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BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     Embodiments of the invention generally relate to expanding tubulars in a wellbore. More particularly, embodiments of the invention relate to the expansion of the tubulars enhanced by use of compressive forces applied to the tubulars.  
         [0003]     2. Description of the Related Art  
         [0004]     Hydrocarbon and other wells are completed by forming a borehole in the earth and then lining the borehole with pipe or casing to form a wellbore. After a section of wellbore is formed by drilling, a section of casing is lowered into the wellbore and temporarily hung therein from the surface of the well. Using apparatus known in the art, the casing is cemented into the wellbore by circulating cement into the annular area defined between the outer wall of the casing and the borehole. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas of the formation behind the casing for the production of hydrocarbons.  
         [0005]     Recent developments in the oil and gas exploration and extraction industries have included using expandable bore lining tubing. Apparatus and methods are emerging that permit tubulars to be expanded in situ. The most common expansion apparatus is a cone or a swedge. Some expansion apparatus include expander tools which are fluid powered and are run into the wellbore on a working string. These hydraulic expander tools can include radially extendable members which, through fluid pressure, are urged outward radially from the body of the expander tool and into contact with a tubular therearound. As sufficient pressure is generated on a piston surface behind these extendable members, the tubular being acted upon by the expansion tool is expanded past its point of plastic deformation. In this manner, the inner and outer diameter of the tubular is increased in the wellbore. By rotating the expander tool in the wellbore and/or moving the expander tool axially in the wellbore with the extendable members actuated, a tubular can be expanded along a predetermined length in a wellbore. Other methods include using hydraulic pressure inside the tubular to expand the tubular past its point of plastic deformation.  
         [0006]     Multiple uses for expandable tubulars are being discovered. For example, an intermediate string of casing can be hung off a string of surface casing by expanding a portion of the intermediate string into frictional contact with the lower portion of surface casing therearound. This allows for the hanging of a string of casing without the need for a separate slip assembly. Additional applications for the expansion of downhole tubulars exist. These include the use of an expandable sand screen, employment of an expandable seat for seating a diverter tool, and the use of an expandable seat for setting a packer.  
         [0007]     There are problems associated with the expansion of tubulars. One particularly associated with rotary expander tools is that the rotary expansion of the tubular makes the wall of the tubular thinner. This then increases the overall length of the tubular which is problematic when trying to determine location in the well. Further, expandable tubulars are currently limited to an expansion of 10%-25% of their original diameter using existing expansion techniques that are constrained by the tubular burst pressure and friction applied thereto. Also when using hydraulic pressure to expand the tubular, due to the high pressure required, weaknesses in the tubular are exploited limiting the amount of expansion that can be achieved before the tubular ruptures.  
         [0008]     There exists a need for an improved method and apparatus for expanding casing or other tubulars within a wellbore. Further, there exists a need for method and apparatus for expanding a tubular which requires less outward force or hydraulic pressure on the tubular with increased expansion. There exists yet a further need for an apparatus and method for expanding a tubular which reduces the risk of uneven expansion of the tubular by reducing the amount of force needed for the expansion operation. Further, there exists a need for a method of expanding a tubular and accurately controlling the location of the tubing.  
       SUMMARY OF THE INVENTION  
       [0009]     Embodiments of the invention generally relate to methods and apparatus for expanding tubulars in a wellbore enhanced by compressive force applied to the tubulars. According to one aspect of the invention, a method of expanding a tubular in a wellbore includes positioning the tubular in the wellbore, affixing at least two locations spaced along a length the tubular to desired locations in the wellbore, and expanding a portion of the tubular between the two locations outward radially with a rotary expander tool, such that the tubular is in compression while expanding. According to another aspect of the invention, methods and apparatus provide for expanding a tubular run into a wellbore by applying a compressive force to at least a portion of the tubular and applying fluid pressure to an inside surface of the tubular to expand the tubular to a larger diameter. The tubular can be located proximate to a window in the wellbore such that expanding the compressed portion of the tubular covers the window and may form a bulge extending through the window. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
         [0011]      FIG. 1  is a sectional view of a wellbore having a tubular disposed therein for expansion according to aspects of the invention;  
         [0012]      FIG. 2  is a sectional view of a tubular and an expansion assembly attached to a work string and disposed in a wellbore;  
         [0013]      FIG. 3  is a sectional view of the tubular of  FIG. 2  after expansion with hydraulic pressure applied to an inside surface thereof;  
         [0014]      FIG. 4  is a sectional view of the tubular of  FIG. 2  after completing expansion with hydraulic pressure;  
         [0015]      FIG. 5  is a sectional view of the tubular of  FIG. 4  after being expanded in a wellbore with a multilateral junction;  
         [0016]      FIG. 6  is a sectional view of the tubular of  FIG. 5  after being fully expanded;  
         [0017]      FIG. 7  is a sectional view of the multi-lateral junction of  FIG. 5  completed with the tubular expanded and drilled out; and  
         [0018]     FIGS.  8  to  11  are schematic illustrations of steps in the process of lining a bore in accordance with embodiments of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0019]      FIG. 1  illustrates a cross-sectional view of a wellbore  100  and a tubular  110  disposed therein. The tubular  110  can be casing or any other type of tubular used in downhole drilling operations, such as a liner or a patch. First and second fixed locations  120 ,  130  spaced apart along the length of the tubular  110  substantially prevent axial movement of the tubular  110  in the wellbore  100  such that the distance between the fixed locations  120 ,  130  cannot vary. The fixed locations  120 ,  130  can be achieved by any method or combination of methods known in the art, such as by using anchors or slips on an outside of the tubular  110  to engage a surrounding surface, by selectively expanding the tubular  110  at one or both of the fixed locations  120 ,  130  into frictional contact with the surrounding surface or by locating the bottom of the tubular  110  on a stop such as a plug, a packer or a bottom of the borehole (see,  FIGS. 9-12 ). In the embodiment shown in  FIG. 1 , the fixed locations  120 ,  130  have been expanded to place the outside surface of the tubular  110  into contact with a surrounding surface. Expansion of the fixed locations  120 ,  130  can be performed by either using a rotary expander tool  140  or additional expander(s) (not shown), such as one or more inflatable members or packers, capable of selective expansion at the fixed locations  120 ,  130 . The fixed locations  120 ,  130  create an annular space between the tubular  110  and the wellbore  100 . To facilitate expansion of the tubular  110 , fluid in the annular space can escape through apertures (not shown) in a surrounding casing and into a formation, through apertures in the tubular  110 , across flow paths at one or both of the fixed locations  120 ,  130  such as by only partial circumferential expansion, and/or directly into the surrounding formation when in an open wellbore. For example, the tubular  110  may serve as a patch to remedy excessive mud loss in an open hole such that fluid from the annular space can easily be pushed into the formation.  
         [0020]     U.S. Pat. No. 6,457,532, which is herein incorporated by reference in its entirety, discloses an exemplary rotary expander tool that can be used as the rotary expander tool  140  schematically illustrated in  FIG. 1 . The rotary expander tool  140  operates to expand the length of the tubular  110  between the fixed locations  120 ,  130 . Typically, the rotary expander tool  140  starts at one fixed location (e.g., the first fixed location  120 ) and progresses to the other fixed location (e.g., second fixed location  130 ) expanding the tubular  110  along the way. If only one location along the tubular is initially fixed, expansion can start a distance from that location to thereby provide the other fixed location prior to the rotary expander tool  140  moving toward the initially fixed location. The tubular need not be placed in compression prior to starting expansion of the tubular  110  between the two fixed locations  120 ,  130  since a compressive load in the tubular  110  develops as expansion with the rotary expander tool  140  progresses. This is due to the fact that use of the rotary expander tool  140  lengthens the tubular  110  by thinning of the tubular wall which, because the fixed locations  120   130  are set to prevent the elongation of the tubular  110 , compresses the tubular  110 . In contrast, a cone used to expand a tubular typically causes the tubular to shorten during expansion such that tension and not compression develops if the cone is used to expand a section between two fixed locations. The compression in the tubular  110  enhances the expansion process by increasing the expansion possible and decreasing the amount of force required by the rotary expander tool  140 .  
         [0021]     Before both of the two fixed locations  120 ,  130  are set, the tubular  110  can optionally be placed in compression either through use of gravity or a mechanical, electrical, or hydraulic device adapted to apply a compressive load on the tubular. Since the tubular  110  is expanded between end points that are fixed, this increases accurate location of the tubular  110  in the wellbore  100 . Thus, this process enables accurate placement of liners, patches and other tubulars in the wellbore without the side effects of having the liner elongate or shorten during expansion.  
         [0022]      FIG. 2  shows a section of the wellbore  100  with a liner  230  and expandable tubing  200 . The expandable tubing  200  can be casing, liner, a patch, or any other type of tubing used in downhole operations for expansion into the liner  230 , casing or an open wellbore.  FIG. 2  depicts the expandable tubing  200  as a patch used for closing an aperture  235  in the wellbore  100  that is lined. The patch can include a seal  256  and an anchoring element  257  on the outside of the expandable tubing  200 .  
         [0023]     The expandable tubing  200  attaches to a work string  210  via a setting tool  220 . The lower end of the expandable tubing  200  attaches to the work string  210  by a carrying mechanism  240  of the setting tool  220 . The carrying mechanism  240  is any suitable temporary connection known in the art such as carrying dogs, collets, threads, latches, slips etc. In one embodiment the carrying mechanism  240  is a set of pre-set slips  231 . The pre-set slips  231  engage the inside diameter of the expandable tubing  200  with a series of teeth  232 . The pre-set slips  231  support the weight of the expandable tubing  200  and the piston assembly. The pre-set slips  231  are held in place by wedges  233  and  234 . Wedge  234  is fixedly attached to the work string  210 . Wedge  233  is attached to a slip release assembly  236 . The slip release assembly  236  connects to a seat  237 . The seat  237  holds a sealing member such as a dart, or ball  270  at its upper end in order to hydraulically seal the work string  210 . The seat  237  connects to the work string  210  with a shear pin  238 . Above the pre-set slips  231  is a lower pressure seal cup  239  for hydraulically sealing the interior of the expandable tubing  200 . At the upper end of the expandable tubing  200 , a compression piston  250  of the setting tool  220  attaches the expandable tubing  200  to the work string  210 . The compression piston  250  has a shoulder  253  which engages the upper end of the expandable tubing  200 . The compression piston  250  moves relative to the work string  210  and a piston base  251 . The piston base  251  fixedly attaches to the work sting  210 , thus as fluid flows in to an annulus  252 , the piston  250  pushes the expandable tubular  200  down relative to the work string  210 . With the lower end of the expandable tubular  200  fixed to the work string  210  by carrying mechanism  240 , the expandable tubular  200  is in compression. More than one compression piston can be used in order to increase the compressive force applied to the expandable tubing  200 , as is known in the art. The carrying mechanism  240  and the compression piston  250  can be adapted to seal the top and bottom of the expandable tubing  200 .  
         [0024]     As illustrated in  FIG. 3 , the work string  210  lowers into the wellbore  100  to a desired location for the expandable tubing  200 . Once at the desired location, the compression piston  250  actuates upon application of hydraulic pressure through the work string  210 , which can be selectively plugged by a stopper, such as a ball  270  dropped onto the seat  237 , a diverter valve such as that disclosed in U.S. patent application Ser. No. 10/954,866 assigned to Weatherford/Lamb, Inc. which is hereby incorporated by reference, could also be used. The compression piston  250  urges the attached top of the expandable tubing  200  toward the carrying mechanism  240 . This places the expandable tubing  200  in compression since the attachment of the top of the expandable tubing  200  via the compression piston  250  permits relative movement between the work string  210  and the expandable tubing  200  while the attachment of the expandable tubing  200  at the carrying mechanism  240  prevents relative axial movement between the lower end of the expandable tubing and the work string  210 . Simultaneously, hydraulic pressure provided through port  245  acts on an inside surface of the expandable tubing  200  to cause radial expansion of the expandable tubing  200  along a length of the expandable tubing  200  between the lower pressure seal cup  239  and an upper pressure seal cup  254 .  
         [0025]     The expandable tubing  200  can utilize changes in material and configuration in order to enhance expansion. In one embodiment, the tubing thickness at the two fixed end points, the piston  250  and carrying mechanism  240  is larger that the expandable tubing  200  wall thickness between the fixed points. Further, in another embodiment the yield strength and/or elastic modulus of the expandable tubular  200  is changed between the fixed points. In another embodiment the expandable tubular  200  is longitudinally corrugated between the fixed points. In yet another embodiment the expandable tubular  200  has a different material than the material at the fixed points. Further, any of these methods can be used in combination to enhance expansion of the expandable tubular  200 . These embodiments ensure the expandable tubular  200  expands from the middle portion first and then outwards toward both ends. This ensures that fluids are not trapped in the annulus between the Expandable tubular  200  and the liner  230 .  
         [0026]     After expansion of the expandable tubing  200  with hydraulic pressure it is necessary to ensure the expandable tubular  200  is secure in the wellbore by pulling or pushing on the work string  210 . The setting tool  220  then releases the expandable tubular  200  at the carrying mechanism  240 . By increasing the hydraulic pressure in the work string  210  the seat  237  shears the shear pin  238 . This causes the slip release assembly  236  to move down which moves the lower wedge  233  down, releasing the pre-set slips  231  as shown in  FIG. 4 . Additionally, an expander  265  (shown schematically) actuates to an extended position having an increased outer diameter. The expander  265  can be any type of expandable cone or hydraulically actuated rotary expander tool, such as those disclosed in U.S. Pat. No. 6,457,532, U.S. patent application Ser. No. 10/808,249 and U.S. patent application Ser. No. 10/954,866, which are hereby incorporated by reference.  
         [0027]      FIG. 4  shows the expandable tubing  200  while the expander  265  completes expansion of the expandable tubing  200  along its entire length. In operation, lowering the work string  210  moves the expander  265  through the expanded section of the expandable tubular  200  and across the end of the expandable tubular  200  where expansion was previously prevented by the carrying mechanism  240 . As the expander  265  moves through the expandable tubular  200 , the expander  265  insures proper expansion and/or further expands the previously expanded length of the expandable tubular  200  and expands the bottom end of the expandable tubular  200 . Accordingly, the previously unexpanded top end of the expandable tubular  200  where expansion was previously prevented due to attachment to the compression piston  250  occurs upon pulling the expander  265  out of the expandable tubular  200  during removal of the work string  210 . For some embodiments, the expander  265  may not be required if it is not desired to expand the ends of the expandable tubular  200  where the expandable tubular attaches to the setting tool  220 . Further, the expander  265  can be arranged to work in conjunction the hydraulic expansion in order to enhance the expansion process. Further, the expander  265  can be attached either below or above the expandable tubular  200  or on another tool and actuated once hydraulic expansion is complete. The work string  210  is removed upon completion of the expansion leaving the expandable tubing  200  in place. Thus, the expandable tubing  200  can be used to patch apertures in the casing, liner or the wellbore itself with no liner. In another embodiment, the unexpanded portions of the expandable tubular  200  could be removed by the apparatus and methods disclosed in U.S. Pat. No. 6,598,678 assigned to Weatherford/Lamb, Inc. or as disclosed U.S. Pat. No. 6,752,215 assigned to Weatherford/Lamb, Inc which are hereby incorporated by reference. This procedure can be done multiple times in the wellbore in order to control production from the formations.  
         [0028]      FIGS. 5-7  depict an embodiment of the invention that utilizes an assembly similar to that illustrated in  FIGS. 2-4 .  FIG. 5  shows the wellbore  100  with a window  310  cut in the side to provide an opening for a lateral junction  320 . An expandable tubing  300  is shown expanded so that it covers the lateral junction  320 . The expandable tubular  300  expands using the methods described above. Thus, the expandable tubing  300  is compressed. While in compression, the expandable tubing  300  is expanded by fluid pressure acting on an inside surface of the expandable tubing to initially expand the expandable tubing  300  up to an inner diameter of the wellbore  100 , as shown in  FIG. 5 . The expansion process continues by further application of hydraulic pressure to cause a wall of the expandable tubing  300  to bulge at the window  310  and enter the lateral junction  320 , as shown in  FIG. 6 . For enhanced expansion, the expandable tubing may comprise any suitable material which can sustain an expansion ratio of greater than 20%. Further, the expandable tubing can be initially longitudinally corrugated in order to facilitate a high expansion ratio. The expander  265  is removed from the wellbore. The lateral junction  320  can then be drilled out using techniques known in the art providing a multi-lateral junction, as shown in  FIG. 7 . A subsequent liner (not shown) can be run into the lateral junction  320  and suspended off of the tubing  300  therein.  
         [0029]      FIGS. 8-11  depict an embodiment of the invention used to line a wellbore  400 .  FIG. 8  shows the lower end of the wellbore  400  including an unlined bore section  410 . Above the unlined section  410 , casing  420  lines the wellbore  400 . As shown, the lower end of the casing  420  includes a larger diameter end section  425 , or bell-end, however, the lower end of the casing  420  can be straight pipe.  
         [0030]     An expandable tubing or liner  430  is run into the wellbore  400  on a work string  440 . The liner  430  is initially coupled to the work string  440  via a setting tool  450 . The liner  430  is located in the wellbore  400  such that the upper end of the liner  430  overlaps the larger diameter casing end section  425 . The lower end of the liner  430  is positioned at the end of the wellbore  400 . The liner  430  itself or a shoe  460  contacts the bottom of the wellbore  400 . Next, weight can optionally be set down on the liner  430 . The weight can be from the length of the work string  440 , or any other method that places the liner  430  in a compressive state.  
         [0031]     As shown in  FIG. 9 , once the liner  430  is in compression, an anchor  470  is set. The anchor  470  can be any type of liner hanger known in the art. With the anchor  470  set, the liner  430  is held in compression between the anchor  470  and the end of the wellbore  400 . For some embodiments, the compressive state, as discussed above with regard to  FIG. 1 , may be caused solely by the expansion process itself and not initially applied to the liner  430  prior to setting of the anchor  470 .  
         [0032]     Next, as shown in  FIG. 10 , a rotary expander tool  480  moves downwardly through the liner  430  to expand the liner  430  to a larger diameter such that the expanded inner diameter of the liner  430  corresponds to the inner diameter of the casing  420 . A more detailed description of the setting tool and expansion tool can be found in U.S. Patent Application Publication No. 2003/0127225, which is herein incorporated by reference in its entirety. The compressive state of the liner  430  enhances the expansion process and requires less force from the rotary expander tool  480  than conventional methods. Once the desired expansion of the liner is complete, the liner  430  can be cemented in place, and the annulus between the liner  430  and the casing  420  proximate the anchor  470  can be sealed.  
         [0033]      FIG. 11  shows creation of a bulge formed monobore shoe, which can be an additional step to the method described in  FIGS. 8-10 . Once the liner  430  is on the bottom of the wellbore  400 , weight is applied to the liner  430  to place the liner  430  in compression. The bottom of the liner  430  is then expanded by fluid pressure applied to the inner surface of the liner  430  to form a bell shaped end  500 . For some embodiments, the material used at the bell shaped end  500  of the liner  430  has a thinner wall thickness than the rest of the liner  430  and/or is shaped pipe in order to facilitate expansion thereof and provide the bell shaped end  500  upon expansion. Further, the bell shaped end  500  may be hydraulically isolated from the rest of the liner such that the fluid pressure is applied to only the bell shaped end  500 . Additional bell shaped ends (not shown) having smaller diameters than the bell shaped end  500  may be located above the bell shaped end  500 . These additional bell shaped ends may be formed by application of a different fluid pressure than applied to the bell shaped end  500  and/or they may be formed of a different material than the bell shaped end  500 . The remainder of the liner  430  can be expanded using any expansion method such as a rotary expansion, a swedge or cone, hydraulic pressure and any methods described above.  
         [0034]     Any of the expandable tubing described above can be longitudinally corrugated tubing or shaped pipe in order to further facilitate expansion. Using shaped pipe or corrugated tubing also reduces the tendency for pipe to buckle. This allows for compression of longer lengths of pipe enhancing the expansion process further.  
         [0035]     Further, the methods described above can be used in any type of down hole tubular expansion including but not limited to liner hangers, packers, straddles, PBRs, drilling-with-liner, etc.  
         [0036]     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Summary:
Methods and apparatus for expanding a tubular with the aid of a compressive force are disclosed. A tubular is run into a wellbore. While the tubular is in a compressive state, the tubular is expanded into its desired form. The expanded tubular can be used for multiple downhole functions such as completing multilateral junctions in a wellbore, patching apertures in a wellbore and lining a wellbore.