Polymer dry powder fracturing fluid and preparation method thereof

Abstract

The invention discloses a polymer dry powder fracturing fluid and a preparation method thereof, and belongs to the technical field of oil and gas field yield increase. The preparation method comprises the following steps: adding polymer dry powder, modified fluorocarbon, polyvinylpyrrolidone and beta-cyclodextrin into a mixer, stirring and mixing for 20-40 minutes, then sieving with a 120-180-mesh sieve, and packaging to obtain the polymer dry powder fracturing fluid. Nano silicon dioxide is modified and then subjected to a copolymerization reaction with acrylic acid, acrylamide and 2-acrylamido-2-methylpropanesulfonic acid, and nano particles with rigidity and extremely high thermal stability are chemically bonded to a polymer molecular chain, so that thermal oxidative degradation and shear fracture of the molecular chain at high temperature can be effectively inhibited; the shear resistance and the high temperature resistance of the fracturing fluid are improved; the fluorocarbon chain segment in the modified fluorocarbon can significantly reduce the interfacial tension between the fracturing fluid and the inner wall of the pipeline and the formation fluid, and the drag reduction capability of the fracturing fluid is enhanced in cooperation with the uniform and stable viscosity characteristic of the polymer system.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field production enhancement technology, and more specifically, relates to a polymer dry powder fracturing fluid and its preparation method. Background Technology

[0002] In the field of oil and gas field development, fracturing is a core technology for improving the production capacity of low-permeability and ultra-low-permeability reservoirs. By injecting fracturing fluid into the formation under high pressure to create artificial fractures, it can effectively connect natural fractures, reduce seepage resistance, and thus achieve efficient extraction of oil and gas resources. However, as oil and gas exploration and development extend to deep wells, ultra-deep wells, and complex lithological reservoirs, traditional polymer fracturing fluids suffer from problems such as slow viscosity recovery and poor temperature and shear resistance, making them unsuitable for field applications. Therefore, avoiding this phenomenon is key to solving the problem. For example, patent application CN119875610A discloses a long-lasting anti-scaling fracturing fluid and its preparation method. This invention's long-lasting anti-scaling fracturing fluid can eliminate or slow down the occurrence of tubing blockage and pump jamming caused by scaling during the production process after oil and gas well fracturing, ensuring the timeliness of oil well production and achieving cost reduction and efficiency improvement. However, its temperature and shear resistance needs further improvement. Summary of the Invention

[0003] Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this invention provides a polymer dry powder fracturing fluid and its preparation method. The polymer dry powder fracturing fluid of this invention has good shear resistance, high temperature resistance, drag reduction, and antibacterial properties.

[0005] Technical solution

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] The present invention discloses a method for preparing a polymer dry powder fracturing fluid, comprising the following steps:

[0008] (1) Preparation of modified nano-silica;

[0009] (2) Preparation of polymer dry powder;

[0010] (3) Preparation of modified fluorocarbon compounds;

[0011] (4) Add the polymer dry powder, modified fluorocarbon compound, polyvinylpyrrolidone and β-cyclodextrin into a mixer, stir and mix for 20-40 minutes, then pass through a 120-180 mesh sieve, package, and obtain polymer dry powder fracturing fluid.

[0012] Further, the preparation method of modified nano silica in step (1) is as follows: 50-60 mL of anhydrous ethanol and 17-20 mL of deionized water are added to the reactor and mixed to obtain a solvent. Then, 2-2.1 g of nano silica and 0.8-0.85 g of 3-(methacryloyloxy)propyltrimethoxysilane are added. The pH is adjusted to 4-5 with dilute hydrochloric acid with a concentration of 1 mol / L. After ultrasonic treatment for 40-50 min, the reaction is carried out at 45-55℃ for 2-3 h. After the reaction is completed, the mixture is centrifuged at high speed for 45-50 min, washed 2-3 times with anhydrous ethanol, and vacuum dried at 55-65℃ for 22-26 h to obtain modified nano silica.

[0013] Further, the preparation method of the polymer dry powder in step (2) is as follows: add 4-4.1g of acrylic acid, 4.2-4.3g of acrylamide, 1-1.1g of 2-acrylamido-2-methylpropanesulfonic acid, 0.4-0.5g of modified nano silica, and 0.02-0.03g of methylenebisacrylamide to 90-100mL of deionized water. Adjust the pH to 6.5-7 using a 10% sodium hydroxide solution. After ultrasonic treatment for 20-30min, purge with nitrogen for 10-15min. Then add 0.2-0.3g of ammonium persulfate to the solution and react at 60-70℃ for 2-4h. After the reaction is completed, dry the solid gel and pulverize it to obtain the polymer dry powder.

[0014] Furthermore, the method for preparing the modified fluorocarbon compound in step (3) is as follows:

[0015] S1: Add 20-21g of hexafluoropropylene dimer, 7.6-8g of methyl 4-bromomethylbenzoate, and 2.9-3g of anhydrous potassium fluoride to 50-60mL of N,N-dimethylacetamide solvent. Stir at 70-80℃ for 46-50h. After the reaction is complete, wash and dry, filter, and purify by column chromatography to obtain intermediate 1.

[0016] S2: Add intermediate 1 to 50-60 mL of methanol solution, mix well, add 55-60 mL of 1 mol / L sodium hydroxide aqueous solution in an ice-water bath at 0-5℃, then heat to 55-65℃ and stir for 4-6 h. After the reaction is complete, wash, adjust the pH of the system to 3-4 with 6 mol / L hydrochloric acid solution, and finally dry, filter, and concentrate under reduced pressure to obtain intermediate 2.

[0017] S3: Add toluene solvent, N-methyldiethanolamine, and intermediate 2 to the reactor, mix well, then add p-toluenesulfonic acid, and react for 12-16 h in an oil bath at 110-120℃. After the reaction is complete, cool to room temperature, wash and dry, and purify to obtain intermediate 3.

[0018] S4: Add intermediate 3 to acetonitrile solvent, stir and mix, add allyl chloride dropwise through a constant pressure funnel over 15-20 min, after the addition is complete, stir the reaction at 50-60℃ for 16-20 h, after the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, wash and dry to obtain intermediate 4.

[0019] S5: Add intermediate 4, dehydroazoamine, to N,N-dimethylformamide solvent, stir and react at 25-30℃ for 22-26 h. After the reaction is completed, remove the solvent by rotary evaporation and dry to obtain the modified fluorocarbon compound.

[0020] Further, the ratio of toluene, N-methyldiethanolamine, intermediate 2, and p-toluenesulfonic acid in S3 is 60-80 mL: 1.1-1.2 g: 9.2-9.3 g: 0.04-0.05 g.

[0021] Furthermore, the ratio of acetonitrile, intermediate 3, and allyl chloride in S4 is 60-80 mL: 4.2-4.5 mmol: 4.5-4.7 mmol.

[0022] Furthermore, the ratio of N,N-dimethylformamide, intermediate 4, and dehydroabimethamide in S5 is 50-60 mL: 2.5-2.6 mmol: 2.4-2.5 mmol.

[0023] Further, the weight parts of each component in step (4) are: 35-40 parts of polymer dry powder, 2-3 parts of modified fluorocarbon compound, 1-1.5 parts of polyvinylpyrrolidone, and 0.5-0.8 parts of β-cyclodextrin.

[0024] This invention also protects a polymer dry powder fracturing fluid, which is prepared by any one of the preparation methods described above.

[0025] Beneficial technical effects

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] After modification, nano-silica undergoes copolymerization with acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid, chemically bonding rigid and highly thermally stable nanoparticles to the polymer molecular chain. This effectively inhibits thermo-oxidative degradation and shear fracture of the molecular chain at high temperatures, improving the shear resistance and high-temperature resistance of the fracturing fluid. The fluorocarbon segments in the modified fluorocarbon compound significantly reduce the interfacial tension between the fracturing fluid and the pipeline wall and formation fluid. Combined with the uniform and stable viscosity characteristics of the polymer system, this effectively reduces flow resistance, enhancing the drag reduction capability of the fracturing fluid. Dehydroabimethamine itself has broad-spectrum antibacterial activity. Its rigid polycyclic structure can insert into the bacterial cell membrane, disrupting membrane integrity. The quaternary ammonium salt group carries a positive charge and can strongly adsorb onto the negatively charged bacterial surface, leading to leakage of cell contents. The synergistic effect of these two factors gives the fracturing fluid excellent antibacterial properties. Attached Figure Description

[0028] Figure 1 This is the synthesis reaction formula for the modified fluorocarbon compound in Example 1.

[0029] Figure 2 This is the infrared spectrum of the modified fluorocarbon compound from Example 1. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0032] The reagents used in the following specific embodiments are of analytical grade. Additionally:

[0033] Polyvinylpyrrolidone: Grade K30, purchased from Tianjin Guangfu Technology Development Co., Ltd.

[0034] Example 1

[0035] This embodiment provides a polymer dry powder fracturing fluid, the preparation method of which specifically includes the following steps:

[0036] (1) Add 50 mL of anhydrous ethanol and 17 mL of deionized water to the reactor and mix to obtain a solvent. Then add 2 g of nano silica and 0.8 g of 3-(methacryloyloxy)propyltrimethoxysilane. Adjust the pH to 4 with 1 mol / L dilute hydrochloric acid. After sonication for 40 min, react at 45 °C for 2 h. After the reaction is completed, centrifuge at high speed for 45 min, wash twice with anhydrous ethanol, and vacuum dry at 55 °C for 22 h to obtain modified nano silica.

[0037] (2) Add 4g of acrylic acid, 4.2g of acrylamide, 1g of 2-acrylamido-2-methylpropanesulfonic acid, 0.4g of modified nano silica and 0.02g of methylenebisacrylamide to 90mL of deionized water. Adjust the pH to 6.5 with 10% sodium hydroxide solution. After sonication for 20min, purge with nitrogen for 10min. Then add 0.2g of ammonium persulfate to the solution and react at 60℃ for 2h. After the reaction is complete, dry the solid gel and pulverize it to obtain polymer powder.

[0038] (3) Add 20g of hexafluoropropylene dimer, 7.6g of methyl 4-bromomethylbenzoate and 2.9g of anhydrous potassium fluoride to 50mL of N,N-dimethylacetamide solvent, stir at 70℃ for 46h, wash and dry after the reaction, filter, and purify by column chromatography to obtain intermediate 1.

[0039] (4) Add intermediate 1 to 50 mL of methanol solution, mix well, add 55 mL of 1 mol / L sodium hydroxide aqueous solution in an ice-water bath at 0 °C, then heat to 55 °C, stir and react for 4 h. After the reaction is complete, wash, adjust the pH of the system to 3 with 6 mol / L hydrochloric acid solution, and finally dry, filter, and concentrate under reduced pressure to obtain intermediate 2.

[0040] (5) Add 60 mL of toluene solvent, 1.1 g of N-methyldiethanolamine, and 9.2 g of intermediate 2 to the reactor, mix well, then add 0.04 g of p-toluenesulfonic acid, and react for 12 h in an oil bath at 110 °C. After the reaction is complete, cool to room temperature, wash and dry, and purify to obtain intermediate 3.

[0041] (6) Add 4.2 mmol of intermediate 3 to 60 mL of acetonitrile solvent, stir and mix, and add 4.5 mmol of allyl chloride dropwise over 15 min through a constant pressure funnel. After the addition is complete, stir the reaction at 50 °C for 16 h. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, wash and dry to obtain intermediate 4.

[0042] (7) Add 2.5 mmol of intermediate 4 and 2.4 mmol of dehydroabimethamide to 50 mL of N,N-dimethylformamide solvent, stir and react at 25 °C for 22 h. After the reaction is complete, remove the solvent by rotary evaporation, dry, and obtain the modified fluorocarbon compound, such as... Figure 1 As shown;

[0043] (8) Add 35 parts by weight of polymer dry powder, 2 parts by weight of modified fluorocarbon compound, 1 part by weight of polyvinylpyrrolidone and 0.5 parts by weight of β-cyclodextrin into a mixer, stir and mix for 20 minutes, then pass through a 120-mesh sieve and package to obtain polymer dry powder fracturing fluid.

[0044] Figure 2 The infrared spectrum of the modified fluorocarbon compound is shown in the wavenumber range of 1000-1300 cm⁻¹. -1 In the region, the spectrum shows strong and broad absorption peaks, corresponding to the stretching vibrations of the CF bond, proving the introduction of fluorine-carbon segments into the molecule; at wavenumbers of 1700-1750 cm⁻¹... -1 In the region, there is a distinct strong absorption peak, corresponding to the stretching vibration of the ester carbonyl group (C=O), and also in the 1100-1300 cm⁻¹ region. -1 Stretching vibrations of COC in the ester group were observed in the region, proving that the esterification reaction of intermediate 2 with N-methyldiethanolamine occurred successfully; at wavenumbers of 3200-3500 cm⁻¹ -1 The weak, broad absorption peak in the region corresponds to the stretching vibration of the NH bond, proving that the dehydroabimethamine was successfully grafted onto the molecular chain; the absorption peaks at wavenumbers of 1600-1680 cm⁻¹... -1 The absorption peak in the region corresponds to the stretching vibration of the C=C bond, which is an inherent structural feature of the aromatic ring of the dehydroabimethamine. The results indicate that the modified fluorocarbon compound was successfully prepared.

[0045] Example 2

[0046] This embodiment provides a polymer dry powder fracturing fluid, the preparation method of which specifically includes the following steps:

[0047] (1) Add 60 mL of anhydrous ethanol and 20 mL of deionized water to the reactor and mix to obtain a solvent. Then add 2.1 g of nano silica and 0.85 g of 3-(methacryloyloxy)propyltrimethoxysilane. Adjust the pH to 5 with 1 mol / L dilute hydrochloric acid. After sonication for 50 min, react at 55 °C for 3 h. After the reaction is completed, centrifuge at high speed for 50 min, wash three times with anhydrous ethanol, and vacuum dry at 65 °C for 26 h to obtain modified nano silica.

[0048] (2) Add 4.1g of acrylic acid, 4.3g of acrylamide, 1.1g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of modified nano silica and 0.03g of methylenebisacrylamide to 100mL of deionized water. Adjust the pH to 7 with 10% sodium hydroxide solution. After sonication for 30min, purge with nitrogen for 15min. Then add 0.3g of ammonium persulfate to the solution and react at 70℃ for 4h. After the reaction is complete, dry the solid gel and pulverize it to obtain polymer powder.

[0049] (3) Add 21g of hexafluoropropylene dimer, 8g of methyl 4-bromomethylbenzoate and 3g of anhydrous potassium fluoride to 60mL of N,N-dimethylacetamide solvent, stir at 80℃ for 50h, wash and dry after the reaction, filter, and purify by column chromatography to obtain intermediate 1.

[0050] (4) Add intermediate 1 to 60 mL of methanol solution, mix well, add 60 mL of 1 mol / L sodium hydroxide aqueous solution in an ice-water bath at 5 °C, then heat to 65 °C, stir for 6 h, wash after the reaction, adjust the pH of the system to 4 with 6 mol / L hydrochloric acid solution, and finally dry, filter, and concentrate under reduced pressure to obtain intermediate 2.

[0051] (5) Add 80 mL of toluene solvent, 1.2 g of N-methyldiethanolamine, and 9.3 g of intermediate 2 to the reactor, mix well, then add 0.05 g of p-toluenesulfonic acid, and react for 16 h in an oil bath at 120 °C. After the reaction is complete, cool to room temperature, wash and dry, and purify to obtain intermediate 3.

[0052] (6) Add 4.5 mmol of intermediate 3 to 80 mL of acetonitrile solvent, stir and mix, and add 4.7 mmol of allyl chloride dropwise over 20 min through a constant pressure funnel. After the addition is complete, stir the reaction at 60 °C for 20 h. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, wash and dry to obtain intermediate 4.

[0053] (7) Add 2.6 mmol of intermediate 4 and 2.5 mmol of dehydroabimethamide to 60 mL of N,N-dimethylformamide solvent, stir at 30 °C for 26 h, remove the solvent by rotary evaporation after the reaction is completed, and dry to obtain the modified fluorocarbon compound.

[0054] (8) Add 40 parts by weight of polymer dry powder, 3 parts by weight of modified fluorocarbon compound, 1.5 parts by weight of polyvinylpyrrolidone and 0.8 parts by weight of β-cyclodextrin to a mixer, stir and mix for 40 min, then pass through a 180 mesh sieve and package to obtain polymer dry powder fracturing fluid.

[0055] Example 3

[0056] This embodiment provides a polymer dry powder fracturing fluid, the preparation method of which specifically includes the following steps:

[0057] (1) Add 53 mL of anhydrous ethanol and 18 mL of deionized water to the reactor and mix to obtain a solvent. Then add 2.03 g of nano silica and 0.82 g of 3-(methacryloyloxy)propyltrimethoxysilane. Adjust the pH to 4 with 1 mol / L dilute hydrochloric acid. After sonication for 42 min, react at 48 °C for 2 h. After the reaction is completed, centrifuge at high speed for 46 min, wash twice with anhydrous ethanol, and vacuum dry at 58 °C for 23 h to obtain modified nano silica.

[0058] (2) Add 4.03g of acrylic acid, 4.22g of acrylamide, 1.02g of 2-acrylamido-2-methylpropanesulfonic acid, 0.42g of modified nano silica and 0.02g of methylenebisacrylamide to 92mL of deionized water. Adjust the pH to 6.5 with 10% sodium hydroxide solution. After sonication for 22min, purge with nitrogen for 12min. Then add 0.22g of ammonium persulfate to the solution and react at 63℃ for 3h. After the reaction is complete, dry the solid gel and pulverize it to obtain polymer powder.

[0059] (3) Add 20.3 g of hexafluoropropylene dimer, 7.7 g of methyl 4-bromomethylbenzoate and 2.93 g of anhydrous potassium fluoride to 52 mL of N,N-dimethylacetamide solvent, stir at 72 °C for 47 h, wash and dry after reaction, filter, and purify by column chromatography to obtain intermediate 1;

[0060] (4) Add intermediate 1 to 52 mL of methanol solution, mix well, add 57 mL of 1 mol / L sodium hydroxide aqueous solution in an ice-water bath at 2 °C, then heat to 58 °C, stir for 5 h, wash after the reaction, adjust the pH of the system to 3 with 6 mol / L hydrochloric acid solution, and finally dry, filter, and concentrate under reduced pressure to obtain intermediate 2.

[0061] (5) Add 68 mL of toluene solvent, 1.13 g of N-methyldiethanolamine and 9.22 g of intermediate 2 to the reactor, mix well, then add 0.04 g of p-toluenesulfonic acid, and react for 14 h in an oil bath at 113 °C. After the reaction is complete, cool to room temperature, wash and dry, and purify to obtain intermediate 3.

[0062] (6) Add 4.3 mmol of intermediate 3 to 68 mL of acetonitrile solvent, stir and mix, and add 4.6 mmol of allyl chloride dropwise over 16 min through a constant pressure funnel. After the addition is complete, stir the reaction at 55 °C for 17 h. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, wash and dry to obtain intermediate 4.

[0063] (7) Add 2.52 mmol of intermediate 4 and 2.42 mmol of dehydroabimethamide to 52 mL of N,N-dimethylformamide solvent, stir at 26 °C for 23 h, remove the solvent by rotary evaporation after the reaction is completed, and dry to obtain the modified fluorocarbon compound.

[0064] (8) Add 36 parts by weight of polymer dry powder, 2 parts by weight of modified fluorocarbon compound, 1 part by weight of polyvinylpyrrolidone and 0.6 parts by weight of β-cyclodextrin into a mixer, stir and mix for 30 min, then pass through a 140 mesh sieve and package to obtain polymer dry powder fracturing fluid.

[0065] Example 4

[0066] This embodiment provides a polymer dry powder fracturing fluid, the preparation method of which specifically includes the following steps:

[0067] (1) Add 58 mL of anhydrous ethanol and 19 mL of deionized water to the reactor and mix to obtain a solvent. Then add 2.08 g of nano silica and 0.84 g of 3-(methacryloyloxy)propyltrimethoxysilane. Adjust the pH to 5 with 1 mol / L dilute hydrochloric acid. After sonication for 48 min, react at 52 °C for 3 h. After the reaction is completed, centrifuge at high speed for 48 min, wash three times with anhydrous ethanol, and vacuum dry at 62 °C for 25 h to obtain modified nano silica.

[0068] (2) Add 4.07g of acrylic acid, 4.28g of acrylamide, 1.07g of 2-acrylamido-2-methylpropanesulfonic acid, 0.48g of modified nano silica and 0.03g of methylenebisacrylamide to 98mL of deionized water. Adjust the pH to 7 with 10% sodium hydroxide solution. After sonication for 28min, purge with nitrogen for 14min. Then add 0.28g of ammonium persulfate to the solution and react at 67℃ for 4h. After the reaction is complete, dry the solid gel and pulverize it to obtain polymer powder.

[0069] (3) Add 20.7 g of hexafluoropropylene dimer, 7.9 g of methyl 4-bromomethylbenzoate and 2.97 g of anhydrous potassium fluoride to 58 mL of N,N-dimethylacetamide solvent. Stir at 78 °C for 49 h. After the reaction is complete, wash and dry, filter, and purify by column chromatography to obtain intermediate 1.

[0070] (4) Add intermediate 1 to 58 mL of methanol solution, mix well, add 59 mL of 1 mol / L sodium hydroxide aqueous solution in an ice-water bath at 3 °C, then heat to 62 °C, stir for 6 h, wash after the reaction, adjust the pH of the system to 4 with 6 mol / L hydrochloric acid solution, and finally dry, filter, and concentrate under reduced pressure to obtain intermediate 2.

[0071] (5) Add 75 mL of toluene solvent, 1.18 g of N-methyldiethanolamine, and 9.28 g of intermediate 2 to the reactor, mix well, then add 0.05 g of p-toluenesulfonic acid, and react for 15 h in an oil bath at 117 °C. After the reaction is complete, cool to room temperature, wash and dry, and purify to obtain intermediate 3.

[0072] (6) Add 4.4 mmol of intermediate 3 to 75 mL of acetonitrile solvent, stir and mix, and add 4.6 mmol of allyl chloride dropwise over 18 min through a constant pressure funnel. After the addition is complete, stir the reaction at 58 °C for 19 h. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, wash and dry to obtain intermediate 4.

[0073] (7) Add 2.58 mmol of intermediate 4 and 2.48 mmol of dehydroabimethamide to 58 mL of N,N-dimethylformamide solvent, stir at 28 °C for 25 h, remove the solvent by rotary evaporation after the reaction is completed, and dry to obtain the modified fluorocarbon compound.

[0074] (8) Add 39 parts by weight of polymer dry powder, 3 parts by weight of modified fluorocarbon compound, 1.5 parts by weight of polyvinylpyrrolidone and 0.7 parts by weight of β-cyclodextrin to a mixer, stir and mix for 35 minutes, then pass through a 160-mesh sieve and package to obtain polymer dry powder fracturing fluid.

[0075] Comparative Example 1

[0076] The main difference between this comparative example and Example 4 is that intermediate 4 is used instead of the modified fluorocarbon compound.

[0077] Comparative Example 2

[0078] The main difference between this comparative example and Example 4 is that no modified nano-silica was added.

[0079] Performance testing

[0080] (1) Apparent viscosity, shear resistance, and drag reduction tests: 3g of the polymer dry powder fracturing fluid prepared in Examples 1-4 and Comparative Examples 1-2 were weighed and slowly added to 497g of a prepared 5000mg / L sodium chloride aqueous solution under stirring. The mixture was stirred continuously until it was completely dissolved and there were no "fish eyes" (unclear particles), resulting in 500g of a 0.6wt% fracturing fluid solution to be tested. The apparent viscosity, shear resistance, and drag reduction were tested at 60℃ according to SYT6376-2008 "Technical Conditions for Fracturing Fluid". The test results are shown in Table 1.

[0081] Table 1: Apparent viscosity, shear resistance, and drag reduction tests

[0082] project Apparent viscosity (mPa·s) Viscosity after shearing (mPa·s) Drag reduction rate (%) Example 1 97 96 83 Example 2 99 98 86 Example 3 98 97 83 Example 4 98 96 84 Comparative Example 1 92 85 76 Comparative Example 2 81 68 70

[0083] As can be seen from Table 1, the polymer dry powder fracturing fluids prepared in Examples 1-4 have good apparent viscosity, shear resistance and drag reduction.

[0084] (2) Temperature resistance test: 3g of the polymer dry powder fracturing fluid prepared in Examples 1-4 and Comparative Examples 1-2 were weighed and slowly added to 497g of a prepared 5000mg / L sodium chloride aqueous solution under stirring. The mixture was stirred continuously until it was completely dissolved and there were no "fish eyes", resulting in 500g of a 0.6wt% fracturing fluid solution to be tested. The apparent viscosity, shear resistance, and drag reduction rate were tested at 200℃ according to SYT6376-2008 "Technical Conditions for Fracturing Fluid". The test results are shown in Table 2.

[0085] Table 2: Temperature Resistance Test

[0086] project Apparent viscosity (mPa·s) Viscosity after shearing (mPa·s) Drag reduction rate (%) Example 1 96 94 81 Example 2 98 97 83 Example 3 97 95 82 Example 4 96 94 83 Comparative Example 1 90 80 72 Comparative Example 2 78 57 59

[0087] As can be seen from Table 2, the polymer dry powder fracturing fluids prepared in Examples 1-4 have good temperature resistance.

[0088] (3) Antibacterial performance test: The flowback fluid from the No. 7 hydraulic fracturing oil well in Haishiwan, Gansu (containing 89.1 wt% water and 1.2 wt% sulfate) was filtered through a 0.22 μm filter membrane to remove background microbial interference and obtain sterile flowback fluid. Flavobacterium C was inoculated into liquid culture medium and cultured under anaerobic conditions at 37℃ to the logarithmic phase. The cells were washed with sterile physiological saline, resuspended, and the cell concentration was adjusted to approximately 1 × 10⁻⁶. 6CFU / mL was used as the working bacterial suspension. 60 mg of the polymer dry powder fracturing fluid prepared in Examples 1-4 and Comparative Examples 1-2 were weighed and dissolved in 10 mL of sterile flowback solution to prepare a 0.6% stock solution. For testing, each sample required two sets of parallel test tubes for sampling at "0 hours" and "48 hours". The "0 hour" setting was used to determine the initial bacterial concentration, including a growth control group (4.75 mL sterile flowback solution + 0.25 mL working bacterial suspension) and an experimental group (4.50 mL sterile flowback solution + 0.25 mL stock solution + 0.25 mL working bacterial suspension), with three replicates for each group. After mixing, samples were immediately taken for serial dilution and plated, and then the test tubes in that group were discarded. The "48-hour" culture group included: a growth control group (9.5 mL sterile efflux solution + 0.5 mL working bacterial suspension), an experimental group (9.0 mL sterile efflux solution + 0.5 mL stock solution + 0.5 mL working bacterial suspension), and a sample background control group (9.5 mL sterile efflux solution + 0.5 mL stock solution), with three replicates for each group. The mixtures were immediately sealed after mixing. All "48-hour" culture group tubes and "0-hour" group plates were placed in an anaerobic jar at 37°C and incubated for 48 hours. After incubation, samples were taken from each tube in the "48-hour" culture group, serially diluted, and plated. All plates were incubated for another 7 days in an anaerobic environment at 37°C until colony morphology stabilized, and then counted. The average colony concentration S0 of the growth control group after 48 hours and the average colony concentration S in the experimental group were used as the basis for comparison. n Calculate the inhibition rate: Inhibition rate = (S0 - S) n ) / S0. The test results are shown in Table 3.

[0089] Table 3: Antibacterial Performance Test

[0090] project Antibacterial rate (%) Example 1 99.6 Example 2 99.8 Example 3 99.7 Example 4 99.8 Comparative Example 1 84.5 Comparative Example 2 99.3

[0091] As can be seen from Table 3, the polymer dry powder fracturing fluids prepared in Examples 1-4 have good antibacterial properties.

[0092] The comparison shows that Comparative Example 1, which uses intermediate 4 instead of modified fluorocarbon, lacks the rigidity enhancement and interfacial stabilization effect brought by the dehydroabimethamine modification. The polymer molecular chains are prone to slippage under shear force, resulting in a decrease in viscosity and drag reduction. Furthermore, it lacks the antibacterial group of dehydroabimethamine and relies solely on the quaternary ammonium salt group of intermediate 4 for antibacterial effect. Therefore, the antibacterial agent performance is not as good as that of the example. Comparative Example 2, which does not add modified nano-silica, loses the rigid reinforcing skeleton of nano-silica. The polymer molecular chains are prone to thermo-oxidative degradation and mechanical breakage under high temperature and high shear, with the most significant viscosity decay. Moreover, the decay rate is greater at high temperature than at room temperature. Therefore, the apparent viscosity, shear resistance, drag reduction, and temperature resistance all decrease. However, since nano-silica has no antibacterial function, its absence does not affect the bactericidal performance. Therefore, the bactericidal rate of Comparative Example 2 can still reach 99.3%.

[0093] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0094] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0095] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a polymer dry powder fracturing fluid, characterized in that, Includes the following steps: (1) Preparation of modified nano-silica; (2) Preparation of polymer dry powder; (3) Preparation of modified fluorocarbon compounds; (4) Add the polymer dry powder, modified fluorocarbon compound, polyvinylpyrrolidone and β-cyclodextrin into a mixer, stir and mix for 20-40 minutes, then pass through a 120-180 mesh sieve, package, and obtain polymer dry powder fracturing fluid.

2. The method for preparing polymer dry powder fracturing fluid according to claim 1, characterized in that, The method for preparing modified nano-silica in step (1) is as follows: 50-60 mL of anhydrous ethanol and 17-20 mL of deionized water are added to the reactor and mixed to obtain a solvent. Then, 2-2.1 g of nano-silica and 0.8-0.85 g of 3-(methacryloyloxy)propyltrimethoxysilane are added. The pH is adjusted to 4-5 with 1 mol / L dilute hydrochloric acid. After ultrasonic treatment for 40-50 min, the mixture is reacted at 45-55℃ for 2-3 h. After the reaction is completed, the mixture is centrifuged at high speed for 45-50 min, washed 2-3 times with anhydrous ethanol, and vacuum dried at 55-65℃ for 22-26 h to obtain modified nano-silica.

3. The method for preparing polymer dry powder fracturing fluid according to claim 1, characterized in that, The preparation method of polymer dry powder in step (2) is as follows: add 4-4.1g of acrylic acid, 4.2-4.3g of acrylamide, 1-1.1g of 2-acrylamido-2-methylpropanesulfonic acid, 0.4-0.5g of modified nano silica, and 0.02-0.03g of methylenebisacrylamide to 90-100mL of deionized water. Adjust the pH to 6.5-7 using a 10% sodium hydroxide solution. After ultrasonic treatment for 20-30min, purge with nitrogen for 10-15min. Then add 0.2-0.3g of ammonium persulfate to the solution and react at 60-70℃ for 2-4h. After the reaction is completed, dry the solid gel and pulverize it to obtain polymer dry powder.

4. The method for preparing polymer dry powder fracturing fluid according to claim 1, characterized in that, The method for preparing the modified fluorocarbon compound in step (3) is as follows: S1: Add 20-21g of hexafluoropropylene dimer, 7.6-8g of methyl 4-bromomethylbenzoate, and 2.9-3g of anhydrous potassium fluoride to 50-60mL of N,N-dimethylacetamide solvent. Stir at 70-80℃ for 46-50h. After the reaction is complete, wash and dry, filter, and purify by column chromatography to obtain intermediate 1. S2: Add intermediate 1 to 50-60 mL of methanol solution, mix well, add 55-60 mL of 1 mol / L sodium hydroxide aqueous solution in an ice-water bath at 0-5℃, then heat to 55-65℃ and stir for 4-6 h. After the reaction is complete, wash, adjust the pH of the system to 3-4 with 6 mol / L hydrochloric acid solution, and finally dry, filter, and concentrate under reduced pressure to obtain intermediate 2. S3: Add toluene solvent, N-methyldiethanolamine, and intermediate 2 to the reactor, mix well, then add p-toluenesulfonic acid, and react for 12-16 h in an oil bath at 110-120℃. After the reaction is completed, cool to room temperature, wash and dry, and purify to obtain intermediate 3. S4: Add intermediate 3 to acetonitrile solvent, stir and mix, add allyl chloride dropwise through a constant pressure funnel over 15-20 min, after the addition is complete, stir the reaction at 50-60℃ for 16-20 h, after the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, wash and dry to obtain intermediate 4. S5: Add intermediate 4, dehydroazoamine, to N,N-dimethylformamide solvent, stir and react at 25-30℃ for 22-26 h. After the reaction is completed, remove the solvent by rotary evaporation and dry to obtain the modified fluorocarbon compound.

5. The method for preparing polymer dry powder fracturing fluid according to claim 4, characterized in that, The ratio of toluene, N-methyldiethanolamine, intermediate 2, and p-toluenesulfonic acid in S3 is 60-80 mL. 1.1-1.2g:9.2-9.3g:0.04-0.05g.

6. The method for preparing polymer dry powder fracturing fluid according to claim 4, characterized in that, The ratio of acetonitrile, intermediate 3, and allyl chloride in S4 is 60-80 mL: 4.2-4.5 mmol: 4.5-4.7 mmol.

7. The method for preparing polymer dry powder fracturing fluid according to claim 4, characterized in that, The ratio of N,N-dimethylformamide, intermediate 4, and dehydroabimethamide in S5 is 50-60 mL: 2.5-2.6 mmol: 2.4-2.5 mmol.

8. The method for preparing polymer dry powder fracturing fluid according to claim 1, characterized in that, The weight parts of each component in step (4) are: 35-40 parts of polymer dry powder, 2-3 parts of modified fluorocarbon compound, 1-1.5 parts of polyvinylpyrrolidone, and 0.5-0.8 parts of β-cyclodextrin.

9. A polymer dry powder fracturing fluid, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

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