Cementing subterranean zones using cement compositions containing biodegradable dispersants

Abstract

Methods of cementing subterranean zones using cement compositions containing biodegradable dispersants are provided. The methods are basically comprised of the steps of preparing a hydraulic cement, a biodegradable dispersant comprised of polyaspartic acid containing side chains formed by reacting one or more side chain chemicals with said polyaspartic acid and sufficient water to form a pumpable slurry, placing the cement composition into a zone to be cemented and allowing the cement composition to set into an impermeable solid mass therein.

What is claimed is:  
     
         1 . A method of cementing a subterranean zone penetrated by a well bore comprising the steps of: 
 (a) preparing a cement composition comprising a hydraulic cement, a biodegradable dispersant comprised of polyaspartic acid containing side chains formed by reacting one or more side chain forming chemicals therewith and sufficient water to form a pumpable slurry;    (b) placing said cement composition in said zone to be cemented; and    (c) allowing said cement composition to set into an impermeable solid mass therein.    
     
     
         2 . The method of  claim 1  wherein said one or more side chain forming chemicals are selected from the group consisting of ethylene oxide, propylene oxide, a vinyl functional polyethylene glycol, a vinyl functional polypropylene glycol, an amino functional polyethylene glycol, a polyester, a polyamide, polyethylene oxide and polypropylene oxide.  
     
     
         3 . The method of  claim 1  wherein said side chain forming chemical is ethylene oxide.  
     
     
         4 . The method of  claim 1  wherein said side chain forming chemical is a vinyl functional polyethylene glycol.  
     
     
         5 . The method of  claim 1  wherein said side chain forming chemical is a vinyl functional polypropylene glycol.  
     
     
         6 . The method of  claim 1  wherein said side chain forming chemical is an amino functional polyethylene glycol.  
     
     
         7 . The method of  claim 1  wherein said side chain forming chemical is a polyester.  
     
     
         8 . The method of  claim 1  wherein said side chain forming chemical is a polyamide.  
     
     
         9 . The method of  claim 1  wherein said side chain forming chemical is polyethylene oxide.  
     
     
         10 . The method of  claim 1  wherein said dispersant has a molecular weight in the range of from about 5,000 to about 500,000 daltons.  
     
     
         11 . The method of  claim 1  wherein said dispersant has a molecular weight of about 10,000 daltons.  
     
     
         12 . The method of  claim 1  wherein said dispersant is present in said composition in an amount in the range of from about 0.1% to about 2.0% by weight of cement therein.  
     
     
         13 . The method of  claim 1  wherein said hydraulic cement is selected from the group consisting of Portland cements, pozzolana cements, gypsum cements, alumina cements and silica cements.  
     
     
         14 . The method of  claim 1  wherein said hydraulic cement in said composition is Portland cement.  
     
     
         15 . The method of  claim 1  wherein said water in said composition is selected from the group consisting of fresh water, unsaturated salt water and saturated salt water.  
     
     
         16 . The method of  claim 1  wherein said water is present in said composition in an amount in the range of from about 18% to about 110% by weight of cement therein.  
     
     
         17 . The method of  claim 1  wherein said composition further comprises a fluid loss control agent selected from the group consisting of hydroxyethylcellulose, hydroxymethylcellulose, carboxymethylhydroxyethylcellulose, hydroxypropylcellulose, a copolymer of 2-acrylamido-2-methyl propane sulfonic acid and N,N-dimethylacrylamide, a graft lignin a lignite polymer, starch, guar, hydroxypropylguar, polyethyleneimine, polyvinylalcohol, polyvinylacetate, carragenan and xanthane.  
     
     
         18 . The method of  claim 1  wherein said fluid loss control agent in said composition is hydroxyethylcellulose.  
     
     
         19 . The method of  claim 1  wherein said fluid loss control agent is present in said composition in an amount in the range of from about 0.2% to about 2.0% by weight of cement therein.