Universal Backup for Swellable Packers

Abstract

A universal backup member is provided for use on packers and other downhole tools that use members selected for expansion upon exposure to a wellbore fluid. The backup member prevents axial extrusion of the swellable member. An elastomer portion of the backup member is selected for expansion in wellbore fluids that include both aqueous solutions and hydrocarbons, without regard to the fluid in the wellbore.

1 . An apparatus for use with a downhole tool having a swellable element, comprising:
 an attachment portion, configured for attachment of the apparatus to the downhole tool;   a ring portion, connected to the attachment portion, having an expanded condition and an unexpanded condition; and   an elastomer portion, disposed radially inwardly of the ring portion, composed of a first elastomer selected to expand upon exposure to both aqueous solutions and hydrocarbons,   wherein expansion of the elastomer portion upon exposure to an aqueous solution or a hydrocarbon urges the ring portion radially outwardly from the unexpanded condition to the expanded condition.   
     
     
         2 . The apparatus of  claim 1 , wherein the swellable element of the downhole tool is composed of a second elastomer, selected to expand upon exposure to aqueous solutions. 
     
     
         3 . The apparatus of  claim 1 , wherein the swellable element of the downhole tool is composed of a second elastomer, selected to expand upon exposure to hydrocarbons. 
     
     
         4 . The apparatus of  claim 1 , wherein the elastomer portion urges the ring portion radially outwardly from the unexpanded condition to the expanded condition responsive to axial pressure on the elastomer portion by the swellable element of the downhole tool. 
     
     
         5 . The apparatus of  claim 1 , wherein the first elastomer is an elastomeric matrix of ethylene propylene diene monomer rubber impregnated with a super absorbent polymer. 
     
     
         6 . The apparatus of  claim 1 , wherein the first elastomer is a reaction product of linear or branched polymers having residual ethylenic unsaturation with an unsaturated organic monomer having at least one reactive moiety. 
     
     
         7 . A downhole tool, comprising:
 a body;   a swellable element, disposed about the body, composed of a second elastomer selected to expand upon exposure to a predetermined wellbore fluid;   a backup unit, disposed about the body at an end of the swellable element, comprising:
 an attachment portion, attached to the body; 
 a ring portion, connected to the attachment portion, having an expanded condition and an unexpanded condition; and 
 an elastomer portion, disposed between the ring portion and the body, composed of a first elastomer selected to expand upon exposure to both aqueous solutions and hydrocarbons regardless of the predetermined wellbore fluid, 
   wherein expansion of the elastomer portion urges the ring portion radially outwardly from the unexpanded condition to the expanded condition.   
     
     
         8 . The downhole tool of  claim 7 , wherein the swellable element axially expands upon exposure to the predetermined wellbore fluid, exerting axial pressure upon the elastomer portion, and
 wherein the elastomer portion urges the ring portion radially outwardly from the unexpanded condition to the expanded condition responsive to axial pressure upon the elastomer portion by the swellable element.   
     
     
         9 . The downhole tool of  claim 7 , wherein the predetermined wellbore fluid is an aqueous solution. 
     
     
         10 . The downhole tool of  claim 7 , wherein the predetermined wellbore fluid is a hydrocarbon. 
     
     
         11 . The downhole tool of  claim 7 , wherein the first elastomer is an elastomeric matrix of ethylene propylene diene monomer rubber impregnated with a super absorbent polymer. 
     
     
         12 . The downhole tool of  claim 7 , wherein the first elastomer is a reaction product of linear or branched polymers having residual ethylenic unsaturation with an unsaturated organic monomer having at least one reactive moiety. 
     
     
         13 . A method of assembling a downhole tool, comprising:
 selecting a swellable element for the downhole tool responsive to a fluid in a wellbore;   disposing the swellable element on a body member of the downhole tool;   disposing a backup unit on the body member adjacent an end of the swellable element, the backup unit comprising:
 a ring portion having an expanded condition and an unexpanded condition; and 
 an elastomer portion, disposed between the ring portion and the body, composed of a second elastomer selected without regard to the fluid in the wellbore; and 
   attaching the backup unit to the body.   
     
     
         14 . The method of  claim 13 , wherein the act of selecting a swellable element comprises:
 selecting a swellable element designed to swell upon exposure to a hydrocarbon.   
     
     
         15 . The method of  claim 13 , wherein the act of selecting a swellable element comprises:
 selecting a swellable element designed to swell upon exposure to an aqueous solution.