Continuous Backup Assembly for High Pressure Seals

Abstract

An extrusion barrier assembly for high pressure and temperature applications for a sealing element incorporates a backing member between the sealing element and a multi-row petal type backup ring assembly. The surface irregularities of the offset petals are distributed through the backing member so that stress concentration locations at the petal transitions between rows are diffused through the backing member to avoid or minimize the tendency of the petals to stress crack at row to row transitions. The backing member is formed from spirally wound strip of sheet material that can be coated to promote relative sliding of overlapping layers. The assembly can be temporarily bonded to retain its shape with adhesive that releases under expected well conditions when the packer or bridge plug is set.

I claim: 
     
         1 . An extrusion barrier assembly for a subterranean seal, comprising:
 a seal element having a longitudinal axis;   a backup ring assembly located adjacent at least one end of said seal element;   a backup member disposed between said backup ring assembly and said seal element and formed from an elongated strip rolled into overlapping layers.   
     
     
         2 . The assembly of  claim 1 , wherein:
 said strip is spirally wound so that adjacent layers are offset from each other.   
     
     
         3 . The assembly of  claim 1 , wherein:
 said layers slide relatively upon compressive loading of said seal element along the longitudinal axis of said element.   
     
     
         4 . The assembly of  claim 1 , wherein:
 said layers are initially secured to each other with an adhesive.   
     
     
         5 . The assembly of  claim 1 , wherein:
 said layers have a coating in between that reduces friction to promote relative sliding between said layers.   
     
     
         6 . The assembly of  claim 1 , wherein:
 said backup member conforms to the shape of said petal backup ring at a contact location.   
     
     
         7 . The assembly of  claim 1 , wherein:
 said petal backup ring provides structural support for said backup member.   
     
     
         8 . The assembly of  claim 1 , wherein:
 said strip is continuous throughout said layers.   
     
     
         9 . The assembly of  claim 1 , wherein:
 said backup member has a frusto-conical shape.   
     
     
         10 . The assembly of  claim 9 , wherein:
 said shape comprising an axis and a taper slope angle of 5-60° with respect to said axis.   
     
     
         11 . The assembly of  claim 1 , wherein:
 spaced petal pairs in one row of said petal backup ring are backed by another petal in an adjacent row to define step transitions at adjacent edges of said spaced petals;   said backup member spanning said step transitions of said spaced petal pairs to reduce stress at said step transitions from compressive loading in a direction of said longitudinal axis of said sealing element.   
     
     
         12 . The assembly of  claim 2 , wherein:
 said layers slide relatively upon compressive loading of said seal element along the longitudinal axis of said element.   
     
     
         13 . The assembly of  claim 12 , wherein:
 said strip is continuous throughout said layers.   
     
     
         14 . The assembly of  claim 13 , wherein:
 said backup member has a frusto-conical shape.   
     
     
         15 . The assembly of  claim 14 , wherein:
 spaced petal pairs in one row of said petal backup ring are backed by another petal in an adjacent row to define step transitions at adjacent edges of said spaced petals;   said backup member spanning said step transitions of said spaced petal pairs to reduce stress at said step transitions from compressive loading in a direction of said longitudinal axis of said sealing element.   
     
     
         16 . The assembly of  claim 15 , wherein:
 said layers are initially secured to each other with an adhesive.   
     
     
         17 . The assembly of  claim 16 , wherein:
 said layers have a coating in between that reduces friction to promote relative sliding between said layers.   
     
     
         18 . The assembly of  claim 17 , wherein:
 said backup member conforms to the shape of said petal backup ring at a contact location.   
     
     
         19 . The assembly of  claim 18 , wherein:
 said petal backup ring provides structural support for said backup member.   
     
     
         20 . The assembly of  claim 19 , wherein:
 said shape comprising a axis and a taper slope angle of 5-60° with respect to said axis.   
     
     
         21 . The assembly of  claim 1 , wherein:
 said backup ring assembly comprises a petal backup ring assembly further comprising at least two rows of circumferentially offset petals and located adjacent at least one end of said seal element.   
     
     
         22 . The assembly of  claim 1 , wherein:
 said backup ring assembly comprises at least one ring with abrupt surface transitions.   
     
     
         23 . The assembly of  claim 1 , wherein:
 said backup ring assembly comprises a plurality of split rings with circumferentially spaced splits.