[0001] The present invention relates to a gauge hanger for deployment in the tubing of a
wellbore, and in particular a gauge hanger which can be deployed using a setting tool
and then later retrieved using a retrieval tool.
[0002] Gauge hangers are used in the oil and gas industry to support instruments such as
pressure and temperature measuring gauges inside tubing whilst the instruments gather
data. The gauge hanger and instruments are then recovered to surface at the end of
the monitoring period. Typically, the gauge hanger and measurement instrument are
installed and retrieved with a cable deployed setting tool.
[0003] Traditionally there have been two types of gauge hangers: those that work by wedging
themselves inside the tubing by various expanding gripper means, and those that are
seated in a special profile in the tubing string. When deployed, either of these means
may prevent further access to the wellbore via the tubing string.
[0004] It is known to use a magnetic field to attach a downhole instrument to tubing in
a wellbore. Gauge hangers that attach magnetically to the side of the tubing may allow
long-term deployment of instruments whilst retaining access to the wellbore for other
intervention tools. However, known magnetic attachment mechanisms tend to be complicated,
and may require the use of several permanent magnets or electromagnets in order to
switch between an activated and deactivated state. Furthermore, existing mechanisms
may require a cable to be permanently attached to the downhole instrument or may risk
the cable detaching before the gauge hanger is attached to the tubing.
[0005] It would therefore be desirable to provide a gauge hanger which can be reliably attached
to the tubing wall at the required depth and then released from its setting tool.
It would also be desirable to provide a gauge hanger which can be easily retrieved
at the end of the monitoring period.
[0006] According to one aspect of the present invention there is provided a gauge hanger
for deployment in a wellbore using a setting tool, the gauge hanger comprising:
a switchable magnet for attaching the gauge hanger to a wellbore wall; and
a coupling assembly for coupling the gauge hanger to the setting tool;
wherein the switchable magnet and the coupling assembly are arranged to be actuated
by a common actuator.
[0007] The present invention may provide the advantage that, by arranging the switchable
magnet and the coupling assembly to be actuated by a common actuator, a less complex
system requiring fewer parts may be provided. Furthermore, this arrangement may help
to ensure that the setting tool can only be disengaged from the gauge hanger once
the gauge hanger is attached to the wall.
[0008] The switchable magnet and the coupling assembly are preferably mechanically linked.
For example, the switchable magnet and the coupling assembly may be linked by a rotatable
member (such as a shaft), which may be rotatable by the common actuator. In this case,
the switchable magnet and the coupling assembly may both be actuated by rotation of
the rotatable member. This may facilitate actuation of the switchable magnet and the
coupling assembly by the common actuator.
[0009] The gauge hanger is preferably arranged to be lowered into the wellbore using the
setting tool. Once at the required depth, the gauge hanger is preferably arranged
to be attached to the wellbore wall and released from the setting tool. The setting
tool can then be lifted to surface.
[0010] The switchable magnet is preferably switchable between a deactivated state and an
activated state. In the activated state, the switchable magnet preferably produces
an external magnetic field sufficient to attach the gauge hanger to the wellbore wall.
In the deactivated state the switchable magnet preferably produces no external magnetic
field, or insufficient external magnetic field to attach the gauge hanger to the wellbore
wall.
[0011] The coupling assembly is preferably switchable between an engaged state and a disengaged
state. In the engaged state, the gauge hanger is preferably attached to the setting
tool, preferably in such a way that the setting tool can support the gauge hanger.
In the disengaged state, the setting tool can preferably be detached from the gauge
hanger.
[0012] Preferably, switching the switchable magnet to an activated state also switches the
coupling assembly to a disengaged state. This may allow the gauge hanger to be detached
from the setting tool as part of the same action as attaching the gauge hanger to
the wellbore wall. This may help to provide a less complex system requiring a single
actuator and/or fewer parts than might otherwise be required.
[0013] Preferably, during setting, the coupling assembly is not switched to the disengaged
state until the switchable magnet is switched to an activated state. This may help
to ensure that the setting tool is only detached from the gauge hanger once the gauge
hanger is attached to the wall.
[0014] The gauge hanger may be arranged to be retrieved from the wellbore using a retrieval
tool. The retrieval tool may be the same as the setting tool, or a separate retrieval
tool may be used. The retrieval tool may be lowered into the wellbore until it encounters
the gauge hanger. The gauge hanger may be arranged to be attached to the retrieval
tool and detached from the wellbore. The retrieval tool and gauge hanger may then
be lifted to surface.
[0015] Preferably, during retrieval, switching the coupling assembly to an engaged state
also switches the switchable magnet to a deactivated state. This may allow the gauge
hanger to be detached from the wellbore wall as part of the same action as attaching
the gauge hanger to the retrieval tool. This may help to provide a less complex system
requiring a single actuator and/or fewer parts than might otherwise be required.
[0016] Preferably the switchable magnet is not switched to a deactivated state until the
coupling assembly is switched to the engaged state. This may help to ensure that the
gauge hanger is only detached from the wellbore wall once the gauge hanger has been
attached to the retrieval tool.
[0017] The switchable magnet preferably comprises one or more permanent magnets in a configuration
that allows an external magnetic field to be turned on or off. For example, the switchable
magnet may comprise a rotatable core, and the rotatable core may comprise one or more
permanent magnets. The rotatable core may be provided in a base comprising at least
one block of high magnetic permeability material and a block of low magnetic permeability
material. Rotation of the rotatable core (relative to the base) may switch the switchable
magnet between an activated state and a deactivated state. This may allow an external
magnetic field to be easily switched on and off without requiring an electromagnet.
[0018] Preferably the coupling assembly comprises a rotatable element, and rotation of the
rotatable element switches the coupling assembly between an engaged state and a disengaged
state. This may help to provide a simple mechanism for attaching and detaching the
setting tool to the gauge hanger.
[0019] Preferably the rotatable element is rotated synchronously with a rotatable core in
the switchable magnet. Thus, the gauge hanger may comprise means, such as a rotatable
shaft, for transferring rotation between the rotatable element and the rotatable core.
This may allow a single actuator such as a motor to be used to attach the gauge hanger
to the wellbore wall and to decouple the setting tool from the gauge hanger.
[0020] In one embodiment, the coupling assembly comprises an engagement member (for example,
one or more dogs) for engagement with the setting tool. In this case, the rotatable
element may comprise a cam which is arranged to displace the engagement member. For
example, the cam may be arranged to displace the engagement member radially as the
cam rotates. Displacement of the engagement member may be, for example, through an
aperture such as a slot in the coupling assembly. The coupling assembly may also comprise
means for causing the engagement member to follow the cam. For example, the coupling
assembly may comprise a slot and pin arrangement which causes the engagement member
to follow the profile of the cam. However, if desired, any other means for causing
the engagement member to follow the cam, such as a spring, may be used instead or
as well.
[0021] The engagement member may be arranged, for example, to engage with an aperture such
as a slot in the setting tool. This may provide a convenient mechanism for engaging
and/or disengaging the gauge hanger with and/or from the setting tool.
[0022] In one embodiment, the coupling assembly comprises two engagement members, which
may be arranged to move in opposite directions. In this case, the cam may comprise
two lobes and each lobe may act on one of the engagement members. Each of the engagement
members may be arranged to move radially outwards into a corresponding aperture in
the setting tool. This may help to provide a secure mechanism for holding the setting
tool and the gauge hanger together. Alternatively, if desired, any other appropriate
number of engagement members and/or lobes, such as three, four or more, may be provided,
and the engagement members may be arranged to move in any appropriate direction. Furthermore,
rather than a cam, any other appropriate means for urging an engagement member outwards
may be provided.
[0023] The coupling assembly may comprise means for limiting rotation of the rotatable element.
For example, where the rotatable element is a cam, the coupling assembly may comprise
a lobe shaped cavity for limiting rotation of the cam. This may help to ensure that
the cam is not over-rotated. This in turn may help to ensure that the switchable magnet
remains in the desired state (e.g., fully activated or fully deactivated) and/or that
the coupling assembly remains in the desired state (e.g., fully engaged or fully disengaged).
[0024] The gauge hanger may further comprise a secondary retention mechanism for holding
the setting tool and the gauge hanger together when the coupling assembly is in a
disengaged state. The secondary retention mechanism may comprise, for example, a snap
ring on the gauge hanger which is arranged to engage with a groove on the setting
tool, or vice versa, or alternatively any other type of releasable retention means.
This may help to ensure that the setting tool and gauge hanger are held together as
the coupling assembly is engaged/disengaged. It may also help to ensure that the two
engagement members are accurately aligned with the corresponding apertures of the
setting tool.
[0025] If desired, a single switchable magnet could be used to attach the gauge hanger to
the wellbore wall. However, in a preferred embodiment, the gauge hanger comprises
a plurality of switchable magnets for attaching the gauge hanger to the wellbore wall.
For example, the gauge hanger may comprise two switchable magnets, one at or towards
the top of the gauge hanger and one at or towards the bottom of the gauge hanger.
Alternatively, three or more switchable magnets could be used, in which case one or
more switchable magnets may be provided at one or more intermediate locations along
the length of the gauge hanger. Use of a plurality of switchable magnets may help
to ensure that the gauge hanger remains attached to the wellbore wall. For example,
where the gauge hanger is deployed in production tubing, this may help to prevent
the gauge hanger from being dislodged by passing liquid or gas flow. Furthermore,
this may help to prevent the gauge hanger from being dislodged by other tools passing
the gauge hanger in either direction. Furthermore it may help the gauge hanger mate
with a variation of internal curvature of the wellbore using different curvatures
of the switchable magnet housings.
[0026] The gauge hanger is preferably used to support one or more instruments such as a
measuring gauge. In one embodiment, a switchable magnet is provided on either side
of the instrument. In this case, the instrument may also be used to transfer rotation
between the switchable magnets. This may help to provide a simple and convenient way
of activating and/or deactivating both switchable magnets. However, if desired, another
mechanism such as a rotatable shaft could be used to transfer rotation between the
switchable magnets.
[0027] The gauge hanger may further comprise means for removably connecting the coupling
assembly to an actuator in the setting tool. The means for removably connecting the
coupling assembly to the actuator may be arranged to transfer rotation between the
actuator and the gauge hanger when engaged. For example, the gauge hanger may comprise
a socket and the setting tool may comprise a shaft arranged to seat inside the socket,
or vice versa. This may allow rotation to be transferred between an actuator, such
as a motor, in the setting tool and the gauge hanger, while allowing the setting tool
to be detached from the gauge hanger.
[0028] The socket and shaft are preferably arranged to transfer rotation between the two.
For example, the shaft may be a hexagonal shaft, in which case the socket may be a
hexagonal socket. Alternatively, any appropriate shape of socket and/or shaft, such
as square, rectangular, triangular, star-shaped, octagonal, or any other multi-sided
polygonal shape may be used instead. Furthermore, any other appropriate arrangement
which allows rotation to be transferred when engaged (such as holes and pins) may
be used instead of a socket and shaft.
[0029] According to another aspect of the invention, there is provided a deployment assembly
comprising a setting tool and a gauge hanger in any of the forms described above.
[0030] According to another aspect of the invention, there is provided a deployment assembly
comprising:
a gauge hanger, the gauge hanger comprising a switchable magnet for attaching the
gauge hanger to a wellbore wall; and
a setting tool for deploying the gauge hanger in a wellbore,
wherein the deployment assembly comprises a coupling assembly for coupling the gauge
hanger to the setting tool, and
the switchable magnet and the coupling assembly are arranged to be actuated by a common
actuator.
[0031] In one embodiment, the coupling assembly is provided in the gauge hanger. However,
in another embodiment, the coupling assembly is provided in the setting tool rather
than in the gauge hanger. In this case, the coupling assembly may comprise an engagement
member for engagement with the gauge hanger and the gauge hanger may comprise an aperture
for receiving the engagement member. The coupling assembly may otherwise be in any
of the forms described above.
[0032] In any of the above arrangements, the setting tool may comprise an actuator arranged
to actuate the coupling assembly and the switchable magnet. The actuator may be for
example a motor arranged to supply torque to the coupling assembly and the switchable
magnet.
[0033] The setting tool (or gauge hanger) may comprise a collar arranged to slide over the
coupling assembly. The collar may comprise one or more of:
an internal taper;
a V-shaped slot arranged to ride over a locator pin on the coupling assembly;
an internal groove arranged to receive a snap ring on the coupling assembly; and
one or more slots arranged to receive an engagement member.
[0034] The setting tool may be arranged to deploy the gauge hanger in the wellbore. Furthermore,
the setting tool may be arranged to retrieve the gauge hanger from the wellbore.
[0035] The setting tool may comprise a guide arranged to locate the setting tool in the
wellbore relative to the gauge hanger. The guide may be for example in the form of
an elliptical hoop structure arranged at an angle to the vertical axis. The guide
may be arranged to ride over the gauge hanger and to rotate the setting tool relative
to the gauge hanger. This may help to ensure that the setting tool is correctly aligned
with the gauge hanger when it is being used for retrieval.
[0036] Alternatively, a separate retrieval tool may be used to retrieve the gauge hanger,
in which case the guide may be provided on the retrieval tool.
[0037] Corresponding methods may also be provided. Thus, according to another aspect of
the invention there is provided a method of deploying a gauge hanger in a wellbore,
the method comprising:
coupling the gauge hanger to a setting tool;
lowering the gauge hanger and setting tool in the wellbore;
attaching the gauge hanger to a wellbore wall by activating a switchable magnet; and
decoupling the setting tool from the gauge hanger,
wherein activating the switchable magnet and decoupling the setting tool are actuated
by a common actuator.
[0038] The actuator may be for example a motor arranged to rotate a rotatable element in
the gauge hanger (or setting tool) and a rotatable core in the switchable magnet.
Rotation of the rotatable element may cause the setting tool to decouple from the
gauge hanger. The rotatable element may be, for example, a cam arranged to act on
an engagement member.
[0039] Preferably the setting tool is not decoupled from the gauge hanger until the switchable
magnet is activated.
[0040] According to a further aspect of the invention there is provided a method of retrieving
a gauge hanger from a wellbore, the method comprising:
lowering a retrieval tool into the wellbore;
coupling the retrieval tool to the gauge hanger; and
deactivating a switchable magnet attaching the gauge hanger to a wellbore wall,
wherein coupling the retrieval tool and deactivating the switchable magnet are actuated
by a common actuator.
[0041] Preferably the switchable magnet is not deactivated until the retrieval tool is coupled
to the gauge hanger.
[0042] Features of one aspect of the invention may be provided with any other aspect. Apparatus
features may be provided with method aspects and vice versa.
[0043] Preferred embodiments of the present invention will now be described, purely by way
of example, with reference to the accompanying drawings, in which:
Figure 1 shows an overview of a wellbore system;
Figures 2(A) and 2(B) illustrate the principles of a switchable magnet;
Figure 3 shows parts of a deployment assembly in an embodiment of the invention;
Figure 4 shows parts of an upper magnet assembly and a coupling assembly;
Figure 5 is a cross-section through the upper magnet assembly and the coupling assembly;
Figure 6 shows parts of a lower magnet assembly;
Figure 7 is a cross-section through the lower magnet assembly;
Figure 8 is an exploded view of a coupling assembly in an embodiment of the invention;
Figure 9 is a cross-section through the coupling assembly;
Figure 10 shows a barrel of the coupling assembly;
Figure 11 shows a dog in the coupling assembly;
Figure 12 shows a collar of a setting tool; and
Figures 13(A) to 13(C) illustrate operation of the coupling assembly.
Overview
[0044] Figure 1 shows an overview of a wellbore system in one embodiment. Referring to Figure
1, the system comprises wellbore 2, casing 4, well head structure 6 and tubing 8.
The tubing 8 may be the conduit through which oil and gas are brought from the producing
formations to the surface. The tubing 8 is typically made from a metallic material
such as mild steel. An instrument 10 such as a pressure and temperature measuring
gauge is located inside the tubing 8 in order to gather data. The instrument 10 may
store the data in memory for later retrieval and/or transmit data to the surface,
for example, using acoustic telemetry or other means of communication. The instrument
10 is supported by a gauge hanger 12 which attaches to the wall of the tubing 8. The
gauge hanger 12 is set in place using a setting tool 14. The setting tool 14 is lowered
and raised using a deployment wire connected to a surface hoist (not shown). In this
example, the tubing 8 is production tubing, although the principles described herein
may be used with any type of tubing, such as drilling tubing or production tubing,
which may be permanently or temporarily deployed in the wellbore.
[0045] Traditionally there have been two types of gauge hangers: those that work by wedging
themselves inside the tubing by various expanding gripper means; and those that are
seated in a special profile in the tubing string. When deployed, either of these may
prevent further access to the wellbore via the tubing string.
[0046] For example, access may be required by other wireline conveyed tools, coiled tubing
conveying tools or small diameter 'spaghetti' strings of tubing. If the duration of
deployment of a gauge hanger assembly is long, this can lead to a conflict in operational
requirements, often requiring the instruments and hangers to be removed from the wellbore
prematurely.
[0047] In embodiments of the invention, a gauge hanger is provided that attaches magnetically
to the side of the tubing, allowing other tools to be run past it. A setting tool
is used to deploy the gauge hanger at the required depth. This can provide a means
of long-term deployment of instruments whilst retaining access to the wellbore for
other intervention tools.
[0048] The magnetic force required to hold the gauge hanger against the wall should only
be generated at the desired setting depth to prevent the device from attaching to
the nearest metallic item it encountered when being run in hole. Furthermore, the
magnetic force holding the gauge hanger against the wall should be able to be removed
at the set depth during retrieval. In embodiments of the invention, a switchable magnet
is used to attach the gauge hanger to the tubing wall. A switchable magnet is a device
that uses one or more permanent magnets in a configuration that allows the external
field to be turned on or off.
[0049] Figures 2(A) and 2(B) illustrate the principles of a switchable magnet in one exemplary
embodiment. In Figures 2(A) and 2(B), cross-sections through an exemplary switchable
magnet are shown. The switchable magnet comprises base 16 and switching core 18. The
base 16 comprises two blocks 20 of ferromagnetic material, such as iron, with a block
22 of non-ferrous material, such as brass or aluminium, between the two. A cylindrical
cavity runs through the centre of the base 16, intersecting the two blocks 20 of ferromagnetic
material and the block 22 of non-ferrous material. The switching core 18 is a cylindrical
permanent magnet which is located inside the cavity. The poles of the magnet are on
diametrically opposite sides of the switching core. The switching core 18 can be rotated
inside the base 16 between an "off" position and an "on" position.
[0050] When the switching core 18 is in the "off" position, as shown in Figure 2(A), the
poles of the magnet are orientated towards the block 22 of non-ferrous material.
[0051] In this position, the blocks 20 of ferrous material act as keepers, allowing the
magnetic flux to bridge the poles. Thus, in the "off" position, little or no external
magnetic field is created. However, when the switching core 18 is in the "on" position,
as shown in Figure 2(B), the blocks 20 of ferrous material act as an extension of
the magnet. Thus, in the "on" position, an external magnetic field is created, with
the magnetic flux passing through the blocks 20. The external magnetic field can be
used to attach the device to a metallic object such as a tubing wall.
Deployment assembly
[0052] In one embodiment, a gauge hanger and a setting tool form a deployment assembly for
deploying the gauge hanger in a wellbore. The deployment assembly is preferably provided
with the following functional features:
- The magnetic force required to hold the gauge hanger against the wall is only generated
at the desired setting depth.
- The magnetic force holding the gauge hanger against the wall is removable at the set
depth during retrieval.
- The setting tool suspended on a slickline has the capability of holding the gauge
hanger whilst being run in hole, activating the magnet at the set depth, and releasing
from the gauge hanger once it is set.
- The magnet is engaged before the setting tool releases the gauge hanger.
- A retrieval tool, preferably one and the same tool as the setting tool, when run in
hole is able to "find" and latch onto the gauge hanger, to release the magnetic force,
and to lift the gauge hanger to surface.
- In the set position, the gauge hanger is streamlined so that tools passing by do not
hook-up and pull the gauge hanger off the tubing wall. Therefore, both the top and
bottom of the gauge hanger and instrument assembly are preferably fixed to the tubing
wall in a streamlined manner.
- The gauge hanger has a low profile to allow other tools to pass by it in as small
a tubing size as possible.
- The magnetic force between the gauge hanger and tubing wall is sufficient to resist
being dislodged by high flow rates of liquid or gas, and to resist pushing or pulling
forces applied by a tool passing by it.
[0053] Figure 3 shows parts of a deployment assembly in an embodiment of the invention.
Referring to Figure 3, the deployment assembly comprises a gauge hanger 12 and a setting
tool 14. The setting tool 14 is used to set the gauge hanger 12 at the appropriate
location in the wellbore tubing. The setting tool 14 is attached to a deployment wire
15 connected to a surface hoist (not shown).
[0054] The setting tool 14 comprises a motor 24, a battery 25, a control unit 26 and a communications
module 27. The motor 24 is powered by the battery 25 and controlled by the control
unit 26. The control unit 26 comprises a processor and associated memory programmed
with the appropriate software to control operation of the motor 24. The communications
module 27 can receive and transmit data and commands for use by the control unit 26.
The communications module 27 communicates with equipment at the surface, for example,
through the wire 15 or using any other appropriate means of transmission, such as
a separate communications wire, radio frequency transmission or acoustic transmission.
[0055] The motor 24 is connected to a drive shaft 28 which is used to transfer torque to
the gauge hanger 12. The setting tool 14 includes a collar 29 which fits over a coupling
assembly in the gauge hanger 12.
[0056] The gauge hanger 12 comprises a coupling assembly 30, an upper magnet assembly 32
and a lower magnet assembly 34. The coupling assembly 30 is used to removably attach
the gauge hanger 12 to the setting tool 14. The upper magnet assembly 32 and the lower
magnet assembly 34 are used to attach the gauge hanger 12 to the tubing wall. The
upper and lower magnet assemblies 32, 34 are connected by means of two torsion bars
36. The torsion bars 36 are used to hold the upper magnet assembly 32 and the lower
magnet assembly 34 together and prevent rotation between the two. One or more instruments
10 such as a measuring gauge is located between the upper magnet assembly 32 and the
lower magnet assembly 34.
[0057] Each of the magnet assemblies 32, 34 comprises a switchable magnet with a switching
core. The switchable magnets may be, for example, in the form described above with
reference to Figures 2(A) and 2(B). Thus, the magnetic forces holding the gauge hanger
12 against the wall are switchable, allowing the device to be set at the required
depth and subsequently removed.
[0058] In the arrangement of Figure 3, both the upper magnet assembly 32 and the lower magnet
assembly 34 are used to attach the gauge hanger 12 to the tubing wall. This helps
to ensure secure attachment using a streamlined device. Furthermore, by attaching
both the top and the bottom of the gauge hanger, other tools passing in either direction
are less likely to dislodge the gauge hanger from the tubing wall. The magnetic forces
between the gauge hanger and tubing wall are designed to be sufficient to resist the
gauge hanger being dislodged by high flow rates of liquid or gas as well as to resist
pushing or pulling forces applied by a tool passing by it.
[0059] The motor 24 in the setting tool 14 is used to rotate the switching core in the upper
magnet assembly 32 between an "off" position and an "on" position via the drive shaft
28. The instrument 10 is also attached to the switching core in the upper magnet assembly
32. This allows rotation to be transferred through the instrument 10 to the lower
magnet assembly 34. Thus, the upper magnet assembly 32 and the lower magnet assembly
34 can be switched simultaneously between the "off" position and the "on" position.
The torsion bars 36 hold the upper magnet assembly 32 and the lower magnet assembly
36 in place relative to each other and ensure that the magnets are always aligned.
[0060] The coupling assembly 30 is designed such that activating the magnetic fields in
the upper and lower magnet assemblies 32, 34 also releases the gauge hanger 12 from
the setting tool 14, as will be explained below. This allows the setting tool 12 to
be removed once the gauge hanger 14 has been set at the required depth.
[0061] The coupling assembly 30 is also designed to attach to a retrieval tool, which may
be the same as the setting tool. Attaching the coupling assembly to the retrieval
tool also deactivates the magnetic fields in the upper and lower magnet assemblies
32, 34. This allows the gauge hanger to be released and lifted to the surface when
it is no longer required.
[0062] Figure 4 shows parts of the upper magnet assembly and the coupling assembly in more
detail. Referring to Figure 4, the upper magnet assembly 32 comprises magnetic mount
42, base 44, switching core 46 and upper instrument mount 48. In the assembled state,
the base 44 is located inside the magnetic mount 42, and the switching core 46 is
located inside the base 44. The base 44 and the switching core 46 together form a
switchable magnet. For example, the base 44 and the switching core 46 may be substantially
in the form described above with reference to Figures 2(A) and 2(B), although other
types of switchable magnet may be used instead. The magnetic mount 42 is used to hold
the base 44 in place. The outside surface of the base 44 is slightly curved, so as
to substantially conform to the inside surface of the tubing with which the gauge
hanger is to be used.
[0063] In the arrangement of Figure 4, the coupling assembly 30 comprises barrel 38 and
rotator shaft 40. The coupling assembly 30 is used to attach the gauge hanger to the
setting tool, and to rotate the rotator shaft 40. The switching core 46 is in the
form of a hollow cylinder with a cavity 47 extending longitudinally through its centre.
The rotator shaft 40 extends into the cavity 47 and is used to rotate the switching
core 46 inside the base 44. The magnetic mount 42 includes a hole 43 which engages
with a collar 45 on the barrel 38. The magnetic mount 42 is attached to the barrel,
so that the barrel 38 remains stationary with respect to the magnetic mount 42 and
the base 44. The magnetic mount 42 also includes holes 49 which are used to attach
the torsion bars 36 (see Figure 3).
[0064] In Figure 4, the rotator shaft 40 extends the entire way through the switching core
46, through a hole 41 in the magnetic mount 42, and into the instrument mount 48.
There is a slight clearance between the rotator shaft 40 and the hole 41, so that
the rotator shaft 40 can rotate inside the hole 41. The instrument mount 48 is fixed
to the rotator shaft 40, for example using a worm screw. Thus, the rotator shaft 40
can be used to rotate both the switching core 46 and the instrument mount 48. The
instrument mount 48 is used to connect an instrument and to transfer rotation of the
rotator shaft 40 though the instrument 10 to the lower magnet assembly 34.
[0065] Figure 5 is a cross-section through the upper magnet assembly and the coupling assembly
in the assembled state. Referring to Figure 5, the rotator shaft 40 extends from the
coupling assembly 30, through the switching core 46 to the instrument mount 48. The
rotator shaft is connected to the switching core and instrument mount, so that rotation
of the rotation shaft causes the switching core and the instrument mount to rotate.
The instrument mount 48 is arranged to connect to an instrument, for example, using
a threaded connection.
[0066] Figure 6 shows parts of the lower magnet assembly in more detail. Referring to Figure
6, the lower magnet assembly 34 comprises magnetic mount 50, base 52, switching core
54 and lower instrument mount 56. The magnetic mount 50 is used to hold the base 52
in place. The base 52 and the switching core 54 together form a switchable magnet.
The magnetic mount 50, base 52 and switching core 54 may be substantially the same
as the corresponding components in the upper magnet assembly 32, although it would
also be possible for them to have different sizes, materials and/or constructions.
[0067] The lower instrument mount 56 is designed to be mounted to the bottom of the instrument
10. Thus, rotation of the instrument 10 causes the lower instrument mount 56 to rotate.
The lower instrument mount 56 includes a rotator shaft 58. The rotator shaft 58 extends
into a cavity in the switching core 54 and is used to rotate the switching core 54
inside the base 52. The magnetic mount 50 includes a hole 53 which accommodates a
collar 55 on the lower instrument mount 56. There is a slight clearance between the
hole 53 and the collar 55, so that the collar 55 can rotate inside the hole 53. The
magnetic mount 50 also includes holes 57 which are used to attach the torsion bars
36. This allows the magnetic mount 50 and base 52 to be held in place (relative to
the upper magnet assembly) while the switching core 54 rotates.
[0068] The rotator shaft 58 extends the entire way through the switching core 54 and through
a hole 59 in the magnetic mount 50. There is a slight clearance between the rotator
shaft 58 and the hole 59, so that the rotator shaft 58 can rotate inside the hole
59. A nut 60 is screwed to the bottom of the rotator shaft 58, with a washer 61 provided
between the nut 60 and the bottom of the magnetic mount 50. The nut and washer allow
the shaft 58 and switching core to rotate, while holding the assembly together.
[0069] Figure 7 is a cross-section through the lower magnet assembly in the assembled state.
Referring to Figure 7, The lower instrument mount 56 is arranged to connect to an
instrument, for example, using a threaded connection. Rotation of the instrument transfers
rotation to the rotator shaft 58. The rotator shaft 58 extends through the switching
core 54 and through the hole 59 to the nut 60. The switching core 54 is connected
to the rotator shaft 58, so that rotation of the rotator shaft causes the switching
core to rotate.
[0070] Figure 8 is an exploded view of a coupling assembly in an embodiment of the invention.
Referring to Figure 8, the coupling assembly 30 comprises setting nut 62, washer 64,
rotator 66, dogs 68, barrel 38, snap ring 70, locator pins 72, and rotator shaft 40.
The snap ring 70 fits into a circumferential groove 71 on the outside of the barrel
38. The locator pins 72 fit into holes 73 on the outside of the barrel 38.
[0071] The setting nut 62 comprises a head 74 and a shank 75. The head 74 includes a socket
76 which is arranged to engage with the drive shaft 28 in the setting tool. In this
example, the socket 76 is a hexagonal cavity and the drive shaft 28 is a hexagonal
shaft, although it will be appreciated that other shapes may be used instead. Furthermore,
if desired, the socket could be in the setting tool and the shaft on the gauge hanger.
[0072] The shank 75 passes through a hole in the centre of the washer 64, and into a hole
78 in the rotator 66. The shank 75 is attached (firmly screwed in) to the rotator
66, so that rotation of the setting nut 62 causes rotation of the rotator 66. The
washer 64 is attached to the rotator 66 by two spring pins (not shown on Fig 8) and
rotates together with the rotator 66 and the setting nut 62.
[0073] The rotator 66 comprises a head 80 and a shank 81. The shank 81 extends into a hole
82 which runs through the centre of the barrel 38. There is a slight clearance between
the shank 81 and the hole 82, so that the shank 81 can rotate inside the hole 82.
The shank 81 is connected to the rotator shaft 40, so that rotation of the rotator
66 causes rotation of the rotator shaft 40.
[0074] The head 80 of the rotator 66 is in the form of a cam. The cam has two lobes orientated
at 180° to each other. The lobes of the cam 80 engage with the dogs 68. The rotator
66 is rotatable between a position in which the lobes are at 90° to the dogs 68 and
a position in which the lobes face the dogs. Rotation of the lobes towards the dogs
68 causes the dogs to be pushed radially outwards. The dogs 68 include holes 83. The
holes 83 receive pins (not shown) which fit into slots 84 in the washer 64. The slots
84 and pins are used to assist with the inward and outward radial movement of the
dogs 68, as will be explained below. The dogs 68 are arranged to engage with slots
in the setting tool 14.
[0075] Figure 9 is a cross-section through the coupling assembly 30 in the assembled state.
In the view shown in Figure 9, the lobes of the cam 80 are orientated perpendicular
to the plane of the paper. Referring to Figure 9, the setting nut 62 is connected
to the rotator 66, and the rotator 66 is connected to the rotator shaft 40. The washer
64 is also connected to the rotator 66. The snap ring 70 is located in the groove
71 on the outside of the barrel 38. The locator pins 72 are in the holes 73 on the
outside of the barrel 38. Rotation of the setting nut 62 causes rotation of the rotator
66, washer 64 and rotator shaft 40 relative to the barrel 38.
[0076] Figure 10 shows the barrel 38 of the coupling assembly 30 in more detail. Referring
to Figures 9 and 10, the barrel 38 includes two protrusions 86 which extend axially
in the direction of the setting nut 62. Each of the protrusions 86 has a straight
edge on the inside of the barrel. The two edges face each other and run parallel to
each other. Thus, the two edges define a slot 87 which runs radially through the barrel
38. The radial slot 87 accommodates the dogs 68.
[0077] Also visible in Figure 10 is a lobe-shaped cavity 88 in the barrel 38 immediately
inwards of the radial slot 87. The cam 80 on the rotator 66 is located partially in
the slot 87 and partially in the cavity 88. The lobe-shaped cavity 88 is used to limit
rotation of the cam 80 on the rotator 66.
[0078] Figure 11 shows one of the dogs in more detail. Referring to Figure 11, the inside
edge of the dog 68 engages with a lobe of the cam 80. The dog 68 acts as a cam follower,
that is, it follows the profile of the cam lobe, moving inwards and outwards as the
cam rotates. The dog 68 has flat sides 90 which allows it to slide radially inside
the slot 87 in the barrel 38. This prevents the dog from skewing. The inside edge
of the dog matches the shape of the cam 80, so that the dog 68 can be completely stowed
when the lobe of the cam is at 90° to the dog. When fully expanded, the tip of the
lobe "locks" into a trough 91 on the inside of the dog to prevent the cam from slipping
rotationally.
[0079] In the arrangement described above, the upper switching core 46 is fastened (for
example, glued or pinned) to the rotator shaft 40 with the poles of the core orientated
specifically relative to the rotator shaft 40 such that when the lobes of the cam
80 (and therefore rotator shaft) are rotated fully to their stop point where the engagement
members (dogs 68) are retracted, the magnet is fully energised. This may require the
rotator shaft to firstly be firmly fixed to the rotator before fixing the core to
the rotator shaft or some other means of achieving the correct alignment.
[0080] The lower rotator shaft 58 and switching core 54 can be fixed together in any orientation
but the lower instrument mount 56 should be fixed to the instrument 10 such that the
lower core 54 and the upper core 46 are exactly aligned so that they engage and disengage
magnetically simultaneously. This may require shimming of the lower instrument mount
to the instrument or some other means of achieving accurate rotational makeup of the
two.
[0081] Referring back to Figure 3, it can be seen that the collar 29 of the setting tool
14 fits over the coupling assembly 30 in the gauge hanger. The collar 29 includes
slots into which the dogs 68 can expand. This allows the setting tool 14 to hold the
gauge hanger 12 as it is being deployed.
[0082] Figure 12 shows the collar 29 of the setting tool in one embodiment. In this embodiment,
the collar is a separate component which attaches to the bottom of the setting tool,
although it would also be possible for the collar to be an integral part of the setting
tool. Referring to Figure 12, the collar 29 is in the form of a hollow cylinder. Recesses
89 are provided on the outside of the collar which allow it to attach to the bottom
of the setting tool. The inside diameter of the collar 29 is slightly larger than
the outside diameter of the coupling assembly 30 in the gauge hanger. The collar 29
also has an internal taper to help it ride over the coupling assembly. In addition,
the collar 29 has two V-shaped slots 94 on its sides. The V-shaped slots 94 open towards
the coupling assembly 30. The slots 94 engage with the locator pins 72 on the coupling
assembly to assist with location of the collar on the coupling assembly.
[0083] The collar 29 includes two opposing slots 92. Each slot 92 runs partially around
the collar in a circumferential direction and forms an aperture through the collar
29 in a radial direction. The dimensions of the slots 92 are slightly larger than
those of the dogs 68. The slots are sized and located such that the dogs 68 can expand
into them.
[0084] The collar 29 also includes two opposing grooves 93 on its inside surface. The grooves
93 are arranged to engage with the snap ring 70 on the coupling assembly 30.
[0085] In this embodiment, a guide 95 is shown attached to the collar 29. The guide 95 has
an outside diameter which corresponds to the diameter of the tubing in which the gauge
hanger is to be deployed. The guide 95 helps to ensure that the setting tool is correctly
orientated in the tubing. The guide 95 is attached to the collar 29 using a bolt 96.
The guide 95 can be removed from the collar 29 and replaced with one of a different
size. This can allow the setting tool to be used with tubulars of different diameters.
Alternatively, when the gauge hanger is being set, it may be possible to dispense
with the guide 95.
Deployment
[0086] When an instrument is to be deployed in the tubing of a wellbore, the gauge hanger
and instrument are first assembled at the surface. This is achieved by connecting
the top of the instrument 10 to the instrument mount 48 in the upper magnet assembly
32, connecting the bottom of the instrument 10 to the instrument mount 56 in the lower
magnet assembly 34, and then connecting the torsion bars 36 between the upper and
lower magnet assemblies 32, 34. If two or more instruments are to be deployed, then
these may be connected in series between the upper and lower magnet assemblies 32,
34.
[0087] Prior to fitting the gauge hanger to the setting tool, the dogs 68 are withdrawn
(if this is not already the case). This is achieved by rotating the rotator 66 such
that the lobes of the cam 80 face away from the dogs 68. The rotator 66 may be rotated,
for example, using a wrench inserted into the hexagonal cavity 76 in the setting nut
62, or by rotating the instrument 10, or in any other way. This also ensures that
the switchable magnets are deactivated.
[0088] The setting tool 14 is then attached to the gauge hanger 12. With the dogs 68 withdrawn,
the collar 29 of the setting tool can be slid over the coupling assembly 30. This
process is assisted by the internal taper on the collar 29. The V-shaped slots 94
engage with the locator pins 72 to help ensure correct alignment between the setting
tool and the coupling assembly. The snap ring 70 on the coupling assembly 30 engages
with the grooves 93 on the inside surface of the collar 29. This provides a secondary
retaining mechanism to hold the setting tool in place on the gauge hanger while the
dogs 68 are engaged.
[0089] When the setting tool 14 is attached to the gauge hanger 12, the hexagonal drive
shaft 28 in the setting tool fits into the hexagonal socket 76 in the setting nut
62 in the gauge hanger. This allows the motor 24 in the setting tool 14 to rotate
the setting nut 62, and hence the rotator 66.
[0090] Once the collar 29 has been fitted to the coupling assembly 30, the dogs 68 can be
expanded into the slots 92 in the collar. The snap ring 70 and grooves 93 ensure that
the dogs 68 are aligned with the slots 92 in an axial direction. Furthermore, the
locator pins 72 and the V-shaped slots 94 ensure that the dogs 68 are rotationally
aligned with the slots 92.
[0091] The dogs 68 are expanded into the slots 92 by rotating the rotator 66 such that the
lobes of the cam 80 face towards the dogs 68 and push them outwards. The rotator 66
may be rotated, for example, using the motor 24, or in any other way. With the dogs
68 expanded into the slots 92 in the collar, the setting tool 14 is able to hold the
gauge hanger 12 as it is being deployed in the tubing.
[0092] The magnetic force required to hold the gauge hanger against the tubing wall should
only be generated at the desired setting depth. Thus, the upper magnet assembly 32
is arranged such that, when the dogs 68 are expanded (with the lobes of the cam facing
towards the dogs), the switching core 46 is orientated with respect to the base 44
such that the external magnetic field is switched off. Likewise, the lower magnet
assembly 34 is arranged such that, with the dogs 68 expanded, the switching core 54
is orientated with respect to the base 52 such that the external magnetic field is
switched off. This can allow the deployment assembly (comprising setting tool and
gauge hanger) to be lowered into the tubing without attaching to the tubing wall or
other objects.
[0093] Once the setting tool 14 has been attached to the gauge hanger 12, the deployment
assembly is lowered into the tubing using the deployment wire 15. The deployment wire
15 is connected to a surface hoist, which lowers the deployment assembly until it
is at the required depth. Suitable surface hoists are known in the art and thus not
described further. As the deployment assembly is being lowered into the tubing, the
dogs 68 are held in the expanded position by the cam 80. This ensures that the setting
tool remains attached to the gauge hanger as it is being lowered.
[0094] Once the deployment assembly has reached the desired depth, the switchable magnets
in the upper magnet assembly 32 and the lower magnet assembly are activated. This
is achieved using the motor 24 in the setting tool 14. The motor 24 rotates the drive
shaft 28, and hence the setting nut 62, rotator 66 and rotator shaft 40 in the coupling
assembly 30 and the switching core 46 in the upper magnet assembly 32. Rotation of
the switching core 46 relative to the base 44 activates the external magnetic field,
causing the upper magnet assembly 32 to attach to the wall of the tubing. At the same
time, the switching core 54 in the lower magnet assembly 34 is rotated respect to
the base 52 via rotation of the instrument 10. Rotation of the switching core 54 relative
to the base 52 activates the external magnetic field, causing the lower magnet assembly
34 to attach to the wall of the tubing.
[0095] Operation of the motor 24 is controlled by the control unit 26 using signals received
by the communications module 27 from a surface operator. This can allow the surface
operator to deploy the gauge hanger at the required depth. Alternatively, the communications
module may be dispensed with, and the setting tool 14 may be arranged to deploy the
gauge hanger 12 after a certain time delay or in response to certain measurements
such as depth measurements.
[0096] As the switching cores 46, 54 in the upper and lower magnet assemblies 32, 34 are
rotated, the rotator 66 and the washer 64 also rotate. As the rotator 66 and the washer
64 rotate, they start drawing the dogs 68 inwards. The coupling assembly is arranged
such that the dogs 68 remain engaged with the slots 92 in the collar 29 until sufficient
magnetic force has been generated to reliably attach the gauge hanger to the tubing
wall. Further rotation of the rotator 66 and the washer 64 draws the dogs 68 out of
the slots 92, releasing the setting tool from the gauge hanger.
[0097] Figures 13(A) to 13(C) illustrate operation of the coupling assembly as the magnets
are activated. In Figures 13(A) to 13(C), a top view of the coupling assembly is shown,
with the washer 64 partially cut away.
[0098] Figure 13(A) shows the coupling assembly when the gauge hanger is in the rest state
prior to activation of the switchable magnets. In this state, the switching cores
46, 54 are oriented relative to their respective bases 44, 52 such that no external
magnetic field is produced. At the same time, the lobes of the cam 80 are orientated
towards the dogs 68, forcing them outwards. In this state, the width of the gauge
hanger between the outer edges of the two dogs 68 is W
1. This width is wider than the internal diameter of the collar 29, ensuring that the
dogs 68 remain in the slots 92.
[0099] Also shown in Figure 13(A) are pins 97. The pins 97 are fitted into the holes 83
in the dogs 68 and extend into the slots 84 in the washer 64. The slots 84 run in
a generally circumferential direction and are orientated such that one end of the
slot is radially outwards of the other (with respect to the axis of rotation). The
washer 64 is attached to the rotator 66 using screws 98, so that the washer rotates
together with the cam 80. In the state shown in Figure 13(A), the dogs 68 are in the
extended position, and the pins 97 are at the radially outwards ends of the slots
84. In this state, the distance between the two pins is D
1.
[0100] Figure 13(B) shows the coupling assembly when the shaft has been rotated through
45° relative to the rest state shown in Figure 13(A). In the state shown in Figure
13(B), the switching cores 46, 54 have been rotated through 45° relative to their
respective bases 44, 52. In this position, a significant proportion of the total available
external magnetic field is already produced. Thus, in this position, the upper and
lower magnetic assemblies produce sufficient external magnetic field to attach themselves
to the tubing wall.
[0101] In Figure 13(B), the washer 64 has been rotated such that the pins 97 are midway
between the two ends of the slots 84. At this point, each pin 97 is in a part of the
slot 84 which is radially inwards with respect to the rest state shown in Figure 13(A).
Thus, rotation of the washer 64 pulls the pins 97 and thus dogs 68 radially inwards.
[0102] In the 45° state shown in Figure 13(B), the distance between the two pins is D
2 where D
2 < D
1. Furthermore, the cam 80 has been rotated such that its lobes are orientated at 45°
to the dogs 68. This allows the dogs 68 to be partially drawn into the coupling assembly.
The width between the outer edges of the two dogs 68 is W
2, where W
2 < W
1. In this example, the width W
2 is approximately equal to the internal diameter of the collar 29. Thus, in this position,
the dogs 68 are at the point of being withdrawn from the slots 92 in the setting tool.
[0103] Figure 13(C) shows the coupling assembly when the gauge hanger is in the engaged
state with the external magnetic fields activated. In this state, the switching cores
46, 54 have been rotated through 90° relative to their respective bases 44, 52. The
total available external magnetic field is produced, ensuring that the gauge hanger
remains attached to the tubing wall.
[0104] In the state shown in Figure 13(C), the washer 64 has been rotated such that the
pins 97 are at the radially inwards ends of the slots 84. Thus, rotation of the washer
64 pulls the pins 97 and thus dogs 68 radially inwards. The distance between the two
pins is D
3 where D
3 < D
2. Furthermore, the cam 80 has been rotated such that its lobes are orientated at 90°
to the dogs 68. This allows the dogs 68 to be completely drawn into the coupling assembly.
[0105] In the 90° position shown in Figure 13(C), the width between the outer edges of the
two dogs 68 is W
3, where W
3 < W
2. The width W
3 is less than the internal diameter of the collar 29. Thus, in this position, the
dogs 68 are completely withdrawn from the slots 92. Thus, in this position, the setting
tool 14 can be disengaged from the gauge hanger 12.
[0106] The coupling assembly is arranged such that sufficient magnetic force to attach the
gauge hanger to the tubing wall is produced before the setting tool is released from
the gauge hanger. For example, in one exemplary embodiment it has been found that
75% of the magnetic holding force is developed when the switching core is rotated
30° from the "off" position. In this embodiment, the coupling assembly is designed
to remain functionally engaged with the setting tool until at least 45° of rotation
to ensure the setting tool cannot be disengaged before the magnets are set. Of course,
it will be appreciated that these values are given by way of example only, and different
values may be used as appropriate. For example, the shape and/or orientation of the
cam 80 and the slots 84 may be varied in order to vary the point at which the dogs
are withdrawn from the slots 92 in the setting tool.
[0107] As mentioned above, the cam 80 extends partially into a lobe shaped cavity 88 immediately
inwards of the radial slot 87 in the barrel 38. The lobe shaped cavity 88 provides
a positive stopping mechanism, so that rotation of the cam 80 is limited to 90°. This
prevents over rotation of the rotating components, ensuring that the switchable magnets
remain fully activated and the dogs remain fully withdrawn. Thus, in this embodiment
the cam is used both to actuate the dogs and to provide a stopping mechanism.
[0108] When the dogs 68 have been withdrawn from the slots 92, the snap ring 70 and grooves
93 provide a secondary retention mechanism, holding the setting tool in place on the
gauge hanger. A light upwards jarring action on the deployment wire 15 disengages
the snap ring and separates the setting tool from the gauge hanger. Once the setting
tool has been disengaged from the gauge hanger, it can be drawn upwards out of the
wellbore using the deployment wire 15.
[0109] It will be appreciated from the above that the action of rotating the switching cores
in the magnet assemblies in order to engage the switching magnets also draws in the
dogs from the slots in the setting tool. Thus, the same action which is used engage
the magnets is also used to disengage the setting tool from the gauge hanger. This
allows a single actuator (the motor 24) to be used to perform both tasks simultaneously
and ensures that the setting tool can only be disengaged from the gauge hanger when
the magnets are set.
Retrieval
[0110] When it is desired to retrieve the gauge hanger from the wellbore, a retrieval tool
is lowered into the tubing and attached to the gauge hanger. The retrieval tool is
used to deactivate the magnetic force holding the gauge hanger to the tubing wall,
and to lift the gauge hanger to the surface.
[0111] In a preferred embodiment, the setting tool described above is also used as a retrieval
tool to retrieve the gauge hanger. The retrieval tool is lowered into the tubing using
a deployment wire 15 (such as a slickline) connected to a surface hoist.
[0112] When the gauge hanger is in the wellbore, it will be lying against the side of the
tubing in an unknown orientation. The retrieval tool therefore needs to be correctly
orientated over the gauge hanger in order to engage with it. This is achieved using
a collar and guide attached to the bottom of the retrieval tool. In one embodiment,
the collar and guide are in the form shown in Figure 12.
[0113] Referring back to Figure 12, the guide 95 is an elliptical hoop structure and is
fixed to the collar 29 at an angle of 45° to the vertical axis. The outside diameter
of the guide 95 corresponds to the diameter of the tubing in which the gauge hanger
is deployed. The collar has a smaller diameter than the guide, and is located off-centre
of the guide. The guide 95 ensures that, as the retrieval tool is being run into the
tubing, it is located adjacent to the tubing wall. Once the retrieval tool encounters
the gauge hanger, the guide 95 slides past the top of the coupling assembly 30. Downward
movement of the guide past the coupling assembly rotates the retrieval tool in the
tubing until it is aligned with the coupling assembly. The collar 29 then slides over
the coupling assembly 30. The collar 29 has an internal taper to help it ride over
the coupling assembly. The two V-shaped slots 94 on the collar 29 ride over the locating
pins 72. This ensures that the dogs 68 are aligned with the slots 92 rotationally
and axially.
[0114] To engage the snap ring 70 with the grooves 93, some downwards force is required.
The retrieval tool is therefore provided with sufficient weight to snap the ring into
place as the collar 29 slides over the coupling assembly 30.
[0115] In addition to mating the snap ring 70 and locating pins 72, the hexagonal shaft
28 from the retrieval tool must also seat inside the hexagonal socket 76 on top of
the coupling assembly. Gentle up and down movement of the retrieval tool (via the
slickline) may be required to assist the process of mating the snap ring, locator
pins and hexagonal shaft. Alternatively, the retrieval tool could be provided with
vibration producing means which cause the tool to vibrate once contact was made, which
would assist in mating the three elements. The vibration may be produced, for example,
by the motor 24 or using a separate vibrator.
[0116] Once the retrieval tool is seated on the gauge hanger, the motor 24 is used to rotate
the drive shaft 28, and hence the setting nut 62, washer 64, rotator 66 and rotator
shaft 40 in the coupling assembly 30 and the switching cores 46, 54 in the upper and
lower magnet assemblies 32, 34. The rotation is in the opposite direction to that
which was used to activate the magnets and disengage the dogs from the slots during
the setting process. Operation of the motor 24 is controlled by the control unit 26
using signals received by the communications module 27 from a surface operator. Alternatively,
the retrieval tool may be arranged to rotate the motor after a certain time delay
or in response to a measurement signal.
[0117] As the washer 64 and the rotator 66 rotate, the lobes on the cam 80 rotate towards
the dogs 68, pushing the dogs outwards into the slots 92 in the collar 29. This process
is the reverse of that described above with reference to Figures 13(A) to 13(C). At
the same time, the switching cores 46, 54 in the upper and lower magnet assemblies
32, 34 are rotated. This begins the process of deactivating the switchable magnets.
However, the magnet assemblies 32, 34 are arranged such that sufficient magnetic force
to attach the gauge hanger to the tubing wall is still produced at least until the
dogs 68 have reliably engaged with the slots 92. This ensures that the magnets do
not disengage before the retrieval tool is attached to the gauge hanger. Further rotation
of the switching cores 46, 54 then deactivates the switchable magnets, releasing the
gauge hanger from the tubing wall. The lobe shaped cavity 88 in the barrel 38 provides
a positive stopping mechanism, so that rotation of the cam 80 is limited to 90° (i.e.,
at the rest position shown in Figure 13(A)). This prevents over rotation of the rotating
components, ensuring that the switchable magnets remain deactivated, and the dogs
fully expanded.
[0118] When the gauge hanger is released from the tubing wall, the weight of the gauge hanger
is taken by the retrieval tool and the slickline. At this point, the weight of the
gauge hanger is noticeable on a weight indicator on the slickline. This provides an
indication to the operator that the retrieval tool is connected to the gauge hanger
and the gauge hanger is disengaged from the tubing wall. The retrieval tool and gauge
hanger can then be lifted to the surface using the slickline.
[0119] It will be appreciated from the above that the action of rotating the cam to expand
the dogs into the slots also rotates the switching cores in the magnet assemblies.
However, the mechanism is arranged such that the switchable magnets are not deactivated
until the dogs are engaged with the slots. Thus, the same action which is used secure
the retrieval tool to the gauge hanger is also used to deactivate the magnets, disengaging
the gauge hanger from the tubing wall. This allows a single actuator (the motor 24)
to be used to perform both tasks simultaneously and ensures that the gauge hanger
is only disengaged from the tubing wall once the retrieval tool is attached.
[0120] When retrieving a gauge hanger that has been in a well for some time, some close-fitting
parts may have become encrusted with scales and contaminants. In this case, some force
may be required to rotate the magnetic cores and to push the dogs out through the
slots in the retrieving tool.
[0121] In some embodiments, a hammering rotating mechanism is provided in the retrieval
tool to overcome "stiction" in the rotating components. This may be in the form of
an impact driver driven by an electro-mechanical device. In this case, the driver
will hammer for several cycles in the clockwise direction (when viewed from above
as in Figures 13(A) to 13(C)) and then stop in that position with the cam firmly rotated
to a stop in the internal lobe with the dogs pushed out in the retrieval tool slots.
[0122] Embodiments of the invention have been described above by way of example only, and
various modifications are possible. For example, the cam and dogs assembly could be
provided in the setting tool and the slots could be provided in the gauge hanger.
In this case, the gauge hanger could be provided with a collar which fits around the
lower part of the setting tool, and the slots could be provided in the collar. In
either case, rather than using a cam and dogs assembly, any other appropriate engagement
mechanism, such as an elliptical engagement member rotatable directly into a slot,
could be used instead. Rather than using a shaft on the setting tool to engage with
a socket on the gauge hanger, the gauge hanger could be provided with a shaft which
engages with a socket on the setting tool. Rather than using two magnet assemblies,
a single magnet assembly could be used to hold the gauge hanger. Alternatively, three
or more magnet assemblies could be used, with an instrument between two successive
magnet assemblies. If desired, a shaft rather than the instrument itself could be
used to rotate the lower magnet assembly or assemblies. Various other modifications
and variations in detail will be apparent to the skilled person within the scope of
the appended claims.
1. A gauge hanger (12) for deployment in a wellbore using a setting tool (14), the gauge
hanger comprising:
a switchable magnet (32, 34) for attaching the gauge hanger to a wellbore wall; and
a coupling assembly (30) for coupling the gauge hanger to the setting tool;
wherein the switchable magnet (32, 34) and the coupling assembly (30) are arranged
to be actuated by a common actuator (24).
2. A gauge hanger according to claim 1, wherein the switchable magnet (32, 34) is switchable
between a deactivated state and an activated state, and, in the activated state, the
switchable magnet produces an external magnetic field sufficient to attach the gauge
hanger to the wellbore wall.
3. A gauge hanger according to claim 1 or 2, wherein the coupling assembly (30) is switchable
between an engaged state and a disengaged state, and, in the engaged state, the setting
tool is attached to the gauge hanger.
4. A gauge hanger according to any of the preceding claims, wherein switching the switchable
magnet (32, 34) to an activated state also switches the coupling assembly to a disengaged
state.
5. A gauge hanger according to claim 4, wherein the coupling assembly (30) is not switched
to a disengaged state until the switchable magnet (32, 34) is switched to an activated
state.
6. A gauge hanger according to any of the preceding claims, wherein switching the coupling
assembly (30) to an engaged state also switches the switchable magnet (32, 34) to
a deactivated state.
7. A gauge hanger according to claim 6, wherein the switchable magnet (32, 34) is not
switched to a deactivated state until the coupling assembly is switched to the engaged
state.
8. A gauge hanger according to any of the preceding claims, wherein the switchable magnet
(32, 34) comprises a rotatable core (46, 54), and rotation of the rotatable core switches
the switchable magnet between an activated state and a deactivated state.
9. A gauge hanger according to any of the preceding claims, wherein the coupling assembly
comprises a rotatable element (66), and rotation of the rotatable element switches
the coupling assembly between an engaged state and a disengaged state.
10. A gauge hanger according to claim 9, wherein the coupling assembly comprises at least
one engagement member (68) for engagement with the setting tool, and the rotatable
element (66) comprises a cam which is arranged to displace the at least one engagement
member.
11. A gauge hanger according to any of the preceding claims, further comprising a secondary
retention mechanism (70) for holding the setting tool and the gauge hanger together
when the coupling assembly is in a disengaged state.
12. A gauge hanger according to any of the preceding claims, the gauge hanger comprising
a plurality of switchable magnets (32, 34) for attaching the gauge hanger to the wellbore
wall, wherein a switchable magnet is preferably provided on either side of an instrument
(10), and the instrument is preferably used to transfer rotation between the switchable
magnets.
13. A deployment assembly comprising a setting tool (14) and a gauge hanger (12) according
to any of the preceding claims, wherein the setting tool comprises an actuator (24)
arranged to actuate the coupling assembly and the switchable magnet.
14. A deployment assembly according to claim 13, wherein the setting tool comprises a
collar (29) arranged to slide over the coupling assembly, wherein the collar preferably
comprises one or more of:
an internal taper;
a V-shaped slot arranged to ride over a locator pin on the coupling assembly;
an internal groove arranged to receive a snap ring on the coupling assembly; and
one or more slots arranged to receive an engagement member,
and wherein the setting tool preferably comprises a guide arranged to locate the setting
tool in the wellbore relative to the gauge hanger.
15. A method of deploying a gauge hanger in a wellbore, the method comprising:
coupling the gauge hanger (12) to a setting tool (14);
lowering the gauge hanger and setting tool in the wellbore;
attaching the gauge hanger to a wellbore wall by activating a switchable magnet (32,
34); and
decoupling the setting tool from the gauge hanger,
wherein activating the switchable magnet and decoupling the setting tool are actuated
by a common actuator (24).