Mobility control polymers for enhanced oil recovery

1. A water-soluble cross-linked polymer comprising about 1 mol % to about 99 mol % acrylamide monomers and about 1 mol % to about 99 mol % acrylic acid monomers or a salt thereof, and further comprising about 0.1 ppm to about 1000 ppm hydrolyzable cross-linked monomer units based on the weight of the water-soluble polymer, wherein the hydrolyzable cross-linked monomer units are covalently cross-linked and the covalently cross-linked monomer units have the structure of formula (IIb):

wherein:

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

2. The water-soluble polymer of claim 1 , wherein the water-soluble polymer comprises about 0.1 ppm to about 500 ppm covalently cross-linked monomer units.

3. The water-soluble polymer of claim 2 , wherein the polymer comprises about 20 mol % to about 80 mol % acrylamide monomers and about 10 mol % to about 60 mol % acrylic acid monomers or a salt thereof.

4. The water-soluble polymer of claim 2 , wherein the polymer comprises about 60 mol % to about 80 mol % acrylamide monomers and about 20 mol % to about 40 mol % acrylic acid monomers or a salt thereof.

5. The water-soluble polymer of claim 4 , wherein each R is independently selected from the group consisting of —H and —CH 3 .

6. The water-soluble polymer of claim 4 , wherein each R is —H.

7. The water-soluble polymer of claim 1 , wherein the water-soluble polymer comprises about 0.1 ppm to about 100 ppm covalently cross-linked monomer units.

8. The water-soluble polymer of claim 7 , wherein the polymer comprises about 20 mol % to about 80 mol % acrylamide monomers and about 10 mol % to about 60 mol % acrylic acid monomers or a salt thereof.

9. The water-soluble polymer of claim 7 , wherein the polymer comprises about 60 mol % to about 80 mol % acrylamide monomers and about 20 mol % to about 40 mol % acrylic acid monomers or a salt thereof.

10. The water-soluble polymer of claim 9 , wherein each R is independently selected from the group consisting of —H and —CH 3 .

11. The water-soluble polymer of claim 9 , wherein each R is —H.

12. A method for recovering a hydrocarbon fluid from a subterranean formation, comprising: injecting into the formation an aqueous flooding fluid comprising water and the water-soluble cross-linked polymer of claim 1 , 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.

13. The method of claim 12 , wherein the water-soluble polymer comprises about 0.1 ppm to about 500 ppm covalently cross-linked monomer units.

14. The method of claim 13 , wherein the polymer comprises about 60 mol % to about 80 mol % acrylamide monomers, about 20 mol % to about 40 mol % acrylic acid monomers or a salt thereof.

15. The method of claim 14 , wherein each R is —H.

16. The method of claim 12 , wherein the water-soluble polymer comprises about 0.1 ppm to about 100 ppm covalently cross-linked monomer units.

17. The method of claim 16 , wherein the polymer comprises about 60 mol % to about 80 mol % acrylamide monomers, about 20 mol % to about 40 mol % acrylic acid monomers or a salt thereof.

18. The method of claim 17 , wherein each R is —H.

19. The method of claim 12 , wherein the aqueous flooding fluid further comprises a surfactant, a biocide, an antioxidant, or a combination thereof.

20. The method of claim 12 , wherein the aqueous flooding fluid comprises about 100 ppm to about 10000 ppm of the water-soluble polymer.