Composite Body Lock Ring for a Borehole Plug with a Lower Slip Assembly

Abstract

A borehole plug or packer for treating is designed to be milled out after use. The plug handles differential pressure from above using a lower slip assembly under a sealing element. A setting tool creates relative axial movement of a setting sleeve and a plug mandrel to compress the seal against the surrounding tubular and set the slips moving up a cone against the surrounding tubular to define the set position for the plug. The set position is held by a split lock ring having a wedge or triangular sectional shape and a surface treatment facing the mandrel that slides along the mandrel during setting movement but resists opposed reaction force from the compressed sealing element. The surface treatment can be a series of downhole oriented ridges such as a buttress thread that preferably penetrate the mandrel when holding the set position.

1 . A plug or packer assembly for borehole use, comprising:
 a mandrel supporting a sealing element and a retaining member disposed between said sealing element and one of opposed ends of said mandrel;   a lock ring having a surface treatment facing said mandrel, said surface treatment oriented toward a second of said ends of said mandrel, said surface treatment configured for sliding contact with an outer surface of said mandrel when moving toward a first of said ends for setting said sealing element and said retaining member and said surface treatment configured to penetrate said outer surface of said mandrel when moving toward said second end.   
     
     
         2 . The assembly of  claim 1 , wherein:
 said lock ring comprising a tapered surface opposite said surface treatment.   
     
     
         3 . The assembly of  claim 1 , wherein:
 said lock ring comprises a split ring.   
     
     
         4 . The assembly of  claim 1 , wherein:
 said lock ring comprises spaced segments.   
     
     
         5 . The assembly of  claim 1 , wherein:
 said lock ring is rotationally locked to said mandrel.   
     
     
         6 . The assembly of  claim 1 , wherein:
 said surface treatment comprises a plurality of ribs oriented toward said second end, said second end oriented downhole from said first end.   
     
     
         7 . The assembly of  claim 6 , wherein:
 said ribs are parallel.   
     
     
         8 . The assembly of  claim 6 , wherein:
 said ribs comprise a spiral.   
     
     
         9 . The assembly of  claim 6 , wherein:
 said ribs comprise a thread form.   
     
     
         10 . The assembly of  claim 6 , wherein:
 said ribs are evenly or unevenly spaced.   
     
     
         11 . The assembly of  claim 1 , wherein:
 said lock ring comprises a triangle shape in section.   
     
     
         12 . The assembly of  claim 11 , wherein:
 said retaining member comprises slips;   said slips are retained to said mandrel by a slip retainer ring defining at least one undercut conforming to the shape of said lock ring.   
     
     
         13 . The assembly of  claim 12 , wherein:
 said undercut and lock ring comprise aligned tapered surfaces with respect to said outer surface of said mandrel such that movement of said slip retainer ring against said lock ring in response to a reaction force from a set said sealing element pushes said surface treatment to penetrate said outer surface of said mandrel.   
     
     
         14 . The assembly of  claim 13 , wherein:
 said tapered surfaces apply a radial and axial component forces to said surface treatment.   
     
     
         15 . The assembly of  claim 14 , wherein:
 said surface treatment comprises a plurality of ribs oriented toward said second end, said second end oriented downhole from said first end.   
     
     
         16 . The assembly of  claim 15 , wherein:
 said ribs are parallel.   
     
     
         17 . The assembly of  claim 15 , wherein:
 said ribs comprise a spiral.   
     
     
         18 . The assembly of  claim 15 , wherein:
 said ribs comprise a thread form.   
     
     
         19 . The assembly of  claim 15 , wherein:
 said ribs are evenly or unevenly spaced.   
     
     
         20 . A treatment method for borehole use, comprising
 running in a packer or plug mandrel supporting a sealing element and a retaining member disposed between said sealing element and one of opposed ends of said mandrel and a lock ring having a surface treatment facing said mandrel, said surface treatment oriented toward a second of said ends of said mandrel, said surface treatment configured for sliding contact with an outer surface of said mandrel when moving toward a first of said ends for setting said sealing element and said retaining member and said surface treatment configured to penetrate said outer surface of said mandrel when moving toward said second end;   setting said sealing element and retaining member;   pumping a treatment into the borehole against said packer or plug.   
     
     
         21 . A plug or packer assembly for borehole use, comprising:
 a mandrel supporting a sealing element and a retaining member disposed between said sealing element and one of opposed ends of said mandrel;   a lock ring facing said mandrel, comprising a surface configured for sliding contact with an outer surface of said mandrel when moving toward a first of said ends for setting said sealing element and said retaining member and said surface configured to frictionally engage using wedging action said outer surface of said mandrel when moving toward said second end.   
     
     
         22 . A treatment method for borehole use, comprising
 running in a packer or plug mandrel supporting a sealing element and a retaining member disposed between said sealing element and one of opposed ends of said mandrel and a lock ring facing said mandrel, comprising a surface configured for sliding contact with an outer surface of said mandrel when moving toward a first of said ends for setting said sealing element and said retaining member and said surface configured to frictionally engage using wedging action said outer surface of said mandrel when moving toward said second end setting said sealing element and retaining member;   pumping a treatment into the borehole against said packer or plug.