Proppants for use in hydraulic fracturing of subterranean formations

1. A proppant for a well treatment fluid, the proppant comprising discrete particles of a substrate coated with a resin comprising a product of a Maillard reaction between (1) a carbohydrate and an amine, (2) a carbohydrate and an ammonium compound, or (3) a carbohydrate, an amine, and an ammonium compound, wherein the substrate is coated with two layers of coating, wherein a first, innermost layer comprises a curable, thermosetting resin, wherein a second, outermost layer comprises the product of the Maillard reaction, and wherein the product of the Maillard reaction is formed by heating the substrate coated with the resin to a temperature of about 149° C. to about 316° C.

2. The proppant of claim 1 , wherein the carbohydrate includes a monosaccharide.

3. The proppant of claim 1 , wherein the product of the Maillard reaction forms a water-insoluble coating on the substrate.

4. The proppant of claim 3 , wherein the carbohydrate comprises at least one of dextrose, xylose, fructose, and dihydroxyacetone.

5. The proppant of claim 1 , wherein said Maillard reaction is between the carbohydrate and the ammonium compound, and wherein the ammonium compound comprises an ammonium salt of a carboxylic acid.

6. The proppant of claim 1 , wherein said Maillard reaction is between the carbohydrate and the ammonium compound, and wherein the ammonium compound comprises an ammonium salt of a polycarboxylic acid.

7. The proppant of claim 6 , wherein said polycarboxylic acid comprises citric acid.

8. The proppant of claim 6 , wherein the reaction mixture for forming said resin comprises a polyol.

9. The proppant of claim 8 , wherein the reaction mixture for forming said resin comprises a phosphorous-containing accelerator.

10. The proppant of claim 1 , wherein the substrate is coated with a single layer of a coating comprising the Maillard reaction product.

11. A proppant for a well treatment fluid, the proppant comprising discrete particles of a substrate coated with a resin comprising a product of a Maillard reaction between (1) a carbohydrate and an amine, (2) a carbohydrate and an ammonium compound, or (3) a carbohydrate, an amine, and an ammonium compound, wherein the substrate is coated with two layers of coating, wherein a first, innermost layer comprises a fusible resin, and a second, outermost layer comprises said product of said Maillard reaction, wherein said product of said Maillard reaction is formed by heating the substrate coated with the resin to a temperature of about 149° C. to about 316° C., and wherein said fusible resin is a thermoplastic resin, and wherein the thermoplastic resin comprises an ethylene vinyl acetate, a phenol-formaldehyde novolac resin, a pine rosin, a modified rosin, a rosin ester, a terpene resin, a coumarone-indene resin, an oligomer of C 5 hydrocarbons, an oligomer of C 9 hydrocarbons, an oligomeric reaction product of a terpene and a phenolic, and an oligomeric reaction product of a terpene and a styrenic, or any combination thereof.

12. The proppant of claim 1 , wherein said curable, thermosetting resin is selected from phenol-aldehyde resins, urea-aldehyde resins, melamine-aldehyde resins, epoxy resins, furfuryl alcohol resins, and copolymers of such resins.

13. The proppant of claim 1 , wherein the substrate particles comprise at least one of sand, glass beads, ceramics, carbon particles, and bauxite.

14. The proppant of claim 1 , wherein the substrate particles comprise as least one of crushed nut hulls and other natural fibers.

15. A fracturing fluid for stimulating hydrocarbon production from a subterranean formation, the fracturing fluid comprising a suspension of a carrier liquid and a proppant comprising discrete particles of a substrate coated with two layers of coating, wherein a first, innermost layer comprises a curable, thermosetting resin, wherein a second, outermost layer comprises a product of a Maillard reaction between (1) a carbohydrate and an amine, (2) a carbohydrate and an ammonium compound, or (3) a carbohydrate, an amine, and an ammonium compound, and wherein the product of the Maillard reaction is formed by heating the substrate coated with the resin to a temperature of about 149° C. to about 316° C.

16. The fracturing fluid of claim 15 , wherein the carbohydrate includes a monosaccharide.

17. The fracturing fluid of claim 15 , wherein the product of the Maillard reaction forms a water-insoluble coating on the substrate.

18. The fracturing fluid of claim 15 , wherein the carbohydrate comprises at least one of dextrose, xylose, fructose, and dihydroxyacetone.

19. The fracturing fluid of claim 18 , wherein said Maillard reaction is between the carbohydrate and the ammonium compound, and wherein the ammonium compound comprises an ammonium salt of a carboxylic acid.

20. The fracturing fluid of claim 15 , wherein said Maillard reaction is between the carbohydrate and the ammonium compound, and wherein the ammonium compound comprises an ammonium salt of a polycarboxylic acid.

21. The fracturing fluid of claim 20 , wherein said polycarboxylic acid comprises citric acid.

22. The fracturing fluid of claim 15 , wherein the curable, thermosetting resin is selected from phenol-aldehyde resins, urea-aldehyde resins, melamine-aldehyde resins, epoxy resins, furfuryl alcohol resins, and copolymers of such resins.

23. The fracturing fluid of claim 15 , wherein the substrate comprises at least one of sand, glass beads, ceramics, carbon particles, and bauxite.

24. The proppant of claim 1 , wherein the substrate has a mesh size between 6 and 100 based on the U.S. Standard Sieve Series, wherein the coating of the resin comprising the product of the Maillard reaction on the substrate has a thickness of about 0.1 mils to about 5 mils, and wherein less than 5% by weight of the proppant is agglomerated.

25. The proppant of claim 1 , wherein the product of the Maillard reaction is between the carbohydrate, the amine, and the ammonium compound.

26. The proppant of claim 1 , wherein the substrate comprises at least one of sand, ceramics, carbon particles, bauxite, pecan shells, and walnut shells.

27. The proppant of claim 1 , wherein the ammonium compound comprises an ammonium salt of a carboxylic acid, and wherein a molar ratio of the ammonium salt of the carboxylic acid to the carbohydrate is about 1:4 to about 1:7.

28. The proppant of claim 1 , wherein the amine comprises ammonia, a primary amine, or a secondary amine.

29. The proppant of claim 1 , wherein the amine comprises ammonia, ethylamine, diethylamine, dimethylamine, ethylpropylamine, aniline, 1-naphthylamine, 2-naphthylamine, or para-aminophenol.

30. The proppant of claim 1 , wherein the proppant contains about 1 wt % to about 6 wt % of the resin based on the weight of the substrate.

31. The proppant of claim 1 , wherein the substrate has a mesh size between 6 and 100 based on the U.S. Standard Sieve Series, wherein the coating of the resin comprising the product of the Maillard reaction on the substrate has a thickness of about 0.1 mils to about 5 mils, wherein less than 5% by weight of the proppant is agglomerated, wherein the substrate comprises at least one of sand, ceramics, carbon particles, and bauxite, wherein the ammonium compound comprises an ammonium salt of a carboxylic acid, wherein a molar ratio of the ammonium salt of the carboxylic acid to the carbohydrate is about 1:4 to about 1:7, wherein the proppant contains about 1 wt % to about 6 wt % of the resin based on the weight of the substrate, and wherein the product of the Maillard reaction forms a water-insoluble coating on the substrate.