Polymer compositions

Abstract

Novel polymer compositions are disclosed, along with their use as well service fluids, for example as completion fluids, work-over fluids or drilling fluids, comprising water soluable copolymers having sulfonate groups and carboxylate groups, along with alkali metal salts of carboxylic acid. Exemplary copolymer has 5 to 95 wt. % structural units derived from 2-acrylamido-2-methylpropanesulfonic acid or salt thereof, and 5 to 95 wt. % structural units derived from acrylic acid or salt thereof. A salt of the polymer may be used, such as the sodium, potassium, ammonium and calcium salts. Exemplary alkali metal salts of the polymer composition include sodium, potassium and cesium salts of formic acid and/or acetic acid in amounts suitable to develop high temperature viscosity suitable for such well servicing fluids. The polymer composition is hydrateble/soluable in a brine of sodium and/or potassium and/or cesium salts of formic and/or acetic acid.

I claim:  
     
         1 . A polymer composition comprising: 
 water soluable copolymer having functionality including at least sulfonate groups and carboxylate groups; and    alkali metal salt of carboxylic acid.    
     
     
         2 . The polymer composition of  claim 1  wherein the water soluable copolymer has a number average molecular weight of at least 1,000,000.  
     
     
         3 . The polymer composition of  claim 1  wherein the water soluable copolymer has number average molecular weight between 1,000,000 to 5,000,000.  
     
     
         4 . The polymer composition of  claim 1  wherein the water soluable copolymer is soluable in an amount of at least 4 lbs/bbl in a substantially saturated brine of alkali metal carboxylate selected from sodium, potassium and cesium salts of acetic and formic acids.  
     
     
         5 . A polymer composition comprising: 
 water soluable copolymer formed as the polymerization reaction product of acrylamidomethylpropanesulfonic acid or salt thereof and alpha, beta-unsaturated carbonyl compound; and    alkali metal salt of carboxylic acid.    
     
     
         6 . The polymer composition of  claim 5  wherein the alkali metal salt of carboxylic acid is selected from the sodium, potassium and cesium salts of C1 to C3 carboxylic acid.  
     
     
         7 . The polymer composition of  claim 5  wherein the alkali metal salt of carboxylic acid is selected from alkali metal salts of formic acid, acetic acid and mixtures thereof.  
     
     
         8 . The polymer composition of  claim 5  wherein the acrylamidomethylpropanesulfonic acid or salt thereof is 2-acrylamido-2-methylpropanesulfonic acid or salt thereof.  
     
     
         9 . The polymer composition of  claim 5  wherein the acrylamidomethylpropanesulfonic acid or salt thereof is 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulfonic acid or salt thereof.  
     
     
         10 . A polymer composition comprising: 
 water soluable copolymer comprising from 5 to 95 wt. % structural units derived from 2-acrylamido-2-methylpropanesulfonic acid or salt thereof, and from 5 to 95 wt. % structural units derived from acrylamide, vinylpyrrolidone, acrylic acid or salt thereof, and    at least one alkali metal salt of C1 to C3 carboxylic acid.    
     
     
         11 . A polymer composition of  claim 10  wherein the water soluable copolymer has 5 to 95 wt. % structural units derived from 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulfonic acid or salt thereof, and 5 to 95 wt. % structural units derived from 2-propanoic acid or salt thereof.  
     
     
         12 . The polymer composition of  claim 10  wherein the alkali metal salt is primarily cesium salt.  
     
     
         13 . The polymer composition of  claim 11  having 0 to 5 wt. % structural units derived from an at least bifunctional cross-linking agent.  
     
     
         14 . The polymer composition of  claim 13  wherein the cross-linking agent is N,N′-methylenebis[2-propenamide].  
     
     
         15 . The polymer composition of  claim 10  wherein the water soluable copolymer is present in an amount of 0.05 to 5 wt. % of the combined weight of all solids of the polymer composition and the alkali metal salt is present in an amount of 95 to 99.95 wt. % of the combined weight of all solids of the polymer composition.  
     
     
         16 . An aqueous polymer composition comprising water and the polymer composition of any of claims  1 - 15 , wherein the copolymer is substantially hydrated by the water, and the alkali metal salt of carboxylic acid is substantially dissolved.  
     
     
         17 . The polymer composition of  claim 16  further comprising alkali metal salt of at least 1 halide.  
     
     
         18 . The polymer composition of  claim 16  wherein the alkali metal salt of at least 1 halide is selected from the sodium, potassium and cesium salts of chloride, bromide and mixtures thereof.  
     
     
         19 . The aqueous polymer composition of  claim 16  developing an apparent viscosity of at least 20 cPs., a plastic viscosity of at least 15 cPs, and a yield point of at least 5 lb./100 ft 2  when dissolved in cesium formate brine at a concentration of 2 pounds per barrel and measured at 120 degrees F.  
     
     
         20 . The aqueous polymer composition of  claim 19  retaining at least 50 percent of its apparent viscosity after roller aging for 30 days at 375 degrees F. and measured at 120 degrees F.  
     
     
         21 . A process for preparing an aqueous polymer composition according to  claim 16  comprising hydrating a polymer composition in accordance with any of claims  1 - 15 .  
     
     
         22 . A process for preparing an aqueous polymer composition according to  claim 21  wherein alkali metal salt of carboxylic acid is dissolved aqueous composition containing the water soluable copolymer.  
     
     
         23 . A process for preparing an aqueous polymer composition according to  claim 21  wherein the water soluable copolymer is dissolved in a brine of alkali metal salt of carboxylic acid.  
     
     
         24 . An aqueous well service fluid comprising: 
 water soluable copolymer having functionality including at least sulfonate groups and carboxylate groups, substantially fully hydrated in a brine solution.    
     
     
         25 . A method of carrying out well-drilling or well-servicing operations comprising the use of an aqueous well service fluid comprising water soluable copolymer having functionality including at least sulfonate groups and carboxylate groups, substantially fully hydrated in a brine solution.  
     
     
         26 . An aqueous well servicing fluid comprising water soluable copolymer having functionality including at least sulfonate groups and carboxylate groups, which copolymer is soluable in a brine of alkali metal salt of carboxylic acid.