Methods of using gelled polymers in the treatment of wells

Claim 2

A method according to claim 1 wherein said aqueous gel comprises water to which there has been added: from 0.0025 to 5 weight percent of said polymer, based upon the weight of said water; from 0.05 to 60 weight percent of said polyvalent metal compound based upon the weight of said polymer; and from 0.1 to at least about 200 percent of the stoichiometric amount of said reducing agent required to reduce said polyvalent metal to said lower polyvalent valence state.

Claim 3

A method according to claim 3 wherein said polymer is a substantially linear polymer of acrylamide.

Claim 4

A method according to claim 4 wherein said compound of a polyvalent metal is a compound of chromium wherein the valence of the chromium is +6 and the valence of at least a portion of said chromium is reduced to +3.

Claim 5

A method according to claim 5 wherein said chromium compound is selected from the group consisting of ammonium chromate, ammonium dichromate, the alkali metal chromates and dichromates, chromium trioxide, and mixtures thereof.

Claim 6

A method according to claim 6 wherein said reducing agent is selected from the group consisting of hydroquinone, sodium sulfide, sodium hydrosulfite, sodium metabisulfite, potassium sulfite, sodium bisulfite, potassium metabisulfite, sodium sulfite, sodium thiosulfate, ferrous sulfate, hydrogen sulfide, ferrous chloride, p-hydrazinobenzoic acid, hydrazine phosphite, hydrazine dihydrochloride, and mixtures thereof.

Claim 7

A method according to claim 3 wherein: said polymer is a substantially linear polyacrylamide; said polyvalent metal compound is sodium dichromate; and said reducing agent is sodium hydrosulfite.

Claim 8

A method according to claim 1 wherein: said borehole comprises an injection well; said formation comprises an oil-bearing formation and is also penetrated by a production well; said method is a fluid drive process carried out for the recovery of oil from said formation by injecting a drive fluid into the pores of said formation via said injection well and driving oil to said production well; and said fluid medium comprising said aqueous gel is introduced into said injection well and into the pores of said formation.

Claim 9

A method according to claim 9 wherein: said fluid medium is injected into said formation prior to injecting a drive fluid into said formation via said injection well in said fluid drive process for driving said oil to said production well.

Claim 10

A method according to claim 10 wherein said aqueous gel comprises water to which there has been added: from 0.025 to 0.4 weight percent of said polymer, based upon the weight of said water; from 0.5 to 30 weight percent of said polyvalent metal compound based upon the weight of said polymer; and from 0.5 to at least about 150 percent of the stoichiometric amount of said reducing agent required to reduce said polyvalent metal to said lower polyvalent valence state.

Claim 11

A method according to claim 11 wherein: said polymer is a substantially linear polyacrylamide; said polyvalent metal compound is sodium dichromate; and said reducing agent is sodium hydrosulfite.

Claim 12

A method according to claim 9 wherein: said fluid medium is injected into said formation subsequent to having injected a drive fluid into said formation via said injection well in said fluid drive process for driving said oil to said production well.

Claim 13

A method according to claim 13 wherein said aqueous gel comprises water to which there has been added: from 0.025 to 0.4 weight percent of said polymer, based upon the weight of said water; from 0.5 to 30 weight percent of said polyvalent metal compound based upon the weight of said polymer; and from 0.5 to at least about 150 percent of the stoichiometric amount of said reducing agent required to reduce said polyvalent metal to said lower polyvalent valence state.

Claim 14

A method according to claim 14 wherein: said polymer is a substantially linear polyacrylamide; said polyvalent metal compound is sodium dichromate; and said reducing agent is sodium hydrosulfite.

Claim 15

A method according to claim 26 wherein said compound of a polyvalent metal is a compound of chromium wherein the valence of the chromium is +6 and the valence of at least a portion of said chromium is reduced to +3.

Claim 16

A method according to claim 16 wherein said chromium compound is selected from the group consisting of ammonium chromate, ammonium dichromate, the alkali metal chromates and dichromates, chromium trioxide, and mixtures thereof.

Claim 17

A method according to claim 17 wherein said reducing agent is selected from the group consisting of hydroquinone, sodium sulfide, sodium hydrosulfite, sodium metabisulfite, potassium sulfite, sodium bisulfite, potassium metabisulfite, sodium sulfite, sodium thiosulfate, ferrous sulfate, hydrogen sulfide, ferrous chloride, p-hydrazinobenzoic acid, hydrazine phosphite, hydrazine dihydrochloride, and mixtures thereof.

Claim 18

A method according to claim 1 wherein: said method comprises a method for drilling a said borehole into the earth; a drill bit is actuated in said borehole in contact with said formation and penetrates same in the presenCe of said fluid medium; and said fluid medium, together with formation solids entrained therein, is removed from said borehole.

Claim 19

A method according to claim 15 wherein said aqueous gel comprises water to which there has been added: from 0.0025 to 5 weight percent of said polymer, based upon the weight of said water; from 0.05 to 60 weight percent of said polyvalent metal compound based upon the weight of said polymer; and from 0.1 to at least about 200 percent of the stoichiometric amount of said reducing agent required to reduce said polyvalent metal to said lower polyvalent valence state.

Claim 20

A method according to claim 20 wherein: said polymer is a substantially linear polyacrylamide; said polyvalent metal compound is sodium dichromate; and said reducing agent is sodium hydrosulfite.

Claim 21

A method according to claim 19 wherein said aqueous gel comprises water to which there has been added: from 0.01 to 1.5 weight percent of said polymer, based upon the weight of said water; from 0.05 to 60 weight percent of said polyvalent metal compound based upon the weight of said polymer; and from 0.1 to at least about 200 percent of the stoichiometric amount of said reducing agent required to reduce said polyvalent metal to said lower polyvalent valence state; and wherein said polymer is a substantially linear polymer of acrylamide and from 0.1 to about 12 percent of the carboxamide groups in said polymer are hydrolyzed to carboxyl groups.

Claim 22

A method according to claim 22 wherein: said polyvalent metal compound is a chromium compound wherein the valence of the chromium is +6 and the valence of at least a portion of said chromium is reduced to +3; and said reducing agent is selected from the group consisting of hydroquinone, sodium sulfide, sodium hydrosulfite, sodium metabisulfite, potassium sulfite, sodium bisulfite, potassium metabisulfite, sodium sulfite, sodium thiosulfate, ferrous sulfate, hydrogen sulfide, ferrous chloride, p-hydrazinobenzoic acid, hydrazine phosphite, hydrazine dihydrochloride, and mixtures thereof.

Claim 23

A method according to claim 1 wherein: said borehole comprises a producing well; said method comprises a method for recovering hydrocarbons from said formation via said borehole, and for reducing the concomitant production of water from said formation; and said fluid medium comprising said aqueous gel is introduced into said well and into the pores of said formation.

Claim 24

A method according to claim 1 wherein from 0.1 to about 12 percent of the carboxamide groups in said polymer are hydrolyzed to carboxyl groups.

Claim 25

A method according to claim 9 wherein said aqueous gel comprises water to which there has been added: from 0.01 to 1.5 weight percent of said polymer, based upon the weight of said water; from 0.05 to 60 weight percent of said polyvalent metal compound based upon the weight of said polymer; and from 0.1 to at least about 200 percent of the stoichiometric amount of said reducing agent required to reduce said polyvalent metal to said lower polyvalent valence state; and wherein said polymer is a substantially linear polymer of acrylamide and from 0.1 to about 12 percent of the carboxamide groups in said polymer are hydrolyzed to carboxyl groups.