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Disclosed is a copolymer useful for preparing acid gels comprising a copolymer having a copolymer backbone, the copolymer having a general formula: wherein: (a) A is an H or other terminating group; (b) R1 is an OH or NH2; (c) R2 is an O or NH; (d) Z is an integer having a value of from 1 to 4; (e)

Disclosed is a copolymer useful for preparing acid gels comprising a copolymer having a copolymer backbone, the copolymer having a general formula: wherein: (a) A is an H or other terminating group; (b) R1 is an OH or NH2; (c) R2 is an O or NH; (d) Z is an integer having a value of from 1 to 4; (e) X and Y are present in a ratio (X:Y) of from 3:2 to 4:1; (f) structures I and II are present as blocks or randomly distributed along the copolymer backbone; and wherein the copolymer has a molecular weight of from about 1,000,000 to about 10,000,000.

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1. A method for fracturing a subterranean formation, the subterranean formation being in fluid communication with the surface through a well bore, comprising:(a) creating a fracture in a subterranean formation; and (b) injecting into the fracture an etching agent, wherein the etching agent includes

1. A method for fracturing a subterranean formation, the subterranean formation being in fluid communication with the surface through a well bore, comprising:(a) creating a fracture in a subterranean formation; and (b) injecting into the fracture an etching agent, wherein the etching agent includes a gelled acid comprising an acid gelled using a copolymer having a backbone, the organic component of the gelled acid having the general formula: wherein:(a) A is an H or other terminating group; (b) R1 is an OH or NH2; (c) R2 is an O or NH; (d) Z is an integer having a value of from 1 to 4; (e) X and Y are present in a ratio (X:Y) of from 3:2 to 4:1; (f) structures I and II are present as blocks or randomly distributed along the copolymer backbone; (g) D?is an anion of a mineral acid; and wherein the copolymer has a molecular weight of from about 1,000,000 to about 10,000,000. 2. The method of claim 1 wherein, in the general formula for the copolymer, R1 is NH2.3. The method of claim 1 wherein, in the general formula for the copolymer, Z is an integer having a value of from 2 to 3.4. The method of claim 3 wherein, in the general formula for the copolymer, Z is an integer having a value of 2.5. The method of claim 4 wherein the copolymer has a molecular weight of from about 1,000,000 to about 6,000,000.6. The method of claim 1 wherein the mineral acid is selected from the group consisting of sulfuric, nitric, hydrochloric, and phosphoric acid.7. The method of claim 6 wherein the mineral acid is selected from the group consisting of sulfuric and hydrochloric acid.8. The method of claim 1 wherein the etching agent includes an additive selected from the group consisting of emulsifiers, chelators, surfactants, proppants, delay additives, biocides, corrosion inhibitors, and mixtures thereof.9. The method of claim 1 wherein the etching agent includes a proppant.10. The method of claim 1 wherein the copolymer is prepared using a formulation comprising:(a) a first vinyl component selected from the group consisting of acrylamide, acrylic acid, and mixtures thereof; and (b) a second vinyl component selected from dimethylaminoethyl methacrylate, dimethylaminoethyl methacrylamide, dimethylaminopropyl methacrylamide, and mixtures thereof; and additionally comprising a crosslinking agent.11. The method of claim 10 wherein the crosslinking agent is bis-acrylamide.12. The method of claim 11 wherein the bis-acrylamide is present in a concentration of less than about 250 parts per million.13. The method of claim 11 wherein the bis-acrylamide is present in a concentration of less than about 200 parts per million.14. The method of claim 11 wherein the bis-acrylamide is present in a concentration of less than about 100 parts per million.