Pressure-resistant quartz sand proppant as well as preparation process and application thereof

Abstract

The invention relates to the technical field of oil and gas field exploitation, and discloses a pressure-resistant quartz sand proppant and a preparation process and application thereof, and the proppant is composed of a quartz sand base material and a multi-layer composite coating coated on the quartz sand base material. The interface grafting layer is chemically bonded with the surface of quartz sand through a silane coupling agent; a latent acid source is utilized to slowly release acid under a heating condition, the sodium silicate in-situ hydrolysis condensation polymerization rate is accurately regulated and controlled, and nano silicon dioxide is used as a nucleation point to construct a compact inorganic nano composite inner shell; the outermost layer is coated with the organic toughening shell. According to the preparation method, the reaction process of the inorganic inner shell is accurately regulated and controlled, and the interface grafting and outer layer toughening technology is combined, so that a synergistically enhanced composite structure among the coatings is formed. According to the structure, the quartz sand propping agent is endowed with extremely low compaction breakage rate and excellent long-term flow conductivity, and the fracturing operation requirements under high-temperature and high-pressure harsh conditions of deep wells, ultra-deep wells and the like can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field exploitation, and in particular to a pressure-resistant quartz sand proppant, a preparation process thereof and an application thereof. BACKGROUND

[0002] Hydraulic fracturing is one of the core technologies for current oil and gas production, and its application range has been extended from conventional oil and gas reservoirs to large-scale development of unconventional resources such as shale gas and tight oil. The implementation of this technology relies on the injection of high-pressure fluid into underground reservoirs to create artificial fractures, and the use of proppants to fill them to maintain the open state of the fractures under high closure pressure, thereby providing long-term and high-conductivity flow channels for oil and gas. The performance of the proppant, especially its structural integrity under high stress, is a key factor in determining the success of fracturing operations and the productivity of oil and gas wells.

[0003] Among various types of proppants, quartz sand has been widely used in fracturing operations due to its abundant resources and low cost. However, as a natural material, the inherent mechanical strength of quartz sand is limited, which restricts its application in deep wells, ultra-deep wells, and high-stress areas. In these high-closure-pressure application scenarios, quartz sand particles are prone to crushing at their compressive limit. The fine powder produced by crushing can migrate and block the pore throats in the proppant bed, resulting in an irreversible and rapid decline in fracture conductivity, ultimately failing to achieve the expected fracturing stimulation effect.

[0004] To solve this problem, existing technologies mainly focus on surface modification of quartz sand, among which coating is a mainstream preparation process. One common process is to coat quartz sand with organic polymers such as phenolic resin. However, this preparation process usually only forms a physical attachment between the quartz sand and the resin, with insufficient interfacial bonding strength. Under the combined action of high temperature, high pressure, and fluid shear in the well, the coating is prone to peeling off from the quartz sand substrate, and the peeling material becomes a new source of blockage, damaging the fracture conductivity.

[0005] Another technical approach is to use inorganic preparation processes, such as generating an enhanced coating on the surface of quartz sand in situ using silicates. However, existing related preparation processes have significant defects, and the reaction process is difficult to control accurately. Generally, the hydrolysis and polycondensation reaction rate of silicates is extremely fast, resulting in a loose, porous, and unevenly distributed inorganic coating with a large number of structural defects in the microstructure. This defective and brittle coating cannot effectively improve the overall compressive strength of the particles, so the proppant prepared by this process will still crush under high stress.

[0006] In summary, existing quartz sand proppants and their preparation processes have not yet economically and effectively solved the problem of quartz sand crushing in high-closure-pressure application environments. SUMMARY

[0007] The technical problem to be solved by the present application is that the conventional quartz sand proppant in the prior art has insufficient strength and is prone to breakage under high closure pressure, while high-performance ceramic proppant is too costly.

[0008] To solve the above technical problems, the present application provides a pressure-resistant quartz sand proppant, a preparation process thereof, and an application thereof.

[0009] The present application provides, in a first aspect, a pressure-resistant quartz sand proppant.

[0010] The pressure-resistant quartz sand proppant comprises, in terms of weight percentage, the following raw material components: sodium silicate: 3%-10%; nano-silicon dioxide: 0.5%-5%; latent acid source: 0.05%-1.5%; epoxy resin: 0.02%-2%; sodium hydroxide: 0.01%-2%; hexamethylenetetramine: 0.03%-3%; ammonium chloride: 0.03%-3%; silane coupling agent: 0.1%-1.5%; calcium stearate: 0.01%-1%; water-washed quartz sand: the balance.

[0011] The technical concept of the proppant is to construct a multi-layer composite structure from the inside to the outside on the surface of the quartz sand substrate through a specific process sequence. The structure comprises an interface layer chemically bonded with the quartz sand substrate, a dense inorganic nano-composite inner shell, and a tough organic toughening outer shell.

[0012] In a preferred technical solution, the latent acid source is one or more of hydrolysable esters or ammonium salts that produce acid upon thermal decomposition.

[0013] Further, the hydrolysable ester is ethyl lactate or ethyl acetate. The latent acid source slowly decomposes or hydrolyzes at a specific temperature and uniformly releases acid in a liquid phase system, thereby effectively regulating the hydrolysis and polycondensation reaction rate of sodium silicate.

[0014] In a preferred technical solution, the silane coupling agent is gamma-aminopropyl triethoxysilane. One end of the coupling agent molecule can chemically react with the hydroxyl groups on the surface of the quartz sand to form a covalent bond, and the amino functional group at the other end can react with the subsequent epoxy resin, thereby forming a chemical connection between the inorganic inner shell and the organic outer shell, improving the interfacial bonding strength of the composite coating.

[0015] The second aspect of the present application provides a preparation process of pressure-resistant quartz sand proppant.

[0016] The preparation process for preparing the aforementioned pressure-resistant quartz sand proppant comprises the following steps: S1, surface activation and interface grafting step: sodium hydroxide and silane coupling agent are applied to the surface of preheated quartz sand substrate to react and form a chemically grafted interface layer. In this step, sodium hydroxide is used to increase the number of hydroxyl groups on the surface of quartz sand and the surface energy. The silane coupling agent reacts with the hydroxyl groups on the surface of quartz sand through hydrolysis and condensation reaction of its siloxane group, fixing the coupling agent molecules on the surface of quartz sand and forming an interface layer.

[0017] S2, in-situ network construction step of inorganic nano-composite layer: precursor solution containing sodium silicate, nano-silica and latent acid source is added to the quartz sand treated in step S1, and the latent acid source is slowly reacted by heating to trigger the in-situ hydrolysis and condensation reaction of sodium silicate, converting the liquid precursor into a solid network structure, and constructing an inorganic nano-composite inner shell on the interface layer. In this step, heating promotes the uniform production of acid in the system by the latent acid source, smoothly reducing the pH value of the system. This triggers the controlled hydrolysis and condensation of sodium silicate. The pre-dispersed nano-silica particles act as nucleation points, guiding the deposition and crosslinking of generated silicic acid on their surfaces, and finally forming an inorganic network reinforced by nano-particles and having a dense structure, i.e. an inorganic nano-composite inner shell.

[0018] S3, coating and curing step of organic toughening outer layer: epoxy resin, hexamethylenetetramine and ammonium chloride are added to the quartz sand with inorganic nano-composite inner shell to coat, and then heated and cured to form an organic toughening outer shell. In this step, the epoxy resin is coated outside the inorganic nano-composite inner shell. Hexamethylenetetramine and ammonium chloride form a composite curing system, which reacts with the epoxy resin and active functional groups on the interface layer at high temperature to form a tough organic polymer outer shell. Calcium stearate acts as a processing aid to prevent particle adhesion during this process.

[0019] In a preferred process scheme, in step S1, the preheating temperature of the quartz sand substrate is 50-70°C.

[0020] In a preferred process scheme, in step S2, the temperature for in-situ hydrolysis and condensation reaction is 80-100°C.

[0021] In a preferred process scheme, in step S3, the epoxy resin, hexamethylenetetramine and ammonium chloride are added at 60-80°C for coating, and then heated to 130-160°C for curing.

[0022] In a preferred process, the precursor solution in step S2 is prepared by dispersing nanosilica in an aqueous sodium silicate solution, and then adding a latent acid source and mixing uniformly. This preparation sequence ensures that the nanosilica can serve as nucleation sites uniformly in the subsequent reaction.

[0023] The third aspect of the present application provides an application of the pressure-resistant quartz sand proppant.

[0024] The pressure-resistant quartz sand proppant of the first aspect, or the pressure-resistant quartz sand proppant prepared by the process of the second aspect, is applied in the hydraulic fracturing process for oil and gas exploitation.

[0025] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present application significantly improves the bonding strength of the composite coating and the quartz sand substrate by introducing a silane coupling agent in the preparation process and performing a preliminary activation and interfacial grafting treatment on the surface of the quartz sand. One end of the silane coupling agent forms a stable chemical bond with the hydroxyl groups on the surface of the quartz sand, and the active functional groups on the other end participate in the curing reaction network of the subsequent organic shell. Thus, a chemical connection is established between the inorganic substrate, the inorganic inner shell, and the organic outer shell. This chemical bonding effect fundamentally solves the technical problem of peeling of traditional coatings under high temperature and high pressure and fluid shear due to weak physical adsorption force, ensuring the long-term integrity of the multi-layer composite structure of the proppant.

[0026] 2. The present application achieves a more dense and uniform inorganic reinforcing layer by precisely controlling the formation process of the inorganic nanocomposite layer using a latent acid source. Under heating conditions, the latent acid source releases acid slowly and uniformly in the liquid system, effectively controlling the in situ hydrolysis and polycondensation reaction rate of sodium silicate. Meanwhile, the pre-dispersed nanosilica particles in the system serve as homogeneous nucleation sites. This process avoids defects such as loose coating structure and micro-cracks caused by rapid pH changes or rapid water loss, forming a solid network with complete structure and fewer defects, providing excellent rigid support for the proppant.

[0027] 3. The present application significantly improves the overall mechanical properties of the proppant by constructing a multi-layer synergistic reinforcing structure composed of an interfacial chemical grafting layer, an inorganic nanocomposite inner shell, and an organic toughening outer shell. The high-hardness inorganic inner shell mainly bears and resists external extrusion stress; the tough organic outer shell can effectively absorb impact energy and inhibit the propagation of surface micro-cracks to the interior; and the firm interfacial chemical bond ensures that the functional layers can synergistically act, effectively transfer and disperse the load. This rigid and tough combined composite structure design allows the external stress to be dissipated step by step, effectively reducing the overall breakage rate of the proppant particles under high closure pressure. DETAILED DESCRIPTION

[0028] The application will be further described in detail in connection with the following examples, comparative examples and test examples.

[0029] The main raw materials and reagents used in the following examples and comparative examples are as follows, and the reagents not specifically described are commercially available analytical pure or higher grade products.

[0030] γ-aminopropyltriethoxysilane: CAS No.: 919-30-2; Sodium silicate: CAS No.: 1344-09-8; Ethyl lactate: CAS No.: 97-64-3; Ammonium acetate: CAS No.: 631-61-8; Epoxy resin E-51: CAS No.: 24969-06-0; Hexamethylenetetramine: CAS No.: 100-97-0; Ammonium chloride: CAS No.: 12125-02-9; Calcium stearate: CAS No.: 1592-23-0.

[0031] Examples 1-3: Example 1: This example is used to illustrate a pressure-resistant quartz sand proppant and its preparation according to the technical scheme of the application.

[0032] The raw material formula is prepared for 1000g of finished product, and the amount of each raw material component and its weight percentage is as follows: Washed quartz sand (40-70 mesh): 870g, accounting for 87.0% of the total weight; Sodium silicate (modulus 2.5): 60g, accounting for 6.0% of the total weight; Nanosilica (particle size 30nm): 20g, accounting for 2.0% of the total weight; Latent acid source (ethyl lactate): 5g, accounting for 0.5% of the total weight; Epoxy resin (E-51): 10g, accounting for 1.0% of the total weight; Sodium hydroxide: 5g, accounting for 0.5% of the total weight; Hexamethylenetetramine: 10g, accounting for 1.0% of the total weight; Ammonium chloride: 10g, accounting for 1.0% of the total weight; Silane coupling agent (γ-aminopropyltriethoxysilane): 8g, accounting for 0.8% of the total weight; Calcium stearate: 2g, accounting for 0.2% of the total weight.

[0033] Preparation process: S1, surface activation and interface grafting step: 870 g of water-washed quartz sand was put into a mechanically stirred reaction kettle which can be heated, and the stirring was started and the temperature was raised to 60°C. 5 g of sodium hydroxide and 8 g of silane coupling agent were dissolved in 20 ml of water to prepare an interface activation solution. The activation solution was added to the reaction kettle by spraying, and the stirring was continued at 60°C for 20 minutes.

[0034] S2, in-situ network construction step of inorganic nano-composite layer: outside the reaction kettle, 20 g of nano-silicon dioxide was added to an aqueous solution containing 60 g of sodium silicate, uniformly dispersed by high shear, and then 5 g of ethyl lactate was added for mixing to prepare a precursor solution. The precursor solution was added to the quartz sand after the S1 step, and the reaction kettle was heated to 90°C, and the stirring was continued at this temperature for 60 minutes.

[0035] S3, coating and curing step of the organic toughening outer layer: after the S2 step was completed, the temperature of the reaction kettle was reduced to 70°C. The stirring was maintained, and 10 g of epoxy resin, 10 g of hexamethylene tetramine, 10 g of ammonium chloride and 2 g of calcium stearate were sequentially added to the kettle. The stirring was continued at this temperature for 10 minutes. Subsequently, the reaction kettle was rapidly heated to 150°C, and the temperature was maintained for 45 minutes for curing. After the curing was completed, the heating was stopped, and the temperature was reduced to room temperature. The product was taken out, and was sieved by a vibrating screen to obtain the final pressure-resistant quartz sand proppant.

[0036] Example 2: This example is used to illustrate the pressure-resistant quartz sand proppant and its preparation in the technical scheme of the present application, which uses different latent acid sources.

[0037] Raw material formula: The components and amounts of each raw material are exactly the same as in Example 1, and only the latent acid source is replaced from 5 g of ethyl lactate (0.5% of the total weight) to 5 g of ammonium acetate (0.5% of the total weight).

[0038] Preparation process: The preparation process steps and process parameters are exactly the same as in Example 1.

[0039] Example 3: This example is used to illustrate the pressure-resistant quartz sand proppant and its preparation in the technical scheme of the present application, which uses a higher content of reinforcing components.

[0040] Raw material formula: The components and amounts of each raw material are as follows, based on the preparation of 1000 g of finished product: Water-washed quartz sand (40-70 mesh): 780 g, accounting for 78.0% of the total weight; Sodium silicate (modulus 2.5): 90 g, accounting for 9.0% of the total weight; Nano-silicon dioxide (particle size 30nm): 40g, accounting for 4.0% of the total weight; Latent acid source (ethyl lactate): 10 g, accounting for 1.0% of the total weight; Epoxy resin (E-51): 15 g, accounting for 1.5% of the total weight; Sodium hydroxide: 10 g, accounting for 1.0% of the total weight; Hexamethylenetetramine: 20 g, accounting for 2.0% of the total weight; Ammonium chloride: 20 g, accounting for 2.0% of the total weight; Silane coupling agent (γ-aminopropyltriethoxysilane): 12g, accounting for 1.2% of the total weight; Calcium stearate: 3g, accounting for 0.3% of the total weight.

[0041] Preparation process: The preparation was carried out using substantially the same preparation process steps and process parameters as those in Example 1, wherein the heat preservation and curing time at 150° C. in step S3 was adjusted to 60 minutes.

[0042] Comparative Examples 1-4: Comparative Example 1: The sample used in this comparative example is conventional washed quartz sand without any treatment, and its specifications are the same as the quartz sand substrate used in Example 1.

[0043] Comparative Example 2: Compared to Example 1, the preparation process of this comparative example omits steps S1 and S2, thus eliminating the use of sodium hydroxide, silane coupling agent, sodium silicate, nano-silica, and latent acid source. The specific process involves preheating quartz sand and then directly adding an organic material such as epoxy resin for coating and curing. All other steps remain the same.

[0044] Comparative Example 3: Compared with Example 1, the difference is that the preparation process of this comparative example only omits step S2, so sodium silicate, nano-silicon dioxide and latent acid source are not used. The rest are the same.

[0045] Comparative Example 4: Compared with Example 1, the only difference is that the raw material formula of this comparative example does not contain a latent acid source (ethyl lactate). The rest are the same.

[0046] Test Example 1-2: Test Example 1: Proppant Pressure Crushing Rate Test Test method: To evaluate the mechanical properties of the samples prepared in the above examples and comparative examples, the pressure crushing resistance test was performed on each sample according to the Performance Test Methods for Proppants Used in Hydraulic Fracturing and Gravel Packing Operations (SY / T 5108-2014) of the People's Republic of China Oil and Natural Gas Industry Standard. The experimental steps are as follows: (1) Dry the sample in an oven at 105°C for 2 hours, and then cool to room temperature in a desiccator; (2) Accurately weigh a certain mass of the sample to be tested, which is determined according to the apparent density of the sample and the volume of the test pressure chamber; (3) Uniformly load the weighed sample between the piston and the pressure ring of the test pressure chamber; (4) Place the sample-loaded pressure chamber on the pressure testing machine, and apply a load at a loading rate of 1.4 MPa / min until the pressure reaches 52 MPa; (5) Maintain the constant closed pressure of 52 MPa for 2 minutes; (6) After the pressure holding is completed, remove the pressure, and carefully take out all the samples in the pressure chamber; (7) Place the taken-out sample on a standard sieve that meets the particle size specifications of the sample (for example, for a 40-70 mesh sample, use a 70 mesh sieve), and fully sieve to separate the fine powder generated after crushing; (8) Accurately weigh the mass of the fine powder passing through the sieve; (9) The crushing rate is calculated by the following formula: crushing rate (%) = (fine powder mass / initial total mass of the sample) x 100%.

[0047] Test results: The samples prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were tested under the same conditions, and the crushing rate results are recorded in the following table.

[0048] Table 1: Crushing rate test results of each sample under a closed pressure of 52 MPa Experimental summary: As can be seen from the test results in Table 1, the samples prepared in Examples 1, 2 and 3 all exhibit lower crushing rates compared to the samples of Comparative Examples 1 to 4, which indicates that the technical scheme of the present application can effectively improve the compressive strength of quartz sand proppants. Comparative Example 1, as a conventional quartz sand without treatment, has the highest crushing rate. Although the crushing rates of Comparative Examples 2 and 3 are reduced, they are still at a relatively high level, which shows that only organic coating or only interface grafting without a key inorganic reinforcing layer has limited structural strengthening effect.

[0049] Comparing Example 1 with Comparative Example 4, the results show that, under identical other conditions, the fragmentation rate of Comparative Example 4 is significantly higher than that of Example 1 due to the lack of a latent acid source to regulate the reaction process. This is because, in the technical solution of the present invention, the latent acid source can uniformly and slowly generate acid under heating conditions, steadily adjusting the pH value of the system, allowing the in-situ hydrolysis and polycondensation reactions of sodium silicate to proceed in a controlled manner. This controlled reaction process, combined with nano-silica as a nucleation point, jointly promotes the formation of an inorganic network inner shell with a dense structure and a small number of defects. This dense inorganic inner shell provides a solid rigid skeleton for the proppant particles, effectively resisting external pressure.

[0050] The crushing rates of Examples 1, 2, and 3 are significantly lower than those of all comparative examples, indicating that the multilayer composite structure constructed by the present invention has a synergistic enhancement effect. In this structure, the chemical bonding formed by the surface activation and interface grafting steps ensures a firm bond between the composite coating and the quartz sand substrate, and is not easily peeled off under the action of external forces. On this basis, the dense inorganic nanocomposite inner shell assumes the main compressive function, while the organic toughening shell of the outer layer can absorb impact energy and inhibit the expansion of microcracks. The layers work synergistically through a stable chemical connection to jointly enhance the overall structural stability and crushing resistance of the proppant, thereby maintaining the integrity of the particles under high closure pressure.

[0051] Test Example 2: Proppant Conductivity Test Test method: To evaluate the fluid flow capacity of the samples under simulated formation conditions, the samples were tested according to the conductivity test requirements in the Petroleum and Natural Gas Industry Standard SY / T6302-2019 "Test and Evaluation Methods for Fracturing Proppant Conductivity". The experimental steps are as follows: (1) The sample was dried in an oven at 105°C for 2 hours and then cooled to room temperature in a desiccator; (2) The sample is evenly spread in the test chamber of the conductivity tester (for example, a test chamber of API standard size) to form a sand concentration of 10 kg / m 2 The proppant sand layer; (3) Assemble the test chamber and place it in a heatable hydraulic press. Apply a closing pressure of 52 MPa while heating and maintaining the test system at 90°C. (4) Under the above temperature and pressure conditions, deoxygenated 2% KCl solution is used as the test fluid and pumped into the sand layer at a specified constant rate (e.g., 5 ml / min); (5) After the system reaches a stable state, the differential pressure sensor is used to accurately record the pressure difference before and after the fluid flows through the sand layer; (6) The conductivity is calculated according to Darcy's law, by measuring the pressure drop, fluid viscosity, flow rate and the sandpack geometry.

[0052] Test results: The samples prepared in Examples 1-3 and Comparative Examples 1-4 were tested under the same conditions, and the resulting conductivity results are recorded in the table below.

[0053] Table 2: Conductivity test results of each sample at a closure pressure of 52 MPa and 90°C Sample No. Flow conductivity (pm 2 • cm)]]> Example 1 156 Example 2 151 Example 3 178 Comparative Example 1 15 Comparative Example 2 42 Comparative Example 3 55 Comparative Example 4 89 Summary of experiments: As can be seen from the test results in Table 2, the samples prepared in Examples 1, 2, and 3 have significantly higher conductivity values than Comparative Examples 1-4. Conductivity is a key indicator of the ability of a proppant to maintain the opening of a fracture and allow fluid to pass under closure pressure. The conventional quartz sand of Comparative Example 1 is severely crushed under high temperature and high pressure, producing fine particles that block the pore channels in the sandpack, resulting in very low conductivity. Although Comparative Examples 2 and 3 have a coating, they still produce a large amount of crushing due to insufficient structural strength, and their conductivity is also at a low level.

[0054] Comparing the test results of Example 1 and Comparative Example 4 confirms the role of latent acid sources in building high-performance coatings. The sample of Example 1 has higher conductivity, and the direct reason is that it maintains a low crushing rate under test pressure. This is achieved by controlling the reaction rate of the in-situ reaction of the latent acid source with the inorganic material during preparation. This controlled reaction process builds a denser and more homogeneous inorganic nanocomposite inner shell, which gives the proppant particle excellent crush resistance, thereby maintaining the integrity of the pore structure inside the sandpack under high closure pressure, leaving an effective flow path for fluid to pass through.

[0055] The high conductivity exhibited by Examples 1, 2, and 3 is a direct manifestation of the stability of the multi-layer synergistic structure under high stress environment. In this structure, the interface grafting step ensures the stable bonding of the coating to the quartz sand substrate under high temperature and high pressure fluid shear, avoiding the formation of blocking materials due to coating peeling. The high-strength inorganic inner shell effectively resists external pressure, while the tough organic outer shell suppresses surface damage. This multi-layer structure synergistically reduces the crushing and fine powder generation of the proppant particles, ensuring that the sandpack composed of these particles has a stable and highly connected pore network, ultimately exhibiting excellent long-term conductivity.

[0056] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A pressure-resistant quartz sand proppant, characterized in that: In terms of weight percentage, the raw material components include: Sodium silicate: 3%-10%; Nano-silicon dioxide: 0.5%-5%; Latent acid source: 0.05%-1.5%; Epoxy resin: 0.02%-2%; Sodium hydroxide: 0.01%-2%; Hexamethylenetetramine: 0.03%-3%; Ammonium chloride: 0.03%-3%; Silane coupling agent: 0.1%-1.5%; Calcium stearate: 0.01%-1%; Washed quartz sand: balance.

2. A pressure-resistant quartz sand proppant according to claim 1, characterized in that: The latent acid source is one or more of hydrolyzable esters or ammonium salts that decompose to generate acid when heated.

3. The pressure-resistant quartz sand proppant according to claim 1, characterized in that: The hydrolyzable ester is ethyl lactate or ethyl acetate.

4. The pressure-resistant quartz sand proppant according to claim 1, characterized in that: The silane coupling agent is γ-aminopropyltriethoxysilane.

5. A process for preparing the pressure-resistant quartz sand proppant according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, surface activation and interface grafting step: applying sodium hydroxide and a silane coupling agent to the surface of the preheated quartz sand substrate to react and form a chemically grafted interface layer; S2, an in-situ network construction step of the inorganic nanocomposite layer: adding a precursor solution containing sodium silicate, nano-silica, and a latent acid source to the quartz sand treated in step S1, and slowly heating the latent acid source to trigger an in-situ hydrolysis and polycondensation reaction of the sodium silicate, thereby transforming the liquid precursor into a solid network structure, and constructing an inorganic nanocomposite inner shell on the interface layer; S3, coating and curing step of the organic toughened outer layer: adding epoxy resin, hexamethylenetetramine and ammonium chloride to the quartz sand formed with the inorganic nanocomposite inner shell for coating, and then heating and curing to form an organic toughened outer shell.

6. The process for preparing a pressure-resistant quartz sand proppant according to claim 5, characterized in that: In the step S1, the preheating temperature of the quartz sand substrate is 50°C-70°C.

7. The process for preparing a pressure-resistant quartz sand proppant according to claim 5, characterized in that: In step S2, the temperature for the in-situ hydrolysis and polycondensation reaction is 80°C-100°C.

8. The process for preparing a pressure-resistant quartz sand proppant according to claim 5, characterized in that: In the step S3, epoxy resin, hexamethylenetetramine and ammonium chloride are added at 60° C.-80° C. for coating, and then the temperature is raised to 130° C.-160° C. for curing.

9. The process for preparing a pressure-resistant quartz sand proppant according to claim 5, characterized in that: The precursor solution in step S2 is prepared by dispersing nano-silica in a sodium silicate aqueous solution, and then adding the latent acid source and mixing them uniformly.

10. Use of the pressure-resistant quartz sand proppant according to any one of claims 1 to 4, characterized in that: It is used in the hydraulic fracturing process for oil and gas extraction.

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