Gel formation by polymer crosslinking

Claim 1

A composition capable of forming a gel for treating underground formations at a slow rate of gelling by crosslinking, said composition consisting essentially of gel forming amounts of: a. water; b. a water thickening amount of a water dispersible polymer selected from among the group consisting of substantially linear homopolymers and copolymers of acrylamide and methacrylamide, cellulose ethers, and heteropolysaccharides produced by fermentation of carbohydrates by bacteria of the genus Xanthomonas, said polymer capable of being crosslinked by polyvalent metal cations; c. a polyvalent metal component chosen from the group consisting of hexavalent chromium compounds and heptavalent manganese compounds in a reducible oxidation state; and d. a reducing agent selected from among the group consisting of MnCl 2 , KI, K 4 Fe(CN) 6 and Mn(NO 3 ) 2 .

Claim 9

A method for forming a gel for treating underground formations, said gel capable of gelling at a slow rate, comprising contacting a solution consisting essentially of a gel forming amount of water, and a water thickening amount of a water dispersible polymer selected from among the group consisting of substantially linear homopolymers and copolymers of acrylamide and methacrylamide, cellulose ethers, and heteropolysaccharides produced by fermentation of carbohydrates by bacteria of the genus Xanthomonas, said polymer capable of being crosslinked by polyvalent metal cations with an amount of a redox system capable of initiating gelling, said redox system consisting essentially of a reducible polyvalent metal component chosen from the group consisting of hexavalent chromium compounds and heptavalent manganese compounds and a reducing agent selected from the group consisting of MnCl 2 , KI, Mn(NO 3 ) 2 , and K 4 Fe(CN) 6 .

Claim 10

A method for forming a gel for treating underground formations, said gel capable of gelling at a slow rate, comprising contacting a solution consisting essentially of a gel forming amount of water, and a water thickening amount of a water dispersible polymer selected from among the group consisting of substantially linear homopolymers and copolymers of acrylamide and methacrylamide, cellulose ethers, and heteropolysaccharides produced by fermentation of carbohydrates by bacteria of the genus Xanthomonas, said polymer capable of being crosslinked by polyvalent metal cations with an amount of a redox system capable of initiating gelling, said redox system consisting essentially of a reducible polyvalent metal component chosen from the group consisting of hexavalent chromium compounds and heptavalent manganese compounds and a reducing agent selected from the group consisting of MnCl 2 , KI, Mn(NO 3 ) 2 , and K 4 Fe(CN) 6 .