Patent Publication Number: US-10329870-B2

Title: Sealing element backup ring with integrated tab to close extrusion path along a mandrel

Description:
FIELD OF THE INVENTION 
     The field of the invention is packer sealing element design and more particularly backup rings that retain a sealing element in a set position against axial extrusion along a mandrel and a surrounding tubular. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  illustrates a packer in a run in position akin to a Premier® model offered by Baker Hughes Incorporated of Houston, Tex. The seal element assembly  17 ,  18 ,  19  and  20  is surrounded by backup rings  15 . A lower gage ring  21  holds a lock ring  22  so that the set position can be held. Slips  11  after breaking shear pin  12  mounted through a bore  13  moves axially and up the ramp of cone  14  to engage the surrounding tubular after the sealing element assembly  17 ,  18 ,  19  and  20  is axially compressed against the surrounding tubular. These parts are mounted to the outer surface of mandrel  10 . To prevent extrusion between the mandrel  10  and the backup ring  15  is a wedge ring  16  that is pushed into a corner against the backup ring  15  and the mandrel  10 . This ring is usually made from PEEK and is expensive to produce and very difficult to insert. Beyond that it can move during a set and become ineffective for its intended purpose if it is displaced from its original location during the set. It can be pushed out of the corner where it was inserted, roll on its axis, or simply not fully installed into the intended corner location to control axial extrusion along the mandrel. 
     The present invention seeks to overcome these problems by integrating an abutting ring to the extrusion barrier adjacent the mandrel to employ the forces developed in the sealing element to press the abutting ring firmly against a mandrel to close an extrusion gap there. One side of the ring is preferably an extension of the inside dimension of the base ring for the backup ring while the sealing element fills a gap between a tapered opposite side of the abutting ring and the backup ring structure. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims. 
     SUMMARY OF THE INVENTION 
     A backup ring assembly has a base ring to support the plastically deformed extrusion barrier when the packer sealing element is set. The base ring has a thin walled tapered extending ring out of the base ring and into the direction of the sealing element. The sealing element fills the annular gap volume between an upper taper on the extending ring and the body of the backup ring such that on setting the pressure internally in the seal material helps to apply a force in a direction toward the mandrel and for the full circumference of the mandrel. This force and the flexibility of the extending ring helps push the extending ring toward the mandrel outer surface to close extrusion gaps between the mandrel and the base ring of the backup ring assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a section view of an existing design of a packer sealing element assembly shown in the run in condition; 
         FIG. 2  is a detailed view of the backup ring of the assembly shown in  FIG. 1 ; 
         FIG. 3  is a run in view in section of a backup ring assembly featuring the extending ring from the base ring of the backup ring assembly; 
         FIG. 4  is the view of  FIG. 3  showing the direction of the applied forces as setting begins; 
         FIG. 5  is the set position showing the backup ring containing the sealing element and the extrusion gap around the mandrel closed by the flexed extending ring. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 3  shows cone  14  on mandrel  10  retaining the backup ring assembly  15 ′ at thread  30 . A portion of the seal assembly in the form of sealing element  17  is also shown. The backup ring assembly has a base ring  32  located between the cone  14  and the mandrel  10 . Extending from base ring  32  is the elongated structure  34  that spans over sealing element  17  with an end  36  designed to be plastically deformed against a surrounding tubular  38  to close off the annular space at the end of the sealing element  17  against the surrounding tubular  38 . The set position of the structure  34  is visible in  FIG. 5 . 
     The base ring  32  has an inside surface  40  facing the mandrel  10 . A flexible extending ring  42  is formed one side preferably by a continuation of surface  40  and on an opposite side by a tapered surface  44  so that the sealing element  17  will climb up on ramp surface  44  in the set position when pressure is developed inside the sealing element  17 . Radial surface  46  and adjacent tapered surface  48  on the elongated structure  34  identify a pocket into which the sealing element  17  end  50  fits snugly. End  52  of the extending ring  42  is preferably blunt to avoid cutting into the sealing element  17  in the setting operation. 
     As axial compression occurs, arrows  54  schematically represent the forces generated in the sealing element  17  on the way to the set position shown in  FIG. 5 . As seen in  FIGS. 4 and 5  the extending ring  42  is pushed against the mandrel  10  to close off any extrusion gap along the mandrel  10  outer surface. The backup ring assembly  15 ′ extends to the surrounding tubular  38  by plastic deformation as it is bent around peripheral surfaces of the cone  14 . The pressure inside the seal element  17  and the adjacent sealing elements helps maintain a pressure on the extending ring  42  in the direction of mandrel  10  principally in a radial direction. Because the extending ring  42  is a continuation of surface  40  and is built integrally to the base ring  32  and is trapped between the set seal  17  and the mandrel  10  the effectiveness of the seal against the mandrel  10  is enhanced. The flexibility of the ring  42  enables it to conform to any imperfections or out of roundness of the mandrel  10  to close off any potential extrusion paths along mandrel  10 . Preferably the entire backup ring assembly  15 ′ is manufactured out of a single workpiece in a common material but variations are envisioned where the ring  42  is of a different material or is a separate piece from the balance of the backup ring assembly  15 ′ and secured to the base ring  32  mechanically such as with fasteners or adhesives or other fixation methods. The ring  42  is preferably a complete ring for 360 degrees in a single layer but options of multiple layers and segmented ring structure is also envisioned. 
     The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: