GB2573314A

GB2573314A - Wear bushing and seal assembly retrieval tool

Info

Publication number: GB2573314A
Application number: GB1807250.4A
Authority: GB
Inventors: Telfer George
Original assignee: Ardyne Holdings Ltd
Current assignee: Ardyne Holdings Ltd
Priority date: 2018-05-02
Filing date: 2018-05-02
Publication date: 2019-11-06
Anticipated expiration: 2038-05-02
Also published as: GB201807250D0; GB2573314B

Abstract

A system which can selectively pull a modified wear bushing 12 either alone or with a seal assembly 28 to save multiple trips into the well. The system has a retrieval tool, comprising a modified wear bushing coupled to a running tool 14. The running tool has a first latching mechanism 78 and a second latching mechanism 78’, the first latching mechanism having a first latch selectively operable to contact a shoulder on the modified wear bushing and allow retrieval of the modified wear bushing, and the second latching mechanism having a second latch selectively operable to operate an activation mechanism 56 which couples the seal assembly to the modified wear bushing for retrieval. When landed, the running tool can pass through the wear bushing to allow operations in the well on the same trip as installing and retrieving the wear bushing and seal assembly.

Description

WEAR BUSHING AND SEAL ASSEMBLY RETRIEVAL TOOL

The present invention relates to apparatus and methods for retrieving wear bushings and seal assemblies from a wellhead and in particular, though not exclusively, to a wear bushing and seal assembly retrieval tool which can selectively pull the wear bushing either alone or with the seal assembly to save multiple trips into the well.

In a typical wellhead, a seal assembly is located between the wellhead and casing hanger to seal the annulus between these component parts. A wear bushing is then installed to land upon the casing hanger. The wear bushing is used to protect the seal assembly and casing hanger from damage when a drill string is run in or pulled out through the wellhead.

Typically multiple trips are required into the well to install the seal assembly, install the wear bushing, run the drill string to perform a downhole operation, retrieve the wear bushing and then retrieve the seal assembly, if required. In drilling applications, only the wear bushing is removed. For this application, bit run and retrieval wear bushings have been developed.

US 2003/0192704 to Vetco Gray Inc. describes a wear bushing which has a lower portion that is landed on a casing hanger in a wellhead housing. The wear bushing is mounted to the running tool, which is joined to a drill string. With running-in keys locked on the tool, the wear bushing is lowered down the well into the wellhead housing. The wear bushing is landed on the casing hanger and anti-rotation pins are pressed upward as they contact a seal assembly. The wear bushing is rotated until the antirotation pins align and fall into slots. With the anti-rotation pins in the slots, the running tool is released from the wear bushing by opposite rotation, and the running tool may then be run deeper into the well. The wear bushing can be extracted using the running tool as the drill string is pulled back to surface. In an alternative embodiment a running tool can be provided which does not pull the wear bushing when pulled back to surface. A separate retrieval tool is then run. This retrieval tool may be the same as the running tool of the first embodiment.

This allows the steps of installing the wear bushing, running the drill string to perform a downhole operation and retrieving the wear bushing to be completed on a single trip in the well. However, a disadvantage is that a user must decide whether or not the wear bushing is going to be retrieved before they make-up the drill string as this will determine the running tool used. In the event that the single trip run and retrieval running tool is used and the drilling operation cannot be completed in a single trip, the wear bushing will be removed and a replacement must be found and made-up for a further run in the well bore.

This lack of selectivity when the drill string is in the well bore provides greater consequences for applications in which the seal assembly is also being removed. For well abandonment in which a cut and pull operation is performed, the seal assembly needs to be removed before the cut section of casing can be pulled from the well bore. Equally, the seal assembly must be in place when an integrity test is performed on the plug in the casing to be cut. This would typically require multiple trips into the well bore. US 6,629,565 to Smith International, Inc. discloses a well abandonment process and apparatus for cutting and retrieving an offshore well casing, the process comprising: making a trip to the well wherein all of the following steps are performed, the steps comprising: pulling a seal assembly from the wellhead, cutting the casing, gripping the casing, and retrieving the seal assembly and cut casing. Thus this advantageously combines the steps of cutting and pulling the casing along with pulling the seal assembly to save a further trip into the well. The seal assembly retrieval tool is run on the drill string with the casing cutter and spear. The seal assembly retrieval tool is at a fixed position in the drill string. When run, the seal assembly retrieval tool engages the seal assembly and an integrity test can be performed with the seal assembly in place. The casing cutter will be at a set distance below the seal assembly and the casing can be cut at this position or the drill string can be pulled from the well to raise the cutting position. In raising the drill string, the seal assembly is raised. Thus you have no choice in whether the seal assembly is removed or not. This arrangement therefore cannot be used to test the integrity of the plug on the same trip because if the test fails you are committed to pulling the seal assembly. This breaches safety requirements. Further some operators stipulate that the seal assembly must be in place during cutting, which is only possible at a single cutting location with this apparatus due to the fixed separation distance between the seal assembly and the casing cutter.

It is therefore an object of the present invention to provide a wear bushing and seal assembly retrieval tool which allows selective removal of the seal assembly when the tool is at the seal assembly in the well bore.

It is a further object of the present invention to provide a wear bushing and seal assembly retrieval tool which allows selective removal of the wear bushing when the tool is at the seal assembly in the well bore.

According to a first aspect of the present invention there is provided a wear bushing and seal assembly retrieval tool, comprising:

a modified wear bushing, the modified wear bushing configured to locate in a wellhead housing, having a throughbore for the unimpeded passage of a drill string therethrough; a plurality of seal assembly retrieval fingers operable via an activation mechanism to couple the modified wear bushing to a seal assembly in the wellhead housing; and a first shoulder on a wall of the throughbore;

a running tool for mounting in the drill string, the running tool having a tubular body with first and second selectable latching mechanisms: the first latching mechanism operable in a first configuration to cause a first latch to contact the first shoulder and retrieve the modified wear bushing and in a second configuration to disengage the latch and allow removal of the running tool without retrieving the modified wear bushing;

the second latching mechanism operable in a third configuration to function the activation mechanism and couple the modified wear bushing to the seal assembly and in a fourth configuration to disengage a second latch and allow removal of the running tool without retrieving the seal assembly; and wherein the first and second latching mechanisms are independently operable and the running tool can pass through the modified wear bushing and be run further into the well.

In this way, the wear bushing can selectively be retrieved with or without the seal assembly. Additionally, the wear bushing and seal assembly can be left in place as the drill string is run-in or pulled out of the well for other operations to be carried out with there selective retrieval on final pull-out if desired.

Preferably, the first latch and the second latch each comprise a plurality of retrieval elements, biased radially outwards from the running tool. In this way, the first latching mechanism is biased to retrieve the wear bushing and the second latching mechanism is biased to operate the activation mechanism and thereby couple the seal assembly to the wear bushing on pulling the running tool from the well bore.

Preferably, the first latching mechanism is releasably coupled to the modified wear bushing on run in. In this way, the running tool is used to locate the wear bushing in the wellhead housing. Preferably at least one of the retrieval elements of the first latch is releasably coupled to the modified wear bushing by a shear bolt. In this way, the running tool can be released from the wear bushing when the wear bushing lands in the wellhead.

Preferably, the plurality of seal assembly retrieval fingers are arranged equidistantly around the modified wear bushing and biased radially inwards to be clear of the seal assembly until the activation mechanism is operated. In this way, the seal assembly is not coupled to the wear bushing in use, so that the seal assembly cannot be inadvertently pulled if a formation on the drill string such as a collar catches on a portion of the wear bushing.

Preferably the activation mechanism comprises a drive sleeve located in the throughbore, the sleeve having an outer conical face at an upper end to engage with an orientated angled surface on an inner end of each seal assembly retrieval finger, so as to force the seal assembly retrieval fingers radially outwards on upward movement of the drive sleeve. In this way, the seal assembly retrieval fingers can be moved radially outwards to engage a receptacle of the seal assembly. Preferably the drive sleeve is held against the seal assembly retrieval fingers in the third configuration to couple the modified wear bushing to the seal assembly. More preferably, the drive sleeve has an annular face arranged perpendicularly to the throughbore at the lower end wherein the retrieval elements of the second latch engage the annular face and move the drive sleeve upwardly and operate the activation mechanism.

Preferably, the second latching mechanism is in a fifth configuration on run in wherein the retrieval elements of the second latch are arranged inside the drive sleeve. In this way, the second latch is prevented from activating the seal assembly retrieval fingers on run-in.

Preferably, each latching mechanism includes a disabling sleeve, releasably coupled to an inner wall of the throughbore of the running tool, the disabling sleeve including: a biasing spring arranged to urge the first/second latch radially outwards, a pocket into which a portion of the first/second latch can locate and a drop ball seat. In this way, a drop ball can be used to move the sleeve and the biasing spring so that the latch locates in the pocket and is held away from the modified wear bushing. In this way, the first latching mechanism can be placed in the second configuration and the second latching mechanism can be placed in the fourth configuration.

Preferably, the retrieval elements of the first and second latches act as drag blocks when running tool is located below the wellhead.

According to a second aspect of the present invention there is provided a method of running a wear bushing in a well, comprising the steps:

(a) mounting a modified wear bushing on a running tool in a drill string according to the first aspect;

(b) running the drill string into a well and landing the modified wear bushing on a wellhead housing;

(c) releasing the running tool from the modified wear bushing and running the drill string further into the well;

(d) completing an operation in the well;

(e) pulling the drill string from the well bore with the first and second latching mechanisms positioned in one of the group comprising:

first latching mechanism in the first configuration and second latching mechanism in the third configuration so as to retrieve the modified wear bushing and the seal assembly, first latching mechanism in the first configuration and second latching mechanism in the fourth configuration so as to retrieve the modified wear bushing and leave seal assembly in the wellhead housing, and first latching mechanism in the second configuration and second latching mechanism in the fourth configuration so as leave the modified wear bushing and the seal assembly in the wellhead housing.

In this way, the wear bushing is selectably retrieved with or without the seal assembly on a single trip in the well bore.

Optionally, in step (e) with the first latching mechanism in the first configuration and second latching mechanism in the third configuration so as to retrieve the modified wear bushing and seal assembly, in the event that the seal assembly sticks and cannot be retrieved, the method includes the further step of moving the second latching mechanism to the fourth configuration and retrieving the wear bushing and leaving the seal assembly in place. This provides a fail-safe arrangement when the seal assembly cannot be removed and will need to be drilled out.

Preferably the method includes the step of operating the activation mechanism by contacting the second latch on a drive sleeve and moving the drive sleeve longitudinally in the throughbore against an end of the plurality of seal assembly retrieval fingers to move them radially outwards into a receptacle on the seal assembly.

Preferably, step (a) includes arranging the first latching mechanism in the first configuration and arranging the second latching mechanism in the fifth configuration wherein the step further includes connecting the first latch to the modified wear bushing by a releasable coupling. In this way, the running tool and the modified wear bushing are coupled together on run-in.

Preferably the method includes the step of dropping a ball from surface down through the drill string into the throughbore to move the second latching mechanism to the fourth configuration.

More preferably, the drop ball engages a disabling sleeve of the second latching mechanism and moves it so that the second latch is retracted into a pocket of the disabling sleeve. In this way, the second latch is prevented from operating the activation mechanism in the fourth configuration. Further, the method may include the step of deactivating the activation mechanism so as to move the seal assembly retrieval fingers radially inwards and disengage the seal assembly from the modified wear bushing.

Preferably the method includes the step of dropping a ball from surface down through the drill string into the throughbore to move the first latching mechanism to the second configuration. More preferably, the drop ball engages a disabling sleeve of the first latching mechanism and moves it so that the first latch is retracted into a pocket of the disabling sleeve. In this way, the second latch is prevented from contacting the shoulder in the second configuration.

In the description that follows, the drawings are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form, and some details of conventional elements may not be shown in the interest of clarity and conciseness. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce the desired results.

Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as including, comprising, having, containing, or involving, and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps. Likewise, the term comprising is considered synonymous with the terms including or containing for applicable legal purposes.

All numerical values in this disclosure are understood as being modified by about. All singular forms of elements, or any other components described herein including (without limitations) components of the apparatus are understood to include plural forms thereof. Furthermore, relative terms such as, lower, upper, up, down and the like are used herein to indicate directions and locations as they apply to the appended drawings and will not be construed as limiting the invention and features thereof to particular arrangements or orientations. Likewise, the term inlet shall be construed as being an opening which, dependent on the direction of the movement of a fluid may also serve as an outlet, and vice versa.

There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which:

Figure 1 is a schematic illustration of a wellbore illustrating a casing hanger with seal assembly in a wellhead in which is located a wear bushing;

Figure 2 is a cross-sectional view of a wear bushing and seal assembly retrieval tool, being run-in and landing on a wellhead housing, according to an embodiment of the present invention;

Figure 3 is a sectional view through the line A-A' of Figure 2 showing the arrangement of seal assembly retrieval fingers of the retrieval tool of Figure 2;

Figure 4 is a sectional view through the line B-B' of Figure 2 showing the first latching mechanism of the retrieval tool of Figure 2;

Figure 5(a) is a cross-sectional view through the modified wear bushing of the retrieval tool of Figure 2 during further operations in a well and Figure 5(b) is a cross-sectional view of the running tool of the retrieval tool of Figure 2 during further operations in the well;

Figure 6 is a cross-sectional view of a wear bushing and seal assembly retrieval tool, arranged to retrieve the wear bushing and the seal assembly, according to an embodiment of the present invention;

Figure 7 is a cross-sectional view of a wear bushing and seal assembly retrieval tool, arranged to retrieve the wear bushing and leave the seal assembly in place, according to an embodiment of the present invention; and

Figure 8 is a cross-sectional view of a wear bushing and seal assembly retrieval tool, arranged to leave the wear bushing and seal assembly in place, according to an embodiment of the present invention.

Referring initially to Figure 1 of the drawings there is illustrated a wear bushing and seal assembly retrieval tool, generally indicated by reference numeral 10, comprising a modified wear bushing 12 and a running tool 14, with the modified wear bushing landed in a wellhead housing 16 and the running tool 14 being located on a drill string 32 in a well 20, according to an embodiment of the present invention.

The well 20 of Figure 1 is a typical arrangement in which a wellhead 22 provides access to a subsea well 20. For simplicity only two casings are shown, with an inner casing string 24 supported from a casing hanger 26 mounted in the wellhead housing 16. A seal assembly 28 is used to seal the annulus 30. A wear bushing 12 is landed in the wellhead 22 against the casing hanger 26 to protect the seal assembly 28 and the casing hanger 26 from damage when a drill string 32 is run in or pulled out through the wellhead 22. The drill string 32 is run from a rig/platform or vessel 34 through a riser 36. In Figure 1, the wear bushing 12 is a modified wear bushing according to an embodiment of the present invention and a running tool 14, for the modified wear bushing 12, is shown on the drill string 32 at a location deeper in the well 20, according an embodiment of the present invention.

Reference is now made to Figure 2 of the drawings which illustrates a wear bushing and seal assembly retrieval tool 10 comprising a modified wear bushing 12 and accompanying running tool 14. The retrieval tool 10 is shown in the wellhead 22, with like parts to those of Figure 1 given the same reference numeral to aid clarity. It will be appreciated by those skilled in the art that the shape and configuration of the wellhead housing 16, seal assembly 28 and casing hanger 26 will vary depending on the manufacturer. However, those shown in Figure 2 include the main characteristics including a groove 38 in the seal assembly 28, used for locating and retrieving the seal assembly 28.

In the present invention, the modified wear bushing 12 has an outer shape to match the inner shape of the wellhead 22. In this regard the wear bushing 12 is formed in three parts, so that it can be adapted for different wellhead 22 designs. However, it may be of unitary or multiple part construction. A seal retrieval portion 40 sits between a lower portion 42 shaped to land on the casing hanger 26 and an upper portion 44 to protect the seal retrieval portion 40 and seal assembly 28. Each part 40,42,44 of the wear bushing provides a central throughbore 46 for the passage of the drill string 32.

The upper portion 44 includes a downward facing shoulder 48 being an annular rim or ledge around an inner surface 50 of the wear bushing 12. There is also a shear bolt 52 (one is shown but there may be more spaced around the circumference) which provides the connection to the running tool 14.

The seal retrieval portion 40 has an activation mechanism 54 used to selectively move seal assembly retrieval fingers 56a-h from a retracted position inside the wear bushing 12 to a radially extended position to sit in the groove 38 of the seal assembly 28. Figure 3 shows the eight seal assembly retrieval fingers 56a-h arranged circumferentially around the wear bushing 12. Each finger 56a-h is biased radially inwards by an individual spring 58a-h. Each finger 56a-h has a distal end 60a-h shaped to match the profile of the groove 38 and an orientation pin 62a-h to ensure the profiles align for engagement to provide maximum loading when the seal assembly 28 is to be retrieved. The activation mechanism 54 has an activation sleeve 64 which is a ring located in the throughbore 46. At an upper end, the activation sleeve 64 has a conical face 66 initially arranged against sloped end faces 68 of the fingers 56a-h. The activation sleeve 64 is biased against the lower portion 42 via a spring 70 leaving a lower annular end face 72 exposed in the throughbore 46.

Now considering the running tool 14. This has a cylindrical body 74, with connections (not shown) to be made-up in the drill string 32. Towards an upper end 76, there is a first latching mechanism, generally indicated by reference numeral 78. The first latching mechanism can be seen in crosssection in Figure 4. Four retrieval blocks 80a-d provide a first latch 82. Each block 80a-d is arranged through the body 74 and retained thereto via a block retainer bar 84a-d and retainer bolt 86a-d. Springs 88a-d within each block 80a-d bias each block 80a-d in a retracted position. The blocks 80a-d are held in a position in which the outer face 90a-d protrudes from the outer surface 92 of the body 74 by virtue of a strong leaf spring 94 located in a pocket 96 of a disabling sleeve 98, being arranged against a back surface lOOa-d of each block 80a-d. Disabling sleeve 98 is an annular sleeve located inside a throughbore 102 of the running tool 14 and attached to the body 74 via a shear screw 104. The sleeve 98 has a ball seat 106 at an upper end 108 thereof. The pocket 96 is an annular groove or recess in the outer surface 110 of the sleeve 98. Ports 112 are also provided through the sleeve 98 from the outer surface 110 to an inner surface 114. A further pocket 128 is arranged in the inner surface 130 of the body 74. Pocket 128 provides a fluid passage around the ball seat 106 via the ports 112, when a ball is located in the seat 106.

Towards a lower end 116 of the running tool 14 there is located a second latching mechanism, generally indicated by reference number 78'. The second latching mechanism 78' has the same components as the first latching mechanism 78 and these have been given the same reference numerals but suffixed with an apostrophe for reference. The second disabling sleeve 98' is shorter than the first 98, with shorter but wider retrieval blocks 80'a-d. This is because the retrieval blocks 80a-d of the first latching mechanism 78 are used to lift the entire wear bushing 12. The inner diameter of the central bore 118 of the first disabling sleeve 98 is greater than the inner diameter of the central bore 118' of the second disabling sleeve 98' so that a drop ball can fall through the first sleeve 98 and seat in the ball seat 106' of the second sleeve 98'.

In use, the wear bushing and seal retrieval tool 10 is first configured as shown in Figure 2. On the running tool 14, the sleeves 98,98' are connected to the body 74 via the shear screws 104,104'. This locates the leaf springs 94,94' under the retrieval blocks 80a-d,80'a-d, and forces the blocks 80,80' radially outwards. The modified wear bushing 12 has the seal assembly retrieval fingers 56 retracted into the activation mechanism 54. The first latch 82, is connected to the wear bushing 12 by locating the retrieval blocks 80a-d below and against the shoulder 48 on the upper portion 44. The shear bolt(s) 52 are located through the upper portion 44 and screwed into the retrieval blocks 80a-d. The second latch 82' is disengaged and the second retrieval blocks 80'a-d are arranged within the activation sleeve 64. This can be considered as the run-in arrangement with the first latching mechanism 78 in the first configuration and the second latching mechanism 78' in the fifth configuration. The modified wear bushing 12 is supported on the running tool 12 by the shoulder 48 and shear bolts 52.

The wear bushing and seal assembly retrieval tool 10 is made-up on the drill string 32 and run in the well 20 until the lower portion 42 contacts the casing hanger 26. By continuing to set down weight on the string 32 the bolts 52 will shear and the running tool 14 will continue through the wear bushing 12 into the well 20. While the second retrieval blocks 80'a-d on the running tool 14 will move radially outwards on clearing the activation sleeve 64, the sloped surfaces of the blocks 80'a-d and the casing hanger 26 will allow the running tool 14 to move into the well 20 with the retrieval blocks 80a-d,80'a-d acting as drag blocks. Figure 5(a) shows the modified wear bushing 12 landed in the wellhead housing 20 and providing protection to the seal assembly 28 and casing hanger 26. It is also noted that there is a large throughbore 46 for the unimpeded passage of a drill string 32. Figure 5(b) shows the running tool 14 located further into the well 20. At this location in the well 20, the casing or liner 120, is pushing the retrieval blocks 80,80' radially inwards against the leaf springs 94,94' and the action of the of the retrieval blocks 80,80' as drag blocks is evident. It is noted that a fluid passageway exists both in the throughbore 102 of the running tool 14 and in the annulus 122 between the tool 14 and casing/liner 120 around the retrieval blocks 80,80'. In this way, other downhole operations can be performed from the string 32 which require circulation in the well 20.

When we are ready to come pull the drill string 32 out of the well, a decision must be made as to whether the wear bushing 12 is to be pulled either alone or with the seal assembly 28. For casing cutting and pulling operations it is beneficial if the wear bushing 12 and seal assembly 28 are retrieved together as this can save multiple trips into the well 20. If this is decided, the drill string 32 can be pulled to raise the running tool 14 through the wear bushing 12. The first latch 82 will pass over the activation sleeve 64 of the activation mechanism 54, as the length of the first retrieval blocks 80a-d is greater than the distance between the end face 75 of the activation sleeve 64 and the greatest inward projection of the casing hanger 26. If the first latch 82 causes upward movement of the activation sleeve 64 by friction due to dragging on the blocks 80a-d, the upward movement will cause the seal assembly retrieval fingers 56 to be forced radially outwards. This does not cause a problem as the fingers 56 will retract when the blocks 80a-d clear the activation sleeve 64.

The second latch 82' is short enough to extend into the space between the end face 75 of the activation sleeve 64 and the greatest inward projection of the casing hanger 26. This is assisted by there being sloping surfaces on the retrieval blocks 80' and the inner surface of the casing hanger 26. A side edge 124 of the retrieval blocks 80' contacts end face 75 of the activation sleeve 64 and drives it upwards. Movement is limited by a shoulder 126 on the activation sleeve 64 meeting a stop 128 on the body 136 of the activation mechanism 54. In this position the activation sleeve 64 has pushed the fingers 56 radially outwards and holds them in this extended position to engage in the groove 38 of the seal assembly 28.

Meanwhile the first latch 82 has relocated against the shoulder 48. The first latching mechanism 78 is in the first configuration and the second latching mechanism 78' is in the third configuration as illustrated in Figure

6. Now by pulling the string 32, the running tool 14 will pull the wear bushing 12, by virtue of the contact on the shoulder 48, and the seal assembly 28, by virtue of the fingers 56 located in the groove 38. In this way, the wear bushing 12 and the seal assembly 28 are retrieved from the well 20 on the same trip as when the wear bushing 12 was landed and an operation in the well has been performed.

If it is desired to only pull the wear bushing 12 and leave the seal assembly 28, as may be required if further operations are required in the well 20, a first ball 126 is dropped through the bore of the drill string 32 from surface. The ball 126 is sized to pass through the bore 118 of the first latching mechanism 78 and land in the ball seat 106' of the second latching mechanism 78'. Pressure on the ball 126 forces the disabling sleeve 98' downwards shearing the screw 104'. The sleeve 98' will travel down until it reaches an upset 132 on the inner surface 130 of the body 74. In this position, the leaf spring 94' has been moved from supporting the retrieval block 80' and consequently, springs 88' in the retrieval block 80' will cause the block to be retracted back into the pocket 96' which is now clear. Retraction of the retrieval block 80' into the body 74 releases the activation sleeve 64 causing it to be biased back to its initial position by virtue of the spring 70. The seal assembly retrieval fingers 56a-h will also retract by virtue of the springs 58a-h as the sloped end faces 68 now meet the conical face 66 of the activation sleeve 64.

When the drill string 32 is pulled to lift the running tool 14 into the wellhead housing 16, the first latch 82 will relocate against the shoulder 48, while the second latch remains within the body 74 of the tool 14. This is illustrated in Figure 7 with the first latching mechanism 78 in the first configuration and the second latching mechanism 78' in the fourth configuration. Continued pulling of the drill string 32 will now retrieve the wear bushing 12 and leave the seal assembly 28 in place.

If the wear bushing 12 and seal assembly 28 are being retrieved together, as described with reference to Figure 6, and the seal assembly 28 sticks and cannot be pulled, the arrangement of Figure 7 can be used. The retrieval tool 10 can be converted by dropping the ball 126 to switch the second latching mechanism 78' from the third configuration to the fourth configuration. This will allow the wear bushing 12 to be removed with the running tool 14 on the drill string 32. The seal assembly 28 can then be recovered on another trip with appropriate equipment.

A further arrangement is shown in Figure 8. This is used when the it is desired to come out of the well leaving the wear bushing 12 and seal assembly 28 in place. This would be needed if the operation in the well cannot be completed and an additional trip is required. A first ball 126 is dropped from surface through the bore 102 to switch the second latching mechanism 78' from the third configuration to the fourth configuration as described herein with reference to Figure 7. A second ball 134 is then dropped from surface though the bore 102. The second ball 134 has a greater diameter than the first ball 126 and is sized to seat in the ball seat 106 of the first latching mechanism 78. Pressure on the ball 134 forces the disabling sleeve 98 downwards shearing the screw 104. The sleeve 98 will travel down until it reaches an upset on the inner surface 130 of the body 74 at the top of the further pocket 128'. The upset is shown as a castellation to allow fluid flow to be maintained around the first ball 126 in the ball seat 106'. In this position, the leaf spring 94 has been moved from supporting the retrieval block 80 and consequently, springs 88 in the retrieval block 80 will cause the block to be retracted back into the pocket 96 which is now clear. Retraction of the retrieval block 80 into the body 74 prevents the block 80 contacting the shoulder 48. The first latching mechanism 78 is now in the second configuration and the second latching mechanism 78' is in the fourth configuration. The drill string 32 and running tool 14 will now pass unimpeded through the bore 46 of the wear bushing 12 leaving the seal assembly 28 and wear bushing 12 in place.

The running tool 14 can be redressed at surface to reposition the disabling sleeves 98,98'. With the first latching mechanism 78 in the first configuration and the second latching mechanism 78' in the third configuration, the running tool 14 can be run into the well 20 to a position below the wellhead 22 and then used as described hereinbefore to selectively retrieve the wear bushing with or without the seal assembly.

The principal advantage of the present invention is that it provides a wear bushing and seal assembly retrieval tool which allows selective removal of the seal assembly when the tool is at the seal assembly in the well bore.

A further advantage of an embodiment of the present invention is that it provides a wear bushing and seal assembly retrieval tool which allows selective removal of the wear bushing when the tool is at the seal assembly in the well bore.

The foregoing description of the invention has been presented for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention herein intended. For example, the numbers of retrieval blocks and seal assembly retrieval fingers can be varied to suit the dimensions and weights of wellhead components. Biasing arrangements other than the springs shown may be used.

Claims

1. A wear bushing and seal assembly retrieval tool, comprising:

2. A wear bushing and seal assembly retrieval tool according to claim 1 wherein the first latch and the second latch each comprise a plurality of retrieval elements, biased radially outwards from the running tool.

3. A wear bushing and seal assembly retrieval tool according to claim 1 or claim 2 wherein the first latching mechanism is biased to retrieve the wear bushing and the second latching mechanism is biased to operate the activation mechanism and thereby couple the seal assembly to the wear bushing on pulling the running tool from the well bore.

4. A wear bushing and seal assembly retrieval tool according to any preceding claim wherein the first latching mechanism is releasably coupled to the modified wear bushing on run in.

5. A wear bushing and seal assembly retrieval tool according to claim 4 wherein at least one of the retrieval elements of the first latch is releasably coupled to the modified wear bushing by a shear bolt.

6. A wear bushing and seal assembly retrieval tool according to any preceding claim wherein the plurality of seal assembly retrieval fingers are arranged equidistantly around the modified wear bushing and biased radially inwards to be clear of the seal assembly until the activation mechanism is operated.

7. A wear bushing and seal assembly retrieval tool according to any preceding claim wherein the activation mechanism comprises a drive sleeve located in the throughbore, the drive sleeve having an outer conical face at an upper end to engage with an orientated angled surface on an inner end of each seal assembly retrieval finger, so as to force the seal assembly retrieval fingers radially outwards on upward movement of the drive sleeve.

8. A wear bushing and seal assembly retrieval tool according to claim 7 wherein the drive sleeve is held against the seal assembly retrieval fingers in the third configuration to couple the modified wear bushing to the seal assembly.

9. A wear bushing and seal assembly retrieval tool according to claim 7 or claim 8 wherein the drive sleeve has an annular face arranged perpendicularly to the throughbore at the lower end wherein the retrieval elements of the second latch engage the annular face and move the drive sleeve upwardly and operate the activation mechanism.

10. A wear bushing and seal assembly retrieval tool according to claim 7 wherein the second latching mechanism is in a fifth configuration on run in wherein the retrieval elements of the second latch are arranged inside the drive sleeve.

11. A wear bushing and seal assembly retrieval tool according to any preceding claim wherein the second latch is prevented from activating the seal assembly retrieval fingers on run-in.

12. A wear bushing and seal assembly retrieval tool according to any preceding claim wherein each latching mechanism includes a disabling sleeve, releasably coupled to an inner wall of the throughbore of the running tool, the disabling sleeve including: a biasing spring arranged to urge the first/second latch radially outwards, a pocket into which a portion of the first/second latch can locate and a drop ball seat.

13. A wear bushing and seal assembly retrieval tool according to any one of claims 2 to 12 wherein the retrieval elements of the first and second latches act as drag blocks when the running tool is located below the wellhead.

14. A method of running a wear bushing in a well, comprising the steps:

(a) mounting a modified wear bushing on a running tool in a drill string according to any one of claims 1 to 13;

(d) completing an operation in the well;

15. A method of running a wear bushing in a well according to claim

14 wherein in step (e) with the first latching mechanism in the first configuration and second latching mechanism in the third configuration so as to retrieve the modified wear bushing and seal assembly, in the event that the seal assembly sticks and cannot be retrieved, the method includes the further step of moving the second latching mechanism to the fourth configuration and retrieving the wear bushing and leaving the seal assembly in place.

16. A method of running a wear bushing in a well according to claim 14 or claim 15 wherein the method includes the step of operating the activation mechanism by contacting the second latch on a drive sleeve and moving the drive sleeve longitudinally in the throughbore against an end of the plurality of seal assembly retrieval fingers to move them radially outwards into a receptacle on the seal assembly.

17. A method of running a wear bushing in a well according to claim

14 wherein step (a) includes arranging the first latching mechanism in the first configuration and arranging the second latching mechanism in the fifth configuration wherein the step further includes connecting the first latch to the modified wear bushing by a releasable coupling.

18. A method of running a wear bushing in a well according to any one of claims 14 to 17 wherein the method includes the step of dropping a first ball from surface down through the drill string into the throughbore to move the second latching mechanism to the fourth configuration.

19. A method of running a wear bushing in a well according to claim 18 wherein the drop first ball engages a disabling sleeve of the second latching mechanism and moves it so that the second latch is retracted into a pocket of the disabling sleeve.

20. A method of running a wear bushing in a well according to any one of claims 14 to 19 wherein includes the step of deactivating the activation mechanism so as to move the seal assembly retrieval fingers radially inwards and disengage the seal assembly from the modified wear bushing.

21. A method of running a wear bushing in a well according to any 5 one of claims 14 to 20 wherein the method includes the step of dropping a second ball from surface down through the drill string into the throughbore to move the first latching mechanism to the second configuration.

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22. A method of running a wear bushing in a well according to claim

21 wherein the drop second ball engages a disabling sleeve of the first latching mechanism and moves it so that the first latch is retracted into a pocket of the disabling sleeve.