Packer Backup Ring with Closed Extrusion Gaps

Abstract

Alternating l-shaped side slots are cut into opposed sides of a backup ring and are circumferentially offset and alternately extend from the inside and outside dimension. An oval shaped opening connects adjacent circumferentially offset slots so that on ring expansion the inside and outside diameters increase as the openings are sheared at one end to place a barrier in opened side slot to prevent extrusion of the adjacent sealing element.

We claim: 
     
         1 . A backup ring assembly for extrusion protection for a sealing element of a borehole barrier, comprising:
 a continuous ring having an inside and an outside surface and an axis;   
       circumferentially spaced slots having a first end extending into said ring from said inside and outside surfaces and having a second end ending short of an opposing said inside or outside surface such that said ring can remain continuous as said inside and outside surfaces grow dimensionally by virtue of said slots opening gaps, said gaps substantially closed at one end by a portion of said ring for contacting the sealing element to minimize extrusion through said gaps. 
     
     
         2 . The assembly of  claim 1 , wherein:
 said slots on said inside and outside surfaces each formed by circumferentially spaced axially extending segments connected by a transverse opening in said ring.   
     
     
         3 . The assembly of  claim 2 , wherein:
 said transverse openings at each said slot comprise opposed ends at said inside and said outside surfaces.   
     
     
         4 . The assembly of  claim 3 , wherein:
 said openings are positioned midway on said inside and outside surfaces.   
     
     
         5 . The assembly of  claim 3 , wherein:
 said ends of said openings that join said respective segments shearing or separating to enable opening of said gaps.   
     
     
         6 . The assembly of  claim 3 , wherein:
 said ends of said openings that do not join said respective segments remaining intact when said inside or outside surfaces increase in dimension.   
     
     
         7 . The assembly of  claim 2 , wherein:
 said slots at an end away from said inside and outside surfaces comprising a stress reduction bend.   
     
     
         8 . The assembly of  claim 1 , wherein:
 said ring having a triangular cross-section such that said outside surface is wider than said inside surface.   
     
     
         9 . The assembly of  claim 5 , wherein:
 said transverse openings comprise an oblong shape so that said shearing or separating defines relatively moving opposed surfaces as said slots open to form said gaps.   
     
     
         10 . The assembly of  claim 9 , wherein:
 said surfaces are disposed at an internal end of said gaps that open from said slots.   
     
     
         11 . The assembly of  claim 9 , wherein:
 said relative movement of said opposed surfaces substantially blocks an internal opening in said gaps that open from said slots.   
     
     
         12 . The assembly of  claim 9 , wherein:
 said relative movement of said opposed surfaces is circumferential about said axis of said ring.   
     
     
         13 . The assembly of  claim 9 , wherein:
 said oblong opening shears at opposed ends to define said opposed surfaces.   
     
     
         14 . The assembly of  claim 1 , wherein:
 said slots define a dovetail shape of a male portion retained by a female portion with space in between said male and female portion to allow relative circumferential movement for enlarging said inside and outside surfaces as said gaps are created.   
     
     
         15 . The assembly of  claim 14 , wherein:
 said male portion extending into said gaps to substantially block an extrusion path for the sealing element.   
     
     
         16 . The assembly of  claim 15 , wherein:
 said gaps extending to varying sizes to allow said outside surface to conform to irregularities in the surrounding borehole.   
     
     
         17 . The assembly of  claim 1 , wherein:
 said gaps extending to varying sizes to allow said outside surface to conform to irregularities in the surrounding borehole.   
     
     
         18 . The assembly of  claim 3 , wherein:
 said openings are positioned offset from midway on said inside and outside surfaces.   
     
     
         19 . The assembly of  claim 1 , wherein:
 said ring having a multilateral cross-section.