Compositions and Methods for Well Treatment

Abstract

A self-healing cement for use in wells in which carbon dioxide is injected, stored or extracted, comprises a carbonaceous material. In the event of cement-matrix failure, or bonding failure between the cement/casing interface or the cement/borehole-wall interface, the material swells when contacted by carbon dioxide. The swelling seals voids in the cement matrix, or along the bonding interfaces, thereby restoring zonal isolation.

1 . A method comprising: (i) including a carbonaceous material in a pumpable cement slurry; (ii) pumping said slurry downhole; (iii) allowing the slurry to set thus forming a cement sheath that will self repair when contacted by carbon dioxide. 
     
     
         2 . The method of  claim 1 , wherein the carbonaceous material is petroleum coke. 
     
     
         3 . A method for maintaining zonal isolation in a subterranean well having a borehole in which carbon dioxide is injected, stored or extracted, comprising the following steps:
 (i) installing a tubular body inside the borehole of the well, or inside a previously installed tubular body;   (ii) pumping aqueous cement slurry comprising a material that swells when contacted by carbon dioxide into the borehole;   (iii) allowing the cement slurry to set and harden;   (iv) in the event of cement-matrix or bonding failure, exposing the set cement to wellbore fluids that contain carbon dioxide; and   (v) allowing the material to swell, thereby restoring zonal isolation.   
     
     
         4 . A method for cementing a subterranean well having a borehole in which carbon dioxide is injected, stored or extracted, comprising the following steps:
 (i) installing a tubular body inside the borehole of the well, or inside a previously installed tubular body;   (ii) pumping an aqueous cement slurry comprising a material that swells when contacted by carbon dioxide into the borehole; and   (iii) allowing the cement slurry to set and harden inside the annular region.   
     
     
         5 . The method of  claim 4 , wherein the cementing process is primary cementing, and the cement slurry is either pumped down the interior of the tubular body and up through the annular region, or down the annular region and up the interior of the tubular body. 
     
     
         6 . The method of  claim 4 , wherein the cementing process is remedial cementing, performed in either a cased or open hole. 
     
     
         7 . The method of  claim 3 , wherein the material is a carbonaceous material. 
     
     
         8 . The method of  claim 3 , wherein the material comprises one or more members of the list comprising coal, petroleum coke, graphite and gilsonite. 
     
     
         9 . The method of  claim 3 , wherein the concentration of the material in the cement matrix is between about 5 percent and about 50 percent by volume of solid blend (BVOB). 
     
     
         10 . The method of  claim 3 , wherein the concentration of the material in the cement matrix is between about 10 percent and 40 percent by volume of solid blend (BVOB). 
     
     
         11 . The method of  claim 3 , wherein the particle-size-distribution of the material is such that the minimum d 10  is about 100 μm, and the maximum d 90  is about 850 μm. 
     
     
         12 . The method of  claim 3 , wherein the cement comprises one or more members of the list comprising Portland cement, calcium aluminate cement, fly ash, blast furnace slag, lime-silica blends, geopolymers, Sorel cements and chemically bonded phosphate ceramics. 
     
     
         13 . The method of  claim 3 , wherein the cement slurry further comprises one or more members of the list comprising dispersing agents, fluid-loss-control agents, set retarders, set accelerators and antifoaming agents. 
     
     
         14 . The method of  claim 3 , wherein the tubular body comprises one or more members of the list comprising drillpipe, casing, liner and coiled tubing. 
     
     
         15 . The method of  claim 3 , wherein the borehole penetrates at least one fluid-containing reservoir, the reservoir containing fluid with a carbon dioxide concentration greater than about five moles per liter. 
     
     
         16 . The method of  claim 4 , wherein the material comprises one or more members of the list comprising coal, petroleum coke, graphite and gilsonite. 
     
     
         17 . The method of  claim 4 , wherein the concentration of the material in the cement matrix is between about 5 percent and about 50 percent by volume of solid blend (BVOB). 
     
     
         18 . The method of  claim 4 , wherein the particle-size-distribution of the material is such that the minimum d 10  is about 100 μm, and the maximum d 90  is about 850 μm. 
     
     
         19 . The method of  claim 4 , wherein the cement comprises one or more members of the list comprising Portland cement, calcium aluminate cement, fly ash, blast furnace slag, lime-silica blends, geopolymers, Sorel cements and chemically bonded phosphate ceramics. 
     
     
         20 . The method of  claim 4 , wherein the borehole penetrates at least one fluid-containing reservoir, the reservoir containing fluid with a carbon dioxide concentration greater than about five moles per liter.