Abstract:
A swellable packer ( 10 ) includes upper and lower end rings ( 20, 22 ) and elastomeric bodies ( 12, 14 ) spaced between the upper and lower end rings to expand and thereby close off an annulus about the downhole tubular. The elastomeric body may be positioned such that a slot ( 26 ) in the body receives a control line ( 28 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority of U.S. Provisional Application Ser. No. 61/241,093 filed on Sep. 10, 2009, the disclosure of which is incorporated herein by reference for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a swellable elastomer element packer that may be placed around a tubular at any location and may be used in both conventional completions and intelligent well completions. 
       BACKGROUND OF THE INVENTION 
       [0003]    Various types of swellable packers have been devised, including packers which are fixed to the OD of a tubular and the elastomer formed by wrapped layers, and designs wherein the swellable packer is slipped over the tubular and locked in place. If the operator desires to have control lines pass through the packer for intelligent well completions, the control line typically was axially aligned with a slot, generally in the exterior of the packer, since the packer was otherwise fixed to the casing or pipe. Manipulation of a control line to obtain proper alignment with a slot in the packer may be difficult, and may risk damage to the control line. An alternative solution is to cut the slot in the exterior of the elastomer cover at the rig site for alignment with the control line. This practice is complicated by the size variance in the cross-section of the control line and/or the encapsulation of the control line. 
         [0004]    Swellable packers are disclosed in U.S. Pat. Nos. 7,472,757 and 7,552,768. U.S. Pat. No. 6,173,788 illustrates control lines on the exterior of a packer, and Publication 2007/0012436 discloses a control cable within the elastomeric body of the packer. Other patents of interest include U.S. Pat. Nos. 4,024,916, 5,137,970, and 6,431,282, 6,474,414, 6,828,531, 6,923,283, and 7,562,710. 
         [0005]    The disadvantages of the prior art are overcome by the present invention, and an improved swellable packer and method of installing a packer is hereinafter disclosed. 
       SUMMARY OF THE INVENTION 
       [0006]    In one embodiment, a swellable packer includes a two piece swellable element manufactured as a single unit and then split longitudinally into two halves. Each of the two halves includes swellable rubber between split end rings. Since the packer may be split in two halves, any control lines are visible from the bore of the respective packer half during installation of the packer on a tubular. 
         [0007]    According to the method of the invention, a lower split end ring and an upper split end ring may be provided for surrounding the downhole tubular. The method includes providing two or more C-shaped elastomeric bodies each spaced longitudinally between the end rings to expand and seal the annulus about the downhole tubular. The end rings are fixedly connected to the downhole tubular, and a side face of one C-shaped elastomeric body is positioned adjacent a side face of another C-shaped elastomeric body to form an elastomeric seal when the elastomer is expanded. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a front view of one embodiment of the packer according to present invention. 
           [0009]      FIG. 2  is a sectional side view of the packer shown in  FIG. 1 . 
           [0010]      FIG. 3  is an end view of the packer shown in  FIG. 1 . 
           [0011]      FIG. 4  is a cross sectional view of the packer shown in  FIG. 1 . 
           [0012]      FIG. 5  is a front view of an alternate embodiment of a packer. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0013]      FIG. 1  depicts a swellable packer  10  with an elastomeric element formed as a unit and split into two halves  12 ,  14  after manufacture. These two halves each include the swellable elastomer body  18 , and split end rings  20 ,  22 . The swellable packer  10  may be fabricated conventionally from elastomer layers which are repeatedly wrapped around a mandrel, and then the elastomeric body is cured at an elevated temperature. The split elastomeric bodies and end rings may be slid off the mandrel, which may be reused for manufacturing another packer. Each end ring has wicker type grooves  24 , as shown in  FIG. 2 , so that when the end rings are bolted together, the wickers are embedded into the tubular, thereby restraining the packer halves from moving circumferentially or axially. When the two packer halves are locked together on the tubular, there is no visible gap between the rubber halves, which are butted up against each other. The halves may have a straight cut axially separating the two halves, as shown in  FIG. 1 , or a castellated type slot  32 , as shown in  FIG. 5 . The tooth pattern of the slot may vary considerably, depending on the application. An advantage of the latter embodiment is that this provides a more tortuous path for any potential leak down the swelled joint at higher pressures and temperatures. Either or both of the halves  12 ,  14  may include a slot  26  (see  FIG. 2 ) for a suitable control line  28 . Alternatively, the control line may be encapsulated into the molded elastomer. The control line may be visible from the lower bore of the swellable packer, which allows the control line to be run in a normal manner on the outside of the tubular going down hole, then the split half swellable packer aligned with the control line, rather than aligning the control line with the slot in the packer. In this design, the control or encapsulated lines may be run along the outside of a downhole tubular, in a conventional fashion, and each swellable packer half aligned to a control line, not the other way around. Once the two packer halves are placed over the capsulated lines, the two halves are bolted together with the inner faces containing the wickers gripping the tubular. The inner face of each split end ring may be configured for reliable gripping engagement with the base tubular on which the packer is mounted. Various types of gripping teeth may be provided on the inner face of an end ring. In some applications, a C-shaped inlay may be provided, thereby effectively forming an inlay sleeve for gripping the base tubular without damaging the tubular. In other applications, one or more of the inner faces of a split end ring may be manufactured with a slight “wave” to the otherwise cylindrical inner surface of a split ring, thereby again concentrating forces to provide reliable gripping engagement without damaging the tubular. 
         [0014]      FIG. 3  is the end view of the packer  10  shown in  FIG. 1 , and illustrates the position of two control lines spaced circumferentially 180° apart. The lower end rings  22  and the mating faces of the two split end rings are also shown in  FIG. 3 . 
         [0015]      FIG. 4  is a cross sectional view through the elastomeric body  26 , and shows the circumferentially opposing control lines  28  and the tubular  40  on which the packer is mounted. 
         [0016]    As the swellable packer is run into the well, the swelling fluid, whether an oil or a water based fluid, will act on the surface of the split elastomer sleeves. When the elastomer swells, it will touch the borehole, or the bore of the casing or other tubular in the hole, with continued swelling by absorption and adsorpotion of the fluid exposing the swelled areas between inner and outer diameters of the elastomeric element and the OD of the tubular and the ID of the outer tubular or borehole wall, and between the two mating side faces of adjacent split elastomeric elements, thereby continuing to have the swell fluid enter the swellable elastomer through those exposed areas. When the packer halves are fully swelled, the split faces will be swelled into one homogenous piece of elastomer and also swelled around the control lines. If pressure is applied from either or both ends of the packer at the same time, both ends of the swellable elastomeric element move simultaneously toward each other, thereby providing bi-directional sealing capability. For the  FIG. 5  embodiment, the packer  10  need not include control lines. The packer may be fabricated as discussed above, then the two halves simply bolted or otherwise secured together on a tubular. 
         [0017]    The packer as disclosed herein has significant advantages compared to the prior art. There is no need for well operations involving packer setting, and the packer has no moving parts and is thus simple and highly reliable. The packer may be shipped to the field and placed at any position on a tubular, as desired by the operator. As shown in  FIG. 4 , the base tubular (pipe) may be wrapped with a thin layer  45  of swellable elastomer that adheres to the base tubular. The split halves of the elastomeric body abut during assembly, engage the thin elastomer layer  45  on the base tubular, and provide additional swell/seal around the control line. 
         [0018]    Control line slots may be cut in the interior of the elastomeric body at a manufacturing facility, since in most cases the size, type and position of the control lines, e.g., control lines 180° apart, will be known as the packer is manufactured. In other situations, the control line gap may be cut in the field. Expansion of the elastomeric material fills any voids around the control line. The control lines may also be passed through apertures or slots in the upper and lower end rings. 
         [0019]    The term “control line” as used herein includes any type of control line, encapsulated line, or other line comprising cable of any type, including fiber optic or electrical conductor, which conducts power or signals between the surface and downhole points. 
         [0020]    A reliable swellable packer is obtained without having to ship the customer the tubular on which the swellable elastomer is molded and/or which there is a wrapping. This allows a substantially thicker rubber to be used compared to embodiments which slip an entire packer body over the end of the material, since the inner sleeve has size restrictions and overcoming the size of the tubular ends is not necessary. This allows for much higher flexibility to the operator, who may maintain a stock of packers of a selected size and promptly install and use the packer of this design on any proper size tubular. 
         [0021]    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.