Downhole plug

Abstract

A downhole plug, has an inner mandrel and a sealing assembly carried on and surrounding an outer surface of the inner mandrel. The sealing assembly is positioned between a lower support downstream of the sealing assembly and a setting shoulder upstream of the sealing assembly. The sealing assembly is activated from a deactivated state to a sealing state by causing the setting shoulder and the lower support to apply a compressive force to the sealing assembly such that an elastomeric seal extrudes outward into sealing engagement with an inner surface of a tubular. The lower support has a series of expandable segments mounted by a frangible connection, such that, as the compressive force is applied, the expandable segments break away from the lower support and move outward into engagement with the inner surface of the tubular.

What is claimed is: 
     
         1 . A downhole plug, comprising:
 an inner mandrel;   a sealing assembly carried on and surrounding an outer surface of the inner mandrel, the sealing assembly being positioned between a lower support downstream of the sealing assembly and a setting shoulder upstream of the sealing assembly;   wherein the sealing assembly is activated from a deactivated state to a sealing state by causing the setting shoulder and the lower support to apply a compressive force to the sealing assembly such that an elastomeric seal extrudes outward into sealing engagement with an inner surface of a tubular; and   the lower support comprising a series of expandable segments mounted by a frangible connection, such that, as the compressive force is applied, the expandable segments break away from the lower support and move outward into engagement with the inner surface of the tubular.   
     
     
         2 . The downhole plug of  claim 1 , wherein the elastomeric seal comprises two or more elastomeric seals having different durometers. 
     
     
         3 . The downhole plug of  claim 1 , wherein each expandable segment has an outer face that engages the inner surface of the tubular, an upper face oriented toward the setting shoulder that engages an anti-extrusion ring of the sealing assembly, and a lower face opposite the upper face that engages a sloped support surface of the lower support, wherein an angle of the outer face relative to the lower face is such that, as the expandable segments break away from the lower support, the lower face engages and moves along the sloped support surface until the outer face is flush with the inner surface of the tubular. 
     
     
         4 . The downhole plug of  claim 3 , wherein the lower face is angled downstream moving radially outward, and the upper face of each expandable segment is angled upstream moving radially outward. 
     
     
         5 . The downhole plug of  claim 1 , wherein the series of expandable segments are mounted to a mounting ring or are integrally formed with the lower support. 
     
     
         6 . A downhole plug, comprising:
 an inner mandrel; and   a sealing mechanism carried on and surrounding an outer surface of the inner mandrel, the sealing mechanism comprising:
 a lower support; 
 an anti-extrusion ring adjacent to and upstream of the lower support, the anti-extrusion ring being made from a flexible, non-elastomeric material; 
 a robust elastomer and an energizing elastomer upstream of the anti-extrusion ring, the robust elastomer being disposed between the energizing elastomer and the anti-extrusion ring, and the robust elastomer having a higher durometer than the energizing elastomer, the robust elastomer extending upstream toward an outer edge of the robust elastomer such that a portion of the robust elastomer overlies a portion of the energizing elastomer; and 
 a setting shoulder upstream of the energizing elastomer; 
   wherein the sealing mechanism is activated from a deactivated state to a sealing state by causing the setting shoulder and the lower support to apply a compressive force to the robust elastomer and the energizing elastomer such that the robust elastomer and the energizing elastomer extrude outward into sealing engagement with an inner surface of a tubular.   
     
     
         7 . The downhole plug of  claim 6 , wherein the lower support comprising a series of expandable segments mounted by a frangible connection, such that, as the compressive force is applied, the expandable segments break away from the lower support and move outward into engagement with the inner surface of the tubular. 
     
     
         8 . The downhole plug of  claim 7 , wherein each expandable segment has an outer face that engages the inner surface of the tubular, an upper face oriented toward the setting shoulder that engages an anti-extrusion ring of the sealing mechanism, and a lower face opposite the upper face that engages a sloped support surface of the lower support, wherein an angle of the outer face relative to the lower face is such that, as the expandable segments break away from the lower support, the lower face engages and moves along the sloped support surface until the outer face is flush with the inner surface of the tubular. 
     
     
         9 . The downhole plug of  claim 8 , wherein the lower face is angled downstream moving radially outward, and the upper face of each expandable segment is angled upstream moving radially outward. 
     
     
         10 . A slip assembly for a downhole plug, comprising:
 a body comprising a plurality of slip segments connected by a frangible web, wherein:
 each slip segment comprises an outer engagement surface that define an outer cylindrical surface; 
 the body defines an inner tapered surface that has a larger diameter at an upstream end of the body and a smaller diameter at a downstream end; 
 the frangible web comprises a portion of the inner tapered surface between adjacent slip segments at the upstream end of the body; 
 the slip segments are separated by pushing the inner tapered surface axially against a ramp surface such that the frangible web fractures and such that the fractured frangible web extends across a portion of a space between adjacent slip segments. 
   
     
     
         11 . The slip assembly of  claim 10 , wherein the frangible web has a length that is shorter than a length of the body.