Enhanced oil recovery using mobility control crosslinked polymers

1. A method for recovering a hydrocarbon fluid from a subterranean formation, comprising:

injecting into the formation an aqueous flooding fluid, the aqueous flooding fluid comprising water and a cross-linked water-soluble polymer having hydrolyzable cross-linked monomer units, the polymer comprising about 1 mol % to 100 mol % acrylamide monomers and at least one anionic monomer unit derived from a monomer selected from the group consisting of an acrylic acid salt, a methacrylic acid salt, a 2-acrylamido-2-methylpropane sulfonic acid salt and a styrene sulfonic acid salt, wherein, after injecting the aqueous flooding fluid into the formation, the hydrolyzable cross-linked monomer units are hydrolyzed to produce an un-crosslinked water-soluble polymer in the aqueous flooding fluid, wherein after hydrolysis of the hydrolyzable cross-linked monomer units, the aqueous flooding fluid has a viscosity that is higher than a viscosity of the aqueous fluid prior to injection into the formation and the un-crosslinked water-soluble polymer moves throughout the formation without blocking pores of the formation, thereby providing mobility control of the hydrocarbon fluid in the formation, wherein the hydrolyzable cross-linked monomer units are ionically cross-linked via an ionic interaction between two monomer units.

2. The method of claim 1 , wherein the water-soluble polymer comprises from about 1 mol % to about 25 mol % ionically cross-linked monomer units.

3. The method of claim 1 , wherein the water-soluble polymer comprises at least one monomer unit having the following formula (I):

wherein:

R is selected from the group consisting of H, C 1 -C 24 alkyl, C 2 -C 24 alkenyl and C 2 -C 24 alkynyl;

each R a is independently selected from the group consisting of H, unsubstituted or substituted C 1 -C 50 alkyl, unsubstituted or substituted C 2 -C 50 alkenyl, unsubstituted or substituted C 2 -C 50 alkynyl and unsubstituted or substituted aryl;

A is selected from the group consisting of O and NR b ;

R b is selected from the group consisting of —H, unsubstituted or substituted C 1 -C 24 alkyl, unsubstituted or substituted C 2 -C 24 alkenyl and unsubstituted or substituted C 2 -C 24 alkynyl;

B is selected from the group consisting of unsubstituted or substituted C 2 -C 24 alkylenyl, unsubstituted or substituted C 2 -C 24 alkenylenyl, unsubstituted or substituted C 2 -C 24 alkynylenyl and unsubstituted or substituted C 2 -C 24 heteroalkylenyl;

Z ⊖ is an anion; and

each represents a point of attachment to the polymer backbone.

4. The method of claim 3 , wherein the monomer unit of formula (I) is derived from a monomer selected from the group consisting of N,N-dimethylaminoethyl acrylate methyl chloride quaternary salt, N,N-dimethylaminoethyl methacrylate methyl chloride quaternary salt, N,N-dimethylaminopropyl acrylamide methyl chloride quaternary salt, and N,N-dimethylaminopropyl methacrylamide methyl chloride quaternary salt.

5. A method for recovering a hydrocarbon fluid from a subterranean formation, comprising:

injecting into the formation an aqueous flooding fluid comprising water and a cross-linked water-soluble polymer having hydrolyzable cross-linked monomer units, the polymer comprising about 1 mol % to 100 mol % acrylamide monomers and at least one anionic monomer unit derived from a monomer selected from the group consisting of an acrylic acid salt, a methacrylic acid salt, a 2-acrylamido-2-methylpropane sulfonic acid salt and a styrene sulfonic acid salt, wherein, after injecting the aqueous flooding fluid into the formation, the hydrolyzable cross-linked monomer units are hydrolyzed to produce an un-crosslinked water-soluble polymer in the aqueous flooding fluid after hydrolysis of the hydrolyzable cross-linked monomer units, the aqueous flooding fluid has a viscosity that is higher than a viscosity of the aqueous fluid prior to injection into the formation and the un-crosslinked water-soluble polymer moves throughout the formation without blocking pores of the formation, thereby providing mobility control of the hydrocarbon fluid in the formation, wherein the cross-linked monomer units are covalently cross-linked and have the following formula (II):

wherein:

each X is selected from the group consisting of O and NR b ;

each R b is independently selected from the group consisting of —H, unsubstituted or substituted C 1 -C 24 alkyl, unsubstituted or substituted C 2 -C 24 alkenyl and unsubstituted or substituted C 2 -C 24 alkynyl;

each R is independently selected from the group consisting of —H, unsubstituted or substituted C 1 -C 24 alkyl, unsubstituted or substituted C 2 -C 24 alkenyl and unsubstituted or substituted C 2 -C 24 alkynyl;

Y is selected from a group consisting of a bond and a linker comprising 1 to about 1000 member atoms; and

each represents a point of attachment to a first polymer backbone, and each represents a point of attachment to the first polymer backbone or to a second polymer backbone.

6. The method of claim 5 , wherein the covalently cross-linked monomer units have the following formula (IIa):

wherein:

each R is independently selected from the group consisting of —H and —CH 3 ;

Z is selected from the group consisting of a bond and a C 1 -C 12 alkylenyl group; and

each represents a point of attachment to a first polymer backbone, and each represents a point of attachment to the first polymer backbone or to a second polymer backbone.

7. The method of claim 6 , wherein the covalently cross-linked monomer units have the following formula (IIb):

8. The method of claim 7 , wherein the water-soluble polymer comprises about 0.1 ppm to about 20,000 ppm covalently cross-linked monomer units.

9. The method of claim 7 , wherein the water-soluble polymer comprises about 0.1 ppm to about 100 ppm covalently cross-linked monomer units.

10. The method of claim 7 , wherein the aqueous flooding fluid comprises about 100 ppm to about 10,000 ppm of the water-soluble polymer.

11. The method of claim 7 , wherein the aqueous flooding fluid further comprises a surfactant, a biocide, an antioxidant, or a combination thereof.

12. The method of claim 7 , wherein prior to injection, the aqueous flooding fluid has a viscosity of 0 cPs to about 100 cPs.

13. The method of claim 7 , wherein after injection, the aqueous flooding fluid has a viscosity of about 1 cPs to about 5,000 cPs.

14. The method of claim 7 , further comprising displacing the hydrocarbon fluid in the formation into one or more production vessels.

15. The method of claim 7 wherein the aqueous flooding fluid before injection has a viscosity of 0 cPs to about 100 cPs, and after introducing the aqueous flooding fluid into the formation, the viscosity of the aqueous flooding fluid increases to about 1 cPs to about 5,000 cPs.

16. The method of claim 15 , wherein the aqueous flooding fluid further comprises a surfactant, a biocide, an antioxidant, or a combination thereof.

17. The method of claim 15 , further comprising displacing the hydrocarbon fluid in the formation into one or more production vessels.

18. The method of claim 5 , wherein after hydrolysis of cross-linked monomer units, the water-soluble polymer is a linear polymer.