U.S. patent application number 12/885594 was filed with the patent office on 2011-03-24 for enhanced secondary substrate for polycrystalline diamond compact cutting elements.
Invention is credited to Timothy P. Beaton.
Application Number | 20110067930 12/885594 |
Document ID | / |
Family ID | 43755663 |
Filed Date | 2011-03-24 |
United States Patent
Application |
20110067930 |
Kind Code |
A1 |
Beaton; Timothy P. |
March 24, 2011 |
ENHANCED SECONDARY SUBSTRATE FOR POLYCRYSTALLINE DIAMOND COMPACT
CUTTING ELEMENTS
Abstract
A cutting structure for a drill bit includes a diamond table
affixed to one end of a first substrate. A second substrate is
affixed to the other end of the first substrate. The second
substrate is made from a different material than the first
substrate. The first and second substrates are substantially
coaxial.
Inventors: |
Beaton; Timothy P.;
(Calgary, CA) |
Family ID: |
43755663 |
Appl. No.: |
12/885594 |
Filed: |
September 20, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61244723 |
Sep 22, 2009 |
|
|
|
Current U.S.
Class: |
175/434 ; 51/307;
51/309 |
Current CPC
Class: |
B24D 99/005 20130101;
E21B 10/573 20130101 |
Class at
Publication: |
175/434 ; 51/307;
51/309 |
International
Class: |
E21B 10/46 20060101
E21B010/46; B24D 3/00 20060101 B24D003/00 |
Claims
1. A cutting structure for a drill bit, comprising: a diamond table
affixed to one end of a first substrate; and a second substrate
affixed to the other end of the first substrate, the second
substrate made from a different material than the first substrate,
the first and second substrates being substantially coaxial.
2. The cutting structure of claim 1 wherein the diamond table
comprises polycrystalline diamond and the first substrate comprises
tungsten carbide.
3. The cutting structure of claim 1 wherein the second substrate
comprises a material composition having higher abrasion resistance
proximate a periphery thereof and higher strength proximate a
center thereof.
4. The cutting structure of claim 1 wherein the second substrate
comprises an erosion resistant outer layer.
5. The cutting structure of claim 4 wherein the erosion resistant
outer layer is disposed except on portions of the second substrate
to be affixed to a bit body.
6. The cutting structure of claim 4 wherein the erosion resistant
outer layer comprises thermally stable polycrystalline diamond.
7. The cutting structure of claim 1 wherein the second substrate
comprises steel.
8. The cutting structure of claim 1 wherein a material composition
of the first substrate is substantially uniform.
9. The cutting structure of claim 1 wherein the second substrate
comprises a material composition having higher abrasion resistance
proximate a first longitudinal end thereof and higher strength
proximate a second longitudinal end thereof.
10. The cutting structure of claim 1 wherein the second substrate
material comprises thermally stable polycrystalline diamond.
11. A drill bit, comprising: a bit body; and at least one
polycrystalline diamond compact cutter affixed to the bit body, the
cutter comprising at least a diamond table affixed to one end of a
first substrate and a second substrate affixed to the other end of
the first substrate, the second substrate made from a different
material than the first substrate, the first and second substrates
being substantially coaxial.
12. The drill bit of claim 11 wherein the diamond table comprises
polycrystalline diamond and the first substrate comprises tungsten
carbide.
13. The drill bit of claim 11 wherein the second substrate
comprises a material composition having higher abrasion resistance
proximate a periphery thereof and higher strength proximate a
center thereof.
14. The drill bit of claim 11 wherein the second substrate
comprises an erosion resistant outer layer.
15. The drill bit of claim 14 wherein the erosion resistant outer
layer is disposed except on portions of the second substrate to be
affixed to a bit body.
16. The drill bit of claim 14 wherein the erosion resistant outer
layer comprises thermally stable polycrystalline diamond.
17. The drill bit of claim 14 wherein the second substrate
comprises steel.
18. The drill bit of claim 11 wherein a material composition of the
first substrate is substantially uniform.
19. The drill bit of claim 11 wherein the second substrate
comprises a material composition having higher abrasion resistance
proximate a first longitudinal end thereof and higher strength
proximate a second longitudinal end thereof.
20. The drill bit of claim 10 wherein the bit body comprises a
material affixable to the second substrate by welding.
21. The drill bit of claim 19 wherein the bit body comprises
steel.
22. The drill bit of claim 11 wherein the second substrate material
comprises thermally stable polycrystalline diamond.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Priority is claimed from U.S. Provisional Application No.
61/244,723 filed on 22 Sep. 2009.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention is related to fixed cutter drill bits
used for drilling wellbores in subsurface earthen formations. More
particularly, the present invention relates to polycrystalline
diamond compact ("PDC") cutters used to shear earthen formations in
so-called "fixed cutter" drill bits.
[0005] 2. Background Art
[0006] Polycrystalline diamond compact ("PDC") cutting elements,
called "cutters", used in wellbore drill bits are well known in the
art. Generally, a PDC cutter is created in a high-temperature,
high-pressure process. During the high-temperature, high-pressure
process, called a "press cycle", a polycrystalline diamond "table"
is created from synthetic diamond grit. During the press cycle the
diamond table is also bonded to a substrate, usually formed from
cemented tungsten carbide ("carbide"), forming the pieces into a
cylinder with an integral carbide substrate.
[0007] In many cases, PDC cutters are manufactured with a short
overall length to allow the making of multiple PDC cutters in a
single press cycle. For cutters made with such short length
substrates as above, in order to extend the length of the PDC
cutter to an industry-acceptable dimension, a second cemented
tungsten carbide substrate is bonded to the short length PDC cutter
substrate in a separate process. Such processes include methods
such as the "LS Bonding" process described in U.S. Pat. No.
4,225,322 issued to Knemeyer. Generally, the characteristics of the
second carbide substrate are matched as closely as possible to the
characteristics of the carbide substrate that is bonded to the
diamond table (i.e., the short length substrate).
[0008] As is well known in the art, PDC cutters are generally
attached to drill bit bodies, which can be either made from steel
or a tungsten carbide `matrix`, through brazing. The extended
length PDC cutter, for example, as created through the addition of
the second carbide substrate to a short length substrate as
explained above, is therefore required to provide sufficient
surface area to make a reliable braze joint between the cutter and
the bit body.
[0009] Drill bits that use PDC cutters as their primary cutting
elements are called `PDC bits`. PDC bits were first used for
drilling earth formations in the 1970's. Initially, PDC bits were
primarily used for drilling low-strength formations because the PDC
cutters could not withstand the forces created when drilling harder
formations. More recently, however, PDC bit design and PDC cutter
technology has improved substantially, thus enabling PDC bits to
drill many tougher formations more effectively than other types of
drill bits. However, there are still many formations that are too
hard or too abrasive to be effectively drilled with PDC bits, and
these formations result in the most expensive drilling in the
industry because the speeds at which such formations can be drilled
are very low, and drill bit life is very short.
[0010] Many attempts have been made to further increase the wear
resistance of PDC bits, including the use of cylinder cutters
comprised of a variety of thermally stable diamond pieces, such as
is disclosed in U.S. Pat. No. 5,205,684 issued to Meskin et al.,
and the addition of diamond particles into the body of the bit or
as separate inserts behind PDC cutters, such as is disclosed in
U.S. Pat. No. 4,718,505 issued to Fuller. Unfortunately, in many
cases, when the wear resistance of a PDC cutter is improved, the
overall life of the bit may not increase in many drilling
applications due to an increased susceptibility of such PDC cutters
to impact damage. In most cases, when a PDC cutter is made more
wear resistant, it often becomes more brittle and can fail more
quickly when experiencing uneven loading in certain subsurface rock
formations.
[0011] Another limiting factor for PDC bits in many drilling
applications is excessive wear to the body of the PDC cutter
resulting from erosion. In such situations, the carbide substrates
wear relatively rapidly, thus accelerating the break down of the
PDC cutter and, therefore, reducing the useful life of the PDC bit.
U.S. Pat. No. 5,667,028 issued to Truax et al., for example
discloses a PDC cutter that has a multitude of PDC segments all
formed in the same PDC cutter body. Such arrangement has been
observed to help prevent substrate erosion as the PDC material that
is embedded in the carbide substrate helps to reduce wear.
[0012] Accordingly, there is a need for PDC cutters with increased
longevity under different drilling conditions. A PDC cutter which
has enhanced abrasion resistance but unreduced impact resistance
will allow a drill bit fitted with those cutters to drill longer
sections in hard formations, and a PDC cutter with enhanced erosion
resistance will allow a bit fitted with those cutters to drill
longer sections in highly abrasive environments.
SUMMARY OF THE INVENTION
[0013] One aspect of the invention is an improved PDC cutter
created by bonding a substrate (secondary substrate') of dissimilar
material to an integral carbide substrate of a PDC cutter. The
material composition of the secondary substrate can be adjusted to
enhance the performance of the PDC cutter in accordance with the
requirements of the particular drilling conditions to be
encountered. The integral carbide substrate and the secondary
substrate are substantially coaxial.
[0014] A drill bit according to another aspect of the invention
includes a bit body and at least one polycrystalline diamond
compact (PDC) cutter affixed to the bit body. The PDC cutter
includes at least a diamond table affixed to one end of a first
substrate and a second substrate affixed to the other end of the
first substrate. The second substrate is made from a different
material than the first substrate. The first and second substrates
are substantially coaxial.
[0015] Other aspects and advantages of the invention will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows an example PDC cutter according to the
invention.
[0017] FIG. 2 shows a recessed section being formed in the integral
substrate of a PDC cutter.
[0018] FIG. 3 shows an example of a secondary substrate having
different material characteristics at different places within the
secondary substrate.
[0019] FIG. 4 shows an example fixed cutter drill bit having at
least one cutter made according to the invention.
[0020] FIG. 5 shows an example secondary substrate including a
steel center pressed or brazed inside a carbide cylinder.
[0021] FIG. 6 shows an example partially coated secondary
substrate, leaving an exposed surface for attachment to a bit
body.
DETAILED DESCRIPTION
[0022] FIG. 1 shows an example polycrystalline diamond compact
("PDC") cutting element or "cutter" 10 having a diamond table 12, a
carbide substrate 14 integrally formed with the diamond table (the
integral substrate), and a secondary substrate 16 bonded to the
integral substrate 14. While the present example is shown in FIG. 1
and is described herein as a cylinder-shaped cutter, the invention
is equally applicable to any shape of PDC cutter. In the present
example, the secondary substrate 16 is comprised of a material
dissimilar to the material of the integral substrate 14 in order to
enhance the performance of the cutter 10, and can be attached to
the integral substrate 14 in a variety of methods that are known in
the art. In the invention, while the shape of the cutter is not
limited, the integral substrate 14 and the secondary substrate 16
are substantially coaxial.
[0023] The material composition of the secondary substrate 16 can
be selected to enhance the performance of the PDC cutter 10 in a
variety of different drilling conditions. In situations where PDC
cutters tend to experience rapid abrasive wear to the diamond
table, the secondary substrate 16 can be formed from highly
abrasion resistant material, such as a mixture of tungsten carbide
particles with a low metal content, to increase the overall wear
resistance of the PDC cutter 10.
[0024] Another possible advantage to the PDC cutter structure of
the invention can be observed in FIG. 2. As a PDC cutter wears, the
self-sharpening action of a PDC cutter, which is well documented in
the literature, produces a recessed section 18 in the surface of
the integral substrate 14, located generally between the diamond
table 12 and the secondary substrate 16. This recessed section 18
allows drilling fluid to flow into the void space created by the
recessed section 18, helping to keep the diamond table 12 cool
while the secondary substrate 16 inhibits further wear. It will be
appreciated by those skilled in the art that the material
composition of the secondary substrate 16 can vary widely and yet
still have abrasion resistance that is much higher than that of the
integral carbide substrate 14. Such differential abrasion
resistance may enhance formation of the recessed section 18, which
may prove advantageous in certain drilling conditions.
[0025] The material composition of the integral carbide substrate
14 is a critical factor in the manufacturing of an effective PDC
cutter. The material composition of the integral carbide substrate
14 must be very uniform throughout its cross section in order to
properly form the diamond table and handle residual stresses
created during the pressing operation. The secondary substrate 16,
however, is under no such limitations, and can therefore have
substantially different material properties throughout its cross
section. This enables creation of a secondary substrate 16 with,
for example, varying abrasion resistance along the cross
section.
[0026] Referring to FIG. 3, in another example the secondary
substrate 16 can be made from varying material composition so as to
have highest abrasion resistance at the periphery of the substrate
structure, as shown at 20, to help inhibit wear to the diamond
table (12 in FIG. 1). Conversely, the secondary substrate 22 can
also have higher material strength toward the center of the
substrate structure, as shown at 22, to help inhibit breakage of
the PDC cutter (10 in FIG. 1) under high loading. In other words,
unlike the integral carbide substrate (14 in FIG. 1), the secondary
substrate 16 can be both highly abrasion resistant and highly
impact resistant by varying the material properties across the
cross section of the secondary substrate (16 in FIG. 1).
[0027] A drill bit made using one or more cutters according to any
of the examples explained herein is shown in FIG. 4, wherein the
drill bit 11 includes a bit body 13 of types well known in the art
for affixing thereto a plurality of PDC cutters 10. Any or all of
the cutters shown in the example bit 11 in FIG. 4 may be made
according to any of the examples explained herein, and it is to be
clearly understood that the bit body and cutter configuration shown
in FIG. 4 is only meant to serve as an example of a drill bit made
using cutters according to the invention. Accordingly, the bit and
cutter structure and numbers of cutters on the bit as shown in FIG.
4 are in no way intended to limit the scope of the present
invention.
[0028] In drilling situations where PDC cutters tend to experience
severe impact damage, using a secondary substrate formed from
highly abrasion resistant material can allow the use of a more
impact resistant diamond table without sacrificing overall wear
resistance. As is well known in the art, PDC cutters that are more
abrasion resistant tend to be less resistant to impact. As a
result, compromises are typically made in the overall design of PDC
bits that use highly abrasion resistant cutters in order to
minimize impact loading of the cutters and therefore limit impact
damage to or breakage of the PDC cutters. Such design
considerations may result in a bit that drills less efficiently.
However, in the present invention, a diamond table and integral
substrate that are inherently more impact resistant, and therefore
less abrasion resistant, can be joined with a highly abrasion
resistant secondary substrate, and can therefore provide a PDC
cutter that is both highly abrasion resistant and highly impact
resistant.
[0029] In a further example, in drilling conditions where PDC
cutters tend to experience severe impact damage, using a secondary
substrate with higher ductility, such as steel, can cushion the
force of the impact on the cutters, thus improving the impact
resistance of the overall PDC cutter structure. This configuration
can also provide a PDC cutter that is both highly abrasion
resistant, due to the use of a diamond table that is inherently
more abrasion resistant and less impact resistant, and highly
impact resistant due to the use of a secondary substrate that
cushions the impact loading on the cutter.
[0030] In yet a further example, in drilling conditions where the
body of the PDC cutter tends to experience rapid erosive wear, the
secondary substrate can be formed with a highly erosion resistant
outer layer, as can be provided, for example with many different
types of ceramics.
[0031] A secondary substrate can also be made wherein the secondary
substrate may be made from a very erosion resistant material layer
on the outer surface, for example a material even more erosion
resistant that traditional carbides, but may include a material in
the center that is tougher and stronger than the erosion resistant
material on the outer layer.
[0032] Examples of materials for a secondary substrate that would
be more erosion resistant than carbide substrate materials known in
the art may include the following:
[0033] a) a made-for-purpose layer of carbide that is formulated to
have higher erosion resistance yet lower structural strength than a
typical integral substrate would have, as can be achieved by
reducing the percentage of metal (typically cobalt) in the carbide
substrate;
[0034] b) a substrate wherein the outer layer (OD) has been coated
in selected regions with diamond through chemical vapor deposition
(CVD) or physical vapor deposition (PVD), yet leaving some of the
outer surface uncoated to enable brazing the cutter to the bit
body, an example of which is shown in FIG. 6, wherein a coated
portion of the outer surface of the secondary substrate 16 is shown
at 34, and an uncoated portion for affixing the secondary substrate
16 to a bit body is shown at 36;
[0035] c) a substrate where the outer layer is made from highly
erosion resistant ceramic, for example, cubic boron nitride (CBN),
while having an inner layer made from stronger, tougher material,
including, for example, steel;
[0036] d) a substrate where, again, the material composition across
the cross-section varies, but in the present example the substrate
may include a very tough/strong center (e.g., much tougher than
typically carbides) and an outer layer that conforms to industry
standards for erosion resistance. An example of the foregoing would
include a steel core pressed or brazed into an annular carbide
cylinder. An example of a steel core pressed or brazed into an
annular carbide cylinder is shown in FIG. 5, wherein the core is
shows at 30 and the annular cylinder is shown at 32.
[0037] It is believed in the wellbore drilling industry that drill
bits made using PDC cutters affixed to steel bit bodies tend to
suffer less impact damage because the steel bit body absorbs the
energy from impacts better than matrix bit bodies (as matrix is
much harder than steel). To the extent such belief is correct, the
same effect could be obtained by making the secondary substrate
primarily made from steel to absorb the impact loading on the
cutter. One possible additional benefit of making the secondary
substrate out of steel is that it becomes possible to weld (instead
of braze) the cutter onto a bit. Welding creates a much stronger
bond than brazing and may make possible certain bit designs that
are not possible using conventionally braze connected cutters.
[0038] In still other examples, the secondary substrate may contain
thermally stable polycrystalline diamond ("TSP") segments to
enhance wear resistance. The TSP may be in the form of a TSP
included in a coating over parts of the secondary substrate or may
be included in the material of all or part of the secondary
substrate. Certain sections of the secondary substrate should
exclude the use of TSP so as to maintain the capability of
attaching the cutter to the bit body, such as by brazing.
[0039] In still other examples, it is possible to vary the
properties of the secondary substrate along its length rather than
across its diameter. For example, a secondary substrate can have a
harder and softer portion separated longitudinally. The harder
portion could be disposed toward the end where it attaches to the
PDC cutter, that is, to substantially match the properties of the
integral substrate of the PDC cutter. A softer/tougher material may
be disposed longitudinally toward the end of the cutter where it
attaches to the drill bit body to enhance braze strength. Such
longitudinally varying properties may be made by layering or by
gradationally varying the substrate material properties during
manufacture.
[0040] PDC cutter bits made according to the various aspects of the
invention may enable more flexibility in designing bits to perform
optimally under more widely varying drilling conditions than PDC
cutter bits known in the art prior to the present invention.
[0041] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
* * * * *