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FIELD OF THE INVENTION 
       [0001]    The present invention relates to an actuator assembly for positioning in a well to actuate a downhole tool. More particularly, this invention relates to a hydraulically powered actuator assembly for suspending in the well from a workstring and producing high forces suitable for radially expanding a downhole tubular. 
       BACKGROUND OF THE INVENTION 
       [0002]    Various types of downhole actuators are used for operating specific downhole equipment in a well. Actuators may be hydraulically powered or electrically powered, or may be powered from axial or rotational forces transmitted to the actuator by a workstring. Some downhole actuators are powered by a pyrotechnic charge. 
         [0003]    Various types of tools have been proposed for expanding a solid tubular downhole. Many of these tools utilize an expander which is moved axially through the tubular and is powered by hydraulic pressure in the tubular behind the expander. One of the problems with this technique is that the expanded tubular is inherently subject to high fluid pressure as the expander moves axially through the tubular. Leaks in the expanded tubular thus decrease the effectiveness of the technique, and the possibility of leaks reduces the recommended fluid pressure since there is a risk that a leak may prevent movement of the expander. If a leak prevents further movement of the expander, limited options are available to circumvent the problem, and the well may need to be abandoned. 
         [0004]    Some tools have used hydraulically actuated expanders with fluid power being supplied to the actuator by a workstring separate from the tubular being expanded. As disclosed in U.S. Pat. Nos. 6,763,893, 6,814,143, 7,225,880, and 7,278,492, the actuator tool may include a series of pistons which move axially to move a tool mandrel with respect to an outer housing of the tool. The pistons are arranged hydraulically in a series, so that a significant axial force required for tubular expansion is obtained with conventional fluid pressure within the workstring and within the tool. By proper sizing, an actuator from 20 to 30 feet in length is able to generate high expansion forces over a stroke length of from 2 to 5 feet. If an additional length of tubular is to be expanded, the tool may be recocked and restroked a second or multiple times. 
         [0005]    The disadvantages of the prior art are overcome by the present invention, in an improved actuator and a method of assembling the actuator as hereinafter disclosed. 
       SUMMARY OF THE INVENTION 
       [0006]    In one embodiment, a hydraulically powered downhole tool axially moves an expander in a well to radially expand a downhole tubular. A tool mandrel is axially secured to the expander, and a plurality of pistons are movable relative to the tool mandrel and are mechanically interconnected by an outer sleeve or housing of the tool radially exterior of the tool mandrel. One or more slips supported by the outer sleeve engage the interior wall of the well to temporarily fix an axial position of the outer sleeve in the well. Both the tool mandrel and the outer sleeve include a plurality of sections each having a lower end for interconnection with an upper end of another section. A retainer is provided for supporting each of the outer sleeve sections axially above a respective lower outer sleeve section, thereby exposing mandrel sections for assembly. 
         [0007]    According to one embodiment of a method of the invention, the tool is assembled by supporting each of the outer sleeve sections axially above a respective lower sleeve section, thereafter assembling the exposed mandrel section, thereafter axially lowering the outer sleeve section over the mandrel, and thereafter assembling the outer sleeve section and respective lower sleeve section. 
         [0008]    These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a cross-sectional view of an upper portion of a hydraulically actuated tool being assembled at the surface of a well. 
           [0010]      FIG. 2  is a cross-sectional view of a lower portion of the actuator tool. 
           [0011]      FIG. 3  illustrates hydraulically actuated slips for the tool. 
           [0012]      FIG. 4  illustrates a lower portion of the tool with an expander for radially expanding a downhole tubular. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0013]    In various applications, expanders are used to radially expand a length of a downhole tubular so that, for example, the tubular is expanded from a run-in internal diameter of 6⅞ inch to an expanded internal diameter of 8.4 inches. Expansion of a downhole tubular may be desirable for a mono-bore well system, and may also be used to expand shorter lengths of a tubular for a seal patch, or for a liner hanger operation. In some mono-bore applications, a relatively short length of a tubular may be expanded by a hydraulically powered downhole tool, and thereafter a substantially longer length of the tubular is expanded by exerting an upward pull on the drill pipe workstring. 
         [0014]    If the tubular being expanded is deep in the well, and particularly if the well has deviations which cause the workstring to engage the side of the well during an axial pulling operation, tubular expansion by pulling on the workstring may not be feasible. In other applications, the drilling rig or the workstring itself is not able to withstand the high pulling force that must be exerted on the expander to cause the desired tubular expansion. 
         [0015]    According to the present invention, an improved actuator is provided for axially moving an expander a substantial axial distance of greater than about 1 meter during stroking of the hydraulic actuator. If the longer expansion of the tubular is required, the tool may be actuated, the tool moved and reset, and the actuator tool again stroked so that a combined length of expanded tubular may be more than 6 meters. Any desired longer length of tubular may be expanded by repeated stroking operations. 
         [0016]    Referring now to  FIG. 1 , an upper portion of an expander tool is shown for suspending in a well, which typically includes an existing casing (not shown in  FIG. 1 ). The actuator tool  10  may be suspended in the well from a drill pipe or other workstring  14 , which is shown threadably connected to top sub  16 . A threaded connector  18  is shown not yet threaded to the sub  16 , and is shown connected to the tool mandrel  20 , which has a central bore fluid passageway  22  therein. Sub  16  and connector  18  are shown threadably disengaged in  FIG. 1 , although the functionally similar components  32  and  34  are shown connected in  FIG. 2 . The tool  10  as shown in  FIG. 1  also includes an outer sleeve or housing  24  which includes threads  25  as shown in  FIG. 1  for threadably connecting to outer piston  26 . Hydraulic pressure in the workstring and thus in the passageway  22  may pass through gap  30  in mandrel  20 , thereby axially moving the sub  16  and tool mandrel  20  relative to the outer sleeve  24  and the outer piston  26 . 
         [0017]    An intermediate portion of the tool as shown in  FIG. 2  illustrates the lower end of mandrel  20  threaded to male connector  32 , which is threadably connected to the female connector  34 . The hydraulic portion of the tool  10  may have a total length of 100 meters or more. The tool may be sequentially assembled at the well site by interconnecting a lower end of an inner mandrel assembly with a partially assembled inner mandrel. Threads on the inner mandrel sections may be engaged with a tong or other conventional equipment, thereby making up, for example, the connection between  32  and  34 . During this assembly operation, the outer sleeve section  24  may be raised above the location for the inner mandrel connection, and may be retained in that upward position by a suitable clasp or latch  28 , as shown in  FIG. 1 . With the outer sleeve raised so as not to interfere with makeup of the inner mandrel connection, the inner mandrel may be made up, and the latch  28  then disengaged and the outer sleeve section lowered so that threads  36  on the lower end of the outer sleeve section as shown in  FIG. 2  come into mating engagement with the threads  38  on the OD of the outer piston  26 . Simultaneously with the makeup of threads at the lower end of the outer sleeve section, the upper end of a sleeve section threaded at  37  mates with threads  29  at the lower end of outer piston  26 , as shown in the lower portion of  FIG. 2 . 
         [0018]    In  FIG. 1 , the tool mandrel  20  is shown disassembled, and the associated outer sleeve or housing is raised for assembly of the mandrel  20 , which is shown in the upper portion of  FIG. 2 . In  FIG. 2 , the lower mandrel connection is made up, and the associated outer sleeve has been lowered over this connection and is also made up. The latch  28  is removed in  FIG. 2 , although a threaded lock for receiving a latch bolt is shown. The outer piston  26  is then securely engaged with the section of the outer sleeve  24  and is in sealing engagement with the inner mandrel  20  due to seals  42 . Similarly, the female connector  34  includes inner threads  44  to interconnect a top section of the inner mandrel with connector  34 , which has one or more outer seals  46  for sealing engagement with the interior of the outer sleeve section  24  when it is lowered in place. The female connector  34  thus effectively forms an inner piston which is secured to the tool mandrel and sealed to the outer sleeve, while the outer piston  26  inversely is connected to the outer sleeve and is sealed to the inner tool mandrel. Those skilled in the art shall appreciate that a plurality of such pistons and piston assemblies may be provided in various tool sections which are assembled sequentially at the well site. Threads  29  or other members may be used instead of latch  28  to retain the outer sleeve temporarily in a raised position for exposure of the components of an inner mandrel connection, so that after the inner mandrel connection is made during an assembly operation, the outer sleeve may be lowered and the outer sleeve sections then connected. 
         [0019]    The running tool mandrel, the outer sleeve, and the pistons thus define variable size hydraulic cavities. A series of mandrel sections, outer sleeve sections, and inner and outer pistons may be provided in the hydraulic sections of the tool, so that axial forces effective stack to create a desired high expansion force. It is a particular feature of the invention that the tool as disclosed herein may generate a hydraulically generated axial force in excess of 1 million pounds, and preferably in excess of 1.5 million pounds, over a relatively long length of approximately 7 meters. 
         [0020]      FIG. 3  depicts a slip portion of the tool for fixing the axial position of the outer sleeve  24  in place during a tubular expansion operation. The outer sleeve  24  as shown in  FIG. 1  is thus structurally interconnected, e.g., threads  51 , with the slip housing  52  shown in  FIG. 3 , which includes one or more cone sections  54  for mating with similarly tapered cone sections on slips  56  with exterior teeth  57 . Axial movement of the inner mandrel  20  relative to the housing  52  interconnected with the outer sleeve  24  thus forces the slips  56  radially outward and into biting engagement with the liner or other tubular  12 . 
         [0021]    Slips  56  are prevented from moving downward due to engagement with sleeve  74 . Collet mechanism  76  is provided between the OD of mandrel  20  and the ID of sleeve  74 . Sleeve  74  thus includes suitable windows each for receiving a respective slip. Collet mechanism  76  may include upper and lower heads, and prevents the slips and sleeve  74  from moving downward with the outer sleeve  24  and slip housing  52  during the slip setting operation. The collets  76  are positioned about the mandrel  20  and releasably engage a groove or stop on the mandrel to hold the slips  54  in an upward position, so that the slips do not move downward while being set. The collets  76  may open radially outward after the slips are set, and allow the tool to be reset when the setting assembly is raised. The action of the collet mechanism is thus repeatable, thereby allowing the tool to be repeatedly stroked, recocked, and then restroked. 
         [0022]    Keys  53  are provided in the slip housing  52  and cooperate axially between slips  56  and sleeve  74  to allow for rotation of sleeve  74  relative to slip housing  52 . Keys  80  are also provided at the lower end of sleeve  74 , and slide within axially extending slots or grooves  72  in the inner mandrel  20  to ensure rotation of the sleeve  74  relative to the mandrel  20 . Thus, rotation applied to outer sleeve  24  is transmitted to mandrel  20 . The slips may be set by dropping a ball on a seat  188  to raise the internal pressure within the mandrel  20  until the increased pressure forces the pistons axially apart, thereby generating a high axial force to set the slips and move the expander. Once the slips are set, the mandrel  20  may be moved upward relative to the slips during the tubing expansion operation. 
         [0023]      FIG. 4  depicts a tubular  12  which will be radially expanded by the hydraulic actuator moving the expander  48  upward, thereby radially expanding the tubular  12 . 
         [0024]    A safety joint (not shown) with left-hand threads may allow for latching of the tool with the downhole expander at the lower end of the tool. Left-hand threads allow right-hand rotation of the workstring for drilling operations and, if necessary, left hand rotation to disengage the tool from the downhole expander. The upper half of the safety joint  173  is threaded to inner mandrel  72  and the safety joint lower half threaded at  172  to mandrel  170 . 
         [0025]    The lower end of tube  204 , when positioned as shown in  FIG. 4 , is configured to rotate the lower end of the tool, thereby reliably rotating the bit. During a drilling operation, the lower end of the flow tube  204  which passes through the interior of the expander  48  may be sealed to the lower housing  224 , thereby providing a substantially sealed flow path to the bit. 
         [0026]      FIG. 4  illustrates one embodiment of a lower portion of an expansion tool according to the present invention which is adapted for a liner or other tubular drilling operation. The lower portion of the tool is shown in  FIG. 4  may have an upper portion which is substantially as described above. The tubular or liner  12  with the expander  48  supported adjacent a lowermost end of the liner, the mandrel  200 , and the housings  222  and  224 , with a bit or reamer  221  at the end thereof, may first be lowered in a well, then the remainder of the tool lowered so that keyed collet heads  194  on the lowered tool connect with the threads  198  on the mandrel  200 . The liner  12 , once expanded, may have its upper end within a casing or other downhole tubular or uncased wellbore (not shown in  FIG. 4 ). 
         [0027]    Sleeve  174  threaded to mandrel  170  has lower clutch teeth  176  circumferentially arranged thereon. The clutch teeth  176  mate with and thus engage clutch teeth  177  at the upper end of mandrel  200 . A radially external surface of the mandrel  200  includes axially extending splines  182 , which mate with similar splines  180  on the modified liner section  178 . The splines  180  on the liner section  178  similarly extend axially, and the upper and lower ends of the splines may include conventional tapers so that the mandrel  200  effectively slides along the splines while torque is transferred from the mandrel  170  to the mandrel  200 , and from the mandrel  200  to the liner  12  to be subsequently expanded, thereby allowing the unexpanded liner and the tool to be rotated together as an assembly. High torque in the drill pipe workstring  14  and thus in the mandrel  20  may be transmitted radially outward from the inner mandrel to the tubular  12 . The mandrel  170  includes a central bore  186 , and a selectively sized seat  188  for subsequently receiving a ball or other plug member. 
         [0028]    Mandrel  170  in turn is threaded at  192  to mandrel  190 . When the tool is latched into the liner as shown in  FIG. 4 , the upper end of mandrel  200  circumferentially surrounds and is axially slidable relative to the lower end of the mandrel  170 , so that upper end of mandrel  200  is positioned circumferentially about the lower end of mandrel  170 . Collet fingers  196  with lower heads  194  are threaded at  198  to the mandrel  200  when the tool is assembled downhole, as discussed above, and may slide axially relative to mandrel  170  to allow the clutch teeth to be disengaged when the work string  12  is subsequently picked up. Flow through passages  202  extend from the inside of the liner section  212  to the exterior of mandrel  190  to allow for drainage and prevent an undesirable pressure head in the tool. 
         [0029]    Tube  204  may thus be threaded to and sealed to mandrel  190 , and accordingly moves axially with mandrel  190 . Expanding members  48  are supported adjacent the lower end of liner section  178 , and may be threaded to the liner section as disclosed in U.S. application Ser. No. 11/803,389, hereby incorporated by reference. Lower housing  222  sandwiches the expander  48  between lower inwardly formed section  228  of the liner  212  and housing  222 . For the embodiment depicted in  FIG. 4 , sleeve  230  may be externally threaded to internal threads on section  228  of the liner. Sleeve  230  is prevented from moving upward by engagement with shoulder  232  on mandrel  200 , thereby rotating mandrel  200  with the lower housing  222 . Sleeve  230  thus acts as a positive stop to prevent upward movement of the expander  48  and the liner  212  prior to activation of the hydraulic power section of the tool. As shown in  FIG. 4 , the section  228  of the liner is radially inwardly formed to reduce the thickness of the sleeve  230  without increasing the thickness of the liner. 
         [0030]    Housing  222  is threaded to the lower end of mandrel  200 , and to the upper end of bit housing  224 . Lower threads  220  on housing  224  are provided for conventionally receiving a bit or reamer  222  for drilling the hole in response to liner rotation. Tube  204  thus includes a central bore about axis  218  which supplies fluid to the bit  222 . Tube  204  remains sealed to the housing  224  during axial movement of the tube. 
         [0031]    To conduct a tubular drilling or reaming operation, the tool as shown in  FIG. 4  may be positioned within the liner  12  after the liner is run at least partially in the hole, then the liner and the tool lowered to a drilling depth. When the tool is subsequently picked up, fluid from within the interior of the tool may drain out through the ports  202  in housing  222 , so that the entire column of fluid does not have to be lifted to the surface with the tool. A seal  223  between tube  204  and the housing  224  ensures the supply of a high pressure fluid to the bit  222  when the tool is positioned as shown in  FIG. 4 . 
         [0032]    The mandrel  200  which surrounds the lower end of mandrel  170  may be threaded at  216  to housing  222 . Mandrel  190  is rotated with the mandrel  170 , thereby also rotating tube  204 . Torque may be transmitted from the mandrel  200  to the bit or reamer  222  without torque having to be transmitted through the expander  48 . 
         [0033]    After the liner  212  or other tubular drilling operation is complete, the drill pipe  12  may be picked up, thereby lifting the mandrel  170  and disengaging the clutch  175 . Thereafter, the tool may be actuated, as explained above, so that the expander  48  is forced upward while the liner  12  remains held in place by slips  56 , thereby expanding a length of the liner during an actuator stroking operation. As previously discussed, the slip resetting and stroking operation may be repeated until a desired length of the liner is expanded, after which time the liner is fixed at its lower end in the well, and an upward force on a drill pipe may be used to expand upper sections of the liner without stroking the tool. 
         [0034]    The tool as disclosed herein may be recocked during an upward stroking operation, then the hydraulic section activated to set the slips and to pull up on the expander and expand a length of the tubular. The tool may be used to expand a tubular in an open hole operation, and may also be used to press a tubular tightly against the wall of another tubular in a cladding operation. Moreover, the technique is able to reliably expand overlapping joints of pipe sections which are expanded, thereby providing a monodiameter or continuous ID bore application. 
         [0035]    The above application discloses elongate components, such as a tool mandrel and an outer sleeve exterior of the tool mandrel, which in practice are each a series of interconnected components, so the tool mandrel and the outer sleeve are each an assembly of a plurality of interconnected tool mandrel sections and a plurality of outer sleeve sections. Accordingly, each of these terms as used herein should be understood to include a plurality of sections which together form the elongate components. 
         [0036]    Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.

Summary:
A hydraulically powered downhole tool includes a tool mandrel ( 20 ) having an interior bore ( 22 ), and a plurality of pistons ( 26 ) each axially movable relative to the tool mandrel and mechanically interconnected by an outer sleeve ( 24 ) exterior of the tool mandrel. A plurality of mandrel sections and a plurality of outer sleeve sections each have a lower end for interconnection with an upper end of a corresponding member. A retainer ( 28 ), ( 29 ) is provided for supporting each outer sleeve section above a respective lower sleeve section, thereby exposing mandrel sections for vertical assembly.