TECHNICAL FIELD

Embodiments of the present disclosure generally relate to proppant coatings, methods of making the proppant coatings and methods for using proppants having the proppant coating.

BACKGROUND

Hydraulic fracturing is a stimulation treatment routinely performed on oil and gas wells. Hydraulic fracturing fluids are pumped into the subsurface formation to be treated, causing fractures to open in the subsurface formation. Proppants, such as grains of sand of a particular size, may be mixed with the treatment fluid to keep the fracture open when the treatment is complete.

SUMMARY

It is often desirable during and after fracturing a subsurface formation to hold the fractures open through the use of proppants for more effective oil and gas production than without. However, conventional uncoated proppants break under downhole stress. Even coated proppant temperatures downhole exacerbate this effect.

Proppant coatings are used to protect the proppant particle from degradation by the presence of aqueous fluids at downhole temperatures. The proppant coating increases the surface area of the particle; therefore, the crush stress is distributed over a larger area of the coated proppant particle. The proppant coating also adheres to the proppant and prevents proppants that are crushed from releasing proppant fines, which may migrate into the formation and restrict flow conductivity of the formation. Conventional proppant coating techniques to reduce both the crush percentage and the generation of proppant fines are done at temperatures greater than 250° C. Conventional proppant coatings are designed to cure completely prior to the use of coated proppants in fracturing operations. However, even coated proppants can break down when stresses are increased, such as at pressures deep within a subsurface formation.

Accordingly, a need exists for proppant coatings, methods for making proppant coatings, and methods of using coated proppants downhole that can withstand increased stresses. Coated proppants often include a proppant coated with an intermediate polymer layer and an outer resin layer. However, these structures may not be strong enough to withstand pressures greater than 8000 pounds per square inch (psi).

According to a first aspect, a coated proppant comprises: a proppant particle; an intermediate cross-linked terpolymer layer encapsulating the proppant particle; and an outer resin layer encapsulating the intermediate cross-linked terpolymer layer.

A second aspect includes the coated proppant of the first aspect, wherein the proppant particle is selected from the group consisting of oxides, silicates, sand, ceramic, resin, epoxy, plastic, mineral, glass, and combinations thereof.

A third aspect includes the coated proppant of the first or second aspect, wherein the proppant particle is selected from the group consisting of sand, ceramic, glass, and combinations thereof.

A fourth aspect includes the coated proppant of any one of the first to third aspects, wherein the intermediate cross-linked terpolymer layer comprises a combination of monomers and a cross-linking agent.

A fifth aspect includes the coated proppant of the fourth aspect, wherein the combination of monomers comprises a first monomer and a second monomer that is different from the first monomer.

A sixth aspect includes the coated proppant of the fifth aspect, wherein the first monomer is cis- or trans-ethylene substituted aromatic organic compound and the second monomer is an alkyl acrylate.

A seventh aspect includes the coated proppant of the fifth or sixth aspects, wherein the first monomer is styrene.

An eighth aspect includes the coated proppant of any one of the fifth to seventh aspects, wherein the second monomer is methyl methacrylate.

A ninth aspect includes the coated proppant of any one of the fifth to eighth aspects, wherein the first monomer is styrene and the second monomer is methyl methacrylate.

A tenth aspect includes the coated proppant of any one of the fifth to ninth aspects, wherein the first monomer is present in the combination of monomers in an amount from 10.0 wt. % to 90.0 wt. %, and the second monomer is present in the combination of monomers in an amount from 10.0 wt. % to 90.0 wt. %.

An eleventh aspect includes the coated proppant of any one of the fifth to tenth aspects, wherein the first monomer is present in the combination of monomers in an amount from 40.0 wt. % to 60.0 wt. %, and the second monomer is present in the combination of monomers in an amount from 40.0 wt. % to 60.0 wt. %.

A twelfth aspect includes the coated proppant of any one of the fourth to eleventh aspects, wherein the cross-linking agent is selected from the group consisting of divinyl benzene, vinylpyridine, bis(vinylphenyl) ethane, bis(vinylbenzyloxy) hexane, and combinations thereof.

A thirteenth aspect includes the coated proppant of any one of the fourth to twelfth aspects, wherein the cross-linking agent comprises divinyl benzene.

A fourteenth aspect includes the coated proppant of any one of the fourth to thirteenth aspects, wherein the cross-linking agent is present as a super addition relative to the combination of monomers in an amount from 0.5 wt. % to 30.0 wt. %.

A fifteenth aspect includes the coated proppant of any one of the fourth to fourteenth aspects, wherein the cross-linking agent is present as a super addition relative to the combination of monomers in an amount from 1.0 wt. % to 15.0 wt. %.

A sixteenth aspect includes the coated proppant of any one of the first to fifteenth aspects, wherein the outer resin layer comprises a cured epoxy resin and graphene.

A seventeenth aspect includes the coated proppant of the sixteenth aspect, wherein the cured epoxy resin is formed from an epoxy resin and a curing agent.

An eighteenth aspect includes the coated proppant of the sixteenth or seventeenth aspects, wherein the epoxy resin has the following general formula:


wherein R and R′ are selected from the group consisting of a part of a six-membered ring, a polyhydroxyphenol, a polybasic acid, a polyol, and combinations thereof.

A nineteenth aspect includes the coated proppant of the seventeenth aspect, wherein the curing agent is selected from the group consisting of aliphatic polyamines and their derivatives, modified aliphatic amines, aromatic amines, and combinations thereof.

A twentieth aspect includes the coated proppant of any one of the first to nineteenth aspects, wherein the coated proppant produces fine production at a load of 12000 psi that is from 2.0% to 10.0%.

A twenty-first aspect includes the coated proppant of any one of the first to twentieth aspects, wherein the coated proppant produces fine production at a load of 10000 psi that is from 0.5% to 5.0%.

A twenty-second aspect includes the coated proppant of any one of the first to twenty-first aspects, wherein the coated proppant has an elastic modulus from 4.0 GPa to 7.0 GPa.

A twenty-third aspect includes the coated proppant of any one of the first to twenty-second aspects, wherein the coated proppant has a hardness from 0.10 GPa to 0.40 GPa.

A twenty-fourth aspect includes the coated proppant of any one of the first to twenty-third aspects, wherein the proppant particle is selected from the group consisting of sand, ceramic, glass, and combinations thereof; the intermediate cross-linked terpolymer layer comprises styrene, methyl methacrylate, and divinyl benzene; and the outer resin layer comprises a cured epoxy resin formed from an epoxy resin and a curing agent, wherein the epoxy resin has the following general formula:


wherein R and R′ are selected from the group consisting of a part of a six-membered ring, a polyhydroxyphenol, a polybasic acid, a polyol, and combinations thereof, and the curing agent is selected from the group consisting of aliphatic polyamines and their derivatives, modified aliphatic amines, aromatic amines, and combinations thereof.

A twenty-fifth aspect includes a method for producing a coated proppant comprising an intermediate cross-linked terpolymer layer, the method comprising: mixing a monomers solution comprising a first monomer, a second monomer that is different from the first monomer, a cross-linking agent, and an initiator; combining at least one proppant particle with the monomers solution; polymerizing the monomer solution on the surface of the at least one proppant particle to form at least one proppant particle having the intermediate cross-linked terpolymer layer on a surface of the at least one proppant particle; mixing a resin solution comprising an epoxy resin, a curing agent, and graphene; combining the at least one proppant particle having the intermediate cross-linked terpolymer layer on a surface of the at least one proppant particle and the resin solution; curing the resin solution to form the coated proppant comprising an intermediate cross-linked terpolymer layer.

A twenty-sixth aspect includes the method of the twenty-fifth aspect, wherein the proppant particle is selected from the group consisting of sand, ceramic, glass, and combinations thereof.

A twenty-seventh aspect includes the method of the twenty-fifth or twenty-sixth aspect, wherein the first monomer is cis- or trans-ethylene substituted aromatic organic compound and the second monomer is an alkyl acrylate.

A twenty-eighth aspect includes the method of any one of the twenty-fifth to twenty-seventh aspects, wherein the first monomer is styrene and the second monomer is methyl methacrylate.

A twenty-ninth aspect includes the method of any one of the twenty-fifth to twenty-eighth aspects, wherein the first monomer is present in the combination of monomers in an amount from 10.0 wt. % to 90.0 wt. %, and the second monomer is present in the combination of monomers in an amount from 10.0 wt. % to 90.0 wt. %.

A thirtieth aspect includes the method of any one of the twenty-fifth to twenty-ninth aspects, wherein the first monomer is present in the combination of monomers in an amount from 40.0 wt. % to 60.0 wt. %, and the second monomer is present in the combination of monomers in an amount from 40.0 wt. % to 60.0 wt. %.

A thirty-first aspect includes the method of any one of the twenty-fifth to thirtieth aspects, wherein the cross-linking agent is selected from the group consisting of divinyl benzene, vinylpyridine, bis(vinylphenyl) ethane, bis(vinylbenzyloxy) hexane, and combinations thereof.

A thirty-second aspect includes the method of any one of the twenty-fifth to thirty-first aspects, wherein the cross-linking agent comprises divinyl benzene.

A thirty-third aspect includes the method of any one of the twenty-fifth to thirty-second aspects, wherein the cross-linking agent is present as a super addition relative to the first monomer and the second monomer in an amount from 0.5 wt. % to 30.0 wt. %.

A thirty-fourth aspect includes the method of any one of the twenty-fifth to thirty-third aspects, wherein the cross-linking agent is present as a super addition relative to the first monomer and the second monomer in an amount from 1.0 wt. % to 15.0 wt. %.

A thirty-fifth aspect includes the method of any one of the twenty-fifth to thirty-fourth aspects, wherein the initiator is selected from the group consisting of azoisobutyronitrile (AIBN), benzoyl peroxide, tert-butyl peroxide, tert-butyl peracetate, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, peracetic acid, potassium persulfate, and combinations thereof.

A thirty-sixth aspect includes the method of any one of the twenty-fifth to thirty-fifth aspects, wherein the initiator is present as a super addition relative to the first monomer and the second monomer in an amount from 1.0 wt. % to 10.0 wt. %.

A thirty-seventh aspect includes the method of any one of the twenty-fifth to thirty-sixth aspects, wherein the epoxy resin has the following general formula:


wherein R and R′ are selected from the group consisting of a part of a six-membered ring, a polyhydroxyphenol, a polybasic acid, a polyol, and combinations thereof.

A thirty-eighth aspect includes the method of any one of the twenty-fifth to thirty-seventh aspects, wherein the curing agent is selected from the group consisting of aliphatic polyamines and their derivatives, modified aliphatic amines, aromatic amines, and combinations thereof.

A thirty-ninth aspect includes the method of any one of the twenty-fifth to thirty-eighth aspects, wherein the epoxy resin is present in a mixture of the epoxy resin and the curing agent in an amount from 15.0 wt. % to 90.0 wt. %.

A fortieth aspect includes the method of any one of the twenty-fifth to thirty-ninth aspects, wherein the epoxy resin is present in a mixture of the epoxy resin and the curing agent in an amount from 70.0 wt. % to 90.0 wt. %.

A forty-first aspect includes the method of any one of the twenty-fifth to fortieth aspects, wherein the curing agent is present in a mixture of the epoxy resin and the curing agent in an amount from 10.0 wt. % to 85.0 wt. %.

A forty-second aspect includes the method of any one of the twenty-fifth to forty-first aspects, wherein the curing agent is present in a mixture of the epoxy resin and the curing agent in an amount from 10.0 wt. % to 30.0 wt. %.

A forty-third aspect includes the method of any one of the twenty-fifth to forty-second aspects, wherein the graphene is present as a super addition relative to the epoxy resin and the curing agent in an amount from 0.05 wt. % to 0.50 wt. %.

