Compositions with polyaziridine crosslinkers for treating subterranean formations

1. A method of treating a subterranean formation comprising:

i) providing to a subterranean formation a composition comprising:

a maleic anhydride copolymer comprising:

repeat units I and II:

wherein each R 1 is independently selected from the group consisting of —H, —O—C 1-5 alkyl, and —C 1-5 alkyl, and each R 2 is independently selected from the group consisting of —H, —O—C 1-5 alkyl, and —C 1-5 alkyl; and

at least one hydrolyzed repeat unit selected from repeat units III and IV:

wherein each R 5 is independently selected from —OH and NH 2 , provided that at least one of R 5 is NH 2 ,

or a salt thereof; and

a polyaziridine crosslinker comprising at least two aziridine moieties, or a salt thereof; and

ii) crosslinking the maleic anhydride copolymer, or a salt thereof, and the polyaziridine crosslinker, or a salt thereof, to form a sealant.

2. The method of claim 1 , wherein the salt of the maleic anhydride copolymer is an ammonium salt, an alkali metal salt, or an alkali earth metal salt.

3. The method of claim 1 , wherein:

each R 1 is H, and each R 2 is independently selected from the group consisting of —H, —OCH 3 , and —CH 3 ; or

each R 2 is H, and each R 1 is independently selected from the group consisting of —H, —OCH 3 , and —CH 3 .

4. The method of claim 1 , wherein the repeat unit I has formula:

5. The method of claim 1 , wherein the polyaziridine crosslinker has formula:

or a salt thereof, wherein:

L 1 and L 2 at each occurrence are each independently selected from the group consisting of —C 1-6 alkylene-, —C 1-6 alkenylene-, —C 1-6 alkynylene-, —(O—C 1-4 alkylene) p -, —(C 1-4 alkylene-O—) p —, —O—, —S—, NH—, and —C(═O)—, wherein said —C 1-6 alkylene-, —C 1-6 alkenylene-, —C 1-6 alkynylene-, and —C 1-4 alkylene- are each optionally substituted with 1, 2, or 3 substituents independently selected from the group consisting of -halo, —CN, —OH, —C 1-3 alkyl, —C 1-3 alkoxy, —C 1-3 haloalkyl, —C 1-3 haloalkoxy, -amino, —C 1-3 alkylamino, and -di(C 1-3 alkyl)amino;

each R 3 is selected form the group consisting of —H, —C 1-6 alkyl, —C 1-6 alkenyl, —C 1-6 alkynyl, -halo, —CN, —OH, —C 1-3 alkoxy, —C 1-3 haloalkyl, —C 1-3 haloalkoxy, -amino, —C 1-3 alkylamino, -di(C 1-3 alkyl)amino, —(O—C 1-4 alkylene) p -H, and —(C 1-4 alkylene-O—) p —C 1-6 alkyl;

each R 4 is selected from the group consisting of:

wherein each of (a) and (b) is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, CN, OH, amino, C 1-3 alkylamino, di(C 1-3 alkyl)amino, —C 1-3 alkyl, C 1-3 alkoxy, C 1-3 haloalkyl, and C 1-3 haloalkoxy;

p at each occurrence is independently an integer from 0 to 40;

x and y at each occurrence are each independently an integer from 0 to 10;

m is an integer from 2 to 4; and

n is an integer from 0 to 4;

provided that a sum of m and n is 4.

6. The method of claim 5 , wherein:

m is 3 and n is 1;

x is 1 and L 1 is selected form the group consisting of —C 1-6 alkylene-, —C 1-6 alkenylene-, —(O—C 1-3 alkylene) p -, and —(C 1-3 alkylene-O—) p —;

each p is an integer form 1 to 20;

R 3 is selected form the group consisting of H, —C 1-3 alkyl, —OH, —C 1-3 alkoxy, —C 1-3 haloalkyl, —C 1-3 haloalkoxy, —(O—C 1-3 alkylene) p -H, and (C 1-3 alkylene-O—) p —C 1-3 alkyl;

each y is an integer from 0 to 5, and each L 2 is independently selected from C 1-4 alkylene-, —O—, NH—, and —C(═O)—; and

each R 4 is selected from the group consisting of:

wherein each of (a) and (b) is optionally substituted with 1 or 2 substituents independently selected from the group consisting of —C 1-3 alkyl, C 1-3 alkoxy, C 1-3 haloalkyl, and C 1-3 haloalkoxy.

7. The method of claim 6 , wherein the polyaziridine crosslinker is a compound PZ-33 of formula:

or a salt thereof.

8. The method of claim 1 , wherein an amount of the polyaziridine crosslinker in the composition is in a range of about 0.1 wt. % to about 20 wt. % relative to an amount of the maleic anhydride copolymer.

9. The method of claim 1 , wherein pH of the composition is in a range of about 5 to about 9.

10. The method of claim 1 , wherein viscosity of the composition is from about 80 cP to about 120 cP.

11. The method of claim 1 , wherein a combined amount of the maleic anhydride copolymer and the polyaziridine crosslinker in the composition is in a range of about 10 wt. % to about 30 wt. % relative to a weight of the composition.

12. The method of claim 1 , wherein the composition comprises an amine crosslinker.

13. The method of claim 12 , wherein the amine crosslinker is selected from the group consisting of a polyamine, a polyethyleneimine, and a combination thereof.

14. The method of claim 12 , wherein the amine crosslinker is tetraethylenepentamine (TEPA).

15. The method of claim 1 , wherein the composition has gel time of less than about 1.5 hours at about 70° F.

16. The method of claim 1 , wherein the composition has gel time of less than about 3 hours at about 40° F.

17. The method of claim 1 , wherein forming the sealant occurs near a casing, a casing-casing annulus, a tubing-casing annulus, or a casing-formation annulus.

18. The method of claim 1 , wherein the sealant is a gel plug.

19. The method of claim 1 , wherein the crosslinking of the composition occurs in contact with a set cement.

20. The method of claim 1 , wherein the subterranean formation comprises a wellbore comprising a cement sheath.

21. The method of claim 20 , wherein forming the sealant occurs in at least one of: a fracture in the cement sheath and a microannulus.

22. The method of claim 20 , wherein forming the sealant prevents or retards undesired loss or flow of a wellbore fluid into the subterranean formation or of a formation fluid into the wellbore.

23. The method of claim 20 , wherein the maleic anhydride copolymer, or a salt thereof, and the polyaziridine crosslinker, or a salt thereof, remain in an uncrosslinked state until placement in an appropriate location in the wellbore.

24. The method of claim 20 , wherein the providing comprises top-down squeezing the composition down an annulus.

25. The method of claim 20 , wherein the providing comprises injecting the composition downhole.

26. The method of claim 1 , wherein forming the sealant comprises a conformance control, a wellbore plug and abandonment, or thermal wellbore isolation gel system.

27. A composition for treating a subterranean formation, the composition comprising:

a maleic anhydride copolymer comprising:

repeat units I and II:

wherein each R 1 is independently selected from the group consisting of —H, —O—C 1-5 alkyl, and —C 1-5 alkyl, and each R 2 is independently selected from the group consisting of —O—C 1-5 alkyl, and —C 1-5 alkyl; and

at least one hydrolyzed repeat unit selected from repeat units III and IV:

wherein each R 5 is independently selected from —OH and NH 2 , or a salt thereof;

a polyaziridine crosslinker comprising at least two aziridine moieties, or a salt thereof; and

a gel time control agent.

28. The composition of claim 27 , comprising an aqueous carrier solvent.

29. The composition of claim 27 , wherein the gel time control agent accelerates or retards formation of the gel from the maleic anhydride copolymer and the polyaziridine crosslinker in the absence of a set cement.

30. The composition of claim 27 , wherein the gel time control agent is selected form the group consisting of citric acid, trisodium phosphate, and a combination thereof.