Patent Publication Number: US-10787888-B2

Title: Downhole expansion tool and method for use of the tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This United States application is the National Phase of PCT Application No. PCT/N02017/050267 filed 16 Oct. 2017, which claims priority to Norwegian Patent Application No. 20161669 filed 19 Oct. 2016, each of which is incorporated herein by reference. 
     BACKGROUND 
     The present invention regards an expansion tool which is positioned within a damaged tubing. In particular the tubing may be positioned within a petroleum well drilled in the ground. The tubing has a deformation which makes it impossible to enter and pass the deformed area with a tool. The deformation makes the tubing useless. The expansion tool comprises radially displaceable expansion elements. More particularly, the expansion tool is adapted to expand radially a small portion of the deformed area. Thereafter, in a series of steps, adjacent portions of the damaged area are expanded until the whole deformation is repaired. 
     Many known expansion tools have a fixed diameter. These are pushed axially through an indentation by brute force. This harms the inner surface of the tube and may harm the tubing itself. The expansion tool may become stuck. It is known to use a stroker to push such an expansion tool through the indentation. 
     Damages may occur to a petroleum well construction. By accident, a production tubing may in a portion be indented or constricted, known as a tubing dent. Such damages to the tubing may be unintentionally caused by heavy well intervention equipment such as snubbing and coil tubing. Such damages may also be caused by external compression forces. Small changes or shifts along a fault zone may also impact a tubing. Sometimes, dependent on the cause and on the extent of the damage, the damage may be repaired in situ by an expansion tool or by a swaging tool. Parts of devices within the production tubing may be damaged. Such a part may be a flow tube in a tubing retrievable down hole safety valve (DHSV) which may make the DHSV nonfunctional. The well must be shut down. The production tubing must be retrieved and the DHSV replaced. Thereafter the well must be completed. This is a time consuming and expensive operation. 
     It would be beneficial if the flow tube could be repaired in situ. However, a DHSV may be irreparable damaged by forcing a fixed diameter expansion tool of known type through the flow tube. A more gentle method would be to convert a damaged tubing retrievable DHSV to a functional wireline retrievable DHSV. This could be done by expanding the flow tube to substantially its original shape and diameter and install by a wireline operation a retrievable DHSV. This will give considerable savings and the down time of the well will be reduced. 
     The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art. 
     The object is achieved through features, which are specified in the description below and in the claims that follow. 
     SUMMARY 
     In a first aspect the invention relates more particularly to an expansion tool for expanding a tubing, the expansion tool comprises:
         a rear portion;   an opposite leading end;   an expansion piston within the expansion tool, the expansion piston comprising an expansion cone; and   radially movable expansion elements forming a circumferential expansion body, where the rear portion is adapted for engaging a power source, said power source is positioned at the rear portion, and the expansion tool further comprises:   a plurality of expansion arms surrounding the expansion piston, each expansion arm is on an outer side provided with an expansion element; and   a wedge portion between the expansion element and the expansion cone, said wedge portion abutting the expansion cone.       

     The expansion tool is in particular adapted for expanding a tubing within a well, such as a petroleum well. The expansion elements are interchangeably connected to the expansion arm. 
     An outward front end surface and an outward rear end surface of the expansion element may be at an equal distance to a centre axis. The outward front end surface and the outward rear end surface may form a continuous outward expansion surface. 
     The expansion cone may taper towards the expansion tool&#39;s leading end with an angle “α” relative to a centre axis of the expansion tool. 
     Each expansion arm may extend forward from a holding sleeve to the expansion element. An arm extension may extend from the expansion element towards and into a guiding sleeve, said guiding sleeve being connected to a free end of the expansion piston at the expansion tool&#39;s leading end. Said arm extension may form an outer surface tapering towards the expansion tool&#39;s leading end. The outer surface may taper towards the expansion tool&#39;s leading end with an angle “α” relative to a centre axis of the expansion tool. An inside portion of the guiding sleeve may abut the outer surface of the arm extension. 
     A holding portion at the expansion arm&#39;s rear end may be locked axially and radially in a circumferential assembly groove in the holding sleeve by an adapter sleeve fitted on the outside and circumventing the expansion arm&#39;s rear end. The holding portion may, however, be displaced slightly relative to the holding sleeve as the holding portion may not be fixed to the holding sleeve or the adapter sleeve by means of a screw, bolt or other fastening means, such as a weld or a hinge. In an alternative embodiment the holding portion may be positioned in a recess in the in the holding sleeve and secured by the circumventing adapter sleeve. The expansion arms front ends are displaced radially outwards by the forward movement of the expansion piston. The expansion arms holding portion at the rear end may be locked in the radial direction by the adapter sleeve. Thus the expansion arms may be bent outwards without any distinct axis of rotation. The outward displacement of the expansion arms&#39; front ends may create a tension in the expansion arms, and this tension may assist in an inward radial displacement of the expansion arms&#39; front ends when the expansion piston is retracted towards the rear portion. 
     The wedge portion may widen towards the expansion tool&#39;s leading end. The wedge portion may widen with an angle “α” relative to a centre axis of the expansion tool. 
     The expansion cone may be provided with a plurality of axially oriented guiding grooves, and the wedge portion may be provided with an axially oriented guiding protrusion, and the guiding protrusion is complementary to one of the guiding grooves. 
     The arm extension portion may in a free end be provided with a guide pin; the guiding sleeve may be provided with a plurality of axially oriented guide slits; and each guide pin may be positioned in a respective guide slit. 
     The expansion tool may be provided with an inner release sleeve connected to the expansion arms, the inner release sleeve may be axially displaceable relative to an outer release sleeve at the expansion tool&#39;s rear portion, the outer release sleeve may be fastened to the inner release sleeve with at least one shear pin, and the inner release sleeve may be provided with a rim that abuts an internal emergency release shoulder in the outer release sleeve when the inner release sleeve is fully displaced relative to the outer release sleeve. 
     In a second aspect the invention relates more particularly to a method for expanding a tubing from within, where the method comprises the steps to: 
     a) provide an expansion tool with a circumferential expansion body, said expansion body comprising a plurality of peripheral expansion elements, the expansion elements are radially movable between a retracted position and an expanded position; 
     b) provide a power source and connect the power source to the expansion tool&#39;s rear portion; 
     c) provide a transportation means adapted to displace the expansion tool and the power source within the tubing; 
     d) displace the expansion body to a first portion of a deformation of the tubing; 
     e) activate the power source such that the expansion elements are displaced radially and are engaging the inner surface of the tubing; 
     f) displace radially and outwardly the expansion elements to a first intended radial distance; 
     g) displace radially and inwardly the expansion elements to a second intended radial distance which is less than the first radial distance; and 
     h) retract the expansion tool, the power source and the transportation means out of the tubing. 
     The method may further comprise the steps after step g) and before step h): 
     g 1 ) displace axially the expansion body to a second portion of the deformation, said second portion being adjacent to the first portion; 
     g 2 ) repeat the steps e)-g); and 
     g 3 ) optionally repeat the steps e)-g 2 ). 
     The method may further comprise before step h) the step of displacing the expansion elements to a third intended radial distance less than a fully expanded radial distance and run the expansion body through the entire length of the expanded and repaired deformation. The expansion body may be run through the entire length of the expanded and repaired deformation from the final expanded portion of the repaired deformation to the initial expanded portion of the repaired deformation. 
     In the following is described an example of a preferred embodiment illustrated in the accompanying drawings, wherein: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows in a perspective view an expansion tool in a retracted position and a stroker connected to the expansion tool, within a tubing with a damage; 
         FIG. 2  shows in a larger scale a front view of the expansion tool within a damaged section of a tubing; 
         FIG. 3  shows in a different scale the expansion tool in a retracted position; 
         FIG. 4  shows in the same scale as  FIG. 3  the expansion tool in a fully expanded position; 
         FIG. 5  shows in the same scale as  FIG. 3  the expansion tool in an emergency retracted position; 
         FIG. 6  shows in another scale a side view of the expansion tool in a retracted position; 
         FIG. 7  shows in the same scale as  FIG. 6  a cross section of the expansion tool along the line A-A; 
         FIGS. 8-10  show enlarged portions of  FIG. 7 ; 
         FIG. 11  shows in the same scale as  FIG. 6  a side view of the expansion tool in a fully expanded position; 
         FIG. 12  shows in the same scale as  FIG. 6  a cross section of the expansion tool in  FIG. 11  along the line C-C; 
         FIGS. 13-15  show enlarged portions of  FIG. 12 ; 
         FIG. 16  shows in the same scale as  FIG. 6  a side view of the expansion tool in an emergency retracted position; 
         FIG. 17  shows in the same scale as  FIG. 6  a cross section of the expansion tool in  FIG. 16  along the line D-D; and 
         FIGS. 18-21  show enlarged portions of  FIG. 17 . 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings, the reference numeral  1  indicates an expansion tool for a tubing. The expansion tool  1  forms a rear portion  10  and a leading end  19 . As seen in  FIGS. 3-5  the expansion tool  1  comprises from the leading end  19  towards the rear portion  10 , a bull nose  2  comprising a bull nose cap  20 , an expansion body  3 , a guiding sleeve  22  between the expansion body  3  and the leading end  19 , axially extending expansion arms  31 , an adapter sleeve  6 , a holding sleeve  5 , and an outer release sleeve  7 . As shown in  FIGS. 7, 12 and 17 , the expansion tool  1  comprises further an axial displaceable expansion piston  4 , and an inner release sleeve  51  connected to the holding sleeve  5 . 
     In the description, the term front and front end means the leading end  19  of the expansion tool  1 . Forward is in a direction towards the leading end  19 . Backwards and rearwards is in a direction towards the rear portion  10 . A tail and a tail end is at the rear portion  10 . 
     As seen in  FIG. 1 , the expansion tool  1  is connected to a power source  8 . The power source is shown as a stroker  82 . The stroker  82  is of a type known per se. The assembly of the stroker  82  and the expansion tool  1  is lowered within a tubing  91  by a wire line (not shown) in a manner known to the skilled person. The wire line provides electrical power to the power source  8 . As an alternative the assembly may be displaced in a deviating or horizontal tubing  91  by a tractor (not shown). The tractor is connected to the wire line and receives energy from the wire line. In  FIG. 1  it is shown that the assembly is lowered until the expansion body  3  is located at a damage  95  of a flow tube  93  within the tubing  91 . The exact position of the damage  95  within the flow tube  93  has been located in advance in a manner known to the skilled person. The internal geometry of the damage  95  may also have been mapped in advance. The exact position of the expansion body  3  is also known to an operator. Optionally, the stroker  82  is secured to an internal wall  97  of the tubing  91  by activating the stroker&#39;s  82  slips  83 . 
     The holding sleeve  5  is at a front portion  50  provided with a circumferential assembly groove  509  as best seen in  FIGS. 10 and 20 . An expansion arm&#39;s  31  rear end  319  is provided with a holding portion  311  which fits complementary in the assembly groove  509 . The adapter sleeve  6  covers the expansion arm&#39;s  31  rear end  319  on the outside. Thus the holding portion  311  is locked axially and radially in the circumferential assembly groove  509  by the adapter sleeve  6 . The holding portion  311  may, however, be displaced slightly relative to the holding sleeve  5  as the holding portion  311  is not fixed to the holding sleeve  5  or the adapter sleeve  6  by means of a screw, bolt or other fastening means, such as a weld or a hinge. In an alternative embodiment the holding portion  311  is positioned in a recess (not shown) in the in the holding sleeve  5  and secured by the adapter sleeve  6 . 
     The expansion arms  31  extend axially from the holding sleeve  5  towards the leading end  19 . Each expansion arm  31  is on its outside  315  in a portion provided with an interchangeable expansion element  33 . The expansion element  33  forms an outward front end surface  330  and an outward rear end surface  339 . The outward front end surface  330  and the outward rear end surface  339  form a continuous outward expansion surface  333 . In  FIG. 6  it is shown with dashed lines the profile of increasing sized expansion elements  33 . Each expansion element  33  is releasably fastened to a corresponding expansion arm  31  with screws  331 . The expansion arm  31  is shown formed with a straight portion from the rear end portion  319  towards the expansion body  3 . The width and thickness of the straight portion is substantially constant along the straight portion. The expansion arms  31  may be made of a strong material such as steel. 
     The expansion arm  31  forms a front end  310 . In the figures each expansion arm  31  is shown extending past the expansion elements  33  between the expansion elements  33  and a centre axis  99 . Each expansion arm  31  is shown connected to an arm extension  35  which extends from the rear portion of the expansion body  3  towards the leading end  19 , as best seen in  FIGS. 7, 12 and 17 . The arm extension  35  is shown connected to the expansion arm  31  with screws  353 , as best seen in  FIGS. 9, 14 and 19 . The arm extension  35  is at a front end  350  provided with a guide pin  351 . The guide pin  351  points outward in a radial direction. The arm extension  35  is in the expansion body  3  portion provided with a wedge portion  37  provided with an inclined face  371  facing inward towards the centre axis  99 , as best seen in  FIGS. 9 and 14 . The inclined face  371  tapers towards the rear portion  10 . The arm extension  35  forms between the expansion body  3  and the front end  350  a straight side facing the centre axis  99 . The opposite, outer side of the arm extension  35  is formed with an inclined face  355  tapering towards the leading end  19 , as best seen in  FIGS. 7, 11, 12 and 17 . The inclined face  355  and the inclined face  371  both form an angle “α” with reference to the centre axis  99 . 
     In the figures, the expansion arm  31  and the arm extension  35  are shown as two separate pieces with overlapping portions and joined together with screws  353 . In an alternative embodiment the expansion arm  31  and the arm extension  35  are made of one piece of material. The function of the expansion arm  31  and the arm extension  35  is described in what follows, and the function is the same either the expansion arm  31  and the arm extension  35  are made of separate pieces or made of one piece of material. The arm extensions  35  may be made of a strong material such as steel. 
     The axial displaceable expansion piston  4  is internally and centrally positioned within the expansion tool  1  along the centre axis  99 . The expansion piston  4  forms a free end  40  at the leading end  19  and a piston rear end  49 . The piston rear end  49  is positioned within the holding sleeve  5  when the expansion tool  1  is in its inactive, retracted position. The piston rear end  49  is provided with a connector  81  for a stroker organ (not shown). The free end  40  is firmly connected to the bull nose  2 . The bull nose  2  is shown comprising the bull nose cap  20  at the end of the leading end  19 . The free end  40  is further firmly connected to the guiding sleeve  22  adjacent the bull nose cap  20 . The guiding sleeve  22  is formed as a frustum with the narrow part facing the leading end  19  and the wide part facing the expansion body  3 . A rear portion of the internal face of the guiding sleeve  22  forms an angel “α” with respect to the central axis  99 . The guiding sleeve  22  is provided with a plurality of guide slits  24 . Each guide slit  24  forms a nose end  240  and a tail end  249 . In the drawings the guide slit  24  is shown as a longitudinal through opening in the wall of the guiding sleeve  22 . The guide slit  24  is complementary to the guide pin  351 . The free end  40  is provided with a dog  411  which forms a widening of a straight portion  46  of the expansion piston  4 . The dog  411  is provided with a front dog shoulder  410  which abuts an internal contact face  221  in the front portion of the guiding sleeve  22 . The dog  411  is further provided with a rear dog shoulder  419 , as best seen in  FIGS. 8 and 18 . 
     In the figures the expansion piston  4  is shown as comprising a front piston body  41  and a piston connector  43 . The front piston body  41  and the piston connector  43  is connected at a piston joint  45 . In an alternative embodiment, the expansion piston  4  may be formed as one piece of material. 
     The front piston body  41  comprises an expansion cone  47  that tapers towards the free end  40 . When the expansion tool  1  is in the inactive, retracted state, the slimmest portion of the expansion cone  47  is located at the front end of the expansion body  3 , as shown in  FIGS. 7 and 9 . The surface of the expansion cone  47  forms an angel “α” with respect to the central axis  99 . 
     The straight portion  46  extends between the expansion cone  47  and the dog  411 . The straight portion  46  has a substantially constant diameter. 
     The expansion cone  47  is optionally provided with a plurality of axially oriented expansion grooves  48 . The number of expansion grooves  48  corresponds with the number of arm extensions  35 . Each arm extension  35  is optionally provided with a guiding protrusion  38  which projects from the inclined face  371 . The guiding protrusion  38  fits complementary in the expansion groove  48 . The expansion groove  48  extends from the rear portion of the expansion cone  47  to the front portion of the expansion cone  47 . 
     The piston connector  43  is in a mid-portion provided with an assembly cone  439  which tapers towards the free end  40 . At a rear end the assembly cone  439  forms a cone shoulder  433 . The cone shoulder  433  abuts a rim  53  of the holding sleeve&#39;s  5  front portion  50  when the expansion tool  1  is in the retracted position as shown in  FIGS. 7, 10 and 14 . The widest diameter of the assembly cone  439  corresponds to the outer diameter of the front portion  50 . 
     The inner release sleeve  51  is at a rear end shown provided with a fixed stop sleeve  75  around the circumference of the inner release sleeve  51 . The stop sleeve  75  forms a stop sleeve rim  751  facing towards the leading end  19  as shown in  FIG. 15 . 
     The outer release sleeve  7  surrounds the inner release sleeve  51  when the expansion tool  1  is in both its inactive, retracted position as shown in  FIG. 7  and in its active, expanded position as shown in  FIG. 12 . The release sleeve  7  is axially displaceable relative to the release sleeve  51 , and the release sleeve  7  is fastened to the holding sleeve  5  with at least one shear pin  71 . A plurality of shear pins  71  are shown in the figures. The release sleeve&#39;s  7  wall  72  is at the front end portion thicker than the remaining portion of the wall  72 . The thicker wall portion forms a support for the shear pins  71 . The thicker wall portion forms a release shoulder  73  which faces the rear portion  10 , see  FIG. 10 . 
     The wall  72  is at a rear end formed with an internal stroker connector  80  as shown in  FIGS. 7, 12 and 17 . 
     The expansion arms  31  holding portions  311  are guided into the assembly groove  509  by sliding each holding portion  311  over the assembly cone  439 , further rearwards over the outer surface of the front portion  50  and into the assembly groove  509 . When all expansion arms  31  are correctly positioned, the adapter sleeve  6  is displaced rearwardly over the expansion arms  31  to encompass the rear ends  319 . The adapter sleeve  6  is releasable fastened to the holding sleeve  5  with screws. The expansion arms  31  are dismantled by first releasing the adapter sleeve  6  and displace the adapter sleeve  6  forwardly over the expansion arms  31 . By turning a dismantling screw  313 , see  FIGS. 10 and 20 , the holding portion  311  is lifted out of the assembly groove  509  and the expansion arm  31  is displaced forwardly over the outer surface of the front portion  50  and the assembly cone  439 . 
     The guiding sleeve  22  surrounds the arm extensions  35  from the guide pins  351  to the expansion arm&#39;s  31  front end  310 , when the expansion tool  1  is in its inactive, retracted state as seen in  FIG. 7 . In the inactive, retracted state, each guide pin  351  is positioned at the nose end  240  of the respective guide slit  24 . 
     The expansion tool  1  is connected to the power source  8  such as a stroker  82  at the stroker connector  80 . The expansion piston  4  is connected to the stroker&#39;s stroking organ (not shown) at the stroker organ connector  81 . Activation of the stroker organ in an axially direction towards the leading end  19  will displace the expansion piston  4  axially forwards towards the leading end  19  as well. The cap  20  and the guiding sleeve  22  are both fixed to the free end  40  and will also be displaced axially with the same speed as the expansion piston  4 . The outer sleeve  7 , the holding sleeve  5 , the expansion arms  31 , the expansion body  3  and the arm extensions  35  are all fixed to the stroker  82  and will not be displaced axially. The guide pins  351  are displaced axially within the guide slits  24  from the nose end  240  towards the tail end  249  of each of the guide slits  24  when the guiding sleeve  22  is displaced forward. 
     As the expansion piston  4  is displaced axially forwards, the expansion cone  47  abuts the wedge portions  37  such that the wedge portions  37 , the expansion arms  31  front ends  310 , the arm extensions  35  rear ends and the expansion elements  33  are displaced radially outwards. This is best seen in  FIGS. 4, 12-14 . 
     The expansion cone  47 , the inclined face  371  of the wedge portion  37 , the inclined face  355  of outer side of the arm extension  35 , and the internal face of the guiding sleeve  22  all form an angle “α” with reference to the centre axis  99 . As a result, the expansion elements  33  are displaced radially outwards with the same increase in radius from the centre axis  99  at the front end surface  330  and at the rear end surface  339  of the expansion elements  33 . In other words, the outer surfaces  333  of the expansion elements  33  are parallel to the centre axis  99  when the expansion tool  1  is in the retracted state, when the expansion tool  1  is in the fully expanded state and when the expansion tool  1  is between the retracted state and the fully expanded state. 
     The axial displacement distance of the stroker organ is precisely determined by known means such as a stroker position controller. The radial displacement distance of the expansion elements  33  is an exact function of the stroker organ&#39;s displacement distance. 
     The maximum axial displacement distance of the stroker organ is determined by the stroker&#39;s construction. An internal stop shoulder (not shown) within the stroker impede further axial forward displacement. The length of each guide slit  24  is longer than the travel distance of the guide pin  351  as shown in  FIGS. 12 and 13 . In addition the length of each guiding groove  48  is adapted to the guiding protrusion  38  such that the guiding protrusion  38  will not abut the front end and the tail end of the guiding groove  48 , as shown in  FIGS. 7, 9, 12 and 14 . 
     The guiding protrusions  38  positioned in the guiding grooves  48  secure that the expansion arms  31 , the arm extensions  35 , the wedge portions  37  and the expansion elements  33  are displaced strictly in the radial direction. 
     The expansion arms  31  front ends  310  are displaced radially outwards by the forward movement of the expansion piston  4 . The expansion arms  31  holding portion  311  at the rear end  319  are locked in the radial direction by the adapter sleeve  6 . Thus the expansion arms  31  are bent outwards without any distinct axis of rotation. The outward displacement of the expansion arms  31  front ends  310  creates a tension in the expansion arms  31 , and this tension will assist in an inward radial displacement of the expansion arms  31  when the expansion piston  4  is retracted towards the rear portion  10 . 
     The stroker  82  and the expansion tool  1  is positioned in a tubing  91  in which a tube portion has been constricted or indented due to a damage  95 . The stroker  82  and the expansion tool  1  may be positioned by a wire line or by a wire line operated tractor as known in the art. When the expansion body  3  is positioned in the upper end of the damage  95 , i.e. the end closest to the surface opening of the tubing  91 , the stroker  82  may optionally be anchored to the internal tube wall  97  by slips  83 , as known in the art. The stroker organ is activated, the expansion piston  4  is displaced axially while the expansion elements  33  are displaced radially and forces the constricted tube wall radially outwards. The expansion elements  33  are not displaced axially when they are displaced radially. The expansion piston  4  may be displaced axially to a desired position, possibly to its maximum axially displacement, and the expansion elements  33  may consequently be displaced radially to a desired radial position, possibly to their maximum radial displacement. Thereafter, the expansion piston  4  is retracted rearwards to its passive position by the stroker organ. 
     The guide sleeve  22  is fixed to the expansion piston  4 . When the expansion piston  4  is retracted rearwards, the guide sleeve  22  is displaced rearwards towards the expansion body  3 . A rear end portion  229  of the guide sleeve  22  abuts the inclined faces  355  at the outside of the arm extensions  35  and will in a gliding manner force the arm extensions  35  and thereby the expansion arms  31  and the expansion elements  33  inwards towards the centre axis  99  when the guide sleeve  22  is displaced towards the expansion body  3 . 
     When the expansion tool  1  is in its retracted position, the slips  83  are released, the stroker  82  is slightly displaced further into the damage  95  in a repair direction, and the method is repeated. The displacement in the repair direction may be equal to the length of the expansion elements  33 , or the displacement may be shorter. The method is repeated until the expansion body  3  has been displaced completely through the damage  95 . 
     Optionally the expansion elements  33  may finally be radially displaced to a position where the external circumference of expansion elements  33  is somewhat less than the created internal free diameter of the repaired, or partly repaired, damaged tube portion. The stroker  82  and the expansion tool  1  are withdrawn and the expansion elements  33  pass the damaged tube portion in the opposite direction of the repair direction. Thereby it is checked that there is free passage through the damage  95  for the expansion body  3 . 
     The stroker  82  and the expansion tool  1  are withdrawn to the surface. If necessary, the expansion elements  33  are replaced with other expansion elements  33  with a larger thickness as shown in  FIG. 6 . The external circumference of the expansion body  3  thus becomes larger. The external circumference of the expansion body  3  may be larger than the external circumference of the holding sleeve  5 , or the adapter sleeve  6 , or the release sleeve  7 , as shown in  FIG. 6 . The external circumference of the holding sleeve  5 , the adapter sleeve  6 , and the release sleeve  7  may the same. The method is then repeated, if necessary several times with further replacements of thicker expansion elements  33 . A final check is performed with the expansion elements  33  displaced radially to somewhat less than the final internal free diameter of the tube portion, which is now without the damage  95 . 
     The method allows for a gentle repair of a damaged portion of a tube  93 . Brute force in the axial direction of the tube  93  is completely eliminated. The tube  93  is not subject to any torsion from the expansion tool  1 . 
     In case the stroker  82  is subject to a failure, the stroker organ may be locked in an active position without any means to retract the stroker organ towards the rear portion  10 . The expansion cone  47  will press the expansion elements  33  towards the inside of the tubing  91  and the expansion body  3  will act as an anchor that cannot be released. In such a case the expansion tool  1  is released by an emergency procedure. The stroker  82  is pulled rearwards until the shear pins  71  break. The outer release sleeve  7  is pulled rearward relative to the inner release sleeve  51 , as shown in  FIGS. 5, 17 and 21 . The outer release sleeve  7  is pulled rearward until the stop sleeve rim  751  abuts the release shoulder  73 . The cone shoulder  433  will in addition abut the rim  53  of the holding sleeve front portion  50  as shown in  FIG. 20 . The stroker organ will keep its relative position to the stroker  82 . However, the stroker  82  and the outer release sleeve  7  is displaced axially relative to the expansion body  3 . The expansion piston  4  is fixed to the stroker organ and will thus also be displaced axially relative to the expansion body  3 . The expansion cone  47  will no longer support the wedge portions  37  and the expansion elements  33  are free to move towards the centre axis  99 . The guiding sleeve  22  is displaced together with the expansion piston  4 . The rear end portion  229  of the guide sleeve  22  abuts the inclined faces  355  at the outside of the arm extensions  35  and will in a gliding manner force the arm extensions  35  and thereby the expansion arms  31  and the expansion elements  33  inwards towards the centre axis  99 . The expansion tool  1  is thereby released and the stroker  82  and the expansion tool  1  can be withdrawn to the surface for repair. The stroker  82  may be pulled rearwards by jarring. 
     It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “α” or “an” preceding an element does not exclude the presence of a plurality of such elements. 
     The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.