Biodegradable chelant compositions for fracturing fluid

1. A biodegradable additive composition comprising:

a) water;

b) at least two of the chelants selected from the group consisting of:

sodium polyaspartate;

sodium iminodisuccinate;

disodium hydroxyethyleneiminodiacetate (Na 2 HEIDA);

sodium gluconate;

sodium glucoheptonate;

sugar alcohols;

monosaccharides; and

disaccharides,

 where at least one of the two chelants is selected from the group consisting of sodium polyaspartate, sodium iminodisuccinate, Na 2 HEIDA, and mixtures thereof: and

c) a solvent or surfactant selected from the group consisting of polyvinylpyrrolidone (PVP), alkyl pyrrolidones, alkyl succinates, alkyl glutamates, alkyl carbonates, monoethanol amide, and alkyl glucosides.

2. The biodegradable additive composition of claim 1 , where the amount of the compounds of b) is effective to improve at least one characteristic of a biodegradable fracturing fluid composition to which the biodegradable additive composition is added, which characteristic is selected from the group consisting of:

demulsification;

crosslink gel stabilization

carbonate or sulfate scale inhibitor;

crosslink delay;

enzyme breaker stabilization; and mixtures thereof.

3. The biodegradable additive composition of claim 2 where at least two characteristics are improved.

4. The biodegradable additive composition of claim 1 where in b) at least one of the chelants is selected from the group consisting of sorbitol, mannitol, and xylitol, and saccharides selected from the group consisting of glucoses, fructose, mannose, galactose, lactose, and mixtures thereof.

5. A biodegradable additive composition comprising:

a) water; and

b) at least one chelant selected from the group consisting of sodium iminodisuccinate, disodium hydroxyethyleneiminodiacetate (Na 2 HEIDA), and mixtures thereof;

c) at least one additional chelant selected from the group consisting of:

sodium polyaspartate;

sodium gluconate;

sodium glucoheptonate;

sugar alcohols;

monosaccharides;

disaccharides; and

d) a solvent or surfactant selected from the group consisting of polyvinylpyrrolidone (PVP), alkyl pyrrolidones, alkyl succinates, alkyl glutamates, alkyl alkyl carbonates, monoethanol amide, and alkyl glucosides.

6. The biodegradable additive composition of claim 5 where in at least three chelants are included.

7. The biodegradable additive composition of claim 5 where at least one of the chelants is selected from the group consisting of sorbitol, mannitol, and xylitol, and saccharides selected from the group consisting of glucoses, fructose, mannose, galactose, lactose, and mixtures thereof.

8. A method of fracturing a subterranean formation comprising:

providing a biodegradable fracturing fluid composition having:

a) a crosslinker selected from the group consisting of titanate, zirconate, and borate crosslinkers, compounds that can generate these crosslinkers and mixtures thereof;

b) at least two of the chelants selected from the group consisting of:

sodium polyaspartate;

sodium iminodisuccinate;

disodium hydroxyethyleneiminodiacetate (Na 2 HEIDA);

sodium gluconate;

sodium glucoheptonate;

sugar alcohols;

monosaccharides; and

disaccharides;

 where the amount of the compounds of b) is effective to demulsify the fracturing fluid and where at least one of the two chelants is selected from the group consisting of sodium polyaspartate, sodium iminodisuccinate, Na 2 HEIDA, and mixtures thereof; and

c) water; and

pumping the fracturing fluid down hole at a pressure effective to fracture a subterranean formation.

9. The method of claim 8 , where the amount of the compounds of b) is additionally effective to improve at least one second characteristic of the biodegradable fracturing fluid composition, which second characteristic is selected from the group consisting of:

carbonate or sulfate scale inhibition;

crosslink gel stabilization

crosslink delay; and

enzyme breaker stabilization.

10. The method of claim 8 where in b) at least three of the chelants of the group are included.

11. The method of claim 8 , where the fracturing fluid further comprises a solvent or surfactant selected from the group consisting of polyvinylpyrrolidone (PVP); alkyl glycols, alkyl glycol ethers, alkyl pyrrolidones, alkyl succinates, alkyl glutamates, alkyl sarcosinates, alkyl carbonates, monoethanol amide, alkyl sorbitans, and alkyl glucosides.

12. The method of claim 8 where in b) at least one of the chelants is selected from the group consisting of sorbitol, mannitol, and xylitol, and saccharides selected from the group consisting of glucoses, fructose, mannose, galactose, lactose, and mixtures thereof.

13. A method of fracturing a subterranean formation comprising:

providing a biodegradable fracturing fluid composition having:

a) a crosslinker selected from the group consisting of titanate, zirconate, and borate crosslinkers, compounds that can generate these crosslinkers and mixtures thereof;

b) at least two of the chelants selected from the group consisting of:

sodium polyaspartate;

sodium iminodisuccinate;

disodium hydroxyethyleneiminodiacetate (Na 2 HEIDA);

sodium gluconate;

sodium glucoheptonate;

sugar alcohols;

monosaccharides; and

disaccharides;

 where the amount of the compounds of b) is effective to delay crosslinking of the crosslinkers and where at least one of the two chelants is selected from the group consisting of sodium polyaspartate, sodium iminodisuccinate, Na 2 HEIDA, and mixtures thereof; and

c) water; and

pumping the fracturing fluid down hole at a pressure effective to fracture a subterranean formation.

14. The method of claim 13 , where the amount of the compounds of b) is additionally effective to improve at least one second characteristic of the biodegradable fracturing fluid composition, which second characteristic is selected from the group consisting of:

demulsification;

crosslink gel stabilization

carbonate or sulfate scale inhibition; and

enzyme breaker stabilization.

15. A method of fracturing a subterranean formation comprising:

providing a biodegradable fracturing fluid composition having:

a) a crosslinker selected from the group consisting of titanate, zirconate, and borate crosslinkers, compounds that can generate these crosslinkers and mixtures thereof;

b) at least two of the chelants selected from the group consisting of:

sodium polyaspartate;

sodium iminodisuccinate;

disodium hydroxyethyleneiminodiacetate (Na 2 HEIDA);

sodium gluconate;

sodium glucoheptonate;

sugar alcohols;

monosaccharides; and

disaccharides;

 where the amount of the compounds of b) is effective to improve carbonate or sulfate scale inhibition, as compared with identical fracturing fluids without the compounds of b) and where at least one of the two chelants is selected from the group consisting of sodium polyaspartate, sodium iminodisuccinate, Na 2 HEIDA, and mixtures thereot and

c) water; and

pumping the fracturing fluid down hole at a pressure effective to fracture a subterranean formation.

16. The method of claim 15 , where the amount of the compounds of b) is additionally effective to improve at least one second characteristic of the biodegradable fracturing fluid composition, which second characteristic is selected from the group consisting of:

demulsification;

crosslink gel stabilization

crosslink delay; and

enzyme breaker stabilization.

17. A method of fracturing a subterranean formation comprising:

providing a biodegradable fracturing fluid composition having:

a) a crosslinker selected from the group consisting of titanate, zirconate, and borate crosslinkers, compounds that can generate these crosslinkers and mixtures thereof;

b) at least two of the chelants selected from the group consisting of:

sodium polyaspartate;

sodium iminodisuccinate;

disodium hydroxyethyleneiminodiacetate (Na 2 HEIDA);

sodium gluconate;

sodium glucoheptonate;

sugar alcohols;

monosaccharides; and

disaccharides;

 where the amount of the compounds of b) is effective to improve crosslink gel stabilization of b) as compared with identical fracturing fluids without the compounds of b) and where at least one of the two chelants is selected from the group consisting of sodium polyaspartate, sodium iminodisuccinate, Na 2 HEIDA, and mixtures thereof; and

c) water; and

pumping the fracturing fluid down hole at a pressure effective to fracture a subterranean formation.

18. The method of claim 17 , where the amount of the compounds of b) is additionally effective to improve at least one second characteristic of the biodegradable fracturing fluid composition, which second characteristic is selected from the group consisting of:

demulsification;

carbonate or sulfate scale inhibition

crosslink delay; and

enzyme breaker stabilization.

19. A method of fracturing a subterranean formation comprising:

providing a biodegradable fracturing fluid composition having:

a) a crosslinker selected from the group consisting of titanate, zirconate, and borate crosslinkers, compounds that can generate these crosslinkers and mixtures thereof;

b) at least two of the chelants selected from the group consisting of:

sodium polyaspartate;

sodium iminodisuccinate;

disodium hydroxyethyleneiminodiacetate (Na 2 HEIDA);

sodium gluconate;

sodium glucoheptonate;

disaccharides

 where the amount of the compounds of b) is effective to improve enzyme breaker stabilization of b) as compared with identical fracturing fluids without the compounds of b) and where at least one of the two chelants is selected from the group consisting of sodium polyaspartate, sodium iminodisuccinate, Na 2 HEIDA, and mixtures thereof; and

c) water; and

pumping the fracturing fluid down hole at a pressure effective to fracture a subterranean formation.

20. The method of claim 19 , where the amount of the compounds of b) is additionally effective to improve at least one second characteristic of the biodegradable fracturing fluid composition, which second characteristic is selected from the group consisting of:

demulsification;

crosslink gel stabilization

carbonate or sulfate scale inhibition; and

crosslink delay.

21. A fracturing fluid comprising:

a) water;

b) at least two of the chelants selected from the group consisting of:

sodium polyaspartate;

sodium iminodisuccinate;

disodium hydroxyethyleneiminodiacetate (Na 2 HEIDA);

sodium gluconate;

sodium glucoheptonate;

sugar alcohols;

monosaccharides; and

disaccharides;

 where at least one of the two chelants is selected from the group consisting of sodium polyaspartate, sodium iminodisuccinate, Na 2 HEIDA, and mixtures thereof.

c) a polymer; and

d) a polymer crosslinker selected from the group consisting of titanate, zirconate, and borate crosslinkers, compounds that can generate these crosslinkers and mixtures thereof.

22. The fracturing fluid of claim 21 where in b) at least one of the chelants is selected from the group consisting of sorbitol, mannitol, and xylitol, and saccharides selected from the group consisting of glucoses, fructose, mannose, galactose, lactose, and mixtures thereof.