Continuous permeability reduction in subterranean reservoirs

Claim 1

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogenous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a crosslinking agent for the polymer capable of reacting with said polymer to produce a gel in an alkaline media; (3) a source of hydroxyl ions in an amount sufficient to retard the reaction of said polymer with said cross-linking agent; and (4) an additive capable of sufficiently reducing the pH of said aqueous liquid at an ambient elevated temperature so as to initiate or accelerate reaction of said polymer and said cross-linking agent.

Claim 2

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogenous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a crosslinking agent for the polymer capable of reacting with said polymer to produce a gel in an alkaline media; (3) a source of hydroxyl ions in an amount sufficient to retard the reaction of said polymer with said cross-linking agent; and (4) an additive capable of sufficiently reducing the pH of said aqueous liquid at an ambient elevated temperature so as to initiate or accelerate reaction of said polymer and said cross-linking agent.

Claim 3

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a crosslinking agent for the polymer capable of reacting with said polymer to produce a gel in an alkaline media; (3) an alkaline material in an amount sufficient to retard the reaction of said polymer with said cross-linking agent; and (4) an additive capable of sufficiently reducing the pH of said aqueous liquid at an elevated temperature so as to accelerate reaction of said polymer and said cross-linking agent at the elevated temperature.

Claim 4

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a crosslinking agent for the polymer capable of reacting with said polymer to produce a gel in an alkaline media; (3) an alkaline material in an amount sufficient to retard the reaction of said polymer with said cross-linking agent; and (4) an additive capable of sufficiently reducing the pH of said aqueous liquid at an elevated temperature so as to accelerate reaction of said polymer and said cross-linking agent at the elevated temperature.

Claim 5

A method for reducing the permeability of the higher permeable zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a crosslinking agent for the polymer capable of reacting with said polymer to produce a gel at a pH below about 9.2 but not above about 9.2; (3) an alkaline material in an amount sufficient to raise the pH of said liquid above about 10.0 in the absence of the additive hereinafter defined; and (4) an additive capable of reducing the pH of said aqueous liquid to a pH below about 9.2 to initiate gelation of said polymer and said crosslinking agent, said additive being further capable of reducing the pH at a faster rate at an elevated temperature than at ambient temperature.

Claim 6

A method for reducing the permeability of the higher permeable zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a crosslinking agent for the polymer capable of reacting with said polymer to produce a gel at a pH below about 9.2 but not above about 9.2; (3) an alkaline material in an amount sufficient to raise the pH of said liquid above about 10.0 in the absence of the additive hereinafter defined; and (4) an additive capable of reducing the pH of said aqueous liquid to a pH below about 9.2 to initiate gelation of said polymer and said crosslinking agent, said additive being further capable of reducing the pH at a faster rate at an elevated temperature than at ambient temperature.

Claim 7

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a crosslinking agent for the polymer capable of substantial reaction with said polymer to produce a gel only below a fixed pH above 7.0; (3) an alkaline material in an amount sufficient to raise the pH of said liquid above said fixed pH in the absence of the additive hereinafter defined; and (4) an additive capable of sufficiently reducing the pH of said aqueous liquid to a pH below the fixed pH to initiate gelation of said polymer and said cross-linking agent, said additive being further capable of reducing the pH at a faster rate at an elevated temperature than at ambient temperature.

Claim 8

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a crosslinking agent for the polymer capable of substantial reaction with said polymer to produce a gel only below a fixed pH above 7.0; (3) an alkaline material in an amount sufficient to raise the pH of said liquid above said fixed pH in the absence of the additive hereinafter defined; and (4) an additive capable of sufficiently reducing the pH of said aqueous liquid to a pH below the fixed pH to initiate gelation of said polymer and said cross-linking agent, said additive being further capable of reducing the pH at a faster rate at an elevated temperature than at ambient temperature.

Claim 10

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition for reducing the permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising an aqueous liquid containing (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a crosslinking agent for the polymer selected from the group consisting of an alkali metal or ammonium aluminates and gallates, (3) an amount of a water-soluble alkaline material selected from the group consisting of alkali metal and ammonium hydroxides, alkali metal silicates, sodium carbonate and alkali metal phosphates sufficient to raise the pH of the overall aqueous liquid to that at which the cross-linking material is substantially unreactive with the polymer, and (4) an amount of a water-soluble temperature-activated acidic material dissolved in the aqueous liquid sufficient to lower the pH of said liquid to that at which a cross-linking reaction occurs when said liquid is subjected to an elevated temperature.

Claim 11

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir a composition for reducing the permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising an aqueous liquid containing (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a crosslinking agent for the polymer selected from the group consisting of an alkali metal or ammonium aluminates and gallates, (3) an amount of a water-soluble alkaline material selected from the group consisting of alkali metal and ammonium hydroxides, alkali metal silicates, sodium carbonate and alkali metal phosphates sufficient to raise the pH of the overall aqueous liquid to that at which the cross-linking material is substantially unreactive with the polymer, and (4) an amount of a water-soluble temperature-activated acidic material dissolved in the aqueous liquid sufficient to lower the pH of said liquid to that at which a cross-linking reaction occurs when said liquid is subjected to an elevated temperature.

Claim 12

A method for reducing the permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through said well and into said reservoir an aqueous liquid containing (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a cross-linking agent for the polymer selected from the group consisting of alkali metal or ammonium aluminates and gallates, (3) an amount of a water-soluble alkaline material selected from the group consisting of alkali metal and ammonium hydroxides, alkali metal silicates, alkali metal and ammonium carbonates, and alkali metal phosphates sufficient to raise the pH of the overall aqueous liquid to that at which the cross-linking material is substantially unreactive with the polymer, and (4) an amount of a water-soluble temperature-activated acidic material dissolved in the aqueous liquid sufficient to accelerate a cross-linking reaction between said polymer and said cross-linking agent when said liquid is subjected to an elevated temperature.

Claim 13

A method for reducing the permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through said well and into said reservoir an aqueous liquid containing (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a cross-linking agent for the polymer selected from the group consisting of alkali metal or ammonium aluminates and gallates, (3) an amount of a water-soluble alkaline material selected from the group consisting of alkali metal and ammonium hydroxides, alkali metal silicates, alkali metal and ammonium carbonates, and alkali metal phosphates sufficient to raise the pH of the overall aqueous liquid to that at which the cross-linking material is substantially unreactive with the polymer, and (4) an amount of a water-soluble temperature-activated acidic material dissolved in the aqueous liquid sufficient to accelerate a cross-linking reaction between said polymer and said cross-linking agent when said liquid is subjected to an elevated temperature.

Claim 14

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir an aqueous liquid containing (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a crosslinking agent for the polymer comprising a water-soluble salt of a polyvalent cation reactive for cross-linking the polymer at an alkaline pH, with said cation being contained in an unreactive anionic species, (3) an amount of water-soluble alkaline material sufficient to raise the pH of the overall aqueous liquid to a value at which said polyvalent cation exists in an anionic species essentially unreactive to said polymer, and (4) an amount of a water-soluble temperature-activated acidic material dissolved in the aqueous liquid in an amount sufficient to accelerate the lowering of the pH of said liquid to a value at which said anionic species becomes a polyvalent cation reactive for crosslinking when said liquid is subjected to an elevated temperature.

Claim 15

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting through a well and into said reservoir an aqueous liquid containing (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a crosslinking agent for the polymer comprising a water-soluble salt of a polyvalent cation reactive for cross-linking the polymer at an alkaline pH, with said cation being contained in an unreactive anionic species, (3) an amount of water-soluble alkaline material sufficient to raise the pH of the overall aqueous liquid to a value at which said polyvalent cation exists in an anionic species essentially unreactive to said polymer, and (4) an amount of a water-soluble temperature-activated acidic material dissolved in the aqueous liquid in an amount sufficient to accelerate the lowering of the pH of said liquid to a value at which said anionic species becomes a polyvalent cation reactive for crosslinking when said liquid is subjected to an elevated temperature.

Claim 25

A method for reducing the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting an aqueous liquid containing (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, popolyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a crosslinking agent for the polymer comprising a water-soluble alkali metal aluminate reactive for cross-linking the polymer at an alkaline pH, (3) an amount of water-soluble alkaline material sufficient to raise the pH of the overall aqueous liquid to a value at which the crosslinking agent is substantially unreactive with the polymer, and (4) an amount of a water-soluble temperature-activated acidic material selected from the group consisting of polyethylene glycol esters, ethyl acetate esters, acrylate copolymers, and mixtures of dimethyl esters comprising dimethyl succinate, dimethyl glutarate, and dimethyl adipate dissolved in the aqueous liquid in an amount sufficient to accelerate the lowering of the pH of said liquid to a value at which said crosslinking agent becomes a polyvalent cation reactive for crosslinking when said liquid is subjected to an elevated temperature.

Claim 26

A method for reducing the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising injecting an aqueous liquid containing (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, popolyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a crosslinking agent for the polymer comprising a water-soluble alkali metal aluminate reactive for cross-linking the polymer at an alkaline pH, (3) an amount of water-soluble alkaline material sufficient to raise the pH of the overall aqueous liquid to a value at which the crosslinking agent is substantially unreactive with the polymer, and (4) an amount of a water-soluble temperature-activated acidic material selected from the group consisting of polyethylene glycol esters, ethyl acetate esters, acrylate copolymers, and mixtures of dimethyl esters comprising dimethyl succinate, dimethyl glutarate, and dimethyl adipate dissolved in the aqueous liquid in an amount sufficient to accelerate the lowering of the pH of said liquid to a value at which said crosslinking agent becomes a polyvalent cation reactive for crosslinking when said liquid is subjected to an elevated temperature.

Claim 27

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a cross-linking agent comprising a water-soluble aluminate; (3) an alkaline material provided in an amount sufficient to raise the pH of said aqueous liquid above 10.0 in the absence of the additive hereinafter described; and (4) an additive comprising a mixture of dimethyl adipate, dimethyl glutarate, and dimethyl succinate.

Claim 28

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir penetrated by at least one well comprising injecting through a well and into said reservoir a composition of matter comprising in an aqueous liquid (1) a water-soluble or water-dispersible polymer; (2) a cross-linking agent comprising a water-soluble aluminate; (3) an alkaline material provided in an amount sufficient to raise the pH of said aqueous liquid above 10.0 in the absence of the additive hereinafter described; and (4) an additive comprising a mixture of dimethyl adipate, dimethyl glutarate, and dimethyl succinate.

Claim 32

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising, in the first stage, injecting through a well and into said reservoir an aqueous liquid comprising (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid-acrylamide copolymers, polyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a cross-linking agent for the polymer selected from the group consisting of an alkali metal or ammonium aluminate, tungstate, or gallate, and (3) an amount of a water-soluble alkaline material selected from the group consisting of alkali metal and ammonium hydroxides, alkali metal silicates, alkali metal and ammonium carbonates, and alkali metal phosphates sufficient to raise the pH of the overall aqueous solution or dispersion above that at which cross-linking material is substantially unreactive with the polymer, passing the said aqueous liquid through the reservoir until the pH has fallen to that at which cross-linking occurs, in the second stage, injecting through a well and into said reservoir a mixture of said aqueous liquid in combination with a sufficient amount of a temperature-activated acidic material dissolved in the aqueous liquid to accelerate the rate at which cross-linking occurs when said aqueous solution reaches reservoir temperature, passing the said aqueous liquid in combination with said acidic material into the reservoir, and allowing gelation so as to reduce the reservoir permeability.

Claim 33

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising, in the first stage, injecting through a well and into said reservoir an aqueous liquid comprising (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid-acrylamide copolymers, polyalkyleneoxides, carboxyalkylcelluloses, carboxyalkylhydroxyethylcelluloses, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a cross-linking agent for the polymer selected from the group consisting of an alkali metal or ammonium aluminate, tungstate, or gallate, and (3) an amount of a water-soluble alkaline material selected from the group consisting of alkali metal and ammonium hydroxides, alkali metal silicates, alkali metal and ammonium carbonates, and alkali metal phosphates sufficient to raise the pH of the overall aqueous solution or dispersion above that at which cross-linking material is substantially unreactive with the polymer, passing the said aqueous liquid through the reservoir until the pH has fallen to that at which cross-linking occurs, in the second stage, injecting through a well and into said reservoir a mixture of said aqueous liquid in combination with a sufficient amount of a temperature-activated acidic material dissolved in the aqueous liquid to accelerate the rate at which cross-linking occurs when said aqueous solution reaches reservoir temperature, passing the said aqueous liquid in combination with said acidic material into the reservoir, and allowing gelation so as to reduce the reservoir permeability.

Claim 39

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising (A) injecting through a well and into said reservoir about 2 to 800 barrels per vertical foot of reservoir to be treated of a composition comprising an aqueous solution or dispersion of (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid-acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyethylhydroxyethylcellulose, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a cross-linking agent reactive for the polymer selected from the group consisting of an alkali metal or ammonium aluminates and gallates, (3) an amount of a water-soluble alkaline material selected from the group consisting of alkali metal and ammonium hydroxides, alkali metal silicates, alkali metal and ammonium carbonates, and alkali metal phosphates sufficient to raise the pH of the overall aqueous solution to a value at which said cross-linking agent is substantially unreactive to the polymer, and (4) a sufficient amount of a temperature-activated water-soluble acidic material dissolved in the aqueous liquid to lower the pH of the liquid to a value at which said cross-linking agent is substantially reactive with the polymer when the solution reaches the temperature of the reservoir, (B) passing said composition into the reservoir, and (C) allowing gelation so as to reduce the reservoir permeability.

Claim 40

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising (A) injecting through a well and into said reservoir about 2 to 800 barrels per vertical foot of reservoir to be treated of a composition comprising an aqueous solution or dispersion of (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid-acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyethylhydroxyethylcellulose, hydroxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a cross-linking agent reactive for the polymer selected from the group consisting of an alkali metal or ammonium aluminates and gallates, (3) an amount of a water-soluble alkaline material selected from the group consisting of alkali metal and ammonium hydroxides, alkali metal silicates, alkali metal and ammonium carbonates, and alkali metal phosphates sufficient to raise the pH of the overall aqueous solution to a value at which said cross-linking agent is substantially unreactive to the polymer, and (4) a sufficient amount of a temperature-activated water-soluble acidic material dissolved in the aqueous liquid to lower the pH of the liquid to a value at which said cross-linking agent is substantially reactive with the polymer when the solution reaches the temperature of the reservoir, (B) passing said composition into the reservoir, and (C) allowing gelation so as to reduce the reservoir permeability.

Claim 44

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising (A) injecting through a well and into said reservoir about 2 to 800 barrels per vertical foot of reservoir to be treated of a composition comprising an aqueous solution or dispersion of (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid-acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyethylhydroxyethylcellulose, hydrooxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a cross-linking agent reactive for the polymer selected from the group consisting of an alkali metal or ammonium aluminates, tungstates, and gallates, (3) an amount of a water-soluble alkaline material sufficient to raise the pH of the overall aqueous solution to a value at which said cross-linking agent is substantially unreactive to the polymer, and (4) a sufficient amount of an acidic material selected from the group consisting of polyethylene glycol esters, ethyl acetate esters, acrylate copolymers and a mixture of dimethyl adipate, dimethyl glutarate and dimethyl succinate dissolved in the aqueous liquid to lower the pH of the liquid to a valve at which said cross-linking agent is substantially reactive with the polymer when the solution reaches the temperature of the reservoir, (B) passing said composition into the reservoir, and (C) allowing gelation so as to reduce the reservoir permeability.

Claim 45

A method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well comprising (A) injecting through a well and into said reservoir about 2 to 800 barrels per vertical foot of reservoir to be treated of a composition comprising an aqueous solution or dispersion of (1) a water-soluble or water-dispersible polymer selected from the group consisting of acrylic acid-acrylamide copolymers, polyacrylamides, partially hydrolyzed polyacrylamides, polyalkyleneoxides, carboxyalkylcelluloses, carboxyethylhydroxyethylcellulose, hydrooxyethylcelluloses and heteropolysaccharides obtained by the fermentation of starch-derived sugar, (2) a cross-linking agent reactive for the polymer selected from the group consisting of an alkali metal or ammonium aluminates, tungstates, and gallates, (3) an amount of a water-soluble alkaline material sufficient to raise the pH of the overall aqueous solution to a value at which said cross-linking agent is substantially unreactive to the polymer, and (4) a sufficient amount of an acidic material selected from the group consisting of polyethylene glycol esters, ethyl acetate esters, acrylate copolymers and a mixture of dimethyl adipate, dimethyl glutarate and dimethyl succinate dissolved in the aqueous liquid to lower the pH of the liquid to a valve at which said cross-linking agent is substantially reactive with the polymer when the solution reaches the temperature of the reservoir, (B) passing said composition into the reservoir, and (C) allowing gelation so as to reduce the reservoir permeability.

Claim 47

The method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well, said reduction in permeability occurring at or nearby the well to about 20 feet from the well, comprising injecting through the well and into said reservoir an aqueous solution or dispersion comprising (1) about 0.0025 to 1 part by weight of a water-soluble or water-dispersible polyacrylamide or partially hydrolyzed polyacrylamide, (2) about 0.0005 to 1 part by weight of an alkali metal or ammonium aluminate cross-linking agent, and (3) an amount of sodium hydroxide or a sodium phosphate sufficient to raise the pH of the overall aqueous solution or dispersion to that at which the crosslinking agent is substantially unreactive with the polymer, and (4) an amount of a temperature activated acidic material comprising a mixture of dimethyl glutarate, dimethyl adipate and dimethyl succinate sufficient to lower the pH of the overall aqueous solution or dispersion at 150° F. to that at which a cross-linking reaction occurs.

Claim 48

The method for reducing the permeability of the higher permeability zones of a subterranean reservoir having heterogeneous permeability penetrated by at least one well, said reduction in permeability occurring at or nearby the well to about 20 feet from the well, comprising injecting through the well and into said reservoir an aqueous solution or dispersion comprising (1) about 0.0025 to 1 part by weight of a water-soluble or water-dispersible polyacrylamide or partially hydrolyzed polyacrylamide, (2) about 0.0005 to 1 part by weight of an alkali metal or ammonium aluminate cross-linking agent, and (3) an amount of sodium hydroxide or a sodium phosphate sufficient to raise the pH of the overall aqueous solution or dispersion to that at which the crosslinking agent is substantially unreactive with the polymer, and (4) an amount of a temperature activated acidic material comprising a mixture of dimethyl glutarate, dimethyl adipate and dimethyl succinate sufficient to lower the pH of the overall aqueous solution or dispersion at 150° F. to that at which a cross-linking reaction occurs.