High-salt-resistant drag reducer and preparation method thereof

Abstract

This invention relates to the field of oilfield chemistry and discloses a high-salt-resistant drag-reducing agent and its preparation method. The preparation method involves adding isopropanol to deionized water and stirring for 5-10 minutes to disperse it. Then, an amide-type quaternary ammonium salt, naphthyl-modified cyclodextrin, and disodium hydroxyethylidene diphosphonate are added, and stirring is continued for 10-15 minutes. Finally, triethanolamine is added, and stirring is performed for 3-5 minutes. The mixture is then filtered to obtain the high-salt-resistant drag-reducing agent. This invention utilizes the synergistic effect of the amide-type quaternary ammonium salt, naphthyl-modified cyclodextrin, and disodium hydroxyethylidene diphosphonate to construct a stable supramolecular worm micelle drag-reducing system. This results in a high drag reduction rate under freshwater conditions and maintains an extremely high drag reduction retention rate in high-salinity formation water environments with low core damage. The agent can be prepared using freshwater or directly using seawater or high-salinity reinjection water, making it suitable for fracturing operations in arid regions with scarce freshwater and offshore oilfields.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to a high salt-resistant drag-reducing agent and its preparation method. Background Technology

[0002] With the deepening exploration and development of unconventional oil and gas reservoirs, the operating environment of oil, gas, and water wells is becoming increasingly complex. Formation water with high salinity and high calcium and magnesium ion content, along with oilfield reinjection water, is widely used in fracturing fluid preparation, placing more stringent demands on the salt resistance of drag-reducing agents used in fracturing fluids. Currently, most commonly used drag-reducing agents in oilfields are polyacrylamide copolymers, which rely on the extension of long polymer chains to achieve drag reduction. However, in high-salt environments, salt ions compress the electric double layer, causing the polymer chains to coil and entangle, significantly reducing drag reduction performance. Furthermore, existing drag-reducing agents generally suffer from insufficient synergistic mechanisms and sensitivity to calcium and magnesium ions, failing to simultaneously meet the engineering requirements of high drag reduction rates, high temperature and salt resistance, and low formation damage. Therefore, avoiding this phenomenon is key to solving the problem. For example, patent application CN115505385A discloses a high-efficiency anti-swelling and drag-reducing agent and its preparation method suitable for water-sensitive conglomerate reservoirs. The high-efficiency anti-swelling and drag-reducing agent described in this invention has good sand-carrying and anti-swelling performance, high temperature resistance, strong water solubility, and low cost. However, its salt resistance is limited, especially its stability is insufficient in high calcium and magnesium ion environment, making it difficult to meet the long-term use requirements of high mineralization strata. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high salt resistance drag reducer and its preparation method. The high salt resistance drag reducer prepared by the present invention has good drag reduction performance, temperature and salt resistance performance and low formation damage characteristics.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a high salt-resistant drag-reducing agent, comprising the following weight components: 15-20 parts by weight of an amide-type quaternary ammonium salt, 3-5 parts by weight of naphthyl-modified cyclodextrin, 4-6 parts by weight of isopropanol, 2-3 parts by weight of disodium hydroxyethylidene diphosphonate, 0.8-1 parts by weight of triethanolamine, and 50-60 parts by weight of deionized water; The amide-type quaternary ammonium salt is prepared by reacting terephthaloyl chloride with 3-diethylaminopropylamine and then reacting it with 1-bromododecane; The naphthyl-modified cyclodextrin is prepared by reacting 1,6-dihydroxynaphthalene with epichlorohydrin to obtain glycidyl ether, which is then modified with 3-aminopropyltriethoxysilane and finally grafted with hydroxypropyl-β-cyclodextrin.

[0005] Furthermore, the preparation method of the amide-type quaternary ammonium salt is as follows: Step 1: Under nitrogen gas protection and 0-5℃ ice-water bath conditions, add 15-20 mL of anhydrous dichloromethane solution and 2-2.1 g of terephthaloyl chloride to the reactor and mix well. Then, dissolve 2.6-2.7 g of 3-diethylaminopropylamine and 2-2.05 g of triethylamine in 30-40 mL of anhydrous dichloromethane and add it dropwise to the reactor. After the addition is complete, heat to room temperature and stir to carry out the reaction. After the reaction is completed, wash the organic phase with water and saturated brine in sequence, dry, filter, and concentrate under reduced pressure to obtain the diamine ditertiary intermediate. In the above steps, the 3-diethylaminopropylamine molecule has a primary amine and a tertiary amine at each end. Due to the small steric hindrance and much stronger nucleophilicity of the primary amine than the tertiary amine, the nitrogen atom of the primary amine will actively attack the carbonyl carbon on the terephthaloyl chloride, undergoing a nucleophilic acyl substitution reaction, removing hydrogen chloride, and forming an amide bond. By controlling the amount of 3-diethylaminopropylamine to be 2.05-2.10 times (molar ratio) of terephthaloyl chloride, and by slowly adding the amine / triethylamine mixed solution dropwise to the acyl chloride solution, it is ensured that the acyl chloride in the system is always in a relatively excess state, promoting the reaction of the two primary amines with the two acyl chloride groups respectively, thereby avoiding the formation of monoamide byproducts. At the same time, the tertiary amine does not react under the reaction conditions, ensuring the selectivity of the reaction, and finally forming a symmetrical structure centered on the benzene ring, obtaining the diamide ditertiary amine intermediate.

[0006] Step 2: Add the diamine intermediate and 1-bromododecane to anhydrous ethanol, stir and mix, and react at 80-85℃ for 12-16 h. After the reaction is completed, cool to room temperature, precipitate the solid, filter, recrystallize with isopropanol 2-3 times, and dry under vacuum to obtain the amide-type quaternary ammonium salt.

[0007] In the above steps, the lone pairs of electrons on the tertiary amine nitrogen atoms at both ends of the diamine intermediate actively attack the terminal carbon atom of 1-bromododecane, squeezing out the bromide ion and forming a carbon-nitrogen single bond, thus forming an amide-type quaternary ammonium salt with two positive charge centers.

[0008] Furthermore, the reaction time in step one is 8-12 hours.

[0009] Furthermore, in step two, the ratio of anhydrous ethanol, diamine diamine intermediate, and 1-bromododecane is 50-60 mL: 2.8-2.9 g: 3.5-3.6 g.

[0010] Furthermore, the preparation method of the naphthyl-modified cyclodextrin is as follows: S1: Under nitrogen protection, 1,6-dihydroxynaphthalene, epichlorohydrin, and tetramethylammonium bromide are added to the reactor and mixed evenly. Then, the temperature is raised to 65-70℃, sodium hydroxide is added, and the mixture is stirred for 3-4 hours. After the reaction is completed, the mixture is filtered, neutralized with acetic acid, and washed with deionized water until neutral. The solvent is removed to obtain the crude product. The crude product is then dissolved in methyl isobutyl ketone, heated to 105-110℃, polyethylene glycol is added, and a 50% sodium hydroxide aqueous solution is added dropwise. The reaction is continued for 3-4 hours. The mixture is then washed with water, the solvent is removed, and the mixture is distilled to obtain 1,6-dihydroxynaphthalene glycidyl ether. In the above steps, by reacting 1,6-dihydroxynaphthalene with epichlorohydrin under alkaline conditions in a Williamson ether synthesis reaction, highly reactive epoxy groups were successfully introduced at both ends of the naphthalene ring to obtain 1,6-dihydroxynaphthalene glycidyl ether, which provides reactive sites for subsequent grafting of silane coupling agents.

[0011] S2: Under nitrogen protection, 1,6-dihydroxynaphthalene glycidyl ether was added to anhydrous toluene solvent and stirred until completely dissolved. Then, 3-aminopropyltriethoxysilane was added dropwise. After the addition was complete, the mixture was stirred at 60-80℃ for 6-12 hours. After the reaction was completed, the mixture was distilled under reduced pressure, washed and dried to obtain the naphthyl modified coupling agent. In the above steps, 3-aminopropyltriethoxysilane has an active primary amine at one end. This primary amine attacks the epoxy group in the product of the previous step, and an epoxy ring-opening addition reaction occurs. The primary amine is converted into a secondary amine, and the epoxy group is opened to generate a secondary hydroxyl group. The siloxane group is linked to the naphthyl ring skeleton through a stable chemical bond, thus obtaining a naphthyl-modified coupling agent.

[0012] S3: Under nitrogen protection, add 50-60 mL of anhydrous N,N-dimethylformamide and 6-6.1 g of hydroxypropyl-β-cyclodextrin to the reactor and stir at 50-60 °C until completely dissolved. Then, dissolve 2.5-2.6 g of naphthyl-modified coupling agent in 25-30 mL of anhydrous N,N-dimethylformamide and add it dropwise to the reactor. After the addition is complete, add 0.5-0.6 mL of triethylamine to the reactor and stir the reaction at 80-100 °C for 12-16 h. During the reaction, continuously purge with nitrogen to carry away the generated ethanol byproduct from the reaction system. After the reaction is complete, cool to room temperature and slowly drop the reaction solution into 300-500 mL of acetone to precipitate. Wash with acetone 2-3 times and dry to obtain naphthyl-modified cyclodextrin.

[0013] In the above steps, under heating and alkaline catalysis of triethylamine, the triethoxysilyl group at the end of the naphthyl-modified coupling agent undergoes an alcoholysis condensation reaction. During the process, nitrogen gas is continuously introduced to carry out the generated ethanol byproduct, pushing the reaction equilibrium to the forward direction and forming a Si-OC bond. This firmly anchors the naphthyl group, which has extremely strong hydrophobicity and π-π stacking interaction, to the outer edge of the cyclodextrin, thus obtaining naphthyl-modified cyclodextrin.

[0014] Further, the ratio of 1,6-dihydroxynaphthalene, epichlorohydrin, tetramethylammonium bromide, sodium hydroxide, methyl isobutyl ketone, polyethylene glycol, and a 50% sodium hydroxide aqueous solution in S1 is 4-4.1g:45-46g:0.06-0.07g:2.4-2.5g:80-100mL:0.23-0.27g:3.4-3.8mL.

[0015] Furthermore, the ratio of anhydrous toluene, 1,6-dihydroxynaphthalene glycidyl ether, and 3-aminopropyltriethoxysilane in S2 is 20-30 mL: 3.5-3.6 g: 5.9-6 g.

[0016] Furthermore, the preparation method of the high salt resistance drag reducer is as follows: add isopropanol to deionized water, stir for 5-10 min to disperse it, then add amide-type quaternary ammonium salt, naphthyl-modified cyclodextrin, and disodium hydroxyethylidene diphosphonate, continue stirring for 10-15 min, finally add triethanolamine, stir for 3-5 min, filter, and obtain the high salt resistance drag reducer.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention constructs a stable supramolecular worm micelle drag-reducing system through the synergistic effect of amide-type quaternary ammonium salt, naphthyl-modified cyclodextrin, and disodium hydroxyethylidene bisphosphonate. The amide-type quaternary ammonium salt possesses a rigid aromatic amide backbone and dual cation centers; the positive charge provides strong electrostatic repulsion, allowing the molecular chains to fully extend in aqueous solution, which is beneficial for the formation and stability of worm micelles and provides highly efficient turbulence suppression. The hydrophobic cavity in the naphthyl-modified cyclodextrin can encapsulate the hydrophobic tail chain of the amide-type quaternary ammonium salt, forming dynamic physical cross-linking points, regulating the micelle structure. π-π stacking can occur between naphthyl groups, further enhancing network strength and improving the structural stability of micelles under high temperature and high salt environments, preventing molecular chain curling and micelle disintegration. Disodium hydroxyethylidene bisphosphonate can efficiently chelate Ca... 2+ Mg 2+The use of high-valence metal ions eliminates the destructive effect of divalent ions on the drag reduction system at the source, further enhancing salt tolerance. The synergistic effect of the components results in a high drag reduction rate under freshwater conditions and maintains an extremely high drag reduction retention rate even in high-salinity formation water environments, with minimal core damage. It can be prepared using freshwater, seawater, or high-salinity reinjection water, making it suitable for arid regions with scarce freshwater and offshore oilfield fracturing operations. Detailed Implementation

[0018] 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.

[0019] The reagents used in the following specific embodiments are of analytical grade. Additionally: Polyethylene glycol: PEG-400.

[0020] Example 1 (1) Under nitrogen gas protection and 0℃ ice-water bath conditions, 15 mL of anhydrous dichloromethane solution and 2 g of terephthaloyl chloride were added to the reactor and mixed evenly. Then, 2.6 g of 3-diethylaminopropylamine and 2 g of triethylamine were dissolved in 30 mL of anhydrous dichloromethane and added dropwise to the reactor. After the addition was completed, the temperature was raised to room temperature and the reaction was stirred for 8 h. After the reaction was completed, the organic phase was washed with water and saturated brine in sequence, dried, filtered, and concentrated under reduced pressure to obtain the diamine intermediate. (2) Add 2.8 g of diamine intermediate and 3.5 g of 1-bromododecane to 50 mL of anhydrous ethanol, stir and mix, and react at 80 °C for 12 h. After the reaction is completed, cool to room temperature, precipitate solid, filter, recrystallize twice with isopropanol, and dry under vacuum to obtain amide-type quaternary ammonium salt. (3) Under nitrogen protection, 4g of 1,6-dihydroxynaphthalene, 45g of epichlorohydrin and 0.06g of tetramethylammonium bromide were added to the reactor and mixed evenly. Then the temperature was raised to 65°C and 2.4g of sodium hydroxide was added. The mixture was stirred for 3h. After the reaction was completed, the mixture was filtered, neutralized with acetic acid and washed with deionized water until neutral. The solvent was removed to obtain the crude product. The crude product was then dissolved in 80mL of methyl isobutyl ketone and heated to 105°C. 0.23g of polyethylene glycol was added and 3.4mL of 50% sodium hydroxide aqueous solution was added dropwise. The reaction was continued for 3h. The mixture was then washed with water to remove the solvent and distilled to obtain 1,6-dihydroxynaphthalene glycidyl ether. (4) Under nitrogen protection, 3.5 g of 1,6-dihydroxynaphthalene glycidyl ether was added to 20 mL of anhydrous toluene solvent and stirred until completely dissolved. Then, 5.9 g of 3-aminopropyltriethoxysilane was added dropwise. After the addition was complete, the mixture was stirred at 60 °C for 6 h. After the reaction was completed, the mixture was distilled under reduced pressure, washed and dried to obtain the naphthyl modified coupling agent. (5) Under nitrogen protection, 50 mL of anhydrous N,N-dimethylformamide and 6 g of hydroxypropyl-β-cyclodextrin were added to the reactor and stirred at 50 °C until completely dissolved. Then, 2.5 g of naphthyl-modified coupling agent was dissolved in 25 mL of anhydrous N,N-dimethylformamide and added dropwise to the reactor. After the addition was complete, 0.5 mL of triethylamine was added to the reactor and stirred at 80 °C for 12 h. Nitrogen gas was continuously introduced during the reaction to carry out the generated ethanol byproducts from the reaction system. After the reaction was completed, the mixture was cooled to room temperature and the reaction solution was slowly added dropwise to 300 mL of acetone to precipitate the precipitate. The precipitate was washed twice with acetone and dried to obtain naphthyl-modified cyclodextrin. (6) Add 4 parts by weight of isopropanol to 50 parts by weight of deionized water, stir for 5 min to disperse it, then add 15 parts by weight of amide-type quaternary ammonium salt, 3 parts by weight of naphthyl-modified cyclodextrin, and 2 parts by weight of disodium hydroxyethylidene diphosphonate, continue stirring for 10 min, finally add 0.8 parts by weight of triethanolamine, stir for 3 min, filter, and obtain a high salt resistance drag reducer.

[0021] Example 2 (1) Under nitrogen gas protection and 5℃ ice-water bath conditions, 20mL of anhydrous dichloromethane solution and 2.1g of terephthaloyl chloride were added to the reactor and mixed evenly. Then, 2.7g of 3-diethylaminopropylamine and 2.05g of triethylamine were dissolved in 40mL of anhydrous dichloromethane and added dropwise to the reactor. After the addition was completed, the temperature was raised to room temperature and the reaction was stirred for 12h. After the reaction was completed, the organic phase was washed with water and saturated brine in sequence, dried, filtered, and concentrated under reduced pressure to obtain the diamine intermediate. (2) Add 2.9 g of diamine intermediate and 3.6 g of 1-bromododecane to 60 mL of anhydrous ethanol, stir and mix, react at 85 °C for 16 h, after the reaction is completed, cool to room temperature, precipitate solid, filter, recrystallize 3 times with isopropanol, and dry under vacuum to obtain amide-type quaternary ammonium salt. (3) Under nitrogen protection, 4.1 g of 1,6-dihydroxynaphthalene, 46 g of epichlorohydrin and 0.07 g of tetramethylammonium bromide were added to the reactor and mixed evenly. Then the temperature was raised to 70°C and 2.5 g of sodium hydroxide was added. The mixture was stirred and reacted for 4 h. After the reaction was completed, the mixture was filtered, neutralized with acetic acid, washed with deionized water until neutral, and the solvent was removed to obtain the crude product. The crude product was then dissolved in 100 mL of methyl isobutyl ketone, heated to 110°C, 0.27 g of polyethylene glycol was added, and 3.8 mL of 50% sodium hydroxide aqueous solution was added dropwise. The reaction was continued for 4 h. Then the mixture was washed with water, the solvent was removed, and the mixture was distilled to obtain 1,6-dihydroxynaphthalene glycidyl ether. (4) Under nitrogen protection, 3.6 g of 1,6-dihydroxynaphthalene glycidyl ether was added to 30 mL of anhydrous toluene solvent and stirred until completely dissolved. Then, 6 g of 3-aminopropyltriethoxysilane was added dropwise. After the addition was complete, the mixture was stirred at 80 °C for 12 h. After the reaction was completed, the mixture was distilled under reduced pressure, washed and dried to obtain the naphthyl modified coupling agent. (5) Under nitrogen protection, 60 mL of anhydrous N,N-dimethylformamide and 6.1 g of hydroxypropyl-β-cyclodextrin were added to the reactor and stirred at 60 °C until completely dissolved. Then, 2.6 g of naphthyl-modified coupling agent was dissolved in 30 mL of anhydrous N,N-dimethylformamide and added dropwise to the reactor. After the addition was complete, 0.6 mL of triethylamine was added to the reactor and stirred at 100 °C for 16 h. Nitrogen gas was continuously introduced during the reaction to carry out the generated ethanol byproducts from the reaction system. After the reaction was completed, the mixture was cooled to room temperature and the reaction solution was slowly added dropwise to 500 mL of acetone to precipitate the precipitate. The precipitate was washed three times with acetone and dried to obtain naphthyl-modified cyclodextrin. (6) Add 6 parts by weight of isopropanol to 60 parts by weight of deionized water, stir for 10 min to disperse it, then add 20 parts by weight of amide-type quaternary ammonium salt, 5 parts by weight of naphthyl-modified cyclodextrin, and 3 parts by weight of disodium hydroxyethylidene diphosphonate, continue stirring for 15 min, finally add 1 part by weight of triethanolamine, stir for 5 min, filter, and obtain a high salt resistance drag reducer.

[0022] Example 3 (1) Under nitrogen gas protection and 2℃ ice-water bath conditions, 18 mL of anhydrous dichloromethane solution and 2.05 g of terephthaloyl chloride were added to the reactor and mixed evenly. Then, 2.65 g of 3-diethylaminopropylamine and 2.02 g of triethylamine were dissolved in 35 mL of anhydrous dichloromethane and added dropwise to the reactor. After the addition was completed, the temperature was raised to room temperature and the reaction was stirred for 10 h. After the reaction was completed, the organic phase was washed with water and saturated brine in sequence, dried, filtered, and concentrated under reduced pressure to obtain the diamine intermediate. (2) Add 2.85 g of diamine intermediate and 3.55 g of 1-bromododecane to 55 mL of anhydrous ethanol, stir and mix, and react at 82 °C for 14 h. After the reaction is completed, cool to room temperature, precipitate solid, filter, recrystallize twice with isopropanol, and dry under vacuum to obtain amide-type quaternary ammonium salt. (3) Under nitrogen protection, 4.05 g of 1,6-dihydroxynaphthalene, 45.5 g of epichlorohydrin and 0.06 g of tetramethylammonium bromide were added to the reactor and mixed evenly. Then the temperature was raised to 68°C and 2.45 g of sodium hydroxide was added. The mixture was stirred and reacted for 3.5 h. After the reaction was completed, the mixture was filtered, neutralized with acetic acid, washed with deionized water until neutral, and the solvent was removed to obtain the crude product. The crude product was then dissolved in 90 mL of methyl isobutyl ketone, heated to 108°C, 0.25 g of polyethylene glycol was added, and 3.6 mL of 50% sodium hydroxide aqueous solution was added dropwise. The reaction was continued for 3.5 h. The mixture was then washed with water, the solvent was removed, and the mixture was distilled to obtain 1,6-dihydroxynaphthalene glycidyl ether. (4) Under nitrogen protection, 3.55 g of 1,6-dihydroxynaphthalene glycidyl ether was added to 25 mL of anhydrous toluene solvent and stirred until completely dissolved. Then, 5.95 g of 3-aminopropyltriethoxysilane was added dropwise. After the addition was complete, the mixture was stirred at 70 °C for 9 h. After the reaction was completed, the mixture was distilled under reduced pressure, washed and dried to obtain the naphthyl modified coupling agent. (5) Under nitrogen protection, 55 mL of anhydrous N,N-dimethylformamide and 6.05 g of hydroxypropyl-β-cyclodextrin were added to the reactor and stirred at 55 °C until completely dissolved. Then, 2.55 g of naphthyl-modified coupling agent was dissolved in 28 mL of anhydrous N,N-dimethylformamide and added dropwise to the reactor. After the addition was complete, 0.55 mL of triethylamine was added to the reactor and stirred at 90 °C for 14 h. Nitrogen gas was continuously introduced during the reaction to carry out the generated ethanol byproducts from the reaction system. After the reaction was completed, the mixture was cooled to room temperature and the reaction solution was slowly added dropwise to 400 mL of acetone to precipitate the precipitate. The precipitate was washed three times with acetone and dried to obtain naphthyl-modified cyclodextrin. (6) Add 5 parts by weight of isopropanol to 55 parts by weight of deionized water, stir for 8 minutes to disperse it, then add 18 parts by weight of amide-type quaternary ammonium salt, 4 parts by weight of naphthyl-modified cyclodextrin, and 2 parts by weight of disodium hydroxyethylidene diphosphonate, continue stirring for 12 minutes, finally add 0.9 parts by weight of triethanolamine, stir for 4 minutes, filter, and obtain a high salt resistance drag reducer.

[0023] Comparative Example 1 The main difference between this comparative example and Example 3 is that a ditertiary amine diamide intermediate is used instead of an amide-type quaternary ammonium salt.

[0024] Comparative Example 2 The main difference between this comparative example and Example 3 is that hydroxypropyl-β-cyclodextrin is used instead of naphthyl-modified cyclodextrin.

[0025] Comparative Example 3 The main difference between this comparative example and Example 3 is that disodium hydroxyethylidene diphosphonate is not added.

[0026] Comparative Example 4 The main difference between this comparative example and Example 3 is that 1-bromododecane in step (2) is replaced with an equimolar amount of 1-bromobutane, thus changing the length of the hydrophobic chain of the amide-type quaternary ammonium salt.

[0027] Performance testing The high salt resistance drag reducers prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests.

[0028] (1) Drag reduction rate test: Referring to SY / T5107-2016 "Evaluation method of performance of water-based fracturing fluid", an indoor pipeline drag reduction test device was used. The test temperature was 25℃, the pipe diameter was 25mm, and the flow rate was 1.5m / s. The high salt resistance drag reduction agent prepared in Examples 1-3 and Comparative Examples 1-4 was dissolved in deionized water at an addition of 0.15wt%, and the drag reduction rate was tested after stirring evenly.

[0029] (2) Temperature and salt resistance test: Prepare simulated formation water with a total mineralization of 100,000 mg / L (NaCl, CaCl2, MgCl2 mass ratio of 10:1:0.5). Add the high salt resistance drag-reducing agent prepared in Examples 1-3 and Comparative Examples 1-4 to the simulated formation water at a dosage of 0.15 wt%, and stir until completely dissolved. Aging is carried out in a roller furnace at 80℃ for 2 hours, followed by natural cooling to 25℃. The drag reduction rate retention rate (relative to normal temperature freshwater conditions) is then tested.

[0030] (3) Core damage test: Referring to the standard SY / T7627-2021 "Technical Requirements for Water-based Fracturing Fluid", the damage rate of the high salt resistance drag-reducing agent prepared in Examples 1-3 and Comparative Examples 1-4 to the core was tested respectively.

[0031] The test results are shown in Table 1.

[0032] Table 1: Performance Tests Example 1 72.5 87.6 11.8 Example 2 74.1 89.0 11.2 Example 3 76.3 90.3 10.5 Comparative Example 1 38.6 45.9 27.5 Comparative Example 2 50.7 58.4 21.3 Comparative Example 3 73.1 50.9 24.0 Comparative Example 4 46.8 54.7 22.7 As can be seen from Table 1, the high salt resistance drag reducers prepared in Examples 1-3 have good drag reduction performance, temperature and salt resistance performance and low formation damage characteristics.

[0033] The comparison shows that Comparative Example 1, which uses a di-tertiary amine diamide intermediate instead of an amide-type quaternary ammonium salt, lacks a strong cationic center and cannot expand through electrostatic repulsion. It also lacks a long hydrophobic carbon chain, preventing the intermediate from inserting into the cavity of the cyclodextrin, resulting in a deficiency of the supramolecular network structure and a decrease in performance. Comparative Example 2, which uses hydroxypropyl-β-cyclodextrin instead of naphthyl-modified cyclodextrin, suffers from the lack of naphthyl groups. Naphthyl groups possess strong aromatic ring hydrophobicity and π-π stacking interactions. Without naphthyl groups, relying solely on the ordinary cavity inclusion function of hydroxypropyl-β-cyclodextrin, the physical cross-linking points easily dissociate under the impact of 80°C and extremely high salinity, leading to the collapse of the supramolecular network structure and a decrease in performance. Comparative Example 3, which does not contain disodium hydroxyethylidene diphosphonate, lacks calcium and magnesium ions in deionized water, thus its drag reduction rate is close to that of the examples. However, in high-salinity simulated formation water, the Ca... 2+ Mg 2+ Unable to be chelated, directly disrupting the dynamic network structure of worm micelles, leading to performance degradation in high-salt environments; Comparative Example 4 altered the length of the hydrophobic chain of the amide-type quaternary ammonium salt, and the carbon chain of 1-bromobutane was too short, resulting in weak hydrophobicity and difficulty in forming effective long-range worm micelles, with an incomplete drag-reducing structure, thus causing a performance degradation.

[0034] 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.

[0035] 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.

[0036] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A high salt-resistant drag-reducing agent, characterized in that, It includes the following components by weight: 15-20 parts by weight of amide-type quaternary ammonium salt, 3-5 parts by weight of naphthyl-modified cyclodextrin, 4-6 parts by weight of isopropanol, 2-3 parts by weight of disodium hydroxyethylidene diphosphonate, 0.8-1 parts by weight of triethanolamine, and 50-60 parts by weight of deionized water. The amide-type quaternary ammonium salt is prepared by reacting terephthaloyl chloride with 3-diethylaminopropylamine and then reacting it with 1-bromododecane; The naphthyl-modified cyclodextrin is prepared by reacting 1,6-dihydroxynaphthalene with epichlorohydrin to obtain glycidyl ether, which is then modified with 3-aminopropyltriethoxysilane and finally grafted with hydroxypropyl-β-cyclodextrin. The preparation method of the amide-type quaternary ammonium salt is as follows: Step 1: Under nitrogen gas protection and 0-5℃ ice-water bath conditions, add 15-20 mL of anhydrous dichloromethane solution and 2-2.1 g of terephthaloyl chloride to the reactor and mix well. Then, dissolve 2.6-2.7 g of 3-diethylaminopropylamine and 2-2.05 g of triethylamine in 30-40 mL of anhydrous dichloromethane and add it dropwise to the reactor. After the addition is complete, heat to room temperature and stir to carry out the reaction. After the reaction is completed, wash the organic phase with water and saturated brine in sequence, dry, filter, and concentrate under reduced pressure to obtain the diamine ditertiary intermediate. Step 2: Add the diamine intermediate and 1-bromododecane to anhydrous ethanol, stir and mix, and react at 80-85℃ for 12-16h. After the reaction is completed, cool to room temperature, precipitate the solid, filter, recrystallize with isopropanol 2-3 times, and dry under vacuum to obtain the amide-type quaternary ammonium salt. The preparation method of the naphthyl-modified cyclodextrin is as follows: S1: Under nitrogen protection, 1,6-dihydroxynaphthalene, epichlorohydrin, and tetramethylammonium bromide are added to the reactor and mixed evenly. Then, the temperature is raised to 65-70℃, sodium hydroxide is added, and the mixture is stirred for 3-4 hours. After the reaction is completed, the mixture is filtered, neutralized with acetic acid, and washed with deionized water until neutral. The solvent is removed to obtain the crude product. The crude product is then dissolved in methyl isobutyl ketone, heated to 105-110℃, polyethylene glycol is added, and a 50% sodium hydroxide aqueous solution is added dropwise. The reaction is continued for 3-4 hours. The mixture is then washed with water, the solvent is removed, and the mixture is distilled to obtain 1,6-dihydroxynaphthalene glycidyl ether. S2: Under nitrogen protection, 1,6-dihydroxynaphthalene glycidyl ether was added to anhydrous toluene solvent and stirred until completely dissolved. Then, 3-aminopropyltriethoxysilane was added dropwise. After the addition was complete, the mixture was stirred at 60-80℃ for 6-12 hours. After the reaction was completed, the mixture was distilled under reduced pressure, washed and dried to obtain the naphthyl modified coupling agent. S3: Under nitrogen protection, add 50-60 mL of anhydrous N,N-dimethylformamide and 6-6.1 g of hydroxypropyl-β-cyclodextrin to the reactor and stir at 50-60℃ until completely dissolved. Then, dissolve 2.5-2.6 g of naphthyl-modified coupling agent in 25-30 mL of anhydrous N,N-dimethylformamide and add it dropwise to the reactor. After the addition is complete, add 0.5-0.6 mL of triethylamine to the reactor and stir the reaction at 80-100℃ for 12-16 h. During the reaction, continuously purge with nitrogen to carry the generated ethanol byproduct out of the reaction system. After the reaction is complete, cool to room temperature and slowly drop the reaction solution into 300-500 mL of acetone to precipitate. Wash with acetone 2-3 times and dry to obtain naphthyl-modified cyclodextrin. In step two, the ratio of anhydrous ethanol, diamine diamine intermediate, and 1-bromododecane is 50-60 mL: 2.8-2.9 g: 3.5-3.6 g. The ratio of 1,6-dihydroxynaphthalene, epichlorohydrin, tetramethylammonium bromide, sodium hydroxide, methyl isobutyl ketone, polyethylene glycol, and a 50% sodium hydroxide aqueous solution in S1 is 4-4.1g:45-46g:0.06-0.07g:2.4-2.5g:80-100mL:0.23-0.27g:3.4-3.8mL. The ratio of anhydrous toluene, 1,6-dihydroxynaphthalene glycidyl ether, and 3-aminopropyltriethoxysilane in S2 is 20-30 mL: 3.5-3.6 g: 5.9-6 g.

2. The high salt resistance drag reducer according to claim 1, characterized in that, The reaction time in step one is 8-12 hours.

3. A method for preparing a high salt-resistant drag-reducing agent as described in any one of claims 1-2, characterized in that, The preparation method of the high salt resistance drag reducer is as follows: add isopropanol to deionized water, stir for 5-10 min to disperse it, then add amide-type quaternary ammonium salt, naphthyl-modified cyclodextrin, and disodium hydroxyethylidene diphosphonate, continue stirring for 10-15 min, finally add triethanolamine, stir for 3-5 min, filter, and obtain the high salt resistance drag reducer.