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BACKGROUND  
       [0001]     The present invention relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides an uncollapsed expandable wellbore junction.  
         [0002]     It is known in the art to fabricate a wellbore junction, or another type of pressure vessel, at the surface and then collapse the junction so that it can be conveyed through a wellbore. When appropriately positioned in the wellbore, the junction is then expanded back to its originally fabricated configuration.  
         [0003]     However, significant problems have been experienced with this method of expanding wellbore junctions. For example, the collapsing operation tends to work harden the material of which the junction is constructed, which makes the material less likely to exactly resume its expanded configuration in the well, and which makes the material more susceptible to corrosion and cracking in the wellbore environment. Critical areas of the junction, such as welds and tight radii areas, are subjected to very high stresses in the collapsing operation. Specialized and complex tooling, such as a built-for-purpose press, crushing mandrels and dies are needed for the collapsing operation.  
         [0004]     Therefore, it may be seen that improved systems and methods are needed for fabricating and expanding wellbore junctions. These systems and methods would find application in creating other types of expandable pressure vessels, as well.  
       SUMMARY  
       [0005]     In carrying out the principles of the present invention, in accordance with an embodiment thereof, an uncollapsed expandable pressure vessel is provided for use in a subterranean well. The described embodiment is a wellbore junction for interconnecting intersecting wellbores in the well. Associated methods are also provided.  
         [0006]     In one aspect of the invention, a method of creating an expanded pressure vessel in a subterranean well includes the step of expanding the pressure vessel in the well, thereby increasing a dimension of the vessel, without prior decreasing of the dimension.  
         [0007]     In another aspect of the invention, a method of creating an expanded pressure vessel in a subterranean well includes the steps of fabricating the vessel in an unexpanded configuration, without decreasing a dimension of the vessel; and then expanding the vessel in the well.  
         [0008]     In yet another aspect of the invention a wellbore junction system for use in a subterranean well is provided. The system includes a wellbore junction expanded outwardly in the well from an unexpanded and uncollapsed configuration.  
         [0009]     These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic partially cross-sectional view of a wellbore junction system and associated method embodying principles of the present invention;  
         [0011]      FIG. 2  is a schematic partially cross-sectional view of the system and method of  FIG. 1 , in which further steps of the method have been performed;  
         [0012]      FIG. 3  is a schematic isometric view of a wellbore junction used in the system and method of  FIGS. 1 &amp; 2 , the wellbore junction embodying principles of the invention;  
         [0013]      FIG. 4  is a top view of the wellbore junction, showing an upper end of the junction in unexpanded and expanded configurations;  
         [0014]      FIG. 5  is a bottom view of the wellbore junction, showing a lower end of the junction in unexpanded and expanded configurations;  
         [0015]      FIG. 6  is a side view showing a method of forming portions of the wellbore junction;  
         [0016]      FIG. 7  is a cross-sectional view of a portion of the wellbore junction formed according to the method of  FIG. 6 ;  
         [0017]      FIG. 8  is an isometric view of an initial step in a method of fabricating the wellbore junction;  
         [0018]      FIGS. 9-17  are isometric views of intermediate steps in the method of fabricating the wellbore junction; and  
         [0019]      FIG. 18  is an isometric view of the fabricated wellbore junction in its unexpanded and uncollapsed configuration.  
     
    
     DETAILED DESCRIPTION  
       [0020]     Representatively illustrated in  FIG. 1  is a wellbore junction system  10  and associated method of creating an expanded pressure vessel, which embody principles of the present invention. In the following description of the system  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention.  
         [0021]     As depicted in  FIG. 1 , a casing string  12  has been conveyed into a wellbore  14 . The wellbore  14  is illustrated as being uncased both above and below a radially enlarged cavity  16  formed in the wellbore, for example, by underreaming. However, any portion of the wellbore  14  could be cased or otherwise lined prior to conveying the casing string  12  into the wellbore, and it is not necessary for the cavity  16  to be formed in the wellbore. Furthermore, the casing string  12  could be another type of tubular string, such as a liner string or tubing string, etc.  
         [0022]     A wellbore junction  18  is interconnected in the casing string  12 . The junction  18  is positioned in the cavity  16 , so that when the junction is later expanded, it can extend outward beyond the wellbore  14  as originally drilled. However, note that if it is not desired to extend the junction  18  in its expanded configuration beyond the wellbore  14  as originally drilled, then the cavity  16  may not be formed in the wellbore.  
         [0023]     It should be clearly understood that the junction  18  is described herein as merely one example of a pressure vessel which may be expanded in a well. Any other type of pressure vessel having a pressure-bearing wall could be used in keeping with the principles of the invention. The vessel may be used for any purpose, such as for downhole storage, for separation of petroleum fluids and water, for downhole manufacturing, etc.  
         [0024]     The junction  18  is used in the system  10  to interconnect the wellbore  14  to another wellbore  20  (see  FIG. 2 ) which will intersect the first wellbore  14 . The wellbore  20  could be drilled before or after the junction  18  is positioned at an intersection  22  between the wellbores  14 ,  20 . Because of the various unique features of the junction  18  described below, the junction has a much improved capability of withstanding pressure differentials applied across its pressure-bearing walls at the intersection  22 .  
         [0025]     In the system  10  as depicted in  FIGS. 1 &amp; 2 , the wellbore  14  is drilled first, so that it extends above and below the intersection  22 . The wellbore junction  18  is then positioned at the intersection  22 , and the junction is expanded. Then, the wellbore  20  is drilled outwardly from the intersection  22  through a leg  24  of the junction  18 . Another leg  26  of the junction  18  extends downwardly inline with the wellbore  14  and is connected to a portion of the casing string extending downwardly into the wellbore below the cavity  16 .  
         [0026]     Alternatively, the junction  18  could be positioned at a lower end of the wellbore  14 . The junction  18  could then be expanded, and intersecting wellbores could be drilled through each of the legs  24 ,  26 . One or neither of these wellbores could be inline with the wellbore  14  above the junction  18 .  
         [0027]     Although the junction  18  is depicted as having only two downwardly extending legs  24 ,  26 , it will be appreciated that any number of legs could be provided in the junction. For example, the junction  18  could have three, four or more legs. The legs could be laterally inline with each other, or they could be longitudinally spaced apart and/or radially distributed in the junction  18 .  
         [0028]     In one important aspect of the invention, the junction  18  is conveyed into the wellbore  14  in an unexpanded configuration (as depicted in  FIG. 1 ), without having been previously collapsed. In this way, the technical difficulties, metallurgical problems and extreme stresses of the collapsing operation are avoided. Instead, the junction  18  is originally fabricated in its unexpanded configuration, conveyed into the wellbore  14 , and then expanded to its expanded configuration for the first time.  
         [0029]     Thus, the junction  18  has an outer dimension d at the time it is conveyed into the wellbore  14 . After being expanded in the wellbore  14 , the junction  18  has an enlarged outer dimension D. Instead of fabricating a junction so that it originally has the outer dimension D, then collapsing the junction so that it has the outer dimension d, conveying it into a wellbore, and then expanding the junction so that it again has the outer dimension D (as was done in the prior art), the junction  18  is fabricated so that it has the outer dimension d in its original configuration.  
         [0030]     The width dimensions d and D are given as examples of dimensions that may be expanded. Other dimensions that could be expanded include cross-sectional area, circumference, diameter, length, etc. Any dimension of a vessel can be expanded in keeping with the principles of the invention.  
         [0031]     Preferably, the junction  18  is expanded by applying a pressure differential across a pressure-bearing wall of the junction to thereby inflate the junction. One or more plugs may be provided for one or both of the legs  24 ,  26 , so that pressure can be applied via the casing string  12  above the junction  18  to inflate the junction. Alternatively, the junction  18  could be expanded by other methods, such as by mechanically swaging or drifting, etc. Furthermore, the junction  18  could be expanded by a combination of methods, such as by combined inflation and mechanical forming (e.g., swaging or drifting). In that case, preferably the junction  18  would be expanded by inflating the junction (either directly, or via a membrane or bladder positioned inside the junction, etc.), and then the junction would be further expanded or “sized” to a certain desired shape by mechanical forming.  
         [0032]     The junction  18  may be cemented in the wellbore  14  and cavity  16  either with, or separately from, the remainder of the casing string  12 . For example, the casing string  12  could be cemented in the wellbore  14  prior to drilling the branch wellbore  20 , then the junction  18  could be cemented in the cavity  16  after a liner string (not shown) is positioned in the branch wellbore and sealingly secured to the leg  24 . The leg  24  could have a seal bore therein, such as a polished bore receptacle (PBR), for sealing engagement with the liner string.  
         [0033]     The junction  18  may also be provided with conventional internal orienting profiles and latching profiles for rotationally orienting the junction relative to the branch wellbore  20 , for anchoring and orienting whipstocks and other deflectors, etc.  
         [0034]     Referring additionally now to  FIG. 3 , a middle portion  28  of the junction  18  is representatively illustrated in its expanded configuration apart from the remainder of the system  10 . In this view it may be seen that the middle portion  28  of the junction  18  forms an intersection between an upper generally cylindrical body  30  and each of the lower legs  24 ,  26 . This intersection is strengthened, and its fabrication is facilitated, by a stiffener  32  interposed between the legs  24 ,  26  and body  30  at the intersection, which is described in more detail below.  
         [0035]     A top view of the body  30  is depicted in  FIG. 4 . The expanded configuration of the body  30  is shown in solid lines. An unexpanded, cloverleaf-shaped, configuration of the body  30  is shown in dashed lines. Note that the body  30  is originally fabricated in the unexpanded configuration, rather than being collapsed or crushed from its expanded configuration.  
         [0036]     A bottom view of the legs  24 ,  26  is depicted in  FIG. 5 . The expanded configurations of the legs  24 ,  26  are shown in solid lines. An unexpanded, partial cloverleaf-shaped, configuration of each of the legs  24 ,  26  is shown in dashed lines. Again, the legs  24 ,  26  are originally fabricated in the unexpanded configurations.  
         [0037]     The unexpanded configurations of the body  30  and legs  24 ,  26  (and other portions of the junction  18 ) are fabricated using techniques which reduce stresses in the various junction portions due to the fabrication process. For example, in  FIG. 6 , a portion  34  of the junction  18  is shown being folded or bent greater than 180 degrees between a cylindrical die  36  and an elastomeric pad  38 , without overstressing the material. This operation can be performed on a conventional brake press, with very little need for specialized equipment, unlike prior methods of crushing wellbore junctions in a built-for-purpose press.  
         [0038]     In  FIG. 7 , an end view of the junction portion  34  is shown after opposite sides of the portion have been folded over in an operation similar to that shown in  FIG. 6 . By welding together four of the portions  34 , the cloverleaf-shaped unexpanded configuration of the body  30  may be fabricated, as shown in  FIG. 4 . This cloverleaf-shaped configuration is achieved without overstressing the material, allowing the body  30  to be fabricated in a smaller space (having smaller outer dimensions) than in previous wellbore junctions. Similarly, other portions of the junction  18  may be fabricated by bending, folding or otherwise partially collapsing multiple individual pieces, and then interconnecting the pieces to each other, or to other uncollapsed pieces.  
         [0039]     Note that welding may be used to interconnect pieces or portions of the junction  18  to each other when those elements are made of metal, but other methods may be used if desired. For example, fasteners, adhesives, explosive bonding, etc. could be used instead of, or in addition to, welding. If the elements are made of non-metallic materials, such as composites or combinations of metals and composites, then other methods may also be used.  
         [0040]     The process of fabricating the junction  18  in its unexpanded configuration is illustrated in  FIGS. 8-17 . However, it should be understood that these figures merely depict one example of a wide variety of methods which may be used to fabricate an expandable pressure vessel according to the principles of the invention. Thus, the invention is not limited to the specific details of this one example described below.  
         [0041]     In  FIG. 8 , it may be seen that the basic starting point in fabricating the junction  18  is the stiffener  32 . This provides a foundation on which the intersection between the body  30  and legs  24 ,  26  is formed. Preferably, the stiffener  32  is fabricated in at least two pieces and then joined together, for example, by welding. The stiffener  32  could be fabricated in one piece, however, in keeping with the principles of the invention.  
         [0042]     In  FIG. 9 , two inner upper portions  40  of the legs  24 ,  26  are attached on opposite sides of the stiffener  32 . A plate  42  is attached to the stiffener  32  and to each of the portions  40 .  
         [0043]     In  FIG. 10 , two inner lower portions  44  of the body  30  are attached within the stiffener  32 . The portions  44  are also welded to the portions  40 .  
         [0044]     In  FIG. 11 , two of the portions  34  of the body  30  are attached above the portions  44 . Two upper body portions  46  are attached above the portions  34 . The upper body portions  46  provide a transition from the cloverleaf-shaped cross-section of the body  30  shown in  FIG. 4  (formed by the portions  34 ) to the cylindrical shape needed for connection of the junction  18  to the casing string  12  above the junction.  
         [0045]     In  FIG. 12 , a middle portion  48  of the leg  24  is attached to a stiffening base  50 . A middle portion  52  of the leg  26  is attached to another stiffening base  54 . The middle leg portions  48 ,  52  may be made up of only one piece each, or they may be made up of multiple interconnected pieces. The two bases  50 ,  54  are attached to each other after the portions  48 ,  52  are attached to the bases.  
         [0046]     In  FIG. 13 , the bases  50 ,  54  are shown attached to each other. The bases  50 ,  54  are then attached to a lower end of the stiffener  32 . Each of the middle leg portions  48 ,  52  is attached to a lower end of one of the inner leg portions  40 . Then, two outer upper leg portions  56  are attached to the inner leg portions  40 , thereby enclosing the upper ends of the legs  24 ,  26  at their intersection with the body  30 .  
         [0047]     In  FIG. 14 , two more lower body portions  58  are attached to the portions  44 , thereby enclosing the lower end of the body  30  at its intersection with the legs  24 ,  26 .  
         [0048]     In  FIG. 15 , two more middle body portions  34  are attached to the previous two portions  34 . This encloses the middle of the body  30  and forms the completed cloverleaf-shaped unexpanded configuration shown in  FIG. 4 .  
         [0049]     In  FIG. 16 , two more of the upper body portions  46  are attached to the previous two portions  46 . This encloses the upper end of the body  30  and forms a cylindrical shape at the top of the body to facilitate connecting to the casing string  12  above the junction  18 .  
         [0050]     In  FIG. 17 , lower ends of the legs  24 ,  26  are shown. A transition piece  60  is attached at a lower end of the leg portion  48 , and a transition piece  62  is attached at a lower end of the leg portion  52 . The transition piece  60  provides a transition between the unexpanded configuration of the leg portion  48  and a configuration of a plug  64  at the lower end of the leg  24 . The plug  64  prevents pressure from escaping through the leg  24  when the junction  18  is inflated. The plug  64  is drilled out later (after the expansion process) when the wellbore  20  is drilled.  
         [0051]     The transition piece  62  provides a transition between the unexpanded configuration of the leg portion  52  and a cylindrical generally tubular configuration of a lower casing connection  66 . The connection  66  may be threaded for connecting the casing string  12  below the junction  18 .  
         [0052]     A deflector  68  is attached to lower ends of the bases  50 ,  54 . The deflector  68  ensures that cutting tools (such as mills, drills, etc.) conveyed through the leg  24  after expansion of the junction  18  are deflected away from the other leg  26 .  
         [0053]     The completed junction  18  is shown in  FIG. 18 . Note that an upper casing connector  70  is attached above the interconnected upper body portions  46 . The connector  70  may be threaded to provide for connecting the junction  18  to the casing string  12  above the junction.  
         [0054]     The interconnected portions of the body  30  and legs  24 ,  26  form pressure-bearing walls of the junction  18 . Thus, the junction  18  is a pressure vessel which is fabricated in an original unexpanded configuration. It will be readily appreciated that, when a pressure differential is applied from the interior to the exterior of the pressure-bearing walls of the junction  18 , that the junction will expand or inflate to its expanded configuration as depicted in  FIG. 2 .  
         [0055]     The expansion process will include unfolding, unbending or otherwise uncollapsing or enlarging various portions making up the junction  18 . For example, the folded or unextended shape of the portions  34  will take on the cylindrical shape of the body  30 , as depicted in  FIG. 4 .  
         [0056]     Note that this expansion process preferably does not include any, or any substantial, lengthening of a perimeter or circumferential stretching of the walls of the junction  18 . Thus, there is preferably no, or no substantial, decrease in the wall thickness of the junction  18  due to the expansion process. For example, the perimeter length of the body  30  in the cloverleaf-shaped unexpanded configuration shown in dashed lines in  FIG. 4  is preferably the same as the perimeter length of the body in the cylindrical expanded configuration shown in solid lines. The same is preferably true of the unexpanded and expanded configurations of the legs  24 ,  26  as depicted in  FIG. 5 .  
         [0057]     Of course, a person skilled in the art would, upon a careful consideration of the above description of a representative embodiment of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to this specific embodiment, and such changes are contemplated by the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.

Summary:
An uncollapsed expandable wellbore junction and associated methods. In a described embodiment, a method of creating an expanded pressure vessel in a subterranean well includes the step of expanding the pressure vessel in the well, thereby increasing a dimension of the vessel, without prior decreasing of the dimension.