U.S. patent application number 11/225380 was filed with the patent office on 2006-04-27 for drilling with mixed tooth types.
This patent application is currently assigned to Halliburton Energy Services, Inc.. Invention is credited to John G. Dennis.
Application Number | 20060086537 11/225380 |
Document ID | / |
Family ID | 32593840 |
Filed Date | 2006-04-27 |
United States Patent
Application |
20060086537 |
Kind Code |
A1 |
Dennis; John G. |
April 27, 2006 |
Drilling with mixed tooth types
Abstract
A rotary-cutter Earth-penetrating bit in which a given track of
bottom hole is attacked by inserts of two different types, e.g.
chisel-shaped and pointed, wider and narrower, higher and shorter,
and/or of different materials. The different types of inserts can
both be included within a single row of a cone.
Inventors: |
Dennis; John G.; (Lakewood,
CO) |
Correspondence
Address: |
GROOVER & HOLMES
BOX 802889
DALLAS
TX
75380-2889
US
|
Assignee: |
Halliburton Energy Services,
Inc.
Carrollton
TX
|
Family ID: |
32593840 |
Appl. No.: |
11/225380 |
Filed: |
September 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10325650 |
Dec 19, 2002 |
6942045 |
|
|
11225380 |
Sep 13, 2005 |
|
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Current U.S.
Class: |
175/57 ; 175/374;
175/426 |
Current CPC
Class: |
E21B 10/16 20130101 |
Class at
Publication: |
175/057 ;
175/374; 175/426 |
International
Class: |
E21B 10/00 20060101
E21B010/00 |
Claims
1-21. (canceled)
22. A rotary-cutter rock-penetrating drill bit, comprising: a
plurality of rotatable elements, each bearing thereon first and
second pluralities of inserted cutting elements which incrementally
remove rock rock as the drill bit is rotated and advanced; wherein
at least some of said first and second cutting elements remove rock
from a shared location, and wherein said first and second inserted
cutting elements have different material compositions.
23. The bit of claim 22, wherein at least one single row of inserts
on at least one rotatable element includes ones of said first and
ones of said second cutting elements.
24. The bit of claim 22, wherein said cutting elements comprise
diamond-loaded cermets.
25. The bit of claim 22, wherein said cutting elements are inserted
into said rotatable element.
26. The bit of claim 22, wherein said rotatable elements are
attached through a rotary joint to arms which are affixed to a body
having an API thread.
27. The bit of claim 22, comprising only three of said rotatable
elements.
28-32. (canceled)
33. A method for rotary drilling, comprising the actions of: (a.)
applying torque and axial force to a bit according to claim 22,
while (b.) pumping drilling fluid through a drill string to which
said bit is connected.
34. A rotary drilling system, comprising: a bit according to claim
22; a drill string which is connected to conduct drilling fluid to
said bit from a surface location; and a rotary drive which rotates
at least part of said drill string together with said bit.
35. A rotary drilling system, comprising: a bit according to claim
22; a drill string which is connected to conduct drilling fluid to
said bit from a surface location; and a rotary drive which rotates
at least part of said drill string together with said bit.
36. A rotary drilling system, comprising: a bit according to claim
22; a drill string which is connected to conduct drilling fluid to
said bit from a surface location; and a rotary drive which rotates
at least part of said drill string together with said bit.
37. A rotary drilling system, comprising: a bit according to claim
22; a drill string which is connected to conduct drilling fluid to
said bit from a surface location; and a rotary drive which rotates
at least part of said drill string together with said bit.
38-45. (canceled)
46. A cutter for a roller-cone-type rock-penetrating drill bit,
comprising: a tapered cutter body bearing a gage row, and at least
one other row of cutting elements; wherein said other row includes
first and second different types of said cutting elements, wherein
said first type and said second type have different cermet
compositions.
47. The cutter of claim 46, wherein said body is steel, and said
cutting elements are cermet inserts.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] The present invention relates to earth-penetrating drill
bits, and particularly to rotary-cone rotating bits such as are
used for drilling oil and gas wells.
[0002] Background: Rotary Drilling
[0003] Oil wells and gas wells are drilled by a process of rotary
drilling. In a conventional drill rig, as seen in Figure ? a drill
bit 50 is mounted on the end of a drill string 52, made of many
sections of drill pipe, which may be several miles long. At the
surface a rotary drive turns the string, including the bit at the
bottom of the hole, while drilling fluid (or "mud") is pumped
through the string by very powerful pumps 54.
[0004] The bit's teeth must crush or cut rock, with the necessary
forces supplied by the "weight on bit" (WOB) which presses the bit
down into the rock, and by the torque applied at the rotary drive.
While the WOB may in some cases be 100,000 pounds or more, the
forces actually seen at the drill bit are not constant: the rock
being cut may have harder and softer portions (and may break
unevenly), and the drill string itself can oscillate in many
different modes. Thus the drill bit must be able to operate for
long periods under high stresses in a remote environment.
[0005] When the bit wears out or breaks during drilling, it must be
brought up out of the hole. This requires a process called
"tripping": a heavy hoist pulls the entire drill string out of the
hole, in stages of (for example) about ninety feet at a time. After
each stage of lifting, one "stand" of pipe is unscrewed and laid
aside for reassembly (while the weight of the drill string is
temporarily supported by another mechanism). Since the total weight
of the drill string may be hundreds of tons, and the length of the
drill string may be tens of thousands of feet, this is not a
trivial job. One trip can require tens of hours and is a
significant expense in the drilling budget. To resume drilling the
entire process must be reversed. Thus the bit's durability is very
important, to minimize round trips for bit replacement during
drilling.
[0006] Background: Drill Bits
[0007] One of the most important types of rotary drill bits
commonly used in drilling for oil and gas is the roller cone bit,
seen in FIG. 6. In such bits, a rotating cone 82 with teeth 84 on
its outer surface is mounted on an arm 46 of the drill bit body.
The arms 46 (typically three) extend downhole from the bit body,
and each carries a spindle on which the cone is mounted with
heavy-duty bearings. The support arms are roughly parallel to the
drill string, but the spindles are angled to point radially inward
and downhole.
[0008] As the drill bit rotates, the roller cones roll on the
bottom of the hole. The weight-on-bit forces the downward pointing
teeth of the rotating cones into the formation being drilled,
applying a compressive stress which exceeds the yield stress of the
formation, and thus inducing fractures. The resulting fragments are
flushed away from the cutting face by a high flow of drilling
fluid.
[0009] The drill string typically rotates at 150 rpm or so, and
sometimes as high as 1000 rpm if a downhole motor is used, while
the roller cones themselves typically rotate at a slightly higher
rate. At this speed the roller cone bearings must each carry a very
bumpy load which averages a few tens of thousands of pounds, with
the instantaneous peak forces on the bearings several times larger
than the average forces. This is a demanding task.
[0010] Background: Selection of Insert Shapes
[0011] A wide variety of shapes have been used for the inserts of
roller-cone-type bits. These include, for example, hemispherical
inserts, where the exposed surface is generally spherical; pointed
inserts, which are also axisymmetric but rise higher, for a given
insert diameter, than hemispherical inserts would; chisel-shaped
inserts, having a "crest" orientation; and more complex shapes.
Insert design and selection is itself a complex and highly
developed area of engineering.
[0012] Proper insert selection depends on the formation being
drilled. Very hard formations will typically be drilled with
hemispherical inserts; sandstone formations will typically use
pointed inserts; and shaly formations will commonly use
chisel-shaped inserts.
Drilling with Mixed Tooth Types
[0013] The present application discloses bits, rigs, and methods
for rock penetration, using different types of teeth for a single
bottomhole track.
[0014] For example, in one class of embodiments, a single row of
one or more cones contains both pointed inserts and chisel-shaped
inserts.
[0015] In another class of embodiments, the same bottomhole track
is attacked by inserts of different diameters. (For example, a
single non-gage row of a single cone can include inserts of
different diameters.) In another class of embodiments, the same
bottomhole track is attacked by inserts of different heights. (For
example, a single non-gage row of a single cone can include inserts
which protrude upward to different heights.) This can
advantageously be implemented, for example, using larger-diameter
inserts for the ones which have greater protrusion from the
cone.
[0016] In another class of embodiments, the same bottomhole track
is attacked by inserts of different materials. (For example, a
single row of a single cone can include inserts with different
carbide compositions.) One particularly advantageous implementation
of this is to combine different carbide compositions with different
profiles, so that the inserts with the more "aggressive" profile
have a more abrasion-resistant composition, and the inserts with a
more "conservative" profile have a more fracture-resistant
composition. (Another advantageous implementation is just the
opposite, where the inserts with the more "aggressive" profile have
a more fracture-resistant composition, and the inserts with a more
"conservative" profile have a more abrasion-resistant
composition.)
[0017] The disclosed innovations, in various embodiments, provide
one or more of at least the following advantages, many related to
efficiencies: [0018] Physical efficiencies as related to failing
multiple types of rock with one cutting structure containing
multiple features/shapes/extensions/diameters; [0019] Aggressive as
related to addressing multiple types of rock
(soft/hard/sandy/shaley/etc) with one cutting structure (containing
multiple features/shapes/extensions/diameters); [0020] Durability
as related to addressing multiple types of rock
(soft/hard/sandy/shaley/etc) with one cutting structure (containing
multiple features/shapes/extensions/diameters); [0021] Mechanical
efficiencies (WOB/RPM) through related to failing multiple types of
rock with one cutting structure (containing multiple
features/shapes/extensions/diameters).
[0022] A further expected advantage, of some embodiments at least,
is improved resistance to secondary tooth fractures induced by a
first tooth fracture: when more durable teeth are mixed with less
durable teeth, the more durable teeth are expected to be more
resistant to secondary fracture.
[0023] It should also be noted that the advantageous obtained by
the disclosed innovations can be used in various ways: for example,
increased durability can be traded off for higher ROP in a given
formation, or vice versa.
BRIEF DESCRIPTION OF THE DRAWING
[0024] The disclosed inventions will be described with reference to
the accompanying drawings, which show important sample embodiments
of the invention and which are incorporated in the specification
hereof by reference, wherein:
[0025] FIGS. 1 and 2 show the cone structure of a first sample
embodiment, from two different perspectives.
[0026] FIG. 3 shows the cone structure of a second sample
embodiment. This embodiment also combines conical and chisel-shaped
inserts in a single row, but note that the orientations of the
chisel-shaped inserts are not the same as in the embodiment of
FIGS. 1 and 2.
[0027] FIG. 4 illustrates some other combinations of different
types of teeth in a single row.
[0028] FIG. 5 shows an exemplary drill rig.
[0029] FIG. 6 shows a conventional rotary cone (or "roller-cone")
drill bit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] The numerous innovative teachings of the present application
will be described with particular reference to the presently
preferred embodiment (by way of example, and not of
limitation).
[0031] The present application teaches combination or mixing of
different types of inserts--whether shapes, diameters, extensions,
and or materials--within the same cone row, within other rows on
the same cone, or in conjunction rows on with other cones which
impact a shared bottom hole track--in an effort to enhance drilling
performance, either by improved rates of penetration or durability
or a combination of both. These features can be beneficial in
transitional formations, mixed lithology or uniform lithology. By
varying the above insert variables in a given row or a combination
of rows the crater shape, bottom hole pattern, and or effective
insert penetration can be enhanced through extra action on bottom,
prefracturing, and/or kerfing the formation, thus combining insert
attribute efficiencies to provide performance improvement.
[0032] Naturally the intermesh clearances need to be adequate for
the insert with the most protrusion in each row, and for the insert
with the greatest width.
[0033] It is also preferable to check the bit's balance, as
described in U.S. Pat. Nos. 6,213,225 and 6,095,262, both of which
are hereby incorporated by reference. (Use of multiple tooth types
in a single row means that more effort will be required to input
the full data needed for the evaluations and optimizations
described in these patents, but those procedures are expected to be
particularly beneficial in this context.) Manufacturing confusion
is another area where the use of the disclosed inventions may
require additional care, so that each insert is placed with exactly
the desired DFA, DFB and angle.
[0034] A design method which can be useful in connection with these
different insert shapes is to maximize insert row clearances to
maximize insert diameter, and then altering insert parameters in a
give row.
Embodiments Combining Differently-Shaped Inserts
[0035] The present application discloses bits, rigs, and methods
for rock penetration, using different types of teeth for a single
bottomhole track.
First Sample Embodiment
[0036] For example, in one class of embodiments, a single row of
one or more cones contains both pointed inserts and chisel-shaped
inserts. In other classes of embodiments, inserts of different
diameters can be combined, or inserts of different heights, or even
inserts of different materials.
[0037] FIGS. 1A and 1B show the cone structure of a first sample
embodiment, from two different perspectives. In this embodiment the
alternating conical and chisel shaped inserts in a drive row have
the same diameter, are made of the same material, and have the same
extension. (As will be obvious to those skilled in the art, the
"conical" inserts typically do not have a sharp tip, but have a
rounded or spherical tip on a conical base.)
[0038] Note that the gage row itself, in this embodiment, does not
have a mixture of tooth types. Instead, the driver row (the next
row inboard of the gage row), and optionally some of the inner
rows, have a mixture of different tooth types.
[0039] Also visible are gage buttons, on the backface of the cone,
which help protect this area.
[0040] It is believed that the combination of axisymmetric and
chisel-shaped inserts may be particularly synergistic, in that the
axisymmetric insert can efficiently initiate failure of rock which
is then efficiently removed by the chisel-shaped insert.
Second Sample Embodiment
[0041] FIG. 3 shows the cone structure of a second sample
embodiment. This embodiment also combines conical and chisel-shaped
inserts in a single row, but note that the orientations of the
chisel-shaped inserts are not the same as in the embodiment of
FIGS. 1 and 2.
Other Mixed-Shape Embodiments
[0042] The specific combination of conical- and chisel-shaped
inserts is particularly attractive, but many other combinations of
different shapes are possible. For example, inserts which have
multiple flats, e.g. in an asymmetric shape like that of a cape
chisel, can be combined with conical inserts, or which
chisel-shaped inserts.
Embodiments Combining Inserts of Unequal Protrusion/Extension
[0043] In another class of embodiments, the same bottomhole track
is attacked by inserts of different heights. (For example, a single
non-gage row of a single cone can include inserts which protrude
upward to different heights.) The inserts with higher protrusions
(greater heights) can accelerate cutting for as long as they last,
which the inserts with lower protrusions provide a more durable and
conservative complement.
[0044] FIG. 4 illustrates some other combinations of different
types of teeth in a single row. For simplicity in illustrating the
alternation or variation of teeth, the geometry has been
transformed so that the inserts are shown in a straight line. Top
and section views are given.
[0045] In the example shown, a sequence of four teeth is
illustrated: chisel-shaped insert 410, low-protrusion
large-diameter "fallback" insert 420, another chisel-shaped insert
410, and a conical insert 430 which has the same height as the
chisel-shaped inserts 410. In this example the full-height conical
insert 430 cooperates with the chisel-shaped inserts 410 to achieve
rapid cutting in tractable formations, and the more durable insert
420 provides increased survivability. Preferably the more durable
insert 420 is given a different composition, e.g. of a more
abrasion-resistant carbide. Thus this figure illustrates unequal
protrusion (or extension, i.e. height above the surface of the
cone), as well as unequal diameters, different materials, and
combination of more than two different types in the same row.
Embodiments Combining Inserts of Unequal Diameter
[0046] In another class of embodiments, the same bottomhole track
is attacked by inserts of different diameters. (For example, a
single non-gage row of a single cone can include inserts of
different diameters.) This has the advantage that durability can be
maximized by large-diameter inserts, without the design
inconvenience and crowding which would result from use of
large-diameter inserts only.
[0047] FIG. 4, as noted above, illustrates an example of mixed
insert diameters.
Embodiments Combining Inserts of Unequal Diameter and Unequal
Protrusion
[0048] FIG. 4, as noted above, illustrates an example of mixed
insert types where both diameter AND protrusion are different
between two of the types. As noted above, this can be a synergistic
combination.
[0049] The example shown combines a large-diameter low-height
insert with a smaller-diameter and greater-protrusion insert.
However, the opposite combination can also have advantages: a
larger diameter can be given to the insert which has greater
protrusion, to reduce the risk of breakage from scraping-related
forces.
Embodiments Combining Inserts of Different Materials
[0050] In another class of embodiments, the same bottomhole track
is attacked by inserts of different materials. (For example, a
single row of a single cone can include inserts with different
carbide compositions.) One particularly advantageous implementation
of this is to combine different carbide compositions with different
profiles, so that the inserts with the more "aggressive" profile
have a more abrasion-resistant composition, and the inserts with a
more "conservative" profile have a more fracture-resistant
composition. (Another advantageous implementation is just the
opposite, where the inserts with the more "aggressive" profile have
a more fracture-resistant composition, and the inserts with a more
"conservative" profile have a more abrasion-resistant
composition.)
[0051] FIG. 4, as noted above, illustrates this class of
embodiments also: note that insert 420 is hatched differently than
the others, to show that it has a different composition.
Combining Inserts of Different Shapes and Different Materials
[0052] It is believed that the combination of axisymmetric and
chisel-shaped inserts may be particularly synergistic, in that the
axisymmetric insert can efficiently initiate failure of rock which
is then efficiently removed by the chisel-shaped insert. In this
example of differentiated tooth functionality, both compositions
and shapes of the two types of teeth can be separately
optimized.
[0053] In another class of embodiments, the same bottomhole track
is attacked by inserts of different materials. (For example, a
single row of a single cone can include inserts with different
carbide compositions.) One particularly advantageous implementation
of this is to combine different carbide compositions with different
profiles, so that the inserts with the more "aggressive" profile
have a more abrasion-resistant composition, and the inserts with a
more "conservative" profile have a more fracture-resistant
composition. (Another advantageous implementation is just the
opposite, where the inserts with the more "aggressive" profile have
a more fracture-resistant composition, and the inserts with a more
"conservative" profile have a more abrasion-resistant
composition.)
Combining Inserts which Differ in More than Two Ways
[0054] In further alternative embodiments, at least two types of
teeth can be made different in three or more respects. For example,
chisel-shaped teeth which perform scraping in soft formations can
optionally be combined with blunt conical teeth with larger
diameters and less protrusion, for maximum survivability when hard
horizons are encountered.
Combining More than Two Types of Inserts
[0055] In further alternative embodiments, it is contemplated that
three of more types of inserts can be combined in the same row (or
hitting the same bottom-hole track). For example, chisel-shaped
teeth which perform scraping in soft formations can optionally be
combined with blunt conical teeth with larger diameters and less
protrusion, for maximum survivability when hard horizons are
encountered.
[0056] According to a disclosed class of innovative embodiments,
there is provided: A rotary-cutter rock-penetrating drill bit,
comprising: a plurality of rotatable elements, each bearing thereon
first and second types of cutting elements which incrementally
remove rock as the drill bit is rotated and advanced; wherein at
least some of said first and second types of cutting elements
remove rock from a shared bottom-hole location, and wherein said
first and second types of cutting elements are differently
optimized for different respective formation types.
[0057] According to another disclosed class of innovative
embodiments, there is provided: A rotary-cutter rock-penetrating
drill bit, comprising: a plurality of cutting elements which
incrementally remove rock from a cutting face as the drill bit is
rotated and advanced; wherein at least one track of said cutting
face is impinged on by first and second types of said cutting
elements having different shapes.
[0058] According to another disclosed class of innovative
embodiments, there is provided: A rotary-cutter rock-penetrating
drill bit, comprising: a plurality of cutting elements which
incrementally remove rock from a cutting face as the drill bit is
rotated and advanced; wherein at least one track of said cutting
face is impinged on by first and second different types of said
cutting elements, wherein said first type is more axisymmetric than
said second type.
[0059] According to another disclosed class of innovative
embodiments, there is provided: A rotary-cutter rock-penetrating
drill bit, comprising: a plurality of cutting elements which
incrementally remove rock from a cutting face as the drill bit is
rotated and advanced; wherein at least one track of said cutting
face is impinged on by first and second types of said cutting
elements, and wherein cutting elements of said first type protrude
deeper into said cutting face than said elements of said second
type.
[0060] According to another disclosed class of innovative
embodiments, there is provided: A rotary-cutter rock-penetrating
drill bit, comprising: a plurality of rotatable elements, each
bearing thereon first and second pluralities of inserted cutting
elements which incrementally remove rock as the drill bit is
rotated and advanced; wherein at least some of said first and
second cutting elements remove rock from a shared location, and
wherein said first and second inserted cutting elements have
different diameters.
[0061] According to another disclosed class of innovative
embodiments, there is provided: A rotary-cutter rock-penetrating
drill bit, comprising: a plurality of rotatable elements, each
bearing thereon first and second pluralities of inserted cutting
elements which incrementally remove rock as the drill bit is
rotated and advanced; wherein at least some of said first and
second cutting elements remove rock from a shared location, and
wherein said first and second inserted cutting elements have
different material compositions.
[0062] According to another disclosed class of innovative
embodiments, there is provided: A method for rotary drilling,
comprising the actions of: applying torque and downhole force to a
weight-on-bit to a bit as described in one of the six preceding
paragraphs, while pumping drilling fluid through a drill string to
which said bit is connected.
[0063] According to another disclosed class of innovative
embodiments, there is provided: A rotary drilling system,
comprising: a bit a bit as described in one of the seven preceding
paragraphs, a drill string which is connected to conduct drilling
fluid to said bit from a surface location; and a rotary drive which
rotates at least part of said drill string together with said
bit.
[0064] According to another disclosed class of innovative
embodiments, there is provided: A cutter for a roller-cone-type
rock-penetrating drill bit, comprising: a tapered cutter body
bearing a gage row, and at least one other row of cutting elements;
wherein said other row includes first and second different types of
said cutting elements, wherein said first type is more axisymmetric
than said second type.
[0065] According to another disclosed class of innovative
embodiments, there is provided: A cutter for a roller-cone-type
rock-penetrating drill bit, comprising: a tapered cutter body
bearing a gage row, and at least one other row of cutting elements;
wherein said other row includes first and second different types of
said cutting elements, wherein said first type has a larger
diameter than said second type.
[0066] According to another disclosed class of innovative
embodiments, there is provided: A cutter for a roller-cone-type
rock-penetrating drill bit, comprising: a tapered cutter body
bearing a gage row, and at least one other row of cutting elements;
wherein said other row includes first and second different types of
said cutting elements, wherein said first type protrudes higher
from said body than does said second type.
[0067] According to another disclosed class of innovative
embodiments, there is provided: A cutter for a roller-cone-type
rock-penetrating drill bit, comprising: a cutter body bearing a
gage row, and at least one other row of cutting elements; wherein
said other row includes first and second different types of said
cutting elements, wherein said first type and said second type have
different cermet compositions.
Modifications and Variations
[0068] As will be recognized by those skilled in the art, the
innovative concepts described in the present application can be
modified and varied over a tremendous range of applications, and
accordingly the scope of patented subject matter is not limited by
any of the specific exemplary teachings given. Some contemplated
modifications and variations are listed below, but this brief list
does not imply that any other embodiments or modifications are or
are not foreseen or foreseeable.
[0069] In various embodiments, various ones of the disclosed
inventions can be applied not only to bits for drilling oil and gas
wells, but can also be adapted to other rotary drilling
applications (especially deep drilling applications, such as
geothermal, geomethane, or geophysical research).
[0070] In various embodiments, various ones of the disclosed
inventions can be applied not only to pure drill bits (as
illustrated), but also to other roller-cone-type rock-removal
machines, such as hole reamers, coring bits, or even to large
tunnel-boring machines.
[0071] In various embodiments, various ones of the disclosed
inventions can also be applied to air-cooled mining-type drill
bits.
[0072] In various embodiments, various ones of the disclosed
inventions can be applied not only to top-driven and table-driven
configurations, but can also be applied to other rotary drilling
configurations, such as motor drive.
[0073] In a less preferred class of alternative embodiments, the
many proposed variations in tooth type can also be applied to
milled cutters.
[0074] In another class of alternative embodiments, the many
proposed variations in tooth type can also be implemented with a
matrix cone structure in which the varying tooth types are formed
integrally with the cermet cone.
[0075] In many of the embodiments described above, the gage row
itself does not include multiple types of insert. However, in other
embodiments, different types of teeth can be combined in the gage
row too (and preferably also in the driver row and/or other
non-gage rows). Insert selection in the gage row is somewhat more
constrained than elsewhere, because of the need to trim the gage
surface as well as the hole bottom; but subject to this constraint,
the disclosed innovations can also be adapted to gage row
design.
[0076] In another class of embodiments, the same bottomhole track
is attacked by inserts of different diameters. (For example, a
single non-gage row of a single cone can include inserts of
different diameters.) In another class of embodiments, the same
bottomhole track is attacked by inserts of different heights. (For
example, a single non-gage row of a single cone can include inserts
which protrude upward to different heights.) This can
advantageously be implemented, for example, using larger-diameter
inserts for the ones which have greater protrusion from the
cone.
[0077] In another class of embodiments, the same bottomhole track
is attacked by inserts of different materials. (For example, a
single row of a single cone can include inserts with different
carbide compositions.) One particularly advantageous implementation
of this is to combine different carbide compositions with different
profiles, so that the inserts with the more "aggressive" profile
have a more abrasion-resistant composition, and the inserts with a
more "conservative" profile have a more fracture-resistant
composition. (Another advantageous implementation is just the
opposite, where the inserts with the more "aggressive" profile have
a more fracture-resistant composition, and the inserts with a more
"conservative" profile have a more abrasion-resistant composition.)
Additional general background on drilling, which helps to show the
knowledge of those skilled in the art regarding implementation
options and the predictability of variations, may be found in the
following publications, all of which are hereby incorporated by
reference: Baker, A PRIMER OF OILWELL DRILLING (5.ed. 1996);
Bourgoyne et al., APPLIED DRILLING ENGINEERING (1991); Davenport,
HANDBOOK OF DRILLING PRACTICES (1984); DRILLING (Australian
Drilling Industry Training Committee 1997); FUNDAMENTALS OF ROTARY
DRILLING (ed. W. W. Moore 1981); Harris, DEEPWATER FLOATING
DRILLING OPERATIONS (1972); Maurer, ADVANCED DRILLING TECHNIQUES
(1980); Nguyen, OIL AND GAS FIELD DEVELOPMENT TECHNIQUES: DRILLING
(1996 translation of 1993 French original); Rabia, OILWELL DRILLING
ENGINEERING/PRINCIPLES AND PRACTICE (1985); Short, INTRODUCTION TO
DIRECTIONAL AND HORIZONTAL DRILLING (1993); Short, PREVENTION,
FISHING & REPAIR (1995); UNDERBALANCED DRILLING MANUAL (Gas
Research Institute 1997); the entire PetEx Rotary Drilling Series
edited by Charles Kirkley, especially the volumes entitled MAKING
HOLE (1983), DRILLING MUD (1984), and THE BIT (by Kate Van Dyke,
4.ed. 1995); the SPE reprint volumes entitled "Drilling,"
"Horizontal Drilling," and "Coiled-Tubing Technology"; and the
Proceedings of the annual IADC/SPE Drilling Conferences from 1990
to date; all of which are hereby incorporated by reference.
[0078] None of the description in the present application should be
read as implying that any particular element, step, or function is
an essential element which must be included in the claim scope: THE
SCOPE OF PATENTED SUBJECT MATTER IS DEFINED ONLY BY THE ALLOWED
CLAIMS. Moreover, none of these claims are intended to invoke
paragraph six of 35 USC section 112 unless the exact words "means
for" are followed by a participle.
[0079] The claims as filed are intended to be as comprehensive as
possible, and NO subject matter is intentionally relinquished,
dedicated, or abandoned.
* * * * *