Chrome free water-based wellbore fluid

Abstract

Methods for maintaining the rheology and reducing the fluid loss of chrome-free, aqueous-based wellbore fluids under high temperature-high pressure conditions are disclosed. The method may comprise formulating the chrome-free, aqueous wellbore fluid with an aqueous base fluid, at least one chrome-free viscosifier, at least one chrome-free fluid loss control additive, at least one chrome-free dispersant; and circulating the chrome-free aqueous-based wellbore fluid in a wellbore at temperatures exceeding 300° F.

1 . A method for maintaining the rheology and reducing the fluid loss of a chrome-free, aqueous-based wellbore fluid under high temperature-high pressure conditions, comprising:
 formulating the chrome-free, aqueous-based wellbore fluid comprising:
 an aqueous base fluid; 
 at least one chrome-free viscosifier; 
 at least one chrome-free fluid loss control additive; and 
 at least one chrome-free dispersant, wherein the circulated chrome-free aqueous-based wellbore fluid has a thermal plastic viscosity less than 70 cP and a fluid loss less than 20 mL and 
   circulating the chrome-free, aqueous-based wellbore fluid in a wellbore at temperatures exceeding 300° F.   
     
     
         2 . The method of  claim 1 , wherein the at least one chrome-free viscosifier is a natural or synthetic clay selected from the group consisting of sepiolite, hectorite, attapulgite, montmorillonite, and combinations thereof. 
     
     
         3 . The method of  claim 1 , wherein the at least one chrome-free fluid loss control additive comprises a polyacrylamide. 
     
     
         4 . The method of  claim 3 , wherein the polyacrylamide is selected from the group consisting of:
 a terpolymer of acrylamide, sulfonated monomer, and vinylpyrrolidone,   a copolymer of acrylamido sulfonic acid and acrylamide,   and combinations thereof.   
     
     
         5 . The method of  claim 1 , wherein the at least one chrome-free dispersant comprises a lignosulfonate. 
     
     
         6 . The method of  claim 5 , wherein the lignosulfonate is selected from the group consisting of resinated sulfonated lignite, oxidized lignite, and combinations thereof. 
     
     
         7 . The method of  claim 1 , wherein the chrome-free, aqueous-based wellbore fluid further comprises at least one chrome-free high-temperature rheology stabilizer. 
     
     
         8 . The method of  claim 7 , wherein the at least one chrome-free high temperature rheology stabilizer is selected from the group consisting of copolymers based on polyacrylate and polyacrylamide; copolymers of vinylamide and vinylsulfonate; and
 combinations thereof.   
     
     
         9 . The method of  claim 1 , wherein the chrome-free, aqueous-based wellbore fluid further comprises a copolymer of starch and latex. 
     
     
         10 . The method of  claim 1 , wherein the at least fluid loss control additive comprises a vinyl-based copolymer. 
     
     
         11 . A method of decreasing gelation of a chrome-free aqueous wellbore fluid in a high temperature, high pressure environment, comprising:
 formulating the chrome-free aqueous wellbore fluid comprising
 an aqueous base fluid; 
 at least one chrome-free viscosifier; 
 at least one chrome-free fluid loss control additive; and 
 at least one chrome-free dispersant, wherein the chrome-free aqueous wellbore fluid preferably has a static shear strength less than 200 pounds per 100 square feet (lb/100 ft 2 ), and a 10-minute gel less than 40 pounds per 100 square feet (lb/100 ft 2 ); and 
   circulating the chrome-free aqueous wellbore fluid in a wellbore at temperature of at least 300° F.   
     
     
         12 . The method of  claim 11 , wherein the at least one chrome-free viscosifier is a natural or synthetic clay is selected from the group consisting of sepiolite, hectorite, attapulgite, montmorillonite, and combinations thereof. 
     
     
         13 . The method of  claim 11 , wherein the at least one fluid loss control additive comprises polyacrylamide. 
     
     
         14 . The method of  claim 13 , wherein the polyacrylamide is selected from the group consisting of:
 a terpolymer of acrylamide, sulfonated monomer, and vinylpyrrolidone,   a copolymer of acrylamido sulfonic acid and acrylamide,   and combinations thereof.   
     
     
         15 . The method of  claim 11 , wherein the at least one chrome-free dispersant comprises a lignosulfonate. 
     
     
         16 . The method of  claim 15 , wherein the lignosulfonate is selected from the group consisting of resinated sulfonated lignite, oxidized lignite, and combinations thereof. 
     
     
         17 . The method of  claim 11 , wherein the chrome-free, aqueous wellbore fluid further comprises at least one chrome-free high temperature rheology stabilizer. 
     
     
         18 . The method of  claim 17 , wherein the at least one high temperature rheology stabilizer is selected from the group consisting of copolymers based on polyacrylate and polyacrylamide; copolymers of vinylamide and vinylsulfonate; and combinations thereof. 
     
     
         19 . The method of  claim 11 , wherein the chrome-free, aqueous wellbore fluid further comprises a copolymer of starch and latex. 
     
     
         20 . The method of  claim 11 , wherein the at least fluid loss control additive comprises a vinyl-based copolymer.