Drilling fluid containing a copolymer filtration control agent

Claim 2

In a method of drilling a well into a subterranean formation in which an aqueous drilling fluid containing clayey material is circulated into the well, the steps of forming a filter cake on the wall of the well to decrease loss of fluid from the drilling fluid, which comprises: (1) admixing with said drilling fluid an amount of at least about 0.25 pounds per 42 gallon barrel of a copolymer of: (a) from between about 8 mole percent and about 70 mole percent of a (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof; and (b) from between about 30 mole percent and about 91 mole percent of a (meth) acrylamide or N-alkyl (meth) acrylamide, a 0.5% by weight aqueous solution of said copolymer having a viscosity of about 25° C. of from between about 18 centipoises and about 44 centipoises, as determined at a shear rate of 511 reciprocal seconds, the number of carbon atoms in the alkyl portion of the acrylamido-alkyl sulfonic acid or alkali metal salt thereof being about four, and the number of carbon atoms in the alkyl portion of the N-alkyl (meth) acrylamide being from between about 1 and about 3.

Claim 3

The method of claim 1 wherein the amount of said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is about 20 mole percent and the amount of said (meth) acrylamide or N-alkyl (meth) acrylamide is about 80 mole percent.

Claim 4

The method of claim 1 wherein said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is sodium 2-acrylamido-2-methyl propane sulfonate.

Claim 5

The method of claim 1 wherein said (meth) acrylamide is acrylamide.

Claim 6

The method of claim 1 wherein said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is sodium 2-acrylamido-2-methyl propane sulfonate in an amount of about 20 mole percent and said (meth) acrylamide is acrylamide in an amount of about 80 mole percent.

Claim 7

In a method of drilling a well into a subterranean formation in which an aqueous drilling fluid containing clayey material is circulated into the well, the steps of forming a filter cake on the wall of the well to decrease loss of fluid from the drilling fluid, which comprises: (1) admixing with said drilling fluid an amount of at least about 0.25 pounds per 42 gallon barrel of a cross-linked copolymer of: (a) from between about 8 mole percent and about 70 mole percent of a (meth) acrylamide alkyl sulfonic acid or alkali metal salt thereof; (b) from between about 30 mole percent and about 91 mole percent of a (meth) acrylamide or N-alkyl (meth) acrylamide; and (c) from between about 0.2 mole percent and about 4.4 mole percent of a quaternary ammonium salt selected from the class consisting of 3-methacryloyloxy-2-hydroxy propyl trimethyl ammonium chloride, 3-acrylamide-3-methylbutyl trimethyl ammonium chloride, diallyl dimethyl ammonium chloride, N-methyl 2-vinyl pyridinium methyl sulfate, N-methyl 4-vinyl pyridinium methyl sulfate, N-propyl acrylamide trimethyl ammonium chloride, and 2-methacryloyloxyethyl trimethyl ammonium methoxulfate, a 0.5% by weight aqueous solution of said copolymer having a viscosity at about 25° C. between about 18 centipoises and about 44 centipoises, as determined at a shear rate of 511 reciprocal seconds, the number of carbon atoms in the alkyl portion of the acrylamido-alkyl sulfonic acid or alkali metal salt thereof being about four, and the number of carbon atoms in the alkyl portion of the N-alkyl (meth) acrylamide being between from about 1 and about 3; and (2) circulating said drilling fluid in said well.

Claim 8

In a method of drilling a well into a subterranean formation in which an aqueous drilling fluid containing clayey material is circulated into the well, the steps of forming a filter cake on the wall of the well to decrease loss of fluid from the drilling fluid, which comprises: (1) admixing with said drilling fluid an amount of at least about 0.25 pounds per 42 gallon barrel of a cross-linked copolymer of: (a) from between about 8 mole percent and about 70 mole percent of a (meth) acrylamide alkyl sulfonic acid or alkali metal salt thereof; (b) from between about 30 mole percent and about 91 mole percent of a (meth) acrylamide or N-alkyl (meth) acrylamide; and (c) from between about 0.2 mole percent and about 4.4 mole percent of a quaternary ammonium salt selected from the class consisting of 3-methacryloyloxy-2-hydroxy propyl trimethyl ammonium chloride, 3-acrylamide-3-methylbutyl trimethyl ammonium chloride, diallyl dimethyl ammonium chloride, N-methyl 2-vinyl pyridinium methyl sulfate, N-methyl 4-vinyl pyridinium methyl sulfate, N-propyl acrylamide trimethyl ammonium chloride, and 2-methacryloyloxyethyl trimethyl ammonium methoxulfate, a 0.5% by weight aqueous solution of said copolymer having a viscosity at about 25° C. between about 18 centipoises and about 44 centipoises, as determined at a shear rate of 511 reciprocal seconds, the number of carbon atoms in the alkyl portion of the acrylamido-alkyl sulfonic acid or alkali metal salt thereof being about four, and the number of carbon atoms in the alkyl portion of the N-alkyl (meth) acrylamide being between from about 1 and about 3; and (2) circulating said drilling fluid in said well.

Claim 9

The method of claim 6 wherein the amount of said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is about 9.8 mole percent; the amount of said (meth) acrylamide or N-alkyl (meth) acrylamide is about 90 mole percent; and the amount of said quaternary ammonium salt is about 0.2 mole percent.

Claim 10

The method of claim 6 wherein said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is sodium 2-acrylamido-2-methyl propane sulfonate.

Claim 11

The method of claim 6 wherein said (meth) acrylamide is acrylamide.

Claim 12

The method of claim 6 wherein said quaternary ammonium salt is a (meth) acryloyloxy alkyl trimethyl ammonium salt.

Claim 13

The method of claim 6 wherein said quaternary ammonium salt is 2-methacryloyloxy-ethyl trimethyl ammonium methosulfate.

Claim 14

The method of claim 6 wherein said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is sodium 2-acrylamido-2-methyl propane sulfonate in an amount of about 9.8 mole percent; said (meth) acrylamide is acrylamide in an amount of about 90 mole percent; and said quaternary ammonium salt is 2-methylacryloyloxy-ethyl trimethyl ammonium methosulfate in an amount of about 0.2 mole percent.

Claim 15

An aqueous drilling fluid comprising water, a clayey substance suspended in said water, and at least about 0.25 pounds per 42 gallon barrel of a copolymer of: (a) from between about 8 mole percent and about 70 mole percent of a (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof; and (b) from between about 30 mole percent and about 91 mole percent of a (meth) acrylamide or N-alkyl (meth) acrylamide, a 0.5% by weight aqueous solution of said copolymer having a viscosity of about 25° C. of from between about 18 centipoises and about 44 centipoises, as determined at a shear rate of 511 reciprocal seconds, the number of carbon atoms in the alkyl portion of the acrylamidoalkyl sulfonic acid or alkali metal salt thereof being about four, and the number of carbon atoms in the alkyl portion of the N-alkyl (meth) acrylamide being from between about 1 and about 3.

Claim 16

An aqueous drilling fluid comprising water, a clayey substance suspended in said water, and at least about 0.25 pounds per 42 gallon barrel of a copolymer of: (a) from between about 8 mole percent and about 70 mole percent of a (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof; and (b) from between about 30 mole percent and about 91 mole percent of a (meth) acrylamide or N-alkyl (meth) acrylamide, a 0.5% by weight aqueous solution of said copolymer having a viscosity of about 25° C. of from between about 18 centipoises and about 44 centipoises, as determined at a shear rate of 511 reciprocal seconds, the number of carbon atoms in the alkyl portion of the acrylamidoalkyl sulfonic acid or alkali metal salt thereof being about four, and the number of carbon atoms in the alkyl portion of the N-alkyl (meth) acrylamide being from between about 1 and about 3.

Claim 17

The drilling fluid of claim 13 wherein the amount of said (meth) acrylamide or N-alkyl (meth) acrylamide is about 80 mole percent.

Claim 18

The drilling fluid of claim 13 wherein the amount of said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is about 20 mole percent and the amount of said (meth) acrylamide or N-alkyl (meth) acrylamide is about 80 mole percent.

Claim 19

The drilling fluid of claim 13 wherein said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is sodium 2-acrylamido-2-methyl propane sulfonate.

Claim 20

The drilling fluid of claim 13 wherein said (meth) acrylamide is acrylamide.

Claim 21

The drilling fluid of claim 13 wherein said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is sodium 2-acrylamido-2-methyl propane sulfonate in an amount of about 20 mole percent and said (meth) acrylamide is acrylamide in an amount of about 80 mole percent.

Claim 22

An aqueous drilling fluid comprising water, a clayey substance suspended in said water, and at least about 0.25 pounds per 42 gallon barrel of a cross-linked copolymer of: (a) from between about 8 mole percent and about 70 mole percent of a (meth) acrylamide alkyl sulfonic acid or alkali metal salt thereof; (b) from between about 30 mole percent and about 91 mole percent of a (meth) acrylamide or N-alkyl (meth) acrylamide; and (c) from between about 0.2 mole percent and about 4.4 mole percent of a quaternary ammonium salt selected from the class consisting of 3-methacryloyloxy-2-hydroxy propyl trimethyl ammonium chloride, 3-acrylamido-3-methylbutyl trimethyl ammonium chloride, diallyl dimethyl ammonium chloride, N-methyl 2-vinyl pyridinium methyl sulfate, N-methyl 4-vinyl pyridinium methyl sulfate, N-propyl acrylamido trimethyl ammonium chloride, and 2-methacryloyloxyethyl trimethyl ammonium methosulfate, a 0.5% by weight aqueous solution of said copolymer having a viscosity at about 25° C. of from between about 18 centipoises and about 44 centipoises, as determined at a shear rate of 511 reciprocal seconds, the number of carbon atoms in the alkyl portion of the acrylamidoalkyl sulfonic acid or alkali metal salt thereof being about four, and the number of carbon atoms in the alkyl portion of the N-alkyl (meth) acrylamide being from between about 1 and about 3.

Claim 23

An aqueous drilling fluid comprising water, a clayey substance suspended in said water, and at least about 0.25 pounds per 42 gallon barrel of a cross-linked copolymer of: (a) from between about 8 mole percent and about 70 mole percent of a (meth) acrylamide alkyl sulfonic acid or alkali metal salt thereof; (b) from between about 30 mole percent and about 91 mole percent of a (meth) acrylamide or N-alkyl (meth) acrylamide; and (c) from between about 0.2 mole percent and about 4.4 mole percent of a quaternary ammonium salt selected from the class consisting of 3-methacryloyloxy-2-hydroxy propyl trimethyl ammonium chloride, 3-acrylamido-3-methylbutyl trimethyl ammonium chloride, diallyl dimethyl ammonium chloride, N-methyl 2-vinyl pyridinium methyl sulfate, N-methyl 4-vinyl pyridinium methyl sulfate, N-propyl acrylamido trimethyl ammonium chloride, and 2-methacryloyloxyethyl trimethyl ammonium methosulfate, a 0.5% by weight aqueous solution of said copolymer having a viscosity at about 25° C. of from between about 18 centipoises and about 44 centipoises, as determined at a shear rate of 511 reciprocal seconds, the number of carbon atoms in the alkyl portion of the acrylamidoalkyl sulfonic acid or alkali metal salt thereof being about four, and the number of carbon atoms in the alkyl portion of the N-alkyl (meth) acrylamide being from between about 1 and about 3.

Claim 24

The drilling fluid of claim 19 wherein the amount of said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is about 9.8 mole percent; the amount of said (meth) acrylamide or N-alkyl (meth) acrylamide is about 90 mole percent; and the amount of said quaternary ammonium salt is about 0.2 mole percent.

Claim 25

The drilling fluid of claim 19 wherein said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is soidum 2-acrylamido-2-methyl propane sulfonate.

Claim 26

The drilling fluid of claim 19 wherein said (meth) acrylamide is acrylamide.

Claim 27

The drilling fluid of claim 19 wherein said quaternary ammonium salt is a (meth) acryloyloxy alkyl trimethyl ammonium salt.

Claim 28

The drilling fluid of claim 19 wherein said quaternary ammonium salt is 2-methacryloyloxy-ethyl trimethyl ammonium methosulfate.

Claim 29

The drilling fluid of claim 19 wherein said (meth) acrylamido alkyl sulfonic acid or alkali metal salt thereof is sodium 2-acrylamido-2-methyl propane sulfonate in an amount of about 9.8 mole percent; said (meth) acrylamide is acrylamide in an amount of about 90 mole percent; and said quaternary ammonium salt is 2-methacryloyloxy-ethyl trimethyl ammonium methosulfate in an amount of about 0.2 mole percent.