GB2573317A

GB2573317A - Improvements in or relating to well abandonment and slot recovery

Info

Publication number: GB2573317A
Application number: GB1807256.1A
Authority: GB
Inventors: Wardley Michael
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: GB2573317B; GB201807256D0

Abstract

A single trip casing cutting and pulling assembly which selectively retrieves the seal assembly. This allows an integrity test to be performed on the same trip. The assembly includes a casing cutter 12, a casing spear 14, and a device 16 for retrieving a wear bushing and seal assembly, including a wear bushing 18 on a running tool 20. The running tool includes latching mechanisms to selectively latch the seal assembly to the modified wear bushing and running tool. When the modified wear bushing is landed in the wellhead housing, the running tool can pass through the modified wear bushing to allow cutting and pulling at any depth within the well, with the seal assembly remaining in the wellhead housing. The assembly can be used to remove the wear bushing and seal assembly, or alternatively can be tripped from the well without retrieving the bushing and seal assembly in the event of a failed integrity test.

Description

IMPROVEMENTS IN OR RELATING TO WELL ABANDONMENT AND SLOT RECOVERY

The present invention relates to apparatus and methods for well abandonment and slot recovery and in particular, though not exclusively, to single trip casing cutting and pulling system which can selectively retrieve the seal assembly on the same trip.

When a well has reached the end of its commercial life, the well is abandoned according to strict regulations in order to prevent fluids escaping from the well on a permanent basis. In meeting the regulations it has become good practise to create the cement plug over a predetermined length of the well and to remove the casing. Current techniques to achieve this may require multiple trips into the well, for example: to pull the wear bushing from the wellhead; to pull the seal assembly from the wellhead; to set a bridge plug to support cement; to cut the casing above the plug; to pull the cut casing from the well; and create a cement plug to cement across to the well bore wall. The cement or other suitable plugging material forms a permanent barrier to meet the legislative requirements.

Each trip into a well takes substantial time and consequently significant costs. Combined casing cutting and pulling tools have been developed so that the cutting and pulling of the casing can be achieved on a single trip. Such a tool is the TRIDENT® System to the present Applicants, Ardyne Technologies Limited.

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, griping 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.

In US 6,629,565 a casing cutting and pulling tool is suspended from an offshore vessel or platform by connection to a drill pipe. At the top of the casing cutting and pulling tool, there is a seal assembly retrieval tool mounted in the drill string, which is used to pull the seal assembly of interior casing or intermediate casing in a wellhead. Below the seal assembly retrieval tool, the casing cutting and pulling tool also has a bumper jar, a spear, a long stroke bumper jar, a mud motor and a casing cutter, all connected to each other in series in the order given.

In one embodiment, the procedure for operation of the system is as follows. Trip in the hole until the seal assembly retrieving tool is about to the seal in the wellhead. It is important to allow for enough space out to trip seal assembly into riser. Next, engage the seal assembly with the seal assembly retrieval tool. Then pull the seal assembly and the casing cutting and pulling tool up into riser. The casing cutter is then spotted at the desired cutting depth. With the casing cutter in the correct location, a slight left-hand torque is applied to engage the spear (1/4 turn) to grip the casing. The casing is then cut and the spear is disengaged by a right-hand torque to release its grip on the casing. The casing cutting and pulling tool is then pulled out of the hole until the spear is just below the wellhead. A left-hand torque is then applied to engage the spear to grip the casing. Next, the casing cutting and pulling tool is pulled out of the hole with the casing. The seal assembly and seal assembly retrieval tool are then laid out at the surface. The casing cutting and pulling tool is then pulled further out of the hole until the casing hanger is landed out on rotary table. It should be spaced out so that the spear can be racked in the derrick. The spear is then disengaged and racked back in the derrick. Finally, the casing is rigged up and laid down on the derrick.

Since the spear is engaged to grip the casing before the casing is cut with the casing cutter, the casing may be cut in tension. In particular, with the spear engaged, the operator of the casing cutting and pulling tool may pull up on the drill pipe so that the casing experiences an applied pressure in tension. With tension pressure applied to the casing during the cutting procedure, the chances of a successful cut are greatly increased. Once the seal assembly is pulled the casing may be cut with the spear at any depth below the wellhead.

There are a number of disadvantages in the apparatus and process described in US 6,629,595. While it states that once the seal assembly is pulled the casing may be cut with the spear at any depth below the wellhead, this is not the case as the maximum depth will be limited to the distance between the spear and the seal assembly retrieval tool as the drill string is stopped when the seal assembly retrieval tool reaches the seal assembly. At this point only shallower depths can be achieved and even this is limited by the requirement for sufficient space out to trip the seal assembly through the riser. Additionally, the seal assembly must remain attached to and supported by the drill string during the cutting of the casing. This means that the drill string cannot be fully rotated from surface to rotate the cutting blades and cut the casing. As described above, only quarter turns are therefore achievable. This limits the operating modes available for use on the cutting and pulling tool. In particular a mud motor has to be present on the drill string to rotate the cutter.

Further, this arrangement does not allow an integrity test to be performed on the same trip. The first stage of a cut and pull operation is to integrity test the plug in the casing to be cut. Known integrity tests are to inflow and/or negative pressure testing and/or drill and tag which sets down weight on the plug. Only when the integrity of the plug is assured, can the casing be cut and pulled. The seal assembly must be in place when an integrity test is performed on the plug in the casing to be cut. Equally, if the test fails then then the seal assembly must be left in place while a new plug or remedial work is carried out and the test repeated. When run, the seal assembly retrieval tool of US 6,629,565 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 at least one embodiment of the present invention to provide a one trip casing cutting and pulling system which allows the selective retrieval of the seal assembly and which obviates or mitigates one or more disadvantages of the prior art.

It is therefore an object of at least one embodiment of the present invention to provide a method of cutting and pulling casing which selectively retrieves the seal assembly to allow an integrity test to be performed on the same trip as the cut and pull operation and which obviates or mitigates one or more disadvantages of the prior art.

According to a first aspect of the present invention there is provided a casing cutting and pulling assembly located on a drill string comprising: a casing spear to anchor to casing in a well bore;

a casing cutter configured to cut the casing; and a modified wear bushing and seal assembly retrieval device, the retrieval device comprising a modified wear bushing and a running tool:

the modified wear bushing configured to locate in a wellhead housing, having an axial throughbore for the unimpeded passage of the drill string therethrough, and an engagement mechanism for connecting the modified wear bushing to a seal assembly; and the running tool being configured to mount in the drill string and having a first latching mechanism operably selectable downhole to a first configuration to couple the modified wear bushing to the running tool and retrieve the modified wear bushing with the seal assembly and a second configuration to prevent coupling and allow removal of the running tool without retrieving the modified wear bushing and the seal assembly; and wherein when the modified wear bushing and seal assembly retrieval device is landed in the wellhead housing, the running tool can be run deeper in the well to position the casing cutter at multiple locations in the casing.

In this way, when the assembly needs to be tripped out of the well the operator has a choice as to whether they will pull the modified wear bushing and seal assembly. An integrity test can therefore be performed with the seal assembly in place. Casing can be cut and pulled at any position in the well with the seal assembly remaining in place, if desired, until the cut casing is pulled, at which time the seal assembly can be pulled as the running tool is tripped through the wellhead. Thus casing cutting and pulling with seal assembly retrieval and performance of the plug integrity test is achieved on a single trip.

Preferably the first latching mechanism is biased to the first configuration and the device includes a first delatching mechanism selectively operable to prevent latching of the running tool to the modified wear bushing. In this way the device can be configured to automatically retrieve the modified wear bushing and seal assembly, with the first delatching mechanism being operated only when a failure occurs in the operating procedure i.e. when an integrity test fails.

Preferably there is a second latching mechanism, the second latching mechanism operably selectable downhole to a third configuration activating the engagement mechanism to couple the modified wear bushing to the seal assembly and a fourth configuration to prevent activation of the engagement mechanism. In this way, a user can decide whether the seal assembly is to be attached to the modified wear bushing therefore allowing its retrieval, or it may be left unattached so that the modified wear bushing can be retrieved independently from the seal assembly. This may be useful if the seal assembly sticks and cannot be retrieved on the running tool.

Preferably the second latching mechanism is biased to the fourth configuration and the device includes a second delatching mechanism selectively operable to prevent latching of the modified wear bushing to the seal assembly.

In this way, the modified wear bushing can selectively be retrieved with or without the seal assembly. Additionally, the modified 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 their selective retrieval on final pull-out if desired.

Preferably the engagement mechanism comprises 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. Preferably, the second latching mechanism includes a second latch which is operable in the third configuration to function the activation mechanism and couple the modified wear bushing to the seal assembly.

Preferably the modified wear bushing has a first shoulder on a wall of the throughbore and the first latching mechanism is operable in the first configuration to cause a first latch to contact the first shoulder and retrieve the modified wear bushing. In this way, the modified wear bushing is automatically picked-up and retrieved with the cut casing section.

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 modified wear bushing in the wellhead housing.

Preferably the modified wear bushing has a substantially cylindrical body and at least a portion of an outer surface of the body has a profile to match an inner surface of a seal assembly into which the retrieval device is deployed. In this way the modified wear bushing and seal assembly retrieval device can be modelled from a standard wear bushing as would be used with the seal assembly.

Preferably the casing spear and casing cutter are located on the drill string below the running tool. In this way, the casing spear and casing cutter can be operated at any depth below the wellhead. Preferably casing cutter is operated by full rotation of the drill string. The unimpeded passage of the drill string through the modified wear bushing allows rotation also and therefore a motor is not required to operate the casing cutter.

Preferably one or more tools are located on the drill string below the running tool. Preferably, the one or more tools includes a packer. More preferably, the packer is a mechanical tension-set retrievable packer. In this way, the packer can be set by pulling or releasing tension on the drill string. Preferably, the casing spear is located between the mechanical tension-set retrievable packer and the casing cutter. In this way, casing can be cut under tension and pressure and/or circulation tests can be performed.

The one or more tools may further include a drill, the drill being located at a distal end of the drill string. Mounting a drill bit on the end of the drill string allows initial dressing of a cement plug prior to casing cutting being achieved on the same trip into the wellbore.

Alternatively, the one or more tools may further include a bridge plug, the bridge plug being located at a distal end of the drill string. Mounting a bridge plug on the end of the drill string allows setting of a bridge plug in the casing prior to casing cutting being achieved on the same trip into the wellbore.

According to a second aspect of the present invention there is provided a method of cutting and pulling casing, the method comprising the steps:

(a) providing a casing cutting and pulling assembly according to the first aspect and locating the running tool of the modified wear bushing and seal assembly retrieval device, the casing spear and the casing cutter in order on a drill string wherein the running tool supports the modified wear bushing;

(b) running the drill string through the wellhead and into a wellbore;

(c) landing the modified wear bushing in the wellhead housing;

(d) running the drill string through the modified wear bushing when the modified wear bushing and seal assembly are in the wellhead housing;

(e) locating the running tool, casing spear and casing cutter below the wellhead at a position at which casing is to be cut;

(f) cutting the casing;

(g) pulling the drill string through the wellhead with the first latching mechanism in the first configuration so to raise the modified wear bushing and seal assembly;

(h) pulling the drill string to locate the casing spear towards an upper end of a cut section of casing and gripping the cut section of casing with the casing spear; and (i) pulling the drill string so as to recover the cut section of casing with the modified wear bushing and the seal assembly.

In this way, the drill string can operate below the wellhead without any restriction on depth or operating configuration so that casing can be cut at any location and the seal assembly may remain in place in the wellhead during casing cutting.

Preferably the method includes the step of performing an integrity test on a plug in casing which is to be cut between steps (d) and (e). More preferably, the steps are performed on a single trip. In this way, an integrity test, cutting and pulling casing and retrieving the seal assembly are all performed on the same trip in the well.

Preferably, the method includes the steps of switching the first latching mechanism between the first and second configurations with the assembly in the wellbore and removing the casing cutting and pulling assembly with the running tool from the wellbore with the modified wear bushing and the seal assembly left in the wellhead.

In an alternative embodiment, the modified wear bushing and seal assembly are selectably connectable downhole and the method may include the steps of switching a second latching mechanism between third and fourth configurations with the assembly in the wellbore, and removing the casing cutting and pulling assembly with the running tool and the modified wear bushing from the wellbore while leaving the seal assembly in the wellhead. This allows an operator to choose whether to retrieve the seal assembly with the modified wear bushing.

These steps which leave the seal assembly in place, may be taken in the event that the integrity test fails and the method would then include the additional steps of inserting a further plug and testing the integrity of the further plug. These additional steps may be completed on the same trip to reinsert the casing cutting and pulling assembly with the running tool before completing the remaining method steps to remove the cut section of casing with the modified wear bushing and the seal assembly.

By being able to select which configurations to operate the device in the wellbore, an integrity test can be performed on the same run as the casing cutting and pulling and seal retrieval operations safe in the knowledge that the in the event of failure of the integrity test or other operational difficulty, the assembly can be tripped out of the well while leaving the seal assembly in place. Removal of the casing cutting and pulling assembly without retrieving the seal assembly allows the assembly to be modified, redressed or repaired or further tools to be run in the wellbore during the cut and pull operation.

Optionally, in step (h) 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 modified 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 at step (a), releasably coupling the modified wear bushing to the running tool and by step (d) decoupling the modified wear bushing from the running tool. In this way the modified wear bushing is carried into the wellbore and positively located in the wellhead housing.

Preferably the method includes the step of rotating the drill string through the modified wear bushing when the seal assembly is in the wellhead housing. In this way, tools which operate by revolutions of the drill string can be used in the well bore.

Preferably the drill string is rotated to operate the casing cutter. Alternatively, the casing cutter can be operated by a motor arranged on the drill string.

Preferably step (f) includes actuating the casing spear to anchor the drill string to the casing in the well bore to hold the casing in tension during step (g). In this way the casing is advantageously cut in tension.

Preferably the method includes at step (a) locating a packer on the drill string below the running tool. Preferably the method includes the further step of actuating the packer to seal an annulus between the drill string and casing in the well bore. Preferably the method includes the step of setting down weight on the drill string to set the packer. Alternatively the method includes the step of applying an upward force or tension to the drill string to set the packer. In this way, a mechanical tension-set packer may be used. The packer may be used to perform the integrity test.

Preferably the method includes the step of performing a circulation test to determine circulation behind the cut tubular at surface. This provides a positive circulation test and the cut casing section, can be removed. Preferably the circulation test is performed between steps (h) and (i). This provides the necessary access behind the cut tubular to determine if circulation occurs.

The method may include the further steps of pulling the drill string through the modified wear bushing when the modified wear bushing is in the wellhead housing to locate the casing cutter at a shallower depth in the casing and cutting the casing at the shallower depth. This will be needed in the event that the circulation test is negative, there being no circulation behind the cut tubular.

The method may include repeating the circulation test and cutting casing at increasingly shallower depths until a positive circulation test occurs and a section of cut tubular can be removed from the wellbore.

The method may include locating a drill bit on the end of the drill string and dressing off a cement plug in the casing on same trip.

Alternatively, the method may include locating a bridge plug on the end of the drill string and setting the bridge plug in the casing on same trip.

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:

Figures 1A to 1H provide schematic illustrations of a casing cutting and removal assembly in a method according to an embodiment of the present invention;

Figure 2 is a part cross sectional view through a modified wear bushing and seal assembly retrieval device for use in a casing cutting and pulling assembly according to an embodiment of the present invention.

Referring to Figures 1A to 1H there is illustrated a casing cutting and pulling assembly, generally indicated by reference numeral 10, including a casing cutter 12, a casing spear 14, a modified wear bushing and seal assembly retrieval device 16 which comprises a modified wear bushing 18 and a running tool 20, mounted in order upon a drill string 22, according to an embodiment of the present invention.

The casing cutting and pulling assembly 10 is used to cut and remove a casing section 24 from a well 26. The well shown in Figures 1A to 1H is a typical arrangement in which a wellhead 28 provides access to a subsea well 26. For simplicity only two casings are shown, with an inner casing string 30 supported from a casing hanger 32 mounted in the wellhead housing 34. A seal assembly 36 is used to seal the annulus 38. As is known in the art a modified wear bushing 18 is landed in the wellhead 28, see Figure IB, against the casing hanger 32 to protect the seal assembly 36 and the casing hanger 32 from damage when a drill string 22 is run in or pulled out through the wellhead 28. The drill string 22 is run from a rig/platform or vessel 42 through a riser 44. In Figures 1A to 1H, the modified wear bushing 18 is a modified wear bushing according to an embodiment of the present invention and a running tool 20, for the modified wear bushing 18, is shown on the drill string 22 at a location deeper in the well 26 with the seal assembly 36 remaining in the wellhead housing 34, at Figure 1C, according an embodiment of the present invention.

Reference is now made to Figure 2 of the drawings which illustrates a modified wear bushing and seal assembly retrieval device 16 comprising a modified wear bushing 18 and accompanying running tool 20 suitable for use in the casing cutting and pulling assembly 10. The retrieval tool 16 is shown in the wellhead 28, with like parts to those of Figures 1A to 1H 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 34, seal assembly 36 and casing hanger 32 will vary depending on the manufacturer. However, those shown in Figure 2 include the main characteristics including a groove 44 in the seal assembly 36, used for locating and retrieving the seal assembly 36.

In the example device 16, the modified wear bushing 18 has an outer shape to match the inner shape of the wellhead 28 and provides a central throughbore 52 for the passage of the drill string 22.

In an upper portion 50 there is a formation or downward facing shoulder 54 being an annular rim or ledge around an inner surface 56 of the modified wear bushing 18. There is also a shear bolt 58 (one is shown but there may be more spaced around the circumference) which provides a releasable connection to the running tool 20.

A seal retrieval portion 46 has an engagement mechanism 45 used to selectively move seal assembly retrieval fingers 60 from a retracted position inside the modified wear bushing 18 to a radially extended position to sit in the groove 44 of the seal assembly 36. The engagement mechanism 45 is operated by an activation mechanism 62, being a sleeve 64 biased to allow the fingers 60 to be in the retracted position.

The running tool 20 has a cylindrical body 68, with connections (not shown) to be made-up in the drill string 32. Towards an upper end there is a first latching mechanism 66 comprising four retrieval blocks 70 arranged around the tool and biased in a retracted position. The blocks 70 are in an extended position, as shown in the Figure, via springs 72 of a delatching mechanism 74. The delatching mechanism 74 can be operated from surface via a drop ball to move and thereby release the block 70 from the spring 72 allowing the block 70 to retract into the body 68 of the tool 20. There is a second latching mechanism 66' and delatching mechanism 74' arranged opposite the activation sleeve 64.

For run-in the device 16 is set-up as illustrated in Figure 2. The latching mechanisms 66,66' are held radially outwards. A block 70 of the first latching mechanism 66 contacts the shoulder 54 of the modified wear bushing 18 and is held thereto by the shear bolt 58. The second latching mechanism 66' is free of the activation sleeve 64 and the engagement mechanism 45 is arranged with the fingers 60 retracted. This may be considered as a fifth configuration. Once landed in the wellhead 28, the bolt 58 will shear and the running tool 20 is freed and clear to move downwards into the wellbore 26. If tripped back out, the first latching mechanism 66 will engage shoulder 54 and pick-up the modified wear bushing 18 while the second latching mechanism 66' picks up the activation sleeve 64 and thereby causes the engagement mechanism 45 to couple the modified wear bushing 18 to the seal assembly 36 via extension of the fingers 60 into the groove 44. This may be considered as a first configuration of the first latching mechanism 66 and a third configuration of the second latching mechanism 66' in which the modified wear bushing 18 and seal assembly 36 are retrieved together.

With the running tool 20 below the wellhead 28, dropping a ball through the drill string 22 and the first delatching mechanism 74, can operate the second delatching mechanism 74', by movement of the spring 72 away from the block 70'. The block 70' retracts and will not contact the activation sleeve 64. The fingers 60 remain retracted while the first latching mechanism 66 will pick-up the modified wear bushing 18 on tripping the running tool 20 through the wellhead 28. Thus the modified wear bushing 18 is retrieved but the seal assembly 36 remains in the wellhead housing. This may be considered as the first configuration of the first latching mechanism 66 and a fourth configuration of the second latching mechanism 66'.

Dropping a further ball, larger than the first ball, can operate the first delatching mechanism 74 causing the block 70 to retract into a pocket of the running tool 20. Shoulder 54 is then passed and the running tool 20 is tripped out through the modified wear bushing 18 without picking up either the modified wear bushing or the seal assembly 36. The first latching mechanism 66 has moved to a second configuration while the second latching mechanism 66' remains in the fourth configuration.

It will be appreciated that a simpler device only operating in two configurations may be used. The two configurations would be to retrieve or leave the seal assembly. In this case the engagement mechanism would always be operational so that the modified wear bushing is always retrieved with the seal assembly.

As shown in Figure IB the casing cutting and pulling assembly 10, in a preferred embodiment, has arranged from a first end 82, a drill bit 84, the casing cutter 12, an anchor mechanism being the casing spear 14, a mechanical tension-set retrievable packer 86 and the modified wear bushing and seal retrieval device 16. The casing cutter 12, casing spear 14 and mechanical tension-set retrievable packer 86 may be formed integrally on a single tool body or may be constructed separately and joined together by box and pin sections as is known in the art. Two parts may also be integrally formed and joined to the third part. This arrangement may be the TRIDENT® casing cutting and pulling system offered byArdyne, UK and Norway. A detailed description of a suitable casing cutter 12, a casing spear 14 and a packer 86 is found in WO2018069685 to the present Applicants, incorporated herein by reference. It will be appreciated by those skilled in the art that other casing cutters, casing spears and packers may be used.

In use, the casing cutting and pulling assembly 10 is assembled on a drill string 22 with the drill 84 mounted on the end 82 for dressing a cement plug 88 already located in the casing 30. Alternatively, a bridge plug (not shown) could replace the drill 84 and be set in the casing 30 in place of the cement plug 88.

Referring to Figure 1A, there is illustrated the well 26 prior to deployment of the casing cutting and pulling assembly 10. The seal assembly 36 is in place on the wellhead 28 to seal the annulus 38 to the casing string 30. A cement plug 88 is shown in the casing string 30. Referring to Figure IB of the drawings, the casing cutting and pulling assembly 10 is run-in the well 26, in the fifth configuration, through the wellhead 28 and into the casing string 30 until the modified wear bushing and seal assembly retrieval device 16 lands in the wellhead 28.

On landing in the wellhead housing 34, the modified wear bushing 18 will contact the casing hanger 32. Continued weight on the string 22 will cause the bolt 58 to shear and the running tool 20 will be released from the modified wear bushing 18 and be free to travel through the bore 52 of the modified wear bushing 18 and into the casing string 30. Note that the seal assembly 36 remains in position in the wellhead housing 34 maintaining the seal on the annulus 38. The modified wear bushing 18 acts as a standard modified wear bushing preventing damage to the seal assembly 36 and casing hanger 32. The seal assembly 36 is not coupled to the modified wear bushing 18 so that if something were to catch on the modified wear bushing such as a drill collar, the modified wear bushing 18 can be lifted without causing the seal assembly 36 to inadvertently be moved.

The drill string 22 is free to travel any distance into the casing string 30, its movement not being restricted by the modified wear bushing and seal assembly retrieval device 16, as in the prior art. The blocks 70,70' of the latching mechanisms 66,66' will act as drag blocks as they travel through the casing 30. The drill string 22 is run-in until the drill bit 84 it reaches the cement plug 88 and the drill 84 is used to dress the cement plug 88. At this point a wellbore integrity test is performed using the casing spear 14 and the mechanical tension-set retrievable packer 86 as the seal assembly 36 is in place. This positive and negative pressure test will determine the integrity of the cement plug 88 and the casing 30 around it. This is as illustrated in Figure 1C and the steps required are as known in the art.

If the integrity test is successful, then the drill string 22 is positioned by being raised to pull up the casing cutting and pulling assembly 10 and locate the blades 90 of the casing cutter 12 at a desired location to cut the casing

30. At this position, the casing spear 14 is hydraulically actuated to grip the casing surface 92 to secure the axial position of the tool 10 in the wellbore and the string 22 rotated from the rig 42 to operate the cutter 12. Note that the casing 30 is held in tension when the casing cutter 12 is operated. Also of note is that as the running tool 20 is located adjacent the other components 12,14,86 of the assembly 10, it is kept clear of and below the wellhead 28. In this way, the annulus 38 is kept sealed with the seal assembly 36 in place in the wellhead 28 during cutting of the casing 30. This is a requirement for some operators. This is shown in Figure ID.

If it is a requirement of the casing cutter 12 that the seal assembly 36 is removed for the passage of fluid, for example, the running tool 20 can be located higher in the drill string so that the seal assembly is raised before the cutting position is reached.

The use of a mechanically set retrievable packer 86 allows rapid setting of the packer 86 by pulling of the string 22 against the set casing spear 14, if a kick occurs in the well 26 for any reason. The mechanical tension-set retrievable packer 86 will rapidly set to seal the well 26 and is a safety feature. When the casing cutter 12 has finished cutting the casing, the casing cutter is deactivated and we have a cut section of casing 24 ready for removal.

The drill string 22 with the assembly 10 is now pulled out of the well 26 until the running tool 20 arrives in the wellhead 28. The first latching mechanism 66 contacts the shoulder 54 on the modified wear bushing 18 and is in the first configuration. The second latching mechanism 66' activates the activation mechanism 62 and the engagement mechanism 45 to couple the seal assembly 36 to the modified wear bushing 18, in the third configuration. The running tool 20 will pick-up the modified wear bushing 18 together with the seal assembly 36. This is shown at Figure IE.

At this point, the packer 86 can be set to seal the casing 30 and perform a circulation test since the annulus 38 is now open. Fluid pressure applied through the drill string 22 will exit the casing at the cut 94 and can be detected in the annulus 38 at surface. A positive test indicates that the annulus behind the casing 24 is free of debris which may cause the casing 24 to stick when removed. The cut casing section 24 can now be removed.

Tension applied to the drill string 22 is released to thereby unset the packer 86. The casing spear 14 is released by setting down weight on the drill string 22. The drill string 22 is now pulled out of the well 26 to locate the casing spear 14 at an upper end of the cut section of casing 24. In this position the casing spear 14 is activated to grip the casing section 24 and by pulling the drill string 22 and the casing cutting and pulling assembly 10 from the well 26, the seal assembly 36 is retrieved together with the cut section of casing 24. This is illustrated in Figure IF. The wellbore now contains the casing stub 96 and cement plug 88. The entire procedure has been completed on a single trip.

In the event that the integrity test on the plug 88 fails, then a new plug is required. In this case, the string 22 needs to be tripped out of the well 26. A ball is dropped through the string 22 to operate the second delatching mechanism 66' in the device 16. This will prevent the coupling of the seal assembly 36 to the modified wear bushing 18, placing the second latching mechanism in the fourth configuration. When the assembly 10 is tripped out of the well, the first latching mechanism 66 will engage the modified wear bushing 18 in the first configuration and the second latching mechanism 66' is in the fourth configuration preventing coupling of the seal assembly 36 to the modified wear bushing 18. This is illustrated in Figure 1G. The casing cutting and pulling assembly 10 is retrieved together with the modified wear bushing 18 while the seal assembly 36 remains in place in the wellhead 28 to maintain the seal to the annulus 38. This procedure is not possible in the prior art. The method can be repeated once a new plug is inserted in the casing 30 or a bridge plug can be located on the end 82 of the assembly 10 and run-in with the assembly 10. In completing the casing and pulling operation the running tool 20 would need to be redressed to reposition the delatching mechanism 74' before it could be re-inserted in the wellbore of the well 26.

As an alternative to pulling the modified wear bushing 18 as shown in Figure 1G, the modified wear bushing 18 may also be left in place with the seal assembly 36. This may be done in the event that the integrity test is good but that the blades 90 on the casing cutter 12 need replacement or some other function on the assembly 10 fails. Following the ball being dropped to move the second latching mechanism 66' to the fourth configuration, a second ball is dropped through the drill string 22 to move the first latching mechanism 66 to the second configuration. This delatches the blocks 70 and prevents pick-up of the modified wear bushing 18 on retrieval of the casing cutting and pulling assembly 10. This is as illustrated in Figure 1H. To complete the method, the running tool is redressed by resetting both delatching mechanisms 74,74' and then it can be run back in the well with a redressed, repaired or modified casing cutting and pulling assembly.

In the event that the circulation test is negative, that is a pressure increase is not seen at surface, then it is assumed that cement or other debris is located in the annulus between the cut casing 24 and the formation which will prevent movement and subsequent recovery of the cut casing section 24. The drill string 22 and casing cutting and pulling assembly 10 are then pulled up the casing to locate the blades 90 of the casing cutter 12 at a location higher in the well, shallower depth, on the cut casing section 24. The steps of cutting, testing and pulling can be repeated safe in the knowledge that the seal assembly 36 remains in the wellhead 28.

The principal advantage of the present invention is that it provides a casing cutting and pulling assembly which allows selective removal of the modified wear bushing and seal assembly.

A further advantage of an embodiment of the present invention is that it provides a method of cutting and pulling casing which allows an integrity test to be performed on the same trip as retrieval of the seal assembly.

A yet further advantage of an embodiment of the present invention is that it provides a method of cutting and pulling casing which allows the seal assembly to remain in position during the cut and then retrieves the seal assembly on the same trip in the well.

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, other designs of modified wear bushing and seal assembly retrieval devices can be considered, having other mechanisms to provide the selective operation. Further it will be appreciated that the nonessential method steps may be added to, changed or removed for a single trip.

Claims

1. A casing cutting and pulling assembly located on a drill string comprising:

a casing spear to anchor to casing in a well bore;

the modified wear bushing configured to locate in a wellhead housing, having an axial throughbore for the unimpeded passage of the drill string therethrough, and an engagement mechanism for connecting the modified wear bushing to a seal assembly; and the running tool being configured to mount in the drill string and having a first latching mechanism operably selectable downhole to a first configuration to couple the modified wear bushing to the running tool and retrieve the modified wear bushing with the seal assembly and a second configuration to prevent coupling and allow removal of the running tool without retrieving the modified wear bushing and the seal assembly; and wherein when the modified wear bushing and seal retrieval device is landed in the wellhead housing, the running tool can be run deeper in the well to position the casing cutter at multiple locations in the casing.

2. A casing cutting and pulling assembly according to claim 1 wherein the first latching mechanism is biased to the first configuration and the device includes a first delatching mechanism selectively operable to prevent latching of the running tool to the modified wear bushing.

3. A casing cutting and pulling assembly according to claim 2 there is a second latching mechanism, the second latching mechanism operably selectable downhole to a third configuration activating the engagement mechanism to couple the modified wear bushing to the seal assembly and a fourth configuration to prevent activation of the engagement mechanism.

4. A casing cutting and pulling assembly according to claim 3 wherein the second latching mechanism is biased to the fourth configuration and the device includes a second delatching mechanism selectively operable to prevent enagagement of the modified wear bushing to the seal assembly.

5. A casing cutting and pulling assembly according to any preceding claim wherein the casing spear and casing cutter are located on the drill string below the running tool.

6. A casing cutting and pulling assembly according to any preceding claim wherein the assembly includes a tension-set retrievable packer, the casing spear being located between the mechanical tension-set retrievable packer and the casing cutter.

7. A method of cutting and pulling casing, the method comprising the steps:

(a) providing a casing cutting and pulling assembly according to claim 1 and locating the running tool of the modified wear bushing and seal assembly retrieval device, the casing spear and the casing cutter in order on a drill string wherein the running tool supports the modified wear bushing;

(b) running the drill string through the wellhead and into a wellbore;

(c) landing the modified wear bushing in the wellhead housing;

(f) cutting the casing;

8. A method of cutting and pulling casing according to claim 7 wherein the method includes the step of performing an integrity test on a plug in casing which is to be cut between steps (d) and (e).

9. A method of cutting and pulling casing according to claim 7 or claim 8 wherein the steps are performed on a single trip in the wellbore.

10. A method of cutting and pulling casing according to claim 7 or claim 8 wherein the method includes, between steps (d) and (g), the additional steps of:

switching the first latching mechanism between the first and second configurations with the assembly in the wellbore;

removing the casing cutting and pulling assembly with the running tool from the wellbore with both the modified wear bushing and the seal assembly left in the wellhead; and running the casing cutting and pulling assembly with the running tool into the wellbore and completing the method steps.

11. A method of cutting and pulling casing according to claim 7 or claim 8 wherein the modified wear bushing and seal assembly are selectably connectable downhole and the method includes, between steps (d) and (g), the additional steps of:

switching a second latching mechanism between third and fourth configurations with the assembly in the wellbore;

removing the casing cutting and pulling assembly with the running tool and the modified wear bushing from the wellbore with the seal assembly being left in the wellhead; and running the casing cutting and pulling assembly with the running tool and the modified wear bushing into the wellbore and completing the method steps.

12. A method of cutting and pulling casing according to claim 10 or claim 11, when depending from claim 8, wherein in the event that the integrity test fails, the method includes the additional steps of inserting a further plug and testing the integrity of the further plug.

13. A method of cutting and pulling casing according to any preceding claim wherein the method includes at step (a), releasably coupling the modified wear bushing to the running tool and by step (d) decoupling the modified wear bushing from the running tool.

14. A method of cutting and pulling casing according to any one of claims 7 to 13 wherein the method includes the step of rotating the drill string through the modified wear bushing to operate the casing cutter.

15. A method of cutting and pulling casing according to any one of claims 7 to 14 wherein step (e) includes actuating the casing spear to anchor the drill string to the casing in the well bore to hold the casing in tension during step (f).

16. A method of cutting and pulling casing according to any one of claims

8 to 15 wherein the method includes at step (a) locating a packer on the drill string below the running tool and using the packer to perform the integrity test.

17. A method of cutting and pulling casing according to any one of claims 7 to 16 wherein the method includes the step of performing a circulation test to determine circulation behind the cut tubular at surface.

18. A method of cutting and pulling casing according to any one of claims

7 to 17 wherein the method includes the further steps of pulling the drill string through the modified wear bushing when the modified wear bushing is in the wellhead housing to locate the casing cutter at a shallower depth in the casing and cutting the casing at the shallower depth.

19. A method of cutting and pulling casing according to claim 18 wherein the method includes repeating the circulation test and cutting casing at increasingly shallower depths until a positive circulation test occurs and a section of cut tubular can be removed from the wellbore.

20. A method of cutting and pulling casing according to any one of claims

9 to 19 wherein the method includes locating a drill bit on the end of the drill string and dressing off a cement plug in the casing on same trip.