GAUGE HANGER

Abstract

A gauge hanger for deployment in a wellbore using a setting tool is disclosed. The gauge hanger comprises 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. The switchable magnet and the coupling assembly are arranged to be actuated by a common actuator such as a motor in the setting tool.

Claims

1. A gauge hanger arranged to be deployed in a wellbore using a setting tool, the gauge hanger comprising: a switchable magnet arranged to attach the gauge hanger to a wellbore wall; and a coupling assembly arranged to couple the gauge hanger to the setting tool; wherein the switchable magnet and the coupling assembly are arranged to be actuated by a common actuator.

2. A gauge hanger according to claim 1, wherein the switchable magnet 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, wherein the coupling assembly 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 claim 1, wherein switching the switchable magnet 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 is not switched to the disengaged state until the switchable magnet is switched to the activated state.

6. A gauge hanger according to claim 1, wherein switching the coupling assembly to an engaged state also switches the switchable magnet to a deactivated state.

7. A gauge hanger according to claim 6, wherein the switchable magnet is not switched to the deactivated state until the coupling assembly is switched to the engaged state.

8. A gauge hanger according to claim 1, wherein the switchable magnet comprises a rotatable core, and rotation of the rotatable core switches the switchable magnet between an activated state and a deactivated state.

9. A gauge hanger according to claim 1, wherein 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.

10. A gauge hanger according to claim 9, wherein the rotatable element is rotated synchronously with a rotatable core in the switchable magnet.

11. A gauge hanger according to claim 9, wherein the coupling assembly comprises at least one engagement member for engagement with the setting tool, and the rotatable element comprises a cam which is arranged to displace the at least one engagement member.

12. A gauge hanger according to claim 1, further comprising a secondary retention mechanism for holding the setting tool and the gauge hanger together when the coupling assembly is in a disengaged state.

13. A gauge hanger according to claim 1, the gauge hanger comprising a plurality of switchable magnets for attaching the gauge hanger to the wellbore wall.

14. A gauge hanger according to claim 13, wherein one of the plurality of switchable magnets is provided on either side of an instrument, and the instrument is used to transfer rotation between the plurality of switchable magnets.

15. 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.

16. A deployment assembly according to claim 15, wherein the setting tool comprises the common actuator arranged to actuate the coupling assembly and the switchable magnet.

17. A deployment assembly according to claim 15, wherein the setting tool comprises a collar arranged to slide over the coupling assembly, wherein the collar 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; or one or more slots arranged to receive an engagement member.

18. A deployment assembly according to claim 15, wherein the setting tool comprises a guide arranged to locate the setting tool in the wellbore relative to the gauge hanger.

19. 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.

20. A method according to claim 19, the method further comprising: lowering a retrieval tool into the wellbore; coupling the retrieval tool to the gauge hanger; and deactivating the switchable magnet attaching the gauge hanger to the wellbore wall, wherein coupling the retrieval tool and deactivating the switchable magnet are actuated by the common actuator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Preferred embodiments of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which:

[0065] FIG. 1 shows an overview of a wellbore system;

[0066] FIGS. 2(A) and 2(B) illustrate the principles of a switchable magnet;

[0067] FIG. 3 shows parts of a deployment assembly in an embodiment of the invention;

[0068] FIG. 4 shows parts of an upper magnet assembly and a coupling assembly;

[0069] FIG. 5 is a cross-section through the upper magnet assembly and the coupling assembly;

[0070] FIG. 6 shows parts of a lower magnet assembly;

[0071] FIG. 7 is a cross-section through the lower magnet assembly;

[0072] FIG. 8 is an exploded view of a coupling assembly in an embodiment of the invention;

[0073] FIG. 9 is a cross-section through the coupling assembly;

[0074] FIG. 10 shows a barrel of the coupling assembly;

[0075] FIG. 11 shows a dog in the coupling assembly;

[0076] FIG. 12 shows a collar of a setting tool; and

[0077] FIGS. 13(A) to 13(C) illustrate operation of the coupling assembly.

DETAILED DESCRIPTION

Overview

[0078] FIG. 1 shows an overview of a wellbore system in one embodiment. Referring to FIG. 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.

[0079] 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. 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.

[0080] 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.

[0081] 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.

[0082] FIGS. 2(A) and 2(B) illustrate the principles of a switchable magnet in one exemplary embodiment. In FIGS. 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.

[0083] When the switching core 18 is in the off position, as shown in FIG. 2(A), the poles of the magnet are orientated towards the block 22 of non-ferrous material. 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 FIG. 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

[0084] 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: [0085] The magnetic force required to hold the gauge hanger against the wall is only generated at the desired setting depth. [0086] The magnetic force holding the gauge hanger against the wall is removable at the set depth during retrieval. [0087] 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. [0088] The magnet is engaged before the setting tool releases the gauge hanger. [0089] 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. [0090] 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. [0091] The gauge hanger has a low profile to allow other tools to pass by it in as small a tubing size as possible. [0092] 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.

[0093] FIG. 3 shows parts of a deployment assembly in an embodiment of the invention. Referring to FIG. 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).

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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 FIGS. 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.

[0098] In the arrangement of FIG. 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.

[0099] 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 34 in place relative to each other and ensure that the magnets are always aligned.

[0100] 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 14 to be removed once the gauge hanger 12 has been set at the required depth.

[0101] 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.

[0102] FIG. 4 shows parts of the upper magnet assembly and the coupling assembly in more detail. Referring to FIG. 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 FIGS. 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.

[0103] In the arrangement of FIG. 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 FIG. 3).

[0104] In FIG. 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.

[0105] FIG. 5 is a cross-section through the upper magnet assembly and the coupling assembly in the assembled state. Referring to FIG. 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.

[0106] FIG. 6 shows parts of the lower magnet assembly in more detail. Referring to FIG. 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.

[0107] 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.

[0108] 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.

[0109] FIG. 7 is a cross-section through the lower magnet assembly in the assembled state. Referring to FIG. 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.

[0110] FIG. 8 is an exploded view of a coupling assembly in an embodiment of the invention. Referring to FIG. 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] FIG. 9 is a cross-section through the coupling assembly 30 in the assembled state. In the view shown in FIG. 9, the lobes of the cam 80 are orientated perpendicular to the plane of the paper. Referring to FIG. 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.

[0116] FIG. 10 shows the barrel 38 of the coupling assembly 30 in more detail. Referring to FIGS. 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.

[0117] Also visible in FIG. 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.

[0118] FIG. 11 shows one of the dogs in more detail. Referring to FIG. 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.

[0119] 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.

[0120] 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.

[0121] Referring back to FIG. 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.

[0122] FIG. 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 FIG. 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] Deployment

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] FIGS. 13(A) to 13(C) illustrate operation of the coupling assembly as the magnets are activated. In FIGS. 13(A) to 13(C), a top view of the coupling assembly is shown, with the washer 64 partially cut away.

[0139] FIG. 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.sub.1. This width is wider than the internal diameter of the collar 29, ensuring that the dogs 68 remain in the slots 92.

[0140] Also shown in FIG. 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 FIG. 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.sub.1.

[0141] FIG. 13(B) shows the coupling assembly when the shaft has been rotated through 45? relative to the rest state shown in FIG. 13(A). In the state shown in FIG. 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.

[0142] In FIG. 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 FIG. 13(A). Thus, rotation of the washer 64 pulls the pins 97 and thus dogs 68 radially inwards.

[0143] In the 45? state shown in FIG. 13(B), the distance between the two pins is D.sub.2 where D.sub.2<D.sub.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.sub.2, where W.sub.2<W.sub.1. In this example, the width W.sub.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.

[0144] FIG. 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.

[0145] In the state shown in FIG. 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.sub.3 where D.sub.3<D.sub.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.

[0146] In the 90? position shown in FIG. 13(C), the width between the outer edges of the two dogs 68 is W.sub.3, where W.sub.3<W.sub.2. The width W.sub.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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] Retrieval

[0152] 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.

[0153] 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.

[0154] 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 FIG. 12.

[0155] Referring back to FIG. 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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 FIGS. 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 FIG. 13(A)). This prevents over rotation of the rotating components, ensuring that the switchable magnets remain deactivated, and the dogs fully expanded.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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 FIGS. 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.

[0164] Embodiment 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.