U.S. patent application number 14/138180 was filed with the patent office on 2014-07-03 for percussion drill bit with conical cutting elements.
This patent application is currently assigned to SMITH INTERNATIONAL, INC.. The applicant listed for this patent is SMITH INTERNATIONAL, INC.. Invention is credited to Lokesh Bhatia, Robert H. Slaughter, JR., Angelo Spedale.
Application Number | 20140182939 14/138180 |
Document ID | / |
Family ID | 51015877 |
Filed Date | 2014-07-03 |
United States Patent
Application |
20140182939 |
Kind Code |
A1 |
Bhatia; Lokesh ; et
al. |
July 3, 2014 |
PERCUSSION DRILL BIT WITH CONICAL CUTTING ELEMENTS
Abstract
A percussion drill bit for drilling a borehole. The drill bit
includes a bit body having a bit face disposed on an axial end
portion thereof. First and second cutting elements are disposed on
the bit face. A cutting plane is defined in tangential contact with
crest portion of the first and second cutting elements. A third
cutting element on the bit face is at least partially positioned
between the first and second cutting elements. The third cutting
element is at least partially conical, and a crest portion of the
third cutting element is offset from the cutting plane.
Inventors: |
Bhatia; Lokesh; (Houston,
TX) ; Slaughter, JR.; Robert H.; (Spring, TX)
; Spedale; Angelo; (Cypress, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SMITH INTERNATIONAL, INC. |
Houston |
TX |
US |
|
|
Assignee: |
SMITH INTERNATIONAL, INC.
Houston
TX
|
Family ID: |
51015877 |
Appl. No.: |
14/138180 |
Filed: |
December 23, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61746765 |
Dec 28, 2012 |
|
|
|
Current U.S.
Class: |
175/57 ;
175/420.1; 175/420.2 |
Current CPC
Class: |
E21B 10/36 20130101 |
Class at
Publication: |
175/57 ;
175/420.1; 175/420.2 |
International
Class: |
E21B 10/36 20060101
E21B010/36; E21B 1/00 20060101 E21B001/00 |
Claims
1. A percussion drill bit for drilling a borehole, comprising: a
bit body having a bit face; first and second cutting elements on
the bit face, the first and second cutting elements defining a
cutting plane in tangential contact with a crest portion of each of
the first and second cutting elements; and a conical cutting
element on the bit face and positioned at least partially between
the first and second cutting elements, the conical cutting element
having a crest portion offset from the cutting plane.
2. The percussion drill bit of claim 1, the crest portion of the
conical cutting element extending beyond the cutting plane by a
distance up to about 70% of a total height of the conical cutting
element as measured from the bit face.
3. The percussion drill bit of claim 1, the crest portion of the
conical cutting element being below the cutting plane by a distance
up to about 25% of a total height of the conical cutting element as
measured from the bit face.
4. The percussion drill bit of claim 1, the first and second
cutting elements being semi-round top cutting elements.
5. The percussion drill bit of claim 1, the first and second
cutting elements being at least partially conical.
6. The percussion drill bit of claim 1, a radius of curvature of
the crest portion of the conical cutting element being less than a
radius of curvature of the crest portions of the first and second
cutting elements.
7. The percussion drill bit of claim 1, the first and second
cutting elements being circumferentially offset from one
another.
8. The percussion drill bit of claim 7, the first and second
cutting elements being positioned in a circumferential gage row on
the bit face.
9. The percussion drill bit of claim 1, the first and second
cutting elements being in first and second circumferential rows of
cutting elements, respectively, the first circumferential row of
cutting elements being radially outward relative to the second
circumferential row of cutting elements.
10. The percussion drill bit of claim 1, at least one of the first,
second, or conical cutting elements comprising diamond.
11. A percussion drill bit for drilling a borehole, comprising: a
bit body having a bit face; first and second semi-round top cutting
elements in an outer circumferential row on the bit face, the first
and second semi-round top cutting elements defining a cutting plane
in tangential contact with a crest portion of the first cutting
element and a crest portion of the second cutting element; and a
third cutting element on the bit face at least partially
overlapping the outer circumferential row, the third cutting
element being at least partially conical, and a crest portion of
the third cutting element extending beyond the cutting plane by a
distance up to about 70% of a total height of the third cutting
element as measured from the bit face.
12. The percussion drill bit of claim 11, a radius of curvature of
the crest portion of the third cutting element being less than a
radius of curvature of the crest portions of the first and second
cutting elements.
13. The percussion drill bit of claim 12, a ratio of the radius of
curvature of the crest portion of the third cutting element to a
diameter of the third cutting element being between about 0.12:1
and about 0.30:1 and a ratio of a radius of curvature of the crest
portion of the first and second cutting elements to a diameter of
the first and second cutting elements being between about 0.4:1 and
about 0.7:1.
14. The percussion drill bit of claim 11, at least one of the
first, second, or third cutting elements comprising diamond.
15. The percussion drill bit of claim 11, the outer circumferential
row being a gage row.
16. A method for drilling a borehole, comprising: running a
percussion hammer drill bit into a borehole, the percussion hammer
drill bit including: a bit body having a bit face; first and second
cutting elements on the bit face and defining a cutting plane in
tangential contact with a crest portion of the first cutting
element and a crest portion of the second cutting element; and a
third cutting element on the bit face and positioned at least
partially between the first and second cutting elements, the third
cutting element being at least partially conical and a crest
portion of the third cutting element being offset from the cutting
plane; and contacting a formation with the first, second, and third
cutting elements to extend the borehole.
17. The method of claim 16, wherein contacting the formation
comprises: moving the bit body back and forth axially within the
borehole; and indexing the bit body about a longitudinal axis
extending therethrough.
18. The method of claim 16, wherein the first and second cutting
elements are: in a same circumferential gage row on the bit face;
or in different circumferential rows on the bit face.
19. The method of claim 16, wherein the crest portion of the third
cutting element extends beyond the cutting plane by a distance up
to about 70% of a total height of the third coning element as
measured from the bit face.
20. The method of claim 16, wherein the crest portion of the third
cutting element is below the cutting plane by a distance up to
about 25% of a total height of the third cutting element as
measured from the bit face.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of, and priority to,
U.S. Patent Application No. 61/746,765, filed on Dec. 28, 2012 and
entitled "PERCUSSION DRILL BIT WITH CONICAL CUTTING ELEMENTS,"
which application is expressly incorporated herein by this
reference in its entirety.
BACKGROUND
[0002] In drilling a borehole in the earth--such as for the
recovery of hydrocarbons or for other applications--a drill bit may
be connected to the lower end of a drill string that includes a
plurality of end-to-end connected drill pipe sections. The drill
bit is rotated by rotating the drill string at the surface and/or
by actuation of downhole motors or turbines. With weight applied to
the drill string, the rotating drill bit engages the earthen
formation causing the drill bit to cut through the formation
material by either abrasion, fracturing, or shearing action,
thereby forming the borehole.
[0003] There are several types of drill bits which may be used,
including percussion hammer bits, roller cone bits, fixed cutter
bits, and drag bits. In percussion hammer drilling operations, the
drill bit may be mounted to the lower end of the drill string, and
the drill string may move the drill bit back and forth axially to
impact the earth to crush, break, and loosen formation material. To
promote efficient penetration, the percussion hammer drill bit may
be "indexed" to fresh earthen formations for each subsequent
impact. Indexing is achieved by rotating the percussion hammer
drill bit between each axial impact of the bit with the earth. In
such operations, the mechanism for penetrating the earthen
formation is of an impacting nature, rather than shearing. The
impacting and rotating percussion hammer drill bit engages the
earthen formation and proceeds to form the borehole along a path
and toward a target zone.
[0004] The cost of drilling a borehole may be proportional to the
length of time it takes to drill the borehole to the desired depth
and location. The drilling time, in turn, is greatly affected by
the number of times the drill bit is changed in order to reach the
desired depth and location. This is the case because each time the
drill bit is changed, the entire drill string--which may be miles
long--is retrieved and each removed from the borehole. Once the
drill string has been retrieved and removed, and the new drill bit
installed, the drill bit is lowered to the bottom of the borehole
on the drill string, which is again constructed by securing each
drill string section end-to-end with an adjacent drill string
section. This process, known as a trip of the drill string, entails
considerable time, effort, and expense.
SUMMARY
[0005] Embodiments disclosed herein generally relate to cutting
elements. More particularly, embodiments of the present disclosure
relate to cutting elements for percussion hammer drill bits. More
specifically still, some embodiments disclosed herein relate to
conical cutting elements for percussion hammer drill bits.
[0006] A percussion drill bit for drilling a borehole is disclosed.
The drill bit includes a bit body having a bit face. First and
second cutting elements are positioned on the bit face and definine
a cutting plane. The cutting plane is in tangential contact with
crest portions of each of the first and second cutting elements. A
third cutting element on the bit face is a conical cutting element
and is at least partially between the first and second cutting
elements. The conical cutting element includes a crest portion
offset from the cutting plane.
[0007] In another embodiment, a percussion drill bit includes a bit
body having a bit face. First and second semi-round cutting
elements positioned in an outer circumferential row on the bit
face, and define a cutting plane. The cutting plane is in
tangential contact with crest portions of the first and second
cutting elements. A third cutting element on the bit face at least
partially overlaps the outer circumferential row and is at least
partially conical. A crest portion of the third, conical cutting
element extends beyond the cutting plane by a distance up to about
70% of a total height of the third cutting element as measured from
the bit face.
[0008] A method for drilling a borehole is disclosed. The method
includes running a percussion hammer drill bit into a borehole. The
percussion drill bit includes a bit body having a bit face with
first, second, and third cutting elements thereon. A cutting plane
is defined in tangential contact with crest portions of the first
and second cutting elements. The third cutting element is
positioned at least partially between the first and second cutting
elements, is at least partially conical, and has a crest portion
that is offset from the cutting plane. The first, second, and third
cutting elements contact a formation to extend the borehole.
[0009] This summary is provided to introduce a selection of
concepts that are further described below in the detailed
description. This summary is not intended to identify key or
essential features of the claimed subject matter, nor is it
intended to be used as an aid in limiting the scope of the claimed
subject matter.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1A depicts a perspective view of an illustrative
percussion hammer drill bit, according to one or more embodiments
of the present disclosure.
[0011] FIG. 1B depicts a top view of the percussion hammer drill
bit shown in FIG. 1A, according to one or more embodiments of the
present disclosure.
[0012] FIG. 2A depicts a profile view of a portion of the
percussion hammer drill bit, according to one or more embodiments
of the present disclosure.
[0013] FIG. 2B depicts an enlarged, partial profile view of the
percussion hammer drill bit shown in FIG. 2A, according to one or
more embodiments of the present disclosure.
[0014] FIGS. 2C and 2D depict enlarged, partial profile views of
the percussion hammer drill bit shown in FIG. 2B, according to one
or more embodiments of the present disclosure.
[0015] FIG. 3A depicts a profile view of a portion of a percussion
hammer drill bit, according to one or more embodiments of the
present disclosure.
[0016] FIG. 3B depicts an enlarged, partial profile view of the
percussion hammer drill bit shown in FIG. 3A, according to one or
more embodiments of the present disclosure.
[0017] FIG. 4A depicts a profile view of a portion of a percussion
hammer dull according to one or more embodiments of the present
disclosure.
[0018] FIG. 4B depicts an enlarged, partial profile view of the
percussion hammer drill bit shown in FIG. 4A, according to one or
more embodiments of the present disclosure.
[0019] FIG. 5A depicts a profile view of a portion of a percussion
hammer drill bit, according to one or more embodiments of the
present disclosure.
[0020] FIG. 5B depicts an enlarged, partial profile view of the
percussion hammer drill bit shown in FIG. 5A, according to one or
more embodiments of the present disclosure.
DETAILED DESCRIPTION
[0021] FIGS. 1 and 2 depict perspective and top views,
respectively, of an illustrative percussion hammer drill bit 100,
according to one or more embodiments of the present disclosure. The
percussion hammer drill bit 100 includes a bit body 102 having a
central axis ("bit axis") 104 extending therethrough. The drill bit
100 may be indexed (i.e., rotated) about the bit axis 104 during
drilling operations.
[0022] A bit face 106 may be disposed on an axial end portion of
the bit body 102. The bit face 106 may include a plurality of
inserts or cutting elements 110 disposed thereon. The bit face 106
may include inner and outer regions 112, 114. The inner region 112
may include the radially innermost region of the drill bit 100, and
may extend from the bit axis 104 to the outer region 114. The outer
region 114 may extend from the inner region 112 to a skirt region
122. Optionally, the skirt region 122 may be about parallel to the
bit axis 104.
[0023] The outer region 114 may include a circumferential gage row
126 having gage cutting elements 136. In the illustrated
embodiment, there is a plurality of gage cutting elements 136. The
circumferential gage row 126 may be the outermost radial row on the
bit face 106. The gage cutting elements 136 may be
circumferentially offset from one another in the gage row. The gage
cutting elements 136 may be adapted to cut the corner of the
borehole. Stated another way, the gage cutting elements 136 may cut
an outermost, or largest radius portion of the borehole bottom
and/or borehole sidewall during drill operations. Accordingly, the
gage cutting elements 136 may maintain the diameter or gage of the
borehole.
[0024] The outer region 114 (or potentially the inner region 112)
may include a circumferential adjacent-to-gage row 128 having one
or more adjacent-to-gage cutting elements 138. A plurality of
adjacent-to-gage cutting elements 138 may be circumferentially
offset from one another in the adjacent to gave row 128 and
positioned radially inward from the gage cutting elements 136 in
the gage row 126. The adjacent-to-gage cutting elements 138 may be
adapted to cut the bottom of the borehole in some embodiments. As
discussed in more detail herein, one or more additional rows 130 of
cutting elements 140 may also be positioned radially inward from
the adjacent-to-gage row 128 at the inner region 112 or the outer
region 114. The one or more additional rows 130 of cutting elements
140 may be adapted to gouge and remove formation material from the
bottom of the borehole in some embodiments.
[0025] The cutting elements 136, 138, 140 may be semi-round top
("SRT") cutting elements having a hemispherical shape. A ratio of
the radius of curvature of a crest portion of the cutting elements
136, 138, 140 to the diameter of the cutting elements 136, 138, 140
may range from about 0.3:1 to about 1:1. For instance, such a ratio
may range from a low of about 0.3:1, about 0.4:1, or about 0.5:1 to
a high of about 0.6:1, about 0.7:1, about 0.8:1, or more. For
example, the ratio of the radius of curvature to the diameter may
be between about 0.4:1 and about 0.7:1. As used herein, "crest
portion" refers to the portion of a cutting element that is most
distal relative to the bit face 106 (e.g., the tip or apex) and/or
the portion of a cutting element that is likely to initially
contact the formation during drilling operations.
[0026] In at least one embodiment, the cutting elements 110 from
different circumferential rows (e.g., rows 126, 128, 130) may be
radially offset from one another with little to no overlap. In
another embodiment, the cutting elements 110 from one
circumferential row may at least partially radially overlap with
the cutting elements 110 from a different circumferential row. The
degree of radial overlap of the cutting elements 110 in adjacent
circumferential rows may be characterized by the ratio of the
radial overlap distance to the radial span distance of the
overlapping cutting elements. As used herein, "radial overlap
distance" refers to the radial distance over which two adjacent
cutting elements 110 overlap. "Radial span distance" refers to the
radial distance spanned or covered by the two adjacent overlapping
cutting elements. Thus, "radial overlap ratio" refers to the ratio
of the radial overlap distance to the radial span distance. The
radial overlap ratio of adjacent cutting elements may range from
about 0.05 to about 0.8 in some embodiments. For instance, in some
embodiments the radial overlap ratio may range from a low of about
0.05, about 0.1, about 0.15, about 0.2, or about 0.25 to a high of
about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, or more. For
example, the radial overlap ratio may be between about 0.1 and
about 0.5, between about 0.1 and about 0.3, or between about 0.05
and about 0.2.
[0027] The greater the radial overlap ratio, the greater the degree
of overlap of a cutting element 110 in a first circumferential row
(e.g., row 126) with another cutting element 110 in an adjacent
second circumferential row (e.g., row 128). As this degree of
overlap increases, it ma become easier for fractures created in the
formation by the cutting elements 110 in the first circumferential
row to communicate and connect with the fractures created in the
formation by the cutting elements 110 in the adjacent second
circumferential row. This communication between different fractures
in the formation may make it easier to generate chips from the
formation. Moreover, an increase in the degree of overlap may
reduce the load on the set of cutting elements 110 that is
responsible for the formation of these chips. U.S. Patent
Application Publication No. 2009/0255735, which is assigned to the
assignee of the present disclosure and is hereby incorporated by
this reference in its entirety, further describes some aspects of
the relationship between the fracture capability of one
circumferential row of cutting elements to an adjacent
circumferential row of cutting elements in a percussion hammer
drill bit.
[0028] One or more conical cutting elements 142, 144, 146 may be
disposed on the bit face 106 of the drill bit 100. In some
embodiments, conical cutting elements 142, 144, 146 may be disposed
in separate rows. Accordingly, although three rows of conical
cutting elements 142, 144, 146 are shown in FIG. 1, more or fewer
conical cutting elements 142, 144, 146 may be disposed on the bit
face 106 of the drill bit 100 without departing from the scope of
the present disclosure. Additionally, any of the conical cutting
elements 142, 144, 146 (or a corresponding row thereof) may be
disposed at least partially in or between any of the
circumferential rows 126, 128, 130.
[0029] Thus, the first conical cutting element 142 may be disposed
in the gage row 126, in the adjacent-to-gage row 128, or between
the gage row 126 and the adjacent-to-gage row 128. The second
conical cutting element 144 may be disposed in the adjacent-to-gage
row 128, in the row 130, or between the adjacent-to-gage row 128
and the row 130. The third conical cutting element 146 may be
disposed in the row 130, disposed in a more radially inner row of
cutting elements, or between the row 130 and an inner row (or the
axis 104).
[0030] The conical cutting elements 142, 144, 146 may have a
conical or frustoconical shape. Such shape may be sharper or more
pointed relative to SRT cutting elements (e.g., cutting elements
136, 138, 140). An outer surface of the conical cutting elements
142, 144, 146 may be oriented at an angle with respect to a
longitudinal axis through the conical cutting element 142, 144,
146. In some embodiments, such an angle may range from about
15.degree. to about 85.degree.. For instance, the angle may range
from a low of about 10.degree., about 15.degree., about 20.degree.,
about 25.degree., about 40.degree., or about 45.degree. to a high
of about 50.degree., about 55.degree., about 60.degree., about
65.degree., about 70.degree., about 75.degree., or more. For
example, the angle may be between about 20.degree. and about
40.degree., between about 10.degree. and about 50.degree., or
between about 40.degree. and about 60.degree..
[0031] A crest portion of the conical cutting elements 142, 144,
146 may be sharp or flat. In some embodiments, the crest portion
may have a radius of curvature that is less than the radius of
curvature of the crest portion of the cutting elements 136, 138,
140. A ratio of the radius of curvature of the crest portion of the
cutting elements 142, 144, 146 to the diameter of the cutting
elements 142, 144, 146 may be between about 0.05:1 to about 0.5:1.
For instance, the ratio of the radius of curvature of the crest
portion to the diameter may range from a low of about 0.05:1, about
0.10:1, or about 0.15:1 to a high of about 0.20:1 about 0.25:1,
about 0.30:1, or more. For example, the ratio of the radius of
curvature to the diameter may be between about 0.12:1 and about
0.30:1 or between about 0.14:1 and about 0.25:1. According to one
or more embodiments of the present disclosure, the conical cutting
elements described herein may be similar to those described in U.S.
patent application Ser. Nos. 61/441,319, 13/370,734, 61/499,851,
and 13/370,862, all of which are assigned to the present assignee
and are incorporated herein by this reference in their
entireties.
[0032] Turning now to FIG. 2A, a profile view of a portion of a
percussion hammer drill bit 200 is illustrated according to one or
more embodiments of the present disclosure. The percussion hammer
drill bit 200 may be similar or the same as the percussion hammer
drill bit 100 disclosed with reference to FIGS. 1A and 1B. Thus,
the discussion with respect to FIGS. 1A and 1B may be equally
applicable to the embodiment illustrated in FIG. 2A.
[0033] The percussion hammer drill bit 200 may include a bit body
202 having a central bit axis 204 extending therethrough. The drill
bit 200 may be indexed about the bit axis 204 during drilling
operations. A bit face 206 may be disposed on an axial end portion
of the bit body 202, and may include an inner region 212 and an
outer region 214. In some embodiments, the inner region 212 may
extend from the bit axis 204 to about 50% of an outermost radius
208 of percussion hammer drill bit 200. The outer region 214 may
extend from the inner region 212 to the outermost radius 208 of the
percussion hammer drill bit 200. In other embodiments, the inner
region 212 may extend more or less than about 50% of the outermost
radius 208 of the percussion hammer drill bit 200.
[0034] The inner region 212 may include a cone region 216, and the
outer region 214 may include a shoulder region 218, a gage region
220, a skirt region 222, or some combination of the foregoing. The
cone region 216 may include the radially innermost region of the
drill bit 200 extending generally from the bit axis 204 to the
shoulder region 218. The cone region 216 may have any suitable
shape, and may be generally concave in some embodiments. In other
embodiments, the cone region 216 may be generally convex, planar,
otherwise shaped, or some combination of the foregoing. The
shoulder region 218 may be positioned radially-outward from the
cone region 216. The shoulder region 218 may be generally convex,
generally convex, generally planar, or otherwise shaped, or have
some combination of the foregoing. The gage region 220 may be
positioned radially outward from the shoulder region 218, and the
skin region 222 may be positioned radially outward from the gage
region 220. The skirt region 222 may be generally parallel to the
bit axis 204 in some embodiments.
[0035] The gage region 220 may include a circumferential gage row
226 having a plurality of gage cutting elements 236. The
circumferential gage row 226 is the outermost radial row on the bit
face 206, and where there are multiple gage cutting elements 236,
they may be equally or unequally circumferentially offset from one
another the gage row 226. The gage cutting elements 236 may be
adapted to cut the corner of the borehole to maintain the diameter
or gage of the borehole.
[0036] The shoulder region 218 may include a circumferential
adjacent-to-gage row 228 having a second plurality of cutting
elements (i.e., adjacent-to-gage cutting elements 238). The
adjacent-to-gage cutting elements 238 may be equally or unequally
circumferentially offset from one another in the adjacent to gage
row 228 and positioned radially inward from the gage cutting
elements 236 in the gage row 226. The adjacent-to-gage cutting
elements 238 may be adapted to cut the bottom of the borehole in
some embodiments.
[0037] The shoulder region 218 may also include one or more rows
positioned radially inward from the adjacent-to-gage row 228 (see
row 330 in FIG. 3A). The cone region 216 may include one or more
rows 232 (e.g., three rows 232a, 232b, 232c) positioned radially
inward from the rows in the shoulder region 218, if any. The rows
232 may include a third plurality of cutting elements 240 (e.g.,
inner row cutting elements 240a, 240b, 240c). The inner row cutting
elements 240 may be adapted to gouge and remove formation material
from the bottom of the borehole.
[0038] The cutting elements 236, 238, 240 may be SRT) cutting
elements having a hemispherical shape. A ratio of the radius of
curvature of the crest portion of the cutting elements 236, 238,
240 to the diameter of the cutting elements 236, 238, 240 may range
from a low of about 0.3:1, about 0.4:1, or about 0.5:1 to a high of
about 0.6:1, about 0.7:1, about 0.8:1, or more. For example, the
ratio of the radius of curvature to the diameter may be between
about 0.4:1 and about 0.7:1.
[0039] In at least one embodiment, the cutting elements 210 from
different circumferential rows (e.g., rows 226, 228, 232) may be
radially offset from one another with little to no overlap. In
another embodiment, the cutting elements 210 from one
circumferential row may at least partially radially overlap with
the cutting elements 210 from a different circumferential row. The
degree of radial overlap of the cutting elements 210 in adjacent
circumferential rows may be characterized by the ratio of the
radial overlap distance to the radial span distance of the
overlapping cutting elements. The radial overlap ratio of adjacent
cutting elements may range from a low of about 0.05, about 0.1,
about 0.15, about 0.2, or about 0.25 to a high of about 0.3, about
0.4, about 0.5, about 0.6, about 0.7, or more. For example, the
radial overlap ratio may be between about 0.1 and about 0.5,
between about 0.1 and about 0.3, or between about 0.05 and about
0.2.
[0040] The greater the radial overlap ratio, the greater the degree
of overlap of a cutting element 210 in a first circumferential row
(e.g., gage row 225) with another cutting element 210 in an
adjacent second circumferential row (e.g., adjacent-to-gage row
228). As this degree of overlap increases, fractures created in the
formation by the cutting elements 210 in the first circumferential
row may more easily communicate and connect with the fractures
created in the formation by the cutting elements 210 in the
adjacent second circumferential row. This communication between
different fractures in the formation may make it easier to generate
chips from the earthen formation. Moreover, an increase in the
degree of overlap may reduce the load on the set of cutting
elements that is responsible for the formation of these chips.
[0041] Optionally, one or more conical cutting elements 242, 244,
246 may be disposed on the bit face 206 of the drill bit 200. In
some embodiments, the conical cutting elements 242, 244, 246 may be
disposed at different radial positions, such there are one or more
first conical cutting elements 242, one or more second conical
cutting elements 244, and one or more third conical cutting
elements 246. Thus, although three conical cutting elements 242,
244, 246 are shown in FIG. 2A, more or less conical cutting
elements may be disposed circumferentially around the corresponding
bit face 206 of the drill bit 200 without departing from the scope
of the present disclosure. Any of first, second, and third conical
cutting elements 242, 244, 246 may be disposed at least partially
in or between any of the circumferential rows 226, 228, 232.
[0042] The first, second, and third conical cutting elements 242,
244, 246 may have a conical or frustoconical shape as disclosed
herein. In some embodiments, an outer surface of the conical
cutting elements 242, 244, 246 may be oriented at an angle with
respect to a longitudinal axis through the conical cutting element
242, 244, 246. The angle may range from a low of about 10.degree.,
about 15.degree., about 20.degree., about 25.degree., about
40.degree., or about 45.degree. to a high of about 50.degree.,
about 55.degree., about 60.degree., about 65.degree., about
70.degree., about 75.degree., or more. For example, the angle may
be between about 10.degree. and about 40.degree., between about
20.degree. and about 50.degree., or between about 40.degree. and
about 60.degree..
[0043] A crest portion of the conical cutting elements 242, 244,
246 may be sharp, flat, or curved. For instance, the crest portion
may have a radius of curvature that is less than the radius of
curvature of the crest portion of the cutting elements 236, 238,
240. A ratio of the radius of curvature of the crest portion of the
cutting elements 242, 244, 246 to the diameter of the cutting
elements 242, 244, 246 may range from a low of about 0.05:1, about
0.10:1, or about 0.15:1 to a high of about 0.20:1, about 0.25:1,
about 0.30:1, or more. For example, the ratio of the radius of
curvature to the diameter may be between about 0.12:1 and about
0.30:1 or between about 0.14:1 and about 0.25:1.
[0044] The first conical cutting element 242 may be disposed in the
gage row 226, in the adjacent-to-gage row 228, or between the gage
row 226 and the adjacent-to-gage row 228 (as shown). The second
conical cutting element 244 may be disposed in the adjacent-to-gage
row 228, in a row in the shoulder region 218, in one of the rows
232 in the cone region 216, between the adjacent-to-gage row 228
and a row in the shoulder region 218, or between the
adjacent-to-gage row 228 (or other row in the shoulder region 218)
and the rows 232 in the cone region 216 (as shown). The third
conical cutting element 246 may be disposed in a row in the
shoulder region 218, in one of the rows 232 in the cone region 216,
between the adjacent-to-gage row 228 (or another row in the
shoulder region 218) and the rows 232 in the cone region 216, or
between rows 232 of the cone region 216 (as shown).
[0045] FIG. 2B depicts an enlarged, partial profile view of a
cutting profile of the percussion hammer drill bit 200, according
to one or more embodiments. Referring to FIGS. 2B and 2C, a cutting
plane 211 may be in tangential contact with a crest portion 237 of
the gage cutting elements 236 and a crest portion 239 of the
adjacent-to-gage cutting elements 238. As used herein, "cutting
plane" refers to a plane that is in tangential contact with the
crest portions of two cutting elements in adjacent rows (e.g., rows
236, 238) or between the crest portions of two cutting elements in
the same circumferential row.
[0046] As shown, a crest portion 243 of first conical cutting
element 242 may be in tangential contact with the cutting plane
211. When the crest portion 243 of the first conical cutting
element 242 is in tangential contact with the cutting plane 211,
the first conical cutting element 242 may impact the formation at
substantially the same time as the gage cutting elements 236 and
the adjacent-to-gage cutting elements 238. As a result, the first
conical cutting element 242 may create fractures in the formation
at substantially the same depth as the gage cutting elements 236
and the adjacent-to-gage cutting elements 238.
[0047] Even when the crest portion 243 of the first conical cutting
element 242 is in tangential contact with the cutting plane 211,
the first conical cutting element 242 may create additional
fractures in the formation that are capable of communicating with
the fractures created in the formation by the gage cutting elements
236 and the adjacent-to-gage cutting elements 238. As a result,
generating a chip from the formation may become easier when the
crest portion 243 of the first conical cutting element 242 is in
tangential contact with the cutting plane 211.
[0048] In at least one embodiment, the crest portion 243 of first
conical cutting element 242 may be offset from the cutting plane
211. For example, the crest portion 243 of first conical cutting
element 242 may extend beyond the cutting plane 211 by a distance
213. The distance 213 may range from about 1% to about 80% of the
height of the first conical element 242 in some embodiments. For
instance, the distance 213 may range from a low of about 1%, about
3%, about 5%, about 10%, or about 20% to a high of about 30%, about
40%, about 50%, about 60%, about 70%, or more of the total height
of the first conical cutting element 242 as measured from the bit
face 206. For example, the distance 213 may be up to about 5%,
about 10%, about 20%, about 30%, about 40%, about 50%, about 60%,
about 70% or more of the total height of the first conical cutting
element 242. The distance 213 may also be between about 1% and
about 10%, between about 1% and about 20%, between about 10% and
about 20%, or between about 3% and about 50% of the total height of
the .first conical cutting element 242.
[0049] When the crest portion 243 of first conical cutting element
242 extends beyond the cutting plane 211 by the distance 213, the
first conical cutting element 242 may pre-fracture the formation by
impacting the formation before the gage cutting elements 236 and/or
the adjacent-to-gage cutting elements 238. In addition, when the
crest portion 243 of first conical cutting element 242 extends
beyond the cutting plane 211 by the distance 213, the first.
conical cutting element 242 may create a fracture in the formation
that is deeper than the fractures created by the gage cutting
elements 236/or and the adjacent-to-gage cutting elements 238. As
such, the first conical cutting element 242 may create a deeper
fracture contour or "groove" in the formation than that created by
the gage cutting elements 236 andior the adjacent-to-gage cutting
elements 238. This groove of pre-fractured formation material may
facilitate the communication between the fractures created by the
gage cutting elements 236 and the adjacent-to-gage cutting elements
238, thereby making it easier to generate chips from the formation
during drilling operations. Moreover, this groove of pre-fractured
formation material may provide a stress relieved area or a free
face toward which the fractures created by the gage cutting.
elements 236 and the adjacent-to-gage cutting elements 238 may
easily propagate. As used herein, "free face" refers to an
unconfined portion of the formation that provides room for the
expansion and movement of fractured rock. The free face created by
the first conical cutting element 242 may provide a stress relieved
area that fractured rock may move toward, thereby using less energy
for the fracture generation process.
[0050] In at least one embodiment, the crest portion 243 of first
conical cutting element 242 may be below the cutting plane 211. For
example, the crest portion 243 of first conical cutting element 242
may be below the cutting plane 211 by a distance 215. The distance
215 may range about 0.5% to about 50% of the total height of the
first conical cutting element 242. For instance, the distance 215
may range from a low of about 0.5%, about 1%, about 2%, about 4%,
or about 6% to a high of about 8%, about 10%, about 15%, about 20%,
about 25%, or more of the total height of the first conical cutting
element 242 as measured from the bit face 206. For example, the
distance 215 may be between about 0.5% and about 3%, between about
1% and about 5%, or between about 1% and about 10%.
[0051] When the crest portion 243 of first conical cutting element
242 is below the cutting plane 211, the first conical cutting
element 242 may not initially engage the formation during drilling.
Rather, the first conical cutting element 242 may serve as a
back-up to the gage cutting elements 236 and/or the
adjacent-to-gage cutting elements 238, and the first conical
cutting element 242 may engage the formation after the gage cutting
elements 236 andlor the adjacent-to-gage cutting elements 238 have
been subjected to substantial wear, thus lowering the cutting plane
211, or when impacted into the formation a distance that allows the
first conical cutting element 242 to also contact the formation. In
another embodiment, the first conical cutting element 242 may
engage the formation after a substantial kerf develops between the
gage row 226 and the adjacent-to-gage row 228 due to the formation
being highly resistant to fracture.
[0052] FIG. 2C depicts an enlarged, partial profile view of a
portion of a cutting profile of a percussion hammer drill bit 200,
according to one or more embodiments of the present disclosure. A
cutting plane 217 may be defined as being in tangential contact
with the crest portion 239 of the adjacent-to-gage cutting elements
238 and the crest portion 241 of the inner row cutting elements 240
in a row 232. As shown, the crest portion 245 of the second conical
cutting element 244 may be in tangential contact with the cutting
plane 217. When the crest portion 245 of the second conical cutting
element 244 is in tangential contact with the cutting plane 217,
the second conical cutting element 244 may impact the formation at
substantially the same time as the adjacent-to-gage cutting
elements 238 and/or the inner row cutting elements 240. As a
result, the second conical cutting element 244 may create fractures
in the formation at substantially the same depth as the
adjacent-to-gage cutting elements 238 and/or the inner row cutting
elements 240.
[0053] Even when the crest portion 245 of second conical cutting
element 244 is in tangential contact with the cutting plane 217,
the second conical cutting element 244 may create additional
fractures in the formation that are capable of communicating with
the fractures created in the formation by the adjacent-to-gage
cutting elements 238 and/or the inner row cutting elements 240. As
a result, generating a chip from the formation may become easier
when the crest portion 245 of second conical cutting element 244 is
in tangential contact with the cutting plane 217.
[0054] In at least one embodiment, the crest portion 245 of second
conical cutting element 244 may be offset from the cutting plane
217. For example, the crest portion 245 of second conical cutting
element 244 may extend beyond the cutting plane 217 by the distance
219. The distance 219 may range from about 1% to about 80% of the
total height of the second conical cutting element 244. For
instance, the distance 219 may range from a low of about 1%, about
3%, about 5%, about 10%, or about 20% to a high of about 30%, about
40%, about 50%, about 60%, about 70% or more of the total height of
the second conical cutting element 244, as measured from the bit
face 206. For example, the distance 219 may be up to about 5%,
about 10%, about 20%, about 30%, about 40%, about 50%, about 60%,
about 70%, or more of the total height of the second conical
cutting element 244. The distance 219 may also be between about 1%
and about 10%, between about 1% and about 20%, between about 10%
and about 20%, or between about 3% and about 50% of the total
height of the second conical cuffing element 244.
[0055] When the crest portion 245 of second conical cutting element
244 extends beyond the cutting plane 217 by the distance 219, the
second conical cutting element 244 may pre-fracture the formation
by impacting the formation before the adjacent-to-gage cutting
elements 238 and/or the inner row cutting elements 240. In
addition, when the crest portion 245 of second conical cutting
element 244 extends beyond the cutting plane 217 by the distance
219, the second conical cutting element 244 may create a fracture
in the formation that is deeper than the fractures created by the
adjacent-to-gage cutting elements 238 andlor the inner row cutting
elements 240. As such, the second conical cutting element 244 may
create a deeper fracture contour or groove in the formation than
that created by the adjacent-to-gage cutting elements 238 and/or
the inner row cutting elements 240. This groove of pre-fractured
formation material may facilitate the communication between the
fractures created by the adjacent-to-gage cutting elements 238
and/or the inner row cutting elements 240, thereby making it easier
to generate chips from the formation during chilling operations.
Moreover, this groove of pre-fractured formation material may
provide a stress relieved area or a free face toward which the
fractures created h the adjacent-to-gage cutting elements 238
and/or the inner row cutting elements 240 may easily propagate. The
free face created by the second conical cutting element 244 may
provide a stress relieved area that fractured rock may move toward,
thereby using less energy for the fracture generation process.
[0056] In at least one embodiment, the crest portion 245 of second
conical cutting element 244 may be below the cutting plane 217. For
example, the crest portion 245 of second conical cutting element
244 may be below the cutting plane 217 by a distance 221. The
distance 221 may range from about 0.5% to about 50% of the total
height of the second conical cutting element 244 as measured from
the bit face 206. For instance, the distance 221 may range from a
low of about 0.5%, about 1%, about 2%, about 4%, or about 6% to a
high of about 8%, about 10%, about 15%, about 20%, about 25% or
more of the total height of the second conical cutting element 244.
For example, the distance 221 may be between about 0.5% and about
3%, between about 1% and about 5%, or between about 1% and about
10%.
[0057] When the crest portion 245 of second conical cutting element
244 is below cutting plane 217, the second conical cutting element
244 may not initially engage the formation during drilling. Rather,
the second conical cutting element 244 may serve as a back-up to
the adjacent-to-gage cutting elements 238 and/or the inner row
cutting elements 240, and the second conical cutting element 244
may engage the formation after the adjacent-to-gage cutting
elements 238 and/or the inner row cutting elements 240 have been
subjected to substantial wear, thus lowering the cutting plane 217.
In another embodiment, the second conical cutting element 244 may
engage the formation after a substantial kerf develops between the
adjacent-to-gage row 228 and the row 230 due to the formation being
highly resistant to fracture, or when adjacent-to-gage cutting
elements 238 and/or gage cutting elements 236 have penetrated the
earthen formation to a depth allowing the second conical cutting
element 244 to engage the formation.
[0058] FIG. 2D depicts an enlarged, partial profile view of a
portion of a cutting profile of a percussion hammer drill bit 200,
according to one or more embodiments of the present disclosure. A
cutting plane 223 may be defined as being in tangential contact
with the crest portions 241 of the inner row cutting elements 240a
in the row 232a and the inner row cutting elements 240b in the row
232b. The inner row cutting elements 240a, 240b may each be in a
cone region (e.g., cone region 216 of FIG. 2A) in some embodiments.
In other embodiments, the inner row cutting elements 240a, 240b may
be in different regions (e.g., cutting element 240a may be in a
shoulder region 218 while cutting element 240b is in a cone region
216).
[0059] As shown, the crest portion 247 of the third conical cutting
element 246 may be in tangential contact with the cutting plane
223. When the crest portion 247 of the third conical cutting
element 246 is in tangential contact with the cutting plane 223,
the third conical cutting element 246 may impact the formation at
substantially the same time as the inner row cutting elements 240a
in the row 232a and/or the inner row cutting elements 240b in the
row 232b. As a result, the third conical cutting element 246 may
create fractures in the formation at substantially the same depth
as the inner row cutting elements 240a in the row 232a and/or the
inner row cutting elements 240b in the row 232b.
[0060] Even when the crest portion 247 of third conical cutting
element 246 is in tangential contact with the cutting plane 223,
the third conical cutting element 246 may create additional
fractures in the formation that are capable of communicating with
the fractures created in the formation by the inner row cutting
elements 240a in the row 232a and the inner row cutting elements
240b in the row 232b. As a result, generating a chip from the
formation may become easier when the crest portion of third conical
cutting element 246 is in tangential contact with the cutting plane
223.
[0061] In at least one embodiment, the crest portion 247 of third
conical cutting element 246 may be offset from the cutting plane
223. For example, the crest portion 247 of third conical cutting
element 246 may extend beyond the cutting plane 223 by a distance
225. In some embodiments, the distance 225 may range from about 1%
to about 80% of the total height of the third conical cutting
element 246, as measured from the bit face 206. For instance, the
distance 225 may range from a low of about 1%, about 3%, about 5%,
about 10%, or about 20% to a high of about 30%, about 40%, about
50%, about 60%, about 70% or more of the total height of the third
conical cutting element 246. For example, the distance 225 may be
up to about 5%, about 10%, about 20%, about 30%, about 40%, about
50%, about 60%, about 70% or more of the total height of the third
conical cutting element 246. The distance 225 may also be between
about 1% and about 10%, between about 1% and about 20%, between
about 10% and about 20%, or between about 3% and about 50% of the
total height of the third conical cutting element 246.
[0062] When the crest portion 247 of third conical cutting element
246 extends beyond the cutting plane 223 by the distance 225, the
third conical cutting element 246 may pre-fracture the formation by
impacting the formation before the inner row cutting elements 240a
in the row 232a (e.g., in a cone or shoulder region) and/or the
inner row cutting elements 240b in the row 232b (e.g., in the cone
or shoulder region). In addition, when the crest portion 247 of
third conical cutting element 246 extends beyond the cutting plane
223 by the distance 225, the third conical cutting element 246 may
create a fracture in the formation that is deeper than the
fractures created by the inner row cutting elements 240a in the row
232a and/or the inner row cutting elements 240b in the row 232b. As
such, the third conical cutting element 246 may create a deeper
fracture contour or groove in the formation than that created by
the inner row cutting elements 240a and/or the inner row cutting
elements 240b. This groove of pre-fractured formation material may
flicilitate the communication between the fractures created by the
inner row cutting elements 240a and the inner row cutting elements
240b, thereby making it easier to generate chips from the formation
during drilling operations. Moreover, this groove of pre-fractured
formation material may provide a stress relieved area or a free
face toward which the fractures created by the inner row cuffing
elements 240a and/or inner row cutting elements 240b may easily
propagate. The free face created by the third conical cutting
element 246 may provide a stress relieved area that fractured rock
may move toward, thereby using less energy for the fracture
generation process.
[0063] In at least one embodiment, the crest portion 247 of third
conical cutting element 246 may be below cutting plane 223. For
example, the crest portion 247 of third conical cutting element 246
may be below the cutting plane 223 by a distance 227. In some
embodiments, the distance 227 may range from about 0.5% to about
50% of the total height of the third conical cutting element 246
(as measured from the bit face 206). For instance, the distance 227
may range from a low of about 0.5%, about 1%, about 2%, about 4%,
or about 6% to a high of about 8%, about 10%, about 15%, about 20%,
about 25% or more of the total height of the third conical cutting
element 246 (as measured from the bit face 206). For example, the
distance 227 may be between about 0.5% and about 3%, between about
1% and about 5%, or between about 1% and about 10%.
[0064] When the crest portion 247 of third conical cutting element
246 is below cutting plane 223, the third conical cutting element
246 may not initially engage the formation during drilling. Rather,
the third conical cutting element 246 may serve as a back-up to the
inner row cutting elements 240a in the row 232a and/or the inner
row cutting elements 240b in the row 232b, and the third conical
cutting element 246 may engage the formation after the inner row
cutting elements 240a and/or the inner row cutting elements 240b
have been subjected to substantial wear, thus lowering the cutting
plane 223. In another embodiment, the third conical cutting element
246 may engage the formation after a substantial kerf develops
between the row 232a and the row 232b due to the formation being
highly resistant to fracture, or when the depth of penetration of
the cutting elements 240a, 240b allows the third conical cutting
element 246 to contact the formation.
[0065] FIG. 3A depicts a partial profile view of a percussion
hammer drill bit 300, and FIG. 3B depicts an enlarged, partial view
of the percussion hammer drill bit 300 shown in FIG. 3A, according
to one or more embodiments of the present disclosure. A bit face
306 may be disposed on an axial end portion of the bit body 302,
and may include an inner region 312 and an outer region 314. In
some embodiments, the inner region 312 may include a cone region
316, and the outer region 314 may include a shoulder region 318, a
gage region 320, a skirt region 322, or some combination of the
foregoing.
[0066] A conical cutting element 350 may be disposed at least
partially within a circumferential gage row 326. The conical
cutting element 350 is referred to herein as the gage conical
cutting element 350. Because the gage conical cutting element 350
is disposed within circumferential gage row 326, the gage conical
cutting element 350 is adjacent to the sidewall of the borehole
(not shown). In this position, the gage conical cutting element 350
may be adapted to cut and fracture the gage portion of the borehole
during drilling operations.
[0067] A cutting plane 311 may be defined to be in tangential
contact with the crest portion 337 of adjacent gage cutting
elements in the circumferential gage row 326. A crest portion 351
of gage conical cutting element 350 may also be in tangential
contact with the cutting plane 311. When the crest portion 351 of
the gage conical cutting element 350 is in tangential contact with
the cutting plane 311, the gage conical cutting element 350 may
impact the formation at substantially the same time as the gage
cutting elements 336. As a result, the gage conical cutting element
350 may create fractures in the formation at substantially the same
depth as the gage cutting elements 336. When the crest portion 351
of the gage conical cutting element 350 is in tangential contact
with the cutting plane 311, the gage conical cutting element 350
may create additional fractures in the formation that are capable
of communicating with the fractures created in the formation by the
crest portion of the gage cutting elements 336. As a result,
generating a chip from the formation may become easier when the
gage conical cutting element 350 is in tangential contact with the
cutting plane 311.
[0068] In at least one embodiment, the crest portion 351 of gage
conical cutting element 350 may be offset from the cutting plane
311 (as shown). For example, the crest portion 351 of gage conical
cutting element 350 may extend beyond the cutting plane 311 by a
distance 329. In some embodiments, the distance 329 may range from
about 1% to about 80% of the total eight of the gage conical
cutting element 350, as measured from the bit face 306. For
instance, the distance 329 may range from a low of about 1%, about
3%, about 5%, about 10%, or about 20% to a high of about 30%, about
40%, about 50%, about 60%, about 70% or more of the total height of
the gage conical cutting element 350 (as measured from the bit face
306). In another example embodiment, the distance 329 may be up to
about 5%, about 10%, about 20%, about 30%, about 40%, about 50%,
about 60%, about 70% or more of the total height of the gage
conical cutting element 350. The distance 329 may also be between
about 1% and about 10%, between about 1% and about 20%, between
about 10% and about 20%, or between about 3% and about 50% of the
total height of the gage conical cutting element 350.
[0069] When the crest portion 351 of gage conical cutting element
350 extends beyond the cutting plane 311 by the distance 329, the
gage conical cutting element 350 may pre-fracture the formation by
impacting the formation before some, and potentially each, gage
cutting element 336. In addition, the gage conical cutting element
350 may create a fracture in the formation that is potentially
deeper than the fractures created by the gage cutting elements 336.
The gage conical cutting element 350 may pre-split the side and/or
the bottom corner of the borehole, by creating a deeper fracture
contour or groove in the formation than that created by the gage
cutting elements 336. This groove of pre-fractured formation
material may facilitate the communication between the fractures
created by the gage cutting elements 336, thereby making it easier
to generate chips from the formation during drilling operations.
Moreover, this groove of pre-fractured formation material may
provide a stress relieved area or a free face toward which the
fractures created by the gage cutting elements 336 may easily
propagate. The free face created by the gage conical cutting
element 350 may provide a stress relieved area where fractured rock
may move toward, thereby using less energy for the fracture
generation process. In another embodiment, the gage conical cutting
element 350 may be below the cutting plane 311 by a distance
331.
[0070] FIG. 4A depicts a profile view of a portion of a percussion
hammer drill bit 400, and FIG. 4B depicts an enlarged, partial view
of the percussion hammer drill bit 400 shown in FIG. 4A, according
to one or more embodiments of the present disclosure. A bit face
406 may be disposed on an axial end portion of the bit body 402,
and may include an inner region 412 and an outer region 414. In
some embodiments, the inner region 412 may include a cone region
416, and the outer region 414 may include a shoulder region 418, a
gage region 420, a skirt region 422, or some combination of the
foregoing. A plurality of conical cutting elements 452 may be
positioned or otherwise disposed on the bit face 406 of the drill
bit 400. The conical cutting elements 452 may be positioned in one
or more circumferential conical cutting element rows 453. The
various rows 453 may be radially offset on the bit face 406.
[0071] The conical cutting elements 452 in a particular row 453 may
be circumferentially offset from one another. The conical cutting
elements 452 in a given row 453 may, in some embodiments, at least
partially radially overlap with the conical cutting elements 452 in
an adjacent row 453. Generally, the degree of overlap of the
cutting profiles of overlapping conical cutting elements 452 in
adjacent circumferential conical cutting rows 453 may be
characterized by the ratio of the radial overlap distance to the
radial span distance of the overlapping conical cutting elements,
as described herein. According to one or more embodiments of the
present disclosure, the radial overlap ratio of adjacent conical
cutting elements 452 may range from about 0.05 to about 0.95. For
instance, the radial overlap ratio may range from a low of about
0.05, about 0.1, about 0.15, about 0.2, or about 0.25 to a high of
about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, or more. For
example, the radial overlap ratio may be between about 0.1 and
about 0.5, between about 0.1 and about 0.3, or between about 0.05
and about 0.2.
[0072] Each conical cutting element 452 in a given row 453 may at
least partially radially overlap with a cutting element 410 in an
adjacent circumferential row. Generally, the degree of overlap of
the conical cutting elements 452 and the cutting elements 410 in
adjacent circumferential conical cutting element rows 453 and
circumferential cutting element rows 426, 428, 430, 432,
respectively, may be characterized by the ratio of the radial
overlap distance to the radial span distance of the overlapping
conical cutting elements 452 and cutting elements 410, as described
herein. According to one or more embodiments of the present
disclosure, the radial overlap ratio of adjacent conical cutting
elements 452 and cutting elements 410 may range from about 0.05 to
about 0.9. For instance, the radial overlap ratio may range from a
low of about 0.05, about 0.1, about 0.15, about 0.2, or about 0.3
to a high of about 0.4, about 0.5, about 0.6, about 0.7, about 0.8,
or more. For example, the radial overlap ratio may be between about
0.05 and about 0.4, between about 0.3 and about 0.6, or between
about 0.4 and about 0.8.
[0073] The greater the radial overlap ratio of adjacent conical
cutting elements 452 and cutting elements 410, the greater the
degree of overlap of a conical cutting element 452 in a first
circumferential row with a cutting element 410 in an adjacent
second circumferential row. As this degree of overlap increases, it
may become easier for fractures created in the formation by the
conical cutting elements 452 in the first circumferential row to
communicate and connect with the fractures created in the formation
by the cutting elements 410 in the adjacent second circumferential
row. This communication between different fractures in the
formation may make it easier to generate chips from the formation.
Moreover, an increase in the degree of overlap may reduce the load
on the set of cutting elements that are responsible for the
formation of these chips.
[0074] In at least one embodiment, the circumferential conical
cutting element rows 453 may include a first circumferential
conical cutting element row 454, a second circumferential conical
cutting element row 456, and a third circumferential conical
cutting element row 458. Although FIGS. 4A and 4B show three
circumferential conical cutting element rows 454, 456, 458, between
the circumferential gage row 426 and the circumferential
adjacent-to-gage row 428, any number of conical cutting element
rows 453 may be disposed between any adjacent circumferential rows
426, 428, 430, 432 without departing from the scope of the present
disclosure.
[0075] In some embodiments, the circumferential conical cutting
element rows 454, 456, 458 may be disposed between the
circumferential gage row 426 and the circumferential
adjacent-to-gage row 428. For example, the first circumferential
conical cutting element row 454 may at least partially radially
overlap with the gage cutting elements 436 in the circumferential
gage row 426. Likewise, the third circumferential conical cutting
element row 458 may at least partially radially overlap with the
adjacent-to-gage cutting elements 438. In at least some
embodiments, the second circumferential conical cutting element row
456 may at least partially radially overlap with the first and/or
third circumferential conical cutting element rows 454, 458. The
conical cutting element rows 454, 456, 458 between circumferential
gage row 426 and circumferential adjacent-to-gage row 428 may
provide more localized fracture of the bottom of the borehole than
that provided by plurality of gage cutting elements 436 and
plurality of adjacent-to-gage cutting elements 438 alone.
[0076] A cutting plane 411 may be defined as being in tangential
contact with the crest portion 437 of the gage cutting elements 436
and the crest portion 439 of the adjacent-to-gage cutting elements
438. As shown, a crest portion 455 of the conical cutting element
452 in the first circumferential conical cutting element row 454
may be in about tangential contact with the cutting plane 411. When
the crest portion 455 of the conical cutting element 452 in first
circumferential conical cutting element row 454 is in tangential
contact with the cutting plane 411, the conical cutting element 452
in first circumferential conical cutting element row 454 may impact
the formation at substantially the same time as the gage cutting
elements 436 and/or the adjacent-to-gage cutting elements 438. As a
result, the conical cutting element 452 in the first
circumferential conical cutting element row 454 may create
fractures in the formation at substantially the same depth as the
gage cutting elements 436 and the adjacent-to-gage cutting elements
438.
[0077] Even when the crest portion 455 of each conical cutting
element 452 in first circumferential conical cutting element row
454 is in tangential contact with the cutting plane 411, the
conical cutting element 452 in first circumferential conical
cutting element row 454 may create additional fractures in the
formation that are capable of communicating with fractures created
in the formation by the gage cutting elements 436 and the
adjacent-to-gage cutting elements 438. As a result, generating a
chip from the formation may become easier.
[0078] The second circumferential conical cutting element row 456
and/or the third circumferential conical cutting element row 458
may be positioned adjacent to one another and between adjacent rows
of cutting elements 410 (e.g., between the circumferential gage row
426 and the circumferential adjacent-to-gage row 428) to create
additional fractures in the bottom of the borehole during drilling
operations. A crest portion 457 of the conical cutting element 452
in the second circumferential conical cutting element row 456 and
crest portion 459 of the conical cutting element 452 in the third
circumferential conical cutting element row 458 may extend beyond
the cutting plane 411 in sonic embodiments. For example, the crest
portions 457, 459 may extend beyond the cutting plane by a distance
413. The distance 413 may range from a low of about 1%, about 3%,
about 5%, about 10%, or about 20% to a high of about 30%, about
40%, about 50%, about 60%, about 70% or more of the total height of
the conical cutting elements 452 in the second andlor third
circumferential conical cutting element rows 456, 458 (as measured
from the bit face 406). For example, the distance 413 may be up to
about 5%, about 10%, about 20%, about 30%, about 40%, about 50%,
about 60%, about 70%, or more of the total height of the conical
cutting elements 452 in the second and/or third circumferential
conical cutting element rows 456, 458. The distance 413 may also be
between about 1% and about 10%, between about 1% and about 20%,
between about 10% and about 20%, or between about 3% and about 50%
of the total height of the conical cutting elements 452 in the
second and/or third circumferential conical cutting element rows
456, 458.
[0079] When the crest portions 457, 459 of conical cutting elements
452 in the circumferential conical cutting element row 456 and/or
the third circumferential conical cutting element row 458 extend
beyond the cutting plane 411, the conical cutting elements 452 in
the second circumferential conical cutting element row 456 andlor
the third circumferential conical cutting element row 458 may
pre-fracture the formation by impacting the formation before the
crest portion 437 of gage cutting elements 436 and/or the crest
portion 439 of adjacent-to-gage cutting elements 438. In addition,
the conical cutting elements 452 in the second circumferential
conical cutting element row 456 and/or the third circumferential
conical cutting element row 458 may create a fracture in the
formation that is deeper than the fractures created by the gage
cutting elements 436 and/or the adjacent-to-gage cutting elements
438.
[0080] The conical cutting elements 452 in the second
circumferential conical cutting element row 456 and/or the third
circumferential conical cutting element row 458 may pre-split the
formation between circumferential gage row 426 and circumferential
adjacent-to-gage row 428 by creating deeper fracture contours or
grooves in the formation than that created by the gage cutting
elements 436 and the adjacent-to-gage cutting elements 438. Because
these grooves of pre-fractured formation material may be in close
proximity to one another, these grooves may further facilitate the
communication between the fractures created by the gage cutting
elements 436 and the adjacent-to-gage cutting elements 438, thereby
making it easier to generate chips from the formation during
drilling operations. Moreover, these grooves of pre-fractured
formation material may provide stress relieved areas or free faces
toward which the fractures created by the gage cutting elements 436
and the adjacent-to-gage cutting elements 438 may easily propagate.
The free faces created by the conical cutting elements 452 in the
second circumferential conical cutting element row 456 and/or the
third circumferential conical cutting element row 458 may provide a
stress relieved area where fractured rock may move toward, thereby
using less energy for the fracture generation process.
[0081] FIG. 5A depicts a profile view of a portion of a percussion
hammer drill bit 500, and FIG. 5B depicts an enlarged, partial view
of the percussion hammer drill bit 500 shown in FIG. 5A, according
to one or more embodiments of the present disclosure. A bit face
506 may be disposed on an axial end portion of the bit body 502,
and may include an inner region 512 and an outer region 514. In
some embodiments, the inner region 512 may include a cone region
516, and the outer region 514 may include a shoulder region 518, a
gage region 520, a skirt region 522, or some combination of the
foregoing.
[0082] FIG. 5A shows plurality of conical cutting elements 552
disposed on a bit face 506. The conical cutting elements 552 may be
disposed in one or more circumferential conical cutting element
rows 553. For example, the conical cutting elements 552 may be
disposed in a first circumferential conical cutting element row
554, a second circumferential conical cutting element row 556, and
a third circumferential conical cutting element row 560.
[0083] In the illustrated embodiment, the circumferential conical
cutting element rows 554, 556 may be disposed between the
circumferential gage row 526 and the circumferential
adjacent-to-gage row 528. The conical cutting elements 552 in
circumferential conical cutting element row 554 may at least
partially radially overlap the gage cutting elements 536 in
circumferential gage row 526. Likewise, the conical cutting
elements 552 in circumferential conical cutting element row 556 may
at least partially radially overlap the adjacent-to-gage cutting
elements 538 in circumferential adjacent-to-gage row 528. In
addition, the conical cutting elements 552 in the circumferential
conical cutting element row 554 may at least partially overlap with
the conical cutting elements 552 in the circumferential conical
cutting element row 556. The conical cutting elements 552 in
circumferential conical cutting element rows 554, 556 may provide
more localized fracture of the bottom of the borehole than that
provided by plurality of gage cutting elements 536 and plurality of
adjacent-to-gage cutting elements 538 alone.
[0084] In some embodiments, a circumferential conical cutting
element row 560 may be disposed between the adjacent-to-gage row
528 and a circumferential row 530 in a shoulder region 518. The
conical cutting elements 552 in the circumferential conical cutting
element row 560 may at least partially radially overlap the
adjacent-to-gage cutting elements 538 in circumferential
adjacent-to-gage row 528. Likewise, the conical cutting elements
552 in the circumferential conical cutting element row 560 may at
least partially radially overlap the inner row cutting elements 540
in row 530. The conical cutting elements 552 in conical cutting
element row 560 may provide more localized fracture of the borehole
bottom than that provided by plurality of adjacent-to-gage cutting
elements 538 and plurality of inner row cutting elements 540 row
530 alone.
[0085] A cutting plane 511 may be defined to be in tangential
contact with the crest portion 537 of the gage cutting elements 536
and/or the crest portion 539 of the adjacent-to-gage cutting
elements 538. As shown, a crest portion 555 of the conical cutting
elements 552 in the first circumferential conical cutting element
row 554 and a crest portion 557 of the conical cutting elements 552
in the second circumferential conical cutting element row 556 may
be offset from the cutting plane 511 by a distance 513. The
distance 513 may range from a low of about 1%, about 3%, about 5%,
about 10%, or about 20% to a high of about 30%, about 40%, about
50%, about 60%, about 70% or more of the total height of the
conical cutting elements 552 in the first and/or second
circumferential conical cutting element rows 554, 556 (as measured
from the bit face 506). For example, the distance 513 may be up to
about 5%, about 10%, about 20%, about 30%, about 40%, about 50%,
about 60%, about 70%, or more of the total height of the conical
cutting elements 552 in the first and/or second circumferential
conical cutting element rows 554, 556. The distance 513 may also be
between about 1% and about 10%, between about 1% and about 20%,
between about 10% and about 20%, or between about 3% and about 50%
of the total height of the conical cutting elements 552 in the
first and/or second circumferential conical cutting element rows
554, 556.
[0086] When the crest portions 555, 557 of the conical cutting
elements 552 in the first and/or second circumferential conical
cutting element rows 554, 556 extend beyond the cutting plane 511,
the conical cutting elements 552 in first circumferential conical
cutting element row 554 and/or in second circumferential conical
cutting element row 556 may pre-fracture the formation by impacting
the formation before the crest portion of the gage cutting elements
536 and/or the adjacent-to-gage cutting elements 538. In addition,
the conical cutting elements 552 in the first circumferential
conical cutting element row 554 and the second circumferential
conical cutting element row 556 may create a fracture in the
formation that is deeper than the fractures created by the crest
portion of the gage cutting elements 536 and the adjacent-to-gage
cutting elements 538.
[0087] The conical cutting elements 552 in the first
circumferential conical cutting element row 554 and/or the second
circumferential conical cutting element row 556 may pre-split the
formation between the circumferential gage row 526 and the
circumferential adjacent-to-gage row 528 by creating deeper
fracture contours or grooves in the formation than that created by
the crest portion of the gage cutting elements 536 and/or the
adjacent-to-gage cutting elements 538. Because these grooves of
pre-fractured formation material may be in close proximity to one
another, these grooves may further facilitate the communication
between the fractures created by the crest portion of the gage
cutting elements 536 and/or the adjacent-to-gage cutting elements
538, thereby making it easier to generate chips from the formation
during drilling operations. Moreover, these grooves of
pre-fractured formation material may provide stress relieved areas
or free faces toward which the fractures created by the gage
cutting elements 536 and/or the adjacent-to-gage cutting elements
538 may easily propagate. The free faces created b the conical
cutting elements 552 in the first circumferential conical cutting
element row 554 and/or the second circumferential conical cutting
element row 556 may provide a stress relieved area that fractured
rock may move toward, thereby using less energy for the fracture
generation process.
[0088] A cutting plane 517 may be defined in tangential contact
with the crest portion 539 of the adjacent-to-gage cutting elements
538 and the crest portion 541 of the inner row cutting elements
540. A crest portion 561 of the conical cutting elements 552 in the
third circumferential conical cutting element row 560 may be in
tangential contact with the cutting plane 517. When the crest
portion 561 of the conical cutting elements 552 in third
circumferential conical cutting element row 560 is in tangential
contact with the cutting plane 517, the conical cutting elements
552 in the third circumferential conical cutting element row 560
may impact the formation at substantially the same time as the
adjacent-to-gage cutting elements 538 and/or the inner row cutting
elements in 540 in row 530. In addition, the conical cutting
elements 552 in the third circumferential conical cutting element
row 560 may create fractures in the formation at substantially the
same depth as the adjacent-to-gage cutting elements 538 and the
inner row cutting elements 540 in row 530.
[0089] The conical cutting elements 552 in the third
circumferential conical cutting element row 560 may create
additional fractures in the formation that are capable of
communicating with fractures created in the formation by the crest
portion of the adjacent-to-gage cutting elements 538 and/or the
inner row cutting elements 540 in row 530. As a result, generating
a chip from the formation may become easier when the conical
cutting elements 552 in the third circumferential conical cutting
element row 560 are in tangential contact with the cutting plane
517.
[0090] Referring generally now to FIGS. 1-5B, in operation, a drill
bit (e.g., percussion hammer drill bit 100, 200, 300, 400, 500) may
be run into a borehole on a work string until the drill bit
contacts the bottom portion of the borehole. The drill bit may then
moves hack and forth axially within the borehole, contacting the
bottom portion of the borehole on each forward stroke. More
particularly, the cutting elements and conical cutting elements on
the drill bit may contact the bottom portion of the borehole on
each forward stroke, thereby cutting or grinding the formation to
extend the length of the borehole. In addition, the drill bit may
be indexed between seine or each axial impact of the drill bit with
the formation so that with each subsequent forward stroke, the
cutting elements and conical cutting elements may contact different
locations of the formation on the bottom portion of the borehole.
The outer surface of the cutting elements and/or the conical
cutting elements may be made of or include tungsten carbide,
tungsten carbide with a super-abrasive material surface such as
polycrystalline diamond ("PCD") or cubic boron nitride ("PCBN"),
other matrix materials of carbides, nitrides, or borides, or other
materials, or any combination of the foregoing.
[0091] As used herein, the terms "inner" and "outer;" "up" and
"down;" "upper" and "lower;" "upward" and "downward;" "above" and
"below;" "inward" and "outward" and other like terms as used herein
refer to relative positions to one another and are not intended to
denote a particular direction or spatial orientation. The terms
"couple," "coupled," "connect," "connection," "connected," "in
connection with," and "connecting" refer to "in direct connection
with" or "in connection with via another element or member." The
terms "hot" and "cold" refer to relative temperatures to one
another. Where a range of values is provided, any two numbers
listed may provide a range for embodiments of the present
disclosure.
[0092] Although only a few example embodiments have been described
in detail above, those skilled in the art will readily appreciate
that many modifications are possible in the example embodiments
without materially departing from the scope of the present
disclosure. Accordingly, all such modifications are intended to be
included within the scope of this disclosure. In the claims,
means-plus-function clauses are intended to cover the structures
described herein as performing the recited function and not only
structural equivalents, but also equivalent structures. Thus,
although a nail and a screw may not be structural equivalents in
that a nail employs a cylindrical surface to secure wooden parts
together, whereas a screw employs a helical surface, in the
environment of fastening wooden parts, a nail and a screw may be
equivalent structures. It is the express intention of the applicant
not to invoke 35 U.S.C. .sctn.120, 6 for any limitations of any of
the claims herein, except for those in which the claim expressly
uses the words `means for` together with an associated
function.
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