Axially Articulated and Rotationally Locked Backup Ring Assembly for a Sealing Element

Abstract

A backup or extrusion barrier ring assembly has multiple rows of rings in segments that have circumferentially offset slots. The rings are rotationally locked to each other to maintain the circumferential offset of the slots that allow the rings to be more flexible in the setting process. The rings as a unit can be mounted to relatively rotate on a supporting mandrel. The rings are mounted to allow them to move axially during setting either in tandem or axially relatively to each other. The axial run in heights of rings decline from innermost to outermost so that when set the heights approach each other to minimize or eliminate sharp ends against the seal. Alternatively, the height difference can be such as to allow ends to bend over an adjacent end further out radially so that free ends bend toward the surrounding tubular and avoid the seal.

We claim: 
     
         1 . An extrusion barrier assembly for a mandrel mounted sealing element in a borehole barrier, comprising:
 a plurality of nested discrete rings mounted to the mandrel for relative axial movement, with respect to the mandrel, of first ends of said rings nearest the mandrel when second ends of said rings are radially actuated from a run in position adjacent said mandrel to a set position in contact with a surrounding borehole wall.   
     
     
         2 . The assembly of  claim 1 , wherein:
 said rings comprise a plurality of axially oriented slots extending from a first axial end thereof, with said slots in adjacent rings circumferentially offset so as to avoid extrusion gaps in said set position.   
     
     
         3 . The assembly of  claim 2 , wherein:
 said rings are rotationally locked with respect to each other to maintain said circumferential offset of said slots.   
     
     
         4 . The assembly of  claim 3 , wherein:
 said rings are rotatably mounted to said mandrel.   
     
     
         5 . The assembly of  claim 3 , wherein:
 said rings each comprise at least one axial keyway such that keyways in said rings are aligned to accept a retainer that permits relative axial movement of said rings and precludes relative rotation between said rings.   
     
     
         6 . The assembly of  claim 5 , wherein:
 said keyways begin at a second axial end opposite said first axial end.   
     
     
         7 . The assembly of  claim 3 , wherein:
 said rings are retained to said mandrel with a retainer ring further comprising a lateral opening for advancing a force regulating retainer radially against said rings to regulate the force required to relatively move said rings in an axial direction.   
     
     
         8 . The assembly of  claim 7 , wherein:
 said rings each comprise at least one axial keyway such that keyways in said rings are aligned to accept a keyway retainer that permits relative axial movement of said rings and precludes relative rotation between said rings.   
     
     
         9 . The assembly of  claim 3 , wherein:
 said slots widen as between said run in and set positions while remaining circumferentially offset as between adjacent said rings.   
     
     
         10 . The assembly of  claim 3 , wherein:
 said rings vary in axial length in said run in position at said first axial end thereof.   
     
     
         11 . The assembly of  claim 10 , wherein:
 said rings comprise a longest in axial length innermost said ring and a shortest in axial. length outermost said ring to define an initial run in height difference, said height difference being reduced in said set position.   
     
     
         12 . The assembly of  claim 10 , wherein:
 said rings comprise a longest in axial length innermost said ring and a shortest in axial length outermost said ring to define an initial run in height difference, said height difference being eliminated in said set position.   
     
     
         13 . The assembly of  claim 10 , wherein:
 at least one of said rings at said first axial end thereof bends over a said first axial end of an adjacent ring when moved to said set position.   
     
     
         14 . The assembly of  claim 10 , wherein:
 at least one of said rings at said first axial end thereof is bent over a said first axial end of an adjacent ring in said run in position.   
     
     
         15 . An extrusion barrier assembly for a mandrel mounted sealing element in a borehole barrier, comprising:
 a plurality of nested discrete rings mounted to the mandrel having first ends of said rings nearest the mandrel and second ends, said second ends of said rings are radially actuated from a run in position adjacent said mandrel to a set position in contact with a surrounding borehole wall;   said rings comprise a plurality of axially oriented slots extending from a first axial end thereof, with said slots in adjacent rings circumferentially offset so as to avoid extrusion gaps in said set position;   said slots widen as between said run in and set positions while remaining circumferentially offset as between adjacent said rings;   said rings vary in axial length in said run in position at said first axial end thereof.   
     
     
         16 . The assembly of  claim 15 , wherein:
 said rings comprise a longest in axial length innermost said ring and a shortest in axial length outermost said ring to define an initial run in height difference, said height difference being reduced in said set position.   
     
     
         17 . The assembly of  claim 15 , wherein:
 said rings comprise a longest in axial length innermost said ring and a shortest in axial length outermost said ring to define an initial run in height difference, said height difference being eliminated in said set position.   
     
     
         18 . The assembly of  claim 15 , wherein:
 at least one of said rings at said first axial end thereof bends over a said first axial end of an adjacent ring when moved to said set position.   
     
     
         19 . The assembly of  claim 15 , wherein:
 at least one of said rings at said first axial end thereof is bent over a said first axial end of an adjacent ring in said run in position.   
     
     
         20 . An extrusion barrier assembly for a mandrel mounted sealing element in a borehole barrier, comprising:
 a plurality of nested discrete rings mounted to the mandrel having first ends of said rings nearest the mandrel and second ends, said second ends of said rings are radially actuated from a run in position adjacent said mandrel to a set position in contact with a surrounding borehole wall;   said rings comprise a plurality of axially oriented slots extending from a first axial end thereof, with said slots in adjacent rings circumferentially offset so as to avoid extrusion gaps in said set position;   said slots widen as between said run in and set positions while remaining circumferentially offset as between adjacent said rings;   said rings are rotationally locked with respect to each other to maintain said circumferential offset of said slots.   
     
     
         21 . The assembly of  claim 20 , wherein:
 said rings are rotatably mounted to said mandrel.   
     
     
         22 . The assembly of  claim 20 , wherein:
 said rings each comprise at least one axial keyway such that keyways in said rings are aligned to accept a retainer that permits relative axial movement of said rings and precludes relative rotation between said rings.   
     
     
         23 . The assembly of  claim 22 , wherein:
 said keyways begin at a second axial end opposite said first axial end.   
     
     
         24 . The assembly of  claim 20 , wherein:
 said rings are retained to said mandrel with a retainer ring further comprising a lateral opening for advancing a force regulating retainer radially against said rings to regulate the force required to relatively move said rings in an axial direction.   
     
     
         25 . The assembly of  claim 24 , wherein:
 said rings each comprise at least one axial keyway such that keyways in said rings are aligned to accept a keyway retainer that permits relative axial movement of said rings and precludes relative rotation between said rings.   
     
     
         26 . The assembly of  claim 1 , wherein:
 said rings are made from abutting or selectively attached segments.   
     
     
         27 . The assembly of  claim 15 , wherein:
 said rings are made from abutting or selectively attached segments.   
     
     
         28 . The assembly of  claim 20 , wherein:
 said rings are made from abutting or selectively attached segments.