A dual-repellent coated quartz sand proppant and method of making the same

Abstract

The present disclosure provides a kind of quartz sand proppant with double repellent coating and its preparation method, belongs to the technical field of proppant preparation.The preparation method of the quartz sand proppant with double repellent coating includes: adding nano-silicon dioxide into water, adding fluorocarbon surfactant after first stirring, obtaining water-based paint after second stirring;The water-based paint is coated on the surface of proppant particles, and the coated proppant particles are transferred to a container sprayed with fluorine-containing silane coupling agent for drying treatment, to obtain quartz sand proppant with double repellent coating.The present disclosure uses a low-cost, environmentally friendly surface modification process to form a dense, stable double repellent coating on the surface of the proppant, which maintains or improves the crush resistance of the proppant, and also reduces the impact of fracturing fluid and oil and water residues on fracture conductivity.

Description

Technical Field

[0001] This disclosure belongs to the field of proppant preparation technology, specifically relating to a quartz sand proppant with a double hydrophobic coating and its preparation method. Background Technology

[0002] In oil and gas reservoir development, the wettability of the formation surface has a significant impact on fluid displacement behavior, thus directly affecting production capacity. When the reservoir rock surface is oleophilic, production capacity is often inhibited; while in a hydrophilic state, although it is conducive to crude oil slippage on the surface, excessively high capillary pressure may also block pore channels, leading to a decrease in production. Therefore, controlling the wettability of the wellbore and proppant surfaces is of great significance for improving oil and gas recovery.

[0003] In existing technologies, wettability is typically altered through chemical treatment to promote fracturing fluid flowback and increase production. Traditional methods mainly involve first using organic solvents to remove bitumen or paraffin deposits from the formation rock surface, followed by the injection of highly hydrophilic surfactants to prevent further hydrocarbon deposition and improve fluid recovery. These surfactants help maximize fracturing fluid recovery by reducing interfacial tension. However, this type of treatment suffers from problems such as short-lasting wettability alteration and rapid surfactant deterioration. Furthermore, uneven surfactant adsorption on the proppant surface can still lead to water lock-in, affecting overall conductivity.

[0004] To improve the cleanliness and conductivity of proppant coatings, some studies have proposed coating the proppant surface with resin to reduce polymer residue in flowback fluids, decrease fine powder generation, and seal off particles generated during fracturing. Other studies have developed superhydrophobic coatings, which, either directly coating the proppant surface or used as fracturing additives, demonstrate significant advantages in fine powder control. These superhydrophobic surfaces effectively reduce gel residue damage, shorten fracturing fluid flowback time, and improve the conductivity of the proppant coating.

[0005] However, existing superhydrophobic modification methods mainly address the backflow problem of single-phase liquids (such as water or oil), and have not yet achieved synergistic optimization for two-phase oil-water flow, making it difficult to effectively reduce capillary pressure in two phases. Therefore, hydrocarbons or water are still prone to be trapped within the proppant coating, affecting overall permeability and conductivity.

[0006] Therefore, there is an urgent need for a proppant material with neutral wetting properties (and no affinity for water and oil) to fundamentally solve the problems of liquid residue and limited two-phase flow, thereby improving fracturing fluid flowback efficiency and oil and gas production capacity. Summary of the Invention

[0007] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a quartz sand proppant with a double hydrophobic coating and a method for preparing the same.

[0008] One aspect of this disclosure provides a method for preparing a quartz sand proppant with a double-hydrophobic coating, comprising: Nano-silica is added to water, and after the first stirring, a fluorocarbon surfactant is added. After the second stirring, a water-based coating is obtained. The water-based coating is applied to the surface of the proppant particles, and the coated proppant particles are transferred to a container sprayed with a fluorinated silane coupling agent for drying to obtain a quartz sand proppant with a double hydrophobic coating. Optionally, the content ratio of the nano-silica, water and fluorocarbon surfactant is 1:(25-35):(1-2).

[0009] Optionally, the particle size of the nano-silica is 7-40 nm.

[0010] Optionally, the ratio of the content of the nano-silica to the content of the fluorosilane coupling agent is 1:(1.5-2.5).

[0011] Optionally, the fluorosilane coupling agent is perfluorodecyltriethoxysilane.

[0012] Optionally, the first stirring time is 8-12 minutes.

[0013] Optionally, the second stirring time is 0.5-1.5 hours and the speed is 500-700 rpm.

[0014] Optionally, the drying process is carried out at a temperature of 75-85℃ for 0.3-1h.

[0015] In another aspect of this disclosure, a double-hydrophobic coated quartz sand proppant is provided, which is prepared by the preparation method described above.

[0016] Optionally, the surface of the quartz sand proppant has a double-hydrophobic coating; wherein the double-hydrophobic coating has a contact angle of 125-150° with oil and a contact angle of 134-156° with water.

[0017] This disclosure discloses a quartz sand proppant with a dual-hydrophobic coating and its preparation method. The preparation method includes: adding nano-silica to water, adding a fluorocarbon surfactant after a first stirring, and then stirring a second time to obtain an aqueous coating; coating the proppant particles with the aqueous coating, and transferring the coated proppant particles to a container sprayed with a fluorosilane coupling agent for drying to obtain the quartz sand proppant with the dual-hydrophobic coating. This disclosure employs a low-cost, environmentally friendly surface modification process applicable to commonly used proppant materials such as quartz sand. This process enables the formation of a dense and stable dual-hydrophobic coating on the proppant surface. The formed dual-hydrophobic coating can maintain or improve the proppant's anti-fracture performance and reduce the impact of fracturing fluid and oil-water residues on fracture conductivity. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the preparation method of the quartz sand proppant with a double-hydrophobic coating according to a specific embodiment of this disclosure. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0020] As shown in Figure 1, one aspect of this disclosure provides a method S100 for preparing a quartz sand proppant with a double-hydrophobic coating, specifically including the following steps S110~S120: S110. Add nano-silica to water, add fluorocarbon surfactant after the first stirring, and then add water-based coating after the second stirring.

[0021] In some preferred embodiments, the content ratio of nano-silica, water, and fluorocarbon surfactant is 1:(25-35):(1-2). For example, 1:30:1.5 is preferred.

[0022] In this embodiment, nano-silica is used as the main framework material, and its micro-nano structure provides surface roughness. At the same time, fluorocarbon surfactants are used to inhibit the aggregation of nano-silica, and the low surface energy of the coating is reduced by the low surface energy characteristics of its fluorine-containing groups, thereby improving the dispersibility of silica and forming a uniform coating on the proppant surface. Then, the nano-silica particles are fixed on the proppant surface by fluorosilane coupling agent treatment to form a certain roughness. The three work together to form a stable hydrophobic and oleophobic coating, thereby significantly improving the hydrophobic and oleophobic properties of the proppant.

[0023] Preferably, the nano-silica has a particle size of 7-40 nm. Nano-silica within this particle size range helps to form a denser micro-nano rough surface, which not only further improves the dihydrophobic properties of the coating, but also enhances the mechanical strength and overall stability of the coating.

[0024] In some other preferred embodiments, the first stirring time is 8-12 minutes, for example, 8 minutes, 10 minutes, 12 minutes, etc.

[0025] In some other preferred embodiments, the second stirring time is 0.5-1.5h and the speed is 500-700rpm. For example, the stirring time can preferably be 0.5h, 1h, 1.5h, etc., and the speed can preferably be 500rpm, 600rpm, 700rpm, etc.

[0026] S120. Water-based coating is applied to the surface of the proppant particles, and the coated proppant particles are transferred to a container sprayed with a fluorosilane coupling agent for drying treatment to obtain a quartz sand proppant with a double hydrophobic coating. In some preferred embodiments, the ratio of the content of nano-silica to the content of fluorosilane coupling agent is 1:(1.5-2.5), for example, 1:2 is preferred.

[0027] As a further preferred option, the fluorosilane coupling agent is perfluorodecyltriethoxysilane, which acts as a crosslinking agent and reacts with the surface of nano-silica and the support agent to form chemical bonds, thereby enhancing the adhesion and durability of the coating. At the same time, the fluorinated segments further reduce the surface energy, which helps to improve the oleophobic properties.

[0028] In other preferred embodiments, the drying temperature is 75-85°C, and the time is 0.3-1 hour. For example, the temperature can preferably be 75°C, 80°C, or 85°C, and the time can preferably be 0.3 hours, 0.5 hours, or 1 hour. In other words, after adding the fluorosilane coupling agent, the coating can be cured by low-temperature air drying. The process is simple and suitable for large-scale promotion.

[0029] In this embodiment, nano-silica is used as the main framework material, providing surface roughness through its micro-nano structure. Simultaneously, fluorocarbon surfactants are used to inhibit the aggregation of nano-silica, and the low surface energy of the coating is reduced by leveraging the low surface energy of its fluorinated groups. After treatment with a fluorosilane coupling agent, the three elements work synergistically to form a stable bihydrophobic coating, thereby significantly improving the hydrophobic and oleophobic properties of the proppant. Furthermore, the fluorosilane coupling agent enhances the adhesion between the coating and the substrate, improving the coating's durability and balancing high strength with fluid conductivity requirements.

[0030] This disclosure provides a neutral wetting proppant and its surface modification method. By modifying the proppant using a low-cost, environmentally friendly aqueous system, a proppant with dual hydrophobic properties (neither water nor oil wets) is formed. This reduces pore throat blockage in the proppant filling layer and achieves a synergistic improvement in the flow properties of the oil and water phases. In other words, the proppant obtained by this disclosure can significantly improve the oleophobic and hydrophobic properties of the proppant while maintaining or improving its mechanical properties. This improves its flowback effect, flow conductivity, and anti-fouling ability in fracturing operations, meeting the comprehensive requirements of proppant flow conductivity, flowback efficiency, and durability in actual oil production processes.

[0031] In another aspect of this disclosure, a double-hydrophobic coating quartz sand proppant is proposed, which is prepared by the preparation method described above. For details of the preparation process, please refer to the above description, which will not be repeated here.

[0032] In some preferred embodiments, the surface of the quartz sand proppant has a dual-repellent coating, meaning the proppant possesses both hydrophobic and oleophobic properties. Specifically, the contact angle of the dual-repellent coating with oil is 125-150°, and the contact angle with water is 134-156°. Furthermore, this proppant exhibits reduced breakage and increased strength.

[0033] The following will further illustrate the quartz sand proppant and its preparation method with specific examples: Example 1 The preparation method of the quartz sand proppant in this example includes the following steps: S1. Add 1 g of nano-silica to 30 g of water, stir magnetically for 10 minutes, and then add 1.5 g of fluorocarbon surfactant. Then, stir at 600 rpm for 1 hour at room temperature to prepare a water-based coating.

[0034] S2. Stir and mix the water-based coating to coat the surface of the proppant particles. Then, transfer it into a tray with 2g of perfluorodecyltriethoxysilane sprayed on the bottom layer. After spreading the sand evenly, place it in an oven and dry it in the air at 80 ℃ for 0.5h to obtain the dual-hydrophobic proppant.

[0035] Furthermore, the proppant's routine performance was evaluated according to SY / T 5108-2014, and the oil and water contact angles of the proppant were measured. The results are as follows: the breakage rate of the quartz sand proppant at 28 MPa decreased from 7.1% to 5.9%, and the strength was significantly improved. The bulk density increased from 1.47 g / cm³. 3 Reduced to 1.44 g / cm³ 3 The contact angle of oil is 150°, and the contact angle of water is 148°.

[0036] This disclosure presents a quartz sand proppant and its preparation method, which has the following advantages over the prior art: First, the proppant prepared in this disclosure exhibits excellent dual-repellent properties, which improves flowback efficiency and conductivity. This property can effectively prevent oil and water from accumulating on the fracture or proppant surface, reduce "water lock" or "oil lock" phenomena, improve fracturing fluid flowback efficiency, and ensure smooth oil and gas recovery.

[0037] Secondly, after surface treatment, the breakage rate of the proppant disclosed herein decreases from 7.1% to 5.9% under 28 MPa pressure, with significantly improved strength and enhanced anti-breakage performance, which is beneficial for maintaining effective support of the crack channel under high closure pressure.

[0038] Third, this disclosure uses water as a dispersion medium, combined with nano-silica and fluorocarbon surfactants, to achieve green preparation of the coating, avoiding the safety and environmental risks of traditional organic solvents. The process is simple and the cost is controllable.

[0039] Fourth, the double-hydrophobic coating of the proppant disclosed herein has a uniform coating effect, consistent quality, stable coating, and good compatibility. It can be adapted to proppants of various sizes and materials (such as quartz sand, ceramsite, etc.) and has good versatility.

[0040] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for preparing a quartz sand proppant with a double-hydrophobic coating, characterized in that, The preparation method includes: Nano-silica is added to water, and after the first stirring, a fluorocarbon surfactant is added. After the second stirring, a water-based coating is obtained. The water-based coating is applied to the surface of the proppant particles, and the coated proppant particles are transferred to a container sprayed with a fluorinated silane coupling agent for drying to obtain a quartz sand proppant with a double hydrophobic coating.

2. The preparation method according to claim 1, characterized in that, The content ratio of the nano-silica, water and fluorocarbon surfactant is 1:(25-35):(1-2).

3. The preparation method according to claim 1, characterized in that, The particle size of the nano-silica is 7-40 nm.

4. The preparation method according to claim 1, characterized in that, The ratio of the content of the nano-silica to the content of the fluorosilane coupling agent is 1:(1.5-2.5).

5. The preparation method according to claim 1, characterized in that, The fluorosilane coupling agent is perfluorodecyltriethoxysilane.

6. The preparation method according to claim 1, characterized in that, The first stirring time is 8-12 minutes.

7. The preparation method according to claim 1, characterized in that, The second stirring time is 0.5-1.5 hours, and the speed is 500-700 rpm.

8. The preparation method according to claim 1, characterized in that, The drying temperature is 75-85℃, and the time is 0.3-1h.

9. A quartz sand proppant with a double-hydrophobic coating, characterized in that, The quartz sand proppant with the double hydrophobic coating is prepared by the preparation method described in any one of claims 1 to 8.

10. The quartz sand proppant with a double-hydrophobic coating according to claim 9, characterized in that, The surface of the quartz sand proppant has a double hydrophobic coating; wherein the double hydrophobic coating has a contact angle of 125-150° with oil and a contact angle of 134-156° with water.

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