U.S. patent application number 14/065150 was filed with the patent office on 2014-04-24 for reamer tool positionable in a wellbore.
This patent application is currently assigned to HALLIBURTON ENERGY SERVICES, INC.. The applicant listed for this patent is HALLIBURTON ENERGY SERVICES, INC.. Invention is credited to John Ransford Hardin, JR., Jean-Pierre Lassoie.
Application Number | 20140110179 14/065150 |
Document ID | / |
Family ID | 47358244 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140110179 |
Kind Code |
A1 |
Lassoie; Jean-Pierre ; et
al. |
April 24, 2014 |
REAMER TOOL POSITIONABLE IN A WELLBORE
Abstract
Described herein is a reamer tool (100) having a body (105) with
bays (115) in which cutter arms (110) are mounted for deployment
between a stowed position and a deployed position. A deployment
mechanism is provided for deploying the cutter arms from their
stowed position to their deployed position that maintains each
cutter arm in a position that is substantially parallel to a
longitudinal axis of the body (105) whilst in its stowed position
and in its deployed position as well as during its deployment from
its stowed position to its deployed position. A control module
(300) is also described for controlling the deployment of the
cutter arms (110). The control module (300) comprises a motor
(310), a gearing mechanism (315) and a moveable element (320) that
closes a port (385) in a first position and opens the port (385) in
a second position. Fluid flow enters a chamber (340) behind a
piston (170) through the port (385) to allow pressure to build up
before actuating the piston (170) and thereby the deployment
mechanism for the cutter arms (170).
Inventors: |
Lassoie; Jean-Pierre;
(Brussels, BE) ; Hardin, JR.; John Ransford;
(Spring, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HALLIBURTON ENERGY SERVICES, INC. |
HOUSTON |
TX |
US |
|
|
Assignee: |
HALLIBURTON ENERGY SERVICES,
INC.
HOUSTON
TX
|
Family ID: |
47358244 |
Appl. No.: |
14/065150 |
Filed: |
October 28, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/IB2012/055804 |
Oct 22, 2012 |
|
|
|
14065150 |
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Current U.S.
Class: |
175/285 |
Current CPC
Class: |
E21B 44/00 20130101;
E21B 10/322 20130101; E21B 10/32 20130101 |
Class at
Publication: |
175/285 |
International
Class: |
E21B 10/32 20060101
E21B010/32 |
Claims
1. A reamer tool positionable downhole in a wellbore, said tool
comprising: a substantially hollow body having a longitudinal axis
and including an external wall having a first outer diameter; at
least one arm bay formed in a portion of the external wall around
the periphery of the body; at least one expandable arm located in
an associated arm bay and mounted for expansion between a retracted
position within the body and an expanded position in which each
expandable arm describes a second outer diameter which is greater
than the first outer diameter; and at least one expansion mechanism
for expanding an associated expandable arm between the retracted
and expanded positions; wherein each expansion mechanism comprises
two elongate links pivotally connected to the associated expandable
arm at one end position and to its associated arm bay at another
end position, each expandable arm being pivotally mounted at the
two end positions with respect to its associated arm bay so that
each expandable arm is maintained substantially parallel to the
longitudinal axis in both the retracted and expanded positions,
and, during its expansion and retraction between the retracted and
expanded positions.
2. The reamer tool of claim 1, further comprising an actuation
mechanism for activating the expansion mechanism, each expandable
arm being pivotally connected at another end position to the
actuation mechanism.
3. (canceled)
4. (canceled)
5. The reamer tool of claim 1, further comprising at least one
return member for deactivating each expansion mechanism.
6. The reamer tool of claim 5, wherein each return member comprises
a spring biased against the action of the actuating mechanism.
7. The reamer tool of claim 1, further comprising a shoulder block
locatable in each arm bay to limit the expansion of the expandable
arm.
8. The reamer tool of claim 1, wherein the second outer diameter is
up to 1.3 times the first outer diameter.
9. The reamer tool of claim 1, wherein each expandable arm
comprises a cutter arm.
10. An expandable cutter arm for a reamer tool postionable downhole
in a wellbore, the expandable cutter arm comprising at least a
front cutting blade and a back cutting blade, each cutting blade
comprising a plurality of cutting elements, one cutting element on
each of the front cutting blade and the back cutting blade
providing an attack point for the associated cutting blade.
11. The expandable cutter arm of claim 10, further comprising a
first side and a second side located either side of a plane, each
side being spaced at respective predetermined distances from the
plane so that the attack point for the front blade and the attack
point for the back blade are equi-spaced from the plane.
12. The expandable cutter arm of claim 11, wherein the
predetermined distance for the first side is different to the
predetermined distance for the second side.
13. The expandable cutter arm of claim 10, wherein the cutting
elements comprise polycrystalline diamond cutting element.
14. A reamer tool postionable downhole in a wellbore, said tool
having at least one expandable cutter arm comprising: at least a
front cutting blade and a back cutting blade, each cutting blade
comprising a plurality of cutting elements, one cutting element on
each of the front cutting blade and the back cutting blade
providing an attack point for the associated cutting blade; and a
first side and a second side located either side of a plane, each
side being spaced at respective predetermined distances from the
plane so that the attack point for the front blade and the attack
point for the back blade are equi-spaced from the plane, and
wherein the predetermined distance for the first side is different
to the predetermined distance for the second side.
15. A reamer tool positionable downhole in a wellbore, said tool
having a longitudinal axis, the reamer tool comprising at least one
expandable cutter arm, each expandable cutter arm having a
plurality of cutting elements arranged to form at least a front
cutting blade and a back cutting blade, one of the cutting elements
on the front cutting blade and one of the cutting elements on the
back cutting blade providing respective attack points for their
associated cutting blades, wherein the attack point for the front
cutting blade and the attack point for the back cutting blade are
equi-spaced from a plane extending through the longitudinal
axis.
16. The reamer tool of claim 15, further comprising at least one
expansion mechanism for expanding an associated expandable cutter
arm between a retracted position and an expanded position, and an
actuation mechanism for activating each expansion mechanism.
17. The reamer tool of claim 16, wherein each expansion mechanism
comprises at least two elongate links pivotally connected to the
associated expandable cutter arm at one end position and to its
associated arm bay at another end position, each expandable cutter
arm are being pivotally mounted at the two positions with respect
to its associated arm bay so that each expandable cutter arm is
maintained substantially parallel to the longitudinal axis in both
the retracted and expanded positions, and, during expansion and
retraction between the retracted and expanded positions.
18. The reamer tool of claim 17, wherein the expansion mechanism
further comprises a third elongate link pivotally connected to each
expandable cutter arm and to the actuation mechanism, each
expandable cutter arm being pivotally connected at another end
position to the actuation mechanism.
19. The reamer tool of claim 16, wherein the actuation mechanism
comprises a piston.
20. The reamer tool of claim 16, further comprising at least one
return member for deactivating each expansion mechanism.
21. The reamer tool of claim 15, further comprising a shoulder
block locatable in each arm bay to limit the expansion of the
expandable cutter arm.
22. The reamer tool of claim 21, wherein the expandable cutter arm
has an opening range up to 1.3 times an outer diameter of the
reamer tool, the shoulder block limiting the opening in accordance
with its size.
23-33. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to improvements in or relating
to downhole tools, and is more particularly, although not
exclusively, concerned with reamer tools.
BACKGROUND TO THE INVENTION
[0002] Earth formation drilling utilises a long string of drilling
pipes and tools coupled together. All elements of the drilling
string are rotated together in order to rotate a cutting bit at the
end of the drilling sting. The cutting bit creates a hole in a
formation through which the rest of the drilling string moves in a
drilling direction. An under-reamer, coupled between two other
elements of the drilling string, is used to widen the walls of the
hole created by the drill bit. The under-reamer, also known as a
reamer, normally has an overall diameter in its retracted position
which is the same as or less than the diameter of the hole being
drilled. When in its deployed position, cutting elements are moved
away from the body of the under-reamer to define a diameter which
is larger than the diameter of the hole being drilled. As the
under-reamer moves downhole rotating with the drilling string, it
widens the hole in the formation behind the drill bit. In addition,
an under-reamer may be used to open a collapsed formation on its
way back up to the surface.
[0003] WO-A-2005/124094 describes one such under-reamer or reamer
tool. The reamer tool comprises a tubular body having an axial
cavity and housings arranged around its periphery to define
external openings. In each of these openings, a cutter element is
housed which comprises two cutter arms that can be moved between a
retracted position where each cutter element is fully retained
within its associated housing, and an expanded position where each
cutting element extends outside its opening so that more material
can be cut away the walls of the hole in a formation thereby
enlarging its diameter. A drive mechanism is provided within the
tubular body to move the cutter elements between their retracted
and expanded positions.
[0004] In the reamer tool described in WO-A-2005/124094, one cutter
arm is pivotally connected to the tubular body at one end and to
the other cutter arm at the other end, the other cutter arm being
connected to the drive mechanism so that both cutter arms can be
retracted and expanded. The arrangement formed by the two cutter
arms when deployed is a `V`-shape where the vertex of the V is
outside the opening.
[0005] Typically, such reamer tools are operated by the pressure of
fluid passing through the drill string, and in particular, through
the tool section itself. The pressure of fluid is controlled by the
operation of a pump associated with the drill string. In
US-A-2010/0006339, the pressure of fluid passing through the tool
is used to operate the reamer so that it is expanded or retracted
in accordance therewith. Here, the reamer assembly comprises cutter
elements and stabiliser pads mounted for sliding movement on
grooves. In the retracted position, the reamer assembly is housed
within a recess, the reamer assembly being moved to the expanded
position by movement along the grooves so that it is outside the
recess. Fluid pressure is sensed to activate the expansion and
retraction of the reamer.
[0006] US-A-2010/0096191 discloses an under-reaming and
stabilisation tool in which a blade element is moved from a
retracted position to an expanded position by wedge elements
coupled to a drive tube, the wedge elements interact with an
inclined face of the blade element to effect the raising
(expansion) and lowering (retraction) of the blade element relative
to a guide channel. As the drive tube moves along the length of the
tool body, the wedge elements are drawn along therewith and they
slide under the inclined face of the blade element causing radial
movement of the blade element to raise out (expand) out of its
guide channel. Movement of the drive tube in the opposite direction
along the length of the tool body withdraws the wedge elements from
under the inclined face of the blade element allowing radial
movement of the blade element to lower (retract) into its guide
channel. The expansion of the blade element is limited by the
actuation mechanism, that is, the drive tube and wedge elements
coupled thereto.
SUMMARY OF THE INVENTION
[0007] It is therefore an object of the present invention to
provide an improved reamer tool in which the cutter arms or blades
are maintained parallel to the axis of the reamer tool in both its
retracted and deployed positions as well as during expansion and
retraction whilst providing a higher opening range.
[0008] It is a further object of the present invention to provide a
reamer tool in which the opening can be adjusted at the surface in
accordance with a value within the opening range whilst providing a
more efficient reamer tool.
[0009] In accordance with a first aspect of the present invention,
there is provided a reamer tool comprising:
[0010] a substantially hollow body having a longitudinal axis and
including an external wall having a first outer diameter;
[0011] at least one arm bay formed in a portion of the external
wall around the periphery of the body;
[0012] at least one expandable arm located in an associated arm bay
and mounted for expansion between a retracted position within the
body and an expanded position in which each expandable arm
describes a second outer diameter which is greater than the first
outer diameter; and
[0013] at least one expansion mechanism for expanding an associated
expandable arm between the retracted and expanded positions;
[0014] characterised in that each expansion mechanism comprises two
elongate links pivotally connected to the associated expandable arm
at one end position and to its associated arm bay at another end
position, each expandable arm being pivotally mounted at the two
end positions with respect to its associated arm bay so that each
expandable arm is maintained substantially parallel to the
longitudinal axis of the body in both the retracted and expanded
positions and during its expansion and retraction between the
retracted and expanded positions.
[0015] By having links connecting each expandable arm to its
associated arm bay, the expandable arm can be maintained
substantially parallel to the longitudinal axis of the reamer tool
thereby providing an opening range which is greater than that
possible with expansion mechanisms comprising wedge elements or the
like.
[0016] In the case where the downhole tool comprises a reamer tool,
the advantage of maintaining the expandable arm parallel to the
longitudinal axis of the body is that the attack point for each
cutting blade is reliable, the attack point being the point at
which a leading cutting element engages with the material or
formation to be cut.
[0017] Naturally, an actuation mechanism is also provided for
activating the expansion mechanism, each expandable arm being
pivotally connected at another end position to the actuation
mechanism.
[0018] Advantageously, the expansion mechanism further comprises a
third elongate link pivotally connected to each expandable arm and
to the actuation mechanism.
[0019] In this way, the actuation mechanism directly moves the
expandable arm and the other elongate links serve to maintain the
substantial parallelism with the longitudinal axis. In a preferred
embodiment, the actuation mechanism comprises a piston.
[0020] The downhole tool may further comprise at least one return
member for deactivating each deployment mechanism. In one
embodiment, each return member comprises a spring biased against
the action of the actuation mechanism.
[0021] A shoulder block may be provided which is locatable in each
arm bay to limit the expansion of the expandable arm. By selecting
a suitably sized shoulder block, the expansion of the expandable
arm can be determined to provide a desired outer diameter for
engagement with a formation.
[0022] In a preferred embodiment, the second outer diameter may be
up to 1.3 times the first outer diameter. For example, if the outer
diameter of the downhole tool is 100 cm, the expandable arms may be
expanded to describe an outer diameter of up to 130 cm.
[0023] Preferably, the downhole tool comprises a reamer tool and
each expandable arm comprises a cutter arm.
[0024] In accordance with another aspect of the present invention,
there is provided an expandable cutter arm for a downhole tool, the
expandable cutter arm comprising at least a front cutting blade and
a back cutting blade, each cutting blade comprising a plurality of
cutting elements, one cutting element on each of the front cutting
blade and the back cutting blade providing an attack point for the
associated cutting blade.
[0025] Such an expandable cutter arm may further comprise a first
side and a second side located either side of a plane, each side
being spaced at respective predetermined distances from a plane so
that the attack point for the front blade and the attack point for
the back blade are equi-spaced from the plane.
[0026] By having the attack point for each cutter arm equi-spaced
from the plane, efficiency of the reamer tool is improved. In
addition, a more flexible reamer tool is provided in which a range
of opening sizes can be accommodated.
[0027] The predetermined distance for the first side may be
different to the predetermined distance for the second side.
[0028] In one embodiment, the cutting elements may comprise
polycrystalline diamond cutting elements.
[0029] In accordance with a further aspect of the present
invention, there is provided a reamer tool having at least one
expandable cutter arm as described above.
[0030] In accordance with another aspect of the present invention,
there is provided a reamer tool having a longitudinal axis, the
reamer tool comprising at least one expandable cutter arm having a
plurality of cutting elements arranged to form at least a front
cutting blade and a back cutting blade, one of the cutting elements
on the front cutting blade and one of the cutting elements on the
back cutting blade providing respective attack points for their
associated cutting blades, characterised in that the attack point
for the front cutting blade and the attack point for the back
cutting blade are equi-spaced from a plane extending through the
longitudinal axis.
[0031] The reamer tool preferably further comprises at least one
expansion mechanism for expanding an associated expandable cutter
arm between a retracted position and an expanded position, and an
actuation mechanism for activating each expansion mechanism.
[0032] In a preferred embodiment, each expansion mechanism
comprises at least two elongate links pivotally connected to the
associated expandable cutter arm at one end position and to its
associated arm bay at another end position, each expandable cutter
arm being pivotally mounted at the two end positions with respect
to its associated arm bas so that each expandable cutter arm is
maintained substantially parallel to the longitudinal axis in both
the retracted and expanded positions, and, during expansion and
retraction between the retracted and expanded positions.
[0033] The expansion mechanism advantageously further comprises a
third elongate link pivotally connected to each expandable cutter
arm and to the actuation mechanism, each expandable cutter arm
being pivotally connected at another end position to the actuation
mechanism.
[0034] The actuation mechanism preferably comprises a piston. The
reamer tool may further comprise at least one return member for
deactivating each expansion mechanism.
[0035] A shoulder block may be provided which is locatable in each
arm bay to limit the expansion of the expandable cutter arm. The
cutter arm may have an opening range up to 1.3 times the outer
diameter of the reamer tool, the shoulder block limiting the
opening in accordance with it size.
[0036] In accordance with another aspect of the present invention,
there is provided a control module for a downhole tool, the
downhole tool including a substantially hollow body having a
longitudinal axis, at least one arm bay formed around the periphery
of the substantially hollow body, at least one expandable arm
located in an associated arm bay and mounted for expansion between
a retracted position within the substantially hollow body and an
expanded position in which the expandable arm describes a second
outer diameter which is greater than the first outer diameter, at
least one expansion mechanism for expanding an associated
expandable arm between the retracted and expanded positions, and a
piston for operating each expandable arm, the control module
comprising:
[0037] an element mounted within the body which is moveable between
a first position and second position;
[0038] a motor controlling the movement of the element; and
[0039] a gearing mechanism associated with the motor for
transferring drive from the motor to the element;
[0040] characterised in that the control module further comprises a
chamber and a port, the chamber being associated with the piston
and the port having an open position and a closed position, the
open and closed position being determined by the second and first
positions respectively of the element;
[0041] and in that the port, in its open position, allows fluid to
flow into the chamber and to increase the pressure therein for
operation of the piston to expand each expandable arm.
[0042] In a preferred embodiment, the motor and gearing mechanism
are mounted between the element and the external wall of the body.
A power source is preferably located within the body of the reamer
tool. This has the advantage of protecting the control module, that
is, the motor, gearing mechanism and power source from the
environment in which the reamer tool operates.
[0043] In one embodiment, the power source comprises a battery. In
another embodiment, the power source comprises a turbine arranged
to generate power for the motor.
[0044] The control module may further comprise at least one
positional sensor for sensing the position of the element within
the body. In addition, at least one pressure sensor may also be
provided for sensing the pressure within the chamber.
[0045] In addition, at least one sensor may be provided for sensing
at least a change in pressure in fluid flowing through the downhole
tool, each sensor providing a control signal for the motor.
Moreover, at least one sensor may be provided for sensing a change
in rotational speed of the downhole tool, each sensor providing a
control signal for the motor.
[0046] Additionally, a communications system may be provided
through which control signals are provided for the motor. In one
embodiment, the communications system includes a wired link over
which control signals are transmitted.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] For a better understanding of the present invention,
reference will now be made, by way of example only, to the
accompanying drawings in which:
[0048] FIG. 1 illustrates a schematic sectioned view of a reamer
tool in accordance with the present invention, the reamer tool
being shown in a retracted position;
[0049] FIG. 2 is similar to FIG. 1 but illustrates the reamer tool
in an expanded position;
[0050] FIG. 3 illustrates cutters mounted on an arm of the reamer
tool shown in FIGS. 1 and 2;
[0051] FIG. 4 illustrates a sectioned view of a control system for
the reamer tool shown FIGS. 1 and 2 with the reamer tool in the
stowed position;
[0052] FIG. 5 is similar to FIG. 4 but illustrates the control
system with the reamer tool in the expanded position.
DESCRIPTION OF THE INVENTION
[0053] The present invention will be described with respect to
particular embodiments and with reference to certain drawings but
the invention is not limited thereto. The drawings described are
only schematic and are non-limiting. In the drawings, the size of
some of the elements may be exaggerated and not drawn on scale for
illustrative purposes.
[0054] It will be understood that the terms "vertical" and
"horizontal" are used herein refer to particular orientations of
the Figures and these terms are not limitations to the specific
embodiments described herein. In addition, the terms "top" and
"bottom" are used to refer to parts of a drill string that face
towards the surface, or top of the drill string, and away from the
surface, or bottom of the drill string, respectively.
[0055] The present invention relates to an improved reamer tool and
a control system for operating such a reamer tool or other downhole
tool. The reamer tool is described below with reference to FIGS. 1
to 3 and the control system is described with reference to FIGS. 4
and 5.
[0056] Although the present invention is described below with
respect to a reamer tool having cutter arms, it is equally
applicable to a downhole tool that may also be used for
stabilisation. In this case, the cutter arms are replaced by
stabilising pad arms which, when expanded, contact the walls of a
formation to stabilise the drill string of which the tool forms a
part. In addition, although the control system is described with
reference to use with a reamer tool, it is not limited to use with
a reamer tool and can be used with any other downhole tool.
[0057] Reamer tools, as well as other downhole tools, are operated,
that is, expanded and retracted by changes in the pressure of fluid
flowing through the associated drill string. The fluid flow is
controlled by a pump associated with the drill string. Changes in
fluid pressure are detected by sensors located at appropriate
positions in the drill string.
[0058] Referring initially to FIGS. 1 and 2, a longitudinal
sectioned view of reamer tool 100 is shown. The reamer tool 100
comprises a reamer body 105 having three cutter arms 110 mounted
within respective housings or arm bays 115 formed in the reamer
body 105. The three cutter arms 110 are equi-spaced around the
periphery of the reamer body 105 but only one such cutter arm is
shown in FIGS. 1 and 2.
[0059] Each cutter arm 110 comprises a cutting element or cutting
blade 120 which is pivotally mounted on each of three elongate
links 125, 130, 135 at respective pivot points 140, 145, 150 as
shown. Two of the elongate links 125, 130 are also pivotally
attached to the housing or arm bay 115 at respective pivot points
155, 160. The third elongate link 135 is also pivotally mounted, by
means of a pivot point 165, on a piston 170.
[0060] The piston 170 comprises an actuation mechanism and is
operated to move from a first position as shown in FIG. 1 to a
second position as shown in FIG. 2 to expand the cutter arms 110,
and more particularly, the cutting elements or cutting blades 120,
from a retracted position to an expanded position where the cutting
elements or cutting blades 120 extend outside the reamer body 105
and define an outer diameter which is up to 1.3 times that of the
normal outer diameter of the reamer body 105.
[0061] It will be appreciated that, in other embodiments of the
reamer tool 100 in accordance with the present invention, the outer
diameter defined by the three cutter arms 110 and their cutting
elements or cutting blades 120 may have other ratios compared to
the outer diameter of the reamer body 105 as required, and, is
therefore not limited to up to 1.3 times the outer diameter of the
reamer body 105. The outer diameter is limited by a shoulder block
175 and the size of the shoulder block 175 is chosen at the surface
before introduction of the drill string of which the reamer tool
100 forms a part into a wellbore in a formation in accordance with
the outer diameter of the reamer tool 100 required to from the
wellbore in the formation.
[0062] It will be appreciated that shoulder blocks of different
sizes can be provided with the reamer tool 100 and an appropriately
sized shoulder block is chosen to limit the expansion of the cutter
arms 110 to control the outer diameter defined by the expanded
cutter arms 110 and cutting elements or cutting blades 120 within
an opening range from the same outer diameter of the reamer body
105 to 1.3 times that outer diameter.
[0063] In the deployment of the cutter arms 110 from inside their
respective housings or arm bays 115 formed in the reamer body 105,
the cutting structure (not shown) of each cutter arm 110 always
remains parallel to a longitudinal axis 180 of the reamer body 105.
The pivot points 140, 145, 150, 155, 160, 165 formed on respective
ones of the links 125, 130, 135, as described above, effectively
provide pivoting axes about which rotation can occur to expand and
retract the cutter arms 110 and cutting elements or cutting blades
120 out of and into their respective housings or arm bays 115.
However, pivot points 140, 145 provided on respective links 125,
130 ensure that the cutter arms 110 remain parallel to the reamer
body 105 as they are expanded, used for cutting and retracted into
their respective housings or arm bays 115. Pivot point 150 provided
on elongate link 135 is used to expand and retract the associated
cutter arm 110 in accordance with the movement of the piston 170 or
other actuation mechanism as will be described in more detail
below.
[0064] By using an expansion mechanism which utilises elongate
links pivotally connected to both the cutter arm 110 and the
housing or arm bay 115 as well as to the piston 170 or other
actuation mechanism, the effective outer diameter of the cutter arm
110 and cutting element or cutting blade 120 can extend up to 1.3
times the outer diameter of the reamer body 105. In addition, the
amount of expansion can easily be limited by a suitable shoulder
block 175.
[0065] The force for expanding the cutter arms 110 is provided by
pressure applied to the piston 170, and, the force for retracting
the cutter arms is provided by a spring 185 (described below with
reference to FIGS. 4 and 5). The applied pressure is provided by
fluid flow through the reamer body 105 as will be described in more
detail below.
[0066] As shown in FIGS. 1 and 2, the reamer body 105 is
substantially tubular with a hollow central portion 190 which
defines a fluid flow path. The piston 170 is mounted within the
reamer body 105 and is operated by fluid flowing therethrough as
will described in more detail with reference to FIGS. 4 and 5
below.
[0067] In the embodiment of the reamer tool 100 described above, it
is essential to ensure that the cutting elements, for example,
polycrystalline diamond cutters known as PDC cutters, function
adequately during the expansion stages to make contact with the
formation in which the reamer tool is to be used. This is described
in more detail with respect to FIG. 3.
[0068] In FIG. 3, a portion 200 of a cutter arm 110 of the reamer
tool 100 shown in FIGS. 1 and 2 is shown in more detail. The
positioning of the cutting elements with respect to the cutter arm
110 is shown. The portion 200 shows a single cutter arm 110 (FIG.
1) having two cutting blades 205, 210, a front cutting blade 205
and a back cutting blade 210. [The terms "front" and "back" refer
to the order in which the cutting blades make contact with the
walls of a wellbore formed in a formation and is determined by the
direction of rotation of the drill string (not shown) of which the
reamer tool 100 (FIG. 1) forms a part.]
[0069] In the embodiment shown in FIG. 3, five cutting elements
215, 220, 225, 230, 235 are visible on front cutting blade 205, and
six cutting elements 240, 245, 250, 255, 260, 265 are visible on
back cutting blade 210. Cutting element 215 on front cutting blade
205 and cutting element 240 on back cutting blade 210 have
respective attack points 270, 275 which are equi-spaced from a
plane 280 that is coincident with the longitudinal axis 180 of the
reamer body 105 (FIG. 1). This means that the distance from side
285 of front cutting blade 205 to the plane 280 is shorter than the
distance from side 290 of back cutting blade 210 to plane 280.
[0070] In the embodiment shown in FIG. 3, the cutting elements 215,
220, 225, 230, 235, 240, 245, 250, 255, 260, 265 comprise PDC
elements as shown. Although eleven PDC elements are visible, the
number of PDC elements present on each blade 205, 210 is determined
in accordance with the dimensions of the PDC element and the
dimension of the reamer tool itself. However, it will be
appreciated that other types of cutting elements may also be used,
for example, impregnated cutting elements.
[0071] By having the attack points 270, 275 equi-spaced from the
plane 280, attack points 270, 275 will contact the formation for
any opening size in the opening range. If the attack points 270,
275 are not equi-distant from the plane 280, the cutter arms will
only have one possible opening size to ensure that both the front
and back cutting blades make contact with the formation.
[0072] The front and back blades 205, 210 as described above have
different numbers of cutting elements 215, 220, 225, 230, 235, 240,
245, 250, 255, 260, 265 which are not aligned with one another so
that the attack points 270, 275 of cutting elements 215, 240 are at
different heights with respect to the reamer body 105.
[0073] The effective outer diameter of the reamer tool 100, that
is, the opening size is determined by the positions of attack
points 270, 275.
[0074] Referring now to FIGS. 4 and 5, a schematic longitudinal
sectioned view of the reamer tool 100 is shown. Components that
have previously been described with reference to FIGS. 1 and 2 have
the same reference numerals.
[0075] The reamer tool 100 comprises the reamer body 105 having
cutter arms 110 mounted within respective housings or arm bays 115
formed in the reamer body 105 as described above. The links and the
pivot points that operate the cutter arms 110 as described above
are not shown for clarity. The spring 185 that is used to return
the expanded cutter arms to their retracted position is shown
schematically as a block.
[0076] As described above, the force for expanding the cutter arms
110 is provided by pressure applied to the piston 170 due to fluid
flow through the reamer tool 100, and, the force for retracting the
cutter arms is provided by the spring 185. During expansion of the
cutter arms, the pressure exerted on the piston 170 creates a force
which is greater than the force provided by the spring 185. Once
the pressure exerted on the piston 170 falls sufficiently so that
the force exerted becomes less than the force provided by the
spring 185, the spring 185 causes the cutter arms 110 to be
retracted into their respective housings or arm bays 115. This is
described in more detail below.
[0077] A control system 300 for deploying the cutter arms 110 is
provided within the reamer body 105 and comprises an electric motor
310, a gearing system 315 and a moveable sleeve 320, the electric
motor 310 and gearing system 315 being housed between the sleeve
320 and an external wall 325 of the reamer body 105. The electric
motor 310 rotates at a first predetermined speed and the gearing
system 315 reduces that first predetermined speed to a second lower
predetermined speed which is used for operating the moveable sleeve
320. In one embodiment, a ball screw (not shown) may be used to
transfer the rotational output from the gearing system 315 to a
linear movement which is used to move the sleeve 320 to open and
close port 385 as will be described in more detail below. However,
it will be appreciated that other arrangements may be used for
transferring rotary motion from the gearing system 315 to linear
motion of the moveable sleeve 320, for example, a pinion or worm
gear forming part of the gearing system 315 may engage with a rack
element provided on the moveable sleeve 320.
[0078] The electric motor 310 may be powered by a battery (not
shown) or from a turbine provided in the drill string (also not
shown), the turbine generating a current from the fluid flow
therethrough. Although a gearing system 315 is described, it will
be appreciated that drive from the motor may be converted into
linear movement by any suitable means for converting the output of
the motor into linear movement.
[0079] The housing or arm bay 115 for each cutter arm 110 is
defined by a wall 330 of the hollow central portion 190 and a
portion 335 of the external wall 325 of the reamer body 105. The
piston 170 is defined by a chamber 340 adjacent the cutter arm 110,
the chamber 340 being defined by the wall 330 of the central
portion 190, external wall 325 of the reamer body 105, sleeve 320,
first cylindrical portion 345, second cylindrical portion 350 and
end wall 355 as shown. End wall 355 also forms barrier between the
electric motor 310 and gearing system 315 of the control system
300.
[0080] Annular seals 360, 365 are provided between the first
cylindrical portion 345 and respective ones of wall 330 and sleeve
320. Additional annular seals 370, 375 are provided between sleeve
320 and second cylindrical portion 350 and with wall 380 of hollow
central portion 190. Seal 360 can be mounted on either the first
cylindrical portion 345 or the wall 330 as the first cylindrical
portion 345 does not move relative to the wall 330.
[0081] The first and second cylindrical portions 345, 350 define
the port 385 which is sealed by the moveable sleeve 320 when in a
first position, as shown in FIG. 4, so that fluid flows through the
hollow central portion 190 as indicated by arrow 390. When the
sleeve 320 is in a second position, as shown in FIG. 5, the port
385 is open and fluid can flow into chamber 340 as shown by arrow
395.
[0082] An additional seal 400 is also provided between the piston
170 and the external wall 325 of the reamer body 105 as shown to
prevent ingress of drilling fluid as the piston 170 moves from the
position shown in FIG. 4 to the position shown in FIG. 5.
[0083] Operation of the electric motor 310 effectively moves the
sleeve 320 in the same direction as arrow 390 to open the port 385
and in the opposite direction to close the port 385, drive from the
electric motor 310 being transmitted to the sleeve 320 via the
gearing system 315. A control signal for the electric motor 310 is
provided by way of an increased fluid flow rate through the hollow
central portion 190 and/or speed of rotation of the drill string
(not shown). At least one suitable sensor (not shown) is provided
to sense the change in pressure and/or rotational speed and to
provide a control signal for the electric motor 310, for example, a
pressure sensor for sensing changes in pressure and an
accelerometer for sensing the change in rotational speed. However,
other sensors may also be used for sensing the change in rotational
speed.
[0084] It will be appreciated that the electric motor 310 may be a
bi-directional motor that operates in two directions to effect
opening and closing of the port 385. As an alternative to the
electric motor 310, a solenoid may be used to effect opening and
closing of the port 385.
[0085] Naturally, the electric motor 310 and gearing system 315 are
sealed within a region 410 defined by the sleeve 320 and an
external wall 325 so that it is protected from the drilling
environment, that is, the mud, rock etc., that finds its way into
the hollow central region 190. In a preferred embodiment, the
region 410 is filled with oil to prevent the ingress debris from
the drilling environment.
[0086] Before the cutter arms 110 are expanded, they are housed in
their respective housings or arm bays 115 as described above. Fluid
flow is through the hollow central portion 190 as indicated by
arrow 390 (FIG. 4). When a control signal is sent to the electric
motor 310, by way of a change in pressure of the fluid flowing
through the hollow central portion 190 and/or a change in the
rotational speed of the drill string as described above, the
electric motor 310 operates the moveable sleeve 320 to move it in
the same direction as the fluid flow as indicated by arrow 390 to
open port 385 (FIG. 5).
[0087] When the port 385 is opened, fluid flows into the chamber
340 and pressure builds up therein. When the pressure in the
chamber 340 reaches a value where the force exerted by the piston
170 is greater than the force exerted by the spring 185, the piston
170 is pushed from the position shown in FIG. 4 towards the arm
bays 115 to expand the cutter arms 110 as shown in FIG. 5. Movement
of the piston 170 towards the arm bays 115 causes each cutter arm
110 to pivot about pivot point 150 on link 135, as well as pivot
points 140, 145 on links 125, 130, so that it is expanded from the
within its associated arm bay 115 as shown in FIGS. 1 and 4, to the
position as shown in FIGS. 2 and 5. Fluid built up in the chamber
340 flows out of nozzles 415 associated with the cutter arms 110
maintaining the position of the piston 170 as shown in FIGS. 2 and
5, and hence the expansion of the cutter arms 110, until the port
385 is closed by the sleeve 320 by the operation of the motor 310
and gearing mechanism 315.
[0088] On receipt of a further control signal, that is, another
change in pressure of the fluid flow and/or a change in rotational
speed of the drill string, the motor 310 is activated once again to
move the moveable sleeve 320 from the position shown in FIG. 5 back
to the position shown in FIG. 4, thereby closing the port 385 so
that no more fluid flows into the chamber 340 as indicated by arrow
395. Fluid flows out of nozzles 415 until the pressure in the
chamber 340 is reduced so that the force of the spring 185 causes
the cutter arms 110 to be returned to their associated housing or
arm bay 115 to be returned to the position shown in FIGS. 1 and 4.
In addition, the piston 170 is pushed back but the force exerted by
the spring 185 to its initial position as shown in FIGS. 1 and
4.
[0089] Alternatively, instead of operating the motor 310, the
cutter arms 110 may be retracted by turning the pump off that is
associated with the drill string so that fluid flow is switched off
through the drill string, and the pressure in the chamber 340 falls
as no further fluid flows through the port 385 and into the chamber
340. Once the pressure in the chamber 340 falls to a value where
the force exerted by the spring 185 exceeds that of provided by the
pressure in the chamber 340, the piston 170 is moved back to the
position shown in FIGS. 1 and 4 and the cutting arms 110 retracted
whilst still parallel to the longitudinal axis 180 due to their
pivoting about points 140, 145, 150; pivoting of the links 125, 130
about points 155, 160 in the respective housing or arm bay 115; and
pivoting about pivot point 165 due to movement of the piston 170 as
it moves from the position shown in FIG. 5 back to the position
shown in FIG. 4.
[0090] As mentioned above, the control system 300 includes a power
supply (not shown), but it may also include other electronic
equipment, for example, pressure sensors for sensing the pressure
in the chamber 340, accelerometers for measuring the speed of
movement of the sleeve 320 and piston 170 and the rotational speed
of the drill string, as well as the speed of the cutter arm 110
during its expansion and retraction phases. In addition, a
communication device (not shown) may be provided through which
control signals can be provided for the electric motor in the case
where the control signals are not supplied by changes in pressure
of the fluid flow or rotational speed of the drill string as
described above.
[0091] The power supply may be provided by one or more batteries or
via a wired link from the surface. Additionally, the wired link may
form part of the communication device through which the control
signals may be transmitted to the electric motor.
[0092] It will be appreciated that the cutter arm expansion
mechanism can be used with other tools, for example, downhole
stabilisers, and the cutter arms can be expanded using other
expansion mechanisms.
[0093] Although a specific embodiment of the present invention is
described, it will be appreciated that this embodiment is not
limiting and other embodiments may fall within the scope of the
invention as defined by the appended claims.
* * * * *