Improvements in or relating to well abandonment

Abstract

Method and apparatus for removing a section of well tubing. A bridge plug is located in the well tubing. A first bottom hole assembly comprising a cutting tool and a swivel sub is run-in and landed on the bridge plug and the well tubing is cut to provide a depth reference in this weight set configuration. A second bottom hole assembly comprising a tubing removal tool such as a milling tool is then run in and is landed on the bridge plug to use the depth reference to locate the cut position on any re-entry into the well. Embodiments have a combined cutting and tubing removal tool to create a window on running the first string which can be located for further operations when the strings are of coiled tubing or narrow drill pipe; and the first and second bottom hole assemblies may be identical.

Description

[0001] IMPROVEMENTS IN OR RELATING TO WELL ABANDONMENT

[0002] FIELD

[0003] The present invention relates to methods and apparatus for well abandonment and in particular, though not exclusively, to a method and apparatus for removing a section of tubular across a longitudinal section of the well to enable the placement of a cement plug.

[0004] BACKGROUND

[0005] 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 practice to create a cement plug over a predetermined length of the well. As a well is constructed by locating conduits such as casing, liner, pipe and tubing (herein collectively referred to as tubulars) into the well, the cement plug must extend over all annuli present in the well. In many cases, all inner conduits are removed leaving the outer casing, including the annulus bounded by the formation.

[0006] The integrity of the casing and in particular, the cement in an annulus will determine if a cement plug can just be located in the tubular. Steel casing can leak at the connections or corrode from acids. Cement can deteriorate with time too, but leaks also happen when cement shrinks, develops cracks or channels, or is lost into the surrounding rock when applied. If integrity fails, gases and liquids can leak out of the casing or, just as importantly, move into, up, and out of the well through faulty cement between the casing and the rock wall. These issues affect the ability to plug a well for abandonment but also for ensuring zonal isolation in unconventional reservoirs. Cement bond logging (CBL) can be used to log the quality of the cement bond but if the CBL shows the bond to be poor, intervention is required with access needed to the outermost tubular.

[0007] One method of creating or repairing the cement plug is to mill away the inner tubular to expose the annulus behind the tubular and then pump cement into the enlarged area to create the cement plug. This is achieved using a rotatable section mill run on a work string and typically operated downwardly to remove the tubular section. In milling downwardly, the weight of the work string, is used to apply downward force to the section mill to cause it to progress through the tubular being milled. This application of force to the mill by weight applied from above creates a wobble in the milling work string, which has a tendency to fracture the cutting inserts on the section mill blades. This, in turn, causes the mill to wear out sooner, resulting in the removal of less tubular footage before replacement of the mill is required. Further, since milling progresses downwardly, cuttings must be removed from the well bore as they are formed, to avoid forming a ball of cuttings around the mill and reducing its effectiveness. Specialized formulation of milling fluid, and maintenance of proper fluid flow rates, are required in order to circulate the cuttings out of the hole.

[0008] To overcome these disadvantages, an alternative method has been developed which perforates the tubular and pumps cement through the perforations to travel up the annulus and thereby create a plug within the annulus. This ‘perf and plug’ arrangement, sometimes referred to as cement squeeze, has disadvantages in that by forcing the cement through narrow apertures there is no guarantee that the cement fully contacts the surrounding formation as the cement may not reach all areas in the annulus. As a result, the cement plug may be compromised and rendered at least partially ineffective. This method does provide a major advantage in that it can be performed from a floating vessel or semi-submersible to offer what is referred to as a ‘rigless’ method of abandonment. By removing the requirement for a drilling rig, significant time and therefore costs can be made in the well abandonment procedure. In the rigless method the work string is anchored to the tubular and as such sea swell will place tension and / or weight on the work string. Even with the use of heave compensators, this variable load means that a section mill, reliant on using controlled weight to operate, cannot be used.

[0009] GB2565804 describes a section mill and method of removing a section of tubular from a well. The section mill includes elongate blades which have a cutting structure extending along at least a portion of a length from a first edge and at least a portion of a width from a second edge of the elongate cutter blade, the second edge being longer than the first edge, the first and second edges being perpendicular to each other. The blades are moved axially and radially relative to the tubular body to arrange the second edge parallel to the central longitudinal axis for milling. Operation of the mill is in an upwards direction using a hydraulic tensioning device to provide a constant load so that milling of tubular can be achieved in a rigless arrangement. A suitable hydraulic tensioning device is described in GB2567157 which maintains a constant load on the section mill so that long sections of tubing can be removed in a near continuous procedure on a single trip into the well in a rigless well abandonment procedure.

[0010] A difficulty in milling of tubular in a rigless procedure is in repositioning the section mill at the milled window when the tool string is retrieved to change the blades or provide other operations on the string. Locating the section mill back at the window is difficult when the bottom hole assembly is deployed on coiled tubing or small diameter drill pipe due to stretch or compression experienced in the running string.

[0011] SUMMARY

[0012] Aspects of the present disclosure relate to methods and apparatus for well abandonment and in particular, though not exclusively, to a method and apparatus for removing a section of tubular across a longitudinal section of the well to enable the placement of a cement plug.

[0013] According to a first aspect, there is provided a method of removing a section of well tubing, comprising the steps:

[0014] (a) locating a bridge plug in the well tubing;

[0015] (b) providing a first string with a first bottom hole assembly comprising a cutting tool and a swivel sub;

[0016] (c) running the first string into the well tubing and landing the first bottom hole assembly on the bridge plug;

[0017] (d) cutting the well tubing with the first bottom hole assembly landed on the bridge plug to thereby provide a depth reference;

[0018] (e) running in a second string and landing a second bottom hole assembly comprising a tubing removal tool on the bridge plug to obtain the depth reference;

[0019] (f) positioning the tubing removal tool in the well tubing by relation to the depth reference; and

[0020] (g) using the tubing removal tool to remove a section of the well tubing.

[0021] In this way, by landing a bottom hole assembly on the bridge plug when further strings are run in the tubular a depth reference is provided in the well to return to the location of the cut. Thus, when a window is cut in the tubing its position is known and subsequent runs into the tubular can locate it for the purpose of milling the tubular.

[0022] Beneficially, the method obviates or mitigates at least some of the disadvantages of the prior art. Alternatively or additionally, the method provides a method of removal of a section of well tubing which provides depth control.

[0023] Step(d) may be performed by the cutting tool being operated via rotation by a motor and rotating the cutting tool on the swivel sub. The motor may be at surface and rotation of the cutting tool is via rotation of the first string. The motor may be in the first bottom hole assembly. The cutting tool may be located between the motor and the swivel sub. More particularly, the swivel sub may be at an end of the first bottom hole assembly and may be landed on the plug.

[0024] The cutting tool may comprise one or more blades to cut the well tubing on first contact of the one or more blades with the tubing.

[0025] The tubing removal tool may be a milling tool. In this way a section mill can be used to remove the section of well tubing by milling.

[0026] The first bottom hole assembly may further comprise a tubing removal tool to open up a window in the well tubing once the cutting tool has cut the well tubing. The method may include creating a window in the well tubing at step (d).

[0027] Step (g) may be performed by the tubing removal tool being operated via rotation by a motor. The motor may be at surface and rotation of the tubing removal tool is via rotation of the second string.

[0028] Step (g) may be performed by raising the second string so that milling is performed in an uphole direction. More particularly, the second bottom hole assembly may include a hydraulic tensioning device to maintain a constant load on the tubing removal tool as it is raised.

[0029] In an embodiment, the cutting tool and tubing removal tool are combined wherein, the one or more blades include a cutting edge and a milling surface. In this way, the first bottom hole assembly can open up a window in the well tubing. More particularly, by combining the cutting tool and tubing removal tool, the second bottom hole assembly and first bottom hole assembly may be identical. This allows only a replacement of the one or more blades between running the first string and the second string.

[0030] The bridge plug may be located on the first bottom hole assembly and step (a) may be performed after step (b) on the same run in the well tubing. This reduces the number of trips into the well. The second bottom hole assembly may also comprise a swivel. In this way, when the second string is landed no damage can occur if the string is being rotated. The well tubing may typically be liner or production tubing. The well tubing has a diameter of 7” (178mm) or less. In an embodiment, the well tubing has a diameter of 4.5” (114mm). The first string and the second string may be coiled tubing or drill pipe. The drill pipe will be of small diameter to be run in the well tubing.

[0031] The method may include the step of creating a cement plug over the milled section of well tubing.

[0032] According to a second aspect, there is provided apparatus for removing a section of well tubing comprising: a tubular string supporting a bottom hole assembly suspended therefrom; the bottom hole assembly comprising, in order from the string: a combined cutting and tubing removal tool; and a swivel, wherein: the swivel is configured to allow rotation of the combined cutting and tubing removal tool when the string is landed on a plug in the well tubing.

[0033] In this way, as the combined cutting and tubing removal tool can rotate relative to a lower end of the swivel sub, the string can be put in compression to make a cut.

[0034] Beneficially, the apparatus obviates or mitigates at least some of the disadvantages of the prior art. Alternatively or additionally, the apparatus obviates or mitigates at least some of the disadvantages of the prior art. Alternatively or additionally, the apparatus provides an apparatus for removal of a section of well tubing which provides depth control.

[0035] The combined cutting and tubing removal tool may comprise a plurality of blades, each blade having a cutting edge to form a circumferential cut in the well tubing and a milling surface to mill the well tubing when rotated. This provides the dual functions cutting and milling on a single tool. The blades may be moveable between a retracted configuration where they sit inside a body of the tool and an extended configuration where they extend radially outwards from the body for use.

[0036] The bottom hole assembly may comprise a tensioning device, the tensioning device configured to apply a constant load on the combined cutting and tubing removal tool when the blades are in the extended configuration. The bottom hole assembly may comprise a motor. In this way, the combined cutting and tubing removal tool can be rotated in the bottom hole assembly independently of rotation of the string. The combined cutting and tubing removal tool will rotate between the motor and the swivel. The motor may be a left hand positive displacement motor. This prevents potential unwinding of the tubular during rotation.

[0037] The tubular string may be coiled tubing. Alternatively, the tubular string may be drill pipe. More particularly, the tubular string may have a diameter of less than 7” (178mm). In an embodiment, the tubular string may have a diameter of less than 4.5” (114mm).

[0038] In the description that follows, the drawings are not necessarily to scale. Certain features 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.

[0039] 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.

[0040] 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 may be utilised in any other aspect, or together form a new aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which:

[0042] Figures 1(a) and 1(b) are schematic illustrations of first steps in a method for removing a section of well tubing, according to an embodiment of the present invention;

[0043] Figures 2(a), 2b and 2(c) are schematic illustrations of further steps in a method for removing a section of well tubing, according to an embodiment of the present invention; and

[0044] Figures 3(a), 3(b) and 3(c) are schematic illustrations of further steps in a method for removing a section of well tubing, according to a further embodiment of the present invention.

[0045] DETAILED DESCRIPTION OF THE DRAWINGS

[0046] Referring initially to Figure 1(a) of the drawings there is illustrated a well tubing, generally indicated by reference numeral 10, located in a well 12 in which a section 20 of the well tubing 10 is to be removed, according to an embodiment of the present invention. The well tubing 10 is typically a liner or production tubing having a diameter of 7” (178mm) or less, with a diameter of 4.5” (114mm) for this embodiment. In this example the well tubing 10 is located within an outer tubular 14, such as liner or casing. It will be realised that there need not be an outer tubular 14 and the well tubing 10 can be the only tubular and may be cemented in place. Within the well tubing 10 at a location below the section 20 to be removed is a plug 30. Plug 30 is a bridge plug as is known in the art and provides a seal across the bore of the well tubing 10.

[0047] A first tubing string 16 is run in the well tubing 10. The first tubing string 16 is formed of coiled tubing or small diameter drill pipe. The first tubing string 16 can be run from a floating vessel to make the intervention rigless for a subsea well 12. The method finds equal application for land based wells and wells serviced by a rig. The first tubing string 16 supports a first bottom hole assembly 18. Located in the first bottom hole assembly 18 are a cutting tool 22 and a swivel sub 24. The swivel sub 24, sometimes referred to as a downhole swivel joint, is as known in the art to allow one end of the sub 24 to rotate relative to a second end which is held static. The cutting tool 22 may be any cutting tool 22 which operates by cutting blades 26 extending from the tool body 28 with cutting edges 32 on the blades 26 contacting the inner surface 34 of the well tubing 10 to provide a circumferential cut 36 through the well tubing 10 when the cutting tool 22 is rotated. In the method, the first tubing string 16 is run into the well 12 until the swivel sub 24, located at the distal end 38 of the first bottom hole assembly 18 is landed on the plug 30. In landing on the plug 30 weight is set down on the first tubing string 16. This effectively compresses the coiled tubing or drill pipe of the first tubing string 16 to remove any stretch caused by the weight of the first bottom hole assembly 18 when run-in. The end of the swivel 24 at the plug 30 will be held static by the weight of the first bottom hole assembly 18 and the first tubing string 16.

[0048] The cutting tool 22 is then operated to extend the cutting blades 26 and create a cut 36 through the well tubing 10. To create the cut 36, the cutting tool 22 is rotated either by rotating the first tubing string 16 from surface or by use of a motor 40 located above the cutting tool 22 in the first bottom hole assembly 18. In the illustrated method and apparatus, the motor 40 is a fluid driven left hand positive displacement motor. The swivel 24 facilitates rotation of the cutting tool 22 while remaining in the weight set or landed configuration. The cut 36 provides a depth reference 42 in the well tubing 10, by virtue of the set distance between the plug 30 and the cut 36 which matches the distance between the cutting blades 26 and the end 38 of the first bottom hole assembly 18. Accordingly, any string run into the well tubing 10 and landed on the plug 30, will be able to determine the position of the depth reference 42 and find the cut 36.

[0049] In the embodiment shown, the cutting tool 22 is combined with a milling tool to provide a dual action section mill 44. The section mill 44 is as described in GB2565804 and is incorporated herein by reference. The section mill has a tubular body and includes elongate blades 26 which have a cutting structure 48 extending along at least a portion of a length from a first edge 50 and at least a portion of a width from a second edge 52 of the elongate cutter blade 26. The blades 26 are moved by an actuator axially and radially relative to the tubular body between first retracted and second extended positions, in each of which the blade second edge is parallel to a longitudinal axis of the device. The tubular body can have a cam body profile on an inner surface which engages a profile on the cutting blade 26 to provide radial movement when the cutting blade 26 is moved axially by e.g. a piston. The body profile has a ramp to cause tilting of the cutting blade 26 at a third blade position, so that blade apex 54 provides the cutting edge 32.

[0050] When first actuated, by fluid flow through the bore of the first tubing string 16, the retracted blades 26 are caused to tilt to the third blade position so as to provide the cutting edge 32. This is as shown in Figure 1(a) and provides the depth reference 42 as described hereinbefore. Continued fluid pumping will cause the blades 26 to fully extend with the second edge 52 parallel to the longitudinal axis of the mill 44 and first tubing string 16. The cutting structure 48 on the blades 26 provides a milling action to mill the well tubing 10 and create a window 46. This is as shown in Figure 1(b).

[0051] At this stage, the first tubing string 16 can be removed if a dedicated milling tool 56 is to be run in to mill and remove the section 20 of well tubing 10. If this is the case, then a second string 58 is run in the well 12 and landed on the bridge plug 30. The second bottom hole assembly 60 on the second string 58 includes the milling tool 56. The milling tool 56 is shown in combination with a hydraulic tensioning device, being an up-thruster tool 62, an anti-torque tool 64, a motor 40 and the swivel sub 24 in the second bottom hole assembly 60 at Figure 2(a). When landed on the plug 30, the distance up the second bottom hole assembly 60 from the distal end 66 on the plug 30 to the blades 68 on the milling tool 56 is spaced to match the depth reference 42, so that when the blades 68 on the milling tool 56 open out, typically on a pivot, they will be within the window 46 at a known distance relative to the depth reference 42. In this way, the depth reference 42 ensures that the cut 36 and window 46 position can be found on repeated entry to the well 10.

[0052] The milling tool 56 is now positioned at the lower end of the interval where a section 20 of well tubing 10 is to be cut. Typically, the components of the second bottom hole assembly 60 are arranged with the milling tool 56 above the swivel 24 at the bottom, with a stabilizer 70, the up-thruster 62, the mud motor 40, and an anti-torque anchor 64 positioned above that, in order.

[0053] The up-thruster 62 may be as disclosed in US 6,679,329 and can be considered as a hydraulic tensioning device. US 6,679,329 is incorporated herein by reference. The purpose of the device 62 is to supply a constant upward load on the milling tool 56 so that upward milling is performed. If a mud motor 40 were used to drive the mill 56 without the device 62, the loading imparted by the work string operated from a floating vessel to lift the mill 56 and cut into the well tubing 10, would be too erratic. The operator would have to be extremely careful not to overload the mill 56, otherwise the mud motor 40 would stall out. The device 62 is a hydraulic cylinder pressurized by the mud flow which is pumped through a fluid flow path in the anti-torque anchor 64, the mud motor 40, the device 62, and on down through the milling tool 56. Drilling mud passes through the milling tool 56 below the up-thruster 62, to operate the mill 56. When the mill needs to be moved upwards a flow restriction creates a back pressure in the second bottom hole assembly 60. This back pressure is used to cause the device 62 to lift upwardly on the milling tool 56. With a tensioning device 62 in the assembly 60, the pump pressure can be controlled in such a fashion that loading on the mill 56 is very constant, and loading can be imparted with much more precision.

[0054] In use, the anti-torque anchor 64 is set against the inner surface 34 of the well tubing 10 as the milling fluid pressure is increased, which also starts the mud motor 40 running and exerts an upward force on the milling tool 56 with the device 62. Rotation of the second bottom hole assembly 60 when is facilitated in the landed position by rotation in the swivel 24. Fluid pressure operates the blades 68 and the milling tool 56 is rotated by the downhole motor 40. The torque anchor 64, mud motor 40, tensioning device 62, stabilizer 70, and milling tool 56 can have the sizes and shapes of their fluid flow paths designed to initiate their respective operations at selected progressive pressure levels, to insure the desired sequence of activation of the various tools. Additionally, the motor 40 can be designed to bypass fluid before it begins to rotate. As a result, the blades 58 extend, then the torque anchor blades 64 contact the well tubing 10, then the mud motor 40 begins to rotate, and finally, the device 62 begins to lift the milling tool 56. Blades 68 will mill the lower end 72 as the device 62 moves the section mill 10 upwards. Milling will continue until the device 62 reaches its full travel, or "bottoms out". A pressure drop will be noted in the milling fluid at this time. The device 62 must then be repositioned to continue milling the section 20.

[0055] An alternative up-thruster 62 which does not suffer from bottoming out is the autoload control sub disclosed in GB2568593 which is incorporated herein by reference. This hydraulic tensioning device 62 provides continuous upward milling of the tubing by raising the work string at a desired rate of progress. The auto-load control sub 62 has a lower end moveable longitudinally relative to the by application of fluid pressure in the work string to apply a weight on the milling tool 56. The auto-load control sub 62 includes a self-correcting mechanism to maintain the lower end at a position between a fully extended position and a fully retracted position to provide continuous milling of the tubing by the milling tool 56 at a milling rate matching the rate at which the second string 58 is lifted.

[0056] In alternative embodiments, the second string 18 is rotated to operate the mill and the anti-torque anchor 64 and mud motor 40 are not used.

[0057] Due to the narrow depth of the blades 68, these will likely need to be replaced multiple times to mill the entire section 20 of well tubing 10. For this, the blades 68 are retracted and the second string 58 pulled from the well. The blades 68 are replaced and the second string 58 can be run in the well 10. The second bottom hole assembly 60 is landed on the plug 30 and the milling blades 68 will be located at the depth reference 42. From this reference point the second string 58 can be raised by an amount equal to the measured previously milled section of the well tubing 10, as shown in Figure 2(b). This distance is known from the stoke length of the up-thruster 62 and the number of times it was reset in the previous run or from the distance travelled by the second string 58 as milling occurred.

[0058] Alternatively, at surface when the blades 68 are replaced, the length of the second bottom hole assembly 60 can be extended by the calculated distance. In this way, when the second bottom hole assembly 58 lands on the plug 30, the milling blades 68 will be located at the last milling position, as shown in Figure 2(c). In either embodiment, the depth reference 42 allows the window 46 to be located for further operations and runs into the well 10. This also offers the opportunity of switching milling blades when centralisers and collars are reached or for avoiding centralisers and collars by stopping and starting milling on either side of the centralisers and collars.

[0059] The process can be repeated until the desired section 20 of well tubing 10 is removed from the well 12.

[0060] If the dual action section mill 44 is used, then once the window 46 is formed and the blades 26 are in the longitudinal position, the first string 16 can be raised while the mill 44 is rotated to remove well tubing 10 from above the cut 36. To facilitate this the first bottom hole assembly 18 would include the torque anchor 64, mud motor 40, tensioning device 62, and stabilizer 70. This is as shown in Figure 3(a). As the cutting surface of the blades 26 is longer than the narrow blades 68 in the milling tool 56, longer lengths of well tubing 10 can be milled before the first string 16 has to be removed for replacement of the blades 26. This is best facilitated by using the auto load control sub as the tensioning device 62. Once the blades 26 are replaced the same string can be run as the second string 18 and landed to the plug 30 to get the depth reference 42, see Figure 3(b) before moving to the last milled position as described herein before. Milling over a longer section can begin again to complete the removal of the section 20 of the well tubing 10. This dual action section mill 44 therefore reduces the number of trips required to remove a section 20 of well tubing 10. The dual action section mill 44 also allows milling to be stopped when a connector or centraliser is found, the blade 26 is retracted, the string 16,18 is moved to position the section mill 44 above the connector or centraliser and the blade apex 54 initially used to make a fresh cut so that milling can continue without requiring to remove the string 16,18 from the well 12. In a further embodiment, the first string 16 can include the plug 30 on the first bottom hole assembly 18. The run-in would then set the plug 30, detaching it from the first string 16, and then set down weight upon it. This would further reduce the number of trips into the well 12.

[0061] In a still further embodiment, once the section of well tubing is removed a cement plug 0 8can be created in the well tubing over the removed section of well tubing as is known in the art. This is as illustrated in Figure 3(b).

[0062] A particular advantage of one or more embodiments of the present invention is that it provides a method of removing a section of well tubing in which a depth reference is provided for location re-positioning when a further string is run in the well.

[0063] A further advantage of one or more embodiments of the present invention is that it provides method of removing a section of well tubing which overcomes the difficulties in calculating depths to locate the window due to stretch or compression in the string, particularly with coiled tubing operations.

[0064] 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, while the section mill is described for upward movement to mill the tubular, the section mill could be adapted to operate in a downward fashion also. Additionally, strings including other tools can be run in the well and perform further tasks e.g. locating a spear in a cut section of casing to pull the casing. Such a cut and pull may be attempted to see if well tubing can be removed without the need for section milling.

Claims

CLAIMS1. A method of removing a section of well tubing, comprising the steps:(a) locating a bridge plug in the well tubing;(b) providing a first string with a first bottom hole assembly comprising a cutting tool and a swivel sub;(c) running the first string into the well tubing and landing the first bottom hole assembly on the bridge plug;(d) cutting the well tubing with the first bottom hole assembly landed on the bridge plug to thereby provide a depth reference;(e) running in a second string and landing a second bottom hole assembly comprising a tubing removal tool on the bridge plug to obtain the depth reference;(f) positioning the tubing removal tool in the well tubing by relation to the depth reference; and(g) using the tubing removal tool to remove a section of the well tubing.

2. The method according to claim 1, wherein step (d) is performed by the cutting tool being operated via rotation by a motor and rotating the cutting tool on the swivel sub.

3. The method according to claim 2, wherein the motor is in the first bottom hole assembly.

4. The method according to any preceding claim, wherein the swivel sub is at an end of the first bottom hole assembly and is landed on the plug.

5. The method according to any preceding claim, wherein the cutting tool comprises one or more blades to cut the well tubing on first contact of the one or more blades with the tubing.

6. The method according to any preceding claim, wherein the tubing removal tool is a milling tool and the section well tubing is removed by milling.

7. The method according to any preceding claim, wherein the first bottom hole assembly further comprise a tubing removal tool to open up a window in the well tubing oncethe cutting tool has cut the well tubing and the method includes creating a window in the well tubing at step (d).

8. The method according to any preceding claim, wherein step (g) is performed by the tubing removal tool being operated via rotation by a motor.

9. The method according to any preceding claim, wherein step (g) is performed by raising the second string so that milling is performed in an uphole direction.

10. The method according to claim 9, wherein the second bottom hole assembly comprises a hydraulic tensioning device and maintains a constant load on the tubing removal tool as it is raised.

11. The method according to any preceding claim, wherein the cutting tool and tubing removal tool are combined and the first bottom hole assembly opens up a window in the well tubing.

12. The method according to claim 11 , wherein the second bottom hole assembly and first bottom hole assembly are identical.

13. The method according to any one of claims 1 to 11 , wherein the bridge plug is located on the first bottom hole assembly and step (a) is performed after step (b) on the same run in the well tubing.

14. The method according to any preceding claim, wherein the second bottom hole assembly comprises a swivel so that the second string can rotate when it is landed on the plug.

15. The method according to any preceding claim, wherein the well tubing has a diameter of 7” (178mm) or less.

16. The method according to claim 15, wherein the well tubing has a diameter of 4.5” (114mm).

17. The method according to any preceding claim, including the step of creating a cement plug over the milled section of well tubing.

18. Apparatus for removing a section of well tubing, comprising: a tubular string supporting a bottom hole assembly suspended therefrom; the bottom hole assembly comprising, in order from an end of the string: a combined cutting and tubing removal tool; and a swivel, wherein: the swivel is configured to allow rotation of the combined cutting and tubing removal tool when the string is landed on a plug in the well tubing.

19. The apparatus according to claim 18, wherein the combined cutting and tubing removal tool comprises a plurality of blades, each blade having a cutting edge to form a circumferential cut in the well tubing and a milling surface to mill the well tubing when rotated.

20. The apparatus according to claim 19, wherein the blades are moveable between a retracted configuration where they sit inside a body of the tool and an extended configuration where they extend radially outwards from the body for use.

21. The apparatus according to claim 20, wherein the bottom hole assembly comprises a tensioning device, the tensioning device configured to apply a constant load on the combined cutting and tubing removal tool when the blades are in the extended configuration.

22. The apparatus according to any one of claims 18 to 21 , wherein the bottom hole assembly comprises a motor and the combined cutting and tubing removal tool is between the motor and the swivel.

23. The apparatus according to claim 22, wherein the motor is a left-hand positive displacement motor.

24. The apparatus according to any one of claims 18 to 23, wherein the tubular string is coiled tubing.

25. The apparatus according to any one of claims 18 to 23, wherein the tubular string is drill pipe having a diameter of less than 7” (178mm).

26. The apparatus according to claim 25, wherein the tubular string has a diameter of less than 4.5” (114mm).

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