U.S. patent application number 09/682466 was filed with the patent office on 2002-03-21 for rotary drill bit design method.
Invention is credited to Griffin, Nigel Dennis, Hughes, Peter Raymond, Matthias, Terry R..
Application Number | 20020033077 09/682466 |
Document ID | / |
Family ID | 26927534 |
Filed Date | 2002-03-21 |
United States Patent
Application |
20020033077 |
Kind Code |
A1 |
Griffin, Nigel Dennis ; et
al. |
March 21, 2002 |
Rotary drill bit design method
Abstract
A method for use in designing rotary drill bits comprises
determining locations in which cutters are to be provided,
determining likely wear rates for cutters positioned at those
locations, and using the likely wear rates to chose between
relatively high and relatively low wear rate cutters for each
location. The cutters all have substantially the same impact
toughness.
Inventors: |
Griffin, Nigel Dennis;
(Nympsfield, GB) ; Hughes, Peter Raymond; (Stroud,
GB) ; Matthias, Terry R.; (Upton St. Leonards,
GB) |
Correspondence
Address: |
SCHLUMBERGER OILFIELD SERVICES
JEFFREY E. DALY
7211 N. GESSNER
HOUSTON
TX
77040
US
|
Family ID: |
26927534 |
Appl. No.: |
09/682466 |
Filed: |
September 6, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60234075 |
Sep 20, 2000 |
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60281054 |
Apr 2, 2001 |
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Current U.S.
Class: |
76/108.2 ;
175/327 |
Current CPC
Class: |
C04B 2237/401 20130101;
C04B 37/021 20130101; Y10T 428/30 20150115; C04B 2235/3206
20130101; F16C 2206/04 20130101; C04B 35/52 20130101; F16C 33/043
20130101; Y10T 428/12493 20150115; C04B 2235/3208 20130101; C04B
2235/427 20130101; B22F 2999/00 20130101; C04B 2237/363 20130101;
C04B 2235/3215 20130101; C04B 2235/442 20130101; Y10T 407/27
20150115; Y10T 428/265 20150115; Y10T 428/12625 20150115; E21B
10/567 20130101; Y10T 428/26 20150115; B22F 7/06 20130101; Y10T
428/24942 20150115; B22F 2005/001 20130101; B22F 2998/00 20130101;
C04B 2235/3213 20130101; C04B 35/645 20130101; B22F 2003/244
20130101; C04B 2235/405 20130101; B22F 2998/00 20130101; B22F
2207/03 20130101; B22F 2999/00 20130101; B22F 1/052 20220101; C22C
26/00 20130101; B22F 2999/00 20130101; B22F 1/052 20220101; C22C
26/00 20130101 |
Class at
Publication: |
76/108.2 ;
175/327 |
International
Class: |
B21K 005/04 |
Claims
What is claimed is:
1. A method for designing a fixed cutter drill bit comprising
determining a layout of cutter locations in which cutters are to be
positioned upon a bit body, determining the likely wear rate for at
least the cutters provided in some of the cutter locations and
using the determined likely wear rates to determine whether to
mount a cutter of a first type of relatively low abrasion
resistance or a cutter of a second type of a relatively high
abrasion resistance in each cutter location, wherein the first type
of cutters has substantially the same impact toughness as the
second type of cutters.
2. A method according to claim 1, wherein the cutters of the second
type each comprise a table of polycrystalline diamond bonded to a
substrate, the table of polycrystalline diamond defining a matrix
of interstices containing a catalysing material, the interstices of
the matrix located within a volume close to a working surface of
the cutter being substantially free of catalysing material.
3. A method according to claim 2, wherein the volume close to the
working surface extends to a depth of at least about 0.25 mm from
the working surface.
4. A method according to claim 3, wherein the volume close to the
working surface extends to a depth of at least about 0.5 mm from
the working surface.
5. A method of designing a fixed cutter drill bit comprising
determining a layout of cutter locations in which cutters are to be
positioned upon a bit body, determining a likely wear rate for at
least the cutters provided at some of the cutter locations,
selecting a desired wear profile for the bit, and using the
determined likely wear rates to determine the abrasion resistance
of the cutter to be mounted at each cutter location to achieve the
desired wear profile, wherein all the cutters have substantially
the same impact toughness.
6. A method according to claim 5, wherein the desired wear profile
is of generally flat form.
7. A method according to claim 5, wherein the desired wear profile
includes a region of relatively low wear rate bounded by regions of
higher wear rates.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Patent Application No. 60/234,075 filed Sep. 20, 2000, and from
U.S. Provisional Patent Application No. 60/281,054 filed Apr. 2,
2001.
BACKGROUND OF INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a method of designing a fixed
cutter rotary drill bit for use in the drilling of wellbores.
[0004] 2. Description of the Related Art
[0005] It is known that certain parts of a fixed cutter rotary
drill bit wear at a faster rate than other parts thereof. Such
variations in wear have been countered, in the past, by providing
the drill bit with additional cutters in the high wear areas
thereof. In the past, drill bit designs were compromised because
cutters having high abrasion resistance had low impact toughness
and cutters having high impact toughness had low abrasion
resistance. As a result of this trade-off such placement of the
cutters may improve the abrasion resistance of the drill bit, but
it is likely that the overall drilling efficiency is not optimized
due to relatively poor impact toughness.
[0006] It is an object of the invention to provide a drill bit
whereby the operating efficiency of the bit can be maintained
whilst providing a bit having a desired wear profile, and to
provide a method for designing such a drill bit and provide high
abrasion resistance while maintaining impact toughness.
SUMMARY OF INVENTION
[0007] According to the present invention there is provided a
method for designing a fixed cutter drill bit comprising
determining a layout of cutter locations in which cutters are to be
positioned upon a bit body, determining the likely wear rate for at
least the cutters provided in some of the cutter locations and
using the determined likely wear rates to determine whether to
mount a cutter of a first type of relatively low abrasion
resistance or a cutter of a second type of a relatively high
abrasion resistance in each cutter location. The impact toughness
of all the cutters is substantially the same.
[0008] The method of the invention is advantageous in that the
positions of the cutter locations can be optimized whilst achieving
an acceptable overall wear rate for the bit.
[0009] The cutters of the second type conveniently each comprise a
table of polycrystalline diamond bonded to a substrate, the table
of polycrystalline diamond defining a matrix of interstices
containing a catalyzing material, the interstices of the matrix
located within a volume close to a working surface of the cutter
being substantially free of catalysing material. The volume
preferably extends to a depth of at least around 0.25 mm from the
working surface.
[0010] According to another aspect of the invention there is
provided a method of designing a fixed cutter drill bit comprising
determining a layout of cutter locations in which cutters are to be
positioned upon a bit body, determining a likely wear rate for at
least the cutters provided at some of the cutter locations,
selecting a desired wear profile for the bit, and using the
determined likely wear rates to determine the abrasion resistance
of the cutter to be mounted at each cutter location to achieve the
desired wear profile.
[0011] The invention also relates to a fixed cutter drill bit
designed in accordance with the methods defined hereinbefore.
BRIEF DESCRIPTION OF DRAWINGS
[0012] The invention will further be described, by way of example,
with reference to the accompanying drawings.
[0013] FIG. 1 is a perspective view of a drill bit designed in
accordance with an embodiment of the invention.
[0014] FIG. 2 is a diagrammatic sectional view of a cutter of the
drill bit of FIG. 1.
[0015] FIG. 3 is a diagrammatic view illustrating the structure of
part of the cutters of FIG. 2.
[0016] FIGS. 4 to 7 are diagrammatic representations of wear
profiles.
[0017] FIGS. 8 and 9 are diagrammatic views of two further drill
bits.
DETAILED DESCRIPTION
[0018] The fixed cutter drill bit illustrated in FIG. 1 comprises a
bit body 10 having a leading face 12 and a shank 14 to permit the
drill bit to be secured to the remainder of a drill string. The bit
body 10 is intended to be rotated, in use, about an axis of
rotation 16.
[0019] Upstanding from the leading face 12 are a plurality of
blades 18 upon which a plurality of cutters 20 are mounted. As
shown in FIG. 2, each cutter 20 comprises a table 22 of
polycrystalline diamond bonded to a tungsten carbide substrate 24.
Each cutter 20 is manufactured using a known technique involving
exposing diamond powder, a catalyst material and a tungsten carbide
substrate to high temperature, high pressure conditions to cause
the diamond powder to undergo a structural change, becoming
polycrystalline diamond, and to cause the polycrystalline diamond
to bond to the substrate.
[0020] It has been found that where the catalyzing material used in
the manufacture of the cutters is cobalt, removal of the catalyst
material from a part of the cutter close to a working surface
thereof results in the abrasion resistance of the cutter improving.
FIG. 3 illustrates part of a cutter so treated. In FIG. 3, the
polycrystalline diamond 26 defines a matrix of interstices 28
containing the catalyzing material used in the formation of the
polycrystalline diamond and used in the bonding of the
polycrystalline diamond to the substrate. The interstices 28
located within a volume 34 close to a working surface 32 of the
diamond 26 have been rendered substantially free of catalyzing
material 30 by leaching the catalyzing material 30 from the volume
34. In the arrangement of FIG. 3, the volume 34 extends over the
full cross-sectional area of the polycrystalline diamond, and
extends to a depth D of approximately 0.25 mm from the working
surface 32.
[0021] Although leaching is the currently preferred technique for
rendering the interstices free of catalyzing material, other
techniques may be used. For example, the catalyzing material may be
forced to undergo a structural change to take an alternative form
which does not have a catalyzing effect, or may be chemically
reacted to form a substance which does not have a catalyzing
effect.
[0022] In accordance with the invention, a layout or arrangement of
cutter locations in which the cutters 20 are to be mounted on the
bit body 10 is chosen, and the likely wear rate to which each of
the cutters 20 is to be exposed is determined. The likely wear rate
for each location may be determined using, for example, a computer
modelling technique, or alternatively may be derived from
measurements taken from a similar, used drill bit. Using the
determined likely wear rate information, either a cutter 20a of a
first type of a relatively low abrasion resistance, or a cutter 20b
of a second type having a relatively high abrasion resistance
manufactured as described hereinbefore is chosen for each cutter
location in order to achieve a desired wear profile.
[0023] FIGS. 4 to 7 illustrate a range of possible profiles. In
each drawing, the full line 36 denotes the profile that would be
achieved if all cutter locations were occupied by cutters 20a of
the first type. In FIGS. 4 and 5, the broken line 38 illustrates
the modification to the wear profile achieved by using cutters 20b
of the second type rather than cutters 20a of the first type in a
region 40 of the bit.
[0024] FIG. 6 illustrates an arrangement which makes use of cutters
of a third type of higher abrasion resistance than the cutters 20b
of the second type. These cutters are similar to the cutters 20b of
the second type but are treated to remove the catalyst material to
a greater depth, for example to a depth of 0.5 mm, from the working
surface. In FIG. 6, the cutters 20b of the second type are located
in regions 40 and the cutters of the third type are location in a
region 42.
[0025] In the profiles of FIGS. 4 to 6, the use of cutters 20b of
the second type, and in FIG. 6 the use of cutters of the third
type, serves to flatten the profile, increasing the uniformity with
which the cutters on the bit wear, thereby permitting the working
life of the bit to be increased. FIG. 7 illustrates an alternative
profile for a bit where the region which conventionally would have
the highest wear rate has a lower wear rate than the remainder of
the bit. It is thought that this may be beneficial in providing
bits of good stability, directional control, and rate of
progress.
[0026] In the hereinbefore described manufacturing process for
improving wear resistance, as the wear resistance of a cutter
improves, its ability to withstand impacts is substantially
retained. However, because a thin wear-resistance lip is often
desirously formed at the cutting edge cutters of the second and
third types, they may be more suitably used in in cutter locations
which are protected against impact. This is because the lip, which
is believed to increase drilling efficiency, may become chipped
during impact. FIGS. 8 and 9 illustrate, diagrammatically, two
rotary drill bits of the type having a plurality of primary cutters
and a plurality of secondary cutters, the secondary cutters being
protected, at least to some extend, against chippage of the lip by
the presence of the primary cutters.
[0027] In FIG. 8, the drill bit 44 defines a plurality of blades
46, each blade 46 having mounted thereon a plurality of cutters 20.
The cutters 20 are arranged in two rows 48, 50 on each blade 46.
The first row 48 comprises a row of primary cutters 20a of the
first type. The second row 50 comprises secondary cutters 20b of
the second type. The secondary cutters are each provided
immediately behind an associated primary cutter, and so are
protected by the primary cutters from impacts.
[0028] The arrangement of FIG. 9 differs from that of FIG. 8 in
that the secondary cutters are mounted upon separate blades from
the primary cutters.
[0029] It will be appreciated that, in order to provide a bit of
good abrasion resistance and good impact resistance, it may in some
circumstances be desirable to position some cutters of the first
type within the regions 40, 42 of FIGS. 4 to 7 to protect the
cutters of the second type from lip chippage.
[0030] Although specific embodiments of the invention have been
described hereinbefore, it will be appreciated that various changes
may be made without departing from the scope of the appended
claims. The present invention has also been described in particular
relation to the drawings attached hereto, it should be understood
that other and further modifications apart from those shown or
suggested herein, may be made within the scope and spirit of the
present invention.
* * * * *