A high salt-resistant suspension polymer composition for fracturing and its preparation method

Abstract

This invention relates to the field of oil and gas development technology, and more particularly to a high-salt-resistant suspension polymer composition for fracturing and its preparation method. By weight, the composition comprises the following raw materials: 30-50 parts modified acrylamide polymer, 40-60 parts industrial white oil, 1-5 parts emulsifier, and 1-3 parts phosphorylated bamboo fiber. This composition exhibits high drag reduction effect, as well as excellent salt resistance, shear resistance, temperature resistance, and antibacterial properties, making it suitable for fracturing operations in high-saltification flowback fluids.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and in particular to a high salt-resistant suspension polymer composition for fracturing and its preparation method. Background Technology

[0002] Hydraulic fracturing technology is a core process for improving the productivity of oil and gas wells, and its application is particularly widespread in the development of unconventional oil and gas reservoirs such as shale oil and gas. Drag reducers, as key functional additives in fracturing fluids, can effectively reduce the risks and difficulties of fracturing operations, improve the proppant-carrying capacity of the system, and optimize the fracturing effect, playing a crucial role in increasing and stabilizing oil and gas well production. Currently, drag reducers are mostly prepared by compounding emulsifiers, dispersants, and other additives with polyacrylamide and its derivatives as the main component. Although these products have certain drag-reducing properties, their temperature resistance is insufficient, making it difficult to meet the exploration and development needs of deep, high-temperature, and high-pressure reservoirs. Furthermore, due to the high cost of flowback fluid treatment, over 70% of fracturing fluid preparations currently used in the field employ oilfield flowback fluids with complex compositions, high salinity, and high calcium and magnesium ion content. This places even more stringent requirements on the salt resistance and calcium and magnesium ion resistance of drag reducers. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, one of the objectives of the present invention is to provide a high salt-resistant suspension polymer composition for fracturing. This composition has a high drag reduction effect, as well as excellent salt resistance, shear resistance, temperature resistance and antibacterial properties, and is suitable for fracturing operations in high-mineralization flowback fluids.

[0004] The second objective of this invention is to provide a method for preparing a high salt-resistant suspension polymer composition for fracturing, which is simple in process, mild in conditions, and easy to industrialize.

[0005] A high salt-resistant suspension polymer composition for fracturing, comprising the following raw materials by weight: 30-50 parts of modified acrylamide polymer, 40-60 parts of industrial white oil, 1-5 parts of emulsifier, and 1-3 parts of phosphorylated bamboo fiber; The preparation process of the modified acrylamide polymer is as follows: Acrylamide, acrylic acid, cationic monomer, and sodium dodecyl sulfate are added to deionized water, and an initiator is added under inert gas protection to carry out the reaction. After purification, the product is obtained. The structural formula of the cationic monomer is as follows: .

[0006] The modified polyacrylamide of the present invention is prepared by free radical copolymerization of acrylamide, acrylic acid and cationic monomer; the cationic monomer is prepared by reacting 4-cyanopyridine and 2-aminopyridine to obtain intermediate 1 containing triazolidine structure, and then reacting intermediate 1 with ethyl chloride acrylate to introduce pyridinium cationic structure to obtain the product.

[0007] Preferably, the molar ratio of acrylamide, acrylic acid, and cationic monomer is 1:(0.3-0.6):(0.06-0.12); the amount of sodium dodecyl sulfate added is 1-2% of the mass of the cationic monomer; the amount of initiator added is 0.3-0.8% of the total mass of acrylamide, acrylic acid, and cationic monomer; the initiator is composed of cerium ammonium nitrate and sodium bisulfite in a mass ratio of 1:1; the reaction temperature is 80-90℃, and the reaction time is 8-10h.

[0008] Preferably, the preparation process of the cationic monomer is as follows: (1) 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline and zinc iodide were added to 1,2-dichlorobenzene and heated and stirred under sealed conditions. After purification, intermediate 1 was obtained. The structural formula of intermediate 1 is as follows: ; (2) The intermediate 1 and ethyl chloride acrylate were added to acetonitrile, and the mixture was purified after reaction to obtain the cationic monomer.

[0009] Preferably, the molar ratio of 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline, and zinc iodide in step (1) is 1:(1.1-1.3):(0.05-0.55):(0.05-0.55):(0.1-0.11); the heating and stirring reaction is carried out at a temperature of 130-135°C for 24-28 hours.

[0010] Preferably, in step (2), the molar ratio of intermediate 1 to ethyl chloride acrylate is 1:(1.5-1.65); the reaction temperature is 70-75℃ and the reaction time is 20-24h.

[0011] Preferably, the preparation process of the phosphorylated bamboo fiber is as follows: Choline chloride, urea, and phosphorous acid were mixed and stirred to obtain a ternary reactive deep eutectic solvent; bamboo fiber was added to the ternary reactive deep eutectic solvent, and the mixture was heated and purified to obtain the phosphorylated bamboo fiber.

[0012] This invention uses a reactive ternary deep eutectic solvent composed of choline chloride, urea and phosphorous acid to treat bamboo fiber. This solvent can simultaneously induce fiber swelling and achieve in-situ phosphorylation, thereby obtaining phosphorylated bamboo fiber.

[0013] Preferably, the molar ratio of choline chloride, urea, and phosphorous acid is 1:2:1; the stirring temperature is 90-95℃; the ratio of bamboo fiber to ternary reactive deep eutectic solvent is 1g:(40-45)mL; and the heating reaction temperature is 130-150℃ for 2-4h.

[0014] Preferably, the emulsifier is Span 80 or Tween 60.

[0015] The second objective of this invention is achieved by the following technical solution: The preparation method of the above-mentioned high salt-resistant suspension polymer composition for fracturing includes the following steps: Add emulsifier and phosphorylated bamboo fiber to industrial white oil, stir, then add modified acrylamide polymer and continue stirring to obtain the final product.

[0016] Preferably, the stirring temperature is 40-60℃ and the stirring time is 20-40 min; the stirring time is 1-2 h.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention provides a high salt-resistant suspension polymer composition for fracturing, comprising modified acrylamide polymer, industrial white oil, emulsifier, phosphorylated bamboo fiber, and other raw materials. This composition has excellent drag reduction effect, salt resistance, shear resistance, temperature resistance, and antibacterial properties, and is suitable for fracturing operations in high-mineralization flowback fluids.

[0018] (2) This invention improves the drag reduction, salt resistance, shear resistance, temperature resistance, and antibacterial properties of the composition by introducing a modified acrylamide polymer. Specifically, the modified acrylamide polymer side chain contains pyridinium cations and rigid triazolidine ring structures; wherein, the pyridinium cations can form strong electrostatic interactions with the phosphate groups of phosphorylated bamboo fibers, playing a stable suspension, dispersion, and support role in the micelle system, thereby significantly improving the salt resistance of the system; the rigid triazolidine ring structure can effectively enhance the shear resistance and temperature resistance of the polymer chain. At the same time, the carboxyl groups on the polyacrylamide chain can form stable coordination bonds with calcium and magnesium metal ions in the fracturing flowback fluid, constructing a three-dimensional network structure between the molecular chains, so that the system remains structurally stable in a high-mineralization environment, further enhancing the salt resistance stability. In addition, the rigid triazolidine structure in the cationic monomer helps improve the temperature resistance of the system. At the same time, it has antibacterial activity, which can endow the system with excellent antibacterial properties. There is no need to add bactericides and other agents on site, which reduces the investment and use of equipment and pipelines, making on-site construction more convenient and orderly.

[0019] (3) This invention improves the drag reduction, salt resistance, shear resistance, and temperature resistance of the composition by introducing phosphorylated bamboo fiber. Specifically, the surface of phosphorylated bamboo fiber is rich in phosphate groups. On the one hand, these groups generate strong electrostatic interactions with the pyridinium cations in the modified acrylamide polymer, enhancing the suspension dispersion and shear resistance of the system. On the other hand, the phosphate groups synergistically interact with the carboxyl groups on the polymer chain, coordinating and crosslinking with calcium and magnesium ions to maintain the integrity of the three-dimensional network structure in a high-salt environment, thereby significantly improving salt resistance and temperature resistance. In addition, phosphorylated bamboo fiber has good biodegradability and can gradually degrade under formation conditions, avoiding solid residue clogging the formation. Its synergistic effect with the cationic monomers in the polymer can further enhance the antibacterial properties of the composition.

[0020] (4) The present invention provides a method for preparing a high salt-resistant suspension polymer composition for fracturing. The method is simple, mild, easy to operate, and easy to mass-produce in the industrial sector. The prepared composition has strong stability, good compatibility on site, and rapid dissolution, which can greatly simplify the process of adding fracturing agents. Attached Figure Description

[0021] Figure 1 SEM image of the phosphorylated bamboo fiber obtained in Example 1 of this invention; Figure 2 The infrared spectrum of the phosphorylated bamboo fiber obtained in Example 1 of this invention. Detailed Implementation

[0022] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0023] In this invention, the diameter of the bamboo fiber is 10-15 μm; the initiator is composed of cerium ammonium nitrate and sodium bisulfite in a mass ratio of 1:1.

[0024] Preparation Example 1 A phosphorylated bamboo fiber, the preparation process is as follows: Choline chloride, urea, and phosphorous acid were mixed in a molar ratio of 1:2:1 and stirred at 92°C until the solution was homogeneous and transparent to obtain a ternary reactive deep eutectic solvent. Bamboo fiber was added to the solvent at a ratio of 1 g to 43 mL, and the mixture was reacted at 140°C for 3 hours. After the reaction was complete, the mixture was filtered, washed with deionized water, and vacuum dried to obtain phosphorylated bamboo fiber. See [Image of SEM image of phosphorylated bamboo fiber]. Figure 1 .

[0025] Preparation Example 2 A phosphorylated bamboo fiber, the preparation process is as follows: Choline chloride, urea, and phosphorous acid were mixed in a molar ratio of 1:2:1 and stirred at 90°C until the solution was uniform and transparent to obtain a ternary reactive deep eutectic solvent. Bamboo fiber was added to the ternary reactive deep eutectic solvent at a ratio of 1 g:40 mL, and the mixture was reacted at 130°C for 4 h. After the reaction was completed, the mixture was filtered, washed with deionized water, and vacuum dried to obtain phosphorylated bamboo fiber.

[0026] Preparation Example 3 A phosphorylated bamboo fiber, the preparation process is as follows: Choline chloride, urea, and phosphorous acid were mixed in a molar ratio of 1:2:1 and stirred at 95°C until the solution was uniform and transparent to obtain a ternary reactive deep eutectic solvent. Bamboo fiber was added to the ternary reactive deep eutectic solvent at a ratio of 1 g:45 mL, and the mixture was reacted at 150°C for 2 h. After the reaction was completed, the mixture was filtered, washed with deionized water, and vacuum dried to obtain phosphorylated bamboo fiber.

[0027] Preparation Example 4 A cationic monomer, prepared as follows: (1) Using 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline, zinc iodide, and 1,2-dichlorobenzene in a ratio of 1 mmol: 1.2 mmol: 0.2 mmol: 0.3 mmol: 0.105 mmol: 2.5 mL, 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline (CAS: 66-71-7) and zinc iodide were added to 1,2-dichlorobenzene. Under sealed conditions, the mixture was heated to 133 °C and stirred for 25 h. After cooling to room temperature, it was diluted with ethyl acetate, filtered, and the filtrate was concentrated and purified by column chromatography (V 己烷 V 乙酸乙酯 =1:4), yielding intermediate 1 (yield 71.9%); the NMR and mass spectrometry results for intermediate 1 are as follows: 1 HNMR: (400MHz, DMSO-d6) δ: 7.34-7.40 (m, 2H), 7.97-7.81 (d, 2H), 8.57-8.61 (dd, 1H), 8.76-8.80 (d, 2H), 8.96-9.00 (m, 1H). MS(ESI)m / z=196.07M.

[0028] (2) Intermediate 1, ethyl chloride acrylate, and acetonitrile were dissolved in acetonitrile at a ratio of 1 mmol: 1.6 mmol: 2.5 mL. The mixture was reacted at 72 °C for 22 h. After the reaction was completed, the mixture was concentrated under reduced pressure. The residue was purified by column chromatography (V... 二氯甲烷 V 甲醇 =10:1~5:1), yielding cationic monomers (yield 52.5%); NMR and mass spectrometry results of the cationic monomers are as follows: 1 HNMR: (400MHz, DMSO-d6) δ: 4.45-4.49 (m, 2H), 4.87-4.91 (m, 2H), 5.81-5.85 (dd, 1H), 6.10-6.14 (m, 1 H), 6.39-6.43 (dd, 1H), 7.34-7.40 (m, 2H), 8.57-8.61 (dd, 1H), 8.94-9.00 (m, 3H), 9.06-9.10 (d, 2H). MS(ESI)m / z=295.12[M] + .

[0029] Preparation Example 5 A cationic monomer, prepared as follows: (1) Using 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline, zinc iodide, and 1,2-dichlorobenzene in a ratio of 1 mmol:1.1 mmol:0.05 mmol:0.05 mmol:0.1 mmol:2 mL, 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline, and zinc iodide were added to 1,2-dichlorobenzene. Under sealed conditions, the mixture was heated to 130 °C and stirred for 28 h. After cooling to room temperature, it was diluted with ethyl acetate, filtered, and the filtrate was concentrated and purified by column chromatography (V 己烷 V 乙酸乙酯 =1:4), to obtain intermediate 1 (yield 68.4%); the NMR and mass spectrometry results of intermediate 1 were consistent with those of preparation example 4.

[0030] (2) With intermediate 1, ethyl chloride acrylate, and acetonitrile in a ratio of 1 mmol: 1.5 mmol: 2 mL, intermediate 1 and ethyl chloride acrylate were dissolved in acetonitrile and reacted at 70 °C for 24 h. After the reaction was completed, the mixture was concentrated under reduced pressure, and the residue was purified by column chromatography (V). 二氯甲烷 V 甲醇 =10:1~5:1), yielding cationic monomers (yield 49.1%); the NMR and mass spectrometry results of the cationic monomers were consistent with those of Preparation Example 4.

[0031] Preparation Example 6 A cationic monomer, prepared as follows: (1) Using 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline, zinc iodide, and 1,2-dichlorobenzene in a ratio of 1 mmol:1.3 mmol:0.55 mmol:0.55 mmol:0.11 mmol:3 mL, 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline, and zinc iodide were added to 1,2-dichlorobenzene. Under sealed conditions, the mixture was heated to 135 °C and stirred for 24 h. After cooling to room temperature, it was diluted with ethyl acetate, filtered, and the filtrate was concentrated and purified by column chromatography (V 己烷 V 乙酸乙酯 =1:4), to obtain intermediate 1 (yield 69.0%); the NMR and mass spectrometry results of intermediate 1 were consistent with those of preparation example 4.

[0032] (2) Intermediate 1, ethyl chloride acrylate, and acetonitrile were dissolved in acetonitrile at a ratio of 1 mmol: 1.65 mmol: 3 mL. The mixture was reacted at 75 °C for 20 h. After the reaction was completed, the mixture was concentrated under reduced pressure. The residue was purified by column chromatography (V... 二氯甲烷 V 甲醇 =10:1~5:1), yielding cationic monomers (yield 48.7%); the NMR and mass spectrometry results of the cationic monomers were consistent with those of Preparation Example 4.

[0033] Preparation Example 7 A modified acrylamide polymer is prepared as follows: With a molar ratio of acrylamide, acrylic acid, and cationic monomer of 1:0.4:0.09, acrylamide, acrylic acid, and the cationic monomer of Preparation Example 4 were mixed, and sodium dodecyl sulfate was added at an amount of 1.5% of the mass of the cationic monomer. After mixing evenly, the mixture was added to deionized water, so that the total mass fraction of the three monomers (acrylamide, acrylic acid, and cationic monomer) in the deionized water was 36%. Under nitrogen protection, an initiator was added at an amount of 0.5% of the total mass of the three monomers. The reaction was carried out at 85°C for 9 hours. After the reaction was completed, the mixture was filtered, dried and solidified, pulverized, washed with anhydrous ethanol, and dried again to obtain the modified acrylamide polymer with a viscosity-average molecular weight of 8.32 million.

[0034] Preparation Example 8 A modified acrylamide polymer is prepared as follows: With a molar ratio of acrylamide, acrylic acid, and cationic monomer of 1:0.3:0.06, acrylamide, acrylic acid, and the cationic monomer of Preparation Example 5 were mixed, and sodium dodecyl sulfate was added at 1% of the mass of the cationic monomer. After mixing evenly, the mixture was added to deionized water to make the total mass fraction of acrylamide, acrylic acid, and cationic monomer in the deionized water 30%. Under nitrogen protection, an initiator was added at 0.3% of the total mass of the three monomers. The reaction was carried out at 80°C for 10 hours. After the reaction was completed, the mixture was filtered, dried and solidified, pulverized, washed with anhydrous ethanol, and dried again to obtain the modified acrylamide polymer with a viscosity-average molecular weight of 5.83 million.

[0035] Preparation Example 9 A modified acrylamide polymer is prepared as follows: With a molar ratio of acrylamide, acrylic acid, and cationic monomer of 1:0.6:0.12, acrylamide, acrylic acid, and the cationic monomer of Preparation Example 6 were mixed, and sodium dodecyl sulfate was added at 2% of the mass of the cationic monomer. After mixing evenly, the mixture was added to deionized water to make the total mass fraction of acrylamide, acrylic acid, and cationic monomer in the deionized water 40%. Under nitrogen protection, an initiator was added at 0.8% of the total mass of the three monomers. The reaction was carried out at 90°C for 8 hours. After the reaction was completed, the mixture was filtered, dried and solidified, pulverized, washed with anhydrous ethanol, and dried again to obtain the modified acrylamide polymer with a viscosity-average molecular weight of 9.78 million.

[0036] Preparation Example 10 The difference between Preparation Example 10 and Preparation Example 7 is that the cationic monomer was omitted, and the viscosity-average molecular weight of the resulting modified acrylamide polymer was 8.46 million.

[0037] Example 1 A high salt-resistant suspension polymer composition for fracturing, comprising, by weight, the following raw materials: 53 parts of industrial white oil, 39 parts of the modified acrylamide polymer of Preparation Example 7, 4 parts of Span 80, and 2 parts of phosphorylated bamboo fiber of Preparation Example 1.

[0038] The preparation method of the above-mentioned high salt-resistant suspension polymer composition for fracturing includes the following steps: Industrial white oil is placed in a reaction vessel, then emulsifier and phosphorylated bamboo fiber are added. After stirring at 50°C for 30 minutes, modified acrylamide polymer is added, and stirring is continued for 1.5 hours to obtain the final product.

[0039] Example 2 A high salt-resistant suspension polymer composition for fracturing, comprising, by weight, the following raw materials: 40 parts of industrial white oil, 30 parts of the modified acrylamide polymer of Preparation Example 8, 1 part of Tween 60, and 1 part of phosphorylated bamboo fiber of Preparation Example 2.

[0040] The preparation method of the above-mentioned high salt-resistant suspension polymer composition for fracturing includes the following steps: Industrial white oil is placed in a reaction vessel, then emulsifier and phosphorylated bamboo fiber are added. After stirring at 40°C for 40 minutes, modified acrylamide polymer is added, and stirring is continued for 2 hours to obtain the final product.

[0041] Example 3 A high salt-resistant suspension polymer composition for fracturing comprises, by weight, the following raw materials: 60 parts of industrial white oil, 50 parts of the modified acrylamide polymer of Preparation Example 9, 5 parts of Span 80, and 3 parts of phosphorylated bamboo fiber of Preparation Example 3.

[0042] The preparation method of the above-mentioned high salt-resistant suspension polymer composition for fracturing includes the following steps: Industrial white oil is placed in a reaction vessel, then emulsifier and phosphorylated bamboo fiber are added. After stirring at 60°C for 20 minutes, modified acrylamide polymer is added, and stirring is continued for 1 hour to obtain the final product.

[0043] Comparative Example 1 The difference between this comparative example and Example 1 is that the modified acrylamide polymer of Preparation Example 7 was replaced by Preparation Example 10.

[0044] Comparative Example 2 The difference between this comparative example and Example 1 is that bamboo fiber is used instead of the phosphorylated bamboo fiber used in Example 1.

[0045] Experimental Example 1 The phosphorylated bamboo fiber obtained in Preparation Example 1 was analyzed by Fourier transform infrared spectroscopy (FT-IR), and the results are as follows: Figure 2 As shown.

[0046] Figure 2 The image shows the infrared spectrum of the phosphorylated bamboo fiber obtained in Example 1; curve a represents the infrared spectrum of bamboo fiber, and curve b represents the infrared spectrum of phosphorylated bamboo fiber. Compared to bamboo fiber, phosphorylated bamboo fiber exhibits higher infrared spectra at 830 cm⁻¹. -1 A new characteristic absorption peak appeared, which is attributed to the stretching vibration of POC, indicating that the phosphate grafting was successful.

[0047] Experiment Example 2 Antibacterial properties: Referring to the Chinese petroleum and natural gas industry standard SY / T0532-2012 "Analysis Methods for Bacteria in Oilfield Injection Water - Extinction Dilution Method", the antibacterial rate of the compositions in the examples or comparative examples was determined, and the results are shown in Table 1.

[0048] As shown in Table 1, the antibacterial rates of Examples 1-3 are all above 99.5%, indicating that the compositions of the present invention have excellent antibacterial properties. Compared with Example 1, the antibacterial rate of Comparative Example 1 is significantly lower due to the omission of the cationic monomer, proving that the cationic monomer is the key component that imparts antibacterial activity to the composition.

[0049] Experimental Example 3 The compositions of the examples or comparative examples were prepared into an aqueous solution with a content of 0.2 wt%, and drag reduction rate, salt resistance, shear resistance and temperature resistance were tested.

[0050] Drag reduction rate: The drag reduction rate was tested according to the method specified in "SY / T6376-2008 General Technical Conditions for Fracturing Fluids", and the results are shown in Table 2.

[0051] The salt resistance, shear resistance, and temperature resistance were tested according to the oil and gas industry standard "SY / T 5107-2016 Performance Evaluation Method for Water-Based Fracturing Fluids". Details are as follows: Salt tolerance: Sodium chloride was added to the above solution to a final concentration of 1 wt%. The salt content was measured using a viscometer at room temperature (25°C) and 170 s. -1 Apparent viscosity was measured at the shear rate, and viscosity retention rate (%) was calculated. The results are shown in Table 2.

[0052] Shear resistance: tested using a rheometer at 25℃ for 170 seconds. -1 Under continuous shearing conditions for 2 hours, the apparent viscosity was measured using a viscometer, and the viscosity retention rate (%) was calculated. The results are shown in Table 2.

[0053] Temperature resistance: tested with a viscometer at 150℃ and 170s. -1Apparent viscosity was measured at the shear rate, and viscosity retention rate (%) was calculated. The results are shown in Table 2.

[0054] The formula for calculating viscosity retention rate is as follows: Viscosity retention rate (%) = Apparent viscosity after experiment η1 / Apparent viscosity before experiment η0 × 100%.

[0055] As shown in Table 2, the high salt-resistant suspension polymer compositions for fracturing prepared in Examples 1-3 of this invention exhibit high drag reduction rates and excellent performance in salt resistance, shear resistance, and temperature resistance. This indicates that by introducing specific cationic monomers into the acrylamide polymer to form a synergistic effect with phosphorylated bamboo fibers, this invention can improve the drag reduction performance and salt, shear, and temperature resistance of the compositions. Compared with Example 1, Comparative Example 1, which did not add cationic monomers, showed a significant decrease in drag reduction rate and a significant reduction in viscosity retention. Comparative Example 2, which used unphosphorylated ordinary bamboo fibers, showed a lower drag reduction rate, and its salt, shear, and temperature resistance were significantly lower than those of the examples, but higher than those of Comparative Example 1. This indicates that specific cationic monomers and phosphorylated bamboo fibers play a key role in improving the drag reduction performance and salt, shear, and temperature resistance of the compositions.

[0056] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A high salt-resistant suspension polymer composition for fracturing, characterized in that, By weight, it includes the following raw materials: 30-50 parts modified acrylamide polymer, 40-60 parts industrial white oil, 1-5 parts emulsifier, and 1-3 parts phosphorylated bamboo fiber; The preparation process of the modified acrylamide polymer is as follows: Acrylamide, acrylic acid, cationic monomer, and sodium dodecyl sulfate are added to deionized water, and an initiator is added under inert gas protection to carry out the reaction. After purification, the product is obtained. The structural formula of the cationic monomer is as follows: 。 2. The high salt-resistant suspension polymer composition for fracturing as described in claim 1, characterized in that, The molar ratio of acrylamide, acrylic acid, and cationic monomer is 1:(0.3-0.6):(0.06-0.12); the amount of sodium dodecyl sulfate added is 1-2% of the mass of the cationic monomer; the amount of initiator added is 0.3-0.8% of the total mass of acrylamide, acrylic acid, and cationic monomer; the initiator is composed of cerium ammonium nitrate and sodium bisulfite in a mass ratio of 1:1; the reaction temperature is 80-90℃, and the reaction time is 8-10h.

3. The high salt-resistant suspension polymer composition for fracturing as described in claim 2, characterized in that, The preparation process of the cationic monomer is as follows: (1) 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline and zinc iodide were added to 1,2-dichlorobenzene and heated and stirred under sealed conditions. After purification, intermediate 1 was obtained. The structural formula of intermediate 1 is as follows: ； (2) The intermediate 1 and ethyl chloride acrylate were added to acetonitrile, and the mixture was purified after reaction to obtain the cationic monomer.

4. The high salt-resistant suspension polymer composition for fracturing as described in claim 3, characterized in that, In step (1), the molar ratio of 4-cyanopyridine, 2-aminopyridine, cuprous bromide, 1,10-phenanthroline, and zinc iodide is 1:(1.1-1.3):(0.05-0.55):(0.05-0.55):(0.1-0.11); the heating and stirring reaction is carried out at a temperature of 130-135℃ for 24-28 hours.

5. The high salt-resistant suspension polymer composition for fracturing as described in claim 3, characterized in that, In step (2), the molar ratio of intermediate 1 to ethyl chloride acrylate is 1:(1.5-1.65); the reaction temperature is 70-75℃ and the reaction time is 20-24h.

6. The high salt-resistant suspension polymer composition for fracturing as described in claim 1, characterized in that, The preparation process of the phosphorylated bamboo fiber is as follows: Choline chloride, urea, and phosphorous acid were mixed and stirred to obtain a ternary reactive deep eutectic solvent; bamboo fiber was added to the ternary reactive deep eutectic solvent, and the mixture was heated and purified to obtain the phosphorylated bamboo fiber.

7. The high salt-resistant suspension polymer composition for fracturing as described in claim 6, characterized in that, The molar ratio of choline chloride, urea, and phosphorous acid is 1:2:1; the stirring temperature is 90-95℃; the ratio of bamboo fiber to ternary reactive deep eutectic solvent is 1g:(40-45)mL; the heating reaction temperature is 130-150℃, and the time is 2-4h.

8. The high salt-resistant suspension polymer composition for fracturing as described in claim 1, characterized in that, The emulsifier is Span 80 or Tween 60.

9. A method for preparing a high salt-resistant suspension polymer composition for fracturing according to any one of claims 1-8, characterized in that, Includes the following steps: Add emulsifier and phosphorylated bamboo fiber to industrial white oil, stir, then add modified acrylamide polymer and continue stirring to obtain the final product.

10. The method for preparing the high salt-resistant suspension polymer composition for fracturing as described in claim 9, characterized in that, The stirring temperature is 40-60℃, and the stirring time is 20-40 minutes; the stirring time is 1-2 hours.

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