Preparation method of high-strength quartz sand for fracturing

Abstract

The invention discloses a preparation method of high-strength quartz sand for fracturing, the quartz sand is subjected to cleaning, dehydration, ball milling and secondary modification, the modification is divided into polymerization modification and surface modification, a modifier for polymerization modification comprises vinyltriethoxysilane, sodium stearate, a 1% sodium hydroxide solution, phenolic resin and titanate, and the modifier is a mixture of vinyl triethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate. According to the invention, the roundness, sphericity, surface smoothness, microstructure and other properties of the quartz fracturing sand are improved, so that the technical problems of lower strength and poorer crushing resistance of the quartz fracturing sand are solved.

Description

Technical Field

[0001] This invention relates to the field of quartz sand production technology, and specifically to a method for preparing high-strength fracturing quartz sand. Background Technology

[0002] With the development of the petroleum industry and the advancement of science and technology, hydraulic fracturing technology has become an important measure for increasing production in low-permeability onshore oilfields. In hydraulic fracturing, the selection of proppant is crucial, with quartz fracturing sand being a commonly used proppant. Quartz fracturing sand, due to its low price and good performance, ranks first in usage in oilfield production both domestically and internationally. From extraction to obtaining quartz fracturing sand for oilfield use, it undergoes many processing steps. Currently, many domestically produced quartz fracturing sands have low strength and poor resistance to breakage. The breakage rate of quartz sand proppant exceeds 8% under a closure pressure of 28 MPa, and this high breakage rate reduces the fracturing and production enhancement effect of quartz sand in oil and gas wells. The rapid development of hydraulic fracturing technology has led to a rapid increase in the demand for fracturing proppants, with a significant need for high-purity, high-strength quartz sand. However, current quartz fracturing sand cannot meet the requirements of oilfield applications.

[0003] This invention improves the roundness, sphericity, surface smoothness, and microstructure of quartz fracturing sand through washing, dehydration, ball milling, and secondary modification. This solves the technical problem of low strength and poor fracture resistance in quartz fracturing sand. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-strength fracturing quartz sand, so as to solve the technical problems of low strength and poor resistance to breakage of quartz fracturing sand.

[0005] To solve the above technical problems, the present invention adopts the following technical solution: 1. A method for preparing high-strength fracturing quartz sand, comprising the following steps: (1) Cleaning: The quartz sand is first washed with water using a cylindrical sand washing and screening machine. After washing, it is magnetically separated and then transferred to a scrubbing machine for acid washing. Finally, it is washed a second time to obtain cleaned quartz sand for later use. (2) Dehydration and drying: Transfer the cleaned quartz sand to a dehydration screen for dehydration treatment for 10-20 minutes, and then dry it in a dryer for 30-60 minutes at a temperature of 150-250℃. (3) Ball milling and sieving: The dried quartz sand is transferred into a wet ball mill, and additives are added for ball milling. After ball milling, it is classified and sieved to obtain quartz sand powder with a particle size in the range of 0.4-0.8 mm. (4) Primary polymerization modification: After heating the quartz sand powder to 180-250℃, spray the modifier and mix evenly. Stir at high speed for 1-2 hours at 180-250℃ to obtain primary modified quartz sand. The modifier comprises vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin, and titanate, wherein the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin, and titanate is 4-7:1-3:2-4:1-3:0.5-1.5. (5) Secondary surface modification: The temperature of the primary modified quartz sand is reduced to 120-150℃, hexadecyltrimethylammonium bromide is added and mixed, and the mixture is stirred at high speed for 2-4 hours at 120-150℃ to obtain secondary modified quartz sand. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.5; (6) Sintering: The secondary modified quartz sand is sintered at 450-500℃ for 0.5-1.5h to obtain high-strength fracturing quartz sand.

[0006] In step (1) above, the pickling is performed using a 1% hydrochloric acid solution and a 3% hydrofluoric acid solution, with a mass ratio of 1% hydrochloric acid solution to 3% hydrofluoric acid solution of 1:2.

[0007] In step (2) above, the drying time is 45-50 minutes and the drying temperature is 190-210℃.

[0008] In step (3) above, the additive added to the ball mill is triethanolamine, and the mass ratio of quartz sand, balls and triethanolamine is 1:2:0.3.

[0009] In step (4) above, the mass ratio of the quartz sand powder to the modifier is 1:3.

[0010] In step (4) above, the modifier includes vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate, and the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate is 5:2:3:2:1.

[0011] In step (4) above, the modifier is prepared by adding vinyltriethoxysilane and sodium stearate to a 1% sodium hydroxide solution and heating and mixing for 10-20 minutes at a temperature of 55-65°C. After mixing evenly, the phenolic resin and titanate are heated and stirred evenly to obtain the modifier.

[0012] In step (4) above, the stirring speed is 10-100 r / min.

[0013] In step (5) above, the mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.5.

[0014] In step (5) above, the stirring speed is 10-100 r / min.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses high-temperature stirring to act on quartz sand powder, allowing modifiers and resins to enter the cracks on the surface of the quartz sand. The organic functional groups of vinyltriethoxysilane can undergo a chemical bonding reaction with the organic resin, significantly improving the interfacial bonding strength between quartz sand and polymer in the resin-based composite material, reducing surface defects of quartz sand, and simultaneously improving tensile strength, impact toughness, and wear resistance.

[0016] 2. By adding hexadecyltrimethylammonium bromide to perform secondary surface modification of quartz sand, it can be coated on the particle surface through hydrogen bonding, thereby reducing the surface energy and improving the surface smoothness.

[0017] 3. The process of water washing-magnetic separation-acid washing-water washing is adopted to remove impurities from the quartz sand, improve the purity of the quartz sand, and make the silica content of the quartz sand reach more than 99%.

[0018] 4. The quartz sand is ball-milled to obtain uniform small particles with a particle size as small as 0.4-0.8 mm, which is beneficial for better dispersion of quartz sand powder and also for the penetration of modifier.

[0019] 5. The sintering process can remove volatile substances from the modifier, while making the coating material more compact and stronger in bonding with the quartz sand matrix, thus making the surface strength of the quartz sand more stable. Detailed Implementation

[0020] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention.

[0021] Example 1 Preparation method of high-strength fracturing quartz sand: (1) Cleaning: The quartz sand is first washed with water using a cylindrical sand washing and screening machine. After washing, it is magnetically separated and then transferred to a scrubbing machine for acid washing. Finally, it is washed a second time to obtain cleaned quartz sand for later use. Pickling is performed using a 1% hydrochloric acid solution and a 3% hydrofluoric acid solution, with a mass ratio of 1% hydrochloric acid solution to 3% hydrofluoric acid solution of 1:2. (2) Dehydration and drying: The washed quartz sand is transferred to a dehydration screen for dehydration treatment for 15 minutes, and then dried in a dryer for 45-50 minutes at a temperature of 200℃. (3) Ball milling and sieving: The dried quartz sand is transferred into a wet ball mill, and an additive is added for ball milling. The additive is triethanolamine. The mass ratio of quartz sand, balls and triethanolamine is 1:2:0.3. After ball milling, the quartz sand is classified and sieved to obtain quartz sand powder with a particle size in the range of 0.4-0.8 mm. (4) Primary polymerization modification: After heating the quartz sand powder to 220°C, spray the modifier and mix evenly. The mass ratio of quartz sand powder to modifier is 1:3. Stir at high speed for 1.5 hours at 220°C with a stirring speed of 50 r / min to obtain primary modified quartz sand. The modifier includes vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate, with the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate being 5:2:3:2:1. The modifier is prepared by adding vinyltriethoxysilane and sodium stearate to a 1% sodium hydroxide solution and heating and mixing for 15 minutes at a temperature of 55-65°C. After mixing evenly, phenolic resin and titanate are heated and stirred evenly to obtain the modifier. (5) Secondary surface modification: The temperature of the primary modified quartz sand was lowered to 135℃, and hexadecyltrimethylammonium bromide was added and mixed. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide was 1:1.5. The mixture was stirred at high speed for 3 hours at 135℃ with a stirring speed of 50 r / min to obtain secondary modified quartz sand. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.5; (6) Sintering: The modified quartz sand is sintered at 450-500℃ for 1 hour to obtain high-strength fracturing quartz sand.

[0022] Example 2 Preparation method of high-strength fracturing quartz sand: (1) Cleaning: The quartz sand is first washed with water using a cylindrical sand washing and screening machine. After washing, it is magnetically separated and then transferred to a scrubbing machine for acid washing. Finally, it is washed a second time to obtain cleaned quartz sand for later use. Pickling is performed using a 1% hydrochloric acid solution and a 3% hydrofluoric acid solution, with a mass ratio of 1% hydrochloric acid solution to 3% hydrofluoric acid solution of 1:2. (2) Dehydration and drying: The washed quartz sand is transferred to a dehydration screen for dehydration treatment for 20 minutes, and then dried in a dryer for 30 minutes at a temperature of 250°C for later use. (3) Ball milling and sieving: The dried quartz sand is transferred into a wet ball mill, and an additive is added for ball milling. The additive is triethanolamine. The mass ratio of quartz sand, balls and triethanolamine is 1:2:0.3. After ball milling, the quartz sand is classified and sieved to obtain quartz sand powder with a particle size in the range of 0.4-0.8 mm. (4) Primary polymerization modification: After heating the quartz sand powder to 250°C, spray the modifier and mix evenly. The mass ratio of the quartz sand powder to the modifier is 4. Stir at high speed for 1 hour at 250°C with a stirring speed of 100 r / min to obtain primary modified quartz sand. The modifier comprises vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate, wherein the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate is 4:1:4:3:0.5. The modifier is prepared by adding vinyltriethoxysilane and sodium stearate to a 1% sodium hydroxide solution and heating and mixing for 20 minutes at a temperature of 55-65°C. After mixing evenly, phenolic resin and titanate are heated and stirred evenly to obtain the modifier. (5) Secondary surface modification: The temperature of the primary modified quartz sand was lowered to 120℃, and hexadecyltrimethylammonium bromide was added and mixed. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide was 1:1.5. The mixture was stirred at high speed for 4 hours at 120℃ with a stirring speed of 10r / min to obtain secondary modified quartz sand. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.5; (6) Sintering: The modified quartz sand is sintered at 450-500℃ for 0.5h to obtain high-strength fracturing quartz sand.

[0023] Example 3 Preparation method of high-strength fracturing quartz sand: (1) Cleaning: The quartz sand is first washed with water using a cylindrical sand washing and screening machine. After washing, it is magnetically separated and then transferred to a scrubbing machine for acid washing. Finally, it is washed a second time to obtain cleaned quartz sand for later use. Pickling is performed using a 1% hydrochloric acid solution and a 3% hydrofluoric acid solution, with a mass ratio of 1% hydrochloric acid solution to 3% hydrofluoric acid solution of 1:2. (2) Dehydration and drying: The cleaned quartz sand is transferred to a dehydration screen for dehydration treatment for 10 minutes, and then dried in a dryer for 60 minutes at a temperature of 150°C for later use. (3) Ball milling and sieving: The dried quartz sand is transferred into a wet ball mill, and an additive is added for ball milling. The additive is triethanolamine. The mass ratio of quartz sand, balls and triethanolamine is 1:2:0.3. After ball milling, the quartz sand is classified and sieved to obtain quartz sand powder with a particle size in the range of 0.4-0.8 mm. (4) Primary polymerization modification: After heating the quartz sand powder to 180°C, spray the modifier and mix evenly. The mass ratio of the quartz sand powder to the modifier is 2. Stir at high speed for 2 hours at 180°C with a stirring speed of 10 r / min to obtain primary modified quartz sand. The modifier comprises vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate, wherein the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate is 7:3:2:1:1.5. The modifier is prepared by adding vinyltriethoxysilane and sodium stearate to a 1% sodium hydroxide solution and heating and mixing for 20 minutes at a temperature of 55-65°C. After mixing evenly, phenolic resin and titanate are heated and stirred evenly to obtain the modifier. (5) Secondary surface modification: The temperature of the primary modified quartz sand was lowered to 150℃, and hexadecyltrimethylammonium bromide was added and mixed. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide was 1:1.5. The mixture was stirred at high speed for 2 hours at 120-150℃ with a stirring speed of 100r / min to obtain secondary modified quartz sand. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.5; (6) Sintering: The modified quartz sand is sintered at 450-500℃ for 1.5h to obtain high-strength fracturing quartz sand.

[0024] Example 4 Preparation method of high-strength fracturing quartz sand: (1) Cleaning: The quartz sand is first washed with water using a cylindrical sand washing and screening machine. After washing, it is magnetically separated and then transferred to a scrubbing machine for acid washing. Finally, it is washed a second time to obtain cleaned quartz sand for later use. Pickling is performed using a 1% hydrochloric acid solution and a 3% hydrofluoric acid solution, with a mass ratio of 1% hydrochloric acid solution to 3% hydrofluoric acid solution of 1:2. (2) Dehydration and drying: The washed quartz sand is transferred to a dehydration screen for dehydration treatment for 15 minutes, and then dried in a dryer for 50 minutes at a temperature of 200°C for later use. (3) Ball milling and sieving: The dried quartz sand is transferred into a wet ball mill, and an additive is added for ball milling. The additive is triethanolamine. The mass ratio of quartz sand, balls and triethanolamine is 1:2:0.3. After ball milling, the quartz sand is classified and sieved to obtain quartz sand powder with a particle size in the range of 0.4-0.8 mm. (4) Primary polymerization modification: After heating the quartz sand powder to 200°C, spray the modifier and mix evenly. The mass ratio of the quartz sand powder to the modifier is 2.5. Stir at high speed for 1-2 hours at 200°C with a stirring speed of 50 r / min to obtain primary modified quartz sand. The modifier comprises vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate, wherein the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate is 5:3:3:1:1.5. The modifier is prepared by adding vinyltriethoxysilane and sodium stearate to a 1% sodium hydroxide solution and heating and mixing for 15 minutes at a temperature of 55-65°C. After mixing evenly, phenolic resin and titanate are heated and stirred evenly to obtain the modifier. (5) Secondary surface modification: The temperature of the primary modified quartz sand was lowered to 125℃, and hexadecyltrimethylammonium bromide was added and mixed. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide was 1:1.5. The mixture was stirred at high speed for 3.5 hours at 125℃ with a stirring speed of 50 r / min to obtain secondary modified quartz sand. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.5; (6) Sintering: The modified quartz sand is sintered at 450-500℃ for 1 hour to obtain high-strength fracturing quartz sand.

[0025] Comparative Example 1 (polymerization modification was performed without adding vinyltriethoxysilane to the modifier; the remaining steps were the same as in Example 1) (1) Cleaning: The quartz sand is first washed with water using a cylindrical sand washing and screening machine. After washing, it is magnetically separated and then transferred to a scrubbing machine for acid washing. Finally, it is washed a second time to obtain cleaned quartz sand for later use. Pickling is performed using a 1% hydrochloric acid solution and a 3% hydrofluoric acid solution, with a mass ratio of 1% hydrochloric acid solution to 3% hydrofluoric acid solution of 1:2. (2) Dehydration and drying: The washed quartz sand is transferred to a dehydration screen for dehydration treatment for 20 minutes, and then dried in a dryer for 30 minutes at a temperature of 250°C for later use. (3) Ball milling and sieving: The dried quartz sand is transferred into a wet ball mill, and an additive is added for ball milling. The additive is triethanolamine. The mass ratio of quartz sand, balls and triethanolamine is 1:2:0.3. After ball milling, the quartz sand is classified and sieved to obtain quartz sand powder with a particle size in the range of 0.4-0.8 mm. (4) Primary polymerization modification: After heating the quartz sand powder to 220°C, spray the modifier and mix evenly. The mass ratio of quartz sand powder to modifier is 1:3. Stir at high speed for 1.5 hours at 220°C with a stirring speed of 50 r / min to obtain primary modified quartz sand. The modifier comprises sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate, wherein the mass ratio of sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate is 2:3:2:1. The modifier is prepared by adding sodium stearate to a 1% sodium hydroxide solution and heating and mixing for 15 minutes at a temperature of 55-65°C. After mixing evenly, the phenolic resin and titanate are heated and stirred evenly to obtain the modifier. (4) Secondary surface modification: The modified quartz sand is heated to 120°C and mixed with hexadecyltrimethylammonium bromide. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.5. The mixture is stirred at high speed for 4 hours at 120°C with a stirring speed of 10 r / min to obtain the modified quartz sand. The mass ratio of the quartz sand to hexadecyltrimethylammonium bromide is 1:1.5; (6) Sintering: The modified quartz sand is sintered at 450-500℃ for 0.5h to obtain high-strength fracturing quartz sand.

[0026] Comparative Example 2 (Surface modification was not performed with the addition of hexadecyltrimethylammonium bromide; the remaining steps were the same as in Example 1). (1) Cleaning: The quartz sand is first washed with water using a cylindrical sand washing and screening machine. After washing, it is magnetically separated and then transferred to a scrubbing machine for acid washing. Finally, it is washed a second time to obtain cleaned quartz sand for later use. Pickling is performed using a 1% hydrochloric acid solution and a 3% hydrofluoric acid solution, with a mass ratio of 1% hydrochloric acid solution to 3% hydrofluoric acid solution of 1:2. (2) Dehydration and drying: The washed quartz sand is transferred to a dehydration screen for dehydration treatment for 15 minutes, and then dried in a dryer for 45-50 minutes at a temperature of 200℃. (3) Ball milling and sieving: The dried quartz sand is transferred into a wet ball mill, and an additive is added for ball milling. The additive is triethanolamine. The mass ratio of quartz sand, balls and triethanolamine is 1:2:0.3. After ball milling, the quartz sand is classified and sieved to obtain quartz sand powder with a particle size in the range of 0.4-0.8 mm. (4) Polymerization modification: After heating the quartz sand powder to 220°C, spray the modifier and mix evenly. The mass ratio of quartz sand powder to modifier is 1:3. Stir at high speed for 1.5 hours at 220°C with a stirring speed of 50 r / min to obtain modified quartz sand. The modifier includes vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate, with the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate being 5:2:3:2:1. The modifier is prepared by adding vinyltriethoxysilane and sodium stearate to a 1% sodium hydroxide solution and heating and mixing for 15 minutes at a temperature of 55-65°C. After mixing evenly, phenolic resin and titanate are heated and stirred evenly to obtain the modifier. (5) Sintering: The modified quartz sand is sintered at 450-500℃ for 1 hour to obtain high-strength fracturing quartz sand.

[0027] Comparative Example 3 (no ball milling, only simple crushing, the rest of the steps are the same as in Example 1) (1) Cleaning: The quartz sand is first washed with water using a cylindrical sand washing and screening machine. After washing, it is magnetically separated and then transferred to a scrubbing machine for acid washing. Finally, it is washed a second time to obtain cleaned quartz sand for later use. Pickling is performed using a 1% hydrochloric acid solution and a 3% hydrofluoric acid solution, with a mass ratio of 1% hydrochloric acid solution to 3% hydrofluoric acid solution of 1:2. (2) Dehydration and drying: The washed quartz sand is transferred to a dehydration screen for dehydration treatment for 15 minutes, and then dried in a dryer for 45-50 minutes at a temperature of 200℃. (3) Crushing and screening: The dried quartz sand is transferred into the crusher, crushed and then graded and screened to obtain granular quartz sand with a particle size in the range of 0.8-1.5 mm. (4) Primary polymerization modification: After heating the granular quartz sand to 220°C, spray the modifier and mix evenly. The mass ratio of quartz sand powder to modifier is 1:3. Stir at high speed for 1.5 hours at 220°C with a stirring speed of 50 r / min to obtain primary modified quartz sand. The modifier includes vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate, with the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate being 5:2:3:2:1. The modifier is prepared by adding vinyltriethoxysilane and sodium stearate to a 1% sodium hydroxide solution and heating and mixing for 15 minutes at a temperature of 55-65°C. After mixing evenly, phenolic resin and titanate are heated and stirred evenly to obtain the modifier. (5) Secondary surface modification: The temperature of the primary modified quartz sand was lowered to 135℃, and hexadecyltrimethylammonium bromide was added and mixed. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide was 1:1.5. The mixture was stirred at high speed for 3 hours at 135℃ with a stirring speed of 50 r / min to obtain secondary modified quartz sand. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.5; (6) Sintering: The modified quartz sand is sintered at 450-500℃ for 1 hour to obtain high-strength fracturing quartz sand.

[0028] Experimental Example 1: Take 100 particles of quartz sand modified in Examples 1-4 and Comparative Examples 1-3 respectively, and select 10 particles with a particle size of 0.6 mm using a microscope. Then, use a single particle strength tester to measure the single particle strength of the particles and calculate the average value. The average values ​​are listed in Table 1.

[0029] Table 1 Strength and breakage rate of modified quartz sand Serial Number Single particle strength 28MPa crushing rate Example 1 71N 6.2% Example 2 69N 6.0% Example 3 66N 6.7% Example 4 64N 7.0% Comparative Example 1 38N 10.9% Comparative Example 2 49N 8.6% Comparative Example 3 52N 8.8% As shown in Table 1, the high-strength fracturing quartz sand prepared by the method of the present invention can be modified to significantly improve the single particle strength of the quartz sand while reducing the breakage rate.

[0030] Experiment Example 2 High-strength fracturing quartz sand was prepared according to the method in Example 1. The strength and breakage rate of the quartz sand after sintering temperature variation were investigated. Using a microscope, 10 particles with a diameter of 0.6 mm were selected, and the strength of each particle was measured using a single-particle strength tester. The average value was calculated and listed in Table 2.

[0031] Table 2 Strength and breakage rate of different sintered modified quartz sands Sintering temperature Single particle strength 28MPa crushing rate 350℃ 47N 8.1% 400℃ 59N 7.5% 450℃ 67N 6.5% 500℃ 69N 6.8% 550℃ 64N 6.9% 600℃ 62N 6.6% As shown in Table 2, when the sintering temperature reaches 450℃, the strength of the modified quartz sand can reach more than 60N, and the breakage rate remains below 7%. As the temperature continues to rise, the strength and breakage rate remain unchanged. Considering energy-saving factors, the sintering temperature range can be controlled within 450-500℃.

Claims

1. A method for preparing high-strength fracturing quartz sand, characterized in that: Follow these steps: (1) Cleaning: The quartz sand is first washed with water using a cylindrical sand washing and screening machine. After washing, it is magnetically separated and then transferred to a scrubbing machine for acid washing. Finally, it is washed a second time to obtain cleaned quartz sand for later use. (2) Dehydration and drying: Transfer the cleaned quartz sand to a dehydration screen for dehydration treatment for 10-20 minutes, and then dry it in a dryer for 30-60 minutes at a temperature of 150-250℃. (3) Ball milling and sieving: The dried quartz sand is transferred into a wet ball mill, and additives are added for ball milling. After ball milling, it is classified and sieved to obtain quartz sand powder with a particle size in the range of 0.4-0.8 mm. (4) Primary polymerization modification: After heating the quartz sand powder to 180-250℃, spray the modifier and mix evenly. The mass ratio of the quartz sand powder to the modifier is 1:2-4. Stir at high speed for 1-2 hours at 180-250℃ to obtain primary modified quartz sand. The modifier comprises vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin, and titanate, wherein the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin, and titanate is 4-7:1-3:2-4:1-3:0.5-1.

5. (5) Secondary surface modification: The temperature of the primary modified quartz sand is reduced to 120-150℃, hexadecyltrimethylammonium bromide is added and mixed, and the mixture is stirred at high speed for 2-4 hours at 120-150℃ to obtain secondary modified quartz sand. The mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.5; (6) Sintering: The secondary modified quartz sand is sintered at 450-500℃ for 0.5-1.5h to obtain high-strength fracturing quartz sand.

2. The method for preparing high-strength fracturing quartz sand according to claim 1, characterized in that: In step (1), the pickling is performed using a 1% hydrochloric acid solution and a 3% hydrofluoric acid solution, with a mass ratio of 1% hydrochloric acid solution to 3% hydrofluoric acid solution of 1:

2.

3. The method for preparing high-strength fracturing quartz sand according to claim 1, characterized in that: In step (2), the drying time is 45-50 minutes and the drying temperature is 190-210℃.

4. The method for preparing high-strength fracturing quartz sand according to claim 1, characterized in that: In step (3), the additive added to the ball mill is triethanolamine, and the mass ratio of quartz sand, balls and triethanolamine is 1:2:0.

3.

5. The method for preparing high-strength fracturing quartz sand according to claim 1, characterized in that: In step (4), the mass ratio of the quartz sand powder to the modifier is 1:

3.

6. The method for preparing high-strength fracturing quartz sand according to claim 1, characterized in that: In step (4), the modifier includes vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate, and the mass ratio of vinyltriethoxysilane, sodium stearate, 1% sodium hydroxide solution, phenolic resin and titanate is 5:2:3:2:

1.

7. The method for preparing high-strength fracturing quartz sand according to claim 1 or 6, characterized in that: In step (4), the modifier is prepared by adding vinyltriethoxysilane and sodium stearate to a 1% sodium hydroxide solution and heating and mixing for 10-20 minutes at a temperature of 55-65°C. After mixing evenly, the phenolic resin and titanate are heated and stirred evenly to obtain the modifier.

8. The method for preparing high-strength fracturing quartz sand according to claim 1, characterized in that: In step (4), the stirring speed is 10-100 r / min.

9. The method for preparing high-strength fracturing quartz sand according to claim 1, characterized in that: In step (5), the mass ratio of the primary modified quartz sand to hexadecyltrimethylammonium bromide is 1:1.

5.

10. The method for preparing high-strength fracturing quartz sand according to claim 1, characterized in that: In step (5), the stirring speed is 10-100 r / min.