Note: Descriptions are shown in the official language in which they were submitted.
CA 02642416 2008-10-30
EXPANDABLE ROLLER REAMER
BACKGROUND OF INVENTION
Field of the Invention
[0001] The present disclosure relates to a roller reamer for stabilizing a
drillstring and
reducing torque.
Description of the Related Art
[0002] In the drilling of oil and gas wells, concentric casing strings are
installed and
cemented in the borehole as drilling progresses to increasing depths. Each new
casing
string is supported within the previously installed casing string, thereby
limiting the
annular area available for the cementing operation. Further, as successively
smaller
diameter casing strings are suspended, the flow area for the production of oil
and gas is
reduced. Therefore, to increase the annular space for the cementing operation,
and to
increase the production flow area, it is often desirable to enlarge the
borehole below the
terminal end of the previously cased borehole. By enlarging the borehole, a
larger
annular area is provided for subsequently installing and cementing a larger
casing string
than would have been possible otherwise. Accordingly, by enlarging the
borehole below
the previously cased borehole, the bottom of the formation can be reached with
comparatively larger diameter casing, thereby providing more flow area for the
production of oil and gas.
[0003] Various methods have been devised for passing a drilling assembly
through an
existing cased borehole and enlarging the borehole below the casing. One such
method is
the use of an underreamer, which has basically two operative states--a closed
or collapsed
state, where the diameter of the tool is sufficiently small to allow the tool
to pass through
the existing cased borehole, and an open or partly expanded state, where one
or more
arms with cutters on the ends thereof extend from the body of the tool. In
this latter
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= 1 ~
position, the underreamer enlarges the borehole diameter as the tool is
rotated and
lowered in the borehole.
[0004] A "drilling type" underreamer is typically used in conjunction with a
conventional
pilot drill bit positioned below or downstream of the underreamer. The pilot
bit can drill
the borehole at the same time as the underreamer enlarges the borehole formed
by the bit.
Underreamers of this type usually have hinged arms with roller cone cutters
attached
thereto. Most of the prior art underreamers utilize swing out cutter arms that
are pivoted
at an end opposite the cutting end of the cutting arms, and the cutter arms
are actuated by
mechanical or hydraulic forces acting on the arms to extend or retract them.
Typical
examples of these types of underreamers are found in U.S. Pat. Nos. 3,224,507;
3,425,500 and 4,055,226. In some designs, these pivoted arms tend to break
during the
drilling operation and must be removed or "fished" out of the borehole before
the drilling
operation can continue. The traditional underreamer tool typically has rotary
cutter
pocket recesses formed in the body for storing the retracted arms and roller
cone cutters
when the tool is in a closed state. The pocket recesses form large cavities in
the
underreamer body, which requires the removal of the structural metal forming
the body,
thereby compromising the strength and the hydraulic capacity of the
underreamer.
Accordingly, these prior art underreamers may not be capable of underreaming
harder
rock formations, or may have unacceptably slow rates of penetration, and they
are not
optimized for the high fluid flow rates required. The pocket recesses also
tend to fill with
debris from the drilling operation, which hinders collapsing of the arms. If
the arms do
not fully collapse, the drill string may easily hang up in the borehole when
an attempt is
made to remove the string from the borehole.
[0005] Conventional underreamers have several disadvantages, including cutting
structures that are typically formed of sections of drill bits rather than
being specifically
designed for the underreaming function. Therefore, the cutting structures of
most
underreamers do not reliably underream the borehole to the desired diameter. A
further
disadvantage is that adjusting the expanded diameter of a conventional
underreamer
requires replacement of the cutting arms with larger or smaller arms, or
replacement of
other components of the underreamer tool. It may even be necessary to replace
the
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a ~
underreamer altogether with one that provides a different expanded diameter.
Another
disadvantage is that many underreamers are designed to automatically expand
when
drilling fluid is pumped through the drill string, and no indication is
provided at the
surface that the underreamer is in the fully-expanded position. In some
applications, it
may be desirable for the operator to control when the underreamer expands.
[0006] Accordingly, it would be advantageous to provide an underreamer that is
stronger
than prior art underreamers, with a hydraulic capacity that is optimized for
the high flow
rate drilling environment. It would further be advantageous for such an
underreamer to
include several design features, namely cutting structures designed for the
underreaming
function, mechanisms for adjustment of the expanded diameter without requiring
component changes, and the ability to provide indication at the surface when
the
underreamer is in the fully-expanded position. Moreover, in the presence of
hydraulic
pressure in the drill string, it would be advantageous to provide an
underreamer that is
selectively expandable.
[0007] Another method for enlarging a borehole below a previously cased
borehole
section includes using a winged reamer behind a conventional drill bit. In
such an
assembly, a conventional pilot drill bit is disposed at the lowermost end of
the drilling
assembly with a winged reamer disposed at some distance behind the drill bit.
The
winged reamer generally comprises a tubular body with one or more
longitudinally
extending "wings" or blades projecting radially outwardly from the tubular
body. Once
the winged reamer has passed through any cased portions of the wellbore, the
pilot bit
rotates about the centerline of the drilling axis to drill a lower borehole on
center in the
desired trajectory of the well path, while the eccentric winged reamer follows
the pilot bit
and engages the formation to enlarge the pilot borehole to the desired
diameter.
[0008] Yet another method for enlarging a borehole below a previously cased
borehole
section includes using a bi-center bit, which is a one-piece drilling
structure that provides
a combination underreamer and pilot bit. The pilot bit is disposed on the
lowermost end
of the drilling assembly, and the eccentric underreanmer bit is disposed
slightly above the
pilot bit. Once the bi-center bit has passed through any cased portions of the
wellbore,
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the pilot bit rotates about the centerline of the drilling axis and drills a
pilot borehole on
center in the desired trajectory of the well path, while the eccentric
underreamer bit
follows the pilot bit and engages the formation to enlarge the pilot borehole
to the desired
diameter. The diameter of the pilot bit is made as large as possible for
stability while still
being capable of passing through the cased borehole. Examples of bi-center
bits may be
found in U.S. Pat. Nos. 6,039,131 and 6,269,893.
[0009] As described above, winged reamers and bi-center bits each include
underreamer
portions that are eccentric. A number of disadvantages are associated with
this design.
First, before drilling can continue, cement and float equipment at the bottom
of the
lowermost casing string must be drilled out. However, the pass-through
diameter of the
drilling assembly at the eccentric underreamer portion barely fits within the
lowermost
casing string. Therefore, off-center drilling is required to drill out the
cement and float
equipment to ensure that the eccentric underreamer portions do not damage the
casing.
Accordingly, it is desirable to provide an underreamer that collapses while
the drilling
assembly is in the casing and that expands to underream the previously drilled
borehole
to the desired diameter below the casing.
[0010] Further, due to directional tendency problems, these eccentric
underreamer
portions have difficulty reliably underreaming the borehole to the desired
diameter. With
respect to a bi-center bit, the eccentric underreamer bit tends to cause the
pilot bit to
wobble and undesirably deviate off center, thereby pushing the pilot bit away
from the
preferred trajectory of drilling the well path. A similar problem is
experienced with
respect to winged reamers, which only underream the borehole to the desired
diameter if
the pilot bit remains centralized in the borehole during drilling.
Accordingly, it is
desirable to provide an underreamer that remains concentrically disposed in
the borehole
while underreaming the previously drilled borehole to the desired diameter.
[0011] In drilling operations, it is conventional to employ a tool known as a
"stabilizer."
In standard boreholes, traditional stabilizers are located in the drilling
assembly behind
the drill bit for controlling the trajectory of the drill bit as drilling
progresses. Traditional
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= 1 stabilizers control drilling in a desired direction, whether the direction
is along a straight
borehole or a deviated borehole.
[0012] In a conventional rotary drilling assembly, a drill bit may be mounted
onto a
lower stabilizer, which is disposed approximately 5 feet above the bit.
Typically the
lower stabilizer is a fixed blade stabilizer that includes a plurality of
concentric blades
extending radially outwardly and spaced azimuthally around the circumference
of the
stabilizer housing. The outer edges of the blades are adapted to contact the
wall of the
existing cased borehole, thereby defining the maximum stabilizer diameter that
will pass
through the casing. A plurality of drill collars extends between the lower
stabilizer and
other stabilizers in the drilling assembly. An upper stabilizer is typically
positioned in
the drill string approximately 30-60 feet above the lower stabilizer. There
could also be
additional stabilizers above the upper stabilizer. The upper stabilizer may be
either a
fixed blade stabilizer or, more recently, an adjustable blade stabilizer that
allows the
blades to be collapsed into the housing as the drilling assembly passes
through the casing
and then expanded in the borehole below. One type of adjustable concentric
stabilizer is
manufactured by Andergauge U.S.A., Inc., Spring, Tex. and is described in U.S.
Pat. No.
4,848,490. Another type of adjustable concentric stabilizer is manufactured by
Halliburton, Houston, Texas and is described in U.S. Pat. Nos. 5,318,137;
5,318,138; and
5,332,048.
[0013] In operation, if only the lower stabilizer was provided, a "fulcrum"
type assembly
would be present because the lower stabilizer acts as a fulcrum or pivot point
for the bit.
Namely, as drilling progresses in a deviated borehole, for example, the weight
of the drill
collars behind the lower stabilizer forces the stabilizer to push against the
lower side of
the borehole, thereby creating a fulcrum or pivot point for the drill bit.
Accordingly, the
drill bit tends to be lifted upwardly at an angle, i.e. build angle.
Therefore, a second
stabilizer is provided to offset the fulcrum effect. Namely, as the drill bit
builds angle
due to the fulcrum effect created by the lower stabilizer, the upper
stabilizer engages the
lower side of the borehole, thereby causing the longitudinal axis of the bit
to pivot
downwardly so as to drop angle. A radial change of the blades of the upper
stabilizer can
control the pivoting of the bit on the lower stabilizer, thereby providing a
two-
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dimensional, gravity based steerable system to control the build or drop angle
of the
drilled borehole as desired.
[0014] When an underreamer or a winged reamer tool is operating behind a
conventional
bit to underream the borehole, that tool provides the same fulcrum effect to
the bit as the
lower stabilizer in a standard borehole. Similarly, when underreaming a
borehole with a
bi-center bit, the eccentric underreamer bit provides the same fulcrum effect
as the lower
stabilizer in a standard borehole. Accordingly, in a drilling assembly
employing an
underreamer, winged reamer, or a bi-center bit, a lower stabilizer is not
typically
provided. However, to offset the fulcrum effect imparted by to the drill bit,
it would be
advantageous to provide an upper stabilizer capable of controlling the
inclination of the
drilling assembly in the underreamed section of borehole.
[0015] In particular, it would be advantageous to provide an upper stabilizer
that engages
the wall of the underreamed borehole to keep the centerline of the pilot bit
centered
within the borehole. When utilized with an eccentric underreamer that tends to
force the
pilot bit off center, the stabilizer blades would preferably engage the
opposite side of the
expanded borehole to counter that force and keep the pilot bit on center.
SUMMARY OF THE INVENTION
[0016] In one aspect, embodiments disclosed herein relate to an expandable
downhole
tool for use in a drilling assembly positioned within a wellbore. The
expandable
downhole tool includes a tool body having an axial flowbore extending
therethrough and
a moveable arm. The moveable arm includes a roller structure including cutters
and
rotatably mounted on the moveable arm. The moveable arm is configured to move
outwardly in response to actuation of the expandable downhole tool.
[0017] In another aspect, embodiments disclosed herein relate to a moveable
arm for an
expandable downhole tool. The moveable arm includes a body, a roller structure
including cutters and rotatably mounted on the body. The moveable arm is
configured be
moveably received into a tool body of the expandable downhole tool.
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100181 In another aspect, embodiments disclosed herein relate to a method of
underreaming a wellbore to form an enlarged borehole. The method includes
using a
drill bit to drill the wellbore, disposing an expandable underreamer above the
drill bit,
using the expandable underreamer to enlarge the borehole, and disposing an
expandable
roller reamer above the first expandable underreamer, wherein the expandable
roller
reamer comprises a moveable arm comprising a roller structure comprising
cutters and
rotatably mounted on the moveable arm. The method further includes actuating
the
expandable roller reamer such that the cutters disposed on the roller
structure contact the
enlarged borehole.
[0019] Other aspects and advantages of the invention will be apparent from the
following
description and the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a schematic, cross-sectional view of a drilling assembly;
[00211 FIG. 2 is a schematic, cross-sectional view of another drilling
assembly;
[0022] FIG. 3 is a schematic, cross-sectional view of another drilling
assembly;
[0023] FIG. 4 is a cross-sectional elevation view of one embodiment of the
expandable
tool of the present invention, showing the moveable arms in the collapsed
position;
[0024] FIG. 5 is a cross-sectional elevation view of the expandable tool of
FIG. 4,
showing the moveable arms in the expanded position;
[0025] FIG. 6 is a perspective view of a "blank" arm for the expandable tool
of FIG. 4;
[0026] FIG. 7 is a top view of an exemplary arm for the expandable tool of
FIG. 4
including a wear pad and cutting structures for back reaming and underreaming;
[0027] FIG. 8 is a side elevation view of the arm of FIG. 7;
[0028] FIG. 9 is a perspective view of the arm of FIG. 7;
[0029] FIG. 10 is a perspective view of the drive ring of the expandable tool
of FIG. 4;
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[0030] FIG. 11 is a cross-sectional elevation view of an alternative
embodiment of the
expandable tool of the present invention, showing the moveable arms in the
collapsed
position; and
[0031] FIG. 12 is a cross-sectional elevation view of the alternative
embodiment of FIG.
11, showing the moveable arms in the expanded position.
[0032] FIG. 13 is a perspective view of an embodiment of a moveable arm having
a
roller reamer structure.
[0033] FIGS. 14a-c are a perspective view of an embodiment of a moveable arm
having a
roller reamer structure.
DETAILED DESCRIPTION
[0034] The present disclosure relates to a roller reamer for stabilizing a
drillstring and
reducing torque. The present invention is susceptible to embodiments of
different forms.
There are shown in the drawings, and herein will be described in detail,
specific
embodiments of the present invention with the understanding that the
disclosure is to be
considered an exemplification of the principles of the invention, and is not
intended to
limit the invention to that illustrated and described herein.
[0035] In particular, various embodiments of the present invention provide a
number of
different constructions and methods of operation. Each of the various
embodiments of
the present invention may be used to enlarge a borehole, or to provide
stabilization in a
previously enlarged borehole, or in a borehole that is simultaneously being
enlarged. The
embodiments of the expandable tool of the present invention may be utilized as
an
underreamer, or as a stabilizer behind a bi-center bit, or as a stabilizer
behind a winged
reamer or underreamer following a conventional bit. The embodiments of the
present
invention also provide a plurality of methods for use in a drilling assembly.
It is to be
fully recognized that the different teachings of the embodiments disclosed
herein may be
employed separately or in any suitable combination to produce desired results.
[0036] It should be appreciated that the expandable tool described with
respect to the
Figures that follow may be used in many different drilling assemblies. The
following
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exemplary systems provide only some of the representative assemblies within
which the
present invention may be used, but these should not be considered the only
assemblies.
In particular, the embodiments of the expandable tool of the present invention
may be
used in any assembly requiring an expandable underreamer and/or stabilizer for
use in
controlling the directional tendencies of a drilling assembly in an expanded
borehole.
[0037] FIGS. 1-3 show various exemplary drilling assemblies within which
embodiments
of the present invention may be utilized. Referring initially to FIG. 1, a
section of a
drilling assembly generally designated as 100 is shown drilling into the
bottom of a
formation 10 with a conventional drill bit 110 followed by an underreamer 120.
Separated from the underreamer 120 by one or more drill collars 130 is a
stabilizer 150
that controls the directional tendencies of the drilling assembly 100 in the
underreamed
borehole 25. This section of the drilling assembly 100 is shown at the bottom
of
formation 10 drilling a borehole 20 with the conventional drill bit 110, while
the
underreamer cutting arms 125 are simultaneously opening a larger diameter
borehole 25
above. The drilling assembly 100 is operating below any cased portions of the
well.
100381 As described previously, the underreamer 120 tends to provide a fulcrum
or pivot
effect to the drill bit 110, thereby requiring a stabilizer 150 to offset this
effect. In the
drilling assembly 100, various embodiments of the expandable tool of the
present
invention are provided in the positions of both the underreamer 120 and the
stabilizer
150. In one embodiment, the stabilizer 150 would also include cutting
structures to
ensure that the larger borehole 25 is enlarged to the proper diameter.
However, any
conventional underreamer may alternatively be utilized with one embodiment of
the
present invention provided in the position of stabilizer 150 in the drilling
assembly 100.
Further, one embodiment of the present invention may be utilized in the
position of
underreamer 120, and a conventional stabilizer may be utilized in the position
of
stabilizer 150.
[0039] Referring now to FIG. 2, where like numerals represent like components,
a
drilling assembly 200 is shown disposed within formation 10, below any cased
sections
of the well. The drilling assembly 200 is drilling a borehole 20 utilizing a
conventional
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drill bit I 10 followed by a winged reamer 220. The winged reamer 220 may be
separated
from the drill bit 110 by one or more drill collars 130, but preferably the
winged reamer
220 is connected directly above the drill bit 110. Upstream of the winged
reamer 220,
separated by one or more drill collars 130, is a stabilizer 150 that controls
the directional
tendencies of the drilling assembly 200 in the underreamed borehole 25. The
drill bit 110
is shown at the bottom of the formation 10 drilling a borehole 20, while the
wing
component 225 of the winged reamer 220 is simultaneously opening a larger
diameter
borehole 25 above. In the assembly 200, one embodiment of the present
invention would
be located in the position of stabilizer 150. In one embodiment of assembly
200, the
stabilizer 150 would also include cutting structures to ensure that the larger
borehole 25 is
enlarged to the proper diameter.
[0040] Referring to FIG. 3, where like numerals represent like components,
again a
drilling assembly 300 is shown disposed within formation 10, below any cased
sections
of the well. The drilling assembly 300 utilizes a bi-center bit 320 that
includes a pilot bit
310 and an eccentric underreamer bit 325. As the pilot bit 310 drills the
borehole 20, the
eccentric underreamer bit 325 opens a larger diameter borehole 25 above. The
bi-center
bit 320 is separated by one or more drill collars 130 from a stabilizer 150
designed to
control the directional tendencies of the bi-center bit 320 in the underreamed
borehole 25.
Again, the function of the stabilizer 150 is to offset the fulcrum or pivot
effect created by
the eccentric underreamer bit 325 to ensure that the pilot bit 310 stays
centered as it drills
the borehole 20. In one embodiment of the drilling assembly 300, one
embodiment of the
expandable tool of the present invention would be located in the position of
stabilizer
150. In another embodiment of assembly 300, the stabilizer 150 would also
include
cutting structures to ensure that the larger borehole 25 is enlarged to the
proper diameter.
[0041] Referring now to FIGS. 4 and 5, one embodiment of the expandable tool
of the
present invention, generally designated as 500, is shown in a collapsed
position in FIG. 4
and in an expanded position in FIG. 5. The expandable tool 500 comprises a
generally
cylindrical tool body 510 with a flowbore 508 extending therethrough. The tool
body
510 includes upper 514 and lower 512 connection portions for connecting the
tool 500
into a drilling assembly. In approximately the axial center of the tool body
510, one or
CA 02642416 2008-10-30
more pocket recesses 516 are formed in the body 510 and spaced apart
azimuthally
around the circumference of the body 510. The one or more recesses 516
accommodate
the axial movement of several components of the tool 500 that move up or down
within
the pocket recesses 516, including one or more moveable, non-pivotable tool
arms 520.
Each recess 516 stores one moveable arm 520 in the collapsed position. In one
embodiment, the expandable tool includes three moveable arms 520 disposed
within
three pocket recesses 516. In the discussion that follows, the one or more
recesses 516
and the one or more arms 520 may be referred to in the plural form, i.e.
recesses 516 and
arms 520. Nevertheless, it should be appreciated that the scope of the present
invention
also comprises one recess 516 and one arm 520.
[0042] The recesses 516 further include angled channels 518 that provide a
drive
mechanism for the moveable tool arms 520 to move axially upwardly and radially
outwardly into the expanded position of FIG. 5. A biasing spring 540 may be
included to
bias the arms 520 to the collapsed position of FIG. 4. The biasing spring 540
is disposed
within a spring cavity 545 and covered by a spring retainer 550. Retainer 550
is locked
in position by an upper cap 555. A stop ring 544 is provided at the lower end
of spring
540 to keep the spring 540 in position.
[0043] Below the moveable arms 520, a drive ring 570 is provided that includes
one or
more nozzles 575. An actuating piston 530 that forms a piston cavity 535,
engages the
drive ring 570. A drive ring block 572 connects the piston 530 to the drive
ring 570 via
bolt 574. The piston 530 is adapted to move axially in the pocket recesses
516. A lower
cap 580 provides a lower stop for the axial movement of the piston 530. An
inner
mandrel 560 is the innermost component within the tool 500, and it slidingly
engages a
lower retainer 590 at 592. The lower retainer 590 includes ports 595 that
allow drilling
fluid to flow from the flowbore 508 into the piston chamber 535 to actuate the
piston 530.
[0044] A threaded connection is provided at 556 between the upper cap 555 and
the inner
mandrel 560 and at 558 between the upper cap 555 and body 510. The upper cap
555
sealingly engages the body 510 at 505, and sealingly engages the inner mandrel
560 at
562 and 564. A wrench slot 554 is provided between the upper cap 555 and the
spring
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retainer 550, which provides room for a wrench to be inserted to adjust the
position of the
spring retainer 550 in the body 510. Spring retainer 550 connects at 551 via
threads to
the body 510. Towards the lower end of the spring retainer 550, a bore 552 is
provided
through which a bar can be placed to prevent rotation of the spring retainer
550 during
assembly. For safety purposes, a spring cover 542 is bolted at 546 to the stop
ring 544.
The spring cover 542 prevents personnel from incurring injury during assembly
and
testing of the tool 500.
[0045] The moveable arms 520 include pads 522, 524, and 526 with structures
700, 800
that engage the borehole when the arms 520 are expanded outwardly to the
expanded
position of the tool 500 shown in FIG. 5. Below the arms 520, the piston 530
sealingly
engages the inner mandrel 560 at 566, and sealingly engages the body 510 at
534. The
lower cap 580 is threadingly connected to the body and to the lower retainer
590 at 582,
584, respectively. A sealing engagement is also provided at 586 between the
lower cap
580 and the body 510. The lower cap 580 provides a stop for the piston 530 to
control the
collapsed diameter of the tool 500.
[0046] Several components are provided for assembly rather than for functional
purposes. For example, the drive ring 570 is coupled to the piston 530, and
then the drive
ring block 572 is boltingly connected at 574 to prevent the drive ring 570 and
the piston
530 from translating axially relative to one another. The drive ring block
572, therefore,
provides a locking connection between the drive ring 570 and the piston 530.
[0047] FIG. 5 depicts the tool 500 with the moveable arms 520 in the maximum
expanded position, extending radially outwardly from the body 510. Once the
tool 500 is
in the borehole, it is only expandable to one position. Therefore, the tool
500 has two
operational positions--namely a collapsed position as shown in FIG. 4 or an
expanded
position as shown in FIG. 5. However, the spring retainer 550, which is a
threaded
sleeve, can be adjusted at the surface to limit the full diameter expansion of
arms 520.
The spring retainer 550 compresses the biasing spring 540 when the too1500 is
collapsed,
and the position of the spring retainer 550 determines the amount of expansion
of the
arms 520. The spring retainer 550 is adjusted by a wrench in the wrench slot
554 that
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rotates the spring retainer 550 axially downwardly or upwardly with respect to
the body
510 at threads 551. The upper cap 555 is also a threaded component that locks
the spring
retainer 550 once it has been positioned. Accordingly, one advantage of the
present tool
is the ability to adjust at the surface the expanded diameter of the tool 500.
Unlike
conventional underreamer tools, this adjustment can be made without replacing
any
components of the tool 500.
[0048] In the expanded position shown in FIG. 5, the arms 520 will either
underream the
borehole or stabilize the drilling assembly, depending upon how the pads 522,
524 and
526 are configured. In the configuration of FIGS. 5, cutting structures 700 on
pads 526
would underream the borehole. Wear buttons 800 on pads 522 and 524 would
provide
gauge protection as the underreaming progresses. Hydraulic force causes the
arms 520 to
expand outwardly to the position shown in FIG. 5 due to the differential
pressure of the
drilling fluid between the flowbore 508 and the annulus 22.
[0049) The drilling fluid flows along path 605, through ports 595 in the lower
retainer
590, along path 610 into the piston chamber 535. The differential pressure
between the
fluid in the flowbore 508 and the fluid in the borehole annulus 22 surrounding
tool 500
causes the piston 530 to move axially upwardly from the position shown in FIG.
4 to the
position shown in FIG. 5. A small amount of flow can move through the piston
chamber
535 and through nozzles 575 to the annulus 22 as the tool 500 starts to
expand. As the
piston 530 moves axially upwardly in pocket recesses 516, the piston 530
engages the
drive ring 570, thereby causing the drive ring 570 to move axially upwardly
against the
moveable arms 520. The arms 520 will move axially upwardly in pocket recesses
516
and also radially outwardly as the arms 520 travel in channels 518 disposed in
the body
510. In the expanded position, the flow continues along paths 605, 610 and out
into the
annulus 22 through nozzles 575. Because the nozzles 575 are part of the drive
ring 570,
they move axially with the arms 520. Accordingly, these nozzles 575 are
optimally
positioned to continuously provide cleaning and cooling to the cutting
structures 700
disposed on surface 526 as fluid exits to the annulus 22 along flow path 620.
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[0050] The underreamer tool 500 of the one embodiment of the present invention
solves
the problems experienced with bi-center bits and winged reamers because it is
designed
to remain concentrically disposed within the borehole. In particular, the tool
500 of the
present invention preferably includes three extendable arms 520 spaced apart
circumferentially at the same axial location on the tool 510. In one
embodiment, the
circumferential spacing would be 120 apart. This three arm design provides a
full gauge
underreaming tool 500 that remains centralized in the borehole at all times.
[0051] Embodiments of the present invention may provide hydraulic indication
at the
surface, thereby inforrning the operator whether the tool is in the contracted
position
shown in FIG. 4, or the expanded position shown in FIG. 5. Namely, in the
contracted
position, the flow area within piston chamber 535 is smaller than the flow
area within
piston chamber 535 when the tool 500 is in the expanded position shown in FIG.
5.
Therefore, in the expanded position, the flow area in chamber 535 is larger,
providing a
greater flow area between the flowbore 508 and the wellbore annulus 22. In
response,
pressure at the surface will decrease as compared to the pressure at the
surface when the
tool 500 is contracted. This decrease in pressure indicates that the too1500
is expanded.
[0052] FIGS. 6-10 provide more detail regarding the moveable arms 520 and
drive ring
570 of FIGS. 4 and 5. FIG. 6 shows a "blank" arm 520 with no cutting
structures or
stabilizing structures attached to pads 522, 524, 526. The arm 520 is shown in
isometric
view to depict a top surface 521, a bottom surface 527, a front surface 665, a
back surface
660, and a side surface 528. The top surface 521 and the bottom surface 527
are
preferably angled, as described in more detail below. The arm 520 preferably
includes
two upper pads 522, one middle pad 524, and two lower pads 526 disposed on the
front
surface 665 of the arm 520. The arm 520 also includes extensions 650 disposed
along
each side 528 of arm 520. The extensions 650 preferably extend upwardly at an
angle
from the bottom 527 of the arm 520 towards pads 522, 524 and 526. The
extensions 650
protrude outwardly from the arm 520 to fit within corresponding channels 518
in the
pocket recess 516 of the tool body 510, as shown in FIGS. 4 and 5. The
interconnection
between the arm extensions 650 and the body channels 518 increases the surface
area of
contact between the moveable arms 520 and the tool body 510, thereby providing
a more
14
CA 02642416 2008-10-30
robust expandable tool 500 as compared to prior art tools. The arm 520
depicted in FIG.
6 is a blank version of either an underreamer cutting arm or a stabilizer arm.
By
changing the structures disposed on pads 522, 524 and 526, the tool 500 is
converted
from an underreamer to a stabilizer or vice versa, or to a combination
underreamer/stabilizer.
[0053] Referring now to FIGS. 7, 8 and 9, an exemplary arm 520 is shown that
includes
two sets of cutting structures 700, 710. FIG. 7 depicts the arm 520 from a top
perspective, FIG. 8 provides an elevational side view, and FIG. 9 shows an
isometric
perspective. The top surface 521 and the bottom surface 527 of the arm 520 are
preferably angled in the same direction as best shown in FIG. 7. These
surfaces 521, 527
are designed to prevent the arm 520 from vibrating when pads 522, 524 and 526
engage
the borehole. Namely, when pads 522, 524 and 526 engage the borehole, the arms
520
are held in compression by the piston 530. The angled top surface 521 and the
angled
bottom surface 527 bias the arms 520 to the trailing side of the pocket
recesses 516 to
minimize vibration.
[0054] In the top view of FIG. 7, pads 522 comprise cutting structures 710
such that the
arm 520 provides back reaming capabilities. Back reaming is pulling the tool
500
upwardly in the borehole while underreaming. Pad 524 is preferably covered
with wear
buttons 800 that provide a stabilizing and gauge protection function. Pads 526
comprise
cutting structures 700 for underreaming. In the side view of FIG. 8, the
extensions 650
that fit within channels 518 of the body 510 are shown extending upwardly at
an angle
along the side 528 from the back surface 660 of the arm 520 towards pads 522,
524 and
526. FIG. 9 shows the same arm 520 in isometric view.
[0055] To change the arm 520 shown in FIGS. 7, 8, and 9 from a back reaming
and
underreaming arm to simply an underreaming arm, the back reaming cutting
structures
710 would be replaced with wear buttons, such as buttons 800. This
configuration would
result in the underreaming arm 520 shown in FIGS. 4 and 5. Modifying the tool
500
from an underreamer to a stabilizer simply requires providing stabilizing
structures on all
of the pads 522, 524 and 526. As a stabilizer, surfaces 522, 524, and 526
would be
CA 02642416 2008-10-30
covered with a dense plurality of wear buttons 800 without any cutting
structures. The
material for the wear buttons 800 may be, for example, a tungsten carbide or
diamond
material, which provides good wear capabilities. In an alternative embodiment,
the pads
522, 524, and 526 may be coated with a hardened material called TCI 300H
hardfacing.
[0056] Accordingly, the pads 522, 524, 526 could comprise a variety of
structures and
configurations utilizing a variety of different materials. When the tool is
used in an
underreaming function, a variety of different cutting structures 700 could be
provided on
surfaces 526, depending upon the formation characteristics. Preferably, the
cutting
structures 700, 710 for underreaming and back reaming, respectively, are
specially
designed for the particular cutting function. More preferably, the cutting
structures 700,
710 comprise the cutting structures disclosed and claimed in co-pending U.S.
patent
application Ser. No. 09/924,961, filed Aug. 8, 2001, entitled "Advanced
Expandable
Reaming Tool," assigned to Smith International, Inc., which is hereby
incorporated
herein by reference.
[0057] Referring now to FIG. 10, additional advantages of one or more
embodiments of
the present invention are provided by the one or more nozzles 575 disposed in
the drive
ring 570. The underreamer/stabilizer preferably includes three moveable arms
520
spaced apart circumferentially at the same axial location along the tool body
510. In one
embodiment, the three moveable arms 520 are spaced 120 circumferentially.
This
arrangement of the arms 520 is preferred to centralize the tool 500 in the
borehole. The
drive ring 570 is moveable with the arms 520 and preferably includes three
extended
portions 576 spaced 120 circumferentially with angled nozzles 575
therethrough that
are designed to direct drilling fluid to the cutting structures 700 of the
underreamer at
surfaces 526. The boreholes 578 in the extended portions 576 adjacent nozzles
575
accept bolts 574 to connect the drive ring 570 to the drive ring block 572 and
piston 530.
An aperture 571 is disposed through the center of the drive ring 570 to enable
a
connection to the piston 530. Because the drive ring 570 is connected to the
piston 530,
it moves with the piston 530 to push the moveable arms 520 axially upwardly
and
outwardly along the channels 518 to the expanded position. Accordingly,
because drive
ring 570 moves with the arms 520, the nozzles 575 continuously provide
drilling fluid to
16
CA 02642416 2008-10-30
' : " . .
the cutting structures 700 on the underreamer surfaces 526. The nozzles 575
are
optimally placed to move with and follow the cutting structures 700 and
thereby assure
that the cutters 700 are properly cleaned and cooled at all times.
[0058] FIGS. 11 and 12 depict a second embodiment of the present invention,
generally
designated as 900, in the collapsed and expanded positions, respectively. Many
components of tool 900 are the same as the components of embodiment 500, and
those
components maintain the same reference numerals. There are, however, several
differences. The inner mandrel 560 of the first embodiment tool 500 is
replaced by a
stinger assembly 910, preferably comprising an upper inner mandrel 912, a
middle inner
mandrel 914, and a lower inner mandrel 916. The lower inner mandrel 916
includes
ports 920 that must align with ports 595 in the lower retainer 590 before
fluid can enter
piston chamber 535 to actuate the piston 530. As shown in FIG. 11, fluid flows
through
the flowbore 508 of tool 900, along pathway 605 depicted by the arrows.
Because the
ports 920 of the lower inner mandrel 916 do not align with the ports 595 of
the lower
retainer 590, the fluid continues flowing along path 605, past ports 595, down
through the
tool 900.
[0059] The tool 900 is selectively actuated utilizing an actuator (not shown),
which
aligns the ports 920 with the ports 595 to enable the expandable tool to move
from the
contracted position shown in FIG. 11 to the expanded position shown in FIG.
12. Below
lower inner mandrel 916, a bottom spring 930 is disposed within a bottom
spring
chamber 935 and held within the body 510 by a bottom spring retainer 950.
Bottom
spring retainer 950 threadingly connects at 952 to the lower retainer 590. The
spring 930
biases the stinger assembly 910 upwardly such that stinger 910 must be forced
downwardly by an actuator to overcome the force of bottom spring 930. By
moving the
stinger 910 downwardly, the ports 920 disposed circumferentially around the
bottom of
lower inner mandrel 916 align with the ports 595 of lower retainer 590 that
lead into
piston chamber 535.
[0060] FIG. 12 shows the tool 900 in an expanded position. In this position,
drilling fluid
flows through the flowbore 508, along pathway 605. However, because stinger
910 has
17
CA 02642416 2008-10-30
r . .
been actuated downwardly against the force of bottom spring 930 by an
actuator, the
ports 920 in lower inner mandre1916 now align with ports 595 in the lower
retainer 590.
Therefore, when the drilling fluid proceeds downwardly along flow path 605
through the
flowbore 508 to reach ports 920, it will flow through ports 920, 595 and into
the piston
chamber 535 as depicted by flow arrows 610.
[0061] Due to the differential pressure between the flowbore 508 and the
wellbore
annulus 22 surrounding tool 900, the fluid flowing along pathway 610 will
actuate the
piston 530 upwardly against the force of spring 540. The piston 530 will push
the drive
ring 570, which will push the arms 520 axially upwardly and outwardly as the
extensions
650 on the arms 520 move along channels 518 in the body 510. Once the fluid
flows
through the nozzles 575 in the drive ring 570, it exits at an angle along
pathway 620 to
cool and clean the cutting structures 700 disposed on surfaces 526 that
underream the
borehole. Accordingly, the second embodiment 900 of FIGS. 11 and 12 is capable
of
being selectively actuated. Namely, by engaging the upper surface 975 of
stinger 910
with an actuator, the too1900 can be selectively actuated at the election of
the operator to
align the ports 920 and 595. A suitable actuator is the flow switch described
and claimed
in U.S. Pat. No. 6,289,999 entitled "Fluid Flow Control Devices and Methods
for
Selective Actuation of Valves and Hydraulic Drilling Tools," hereby
incorporated herein
by reference.
[0062] Referring again to FIGS. 11 and 12, typically a gap is provided between
the upper
end 975 of the stinger 910 and the actuator when the tool is in the collapsed
position.
That gap length must be maintained to ensure that actuation occurs only when
it is meant
to occur. Accordingly, upper inner mandrel 912 may include an adjustment ring
portion
918, which is just a spacer ring that makes up any discrepancies in the area
between the
upper inner mandrel 912 and the middle inner mandrel 914 such that the
appropriate gap
dimension can be maintained.
[0063] As one of ordinary skill in the art will readily appreciate, any
actuating
mechanism can be utilized to selectively actuate the tool 900 of FIGS. 11 and
12.
However, the flow switch provides the advantage of additional hydraulic
indications to
18
CA 02642416 2008-10-30
' . ' . .
the surface, in addition to the pressure indications provided by the increased
flow area in
the piston chamber 535 when the tool 900 is in the expanded position of FIG.
12.
Namely, the flow switch includes an uplink pulser capable of providing
position and
status information to the surface via mud pulse telemetry. Accordingly, one
embodiment
comprises the too1900 of FIGS. 11 and 12, and more preferably comprises the
too1900 in
combination with the referenced flow switch.
100641 In operation, an expandable tool 500 or 900 is lowered through casing
in the
collapsed position shown in FIGS. 4 and 11, respectively. The first embodiment
of the
tool 500 would then be expanded automatically when drilling fluid flows
through
flowbore 508, and the second embodiment of the too1900 would be expanded only
after
selectively actuating the tool 900. Whether the selective actuation feature is
present or
not, the tools 500, 900 expand due to differential pressure between the flow
bore 508 and
the wellbore annulus 22 acting on the piston 530. That differential pressure
may be in the
range of 800 to 1,500 psi. Therefore, differential pressure working across the
piston 530
will cause the one or more arms 520 of the tool to move from a collapsed to an
expanded
position against the force of the biasing spring 540.
[0065J Before the drilling assembly is lowered into the borehole, the function
of the
present invention as either an underreamer or as a stabilizer would be
determined.
Referring again to FIG. 1, one example would be to use either embodiment of
the tool
500, 900 in the position of underreamer 120, and preferably to use the second
embodiment of the tool 900 in the position of stabilizer 150. As another
example,
referring to FIGS. 2 and 3, if a winged reamer 220 or a bi-center bit 320 is
used instead of
an underreamer 120, the second embodiment of the too1900 would preferably be
used in
the position of stabilizer 150. As an underreamer, one or more embodiments of
the
present invention are capable of underreaming a borehole to a desired
diameter. As a
stabilizer, one or more embodiments of the present invention provide
directional control
for the assembly 100, 200, 300 within the underreamed borehole 25.
[00661 Turning to FIG. 13, a moveable ann 820 with a roller structure 162 in
accordance
with another embodiment is shown. The moveable arm 820 shown in FIG. 13 is
similar
19
CA 02642416 2008-10-30
. . . . ,
in structure to the blank arm shown in FIG. 6. A body 830 includes extensions
650
formed on the sides and configured to fit within corresponding channels of the
tool body,
such as the embodiment shown in FIGS. 4 and 5. The body 830 is further
configured to
accommodate the roller structure 162 rotatably attached thereto. The shape of
the roller
structure 162 may be, for example, cylindrical or fiusto-conical. Cutting
structures 163
are distributed azimuthally about the roller structure 162. The cutting
structures 163 may
be integrally formed with the roller structure 162 or provided as inserts in
corresponding
pockets formed in the roller structure 162. If provided as inserts, any
suitably hard
material may be used, such as, for example, tungsten carbide or diamond
material. The
cutting structures 163 may be, for example, bullet-shaped. Those having
ordinary skill in
the art will appreciate that the shape of the cutting structures 163 may vary
without
departing from the scope of the present disclosure.
[0067] The expandable roller reamer may include a plurality of moveable arms
azimuthally spaced around the tool body. To balance the forces on the
expandable roller
reamer and better stabilize the drillstring, the plurality of moveable arms
may be
circumferentially spaced apart around the tool body. For example, in one
embodiment,
the expandable roller reamer may include three moveable arms with roller
structures
spaced 120 apart.
[0068] In the embodiment shown in FIG. 13, the roller structure 162 is formed
as a
sleeve disposed on a roller pin 161. A set screw 165 fixes the roller
structure 162 relative
to the roller pin 161. To attach the roller pin 161 to the moveable ann 820,
roller mounts
171 are provided at opposing ends of the roller pin 161 and disposed in
corresponding
pockets formed in the moveable arm 820. The roller mounts 171 may be attached
to the
moveable arm 820 using, for example, bolts 172. Bearing assemblies (not shown)
may
be provided within the roller mounts 171.
[0069] The structure of the moveable arm 820 of FIG. 13 may provide several
advantages. The moveable arm 820 may be configured to be interchangeable with
other
moveable arms disclosed herein in order for the same tool body to be useable
for
different applications by changing out the moveable arms, which can be
performed at a
CA 02642416 2008-10-30
= ~ ' .
drilling site with readily available tools. Interchangeability of moveable
arms also
reduces manufacturing costs by increasing quantities of the tool body.
Further, the
various types of moveable arms may be manufactured with the common dimensions
(e.g.
extensions 650) before being finished with specialized features, such as
pockets to
accommodate the roller pin.
[00701 Figures 14a-c, show another embodiment of a roller structure in
accordance with
disclosed features. In Figure 14b, blades 921, may form the cutting structure,
as opposed
to inserts, or other cutting elements. The blades may be formed from a super
hard
material, such as tungsten carbide, or may be formed from a matrix material,
and be
impregnated with another material, such as diamond. Thus, in one embodiment,
the
blades 921 are diamond impregnated matrix blades. Those having ordinary skill
in the
art will appreciate that a number of other materials may be used as the
cutting structure in
this fashion. In addition, a combination of inserts, shown at 922, and blades
may be used
together to form a cutting structure. As with Figure 13, the structure may be
bolted on, or
otherwise attached. In addition, wear features 923 may be added to contact the
hole wall
for stabilization purposes. These wear features 923 may comprise a super hard
material,
such as tungsten carbide. Figures 14a and 14c show other views of the
embodiment.
[0071] Although interchangeability is a potential advantage, those having
ordinary skill
in the art will appreciate that an expandable roller reamer may provide other
advantages
associated with stabilizing the drillstring. For example, the expandable
roller reamer may
be deployed above another expandable reamer on the drillstring. The outer
diameter of
the expandable roller reamer can be configured to substantially match or
slightly exceed
the outer diameter of the expandable reamer. By so doing, the expandable
roller reamer
is able to smooth the wellbore and provide active stabilization of the
drillstring during
drilling operations. While contacting the wall of the wellbore, the roller
structures freely
roll rather than drag, thereby reducing torque on the drilistring. Further,
the diameter of
the expandable roller reamer may be reduced to later pull the drilistring from
the
wellbore, thereby reducing the risk of the drillstring being stuck in the
wellbore.
21
CA 02642416 2008-10-30
. # ~ .
[0072] While the invention has been described with respect to a limited number
of
embodiments, those skilled in the art, having benefit of this disclosure, will
appreciate
that other embodiments can be devised which do not depart from the scope of
the
invention as disclosed herein. Accordingly, the scope of the invention should
be limited
only by the attached claims.
22
