Remedial technique for maintaining well casing

Abstract

A method for repairing a leak in a wellbore includes determining a location of the leak in the wellbore, lowering a casing drilling tool to approximately the location of the leak, drilling a hole in a casing lining the wellbore, pumping a sealing fluid into the hole drilled in the casing, and installing a plug in the hold in the casing.

We claim: 
     
         1 . A method for reparing a leak in a wellbore, comprising:
 determining a location of the leak in the wellbore;   lowering a casing drilling tool to approximately the location of the leak;   drilling a hole in a casing lining the wellbore;   pumping a sealing fluid into the hole drilled in the casing; and   installing a plug in the hold in the casing.   
     
     
         2 . The method of  claim 1 , wherein the sealing fluid comprises cement. 
     
     
         3 . The method of  claim 1 , wherein the plug is a mechanical expansion plug able to sustain bi-directional pressure differentials. 
     
     
         4 . The method of  claim 1 , further comprising:
 setting a packer in the casing drilling tool before drilling the hole; and   wherein pumping the sealing fluid into the hole drilled in the casing comprises pumping cement from a chamber within the casing drilling tool.   
     
     
         5 . The method of  claim 1 , wherein pumping the sealing fluid into the hole drilled in the casing comprises pumping a cement from the surface through coiled tubing coupled to the cased hole drilling tool. 
     
     
         6 . The method of  claim 1 , wherein the plug is made of a material selected such that an expansion rate of the material is the same or greater than an expansion rate of the casing. 
     
     
         7 . A tool for repairing leaks in casing, comprising:
 a drill for boring through the casing;   a seal for sealing around a hole in the casing; and   a supply of sealing fluid.   
     
     
         8 . The tool of  claim 7 , wherein the supply of sealing fluid comprises cement stored in a chamber within the tool. 
     
     
         9 . The tool of  claim 7 , wherein the supply of sealing fluid comprises a reservoir of sealing fluid at a surface location connected to the tool by coiled tubing. 
     
     
         10 . The tool of  claim 7 , wherein the seal is a set of packers capable of setting above and below the hole in the casing.