WO2025083416A1

WO2025083416A1 - Method and downhole tool assembly for casing recovery and handling

Info

Publication number: WO2025083416A1
Application number: PCT/GB2024/052675
Authority: WO
Inventors: Michael Wardley
Original assignee: Ardyne Holdings Ltd
Current assignee: Ardyne Holdings Ltd
Priority date: 2023-10-19
Filing date: 2024-10-18
Publication date: 2025-04-24
Anticipated expiration: 2026-04-19
Also published as: GB202315986D0

Abstract

A method and downhole tool assembly (10) for recovering casing from a wellbore, the method comprising: for at least two cut pieces of the casing: gripping the cut piece of the casing with a respective one of a plurality of gripping arrangements (16, 18) of the downhole tool assembly (10), and applying a force to said cut piece of casing so as to dislodge the cut piece of casing from the wellbore; and pulling the downhole tool assembly (10) out of the wellbore to pull the at least two cut pieces of the casing out of the wellbore together. A downhole tool assembly (10) and a method of handling a cut piece of casing at a rig floor using the downhole tool assembly (10), the downhole tool assembly (10) comprising an upper portion (26) and a lower portion (28); the upper portion (26) and the lower portion (28) being releasably connectable; the upper portion (26) comprising a gripping arrangement (16) configured to grip a cut piece of casing, and a handling sub (24); and the handling sub (24) configurable in an extended configuration in which the handling sub (24) has a first outer diameter, and a retracted configuration in which the handling sub (24) has a second outer diameter smaller than the first outer diameter.

Description

METHOD AND DOWNHOLE TOOL ASSEMBLY FOR CASING RECOVERY AND HANDLING

FIELD

This relates to a method and downhole tool assembly for recovering casing from a wellbore. This further relates to a method and downhole tool assembly for handling casing at a rig floor.

BACKGROUND

There are occasions in oilfield operations, for instance during well abandonment, when it is desired to cut casing at a predetermined depth and pull the cut piece from the wellbore.

However, there are a number of technical challenges associated with the removal of casing.

For example, after many years in the wellbore, solids from the drilling mud can settle on the outside of the casing thereby increasing the force required to move the cut casing piece and often it is found that the cut casing piece is stuck and cannot be removed from the wellbore.

One of the options open to the operator is to make another cut in the cut piece of casing thereby producing two shorter pieces. Each shorter piece can be expected to have less resistance than the original single piece of cut casing. An attempt can then be made to recover the upper of the two pieces of cut casing, and if successful said upper piece of cut casing can be recovered to surface. A second trip back into the well can then be made to recover the lower piece of cut casing.

If, however, the process of attempting to pull the upper piece of cut casing is unsuccessful, another cut can be made to split the upper piece of cut casing into two even shorter pieces of cut casing.

This process can be repeated until the pulling force required to remove the upper piece of cut casing is within the capability of the available equipment. It will be appreciated the process described above can, however, result in several cut pieces in the wellbore at any one time, each of which must be individually recovered to surface and so requiring multiple trips into and out of the wellbore. It will be appreciated that each trip into and out of the wellbore involves significant time and cost to the operator. The recovery of multiple pieces of casing also increases the complexity of handling operations at surface, e.g. on the rig floor, with increase risk to personnel and equipment.

SUMMARY

Aspects of the present disclosure relate to a method and downhole tool assembly for recovering casing from a wellbore. Other aspects relate to a method and downhole tool assembly for handling casing at a rig floor.

In a first aspect, there is provided a method for recovering casing from a wellbore, the method comprising: for at least two cut pieces of the casing: gripping each of the cut pieces of the casing with a respective one of a plurality of gripping arrangements of a downhole tool assembly; and applying a force to said cut piece of casing so as to dislodge the cut piece of casing from the wellbore; and pulling the downhole tool assembly out of the wellbore to pull the at least two cut pieces of the casing out of the wellbore together.

Beneficially, the method may permit a plurality of cut pieces of casing to be removed from the wellbore during a single trip, or at least with a reduced number of trips into and out of the wellbore. It will be appreciated that each trip into the well and back out takes time and has potentially high costs associated with running a rig, therefore reducing the total number of trips into and out of the well reduces the time and therefore cost of the casing recovery operation.

Pulling the downhole tool assembly out of the wellbore may be performed by pulling a string, e.g. a tubing string, e.g. an intervention string, drill string or the like, coupled to the downhole tool assembly. The at least two cut pieces of the casing may comprise adjacent first, uphole, and second, downhole, cut pieces of the casing.

The method may comprise gripping and dislodging the first, uphole, cut piece of the casing and then gripping and dislodging the second, downhole, cut piece of the casing.

Each of the plurality of gripping arrangements may grip an uphole end of the respective cut piece of the casing.

The step of dislodging the respective cut piece of the casing from the wellbore may comprise using a dislodging arrangement.

The dislodging arrangement may comprise a downhole power tool, e.g. a jack.

The step of dislodging the respective cut piece of the casing from the wellbore may comprise anchoring the downhole tool assembly to the wellbore, e.g. to a liner, host casing or the like within the wellbore. The dislodging arrangement may be configured and/or operable to anchor the downhole tool assembly to the wellbore.

At least part of the dislodging arrangement, e.g. the downhole power tool, may be fluid e.g. hydraulically, operated and/or operable.

The step of dislodging the respective cut piece of the casing from the wellbore may comprise operating a valve of the dislodging arrangement, e.g. closing the valve.

Alternatively, the step of dislodging the respective cut piece of the casing from the wellbore may comprise pulling on the downhole tool assembly via a string.

The method may comprise the preliminary step of cutting the casing into the at least two cut pieces of the casing. The casing may be cut using a cutting arrangement of the downhole tool assembly.

The method may comprise a testing procedure to determine how many pieces the casing needs to be cut into in order for recovery from the wellbore to be achieved. The testing procedure may comprise iteratively attempting to dislodge a piece of the casing and cutting the piece of the casing, e.g. into two cut pieces, if the dislodging attempt fails, until all cut pieces of the casing are successfully dislodged. A cut piece of the casing may be pulled from the wellbore after being successfully dislodged. The testing procedure may be performed starting from an uphole end of the casing, so that each uphole cut piece of the casing may be dislodged before the adjacent downhole cut piece of the casing.

A plurality of cut pieces of the casing less than or corresponding to the number of the plurality of gripping arrangements may be pulled from the wellbore together.

Pulling the at least two cut pieces of the casing out of the wellbore together may comprise pulling the at least two cut pieces of the casing to a rig floor. The method may comprise removing the at least two cut pieces of the casing from the downhole tool assembly at the rig floor. Removing the at least two cut pieces of the casing from the downhole tool assembly at the rig floor may involve operation of a respective one of a plurality of handling subs of the downhole tool assembly. The handling sub may be located on the downhole tool assembly downhole of the respective gripping arrangement. Each handling sub may be spaced from the respective gripping arrangement on the downhole tool assembly such that it is downhole of the respective cut piece of the casing being gripped by the gripping arrangement.

In a second aspect there is provided a downhole tool assembly for recovering casing from a wellbore, the downhole tool assembly comprising: at least two gripping arrangements, each of the at least two gripping arrangements configured to grip a respective cut piece of the casing, so that pulling the downhole tool assembly out of the wellbore will pull the at least two cut pieces of the casing out of the wellbore together.

The downhole tool assembly may comprise and/or take the form of a bottom hole assembly (BHA).

The at least two gripping arrangements may comprise adjacent first and second gripping arrangements. In use, the first gripping arrangement may be an uphole gripping arrangement. In use, the second gripping arrangement may be a downhole gripping arrangement. The adjacent uphole and downhole gripping arrangements may be configured and/or operable to grip adjacent uphole and downhole cut pieces of the casing.

Each of the at least two gripping arrangements may comprise a grappling tool, a spear, an overshot or the like. The at least two gripping arrangements may be spaced apart in the downhole tool assembly. The downhole tool assembly may comprise one or more collar arrangements positioned between adjacent gripping arrangements of the at least two gripping arrangements.

The downhole tool assembly may comprise a dislodging tool configured to apply a force to the at least two cut pieces of the casing to dislodge each cut piece of the casing when gripped by the respective gripping arrangement. The dislodging tool may comprise a downhole power tool, e.g. a jack. The downhole power tool may be configured to apply a force to each cut piece of the casing when gripped by the respective gripping arrangement. The dislodging tool may comprise an anchoring arrangement. The anchoring arrangement may be configured to anchor the dislodging tool to the wellbore, e.g. to a wall, liner, host casing or the like of the wellbore. The dislodging tool may comprise a valve. The valve may be configured to operate the downhole power tool. The dislodging tool may be positioned in the downhole tool assembly such that in use it is uphole of the at least two gripping arrangements. The downhole tool assembly may comprise one or more collar arrangements positioned between the dislodging tool and the at least two gripping arrangements.

The downhole tool assembly may comprise a cutting arrangement. The cutting arrangement may be configured to cut the casing into the at least two cut pieces. The cutting arrangement may comprise a cutter, e.g. one or more blades. The cutting arrangement may comprise a motor. The motor may be configured to rotate the cutter. The cutting arrangement may be positioned in the downhole tool assembly such that in use it is downhole of the at least two gripping arrangements.

The downhole tool assembly may comprise a taper mill. The taper mill may be positioned at an end of the downhole tool assembly. In use, the taper mill may be positioned at a downhole end of the downhole tool assembly. The downhole tool assembly may comprise a handling sub associated with one of the gripping arrangements. The handling sub may be positioned on the downhole tool assembly such that in use it is downhole of the associated gripping arrangement. The handling sub may be positioned on the downhole tool assembly between adjacent gripping arrangements. The handling sub may be positioned on the downhole tool assembly between two collar arrangements. At least one of the collar arrangements may be positioned directly adjacent the respective end of the handling sub. The handling sub may be releasably connected to the directly adjacent collar arrangement distil the associated gripping arrangement. The handling sub may be configurable in an extended configuration in which the handling sub has a first outer diameter, and a retracted configuration in which the handling sub has a second outer diameter smaller than the first outer diameter. The handling sub may be configured to support a cut piece of casing in the extended configuration. The handling sub may comprise members, e.g. supports or arms, which can be arranged in the retracted configuration and the extended configuration. In the retracted configuration the members may be stowed. In the retracted configuration the members may extend axially, e.g. along the downhole tool assembly. In the retracted configuration the members may be generally flush with the adjacent collar arrangements. In the extended configuration the members may be deployed. In the extended configuration the members may extend radially outward. Reconfiguration between the retracted configuration and the extended configuration may be by manual operation, such as turning a screw which deploys the members.

In a third aspect, there is provided a downhole tool assembly comprising: an upper portion; and a lower portion; wherein the upper portion and the lower portion being releasably connectable, and wherein the upper portion comprises: a gripping arrangement configured to grip a cut piece of casing; and a handling sub, and wherein the handling sub is configurable in an extended configuration in which the handling sub has a first outer diameter, and a retracted configuration in which the handling sub has a second outer diameter smaller than the first outer diameter. In use, the downhole tool assembly is configured and/or operable to handle the cut piece of casing at the rig floor following a casing recovery operation. In use, the downhole tool assembly is configured and/or operable to facilitate removal of the cut piece of casing from the downhole tool assembly.

Beneficially, downhole tool assembly permits handling of the cut piece of casing at the rig floor following a casing recovery operation. This in turn permits the downhole tool assembly to provide safe handling procedures on the rig floor for a recovered casing piece, e.g. when a plurality of casing pieces are recovered in a single trip.

The first outer diameter may be larger than an inner diameter of the cut piece of casing. The second outer diameter may be smaller than the inner diameter of the cut piece of casing.

The handling sub may comprise members, e.g. supports or arms, which can be arranged in the retracted configuration and the extended configuration. In the retracted configuration the members may be stowed. In the retracted configuration the members may extend axially, e.g. along the downhole tool assembly. In the retracted configuration the members may be generally flush with the adjacent collar arrangements. In the extended configuration the members may be deployed. In the extended configuration the members may extend radially outward. Reconfiguration between the retracted configuration and the extended configuration may be by manual operation, such as turning a screw which deploys the members.

The gripping arrangement and the handling sub may be spaced apart such that in use the handling sub is below the cut piece of casing gripped by the gripping arrangement. The upper portion may comprise a collar arrangement between the gripping arrangement and the handling sub.

The lower portion may comprise a collar arrangement. The handling sub and the collar arrangement of the lower portion may be releasably connected. The lower portion may comprise a second gripping arrangement. The lower portion may comprise a cutting arrangement. The lower portion may comprise a taper mill.

The upper portion may comprise a dislodging tool. The upper portion may comprise a collar arrangement between the dislodging tool and the gripping arrangement. The upper portion may be connected to a string.

In a fourth aspect, there is provided a method of handling a cut piece of casing at a rig floor using the downhole tool assembly of the third aspect.

The method may comprise engaging the cut piece of casing with the handling sub in the extended configuration, and manoeuvring the downhole tool assembly to move the cut piece of casing.

Beneficially, use of the handling sub allows for safe handling of the cut piece of the casing.

The method may comprise at least one of: setting the cut piece of casing on the downhole tool assembly in a rig floor opening; configuring a handling sub of the upper portion of the downhole tool assembly below the cut piece of casing to an extended configuration having an outer diameter greater than an inner diameter of the cut piece of casing; manoeuvring the downhole tool assembly to engage the handling sub with the cut piece of casing and lift the cut piece of casing out of the rig floor opening; setting the lower portion of the downhole tool assembly in the rig floor opening; disconnecting the upper portion and the lower portion of the downhole tool assembly; reconfiguring the handling sub to a retracted configuration having an outer diameter smaller than an inner diameter of the cut piece of casing; and extracting the upper portion of the downhole tool assembly from the cut piece of casing. The steps of setting, configuring, manoeuvring, setting, disconnecting, reconfiguring and extracting may form, in a fifth aspect, a method of removing a cut piece of casing from a downhole tool assembly at a rig floor.

Setting the lower portion of the downhole tool assembly in the rig floor opening may comprise setting a collar arrangement of the lower portion in the rig floor opening. Disconnecting the upper portion and the lower portion may comprise disconnecting the handling sub and the collar arrangement.

The cut piece of casing may initially be gripped by a gripping arrangement of the downhole tool assembly. The griping arrangement may grip an upper end of the cut piece of casing. The gripping arrangement may for part of the upper portion. The gripping arrangement may be arranged above the handling sub. The gripping arrangement may be spaced from the handling sub so that the handling sub is below the cut piece of casing when the cut piece of casing is gripped by the gripping arrangement.

Setting the cut piece of casing in the rig floor opening may comprise manoeuvring the downhole tool assembly.

After setting the cut piece of casing in the rig floor opening, and before manoeuvring the downhole tool assembly to engage the handling sub, the method may comprise releasing the gripping arrangement from the cut piece of casing. The gripping arrangement may be release from the cut piece of casing by rotating or applying an impact to the gripping arrangement.

After disconnecting the handling sub and the collar arrangement, the method may comprise sitting the upper portion on the rig floor.

The method may comprise supporting the cut piece of collar arrangement with a line, e.g. a tugger line. This may facilitate reconfiguring the handling sub to the retracted configuration.

The invention is defined by the appended claims. However, for the purposes of the present disclosure it will be understood that any of the features defined above or described below may be utilised in isolation or in combination. For example, features described above in relation to one of the above aspects or below in relation to the detailed description below may be utilised in any other aspect, or together form a new aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of a downhole tool assembly for recovering casing from a wellbore;

Figures 2a to 2f shows steps in a method of recovering casing from a wellbore using the downhole tool assembly of Figure 1; and

Figures 3a to 3h show steps in a method of removing a cut piece of casing from the downhole tool assembly of Figure 1 at a rig floor.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows a downhole tool assembly 10 for recovering casing from a wellbore. The downhole tool assembly 10 may otherwise be referred to as a bottom hole assembly (BHA). In use, the downhole tool assembly 10 is connected to a rig by a tubing string 12, e.g. an intervention string, drill string or the like. The downhole tool assembly 10 is configured to be connected to the tubing string 12 at an end of the downhole tool assembly 10, e.g. an uphole end 14 of the downhole tool assembly 10. The downhole tool assembly 10 can be manoeuvred in and out of the wellbore via the tubing string 12.

The downhole tool assembly 10 comprises two gripping arrangements 16, 18, each configured to grip a respective cut piece of the casing, so that pulling the downhole tool assembly 10 out of the wellbore via the string will pull at least two cut pieces of the casing out of the wellbore together. The two gripping arrangements 16, 18 are spaced apart in the downhole tool assembly 10. Of the two gripping arrangements 16, 18, one is an uphole gripping arrangement 16 and the other is a downhole gripping arrangement 18, e.g. in use one of the gripping arrangements 16 will be located on the downhole tool assembly in a respective uphole position and the other gripping arrangement 18 will be located on the downhole tool assembly in a respective downhole position. The uphole and downhole gripping arrangements 16, 18 are configured to grip respective adjacent uphole and downhole pieces of casing. Each of the gripping arrangements 16, 18 comprises a spear. The downhole tool assembly 10 comprises a first collar arrangement 20 and a second collar arrangement 22 between the gripping arrangements 16, 18. The first collar arrangement 20 is proximal the uphole gripping arrangement 16. The second collar arrangement 22 is proximal the downhole gripping arrangement 18.

The downhole tool assembly 10 comprises a handling sub 24, e.g. a secure sub, associated with the uphole gripping arrangement 16. The handling sub 24 is positioned on the downhole tool assembly 10 such that in use it is downhole of the uphole gripping arrangement 16. The handling sub 24 is positioned on the downhole tool assembly 10 between the uphole and downhole gripping arrangements 16, 18. The handling sub 24 is positioned on the downhole tool assembly 10 between the first and second collar arrangements 20, 22. The first collar arrangement 20 is positioned directly adjacent one end of the handling sub 24. The second collar arrangement 22 is positioned directly adjacent the other end of the handling sub 24. The handling sub 24 is releasably connected to the second collar arrangement 22. In this way, the downhole tool assembly can be split into an upper portion 26 and a lower portion 28. The handling sub 24 is configurable in an extended configuration in which the handling sub 24 has a first outer diameter, and a retracted configuration in which the handling sub 24 has a second outer diameter smaller than the first outer diameter. The handling sub 24 is configured to support a cut piece of casing in the extended configuration, as discussed in more detail below with regard to Figures 3a to 3h.

The downhole tool assembly 10 comprises a dislodging tool 30 configured to dislodge each piece of casing from the wellbore when gripped by the respective gripping arrangement 16, 18. The dislodging tool 30 comprises a downhole power tool 32, e.g. a jack. The downhole power tool 32 is configured to apply a force to each piece of the casing when gripped by the respective gripping arrangement 16, 18. The dislodging tool 30 comprises an anchoring arrangement 34 (see Figure 2b). The anchoring arrangement 34 is configured to anchor the dislodging tool 30 to the wellbore, e.g. to a host casing of the wellbore. The dislodging tool 30 comprises a valve 36. The valve 36 is configured to operate the downhole power tool 32. The dislodging tool 30 is positioned in the downhole tool assembly 10 such that in use it is uphole of the two gripping arrangements 16, 18. The dislodging tool 30 is arranged proximal the end 14 of the downhole tool assembly 10 configured to be connected to the tubing string 12. The downhole tool assembly 10 comprises a third collar arrangement 38 positioned between the dislodging tool 30 and the two gripping arrangements 16, 18, e.g. between the dislodging tool 30 and the uphole gripping arrangement 16.

The downhole tool assembly 10 comprises a cutting arrangement 40. The cutting arrangement 40 is configured to cut the casing to be removed from the wellbore into cut pieces of casing. The cutting arrangement 40 comprises a cutter 42, e.g. comprising a blade. The cutting arrangement 40 comprises a motor 44. The motor 44 is configured to rotate the cutter 42 when it is desired to cut the casing. The cutting arrangement 40 is positioned in the downhole tool assembly 10 such that in use it is downhole of the two gripping arrangements 16, 18. The cutting arrangement 40 is arranged distal the end 14 of the downhole tool assembly 10 configured to be connected to the tubing string 12. The two gripping arrangement 16, 18 are arranged in the downhole tool assembly 10 between the dislodging tool 30 and the cutting arrangement 40.

The downhole tool assembly 10 comprises a taper mill 48. The taper mill 48 is positioned at an end 50 of the downhole tool assembly 10 opposite the end 14 configured to be connected to the tubing string 12. In use, the taper mill 48 is positioned at a downhole end 50 of the downhole tool assembly 10. The taper mill (48) guides the BHA 10 during the trip into the well.

It may be appreciated that there are many alternative BHA’s that may be used; for instance, the motor may be omitted and the casing cutter may be operated by rotating the string, or the jack may be omitted and the casing pulled by applying force from surface via rig equipment.

By way of example, referring to Figure 1, a BHA is prepared to be run into a wellbore. Figures 2a to 2f show a method for recovering casing 52 from a wellbore using the downhole tool assembly 10 of Figure 1.

Figure 2a shows the BHA (10) deployed in the wellbore and located at a point where a cut in the casing is to be made. The cutter 42 is operated by pumping fluid through the tubing string 12 and BHA 10 to turn the motor 44 and deploy the cutter blade. In Figure 2b, the tubing string 12 is lifted until the downhole gripping arrangement 18 is positioned near the top, e.g. uphole end, of the casing 52. The downhole gripping arrangement 18 is used to grip the casing 52. The anchoring arrangement 34 of the dislodging tool 30 then grips the host casing 54 to anchor the dislodging tool 30 to the wellbore. The valve 36 is then closed. Applying pressure into the tubing string 12 now activates the jack 32 of the deploying tool 30 and an upward force is applied to the casing 52. If the force is enough to dislodge the casing 52 then it is recovered to surface in a normal fashion, e.g. by recovering the downhole tool assembly 10 to surface with the casing 52 attached thereto via the gripping arrangement 18. However, if it is not possible to dislodge the casing 52, then a second cut needs to be made as further explained below.

The attempt at dislodging the casing 52 forms a testing procedure to determine how many pieces the casing 52 needs to be cut into for recovery from the wellbore. The testing procedure comprises iteratively attempting to dislodge a piece of the casing and cutting the piece of the casing, e.g. into two cut pieces, if the dislodging attempt fails, until all cut pieces of the casing are successfully dislodged. A cut piece of the casing can be pulled from the wellbore after being successfully dislodged. The testing procedure is performed starting from an uphole end of the casing 52, so that each uphole cut piece of the casing is dislodged before an adjacent downhole cut piece of the casing.

Figure 2c shows the second cut being made in between the top, e.g. uphole end, of the casing 52 and the first cut, so that the casing to be recovered is now in two cut pieces; an upper, e.g. uphole, piece 52a and a lower, e.g. downhole, piece 52b. Under normal circumstances, an attempt would be made to recover the upper piece 52a and, if successful, the tubing string 12 along with the upper piece 52a would be recovered to surface. The tubing string 12 would then be tripped back into the wellbore to recover the lower piece 52b. However, according to the present disclosure, in Figure 2d the uphole gripping arrangement 16 is engaged with the upper piece 52a, the jack 32 is activated as afore described and the upper piece 52a is dislodged from the wellbore.

In Figure 2e the tubing string 12 is raised until the downhole gripping arrangement 18 is near the top, e.g. uphole end, of the lower piece 52b, at which point it is engaged to grip the lower piece 52b. The jack 32 is then activated as afore described to dislodge the lower piece 52b from the wellbore. If successful, the tubing string 12 is recovered to surface with the two cut pieces of casing 52a, 52b as shown in Figure 2f to pull the first piece of cut casing 52a and the second piece of cut casing 52b out of the wellbore together.

If it is not possible to dislodge the lower piece 52b then the downhole gripping arrangement 18 is disengaged and the tubing string 12 recovered with just the upper piece 52a. As per the testing procedure, a separate trip would then be made to cut the lower piece 52b into still shorter pieces and retrieve two cut pieces in a single trip where possible.

It may be appreciated that the BHA 10 could include a third gripping arrangement, and an associated second handling sub, and the casing could be cut into three pieces and all three recovered in the same trip and so on. to the downhole tool assembly 10 can also provide safe rig handling of a recovered casing piece on a rig floor 56, e.g. a drill floor. Safe rig handling of the casing piece 52a may be achieved by use of the handling sub 24, e.g. the ‘secure sub’. The handling sub 24 is a tool which is used to safely handle the casing piece 52a when it is received at the drill floor 56. The handling sub 24 is positioned in the BHA 10 below the point at which the lower end of the upper casing piece 52a reaches after the uphole gripping arrangement 16 has engaged it, e.g. the distance between the gripping arrangement 16 and the handling sub 24 is at least the length of the cut piece of casing 52a being retrieved. The handling sub 24 has no function until a casing piece 2a is received at the drill floor 56 and is dormant during all downhole operations.

The handling sub 24 comprises members 58, e.g. supports or arms, which can be arranged in the retracted configuration and the extended configuration. In the retracted configuration the members 58 are stowed. In the retracted configuration the members 58 extend axially. In the retracted configuration the members 58 are generally flush with the adjacent collar arrangements 20, 22. In the retracted configuration, the outer diameter of the handling sub 24 is smaller than the inside diameter of the casing 52a. In the extended configuration the members 58 are deployed. In the extended configuration the members 58 extend radially outward. In the extended configuration, the outer diameter of the handling sub 24 is larger than the inside diameter of the casing. Reconfiguration between the retracted configuration and the extended configuration may be by manual operation, such as turning a screw which deploys the members 58.

Figure 3 shows a cut casing piece 52a supported by the uphole gripping arrangement 16 and received at the drill floor 56. The handling sub 24 is positioned below the lower end of the casing piece 52a. A tugger line 60 is attached to the casing piece 52a to provide additional support and remains attached until after the casing piece 52a has been removed from the rig floor 56.

The string 12 is lifted, e.g. by a top drive, as shown in Figure 3b. The string 12 is lifted until the cut casing piece 52a and the handling sub 24 are above the rig floor 56. The members 58 of the handling sub 24 are deployed so that the members 58 extend radially outward, e.g. the handling sub 24 is reconfigured from the retracted configuration to the extended configuration.

In Figure 3c, the string 12 is lowered until the casing piece 52a can be set in a first set of slips 62a in an opening in the drill floor 56 and supported at the drill floor 56.

The gripping arrangement 16 is now disengaged from the cut piece of casing 52a, for instance by further lowering the string 12 as shown in Figure 3d. As the string 12 is further lowered, the cut piece of casing 52a remains stationary due to the support provided by the slips 62 and the rig floor 56.

The string 12 is now lifted relative to the cut casing piece 52a until the handling sub 24 reaches the bottom of the cut casing piece 52a and engages the bottom of the cut casing piece 52a. Continued lifting raises the cut casing piece 52a above the rig floor 56, supported by the handling sub 24. The lower portion 28 of the downhole tool assembly 10, e.g. the second collar arrangement 22, is now set in a second set of slips 62b, e.g. larger slips, at the rig floor 56 as shown in Figure 3e.

Figure 3f shows the connection between the upper portion 26 and the lower portion 28 of the downhole tool assembly 10being disengaged. The handling sub 24 is lowered to the rig floor 56, the cut casing piece 52a lifted with the tugger line 60 off the handling sub 24, and the handling sub arms 58 are retracted as shown in Figure 3g, e.g. the handling sub 24 is reconfigured from the extended configuration to the retracted configuration. The upper portion 26 of the downhole tool arrangement 10, e.g. the gripping arrangement 16, collar arrangement 20 and handling sub 24, can now be withdrawn from the casing piece 52a by lifting via the string 12 as shown in Figure 3h and racked back in the derrick. A second tugger line 64 can now be attached to the casing piece 52a, which can now be removed from the rig floor 56.

Claims

CLAIMS:

1. A method for recovering casing from a wellbore, the method comprising: for at least two cut pieces of the casing: gripping the cut pieces of the casing with a respective one of a plurality of gripping arrangements of a downhole tool assembly, and applying a force to said cut piece of casing so as to dislodge the cut piece of casing from the wellbore; and pulling the downhole tool assembly out of the wellbore to pull the at least two cut pieces of the casing out of the wellbore together.

2. The method of claim 1 , further comprising cutting the casing into the at least two cut pieces of the casing.

3. The method of claim 1 or 2, wherein each of the plurality of gripping arrangements grips an uphole end of the respective cut piece of the casing.

4. The method of any preceding claim, wherein the step of dislodging the respective cut piece of the casing from the wellbore comprise: anchoring the downhole tool assembly to the wellbore, and operating a valve of a dislodging arrangement.

5. The method of any preceding claim, further comprising a testing procedure to determine how many pieces the casing needs to be cut into for recovery from the wellbore, wherein the testing procedure comprises iteratively attempting to dislodge a piece of the casing and cutting the piece of the casing if the dislodging attempt fails, until all cut pieces of the casing are successfully dislodged.

6. The method of claim 5, wherein the testing procedure is performed starting from an uphole end of the casing, so that each uphole cut piece of the casing is dislodged before an adjacent downhole cut piece of the casing.

7. A downhole tool assembly for recovering casing from a wellbore, the downhole tool assembly comprising: at least two gripping arrangements, each of the at least two cutting arrangements configured to grip a respective cut piece of the casing, so that pulling the downhole tool assembly out of the wellbore will pull at least two cut pieces of the casing out of the wellbore together.

8. The downhole tool assembly of claim 7, further comprising a dislodging tool configured to apply a force to each cut piece of the casing to dislodge said cut piece of the casing when gripped by the respective gripping arrangement.

9. The downhole tool assembly of claim 7 or 8, further comprising a cutting arrangement configured to cut the casing into the at least two cut pieces.

10. The downhole tool assembly of any of claims 7 to 9, further comprising a handling sub associated with one of the gripping arrangements.

11. The downhole tool assembly of claim 10, wherein the at least two gripping arrangements are spaced apart in the downhole tool assembly, wherein the downhole tool assembly comprise two collar arrangements positioned between adjacent gripping arrangements of the at least two gripping arrangements, and wherein the handling sub is positioned between the collar arrangements.

12. The downhole tool assembly of claim 10 or 11 , wherein the handling sub is configurable in an extended configuration in which the handling sub has a first outer diameter, and a retracted configuration in which the handling sub has a second outer diameter smaller than the first outer diameter.

13. A downhole tool assembly comprising: an upper portion; and a lower portion, wherein the upper portion and the lower portion are releasably connectable; wherein the upper portion comprises: a gripping arrangement configured to grip a cut piece of casing; and a handling sub, and wherein the handling sub is configurable in an extended configuration in which the handling sub has a first outer diameter, and a retracted configuration in which the handling sub has a second outer diameter smaller than the first outer diameter.

14. The downhole tool assembly of claim 13, wherein the handling sub comprises members which can be arranged extending axially in the retracted configuration and extending radially in the extended configuration.

15. The downhole tool assembly of claim 13 or 14, wherein the upper portion comprises a collar arrangement between the gripping arrangement and the handling sub so that the gripping arrangement and the handling sub are spaced apart.

16. The downhole tool assembly or claims 13, 14 or 15, wherein the lower portion comprises a collar arrangement, and the handling sub and the collar arrangement of the lower portion are releasably connectable.

17. The downhole tool assembly of any of claims 13 to 16, wherein the lower portion comprises at least one of: a second gripping arrangement, a cutting arrangement, and a taper mill.

18. The downhole tool assembly of any of claims 13 to 17, wherein the upper portion comprises a dislodging tool.

19. A method of handling a cut piece of casing at a rig floor using the downhole tool assembly of any of claims 13 to 18.

20. The method of claim 19, comprising at least one of: setting the cut piece of casing on the downhole tool assembly in a rig floor opening; configuring a handling sub of the upper portion of the downhole tool assembly below the cut piece of casing to an extended configuration having an outer diameter greater than an inner diameter of the cut piece of casing; manoeuvring the downhole tool assembly to engage the handling sub with the cut piece of casing and lift the cut piece of casing out of the rig floor opening; setting the lower portion of the downhole tool assembly in the rig floor opening; disconnecting the upper portion and the lower portion of the downhole tool assembly; reconfiguring the handling sub to a retracted configuration having an outer diameter smaller than an inner diameter of the cut piece of casing; and extracting the upper portion of the downhole tool assembly from the cut piece of casing.