Downhole reforming tool and methods

Abstract

A downhole tool 20 for reforming downhole pipe 22 comprises an anchor 26 for engaging a wall of the pipe 22 above a collapsed pipe section 24, a cone 28 for translating downwards into the collapsed pi

Description

05 11 24 DOWNHOLE REFORMING METHODS FIELD This disclosure relates to methods of reforming downhole pipe. 5 BACKGROUND In the oil and gas exploration and production industries, subsurface hydrocarbon reservoirs may be accessed by drilling bores from surface to intersect the reservoirs. The bores are lined with metal pipe or tubing, such io as casing and liner, and smaller diameter tubing may be deployed within the bore-lining tubing to, for example, carry hydrocarbons from the reservoir to surface. Similar arrangements may be used in other applications where subsurface access is required, for example when accessing water-bearing aquifers, or in geothermal operations. 15 The tubing is typically cylindrical and will have a known internal diameter. An operator may thus determine, for example, the flow area of a given tubing section, or the diameter of an object, such as a tool, that may be translated through the downhole tubing. It is known for a section of downhole tubing to suffer a partial or 20 complete collapse. In such a circumstance an operator may attempt to restore the tubing to the original configuration by, for example, mounting a cone on the end of a drill pipe string and driving the cone through the collapsed section. 25 SUMMARY According to a first aspect of the disclosure there is provided a method of reforming a downhole pipe including a collapsed pipe section, the method comprising: determining parameters of the collapsed pipe section; determining a series of reforming stages to return the collapsed pipe section to a non-collapsed configuration; determining a cone geometry suitable to advance into and reform the collapsed pipe section in accordance with the determined reforming stages, 5 providing a cone according to the determined cone geometry, and translating the cone into the collapsed pipe section. The parameters of the collapsed pipe section may include one or more of: the pipe dimensions; the original form of the pipe; the geometry of the collapsed pipe, and characteristics of the pipe material. 10 The step of determining the series of reforming stages may include identifying the stresses and strains that will be experienced by the pipe at each reforming stage or the forces that will be necessary to reform the pipe at each reforming stage. This allows the operator to identify and thus avoid reforming stages that would damage the pipe, to design the most 15 advantageous series of reforming stages, and to ensure that the associated apparatus can provide the necessary reforming forces. The method may comprise selecting and providing a single cone and reforming the collapsed pipe section using the selected cone in a single reforming stage. Alternatively, the method may comprise selecting and 20 providing a first cone and a second cone; translating the first cone into the collapsed pipe section to partially reform the pipe section, and then translating the second cone into the partially reformed pipe section to further reform the pipe section. Thus, in some examples multiple cones of different configurations may be provided to allow the collapsed pipe section to be 25 reformed in multiple reforming stages. Multiple cones may be provided on a reforming tool, but it is more likely that the tool will initially be provided with the first cone and the first cone translated through the collapsed pipe section in a first reforming stage and the tool then retrieved to surface and the first cone replaced with the second cone and the second cone then translated 30 through the partially reformed pipe in a second reforming stage. 05 11 24 The method may comprise forming a test pipe section recreating the geometry and other parameters of the collapsed pipe section and translating the cone, or multiple cones, through the test pipe section. The operator may thus confirm the effectiveness and suitability of the determined cone 5 geometry and determined reforming stages. If the test identifies any issues which were not predicted from the theoretical design process the operator may implement and test modifications to the cone geometry in one or more of the predetermined reforming stages, before attempting to reform the collapsed pipe section downhole. io This further aspect of the disclosure may use an axial force generator to translate the cone into and through the collapsed pipe section. Alternatively, or in addition, weight may be applied to the cone, which weight may be applied from surface via a suitable member, such as a drill pipe string, or by providing weighted members, such as drill collars, above the 15 cone. In one example there is provided a downhole tool for reforming a collapsed section of a cylindrical downhole pipe to the original cylindrical configuration, the tool comprising: an anchor for engaging a section of a wall of a cylindrical downhole 20 pipe above a collapsed section of the pipe having a wall that has been collapsed from the original cylindrical configuration to a non-cylindrical configuration; a cone for translating downwards into the collapsed pipe section to restore the wall of the collapsed pipe section to the original cylindrical 25 configuration, the cone having one of an oval, bulb or part-spherical form and having a circular cross-section, and an axial force generator for driving the cone downwards into the collapsed pipe section. In another example there is provided a method of reforming a collapsed section of a cylindrical downhole pipe to the original cylindrical configuration, the method comprising: running a reforming tool into a cylindrical downhole pipe and 5 activating a tool anchor to engage a wall of the pipe above a collapsed section of the pipe, the collapsed pipe section having a wall that has been collapsed from the original cylindrical configuration to a non-cylindrical configuration; and driving a circular cross-section cone having one of an oval, bulb or 10 part-spherical form downwards from the tool anchor into the collapsed pipe section to restore the wall of the collapsed pipe section to the original cylindrical configuration. The cone may be provided on a leading end of the tool. The tool may be run into a bore until the cone engages an upper end of the collapsed pipe 15 section. The anchor may then be activated. The axial force generator may then be activated to drive the cone into the collapsed pipe section. The axial force generator may have a stroke which is shorter than the length of the collapsed pipe section. In such a situation, following an initial translation of the cone into the collapsed pipe section, the axial force 20 generator and the anchor may be deactivated and moved downwards, such that the axial force generator resets. The anchor may then be reactivated, followed by the axial force generator, to advance the cone further into the collapsed pipe section. This process may be repeated until the cone has been translated through the length of the collapsed pipe section. 25 The tool may be configured for mounting on an elongate support member, such as a tubing string or coiled tubing. The anchor may take any appropriate form, and may have an initial retracted configuration, in which the anchor may be translated through the pipe, and an activated extended configuration, in which slips, or other 30 anchoring members are radially extended to engage the pipe wall. The 05 11 24 anchor may be retained in the initial retracted position by a releasable coupling, such as a shear pin or ring. The anchor may be activated in any appropriate manner, for example the anchor may be fluid pressure activated. The anchor may include a through bore or other fluid passage to 5 allow fluid communication into or through the anchor. An elevated fluid pressure may be applied to the retracted anchor to activate or release the anchor from the initial retracted position and permit the anchor to assume the activated extended configuration. The anchor may be biased towards a retracted configuration such that a reduction in an activation force will cause io the anchor to return to the retracted configuration. With the anchoring members extended the anchor may be movable downwards but will resist upwards movement. A further elevated pressure, selected to be above the normal operating pressures for the tool, may be used to force deactivation of the anchor and retract the anchor members. 15 The anchor may include a cam member axially movable in response to an elevated pressure to urge an anchoring member radially outwards. The cam member and the anchoring member may be arranged such that downwards movement of the tool relative to an extended anchoring member tends to move the anchoring member radially inwards and down a cam face 20 of the cam member, whereas upwards movement of the tool relative to an extended anchoring member tends to maintain the anchoring member radially extended and urges the anchoring member up the cam face. The axial force generator may take any appropriate form and may comprise a drive unit. The axial force generator may be activated in any 25 appropriate manner and may be fluid pressure activated. The axial force generator may include a through bore or other fluid passage to allow fluid communication through or into the force generator. The force generator may include one of more axially movable pistons actuated by the pressure differential between the interior and the exterior of the tool. 05 11 24 The anchor may be activated by a first fluid pressure and the axial force generator activated by a second fluid pressure higher than the first fluid pressure. In some examples the cone may have a main axis intended to be co-5 axial with the pipe and a body which tapers from a generally circular base and has a circular cross-section over the length of the cone. However, in other examples a further cone may be provided, this cone having an eccentric, non-symmetrical or irregular form. For example, a leading end of the cone may be configured to be offset from the pipe axis. io The cone may define a through flow passage such that fluid may be flowed through the cone to, for example, provide lubrication, displace debris, and facilitate well control. The flow passage may include a restriction or nozzle to facilitate generation of an elevated pressure in the fluid above the cone. 15 It will be understood that the various features described above, and as claimed below, may have utility separately of the recited aspects. Also, the skilled person will understand that the features described above with reference to one aspect of the disclosure, and as claimed below, may be combined with the other aspects of the disclosure. 20 BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: 25 Fig. 1 is a sectional view of a downhole tool in accordance with an example of the disclosure; Figs. 2 to 7 are sectional views of the tool of Fig. 1, illustrating a sequence of steps during a pipe reforming process and the corresponding tool configurations; Figs. 8, 9 &10 are enlarged sectional views of an anchor assembly of the tool of Fig. 1 in configurations corresponding to Figs. 2, 3 &7, respectively; Figs 11 &12 are sectional views of a drive unit assembly of the tool 5 of Fig. 1 in configurations corresponding for Figs. 2 &5, respectively; Figs 13a &13b are sectional and end views of the nose cone of the downhole tool of Fig. 1, and Figs. 14a &14b through Figs. 17a &17b are sectional and end views of nose cones of different configurations. io 15 DETAILED DESCRIPTION OF THE DRAWINGS Reference is first made to Fig. 1 of the drawings, a sectional view of a downhole tool 20. As will be described, the tool 20 has utility in reforming downhole pipe 22 (Fig. 2) that has collapsed. As will be described, the nature of the collapse (radial and axial extent, form, and the like) will vary, and the drawings illustrate a collapse in the form of a short section of pipe 24 that has been subject to a substantial and symmetrical reduction in diameter. The tool 20 has a generally cylindrical elongate form and is intended 20 to form a bottom hole assembly (BHA) for mounting on the end of an elongate support member such as a drill pipe string or coil tubing which attaches to a suitable coupling at the upper end of the tool 20 (the left-hand end of the tool 20 as illustrated in Fig. 1). The tool 20 may thus be run into a well lined with pipe such as a completion, casing, or liner. 25 The tool 20 comprises an anchor 26 at the upper end of the tool for selectively engaging a wall of the pipe 22 above the collapsed pipe section 24, a cone 28 at the lower end of the tool for translating downwards into the collapsed pipe section 24, and an axial force generator or drive unit 30 between the anchor 26 and the cone 28 for driving the cone 28 downwards 30 into the collapsed pipe section 24. The tool 20 defines a central through bore 32 allowing fluid communication between a surface rig and the tool 20 via the supporting drill pipe or coil tubing; thus, fluid pressure may be utilised to actuate the anchor 26 and the drive unit 30, and in some examples the cone 28 may be 5 provided with cleaning or lubricating nozzles. The operation of the tool 20 will be described briefly with reference to Figs, 2 through 7 of the drawings, followed by a more detailed description of the elements of the tool 20. The tool 20 is initially provided in an axially retracted or un-stroked configuration, as illustrated in Figs. 1 &2. The tool io 20 may be assembled on the surface rig and then mounted on the support string such that the tool 20 may be run into the well. The tool 20 is run into the well until the cone 28 tags or engages the upper end of the collapse 24 (Fig. 2); the depth of the collapse 24 will have been established by earlier surveys and the engagement of the cone 28 with the collapse will be evident 15 at surface by a reduction in string tension. The tool 20 and supporting string are filled with fluid and connected to surface pumps, and once the cone 28 has engaged the collapse 24 the pumps are activated to increase the fluid pressure to a first level and actuate the anchor 26 to extend and engage the inner surface of the surrounding 20 pipe 22 (Fig. 3). A further increase in fluid pressure actuates the drive unit 30 to stroke or extend and translate the cone 28 into the collapse section of pipe 24 (Fig. 4). In the illustrated example a full stroke of the drive unit 30 is sufficient to translate the cone through the collapse 24 and return the pipe 22 to the 25 original form (Fig. 5). If the internal tool fluid pressure is then reduced, the anchor 26 releases (Fig. 6), allowing the tool 20 to be retrieved to the surface. However, if the anchor 26 does not release on the pressure reducing, a shear contingency feature allows the anchor 26 to be hydraulically retracted 30 (Fig. 7). Reference is now also made to Figs. 8, 9 &10, enlarged sectional views of the anchor 26 in configurations corresponding to Figs. 2, 3 &7, respectively. The anchor 26 has a generally cylindrical body 34 comprising an upper part 34a, and a lower part 34b. The lower part 34b includes a 5 reduced diameter portion having an external cam profile 36 including four inclined cam surfaces 38. Slips 40 are located around the profile 36 and have an internal surface 42 configured to cooperate with the cam surfaces 38. The upper and lower ends of the slips 40 are restrained by axially movable upper and lower collars 44a &44b. The lower collar 44b is axially io restrained by a sleeve 46 pinned to the anchor body part 34b. The sleeve 46 accommodates a compression spring 48 which tends to urge the lower collar 44b, and thus also the slips 40, upwards relative to the anchor body 34. The upper collar 44a may initially be pinned to the anchor body 36 to 15 prevent accidental actuation of the anchor 26. Fluid pressure in the tool bore 32 is communicated, through radial ports 50, to a chamber 52 formed between the collar 44a and the anchor body 34. The upper end of the chamber 52 is isolated from the exterior of the tool by a larger diameter seal 54a between the collar 44a and the upper body part 34a, and the lower end 20 of the chamber 52 is isolated from the exterior of the tool by a smaller diameter seal 54b between the collar 44a and the lower body part 34b. If the fluid pressure in the chamber 52 exceeds the pressure in the annulus 56 between the tool 20 and the pipe 22 and is in excess of a first level sufficient to release a retaining shear pin, the collar 44a is urged 25 downwards, translating the slips 40 downwards and over the cam profile 36. The relative axial movement of the slips 40 and the cam 36 causes the slips 40 to move radially outwards and engage the inner surface of the pipe 22, as shown in Figs. 3 &9. As described above, the lower collar 44b is urged upwards by the spring 48 and in the absence of an elevated internal 30 tool pressure will maintain the slips 40 in an upper, retracted configuration. However, an elevated internal tool pressure will overcome the spring force and translate the collar 44b downwards, together with the slips 40. With the slips 40 extended the anchor 26 secures the upper end of the tool 20 relative to the pipe 22 and permits the drive unit 30 to be actuated 5 to drive the cone 28 through the collapse 24, as will be described. In normal operations the lower sleeve 46 does not move as the slips 40 are extended and retracted. However, fluid pressure in the tool bore 32 is communicated, through radial ports 60, to a chamber 62 formed between the sleeve 46 and the anchor body 34. The lower end of the chamber 62 is io isolated from the exterior of the tool by a larger diameter seal 64a between the sleeve 46 and the body 34, and the upper end of the chamber 62 is isolated from the exterior of the tool by a smaller diameter seal 64b between the sleeve 46 and the body 34. Thus, an internal tool pressure in excess of the annulus pressure will tend to urge the sleeve 46 upwards. However, the 15 sleeve 46 is fixed to the anchor body 36 by a pin 66. Thus, only on exposure to an elevated internal fluid pressure in excess of a third level sufficient to shear the pin 66 will the sleeve 46 move upwards, as illustrated in Figs. 10. Such upwards movement is transferred to the lower collar 44b, the slips 40, and the upper collar 44a, and causes the slips 40 to retract. 20 The annular area defined by the seals 64a &64b of the lower chamber 62 is greater than the area defined by the seals 54a &54b of the upper chamber 52 such that, once the pin 66 has been sheared, the fluid pressure acting of the sleeve 46 will overpower the (same) pressure acting on the collar 44a. Thus, if the retracting force generated by the spring 48 is 25 insufficient to translate and retract the slips 40, an elevated pressure may be utilised to force retraction of the slips 40 and release of the anchor 26. Reference is now made also to Figs. 11 &12 of the drawings, sectional views of a drive unit 30. The drive unit 30 comprises a generally cylindrical body 70 comprising an inner body assembly 70a connected to 30 the lower end of the lower anchor body part 34b, and an outer body assembly 70b, the lower end of which provides mounting for the cone 28. The inner body assembly 70a comprises three coaxial cylindrical members 72a, 72b, 72c secured end-to-end by two collars 74a, 74b. The outer body assembly 70b comprises a cylindrical tube 76 providing mounting for two 5 annular pistons 78b, 78c, the tube 76 having an inner surface in sliding, sealing engagement with the outer surfaces of the collars 74a, 74b, via seals 80a, 80b. The pistons 78b, 78c form the lower walls of respective chambers 82b, 82c in fluid communication with the tool bore 32 via pressure communicating ports 84b, 84c in the cylindrical members 72b, 72c. The io pistons 78b, 78c form the upper walls of annular chambers 86b, 86c formed between the tube 76 and the members 72b, 72c, the chambers 86b, 86c being in fluid communication with the annulus 56 via pressure communication ports 88b, 88c in the tube 76. A collar 89 mounted on the lower end of the member 72c provides the lower wall of the chamber 86c. 15 A similar chamber 86a is defined between the cylindrical member 72a and the tube 76 and communicates with the annulus 56 via ports 88a. The skilled person will recognise that an elevated internal tool pressure, selected to be between the first and third levels, will create a differential pressure and a resultant axial force across the pistons 78b, 78c, 20 urging the outer body assembly 70b, and the cone 28 mounted thereon, downwards relative to the inner body assembly 70a, as illustrated in Fig. 12. Reference is now also made to Figs. 13a &13b, sectional and end views of the cone 28. The cone 28 of this example has a generally solid, spherical nose 90 and a generally cylindrical mounting portion 92 having a 25 profile to engage with the lower end of the tube 76 and a circumferential slot 94 to locate a seal 96. In use, an operator will first have determined the location and form of the collapse 24. The operator will also have information on the nature and parameters of the pipe 22, for example the pipe diameter, wall thickness, 30 material, pipe properties, and presence or absence of a surrounding 05 11 24 concrete sheath. Surveys may also be used to determine the axial and radial extent of the collapse 24. The drawings illustrate a collapse 24 in the form of a symmetrical radial restriction in the pipe diameter, however a pipe collapse may take any form. Depending on the nature of the collapse, the 5 operator will select an appropriate form of cone nose 90 and may model the reforming of the collapse 24 using appropriate simulations. The operator may determine that reforming the collapse 24 in a single pass of a cone 28 would require application of excessive forces or would expose the pipe wall to damaging stresses and strains and may thus io select multiple cone forms to be run in sequence to reform the collapse in a series of stages. Before attempting to reform the downhole pipe 22, the operator may recreate the collapse 24 in a test specimen of similar material and dimensions to the pipe 22 and attempt to reform the replication of the 15 collapse 24 on surface using the selected cone nose 90 or the selected sequence of cones. This allows the operator to identify any issues that may arise and were not predicted by modelling, and the operator may run a multitude of tests using a variety of cone forms and reforming stages to identify the optimum cone geometries and reforming stages for a particular 20 collapse geometry. The resulting downhole reforming operation is thus far more likely to be successful and less likely to encounter problems. The tool 20 is initially provided with the slips 40 in a retracted configuration, and with the drive unit 30 in an axially retracted or un-stroked configuration, with the drive unit pistons 78b, 78c located towards the upper 25 ends of their respective chambers 86b, 86c. In this configuration the upper end of the cone mounting portion 92 is directly adjacent the lower end of the cylindrical member 72c. The tool 20 may be shipped in an assembled state or may be assembled on the surface rig. The assembled tool 20 is mounted on the support string and run into the well. The operator will be aware of the depth of the collapse 24 such that the length of support member required to run the tool 20 to target depth will be known. As the tool 20 approaches the collapse 24 the tool 20 will be advance slowly until the cone 28 tags or engages the upper end of the 5 collapse 24 (Fig. 2). Engagement of the cone 28 with the collapse 24 will be evident at surface by a reduction in string weight. The tool 20 and supporting string may be top filled to ensure that the tool bore 32 is filled with fluid. The top of the support string may be connected to surface pumps and the pumps activated to increase the io internal tool pressure to a first level. This pressure is communicated to the anchor piston chamber 52 and the upper collar 44a is urged downwards. The collar 44a may be initially pinned to the anchor body part 34a and the pressure required to move the collar 44a must be sufficient to shear the pin. Downwards translation of the collar 44a translates the slips 40 downwards 15 and causes the slips 40 to move radially outwards as the slip internal surfaces 42 ride up the corresponding cam surfaces 38. Downwards movement of the slips 40 is controlled and limited by engagement with the lower collar 44b, which is biased upwards by the spring 48. The slips 40 are thus moved outwards into contact with the inner 20 surface of the pipe 22; the tool 20 is thus anchored in the pipe 22. The slips 40 will remain extended while the internal tool pressure is maintained. The surface pumps are then actuated to generate a further increase in the tool internal fluid pressure, to a predetermined second level, to actuate the drive unit 30. The fluid pressure in the tool bore 32 is 25 communicated via the ports 84b, 84c to the chambers 82b, 82c to urge the pistons 78b, 78c downwards. The pistons 78b, 78c, and the attached tube 76 move downwards relative to the inner cylindrical members 72a, 72b, 72c, to axially extend the unit 30 and translate the cone 28 into the collapsed section of pipe 24 (Fig. 4). The cone nose 90 engages the inner surface of 30 the collapse 24 and forces the collapsed pipe wall radially outwards, to return to the original cylindrical configuration. In the illustrated example a single stroke of the drive unit 30 is sufficient to translate the cone 28 through the collapse 24 and return the pipe 22 to the original form (Fig. 5). The operator may see a drop in internal tool pressure when the cone 28 has 5 translated through the collapse 24 and the resistance to further axial translation of the cone 28 is reduced. While the internal tool pressure is acting to extend the drive unit 30, there is an upwards reaction force acting on the inner body assembly 70a, 72c, which is transmitted to the lower anchor body part 34b. Through the io interaction of the cam profile 36 formed on the part 34b with the inner slip surfaces 42, the slips 40 are urged outwards and the engagement between the anchor 26 and the pipe 22 is enhanced. Once the cone 28 has been fully stroked the surface pumps may be deactivated and the internal tool pressure allowed to fall. This allows the 15 anchor spring 48 to extend and move the slips 40 upwards, such that the slips 40 may radially retract. With the anchor 26 in the retracted configuration, the tool 20 may be retrieved to the surface (Fig. 6). However, if the stroke of the drive unit 30 has not been sufficient to extend the cone 28 all the way through and 20 completely reform the collapse 24, the operator may apply weight to the tool 20 to reset or un-stroke the drive unit 30 and return the pistons 78b, 78c to the start of the tool stroke. Increasing the internal tool pressure again will activate the anchor 26 and then stroke or extend the drive unit 30 to force the cone 30 further through the collapse 24. 25 The ability to reset or axially retract the tool 20 in this manner facilitates the reforming of longer collapses while allowing the length of the tool 20 to be kept relatively short. This may allow the tool 20 to be fitted within the length of a coiled tubing lubricator, facilitating the safe mounting of the tool 20 on coiled tubing. A restricted tool length also facilitates storage 30 and transportation of the assembled tool. If the anchor 26 does not release on reduction of the internal tool pressure, the shear contingency feature may be utilised, whereby the surface pumps are activated to generate a higher internal fluid pressure, at a third level, which is communicated to the anchor unit chamber 62. If the 5 pressure is sufficiently high the upwards force acting on the sleeve 46 will shear the sleeve-retaining pin 66 and translate the sleeve 46 upwards (Fig. 10). The movement of the sleeve 46 results in a corresponding upwards movement of the collar 44b and the slips 40, causing the slips 40 to radially retract. io With the anchor 26 released from the pipe 22, the tool 20 may be retrieved to surface. Reference is now made also to Figs. 14a &14b through Figs. 17a &17b, sectional and end views of nose cones of different configurations. Figs. 14a &14b illustrates a cone nose 100 which has a generally spherical form, 15 like the nose 90 described above. However, the nose 100 includes three flow passages 102 leading from the tool bore 32 to nozzles 104 in an end face of the nose 100, whereby fluid may be directed through the nose for cleaning, lubrication and well control. Figs. 15a &15b illustrate a pointed nozzled nose cone 110, which 20 may have utility in a collapse where the internal diameter of the pipe has been significantly reduced and an attempt to reform the collapse using a relatively blunt cone will result in significant axial forces acting between the cone and the collapsed pipe, whereas the pointed cone 110 may generate forces having a larger radial component. 25 Figs. 16a &16b illustrate a nozzled oval nose cone 120 which may facilitate entry of the cone into a collapsed pipe section. Figs 17a &17b illustrate a spade-form nose cone 130 in which the cone leading end 132 is radially offset from the main tool axis, and thus also from the main pipe axis. The cone 130 is intended to only partially reform a 30 collapse, and to prepare the collapse to receive one or more alternative cone forms which may be used to return the pipe to a cylindrical form. This form of cone may facilitate reforming a collapse in which, for example, one side of the pipe remains substantially cylindrical in form while the opposite side of the wall has experienced a significant degree of deformation. The 5 nose end 132 may be advanced into such a collapse and oriented to locate the end 132 in the small and offset gap between the opposing sides of the collapsed pipe. When the nose cone 130 is translated into the collapse the cone 130 will apply reforming forces with a significant radial element to the wall portion which has experienced the greater degree of deformation. io Once the collapse has been partially opened by the cone 130, the tool 20 may be returned to surface and the cone 130 removed and replaced by, for example, an appropriate symmetrical cone form, such as those described above. The tool 20 is then re-run into the partially reformed pipe 22 and the second cone form used to further reform the collapsed pipe. 15 In such a situation, analysis of the collapse may have identified that reforming the collapse would be best achieved using a combination of cone forms, with the spade-form cone 130 being useful in an initial reforming operation, and a subsequent run with another cone form allowing restoration of the collapse to the initial cylindrical pipe form. Other collapses may be 20 reformed in multiple reforming stages using three or more progressively changing cone forms. The skilled person will appreciate that an initial detailed analysis of the collapsed pipe section and the subsequent development and analysis of one or more reforming stages substantially increases the likelihood of 25 successfully reforming the pipe. The skilled person will also appreciate that the illustrated tool is only one example of a tool suitable for implementing the disclosed reforming method. In other examples, one or both of the anchor and the axial force generator may be omitted, and other means employed to translate the 30 cones through the collapsed pipe section: weight may be utilised to drive the cone into the pipe, and for example drill collars may be provided above the cone. 5 REFERENCE NUMBERS: downhole tool 20 downhole pipe 22 collapsed pipe section 24 10 anchor 26 cone 28 drive unit 30 tool bore 32 CM anchor body 34 i— 15 upper &lower anchor body parts 34a, 34b 1 cam profile 36 o cam surfaces 38 slips 40 slips internal surface 42 20 upper &lower collars 44a, 44b sleeve 46 compression spring 48 pressure communication ports 50 piston chamber 52 25 piston seals 54a, 54b annulus 56 pressure communication ports 60 piston chamber 62 piston seals 64a, 64b 30 pin 66 05 11 24 drive unit body 70 inner, outer body assemblies 70a, 70b cylindrical members 72a, 72b, 72c collars 74a, 74b 5 tube 76 pistons 78b, 78c seals 80a, 80b chambers 82b, 82c pressure communicating ports 84b, 84c 10 chambers 86a, 86b, 86c pressure communication ports 88a, 88b, 88c collar 89 cone nose 90 cone mounting portion 92 15 slot 94 seal 96 cone nose 100 flow passages 102 20 nozzles 104 cone nose 110 cone nose 120 25 cone nose 130 cone leading end 132

Claims

10 09 241. A method of reforming a downhole pipe including a collapsed pipe section, the method comprising:5 determining parameters of the collapsed pipe section;determining a series of reforming stages to return the collapsed pipe section to a non-collapsed configuration,determining a cone geometry suitable to advance into and reform the collapsed pipe section in accordance with the determined reforming stages, io providing a cone according to the determined cone geometry, andtranslating the cone into the collapsed pipe section.

2. The method of claim 1, further comprising:providing a first cone and a second cone;15 translating the first cone into the collapsed pipe section to partiallyreform the pipe section, andtranslating the second cone into the partially reformed pipe section to further reform the pipe section.20 3. The method of claim 2, further comprising:retrieving the first cone from the downhole pipe;removing the first cone from a support member;mounting the second cone on the support member, and running the second cone into the pipe.

254. The method of claim 1, 2 or 3, wherein the parameters of the collapsed pipe section may include one or more of: the pipe dimensions; the original form of the pipe; the geometry of the collapsed pipe, and characteristics of the pipe material.

305. The method of any one of claims 1 to 4, wherein the step of determining the series of reforming stages includes identifying reforming force magnitudes that will be necessary at each reforming stage.5 6. The method of any one of claims 1 to 5, further comprising forming atest pipe section recreating the geometry of the collapsed pipe section and translating the cone through the test pipe section before translating the cone into the collapsed pipe section of the downhole pipe.io 7. The method of any one of claims 1 to 6, further comprising providing a hydraulically actuated axial force generator to translate the cone into the collapsed pipe section.

8. The method of any one of claims 1 to 7, further comprising providing drill 15 collars to provide weight to translate the cone into the collapsed pipe section.

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