U.S. patent application number 16/410154 was filed with the patent office on 2019-09-05 for hybrid roller cone and junk mill bit.
The applicant listed for this patent is Varel International Ind., L.P.. Invention is credited to Johnathan Walter Howard, Sterling Robinson, Matthew Charles Stroever.
Application Number | 20190271203 16/410154 |
Document ID | / |
Family ID | 59561279 |
Filed Date | 2019-09-05 |
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United States Patent
Application |
20190271203 |
Kind Code |
A1 |
Howard; Johnathan Walter ;
et al. |
September 5, 2019 |
HYBRID ROLLER CONE AND JUNK MILL BIT
Abstract
A hybrid bit for use in a wellbore includes: a body having a
shank for connection to a drilling motor or drill pipe and a
plurality of legs attached to the shank; and a plurality of cutting
structures. The cutting structures include a roller cone mounted to
a first one of the legs and a fixed mill mounted to a second one of
the legs and including a pad dressed with a cermet material.
Inventors: |
Howard; Johnathan Walter;
(Conroe, TX) ; Stroever; Matthew Charles; (Spring,
TX) ; Robinson; Sterling; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Varel International Ind., L.P. |
Carrollton |
TX |
US |
|
|
Family ID: |
59561279 |
Appl. No.: |
16/410154 |
Filed: |
May 13, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15400163 |
Jan 6, 2017 |
10337272 |
|
|
16410154 |
|
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|
62295746 |
Feb 16, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 10/14 20130101;
E21B 29/00 20130101; E21B 10/567 20130101 |
International
Class: |
E21B 29/00 20060101
E21B029/00; E21B 10/14 20060101 E21B010/14; E21B 10/567 20060101
E21B010/567 |
Claims
1. A hybrid bit for use in a wellbore, comprising: a body having a
shank for connection to a drilling motor or drill pipe and a
plurality of legs attached to the shank; and a plurality of cutting
structures, comprising: a roller cone mounted to a first one of the
plurality of legs; and a fixed mill mounted to a second one of the
plurality of legs and comprising a pad dressed with a cermet
material; and a junk chute for accommodating milling of a pump-down
plug and comprising: a diverter groove formed in the pad; and a
junk slot formed between the first one of the plurality of legs and
the second one of the plurality of legs and having an entrance
located adjacent to the diverter groove, wherein: the diverter
groove is formed in a leading edge of the pad such that the roller
cone rotates in a direction for driving the pump-down plug into the
diverter groove, and the diverter groove has an outer shoulder
shaped for trapping the pump-down plug and an inner contour for
directing the pump-down plug toward cutters of the roller cone
2. The hybrid bit of claim 1, wherein: the roller cone has a nose
row of cutters, each cutter of the nose row is a milled tooth or a
cermet insert, and the nose row is located adjacent to the diverter
groove.
3. The hybrid bit of claim 2, wherein each cutter of the nose row
is the milled tooth.
4. The hybrid bit of claim 1, wherein the diverter groove is also
dressed with the cermet material.
5. The hybrid bit of claim 1, wherein the diverter groove is
longitudinally inclined such that a size thereof is greatest
adjacent to a bottom of the pad and decreases toward the junk slot
for funneling the pump-down plug toward the junk slot.
6. The hybrid bit of claim 1, wherein the cermet material is a
plurality of cutter blocks brazed to the pad.
7. The hybrid bit of claim 6, wherein the plurality of cutter
blocks are brazed into grooves formed in the pad at a desired
orientation.
8. The hybrid bit of claim 6, wherein: each cutter block of the
plurality of cutter blocks has a pair of opposite rectangular sides
and four profiled sides connecting the rectangular sides, the
profiled sides each have rectangular end portions located adjacent
to the respective rectangular sides and profiled mid portions
connecting the respective end portions, and each rectangular side
has a raised peripheral portion and a recessed interior
portion.
9. The hybrid bit of claim 6, wherein the plurality of cutter
blocks are brazed on the pad such that a cutting edge thereof is
over-exposed relative to a cutting edge of a cutting structure of
the roller cone.
10. The hybrid bit of claim 6, wherein the plurality of cutter
blocks are brazed on the pad such that a cutting edge thereof is
under-exposed relative to a cutting edge of a cutting structure of
the roller cone.
11. The hybrid bit of claim 6, wherein the plurality of cutter
blocks are brazed on the pad such that a cutting edge thereof is
equally exposed relative to a cutting edge of a cutting structure
of the roller cone.
12. The hybrid bit of claim 1, wherein the second leg has a wrench
profile formed therein.
13. The hybrid bit of claim 1, further comprising a second roller
cone mounted to a third one of the plurality of legs, wherein the
plurality of cutting structures consists only of three cutting
structures.
14. The hybrid bit of claim 1, further comprising a second fixed
mill mounted to a third one of the plurality of legs, wherein the
plurality of cutting structures consists only of three cutting
structures.
15. The hybrid bit of claim 1, wherein a cutting edge of each of
the plurality of cutter blocks is made from the cermet
material.
16. A method of drilling out a plug, comprising: assembling the
hybrid bit of claim 1 as part of a mill string; deploying the mill
string into a casing or liner string set in the wellbore to the
plug set in the casing or liner string; and injecting milling fluid
through the mill string, rotating the hybrid bit, and engaging the
hybrid bit with the plug, thereby drilling out the plug.
17. A junk mill for use in a wellbore, comprising: a body having a
shank for connection to a drilling motor or drill pipe; a plurality
of fixed cutting structures mounted to the body, each cutting
structure comprising a pad dressed with a cermet material; and a
junk chute for accommodating milling of a pump-down plug and
comprising: a diverter groove formed in a first one of the pads;
and a junk slot formed between the first and an adjacent second one
of the pads and having an entrance located adjacent to the diverter
groove.
Description
BACKGROUND OF THE DISCLOSURE
Field of the Disclosure
[0001] The present disclosure generally relates to a hybrid roller
cone and junk mill bit.
Description of the Related Art
[0002] U.S. Pat. No. 8,678,111 discloses a hybrid earth-boring bit
including a bit body having a central axis, at least one,
preferably three fixed blades, depending downwardly from the bit
body, each fixed blade having a leading edge, and at least one
rolling cutter, preferably three rolling cutters, mounted for
rotation on the bit body. A rolling cutter is located between two
fixed blades.
[0003] U.S. Pat. App. Pub. No. 2013/0313021 discloses an earth
boring drill bit having a bit body having a central longitudinal
axis that defines an axial center of the bit body and configured at
its upper extent for connection into a drillstring; at least one
primary fixed blade extending downwardly from the bit body and
inwardly toward, but not proximate to, the central axis of the
drill bit; at least one secondary fixed blade extending radially
outward from proximate the central axis of the drill bit; a
plurality of fixed cutting elements secured to the primary and
secondary fixed blades; at least one bit leg secured to the bit
body; and a rolling cutter mounted for rotation on the bit leg;
wherein the fixed cutting elements on at least one fixed blade
extend from the center of the bit outward toward the gage of the
bit but do not include a gage cutting region, and wherein at least
one roller cone cutter portion extends from substantially the drill
bit's gage region inwardly toward the center of the bit, the apex
of the roller cone cutter being proximate to the terminal end of
the at least one secondary fixed blade, but does not extend to the
center of the bit.
[0004] U.S. Pat. App. Pub. No. 2015/0053422 discloses a hybrid
rotary cone drill bit including a plurality of legs. A bearing
shaft extends from each leg, and a rotary cone is rotationally
coupled to each bearing shaft. At least one rotary cone includes a
nose row of cutting structures, an inner row of cutting structures,
and a gage row of cutting structures. The nose row and the inner
row of cutting structures are formed of milled teeth. The gage row
of cutting structures is formed of cutter inserts.
[0005] U.S. Pat. App. Pub. No. 2015/0233187 discloses a fixed
cutter bit for milling a frac plug including a body and a face. The
face includes a base surface and a plurality of cutter support
structures extending from the base surface. Each cutter support
structure has a peripheral portion and an inner portion disposed
radially internal of the peripheral portion. At least one
first-type cutter is supported by each peripheral portion; at least
one second-type cutter is supported by each inner portion. The
first type cutter is adapted to mill a harder material than the
second-type cutter, and the first-type is different from the
second-type.
SUMMARY OF THE DISCLOSURE
[0006] The present disclosure generally relates to a hybrid roller
cone and junk mill bit. In one embodiment, a hybrid bit for use in
a wellbore includes: a body having a shank for connection to a
drilling motor or drill pipe and a plurality of legs attached to
the shank; and a plurality of cutting structures. The cutting
structures include a roller cone mounted to a first one of the legs
and a fixed mill mounted to a second one of the legs and including
a pad dressed with a cermet material.
[0007] In another embodiment, a junk mill for use in a wellbore
includes: a body having a shank for connection to a drilling motor
or drill pipe; a plurality of fixed cutting structures mounted to
the body, each cutting structure including a pad dressed with a
cermet material; and a junk chute for accommodating milling of a
pump-down plug. The junk chute includes a diverter groove formed in
a first one of the pads and a junk slot formed between the first
and an adjacent second one of the pads and having an entrance
located adjacent to the diverter groove.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] So that the manner in which the above recited features of
the present disclosure can be understood in detail, a more
particular description of the disclosure, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this disclosure and are therefore not to be considered limiting of
its scope, for the disclosure may admit to other equally effective
embodiments.
[0009] FIG. 1 illustrates a hybrid rotary cone and junk mill bit
positioned for drilling out a frac plug set in a wellbore,
according to one embodiment of the present disclosure.
[0010] FIGS. 2 and 3 illustrate the hybrid bit.
[0011] FIGS. 4A-4C illustrates a cutter of a fixed mill cutting
structure of the hybrid bit.
[0012] FIGS. 5A-5C illustrate mounting of the cutter to a mill pad
of the hybrid bit.
[0013] FIG. 5D illustrates exposure options of the fixed mill
cutting structure relative to the roller cone cutting structures of
the hybrid bit.
[0014] FIG. 6 illustrates the hybrid bit having captured a ball of
the frac plug during drill out thereof.
[0015] FIG. 7A illustrates an alternative hybrid bit, according to
another embodiment of the present disclosure. FIG. 7B illustrates a
junk mill, according to another embodiment of the present
disclosure.
DETAILED DESCRIPTION
[0016] FIG. 1 illustrates a hybrid rotary cone and junk mill bit 1
positioned for drilling out a frac plug 2 set in a wellbore 3,
according to one embodiment of the present disclosure. For a
hydraulic fracturing operation, the frac plug 2 is set against a
casing or liner string 4 to isolate a zone (not shown) of a
formation adjacent to the wellbore 3. To set the frac plug 2, a
setting tool (not shown) and the frac plug 2 may be deployed down
the casing or liner string 4 using a wireline (not shown). The frac
plug 2 may be set by supplying electricity to the setting tool via
the wireline to activate the setting tool. A piston of the setting
tool may move an outer portion of the frac plug 2 along a mandrel 5
of the frac plug while the wireline restrains a mandrel of the
setting tool and the plug mandrel, thereby compressing a packing
element 8 and driving slips 6 along respective slip cones 7 of the
frac plug. The packing element 8 may be radially expanded into
engagement with the casing or liner string 4 and the slips 6 may be
wedged into engagement therewith.
[0017] The casing or liner string 4 may then be perforated above
the set frac plug 2 and the isolated zone may be hydraulically
fractured by pumping a ball 9 followed by fracturing fluid (not
shown) down the casing or liner string 4. The ball 9 may land in a
seat of the plug mandrel 5, thereby forcing the fracturing fluid
into the zone via the perforations. Another frac plug (not shown)
may then be set above the fractured zone and the casing or liner
string 4 may again be perforated above the plug for hydraulic
fracturing of another zone. This process may be repeated many
times, such as greater than or equal to ten or twenty times, until
all of the zones adjacent to the wellbore 3 have been
fractured.
[0018] After all of the zones have been fractured, a production
valve at the wellhead may be opened to produce fluid from the
wellbore in an attempt to retrieve the balls 9. However, this
attempt often fails. The hybrid bit 1 (only partially shown) may be
deployed down the casing or liner string 4 using coiled tubing (not
shown). A drilling motor (not shown), such as a mud motor, may
connect the hybrid bit 1 to the coiled tubing. The hybrid bit 1,
drilling motor, and coiled tubing may be collectively referred to
as a mill string. Milling fluid may be pumped down the coiled
tubing, thereby driving the drilling motor to rotate the hybrid bit
1 and the hybrid bit may be advanced into engagement with the frac
plug 2, thereby drilling out the frac plug. Once drilled out, the
mill string may be advanced to drill out the next frac plug 2 until
all of the frac plugs have been drilled out.
[0019] Alternatively, the mill string may include a string of drill
pipe instead of coiled tubing with or without the drilling motor.
Alternatively, the hybrid bit 1 may be employed to drill out other
types of downhole tools, such as packers, bridge plugs, float
collars, float shoes, stage collars, guide shoes, reamer shoes,
and/or casing bits.
[0020] FIGS. 2 and 3 illustrate the hybrid bit 1. The hybrid bit 1
may include a body 10 and a plurality of cutting structures, such
as one or more roller cones 11a,b and a fixed mill 11c. The body 10
may have an upper shank 10s and a lower leg 10a-c for each cutting
structure 11a-c. The body 10 may be made from a metal or alloy,
such as steel. Each leg 10a-c may be attached to the shank 10s,
such as by welding. The legs 10a-c may be equally spaced around the
body 10, such as three at one hundred twenty degrees. The shank 10s
may have a coupling, such as a threaded pin, formed at an upper end
thereof for connection to the drilling motor or drill pipe. A bore
(not shown) may be formed in the shank 10s and may extend from an
upper end thereof to a plenum formed therein adjacent to a lower
end thereof.
[0021] Each leg 10a,b may have an upper shoulder 12s, a mid
shirttail 12h, a lower bearing shaft (not shown), and a ported boss
12n. The shoulder 12s, shirttail 12h, ported boss 12n, and bearing
shaft of each leg 10a,b may be interconnected, such as by being
integrally formed and/or welded together. Each ported boss 12n may
be in fluid communication with the plenum via a respective port
formed in the shank 10s and may have a nozzle fastened therein for
discharging the milling fluid onto the respective roller cone
11a,b. Each bearing shaft may extend from the respective shirttail
12h in a radially inclined direction. Each bearing shaft may have a
journal for supporting rotation of the respective roller cone 11a,b
therefrom. Each leg 10a,b may have a lubricant reservoir formed
therein and a lubricant passage extending from the reservoir to the
respective journal bearing formed between the bearing shaft and the
respective roller cone 11a,b. The lubricant may be retained within
the each leg 10a,b by a seal, such as an o-ring, positioned in a
seal gland between the respective cone 11a,b and the bearing shaft.
Each leg 10a,b may also have a fill port 12p in fluid communication
with the lubricant reservoir and closed by a pressure
compensator.
[0022] Each roller cone 11a,b may be mounted to the respective leg
10a,b by a plurality of balls (not shown) received in a race formed
by aligned grooves in each roller cone and the respective bearing
shaft. The balls may be fed to each race by a ball passage formed
in each leg 10a,b and retained therein by a respective ball plug
13. Each ball plug 13 may be attached to the respective leg 10a,b,
such as by welding. Upper and lower edges of each shirttail 12h may
be protected from erosion and/or abrasion by respective hardfacing
22u,w with a ceramic or cermet material. An outer surface of each
shirttail 12h may also be protected from erosion and/or abrasion by
stabilizer inserts 14 secured into sockets thereof, such as by
interference fit or brazing. Each insert 14 may be made from a
cermet.
[0023] Each roller cone 11a,b may be made from a metal or alloy,
such as steel. Each roller cone 11a,b may have a plurality of
respective rows 15a-c, 16a-c of cutters, such as a nose row 15a,
16a, an inner row 15b, 16b, and a gage row 15c, 16c of cutters. The
nose row 16a and the inner row 16b of the roller cone 11 b may be
offset relative to the respective nose row 15a and inner row 15b of
the roller cone 11a. Each cutter of the nose rows 15a, 16a may be a
milled tooth hardfaced by a cermet. Each cutter of the inner row
15b may be a milled tooth hardfaced by a ceramic or cermet
material. Each cutter of the gage rows 15c, 16c may be a cermet
insert mounted in sockets formed in the respective roller cone
11a,b, such as by interference fit or brazing. Each cutter of the
inner row 16b may be a cermet insert mounted to the roller cone
11b, such as by interference fit or brazing. Each cermet insert may
be chisel-shaped (shown) or conical (not shown).
[0024] Alternatively, each cutter of both inner rows 15b, 16b may
be a hardfaced milled tooth. Alternatively, each cutter of both
inner rows 15b, 16b may be a cermet insert. Alternatively, each
cutter of the roller cones 11a,b may be a hardfaced milled tooth.
Alternatively, each cutter of the roller cones 11a,b may be a
cermet insert. Alternatively, each cutter of at least one row of
either roller cone 11a,b may be a cermet insert and each cutter of
at least one row of either roller cone 11a,b may be a hardfaced
milled tooth.
[0025] The leg 10c may have an upper shoulder 17s, a mid shirttail
17h, a wrench profile 17w, a mill pad 17p, and a ported boss 17n.
The shoulder 17s, shirttail 17h, mill pad 17p, and ported boss 17n
of the leg 10c may be interconnected, such as by being integrally
formed and/or welded together. The ported boss 17n may be in fluid
communication with the plenum via a respective port formed in the
shank 10s and may have a nozzle fastened therein for discharging
the milling fluid onto the fixed mill cutting structure 11c. Upper
and lower edges of each shirttail 17h may also be protected from
erosion and/or abrasion by the hardfacing 22u,w. An outer surface
of the shirttail 17h may also be protected from erosion and/or
abrasion by the stabilizer inserts 14 mounted into sockets formed
therein, such as by interference fit or brazing. The wrench profile
17w may be a flat and may be formed in the shirttail 17h adjacent
to the shoulder 17s. Since the leg 10c does not need a lubricant
reservoir, the space that would otherwise be occupied by the fill
port 12p may be utilized for the wrench profile 17w, thereby
obviating the need for a bit box to connect the hybrid bit 1 to the
mill string. The hybrid bit 1 may further include a second wrench
profile, such as a flat, formed in the ported boss 12n opposite to
the leg 10c.
[0026] The hybrid bit 1 may further have a first junk slot 29a
formed between the shirttail 12h of the leg 10a and the shirttail
17h of the leg 10c and a second junk slot 29b formed between the
shirttails 12h of the legs 10a,b. The hybrid bit 1 may further have
a junk chute 18 with a third junk slot 18s. Each junk slot 29a,b,
18s may be formed into the body 10, such as by milling and/or
forging. Each ported boss 12n, 17n may be located in a respective
junk slot 29a,b, 18s. Each junk slot 29a,b, 18s may be sized to
allow passage of debris (not shown) created during milling of the
frac plugs 2 into an annulus formed between the mill string and the
casing or liner string 4.
[0027] The junk chute 18 may include a diverter groove 18g formed
in the mill pad 17p and the third junk slot 18s formed between the
shirttail 17h of the leg 10c and the shirttail 12h of the leg 10b.
An entrance of the junk slot 18s may be located adjacent to the
diverter groove 18g. The diverter groove 18g may be operable to
receive and capture each ball 9 of the respective frac plug 2. The
diverter groove 18g may be located along a leading edge of the mill
pad 17p (see rotation arrow 19a in FIG. 6) such that the adjacent
roller cone 11b rotates in a direction 19b for driving the ball 9
into the diverter groove. The diverter groove 18g may have an outer
shoulder 18o shaped for trapping the ball 9 and an inner contour
18n for directing the ball toward the cutters of the adjacent
roller cone 11b. The diverter groove 18g may also be longitudinally
inclined such that a size thereof is greatest adjacent to a bottom
of the mill pad 17p and decreases toward the junk slot 18s, thereby
funneling the ball 9 toward the junk slot.
[0028] FIGS. 4A-4C illustrate a cutter 20 of the fixed mill cutting
structure 11c. To form the fixed mill cutting structure 11c, the
mill pad 17p (including the diverter groove 18g) may be dressed
with cutters 20. Each cutter 20 may be a block, such as a cubic
block, of cermet material. The cermet material may include a binder
and carbide, such as cobalt-tungsten carbide. The cermet material
may be formed into the block by sintering, such as hot
pressing.
[0029] Each cutter 20 may have a pair of opposite rectangular sides
and four profiled sides connecting the rectangular sides. The
profiled sides may each have rectangular end portions located
adjacent to the respective rectangular sides and profiled mid
portions connecting the respective end portions. Each rectangular
end portion may have chamfered corners adjacent to the respective
rectangular sides. Each profiled portion may have a pair of opposed
trapezoidal portions converging from the respective end portions
toward a center of the cutter 20. Each profiled portion may further
have a filleted rectangular center portion connecting ends of the
trapezoidal portions distal from the respective end portions. Each
rectangular side may have a raised peripheral portion and a
recessed interior portion. Tapered walls may connect each raised
peripheral portion to the respective interior portion. Each corner
of the tapered walls may be shaved.
[0030] FIGS. 5A-5C illustrate mounting of the cutter 20 to the mill
pad 17p. The diverter groove 18g has been omitted from the mill pad
17p for simplicity. The mill pad 17p may have circumferentially
extending grooves 24 for dressing the mill pad with the cutters 20.
The grooves 24 may each be vee-shaped to facilitate a desired
orientation of the cutters 20 therein. The desired orientation may
be either the orientation illustrated in FIG. 5B or the orientation
illustrated in FIG. 5C.
[0031] Each cutter 20 may occupy only a small fraction of a surface
of the mill pad 17p such that many cutters are necessary to dress
the surface, such as greater than or equal to thirty cutters. The
cutters 20 may be mounted in the respective grooves 24, such as by
brazing. To facilitate the brazing operation, several cutters 20
may be combined in a rod (not shown) with a tinning binder which
allows a welder (person or robot) to rapidly braze the cutters on
the surfaces.
[0032] Alternatively, the mill pad 17p may be non-profiled and the
cutters mounted thereto in a random orientation. Alternatively, the
mill pad 17p may be hardfaced with a ceramic or cermet material
instead of having the cutters 20 mounted thereto.
[0033] FIG. 5D illustrates exposure options of the fixed mill
cutting structure 11c relative to the roller cone cutting
structures 11a,b. The cutters 20 may be mounted on the mill pad 17p
such that a cutting edge 21 thereof is over-exposed 21a, equally
exposed 21b, or under-exposed 21c relative to a cutting edge of the
roller cone cutting structures 11a,b. The over-exposure 21a means
that the fixed mill cutting structure 11c will engage each frac
plug 2 immediately before the roller cone cutting structures 11a,b.
The under-exposure means that the fixed mill cutting structure 11c
will engage each frac plug 2 immediately after the roller cone
cutting structures 11a,b. Equal exposure 21b means that the fixed
mill cutting structure 11c will engage each frac plug 2
contemporaneously with the roller cone cutting structures 11a,b.
The exposure 21a-c may be selected according to the materials of
each frac plug 2. If each frac plug 2 is primarily constructed of
hard and brittle materials, such as cast iron, then underexposure
21c may be more beneficial as the less aggressive roller cone
cutting structures 11a,b are more suitable thereto. If each frac
plug 2 is primarily constructed of resilient materials, such as
composites, then overexposure 21c may be more beneficial as the
more aggressive cutters 20 are more suitable thereto.
[0034] FIG. 6 illustrates the hybrid bit 1 having captured the ball
9 of the frac plug 2 during drill out thereof. The interaction
between the diverter groove 18g and the adjacent roller 11b cone
may serve to catch and trap the ball 9 until the ball has been
milled into a small enough piece of debris to travel through the
junk slot 18s. Dressing the diverter groove 18g with the cutters 20
allows gripping of the ball 9 to discourage the ball from spinning
as the hybrid bit 1 is milling the ball.
[0035] Alternatively, the diverter groove 18g may be configured to
catch and trap other types of pump-down plugs, such as darts.
Alternatively, the diverter groove 18g may not be dressed with the
cutters 20.
[0036] FIG. 7A illustrates an alternative hybrid bit 23, according
to another embodiment of the present disclosure. The alternative
hybrid bit 23 may include a modified body and a plurality of
cutting structures, such as the roller cone 11 b and a plurality of
fixed mills 11c, 23m. The modified body 10 may be similar to the
body 10 except for having a modified leg instead of the leg 10a.
The modified leg may be similar to the leg 10c except that the mill
pad thereof may have the diverter groove omitted therefrom.
[0037] FIG. 7B illustrates a junk mill 25, according to another
embodiment of the present disclosure. The junk mill 25 may include
a tubular body (not shown) and plurality (three shown) fixed
cutting structures 26a-c. The body may have a coupling, such as a
threaded pin, formed at an upper end thereof for assembly as part
of a mill string, a flow bore therein, and ported bosses for
discharging milling fluid onto the cutting structures. Each cutting
structure 26a-c may include a pad (not shown) mounted to the body,
such as by welding, and cermet material bonded to the pad, such as
by hardfacing. The junk mill 25 may also have a first junk slot 27a
formed between the cutting structures 26a,b, a second junk slot 27b
formed between the cutting structures 26a,c and a junk chute 28.
The junk chute 28 may include a diverter groove 28g and a junk slot
28s formed between the cutting structures 26b,c and having an
entrance located adjacent to the diverter groove. The diverter
groove 28g may be formed in a leading or trailing edge of the
cutting structure 26c, dressed (not shown) with the cermet
material, and may be configured to operate in a similar fashion to
the diverter groove 18g.
[0038] Alternatively, the junk mill 25 may be dressed with the
cutters 20 instead of being hardfaced.
[0039] While the foregoing is directed to embodiments of the
present disclosure, other and further embodiments of the disclosure
may be devised without departing from the basic scope thereof, and
the scope of the invention is determined by the claims that
follow.
* * * * *