Methods for making and using UV/EB cured precured particles for use as proppants

1. A method comprising:

making precured free flowing coated particles having a particle size range of about 6 mesh to about 200 mesh, consisting essentially of a particulate substrate having a particle size range of about 6 mesh to about 200 mesh selected from the group consisting of sand and a sintered ceramic particle and a single layer of precured coating disposed upon the substrate, the coating consisting essentially of a continuous phase comprising curable resin in the absence of solid particles in the coating, comprising the steps of:

mixing at a temperature in the range from about 50° F. to about 150° F. the substrate with liquid coating material to form curable coated particles consisting essentially of the substrate and a single layer of continuous phase resin curable coating on the substrate, said liquid coating material comprising at least one curable resin selected from the group consisting of:

epoxy,

urethane acrylate,

epoxy (meth)acrylate,

epoxy-modified novolak resins,

resole resins,

modified resole resins,

terpolymers of phenol, furfuryl alcohol and formaldehyde,

furans,

urethanes,

melamines, and

unsaturated polyesters, and

blends or copolymers thereof;

curing the resin on the curable coated particles to form precured coated particles, wherein the curing comprises exposing the curable coated particles to ultraviolet light or electron beam;

wherein a photoinitiator is added to the resin prior to curing if the resin is to be cured with UV light and wherein a photoinitiator is optionally added to the resin prior to curing if the resin is to be cured with electron beam;

wherein the substrate is at a temperature of about 50° F. to about 150° F. when initially mixed with the resin,

wherein the curing occurs before the resulting precured coated particles are placed into a subterranean formation,

the resin being present in an amount of at most 5% weight percent of the coated particle,

wherein the precured coated particle has a crush strength of less than 20% crush at 10,000 psi.

2. The method of claim 1 , wherein the proppant having a precured coating is stored for at least 1 hour after coating before being placed into the subterranean formation, wherein the curable liquid coating material is applied to the substrate and then the mixing step occurs for a sufficient time to form the continuous phase resin curable coating on the substrate as a uniform coating on the substrate, followed by the curing of the coating.

3. The method of claim 1 , wherein the curing occurs in the absence of added heat from initiation of the mixing to production of the precured coated particles,

wherein the curing occurs in the absence of exposing the curable particles to microwaves.

4. The method of claim 1 , wherein the coated particle has a loss on ignition of from about 1 to about 5 weight %, wherein the precured coated particle has a crush strength of less than 15% crush at 10,000 psi.

5. The method of claim 1 , wherein the curable resin comprises at least one resin selected from the group consisting of epoxies, furans, free methylol-containing melamines, resole, unsaturated polyester, and blends and co-polymers thereof.

6. The method of claim 1 , wherein the curable resin comprises at least one resin selected from the group consisting of bisphenol A based aromatic epoxies, cycloaliphatic epoxies and bisphenol F based epoxy.

7. The method of claim 6 , wherein the coating has an absence of solid particles, wherein the coating has an absence of silicone, silane, toughening agent, rubber and latex.

8. The method of claim 1 , wherein the coating has an absence of rubber or latex.

9. The method of claim 1 , wherein the coating has an absence of solid particles, wherein the coating has an absence of silicone, silane, toughening agent, rubber and latex.

10. The method of claim 1 , wherein the substrate has a particle size in the range from 6 to 100 mesh.

11. The method of claim 1 , wherein the coating comprises at least one member of the group consisting of C2-C16 alkane diol, C2-C16 alkene diol, C2-C16 alkyne diol, and polymeric polyol.

12. The method of claim 1 , wherein the coating comprises additives selected from the group consisting of hardeners, impact modifiers, flow control additives, crosslinking agents, foaming agents, initiators, photosensitizers, thermal stabilizers, light stabilizers, antioxidants, flame retardants, anti-drip agents, antiozonants, stabilizers, anti-corrosion additives, mold release agents, fillers, anti-static agents, pigments, dyes, and the like, or combination comprising at least one of the foregoing.

13. The method of claim 1 , wherein the coated proppant particle has a particle size in the range of about 20/40 mesh and the coated proppant particle generates less than 12 wt % in fines, based on the total weight of the coated proppant particle when subjected to a pressure of greater than or equal to about 10,000 psi according to API RP 56.

14. The method of claim 1 , further comprising treating a subterranean formation, said treating comprising injecting a fracturing fluid into the subterranean formation, wherein the fracturing fluid comprises the coated proppant particle.

15. The method of claim 1 , wherein the photoinitiator is selected from the group consisting of free radical, cationic photoinitiators, and combinations thereof.

16. The method of claim 15 , wherein the cationic photoinitiators are selected from the group consisting of triaryl sulfonium, tetraaryl phosphonium, diaryl iodonium salts, aryldiazonium salts, triarylsulfonium salts, diaryliodonium salts, and combinations thereof.

17. The method of claim 15 , wherein the cationic photoinitiators are selected from the group consisting of unsaturated nitrosamines, diazonium salts, cyclopentadienylmanganese tricarbonyl compounds, metal salts of fluorinated alkane sulfonic acids, aryliodonium salts, aromatic onium salts of the elements of groups VA and VIA, thiopyryllium salts, and combinations thereof.

18. The method of claim 1 , wherein the photoinitiator comprises one or more antioxidants or acrylated silicone additives.

19. The method of claim 1 , further comprising a photosensitizer provided with the photoinitiator.

20. The method of claim 1 , wherein the photoinitiator comprises from about 0.1 to about 10 percent by weight of the coating.

21. The method of claim 1 , wherein the exposing the curable coated particles to ultraviolet light or electron beam comprises applying ultraviolet irradiance at 100-300 watts/inch, an energy density from about 300 mJ/cm 2 to about 20000 mJ/cm 2 , at a wavelength in the spectral range of between about 200 nm to about 450 nm.

22. The method of claim 1 , wherein the exposing the curable coated particles to ultraviolet light or electron beam comprises applying a dosage of electron beam radiation from about 1 Megarad to about 40 Megarad.

23. The method of claim 1 , wherein the method comprises a continuous or batch process.