In situ decomposition of carbonyls at high temperature for fixing incomplete and failed well seals

Abstract

Methods and systems relating to in situ decomposition of carbonyls at high temperature for fixing incomplete and failed well seals, are described. According to one embodiment, a method, comprises injecting a sealing agent into a subterranean well having sealing channels or voids in well casings. An alkaline-earth carbonate precipitate is formed from the decomposition of a carbonyl compound. The sealing agent includes the carbonyl compound and an alkaline-earth halide salt.

What is claimed is: 
     
         1 . A method, comprising:
 injecting a sealing agent into a subterranean well, wherein the subterranean well comprises a first void between a first well casing layer and a subterranean formation, and wherein the sealing agent comprises a carbonyl compound; and   forming a carbonate precipitate from decomposition of the carbonyl compound.   
     
     
         2 . The method of  claim 1 , further comprising sealing the first void with the carbonate precipitate. 
     
     
         3 . The method of  claim 1 , further comprising sealing a second void with the carbonate precipitate, wherein the subterranean well comprises the second void between a second well casing layer and the first well casing layer, and wherein the second well casing layer is smaller than the first well casing layer. 
     
     
         4 . The method of  claim 1 , further comprising adding an alkaline-earth halide salt to the sealing agent to form an alkaline-earth carbonate precipitate from decomposition of the carbonyl compound in the presence of the alkaline-earth halide salt. 
     
     
         5 . The method of  claim 1 , wherein the carbonyl compound is urea. 
     
     
         6 . The method of  claim 1 , wherein the carbonyl compound is dimethyl carbonate. 
     
     
         7 . The method of  claim 3 , wherein the alkaline-earth halide salt comprises one or more of calcium chloride, magnesium chloride, calcium bromide, calcium iodide, magnesium bromide, and magnesium iodide. 
     
     
         8 . The method of  claim 1 , wherein the carbonyl compound has a molar concentration of 0.01 M to 100 M. 
     
     
         9 . The method of  claim 3 , wherein the alkaline-earth halide salt has a molar concentration of 0.01 M to 100 M. 
     
     
         10 . The method of  claim 3 , wherein the carbonyl compound to alkaline-earth halide salt molar ratio has a range of 100:1 to 1:100. 
     
     
         11 . The method of  claim 1 , wherein the void is associated with debonding between a cement sheath and the first well casing layer, and wherein the cement sheath is between the first well casing layer and the subterranean formation. 
     
     
         12 . The method of  claim 1 , wherein the void is associated with debonding between a cement sheath and the subterranean formation, wherein the cement sheath is between the first well casing layer and the subterranean formation. 
     
     
         13 . The method of  claim 1 , wherein the void is associated with a crack in a cement sheath, wherein the cement sheath is between the first well casing layer and the subterranean formation. 
     
     
         14 . The method of  claim 1 , wherein the void is part of a lost circulation zone. 
     
     
         15 . The method of  claim 1 , wherein the decomposition occurs at a temperature of about 135° C. or more. 
     
     
         16 . The method of  claim 1 , further comprising dissolving the carbonate precipitate by exposing the carbonate precipitate to an acid solution. 
     
     
         17 . The method of  claim 15 , wherein the acid solution comprises one or more of hydrochloric acid, acetic acid, formic acid, citric acid, oxalic acid, nitrilotriacetic acid (NTA), ethylenediamine tetraacetic acid (EDTA) and diethylenetriamine pentaacetic acid (DTPA). 
     
     
         18 . The method of  claim 1 , further comprising controlling a temperature of a selected portion of the subterranean well to control a degree of precipitation of the carbonate precipitate in a region adjacent the selected portion. 
     
     
         19 . The method of  claim 1 , wherein the subterranean well is a geothermal well. 
     
     
         20 . The method of  claim 1 , wherein the subterranean well is a petroleum well. 
     
     
         21 . The method of  claim 1 , wherein the sealing agent further comprises one or more of a flow control additive, a catalyst, a nucleation enhancer, a viscosity flow modifier, and a filler. 
     
     
         22 . The method of  claim 20 , wherein the flow control additive comprises one or more of an inert particulate, clay and a thermally stable polymer. 
     
     
         23 . The method of  claim 20 , wherein the flow control additive comprises particulate calcium carbonate, which also acts as a nucleation seed for the carbonate precipitate. 
     
     
         24 . The method of  claim 1 , further comprising monitoring the temperature of a selected region in the subterranean well by inserting a temperature monitoring tool into the selected region. 
     
     
         25 . The method of  claim 23 , wherein the temperature monitoring tool is a fiber optic tube. 
     
     
         26 . The method of  claim 1 , wherein injecting the sealing agent into the subterranean well comprises using pressure to force the sealing agent into the void. 
     
     
         27 . The method of  claim 25 , wherein the pressure has a range of hydrostatic to 5000 psi.