阅读说明：本技术 经涂覆的支撑剂以及其制造方法和用途 (Coated proppants and methods of making and using the same ) 是由 B·拉格哈瓦·雷迪 梁枫 于 2020-03-25 设计创作，主要内容包括：提供了用于产生具有嵌段共聚物支撑剂涂层的支撑剂的方法。所述方法包括用所述嵌段共聚物支撑剂涂层涂覆支撑剂颗粒以生产具有嵌段共聚物支撑剂涂层的经涂覆的支撑剂。所述嵌段共聚物支撑剂涂层是具有至少一个共聚物主链的嵌段共聚物组合物。每个共聚物主链包含至少两个硬链段和设置在所述至少两个硬链段之间的软链段。此外,提供了一种包含支撑剂颗粒和嵌段共聚物支撑剂涂层的支撑剂。所述嵌段共聚物支撑剂涂层是具有至少一个共聚物主链的嵌段共聚物组合物,其中每个共聚物主链包含至少两个硬链段。软链段设置在所述至少两个硬链段之间。所述共聚物主链具有至少一个接枝到所述软链段上的酸酐基团。此外,所述酸酐基团通过含胺交联剂交联。(Methods for producing proppants having a block copolymer proppant coating are provided. The method comprises coating proppant particles with the block copolymer proppant coating to produce a coated proppant having a block copolymer proppant coating. The block copolymer proppant coating is a block copolymer composition having at least one copolymer backbone. Each copolymer backbone comprises at least two hard segments and a soft segment disposed between the at least two hard segments. In addition, a proppant comprising proppant particles and a coating of block copolymer proppant is provided. The block copolymer proppant coating is a block copolymer composition having at least one copolymer backbone, wherein each copolymer backbone comprises at least two hard segments. The soft segment is disposed between the at least two hard segments. The copolymer backbone has at least one anhydride group grafted to the soft segment. Further, the anhydride groups are crosslinked by an amine-containing crosslinking agent.)

1. A method of making a coated proppant having a block copolymer proppant coating, the method comprising:

coating a proppant particle with the block copolymer proppant coating to produce a coated proppant having a block copolymer proppant coating, wherein the block copolymer proppant coating is a block copolymer composition having at least one copolymer backbone, each copolymer backbone comprising at least two hard segments, and a soft segment disposed between the at least two hard segments.

2. The method of claim 1, further comprising forming the block copolymer proppant coating by adding at least one anhydride group to soft segments of at least one copolymer backbone.

3. The method of claim 2, wherein the anhydride groups comprise succinic anhydride groups, maleic anhydride groups, or a combination thereof.

4. The method of claim 2 or 3, wherein the anhydride group is grafted to one of a secondary or tertiary carbon of the soft segment.

5. The method of any one of claims 2 to 4, further comprising crosslinking the anhydride groups with an amine-containing crosslinking agent prior to coating the proppant particles with the block copolymer proppant coating, wherein the amine-containing crosslinking agent comprises 3- (2-aminoethylaminopropyl) trimethoxysilane, 3-aminopropyltriethoxysilane, or a combination thereof.

6. The method of any one of claims 2 to 4, further comprising crosslinking the anhydride groups with an amine-containing crosslinking agent after coating the proppant particles with the block copolymer proppant coating, wherein the amine-containing crosslinking agent comprises 3- (2-aminoethylaminopropyl) trimethoxysilane, 3-aminopropyltriethoxysilane, or a combination thereof.

7. The method of any one of claims 2 to 6, further comprising heating the proppant particles to 100 ℃ to 210 ℃, mixing the proppant particles and the block copolymer proppant coating to form a mixture, cooling the mixture, and adding an amine-containing cross-linking agent to the mixture after cooling.

8. The method of any preceding claim, wherein coating the proppant particle with a block copolymer proppant coating comprises coating the proppant particle with a block copolymer proppant coating in an amount of 1 to 10 weight percent, calculated based on the weight of the proppant particle.

9. The method of any preceding claim, wherein the hard segment comprises at least one aromatic moiety and the soft segment is unsaturated.

10. The method of any preceding claim, wherein:

the hard segment comprises the polymerization product of at least one monomer selected from the group consisting of styrene, alpha-methylstyrene, methacrylates, polyamides, and polyamines; and is

The soft segment includes the polymerization product of one or more monomers selected from the group consisting of butene, butadiene, ethylene, tetrahydrofuran, ethylene oxide, propylene oxide, and acrylic acid.

11. The method of any preceding claim, wherein the hard segments are end blocks and the soft segments are aliphatic.

12. The method of any preceding claim, wherein the block copolymer having the grafted anhydride groups comprises the formula

13. The method of any preceding claim, wherein the block copolymer comprises a styrene-ethylene-butylene-styrene (SEBS) block copolymer, a polyether block amide (PEBA) block copolymer, or both.

14. The method of any preceding claim, wherein:

the block copolymer has an A-B-A structure, where A and B are two compositionally different subunits.

15. A coated proppant, said coated proppant comprising:

proppant particulates comprising sand, ceramic materials, or combinations thereof; and

a block copolymer proppant coating the proppant particles, wherein

The block copolymer proppant coating is a block copolymer composition having at least one copolymer backbone, each copolymer backbone comprising at least two hard segments and a soft segment disposed between the at least two hard segments, wherein the copolymer backbone has at least one anhydride group grafted to the soft segment, and the anhydride groups are crosslinked by an amine-containing crosslinking agent.

16. The coated proppant of claim 15, wherein:

the block copolymer comprises a styrene-ethylene-butylene-styrene (SEBS) block copolymer, a polyether block amide (PEBA) block copolymer, or both; and is

The anhydride group includes a succinic anhydride group, a maleic anhydride group, or a combination thereof.

17. The coated proppant of any one of claims 15-16, wherein the block copolymer having the grafted anhydride groups comprises the formula

18. The coated proppant of any one of claims 15-17, wherein:

the coated proppant has a percent crush of less than 10% at 6000psi,

the coated proppant has a percent crush of less than 25% at 8000 psi; and is

The tensile strength of the block copolymer proppant coating is 3000psi to 5000 psi.

19. The coated proppant of any one of claims 15 to 18, wherein the block copolymer proppant coating further comprises a tracer material comprising thorium dioxide (ThO)₂) Barium sulfate ((BaSO)₄) At least one of diatrizoate, metrizoate, iophthalate, iodixanate, iopamidol, iohexol, ioxilan (ioxilan), iopromide, iodixanol, and ioversol.

20. A method for increasing the rate of hydrocarbon production from a subterranean formation, the method comprising:

producing a first rate of production of hydrocarbons from the subterranean formation;

introducing into the subterranean formation a hydraulic fracturing fluid comprising a plurality of the coated proppants of any one of claims 15 to 19; and

increasing hydrocarbon production from the subterranean formation by producing a second rate of hydrocarbon production from the subterranean formation, wherein the second rate of hydrocarbon production is greater than the first rate of hydrocarbon production.

Technical Field

Embodiments of the present disclosure relate generally to coated proppants and methods of using the same.

Background

Hydraulic fracturing is a conventional stimulation treatment performed on oil and gas wells. A hydraulic fracturing fluid is pumped into the subterranean formation to be treated such that the fracture opens in the subterranean formation. Proppants, such as sand particles of a particular size, may be mixed with the treatment fluid to hold the fracture open when the treatment is complete.

Disclosure of Invention

During and after fracturing a subterranean formation, it is often desirable to keep the fracture open through the use of proppants in order to produce hydrocarbons more efficiently than when no proppants are used. However, conventional uncoated proppants fracture under downhole stress. In particular, uncoated ceramic proppants can decompose under humid conditions, causing them to lose their crush resistance. Downhole temperatures exacerbate this effect.

The proppant coating serves to protect the proppant particles from degradation due to the presence of the aqueous fluid at downhole temperatures. The proppant coating increases the surface area of the particle; thus, the crushing stress is distributed over a larger area of the coated proppant particle. In turn, the force distribution along a larger area should be such that the amount of proppant particles that are crushed, also referred to as the 'percent crush', is reduced. The proppant coating also adheres to the proppant and prevents the crushed proppant from releasing proppant fines that may migrate into the formation and limit the formation's conductivity. Conventional proppant coating techniques for reducing both the percent crush and proppant fines generation are accomplished at temperatures above 250 ℃. Conventional proppant coatings are designed to fully cure before the coated proppant is used in a fracturing operation.

Thus, there is a need for coated proppants and methods of using the same downhole, as well as methods of producing such coated proppants that require a cure temperature of less than 250 ℃. Likewise, the coated proppant should be partially or fully cured prior to use. There is also a continuing need for coated proppants and methods of producing coated proppants having an elastomeric coating. The elastomeric coating increases the crush strength of the coated proppant so that the coated proppant can withstand greater closure stresses without fracturing the proppant particles than uncoated proppant particles. This results in a reduction in the percentage of proppant material that is crushed. Also, the coating encapsulates and adheres to the proppant material such that at least some of the fines that may be generated when the coated proppant is crushed are trapped within or on the block copolymer coating; thus, the amount of "free fines" released is reduced compared to uncoated proppant. The subject matter disclosed herein and embodiments thereof address these needs by providing a coated proppant material comprising an encapsulating polymer, including a block copolymer. In some embodiments, the encapsulating polymer may be crosslinked. In some embodiments, the polymer comprises a polystyrene-polyvinylbutylene-polystyrene-graft-maleic anhydride (PS-PEB-PS-g-MA) copolymer.

The crosslinked block copolymer proppant coating is a crosslinked block copolymer that is the product of the reaction between the block copolymer and the crosslinking agent. In some embodiments, the block copolymer comprises at least two hard segments, and a soft segment disposed between the two hard segments. In some embodiments, at least one anhydride group is grafted to the soft segment. In some embodiments, the block copolymer comprises polystyrene-polyvinylbutylene-polystyrene-grafted maleic anhydride (PS-PEB-PS-g-MA). In some embodiments, the crosslinking agent is an amine-containing crosslinking agent. In some embodiments, the amine-containing crosslinker may include 3- (2-aminoethylaminopropyl) trimethoxysilane, 3-aminopropyltriethoxysilane, or a combination thereof.

Drawings

The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

fig. 1 is a schematic illustration of proppant particles and coated proppants according to one or more embodiments described in this disclosure.

Detailed Description

As used throughout this disclosure, the term "block copolymer" refers to a polymer having at least two compositionally different subunits (a and B) derived from different monomer species. The at least two compositionally different subunits are covalently bonded to each other and linearly oriented.

As used throughout this disclosure, the term "polymer backbone" or "copolymer backbone," which may also be referred to as a "backbone," is a linearly oriented polymer chain to which all side chains or moieties are attached or grafted.

As used throughout this disclosure, the term "grafting" refers to a reaction in which one or more compositions are attached as side chains to a backbone or polymeric backbone, where the grafted composition is compositionally different from the polymeric backbone.

As used throughout this disclosure, the term "cross-linking" refers to the covalent bonding of a first polymer chain to a second polymer chain using a cross-linking agent.

As used throughout this disclosure, the terms "soft segment" and "hard segment" refer to the relevant block portion (or block) of the polymer chain. The soft segment is a block portion of the polymer chain that, if the polymer chain is in pure homopolymer form, will have a reduced glass transition temperature and will have a lower stiffness than a pure homopolymer form of a similarly blocked hard segment.

As used throughout this disclosure, the term "layered roughness" refers to a micro roughness covered by a nano roughness.

As used throughout this disclosure, the term "hydraulic fracturing" refers to stimulation treatments performed on reservoirs having a permeability of less than 10 millidarcies. The hydraulic fracturing fluid is pumped into the subterranean formation such that fractures are formed. The wings of the fracture extend outward from the wellbore in opposite directions, depending on the natural stresses within the subterranean formation. The proppant is mixed with the treatment fluid to keep the fracture open when the treatment is complete. Hydraulic fracturing is in fluid communication with a subterranean formation and bypasses damage that may exist in the near wellbore region.

As used throughout this disclosure, the term "subterranean formation" refers to a rock body that is sufficiently distinct and continuous from the surrounding rock body so that the rock body can be divided into distinct entities. Thus, the subterranean formation is sufficiently homogeneous to form a single identifiable unit that contains similar rheological properties, including but not limited to porosity and permeability, throughout the subterranean formation. The subsurface formation is the basic unit of rock stratigraphy.

As used throughout this disclosure, the term "lithostatic pressure" refers to the pressure of the weight of overburden or overburden rock against the subterranean formation.

As used throughout this disclosure, the term "oleaginous subterranean formation" refers to a subterranean formation from which hydrocarbons are produced.

As used throughout this disclosure, the term "proppant" refers to a particle that is capable of holding open a fracture after a hydraulic fracturing treatment is completed.

As used throughout this disclosure, the term "reservoir" refers to a subterranean formation having sufficient porosity and permeability to store and transport fluids.

As used throughout this disclosure, the term "wellbore" refers to a borehole or wellbore, including an open hole or uncased section of a well. A wellbore may refer to a pore space defined by a wellbore wall in which a rock face bounding a borehole defines the wellbore.

A production well is a fluid conduit that enables hydrocarbons to travel from a subterranean formation to the surface. As hydrocarbons are produced, the pressure in the formation decreases as the amount of gas in the formation decreases. If the pressure in the formation drops below the dew point of the hydrocarbon gas, a hydrocarbon liquid condensate is formed. Such liquid condensate may cause fluid blockages in the formation and restrict fluid pathways between the formation and the wellbore.

The present disclosure relates to compositions, methods of production, and methods of using block copolymer encapsulated proppants. In some embodiments, the proppant comprises proppant particles comprising sand, a ceramic material, or a combination thereof. The proppant coating that encapsulates the proppant particles can comprise a block copolymer composition and have copolymer backbones, wherein each copolymer backbone further comprises at least two hard segment blocks and a soft segment block disposed between the two hard segment blocks. In some embodiments, the copolymer backbone is further grafted with an anhydride on the soft segment block. In some embodiments, the grafted anhydride is maleic anhydride. Further, in some embodiments, the anhydride may be crosslinked by an amine-based crosslinking agent. In some embodiments, the amine-containing crosslinker may include 3- (2-aminoethylaminopropyl) trimethoxysilane, 3-aminopropyltriethoxysilane, or a combination thereof. The block copolymer proppant coating can have a uniform thickness or can contain variations throughout the thickness, resulting in a layered roughness in the block copolymer proppant coating.

The uncrosslinked block copolymer can be used as a thermoplastic elastomer to improve the elasticity of the block copolymer proppant coating. In embodiments, the crosslinked block copolymer may be used as a thermoset elastomer. In embodiments, the crosslinked block copolymer may include thermally reversible crosslinks.

In embodiments where the block copolymer is not crosslinked, the block copolymer composition may melt at a particular temperature range (referred to as the melting temperature) to create a flowable medium. The block copolymer composition can resolidify upon cooling below the melting temperature.

In embodiments where the crosslinked block copolymer comprises thermally reversible crosslinks, the crosslinks may be reversed at the melting temperature, thereby creating a flowable medium. Upon cooling below the melting temperature, the crosslinks may reform such that the block copolymer composition may resolidify upon cooling below the melting temperature and crosslink again.

This cyclic process can be repeated an infinite number of times, meaning that the block copolymer proppant coating can be used as a solid proppant coating at a temperature below the melting temperature. Furthermore, this means that the block copolymer proppant coating can melt when the temperature is raised to equal to or above the melting temperature and can return to a solid block copolymer proppant coating when the temperature is lowered below the melting temperature. This behavior is different from that of conventional thermoset rubbers. Conventional thermoset rubbers are single phase materials with irreversible chemical bonds that are not melt or melt processable.

In embodiments where the crosslinked block copolymer does not include thermoreversible crosslinks and is used as a thermoset elastomer, the crosslinked block copolymer may exhibit rubber-like elasticity but may not deform due to the matrix structure of the crosslinked block copolymer. In addition, the crosslinked block copolymer does not melt at a temperature of at least 100 ℃, 150 ℃, 200 ℃, 250 ℃, 300 ℃, 350 ℃, or at least 400 ℃. Without being bound by theory, the crosslinked block copolymer may not dissolve if exposed to a hydrocarbon or water-based solution. Conversely, if exposed to a hydrocarbon, the crosslinked block copolymer may swell from 0.5 weight percent (wt%) to 6 wt%, from 0.5 wt% to 5 wt%, from 0.5 wt% to 4.5 wt%, from 0.5 wt% to 4 wt%, from 0.5 wt% to 3.5 wt%, from 0.5 wt% to 3 wt%, from 0.5 wt% to 2.5 wt%, from 2 wt% to 6 wt%, from 2 wt% to 5 wt%, from 2 wt% to 4.5 wt%, from 2 wt% to 4 wt%, from 2 wt% to 3.5 wt%, from 2 wt% to 3 wt%, from 2 wt% to 2.5 wt%, from 2.5 wt% to 6 wt%, from 2.5 wt% to 5 wt%, from 2.5 wt% to 4 wt%, from 2.5 wt% to 3 wt%, from 3 wt% to 6 wt%, from 3 wt% to 5 wt%, from 3 wt% to 4.5 wt%, from 3 wt% to 3.5 wt%, from 3 wt% to 4.5 wt%, from 3 wt%, or from 3 wt% to 3.5 wt% of the polymer, or a polymer, and a polymer, and a polymer, and a polymer, and a, 3.5 to 6 wt%, 3.5 to 5 wt%, 3.5 to 4.5 wt%, 3.5 to 4 wt%, 4 to 6 wt%, 4 to 5 wt%, 4 to 4.5 wt%, 4 to 6 wt%, 4.5 to 5 wt%, or 5 to 6 wt%.

Since the hard segment and the soft segment have different glass transition temperatures, the block copolymer functions as a thermoplastic elastomer. As used herein, "segment" and "block" are used interchangeably. Glass transition is a gradual and reversible transition in an amorphous material (or in amorphous regions within a semi-crystalline material) from a hard and relatively brittle "glassy" state to a viscous or rubbery state with increasing temperature. Glass transition temperature T of the material_gThe temperature range over which this glass transition occurs is characterized. The glass transition temperature of the homopolymer material (i.e., consisting of the same monomeric units) is lower than the melting temperature T of the crystalline state of the homopolymer material_m。

The soft segment has a glass transition temperature lower than the glass transition temperature of the hard segment. In many cases, T of the Soft segment_gLess than 20 ℃ and T of the hard segment_gIs at least 80 ℃, at least 90 ℃, at least 100 ℃, at least 150 ℃, at least 200 ℃, at least 250 ℃, at least 300 ℃, at least 350 ℃, or at least 400 ℃.

T of hard segment_gCan be from 80 ℃ to 400 ℃, from 80 ℃ to 350 ℃, from 80 ℃ to 300 ℃, from 80 ℃ to 250 ℃, from 80 ℃ to 200 ℃, from 80 ℃ to 150 ℃, from 80 ℃ to 100 ℃, from 80 ℃ to 90 ℃, from 90 ℃ to 400 ℃, from 90 ℃ to 350 ℃, from 90 ℃ to 300 ℃, from 90 ℃ to 250 ℃, from 90 ℃ to 200 ℃, from 90 ℃ to 150 ℃, from 90 ℃ to 100 ℃, from 100 ℃ to 400 ℃, from 100 ℃ to 350 ℃, from 100 ℃ to 300 ℃, from 100 ℃ to 250 ℃, from 100 ℃ to 200 ℃, from 150 ℃ to 400 ℃, from 150 ℃ to 350 ℃, from 150 ℃ to 300 ℃, from 150 ℃ to 250 ℃, from 150 ℃ to 200 ℃, from 200 ℃ to 400 ℃, from 200 ℃ to 350 ℃, from 200 ℃ to 300 ℃, from 200 ℃ to 250 ℃, from 250 ℃ to 400 ℃, from 250 ℃ to 350 ℃, from 300 ℃ to 400 ℃, from 300 ℃ to 350 ℃, or from 350 ℃ to 400 ℃.

Further, the hard segment may comprise at least one aromatic moiety. Specifically, the hard segment may include a polymerization product of at least one monomer selected from styrene, α -methylstyrene, methacrylate, polyamide and polyamine.

As used herein, a block copolymer is a polymer having at least two compositionally different subunits (a and B) derived from different monomer species. In one or more embodiments, these segments can include oligomers or homopolymers. In another embodiment, the block copolymer may have at least three different subunits A, B and C in the block copolymer backbone. As used herein, "segment" and "block" may sometimes be used interchangeably as "subunit", but not in most cases. For example, a block copolymer may have an A-B-A structure, meaning that there are only two subunits, A and B, that differ in composition; however, the polymer backbone has three segments, wherein two of the three segments (i.e., the a segment) have the same composition. As previously mentioned, in some embodiments, the block copolymer composition comprises at least one anhydride group grafted to the block copolymer backbone. In a further embodiment, these anhydrides may be crosslinked by amine-containing crosslinkers.

The block copolymer composition includes at least one copolymer backbone. Each copolymer backbone comprises at least two hard segments and one soft segment. The hard segment may be an end block of the block copolymer. Alternatively, the copolymer backbone may comprise more than one soft segment, and these soft segments may be end blocks of the block copolymer. In some embodiments, the block copolymer has at least two hard segments and at least one soft segment, wherein one soft segment of the at least one soft segment is disposed between two hard segments of the at least two hard segments. In some embodiments, the two hard segments are disposed as end blocks of the block copolymer. In some embodiments, there is more than one soft segment between two hard segments disposed as end blocks of a block copolymer. In some embodiments, only one of the two hard segments is provided as an end block of the block copolymer. In some embodiments, no hard segments are provided as end blocks of the block copolymer backbone. In some such embodiments, the two soft segments are disposed as end blocks of the block copolymer.

As previously mentioned, each copolymer backbone contains at least two hard segments and one soft segment. The soft segment is disposed between at least two hard segments. The soft segment may be aliphatic. In some embodiments, the soft segment comprises the polymerization product of one or more monomers selected from the group consisting of butene, butadiene, ethylene, tetrahydrofuran, ethylene oxide, propylene oxide, and acrylic acid. The soft segment can be unsaturated. The glass transition temperature of the soft segment may be-100 ℃ to-50 ℃, -100 ℃ to-55 ℃, -100 ℃ to-60 ℃, -100 ℃ to-65 ℃, -100 ℃ to-70 ℃, -100 ℃ to-75 ℃, -100 ℃ to-80 ℃, -100 ℃ to-85 ℃, -100 ℃ to-90 ℃, -100 ℃ to-95 ℃, -95 ℃ to-80 ℃, -95 ℃ to-85 ℃, -95 ℃ to-90 ℃, -90 ℃ to-80 ℃, -90 ℃ to-85 ℃, -80 ℃ to-50 ℃, -80 ℃ to-55 ℃, -80 ℃ to-60 ℃, -80 ℃ to-65 ℃, -80 ℃ to-70 ℃, -80 ℃ to-75 ℃, -75 ℃ to-50 ℃, -75 ℃ to-55 ℃, -75 ℃ to-60 ℃, -75 ℃ to-65 ℃, -75 ℃ to-70 ℃, -70 ℃ to-50 ℃, -70 ℃ to-55 ℃, -70 ℃ to-60 ℃, -70 ℃ to-65 ℃, -65 ℃ to-50 ℃, -65 ℃ to-55 ℃, -65 ℃ to-60 ℃, -60 ℃ to-50 ℃, -60 ℃ to-55 ℃, -100 ℃ to 20 ℃, -80 ℃ to 20 ℃, -60 ℃ to 20 ℃, -40 ℃ to 20 ℃, -20 ℃ to 20 ℃, 0 ℃ to 20 ℃, 10 ℃ to 20 ℃, -100 ℃ to 10 ℃, -60 ℃ to 10 ℃, -40 ℃ to 10 ℃, -20 ℃ to 10 ℃, 0 ℃ to 10 ℃, 100 ℃ to 0 ℃, 80 ℃ to 0 ℃, 60 ℃ to 0 ℃, 40 ℃ to 0 ℃, 20 ℃ to 0 ℃, 100 ℃ to-20 ℃, 80 ℃ to-20 ℃, 60 ℃ to-20 ℃, 40 ℃ to-20 ℃, or-60 ℃ to-40 ℃.

In addition, the copolymer backbone has at least one anhydride group grafted to the soft segment. The anhydride group can be grafted to one of the secondary or tertiary carbons of the soft segment. In some embodiments, the anhydride group comprises a succinic anhydride group, a maleic anhydride group, or a combination thereof. Specifically, the block copolymer having at least one anhydride group grafted to the soft segment may be a SEBS block copolymer and include the following formula:

in some embodiments, the block copolymer may include a styrene-ethylene-butylene-styrene (SEBS) block copolymer, a linear block copolymer comprising two styrene blocks and an ethylene/butylene block. The polystyrene content of the SEBS block copolymer can be 10 wt% to 40 wt%, 10 wt% to 35 wt%, 10 wt% to 30 wt%, 10 wt% to 25 wt%, 10 wt% to 20 wt%, 10 wt% to 15 wt%, 13 wt% to 40 wt%, 13 wt% to 35 wt%, 13 wt% to 30 wt%, 13 wt% to 25 wt%, 13 wt% to 20 wt%, 13 wt% to 15 wt%, 15 wt% to 40 wt%, 15 wt% to 35 wt%, 15 wt% to 30 wt%, 15 wt% to 25 wt%, 15 wt% to 20 wt%, 20 wt% to 40 wt%, 20 wt% to 35 wt%, 20 wt% to 30 wt%, 25 wt% to 40 wt%, 25 wt% to 35 wt%, 25 wt% to 30 wt%, 30 wt% to 40 wt%, or a combination thereof, 30 to 35 wt%, 35 to 40 wt%, 30 wt%, or 13 wt%. The specific gravity of the SEBS block copolymer can be from 0.8g/cc to 0.95g/cc, from 0.8g/cc to 0.9g/cc, from 0.85g/cc to 0.95g/cc, from 0.85g/cc to 0.9g/cc, from 0.9g/cc to 0.95g/cc, or from 0.91 g/cc. In other embodiments, the block copolymer may comprise a polyether block amide (PEBA) block copolymer. The PEBA block copolymer is produced by polycondensation of a carboxylic polyamide with an alcohol-terminated polyether to produce HO- (CO-PA-CO-O-PE-O)_n-H, wherein PA is a polyamide and PE is a polyether. The PEBA block copolymer is commercially available as VESTAMID manufactured by Evonik Corporation.

The block copolymer composition can comprise 0 wt% to 10 wt%, 0 wt% to 5 wt%, 0 wt% to 3 wt%, 0 wt% to 2 wt%, 0 wt% to 1.5 wt%, 0 wt% to 1 wt%, 0 wt% to 0.5 wt%, 0.5 wt% to 10 wt%, 0.5 wt% to 5 wt%, 0.5 wt% to 3 wt%, 0.5 wt% to 2 wt%, 0.5 wt% to 1.5 wt%, 0.5 wt% to 1 wt%, 1 wt% to 10 wt%, 1 wt% to 5 wt%, 1 wt% to 3 wt%, 1 wt% to 2 wt%, 1 wt% to 1.5 wt%, 1.5 wt% to 10 wt%, 1.5 wt% to 5 wt%, 1.5 wt% to 3 wt%, 1.5 wt% to 2 wt%, 2 wt% to 10 wt%, 2 wt% to 5 wt%, 2 wt% to 3 wt%, 2 wt% to 5 wt%, 2 wt% to 3 wt%, 0 wt% to 3 wt%, 0.5 wt%, 0 wt%, 0.5 wt% to 0.5 wt%, 0 wt%, 0.5 wt% to 10 wt%, 0.5 wt% to 10 wt%, 0.10 wt%, 0.5 wt%, 1 wt%, 0.5 wt%, 1.5 wt%, 2 wt%, 0.1 wt%, 2 wt%, 0.5 wt%, 0., 3 to 10 weight percent, 3 to 5 weight percent, or 5 to 10 weight percent of anhydride groups. The block copolymer composition may comprise 1.4 to 2 weight percent of anhydride groups.

Finally, the copolymer backbone may be crosslinked. A crosslinking agent is a substance or agent that induces the formation of crosslinks in a subterranean formation. Mixing the block copolymer with the crosslinking agent results in a chemical reaction that crosslinks the block copolymer. The cross-linked block copolymer proppant coating can retain its shape without dissolving in the hydraulic fracturing fluid while maintaining sufficient attraction or bonding with the proppant particles. The degree of crosslinking can be controlled by the molar or weight ratio of crosslinking agent to monomer. Without being bound by theory, crosslinking prevents the block copolymer from melting and increases the elasticity of the block copolymer. The degree of crosslinking directly affects the elasticity of the block copolymer proppant coating. The degree of crosslinking, reflected by the swelling value, can be controlled by the amount of crosslinker added, as well as the duration and temperature of crosslinking. In some embodiments, the crosslinking agent may include at least one of hexamethylenetetramine, paraformaldehyde, oxazolidine, melamine resin, aldehyde donor, resole polymer, and aminosilane crosslinking agent.

In some embodiments, the crosslinking agent may be an amine-containing crosslinking agent. The amine-containing crosslinker may be an aminosilane crosslinker. The aminosilane may include at least one of 3- (2-aminoethylaminopropyl) trimethoxysilane and 3-aminopropyltriethoxysilane. The block copolymer composition may comprise 0 wt% to 5 wt%, 0 wt% to 3 wt%, 0 wt% to 2 wt%, 0 wt% to 1.5 wt%, 0 wt% to 1 wt%, 0 wt% to 0.5 wt%, 0.5 wt% to 5 wt%, 0.5 wt% to 3 wt%, 0.5 wt% to 2 wt%, 0.5 wt% to 1.5 wt%, 0.5 wt% to 1 wt%, 1 wt% to 5 wt%, 1 wt% to 3 wt%, 1 wt% to 2 wt%, 1 wt% to 1.5 wt%, 1.5 wt% to 5 wt%, 1.5 wt% to 3 wt%, 1.5 wt% to 2 wt%, 2 wt% to 5 wt%, 2 wt% to 3 wt%, or 3 wt% to 5 wt% of the aminosilane. The block copolymer composition may comprise 1 wt%, 1.3 wt%, or 1.4 wt% of the aminosilane.

The block copolymer proppant coating may be insoluble in hydrocarbon-based fluids such as, but not limited to, crude oil, oil-based drilling fluids, produced hydrocarbons, diesel, xylenes, and aromatics.

The block copolymer proppant coating can have a melting temperature of 150 ℃ to 250 ℃, 150 ℃ to 240 ℃, 150 ℃ to 230 ℃, 150 ℃ to 220 ℃, 150 ℃ to 210 ℃, 170 ℃ to 250 ℃, 170 ℃ to 240 ℃, 170 ℃ to 230 ℃, 170 ℃ to 220 ℃, 170 ℃ to 210 ℃, 180 ℃ to 250 ℃, 180 ℃ to 240 ℃, 180 ℃ to 230 ℃, 180 ℃ to 220 ℃, 180 ℃ to 210 ℃, 190 ℃ to 250 ℃, 190 ℃ to 240 ℃, 190 ℃ to 230 ℃, 190 ℃ to 220 ℃, 190 ℃ to 210 ℃, 200 ℃ to 250 ℃, 200 ℃ to 240 ℃, 200 ℃ to 230 ℃, 200 ℃ to 220 ℃, or 200 ℃ to 210 ℃.

The melt flow index of the block copolymer proppant coating can be from 10g/10min (g/10min) to 50g/10min, from 10g/10min to 45g/10min, from 10g/10min to 40g/10min, from 10g/10min to 35g/10min, from 10g/10min to 30g/10min, from 10g/10min to 25g/10min, from 10g/10min to 20g/10min, from 10g/10min to 15g/10min, from 15g/10min to 50g/10min, from 15g/10min to 45g/10min, from 15g/10min to 40g/10min, from 15g/10min to 35g/10min, from 15g/10min to 30g/10min, from 15g/10min to 25g/10min, from 15g/10min to 20g/10min, 20g/10min to 50g/10min, 20g/10min to 45g/10min, 20g/10min to 40g/10min, 20g/10min to 35g/10min, 20g/10min to 30g/10min, 20g/10min to 25g/10min, 25g/10min to 50g/10min, 25g/10min to 45g/10min, 25g/10min to 40g/10min, 25g/10min to 35g/10min, 25g/10min to 30g/10min, 30g/10min to 50g/10min, 30g/10min to 45g/10min, 30g/10min to 40g/10min, 30g/10min to 35g/10min, 35g/10min to 50g/10min, 35g/10min to 45g/10min, 35g/10min to 40g/10min, 40g/10min to 50g/10min, 40g/10min to 45g/10min, 40g/10min, or 22g/10min, as measured at 230 ℃ according to ASTM D1238.

Each coated proppant can comprise 0.5 wt% to 15 wt%, 0.5 wt% to 12 wt%, 0.5 wt% to 10 wt%, 0.5 wt% to 8 wt%, 0.5 wt% to 5 wt%, 0.5 wt% to 3 wt%, 0.5 wt% to 2 wt%, 0.5 wt% to 1 wt%, 1 wt% to 15 wt%, 1 wt% to 12 wt%, 1 wt% to 10 wt%, 1 wt% to 8 wt%, 1 wt% to 5 wt%, 1 wt% to 3 wt%, 1 wt% to 2 wt%, 2 wt% to 15 wt%, 2 wt% to 12 wt%, 2 wt% to 10 wt%, 2 wt% to 8 wt%, 2 wt% to 5 wt%, 2 wt% to 3 wt%, 3 wt% to 15 wt%, 3 wt% to 12 wt%, 3 wt% to 10 wt%, 3 wt% to 8 wt%, 3 wt% to 5 wt%, 3 wt% to 3 wt%, 3 wt% to 15 wt%, 3 wt% to 12 wt%, 3 wt% to 10 wt%, 3 wt% to 8 wt%, 3 wt% to 3 wt%, or 3 wt% to 3 wt% of the composition, 3 to 5 wt%, 5 to 15 wt%, 5 to 12 wt%, 5 to 10 wt%, 5 to 8 wt%, 8 to 15 wt%, 8 to 12 wt%, 8 to 10 wt%, 10 to 15 wt%, 10 to 12 wt%, or 12 to 15 wt% of a block copolymer proppant coating, as calculated by weight of the proppant particle.

Fig. 1 schematically depicts two states of proppant particle 100. On the left, proppant particle 100 is depicted in a first, uncoated state. Next, on the right, coated proppant is depicted with proppant particle 100 in a second coated state. In the second state, the proppant particle 100 has undergone a coating step 200 of coating with a block copolymer proppant coating 110, thereby forming a coated proppant.

The proppant particles may be selected from any material suitable for use in hydraulic fracturing applications. As previously described, proppants are proppant particles used in hydraulic fracturing fluids to maintain and hold open subterranean fractures during or after subterranean treatments. In some embodiments, the proppant particles may include particles of materials such as oxides, silicates, sand, ceramics, resins, epoxies, plastics, minerals, glass, or combinations thereof. For example, the proppant particles may include graded sand, treated sand, ceramic proppant, sand,Plastic proppant, or other materials. The proppant particles may comprise bauxite, sintered bauxite, Ti⁴⁺Particles of/polymer composite material wherein the superscript "4 +" represents the oxidation state of titanium, titanium nitride (TiN) or titanium carbide. The proppant particles may comprise glass particles or glass beads. Embodiments of the present disclosure may utilize at least one proppant particle and in embodiments where more than one proppant particle is used, the proppant particle may contain two or more different materials or a mixture of three or more different materials.

The material of the proppant particles may be selected based on the particular application and desired characteristics (e.g., depth of the subterranean formation in which the proppant particles will be used), such as proppant particles that are required to have greater mechanical strength at greater lithostatic pressures. For example, ceramic proppant materials exhibit greater strength, heat resistance, and conductivity than sand. In addition, the ceramic proppant material has a more uniform size and shape than sand.

The proppant particles can include various sizes or shapes. In some embodiments, one or more proppant particles can have a size of 8 mesh to 200 mesh (from 74 micrometers (μm) to 2.36 millimeters (mm) in diameter). In some embodiments, the proppant particle may have 8 mesh to 16 mesh (diameter 2380 μm to 1180 μm), 16 mesh to 30 mesh (diameter 600 μm to 1180 μm), 20 mesh to 40 mesh (diameter 420 μm to 840 μm), 30 mesh to 50 mesh (diameter 300 μm to 600 μm), 40 mesh to 70 mesh (diameter 212 μm to 420 μm), or 70 mesh to 140 mesh (diameter 106 μm to 212 μm). The sphericity and roundness of the proppant particles may also vary based on the desired application.

In some embodiments, the proppant particle can have a rough surface texture that can increase the adhesion of the block copolymer proppant coating to the proppant particle. The surface of the proppant particles can be roughened to increase the surface area of the proppant particles by any suitable physical or chemical method, including, for example, using a suitable etchant. In some embodiments, the proppant particles may have a surface that provides the desired adhesion of the block copolymer proppant coating to the proppant particles or may have been sufficiently rough without the need for chemical or physical roughening. In particular, ball milling the proppant particles can provide relatively more rounded particles as well as particles with increased surface roughness.

The term "rough" refers to a surface that has at least one deviation, such as a depression or a protrusion, from the normalized plane of the surface. The surface may be uneven and irregular and may have one or more defects such as pits, bumps, or bumps or other surface defects. The rough surface may have an arithmetic average roughness (R) of greater than or equal to 1 nanometer (nm) (1nm ═ 0.001 μm)_a). R is to be_aDefined as the arithmetic mean of the difference between the local surface height and the mean surface height and which can be described by equation 1, it is envisaged to make n measurements:

in equation 1, each y_iThe amount of deviation (meaning the depth or height of the depression or protrusion, respectively) from the normalized plane of the surface for the absolute value of the ith of the n measurements. Thus, R_aIs the arithmetic mean of the absolute values of n measurements of the deviation y from the normalized plane of the surface. In some embodiments, the surface of the proppant particle can have an R of greater than or equal to 2nm (0.002 μm), or greater than or equal to 10nm (0.01 μm), or greater than or equal to 50nm (0.05 μm), or greater than or equal to 100nm (0.1 μm), or greater than or equal to 1 μm_a。

The block copolymer proppant coating can also comprise a tracer material. Suitable tracer materials may include, but are not limited to, ionic contrast agents, such as thorium dioxide (ThO)₂) Barium sulfate (BaSO)₄) Diatrizoate, metrizoate, iophthalate, and iodixanoate; and non-ionic contrast agents such as iopamidol, iohexol, ioxilan, iopromide, iodixanol and ioversol. Further, the tracer material can be present at 0.001 wt% to 5.0 wt%, 0.001 wt% to 3 wt%, 0.001 wt% to 1 wt%, 0.001 wt% to 0.5 wt%, 0.001 wt% to 0.1 wt%, 0.005 wt%, or a combination thereofFrom weight% to 5.0 weight%, from 0.005 weight% to 3 weight%, from 0.005 weight% to 1 weight%, from 0.005 weight% to 0.5 weight%, from 0.005 weight% to 0.1 weight%, from 0.01 weight% to 5.0 weight%, from 0.01 weight% to 3 weight%, from 0.01 weight% to 1 weight%, from 0.01 weight% to 0.5 weight%, from 0.5 weight% to 5.0 weight%, from 0.5 weight% to 3 weight%, from 0.5 weight% to 1 weight%, from 1 weight% to 5.0 weight%, from 1 weight% to 3 weight%, or from 3 weight% to 5 weight% as calculated on the weight of the block copolymer composition.

In some embodiments, the block copolymer proppant coating further comprises a lubricant to reduce friction on the block copolymer proppant coating. The lubricant may include at least one of calcium stearate or silicone oil. The block copolymer proppant coating can comprise 0.01 wt% to 8 wt%, 0.01 wt% to 3.75 wt%, 0.01 wt% to 1.75 wt%, 0.25 wt% to 8 wt%, 0.25 wt% to 3.75 wt%, 0.25 wt% to 1.75 wt%, 0.75 wt% to 8 wt%, 0.75 wt% to 3.75 wt%, or 0.75 wt% to 1.75 wt% of a lubricant, as calculated by weight of the block copolymer composition.

The block copolymer proppant coating may also comprise an accelerator. The promoter may include at least one of hydrochloric acid, lewis acids, boron trifluoride etherate, zinc or manganese ions, acetic acid, carboxylic acids, sodium hydroxide, other bases, or salts such as zinc acetate. The block copolymer proppant coating can comprise 1 to 70 weight percent, 1 to 45 weight percent, 1 to 20 weight percent, 5 to 70 weight percent, 5 to 45 weight percent, 5 to 12 weight percent, 12 to 70 weight percent, 12 to 45 weight percent, 12 to 20 weight percent accelerator, as calculated by weight of the proppant particle.

The block copolymer proppant coating can also comprise a filler material. The filler material can increase the mechanical strength of the block copolymer proppant coating and provide resistance to chemicals used in hydraulic fracturing fluids. The filler material may include nanoreinforcement materials of various shapes, such as, but not limited to, spheres, cylinders, cubes, pyramids, cones, triangular prisms, and tetrahedrons. The filler material may include at least one of silica, alumina, mica, graphene, vanadium pentoxide, zinc oxide, calcium carbonate, zirconia, and nanoreinforcement. The nanoreinforcement material may include at least one of carbon nanotubes, nanosilica, nanoclay, nanographene, boron nitride nanotubes, nano vanadium pentoxide, nano zinc oxide, nano calcium carbonate, and nano zirconium oxide.

In some embodiments, the block copolymer proppant coating may be fully cured or may be partially cured. This provides irregularly sized and shaped proppant particles with greater crush strength and electrical conductivity. In particular, in certain embodiments, the block copolymer proppant coating may be partially crosslinked prior to introduction into the wellbore and subterranean formation and fully crosslinked by completing crosslinking as downhole temperature is lowered after introduction into the wellbore and subterranean formation. By completing the crosslinking of the block copolymer proppant coating in the wellbore and subterranean formation, the block copolymer proppant coating of the various coated proppants can crosslink together and form crosslinked multi-layered proppant bridges within the fracture. Such crosslinked, multi-layered proppant bridges increase the crush strength of the proppant as a whole, increase the width of the propped fracture, and ensure a higher fluid conductivity through the fracture than can be achieved with a fully cured coated proppant alone.

Referring again to fig. 1, in one or more embodiments, proppant particles 100 can be coated with a block copolymer proppant coating 110 during the coating step 200 to produce, form, or generate a coated proppant. In some embodiments, the block copolymer proppant coating 110 can be a surface layer that coats the proppant particle 100. Such a surface layer may cover at least a portion of the surface of proppant particle 100. The block copolymer proppant coating 110 can cover the entire surface of the proppant particle 100 (as shown), or alternatively, can only partially surround the proppant particle 100 (not shown), leaving at least a portion of the surface of the proppant particle 100 uncoated or otherwise exposed. Also not shown, the block copolymer proppant coating 110 can be the outermost coating of the proppant particle 100, with one or more other intermediate coatings located between the block copolymer proppant coating 110 and the proppant particle 100. This means that block copolymer proppant coating 110 is in indirect contact with proppant particle 100, rather than in direct contact with proppant particle 100, as shown.

The percent crush is the percentage of proppant that will be crushed at a given pressure. A smaller crush percentage is desirable because less coated proppant may be crushed under downhole conditions, where the pressure may be greater than 20 pounds per square inch (psi), 200psi, 500psi, 1000psi, 2000psi, 3000psi, 5000psi, 7000psi, or 10000 psi. The coated proppants of the present disclosure may have a crush percentage at 6000psi of less than 50%, less than 30%, less than 20%, less than 15%, less than 12%, less than 10%, less than 8%, less than 7%, less than 5%, less than 3%, less than 2%, or 9.7%. The coated proppants of the present disclosure may have a percent crush of less than 70%, less than 50%, less than 40%, less than 35%, less than 30%, less than 25%, less than 20%, less than 15%, less than 10%, or 24.8% at 8000 psi.

Compressive strength is the resistance of a material to fracture under compression. A material with a higher compressive strength suffers less cracking at a given pressure than a material with a lower compressive strength. Higher compressive strength is desirable because the block copolymer proppant coating is less likely to fracture under downhole conditions, where the pressure may be greater than 20psi, 200psi, 500psi, 1000psi, 2000psi, 3000psi, 5000psi, 7000psi, or 10000 psi. The compressive strength of the block copolymer proppant coating of the present disclosure can range in dew pressure from 3500psi to 6000psi, 3500psi to 5500psi, 3500psi to 5200psi, 3500psi to 5000psi, 3500psi to 4700psi, 3500psi to 4500psi, 3500psi to 4100psi, 4000psi to 6000psi, 4000psi to 5500psi, 4000psi to 5200psi, 4000psi to 5000psi, 4000psi to 4700psi, 4000psi to 4500psi, 4500psi to 6000psi, 4500psi to 5500psi, 4500psi to 5200psi, 4500psi to 5000psi, 4500psi to 4700psi, 4700psi to 6000psi, 4700psi to 5500, 4700psi to 5000psi, 5000 to 6000psi, 5500, 5000psi to 5500psi, 5200 to 5200, or 4000 to 5200psi, meaning that the block copolymer proppant coating will not break before it exceeds its compressive strength.

Tensile strength is the resistance of a material to fracture under tension. A material with greater tensile strength suffers less breakage at a given tension than a material with less tensile strength. The tensile strength of the block copolymer proppant coating of the present disclosure can be 1000psi to 5000psi, 1000psi to 4500psi, 1000psi to 4000psi, 1000psi to 3500psi, 1000psi to 3000psi, 1000psi to 2000psi, 1000psi to 1500psi, 2000psi to 5000psi, 2000psi to 4500psi, 2000psi to 4000psi, 2000psi to 3500psi, 2000psi to 3000psi, 3000psi to 5000psi, 3000psi to 4500psi, 3000psi to 4000psi, 3000psi to 3500psi, 3500psi to 5000psi, 3500psi to 4500psi, 3500psi to 4000psi, 4000psi to 5000psi, 4000psi to 4500psi, or 4500 to 5000psi, meaning that the block copolymer proppant coating does not break before its tensile strength is exceeded.

The modulus of elasticity measures the resistance of a material to elastic or non-permanent deformation when a stress is applied to the material. The elastic modulus of an object is defined as the slope of its stress-strain curve in the elastically deformed region. Harder materials will have a greater modulus of elasticity. The equation for the modulus of elasticity has the following general form:

where stress is the force causing the deformation divided by the area of applied force and strain is the ratio of the change in a certain parameter caused by the deformation to the original value of that parameter. The elastic modulus of the block copolymer proppant coating of the present disclosure can be 1.5 x 10⁶psi to 2.5X 10⁶psi、1.5×10⁶psi to 2.0 x 10⁶psi、1.75×10⁶psi to 2.5X 10⁶psi、1.75×10⁶psi to 2.0 x 10⁶psi、1.75×10⁶psi to 1.95X 10⁶psi、1.75×10⁶psi to 1.9X 10⁶psi、1.75×10⁶psi to 1.85X 10⁶psi、1.85×10⁶psi to 2.5X 10⁶psi、1.85×10⁶psi to 2.0 x 10⁶psi、1.85×10⁶psi to 1.95X 10⁶psi、1.85×10⁶psi to 1.9X 10⁶psi、1.9×10⁶psi to 2.5X 10⁶psi、1.9×10⁶psi to 2.0 x 10⁶psi, or 1.9X 10⁶psi to 1.95X 10⁶psi。

Other embodiments of the present disclosure relate to methods for producing coated proppants. The method may include coating proppant particulates with a block copolymer proppant coating to produce a coated proppant having a block copolymer proppant coating. The block copolymer proppant coating is a block copolymer composition having at least one copolymer backbone. Each copolymer backbone comprises at least two hard segments and a soft segment disposed between the at least two hard segments.

In some embodiments, the method may further comprise forming a block copolymer proppant coating by adding at least one anhydride group to the soft segment of the at least one copolymer backbone. The acid anhydride group may be at least one of a succinic anhydride group and a maleic anhydride group. Further, the anhydride group can be grafted to one of the secondary or tertiary carbons of the soft segment.

In one embodiment, the method may further comprise crosslinking the at least one anhydride group with a crosslinking agent prior to coating the proppant particle with the block copolymer proppant coating. In another embodiment, the method may further comprise crosslinking the at least one anhydride group with a crosslinking agent after coating the proppant particle with the block copolymer proppant coating. In some embodiments, the crosslinking agent may include at least one of hexamethylenetetramine, paraformaldehyde, oxazolidine, melamine resin, aldehyde donor, resole polymer, and aminosilane crosslinking agent. In some embodiments, the crosslinking agent is an amine-containing crosslinking agent. The amine-containing crosslinker may be an aminosilane crosslinker. The aminosilane may include at least one of 3- (2-aminoethylaminopropyl) trimethoxysilane and 3-aminopropyltriethoxysilane. The block copolymer proppant coating can be fully crosslinked prior to introducing the coated proppant into the wellbore. In yet another embodiment, the block copolymer proppant coating can be partially cured and partially crosslinked when the coated proppant is introduced into the wellbore. The block copolymer proppant coating can be partially crosslinked by heating the coated proppant until the block copolymer proppant coating is free of visible liquid crosslinking agent. The amount of crosslinking can be determined by measuring the enthalpy of the crosslinking reaction via infrared spectroscopy or by Differential Scanning Calorimetry (DSC). Chemical methods can also be used to determine the density of the crosslinked network by, for example, testing the swellability of the block copolymer proppant coating in various solvents. In addition, the amount of crosslinking can be measured by testing the mechanical properties of the block copolymer proppant coating. For example, the amount of crosslinking can be determined using tensile testing, shore hardness testing, or Dynamic Mechanical Analysis (DMA).

Coating the proppant particle with a block copolymer proppant coating can include coating the proppant particle with 0.5 wt% to 10 wt% of the block copolymer proppant coating as calculated by weight of the proppant particle. Coating a proppant particle with a block copolymer proppant coating can include coating the proppant particle with 0.5 wt% to 15 wt%, 0.5 wt% to 12 wt%, 0.5 wt% to 8 wt%, 0.5 wt% to 5 wt%, 0.5 wt% to 3 wt%, 0.5 wt% to 2 wt%, 0.5 wt% to 1 wt%, 1 wt% to 15 wt%, 1 wt% to 12 wt%, 1 wt% to 10 wt%, 1 wt% to 8 wt%, 1 wt% to 5 wt%, 1 wt% to 3 wt%, 1 wt% to 2 wt%, 2 wt% to 15 wt%, 2 wt% to 12 wt%, 2 wt% to 10 wt%, 2 wt% to 8 wt%, 2 wt% to 5 wt%, 2 wt% to 3 wt%, 3 wt% to 15 wt%, 3 wt% to 12 wt%, as calculated based on the weight of the proppant particle, 3 to 10 wt%, 3 to 8 wt%, 3 to 5 wt%, 5 to 15 wt%, 5 to 12 wt%, 5 to 10 wt%, 5 to 8 wt%, 8 to 15 wt%, 8 to 12 wt%, 8 to 10 wt%, 10 to 15 wt%, 10 to 12 wt%, or 12 to 15 wt% of the block copolymer proppant coating coats the proppant particle.

The method may further comprise coating the proppant with a coupling agent. In some embodiments, the method further comprises using a lubricant or accelerator. In other embodiments, the method comprises coating the proppant particle with a top coat. The top coat may be a cover layer added to obtain additional properties or characteristics. As non-limiting examples, additional coatings may be used in conjunction with breakers or may contain breakers. As used throughout this disclosure, "breakers" refer to compounds that may damage or degrade a coating after a fracturing operation to prevent damage to a subterranean formation. In some embodiments, the breaker may be an oxidant or an enzyme breaker. The breaker may be any suitable material capable of degrading the coating material.

The method may further include heating the proppant particles to 100 ℃ to 210 ℃, mixing the proppant particles and the block copolymer proppant coating to form a mixture, cooling the mixture, and adding an amine-containing crosslinking agent to the mixture after cooling. In a method where the block copolymer composition comprises an SEBS block copolymer, the method can further comprise heating the proppant particle to 100 ℃ to 210 ℃, 70 ℃ to 150 ℃, 70 ℃ to 130 ℃, 70 ℃ to 120 ℃, 70 ℃ to 110 ℃, 70 ℃ to 100 ℃, 80 ℃ to 150 ℃, 80 ℃ to 130 ℃, 80 ℃ to 120 ℃, 80 ℃ to 110 ℃, 80 ℃ to 100 ℃, 90 ℃ to 150 ℃, 90 ℃ to 130 ℃, 90 ℃ to 120 ℃, 90 ℃ to 110 ℃, 90 ℃ to 100 ℃, 100 ℃ to 150 ℃, 100 ℃ to 130 ℃, 100 ℃ to 120 ℃, or 100 ℃ to 110 ℃. In a method in which the block copolymer composition comprises a PEBA block copolymer, the method can further comprise heating the proppant particle to 100 ℃ to 210 ℃, 150 ℃ to 300 ℃, 150 ℃ to 230 ℃, 150 ℃ to 210 ℃, 150 ℃ to 200 ℃, 150 ℃ to 180 ℃, 170 ℃ to 300 ℃, 170 ℃ to 230 ℃, 170 ℃ to 210 ℃, 170 ℃ to 200 ℃, 170 ℃ to 180 ℃, 180 ℃ to 300 ℃, 180 ℃ to 230 ℃, 180 ℃ to 210 ℃, 180 ℃ to 200 ℃, 200 ℃ to 300 ℃, 200 ℃ to 230 ℃, 200 ℃ to 210 ℃, 210 ℃ to 300 ℃, or 210 ℃ to 250 ℃. Heating may comprise calcination by any suitable process, such as, for example, by forced hot air heating, convection, friction, conduction, combustion, exothermic reactions, microwave heating, or infrared radiation.

In some embodiments, the method may further comprise roughening the proppant particles prior to the coating step. As previously described, the proppant particles may be chemically or physically roughened.

In some embodiments, the coating step may include contacting the proppant particles with the mixture in a fluidized bed process. In some embodiments, the coating step may comprise a stationary, bubbling, circulating, or vibrating fluidized bed process. In some embodiments, the coating step may include spraying or saturating the proppant particles with the mixture. In some embodiments, the coating step may include tumbling or agitating the coated proppant to prevent agglomeration or caking. The coating step may include adding another compound, such as a solvent, initiator, adhesion promoter, or additive, to the mixture to form a block copolymer proppant coating. In some embodiments, the coating process may be performed using emulsion coating techniques. In some embodiments, the adhesion promoter may comprise a silane (e.g., an aminosilane) or a silane-containing monomer. In some embodiments, the coated proppant particles may not require an adhesion promoter.

Hydraulic fracturing fluids and methods for increasing the rate of hydrocarbon production from a subterranean formation are also disclosed. Hydraulic fracturing fluids may be used to extend fractures within a subterranean formation and further open the fractures. The hydraulic fracturing fluid may comprise water, a clay-based component, and a coated proppant as disclosed in the present disclosure. The clay-based component may comprise one or more components selected from the group consisting of: lime (CaO), CaCO₃Bentonite, montmorillonite clay, barium sulfate (barite), hematite (Fe)₂O₃) Mullite (3 Al)₂O₃·2SiO₂Or 2Al₂O₃·SiO₂) Kaolin (Al)₂Si₂O₅(OH)₄Or kaolinite), oxidationAluminum (Al)₂O₃Or alumina), silicon carbide, tungsten carbide, or combinations thereof. The coated proppant in the hydraulic fracturing fluid can help treat the subterranean fracture, prop open the fracture and keep the fracture open. The method may include producing a first rate of production of hydrocarbons from a subterranean formation; introducing a hydraulic fracturing fluid comprising the coated proppant into a subterranean formation; and increasing hydrocarbon production from the subterranean formation by producing a second rate of hydrocarbon production from the subterranean formation, wherein the second rate of hydrocarbon production is greater than the first rate of hydrocarbon production.

The hydraulic fracturing fluid in the subterranean fracture may comprise a coated proppant suspended in the hydraulic fracturing fluid. In some embodiments, the coated proppant may be distributed throughout the hydraulic fracturing fluid. The coated proppant may not aggregate or otherwise coalesce within the subterranean formation due in part to the wettability characteristics of the block copolymer proppant coating. The hydraulic fracturing fluid may be pumped into the subterranean formation or may otherwise be in contact with the subterranean formation.

Embodiments of a method of treating a subterranean formation may include propagating at least one subterranean fracture in the subterranean formation to treat the subterranean formation. In some embodiments, the subterranean formation may be a rock or shale subterranean formation. In some embodiments, contacting of the subterranean formation may comprise drilling into the subterranean formation and subsequently injecting a hydraulic fracturing fluid into at least one subterranean fracture in the subterranean formation. In some embodiments, the hydraulic fracturing fluid may be pressurized prior to injecting the hydraulic fracturing fluid into a subterranean fracture in the subterranean formation.

Examples

The following examples illustrate features of the present disclosure, but are not intended to limit the scope of the present disclosure.

In this study, Frac grade sand was coated with two Maleic Anhydride (MA) grafted SEBS copolymers from Kraton Corporation and then crosslinked with 3-aminopropyltriethoxysilane. SEBS block copolymer can be used as Kraton^TMFG 1901 and Kraton^TMFG 1924 is commercially available from Kraton Corporation and its properties are listed in Table 1. These SEBS block copolymersThe polymer contained polystyrene as hard segment endblocks, ethylene/butylene copolymer as soft segments, and had been grafted with about 2 wt% maleic anhydride. Catalytic hydrogenation of maleic anhydride produces succinic anhydride.

Table 1: block copolymer characteristics

The sum of the weight percentages of the monomer 1 and the monomer 2 is 70 wt%

The sum of the weight percentages of the monomer 1 and the monomer 2 is 87 wt%

Measured according to ASTM D412.

A batch of 165 grams Unifrac 20/40 sand was mixed with 5 grams (3 wt%) FG 1924. Another batch of Unifrac 20/40 sand was mixed with FG 1901. Both batches were hot rolled in an oven at 220 ℃ F. for 18 hours. The hot rolled batch was screened through an 8 mesh screen and the weight of particles retained by the screen and passing through the screen was measured. Thermogravimetric analysis (TGA) was performed on the isolated sand samples to estimate the amount of elastomeric coating. The results are shown in table 2.

Table 2:

the results in table 2 show that the comparative example containing FG 1924 was unevenly coated on the sand. This is shown by a larger amount of trapped sample containing a larger amount of elastomer and a smaller amount of elastomer on the passing sample. Next, 0.2 grams of aminopropylaminoethyltrimethoxysilane was added dropwise with shaking to 80 grams of the FG 1901 coated sand control passed through an 8 mesh screen. The sample was then hot rolled at 200 ° f for 4 hours. The sand coated with the crosslinked block copolymer, for example the sand coated with the inventive example FG 1901+ crosslinker shown in table 3, had a significantly different visual appearance, reflecting a higher transparency and a smoother surface than the uncoated sand.

Crush strength tests were performed on all sand samples, including the uncoated control sample, the coated but uncrosslinked sample containing both elastomers, and the coated crosslinked sample containing FG 1901, at pressures of 6000psi and 8000 psi. The weight% of fines from the crushed sand samples was measured by passing the crushed samples through a 40 mesh screen. The results are shown in tables 3 and 4.

Table 3: results of crush studies at 6000psi pressure.

Table 4: results of crush studies at 8000psi pressure.

The results clearly show that the cross-linked block copolymer significantly reduced the amount of fines, indicating that the cross-linked block copolymer can be used to coat proppants, including sand, and produce coated proppants with crush strength capable of withstanding crush pressures of 6000psi and 8000 psi.

The coated sand samples were also tested for the possibility that the coating could dissolve or swell in hydrocarbon solvents when inside the fracture. The coated samples were soaked in xylene at room temperature for 4 hours. Excess solvent was poured in and the sample was quickly wiped dry with a paper towel and weighed. The results are shown in table 5.

TABLE 5

The results indicate that the block copolymer proppant coating is insoluble in xylene (or swells greater than 10%).

It is noted that one or more of the following claims utilize the term "where" or "where" as transitional phrases. For the purposes of defining the technology of this invention, it is noted that this term is introduced in the claims as an open transition phrase used to introduce a recitation of a series of features of a structure and is to be interpreted in the same manner as the more commonly used open leading term "comprising". For purposes of defining the present technology, the transitional phrase "consisting of … …" may be introduced in the claims as a closed leading term that limits the scope of the claims to the recited components or steps and any naturally occurring impurities. For purposes of defining the present technology, the transitional phrase "consisting essentially of … …" may be introduced in the claims to limit the scope of one or more claim terms to a stated element, component, material, or method step as well as any non-stated element, component, material, or method step that does not materially affect the characteristics of the claimed subject matter. The transition phrases "consisting of … …" and "consisting essentially of … …" may be construed as a subset of open transition phrases (such as "comprising" and "including"), such that any statement that uses an open phrase to introduce a list of elements, components, materials, or steps should be construed to also disclose the statement that a list of elements, components, materials, or steps uses the closed terms "consists of … …" and "consists essentially of … …". For example, a statement that a composition "comprises" components A, B and C should be interpreted as also disclosing a composition "consisting of" components A, B and C as well as a composition "consisting essentially of" components A, B and C. Any quantitative value expressed herein can be considered to encompass an open-ended embodiment consistent with the transition phrase "comprising" or "including" as well as a closed or partially closed-ended embodiment consistent with the transition phrases "consisting of … …" and "consisting essentially of … …".

As used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. The verb "comprise" and its conjugations should be interpreted as referring to elements, components or steps in a non-exclusive manner. The recited elements, components or steps may be present, utilized or combined with other elements, components or steps not expressly recited. It should be understood that any two quantitative values assigned to a property may constitute a range for that property, and all combinations of ranges formed from all of the quantitative values for a given property are contemplated in this disclosure. The subject matter of the present disclosure has been described in detail and by reference to specific embodiments. It should be understood that any detailed description of components or features of an embodiment does not necessarily imply that the components or features are essential to the specific embodiment or any other embodiments.

It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the present specification cover the modifications and variations of the various embodiments described, provided such modifications and variations are within the scope of the appended claims and their equivalents. All tests, properties and experiments were performed at room temperature and atmospheric pressure unless otherwise stated in the application.

The presently described subject matter may incorporate one or more aspects that should not be viewed as limiting the teachings of the present disclosure. A first aspect may include a method of producing a coated proppant having a block copolymer proppant coating, the method comprising: coating a proppant particle with the block copolymer proppant coating to produce a coated proppant having a block copolymer proppant coating, wherein the block copolymer proppant coating is a block copolymer composition having at least one copolymer backbone, each copolymer backbone comprising at least two hard segments, and a soft segment disposed between the at least two hard segments.

A second aspect includes a coated proppant comprising: proppant particulates comprising sand, ceramic materials, or combinations thereof; and a block copolymer proppant coating the proppant particle, wherein the block copolymer proppant coating is a block copolymer composition having at least one copolymer backbone, each copolymer backbone comprising at least two hard segments and a soft segment disposed between the at least two hard segments, wherein the copolymer backbone has at least one anhydride group grafted to the soft segment, and the anhydride groups are crosslinked by an amine-containing crosslinking agent.

A third aspect includes a method for increasing the rate of hydrocarbon production from a subterranean formation, the method comprising: producing a first rate of production of hydrocarbons from the subterranean formation; introducing a hydraulic fracturing fluid comprising a plurality of coated proppants into the subterranean formation; and increasing hydrocarbon production from the subterranean formation by producing a second rate of hydrocarbon production from the subterranean formation, wherein the second rate of hydrocarbon production is greater than the first rate of hydrocarbon production.

Another aspect includes any of the preceding aspects, further comprising forming a block copolymer proppant coating by adding at least one anhydride group to the soft segment of the at least one copolymer backbone.

Another aspect includes any of the preceding aspects, wherein the anhydride group comprises a succinic anhydride group, a maleic anhydride group, or a combination thereof.

Another aspect includes any of the preceding aspects, wherein the anhydride group is grafted to one of a secondary or tertiary carbon of the soft segment.

Another aspect includes any of the preceding aspects, further comprising crosslinking the anhydride groups with an amine-containing crosslinking agent prior to coating the proppant particles with the block copolymer proppant coating.

Another aspect includes any of the preceding aspects, further comprising crosslinking the anhydride groups with an amine-containing crosslinking agent after coating the proppant particles with the block copolymer proppant coating.

Another aspect includes any of the preceding aspects, wherein the amine-containing crosslinking agent comprises 3- (2-aminoethylaminopropyl) trimethoxysilane, 3-aminopropyltriethoxysilane, or a combination thereof.

Another aspect includes any of the preceding aspects, further comprising heating the proppant particles to 100 ℃ to 210 ℃, mixing the proppant particles and the block copolymer proppant coating to form a mixture, cooling the mixture, and adding an amine-containing crosslinking agent to the mixture after cooling.

Another aspect includes any of the preceding aspects, wherein coating the proppant particle with a block copolymer proppant coating comprises coating the proppant particle with a block copolymer proppant coating in an amount of 1 wt% to 10 wt%, calculated based on the weight of the proppant particle.

Another aspect includes any of the preceding aspects, wherein the hard segment comprises at least one aromatic moiety.

Another aspect includes any of the preceding aspects, wherein the hard segment comprises a polymerization product of at least one monomer selected from styrene, alpha-methylstyrene, a methacrylate, a polyamide, and a polyamine.

Another aspect includes any of the preceding aspects, wherein the hard segment is an end block.

Another aspect includes any of the preceding aspects, wherein the soft segment is aliphatic.

Another aspect includes any of the preceding aspects, wherein the soft segment comprises a polymerization product of one or more monomers selected from the group consisting of butene, butadiene, ethylene, tetrahydrofuran, ethylene oxide, propylene oxide, and acrylic acid.

Another aspect includes any of the preceding aspects, wherein the soft segments are unsaturated.

Another aspect includes any of the preceding aspects, wherein the block copolymer having grafted anhydride groups comprises the formula

Another aspect includes any of the preceding aspects, wherein the block copolymer comprises a styrene-ethylene-butylene-styrene (SEBS) block copolymer.

Another aspect includes any of the preceding aspects, wherein the block copolymer comprises a polyether block amide (PEBA) block copolymer.

Another aspect includes any of the preceding aspects, wherein the block copolymer has an a-B-a structure, wherein a and B are two compositionally different subunits.

Another aspect includes any of the preceding aspects, wherein the tensile strength of the block copolymer proppant coating is 3000psi to 5000 psi.

Another aspect includes any of the preceding aspects, wherein the block copolymer proppant coating further comprises a tracer material comprising thorium dioxide (ThO)₂) Barium sulfate (BaSO)₄) Diatrizoate, metrizoate, iophthalate, iodixanate, iopamidol, iohexol, ioxilan (ioxilan), iopromide, iodixanol, ioversol, or combinations thereof.

Another aspect includes any of the preceding aspects, wherein the coated proppant has a percent crush of less than 10% at 6000 psi.

Another aspect includes any of the preceding aspects, wherein the coated proppant has a percent crush of less than 25% at 8000 psi.

Another aspect includes any of the preceding aspects, wherein the block copolymer proppant coating further comprises a tracer material comprising thorium dioxide (ThO)₂) Barium sulfate ((BaSO)₄) At least one of diatrizoate, metrizoate, iophthalate, iodixanate, iopamidol, iohexol, ioxilan (ioxilan), iopromide, iodixanol, and ioversol.

Having described the subject matter of the present disclosure in detail and by reference to specific embodiments thereof, it should be noted that the various details disclosed herein are not to be taken as an indication that such details are related to elements that are essential components of the various embodiments described herein, even though specific elements are illustrated in each of the figures appended hereto. Further, it should be apparent that modifications and variations are possible without departing from the scope of the disclosure, including but not limited to the embodiments defined in the appended claims. Rather, while some aspects of the present disclosure are identified as particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.