Method and apparatus for controlling erosion in a downhole tool

Abstract

A drill string is comprised of a tubular element and an elastomeric element. The tubular element has an interior surface and a longitudinal axis. The elastomeric element is positioned on the interior surface of the tubular element, and includes one or more ribs extending from the interior surface of the tubular element and arranged in a configuration that diverges from the longitudinal axis of the tubular element. The ribs form an opening within the tubular element having a diameter of a preselected size substantially similar to a diameter of a tool to be positioned therein.

We claim: 
     
         1 . A drill string, comprising:
 a tubular element having an interior surface and a longitudinal axis; and   at least one elastomeric element positioned on the interior surface of the tubular element, the elastomeric element having one or more ribs extending from the interior surface of the tubular element and arranged in a configuration that diverges from the longitudinal axis of the tubular element.   
     
     
         2 . A drill string, as set forth in  claim 1 , wherein the one or more ribs form an opening within the tubular element having a diameter of a preselected size. 
     
     
         3 . A drill string, as set forth in  claim 2 , wherein the opening diameter formed by the one or more ribs is substantially similar to a diameter of a tool to be positioned therein. 
     
     
         4 . A drill string, as set forth in  claim 1 , wherein the one or more ribs are arranged in a helical configuration. 
     
     
         5 . A drill string, as set forth in  claim 1 , wherein the one or more ribs are arranged in a corkscrew configuration. 
     
     
         6 . A drill string, as set forth in  claim 1 , wherein the elastomeric element is formed from a synthetic rubber. 
     
     
         7 . A drill string, as set forth in  claim 1 , wherein the elastomeric element is formed from a synthetic rubber copolymer. 
     
     
         8 . A drill string, as set forth in  claim 1 , wherein the elastomeric element is formed from a Nitrile rubber. 
     
     
         9 . A drill string, as set forth in  claim 1 , wherein the elastomeric element is formed from a, Nitrile butadiene rubber. 
     
     
         10 . A drill string, as set forth in  claim 1 , wherein the elastomeric element is formed from acrylonitrile. 
     
     
         11 . A drill string, as set forth in  claim 1 , wherein the elastomeric element is formed from butadiene. 
     
     
         12 . A drill string, as set forth in  claim 1 , wherein the elastomeric element covers substantially the entire inner surface of the drill string. 
     
     
         13 . A method for forming an elastomeric element on an interior surface of drill string, comprising:
 positioning a mandrel within the drill string to form a void between the interior surface of the drill string and the mandrel;   injecting an elastomeric material into the void; and   removing the mandrel from the drill string.   
     
     
         14 . A method, as set forth in  claim 13 , further comprising heating the drill string prior to injecting the elastomeric element into the void. 
     
     
         15 . A method, as set forth in  claim 13 , further comprising heating the drill string during at least a portion of the time that the elastomeric element is being injected into the void. 
     
     
         16 . A method, as set forth in  claim 13 , further comprising heating the mandrel prior to injecting the elastomeric element into the void. 
     
     
         17 . A method, as set forth in  claim 13 , further comprising heating the mandrel during at least a portion of the time that the elastomeric element is being injected into the void. 
     
     
         18 . A method, as set forth in  claim 13 , wherein injecting an elastomeric material into the void further comprises injecting a synthetic rubber into the void. 
     
     
         19 . A method, as set forth in  claim 13 , wherein injecting an elastomeric material into the void further comprises injecting a synthetic rubber copolymer into the void. 
     
     
         20 . A method, as set forth in  claim 13 , wherein injecting an elastomeric material into the void further comprises injecting a Nitrile rubber into the void. 
     
     
         21 . A method, as set forth in  claim 13 , wherein injecting an elastomeric material into the void further comprises injecting a Nitrile butadiene rubber into the void.