Abstract:
Arrangements and packer devices having anti-extrusion backup rings that are expanded radially outwardly by a setting mechanism that lies proximate the elastomeric packer element that is being protected against extrusion. The setting mechanism can be a slip assembly that has a radially expandable slip element.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates generally to the design of packer devices. 
         [0003]    2. Description of the Related Art 
         [0004]    Anti-extrusion backup rings are used to prevent or reduce extrusion of deformable elastomeric packer elements for packer devices in wellbores. Other backup rings partially encase an end portion of the elastomeric packer element and are therefore, expanded radially outwardly as the packer element expands radially during setting. Backup rings of this type are discussed in U.S. Pat. No. 8,083,001 issued to Conner et al. which is owned by the assignee of the present invention and is herein incorporated by reference. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides packer devices having one or more anti-extrusion backup rings that are expanded radially outwardly by the radial expansion of a setting mechanism that lies proximate the elastomeric packer element that is being protected against extrusion. In certain embodiments, the setting mechanism is a slip assembly that has a radially expandable slip element. In particular embodiments, the slip assembly is set by axial movement of the slip element over a setting cone. In a described embodiment, the anti-extrusion backup ring has an interior portion that extends along the end wall of the packer element and an exterior portion that is substantially perpendicular to the interior portion. In the described embodiment, the exterior portion overlies a portion of the slip element. The slip element urges the backup ring into mechanical or intimate contact with a surrounding tubular when the slip element is set against the surrounding tubular. Outward radial expansion of the slip element will urge the exterior portion of the backup ring radially outwardly. In a described embodiment, the exterior portion of the backup ring is urged into contact with the surrounding tubular by the slip element. When so set, the backup ring prevents or reduces axial extrusion of the packer element past the backup ring in the direction of the slip assembly. 
         [0006]    In another described embodiment, the backup ring takes the form of an annular spring that radially surrounds the cone of the slip assembly. During setting of the packer device, the slip element urges the spring into a wedged position between the cone and the surrounding tubular so that the wedged spring acts as backup ring to prevent extrusion of the packer element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The advantages and further aspects of the invention will be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing and wherein: 
           [0008]      FIG. 1  is a one-quarter side cross-sectional view of an unset exemplary packer device having an anti-extrusion backup ring in accordance with the present invention. 
           [0009]      FIG. 2  is a one-quarter side cross-sectional view of the packer device of  FIG. 1 , now in a set position. 
           [0010]      FIG. 3  is a one-quarter side cross-sectional view of an unset packer device having an exemplary alternative anti-extrusion backup ring in accordance with the present invention. 
           [0011]      FIG. 4  is a one-quarter side cross-sectional view of the packer device of  FIG. 3 , now in a set position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]      FIG. 1  illustrates an exemplary compression-set packer device  10  that includes an interior cylindrical mandrel  12  that defines an interior flowbore  14  having central axis  16  along its length. As the general construction and operation of a compression-set packer device is well known, it will not be discussed in detail here. 
         [0013]    A compressible, or compression-set, packer element  18  radially surrounds the mandrel  12 . The packer element  18  is preferably formed of a deformable elastomer, as is known in the art. An anti-extrusion backup ring  20  is located adjacent the packer element  18 . The backup ring  20  has an interior portion  22  that extends radially outwardly from the mandrel  12  and along the end wall  24  of the packer element  18 . The backup ring  20  also has an exterior portion  26  that, in the depicted embodiment, is substantially perpendicular to the interior portion  22 . In particular embodiments, the backup ring  20  is formed of metal. A suitable metal for this application is annealed 8620 steel. In other particular embodiments, the backup ring  20  is formed of a non-metallic material such as carbon epoxy and other composites. In preferred embodiments, the backup ring  20  has a rigidity that allows it to be deployed with a setting force that is usual and customary for setting of the packer element  18 . In particular embodiments, the setting force would be in the range of 5,000-15,000 lbs. In accordance with other embodiments, the backup ring  20  could be a non-metallic petal-style backup ring that is not flexible, but has a designated break point. 
         [0014]    In accordance with other particular embodiments of the present invention, the exterior portion  26  of the backup ring  20  is slotted so that the backup ring  20  is of the petal variety. Also in certain embodiments, this petal-style ring is formed of non-metallic material. 
         [0015]    A slip assembly, generally shown at  28 , radially surrounds the mandrel  12  and includes a cone  30  that is axially slidable upon the mandrel  12 . The cone  30  presents a ramped outer radial setting surface  32 . The slip assembly  28  also includes a slip element  34 . The slip element  34  is typically radially segmented, but need not be so. The slip element  34  preferably has teeth  36  to create a biting engagement with a surrounding tubular member  38  when set. The slip element  34  presents a radially inwardly-facing slanted surface  40  that is complimentary to the surface  32  of the cone  30 . The slip element  34  is located so that the slanted surface  40  is in contact with the surface  32  of the cone  30 . It is noted that, in the unset position, shown in  FIG. 1 , an end portion  42  of the slip element  34  is disposed radially within the exterior portion  26  of the backup ring  20 . 
         [0016]    A ring  44  also radially surrounds the mandrel  12  and is affixed to the mandrel  12  by threaded or bonded connection  46 . The ring  44  contacts the slip element  34 . 
         [0017]    In order to set the packer device  10 , the components surrounding the mandrel  12  are axially compressed against the ring  44  as is known in the art. As  FIG. 2  illustrates, the packer element  18  will expand radially outwardly and into sealing contact with the surrounding tubular  38 . As the cone  30  is moved axially toward the ring  44 , the slip element  34  is moved radially outwardly due to sliding movement of the slip element  34  upon the ramped surface  32  of the cone  30 . The slip element  34  is moved radially outwardly until its teeth  36  bitingly engage the surrounding tubular  38 . 
         [0018]    The radial outward movement of the slip element  34  also energizes the backup ring  20 . The interior portion  24  of the backup ring  20  is urged against the packer element  18 . The exterior portion  26  of the backup ring  20  is also preferably brought into contact with the surrounding tubular  38  by the slip element  34 . The backup ring  20  now functions as an anti-extrusion barrier which will prevent extrusion of the packer element  18  axially toward the slip assembly  28 . Although only a single backup ring  20  is depicted associated with a single axial end wall  24  of the packer element  18 , it should be understood that a similar to backup ring and setting arrangement could be used for the opposite axial end of the packer element  18 . 
         [0019]    It will be understood that the invention provides an arrangement for preventing axial extrusion of a packer element that is set within a surrounding tubular. This arrangement includes the anti-extrusion backup ring  20  as well as the setting mechanism that is provided in certain embodiments by the slip assembly  28 . 
         [0020]    In addition, it should be understood that the invention provides methods for establishing an anti-extrusion backup seal for a packer element  18  in a packer device  10  to be set within a surrounding tubular  38 . In accordance with these methods, an anti-extrusion backup ring  20  is placed proximate an end wall  24  of the packer element  18 . The backup ring  20  is then energized to prevent extrusion by a setting mechanism other than the packer element  18 . In particular embodiments, the setting mechanism is a slip assembly  28  and energizes the backup ring  20  by urging a slip element  34  radially outwardly to cause the backup ring  20  to be urged against the packer element  18 . In certain embodiments, the slip element  34  urges a portion of the backup ring  20  into engagement with the surrounding tubular  38 . 
         [0021]    The inventors have found that the arrangements and methods of the present invention provide for positive energizing of the backup ring  20 . Since the slip element  34  is formed of a rigid material or assemblage of rigid materials, it will provide for a rigid anchoring of the backup ring  20  against the surrounding tubular  38 . 
         [0022]      FIGS. 3 and 4  illustrate an alternative compression-set packer device  50  having a packer element  18  that radially surrounds mandrel  12 . The packer device  50  is constructed and operates in the manner as the packer device  10  described previously except where indicated otherwise. The inclined outer surface  32  of cone  30  preferably includes an annular recess  52 . An annular spring  54  is disposed on the outer surface  32  of the cone  30 . Preferably, the spring  54  resides within the recess  52 . In one embodiment, the spring  54  is formed of a non-metallic ceramic material, such as carbon fiber reinforced PEEK (polyether ether ketone). Suitable annular springs for use as the spring  54  are available commercially from a number of manufacturers, including Automated Dynamics of Schenectady, N.Y. 
         [0023]    When the packer device  50  is moved from the unset position ( FIG. 3 ) to the set position ( FIG. 4 ) by compression, the end portion  42  of the slip element  34  will contact the spring  54  and urge it over the cone  30 . The spring  54  is then wedged between the cone  30  and the surrounding tubular  38  so that the spring  54  functions as an anti-extrusion backup member that will prevent extrusion of the packer element  18  axially within the surrounding tubular  38 . It is noted that the spring  54  may deform (flatten) cross-sectionally as it is wedged. 
         [0024]    The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to those skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention.