment,
the inner surface of sleeve 511 engaging cutter element 510 tapers
inward moving from end 511b to end 511a. The tapered or negative
draft of sleeve 511 offers the potential for enhanced retention and
mechanical lock of cutter element 510 therein. Cutter element 510
has a cutting surface or face 512 at one end 511a of sleeve 511 and
a back face 513 at the opposite end 511b of sleeve 511. With cutter
element 510 securely disposed within sleeve 511, sleeve 511 is
brazed to body 501 of cutting device 500 using conventional brazing
techniques.
[0060] Referring now to FIG. 8E, a cutting device 600 (e.g., a mill
or a drill bit) includes a body 601 and a whisker ceramic composite
cutter element 610 rigidly secured to the underlying body 601. In
this embodiment, cutter element 610 is made entirely of whisker
ceramic composite 60 and is brazed to a metal (e.g., steel) base
611 using a filler material 612 and conventional brazing
techniques. The filler material 612 provides a transition layer
between the whisker ceramic composite cutter element 610 and metal
base 611 to enhance the connection therebetween. In addition, in
this embodiment, filler material 612 provides additional cutting
contact points when cutter element 610 is completely worn down to
filler material 612. In particular, crushed carbide is distributed
throughout a binder in filler material 612. The crushed carbide
provides an added cutting mechanism once exposed. With cutter
element 610 securely attached to base 611 with filler material 612,
base 611 is brazed to body 601 of cutting device 600 using
conventional brazing techniques.
[0061] Referring now to FIG. 8F, a cutting device 700 (e.g., a mill
or a drill bit) includes a body 701 and a whisker ceramic composite
cutter element 710 rigidly secured to the underlying body 701 with
a braze material 711. In this embodiment, cutter element 710 is
made of whisker ceramic composite 60 pre-coated with braze material
711, which includes an "active" brazing component for subsequent
brazing to body 701 by means known in the art such as vacuum
furnace methods, argon methods, or JPL microwave brazing methods.
Examples of active braze materials that can be used for braze
material 711 include titanium, TicuSil.RTM. brazing alloy available
from Morgan Technical Ceramics of Hayward, Calif., and
IncuSil.RTM.-ABA.TM. brazing alloy available from available from
Morgan Technical Ceramics of Hayward, Calif.
[0062] Referring now to FIG. 8G, a cutting device 800 (e.g., a mill
or a drill bit) includes a body 801 and a whisker ceramic composite
cutter element 810 rigidly secured to the underlying body 801. In
this embodiment, cutter element 810 is made entirely of whisker
ceramic composite 60 and includes a cutting portion 811 at a first
end 810a, a base portion 812 extending from an end 810b to cutting
portion 811, and a retention flange 813 extending around the
periphery of base portion 812 at end 810b. Cutter element 810 is
precast into the matrix 814 of the body 801. The matrix 814
surrounds retention flange 813, thereby securing cutter element 810
to body 801. As previously described with respect to cutter element
140 of FIG. 7B, the outer edge 815 of flange 813 can be radiused to
reduce stress concentrations.
[0063] In the manner described, cutter elements comprising whisker
ceramic composites can be securely attached to cutting devices for
milling a downhole metal object or structure such as casing or a
packer. Experimental data and known material properties indicate
such whisker ceramic composites offer the potential for improved
strength and toughness (e.g., resistance to fractures), improved
resistance to thermal shock, and overall improved performance and
durability cutting metals (e.g., steel) as compared to conventional
cutter element materials such as polycrystalline diamond, cubic
boron nitride, thermally stable diamond, polycrystalline cubic
boron nitride, and tungsten carbide. Accordingly, embodiments of
cutter elements described herein offer the potential for improved
metal cutting performance, speed, and durability as compared to
conventional cutter elements.
[0064] While preferred embodiments have been shown and described,
modifications thereof can be made by one skilled in the art without
departing from the scope or teachings herein. The embodiments
described herein are exemplary only and are not limiting. Many
variations and modifications of the systems, apparatus, and
processes described herein are possible and are within the scope of
the invention. For example, the relative dimensions of various
parts, the materials from which the various parts are made, and
other parameters can be varied. Accordingly, the scope of
protection is not limited to the embodiments described herein, but
is only limited by the claims that follow, the scope of which shall
include all equivalents of the subject matter of the claims. Unless
expressly stated otherwise, the steps in a method claim may be
performed in any order. The recitation of identifiers such as (a),
(b), (c) or (1), (2), (3) before steps in a method claim are not
intended to and do not specify a particular order to the steps, but
rather are used to simplify subsequent reference to such steps.
* * * * *