Patent ID: 6855672

Claim:
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) R 1 is an OH or NH 2 ; (c) R 2 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.