Salt-resistant gelling agent, preparation method and application thereof

Abstract

The present application relates to a kind of anti-salt thickening agent and its preparation method and application, belong to the technical field of oil fracturing fluid processing.Solve the technical problems of low economic benefit, high cost and big environmental protection pressure in prior art that fracturing flowback fluid must be treated before being reused, such as metal ions, solid impurities and the like.The anti-salt thickening agent of the present application, by weight, raw materials include acrylamide 53-60 parts, acrylic acid 45-55 parts, 2-acrylamide-2-methylpropane sulfonic acid 1.5-2 parts, styrene 0.1-1 part and modified polyethylene glycol 3-6 parts.The anti-salt thickening agent, the introduced sulfonic acid group, benzene ring and tannic acid, have excellent salt resistance and stability, can resist fracturing flowback fluid with total salinity ≤1wppm, calcium and magnesium ion concentration ≤500ppm, and fracturing flowback fluid with iron ion concentration within 50ppm, providing a basis for direct use of fracturing flowback fluid.

Description

Technical Field

[0001] This invention belongs to the field of petroleum fracturing fluid treatment technology, specifically relating to an anti-salt thickener, its preparation method and application, and particularly to the application of the anti-salt thickener in the reuse of fracturing flowback fluid. Background Technology

[0002] Fracturing is one of the main measures for increasing oil and gas field production. Fracturing fluid is an essential working medium in the fracturing process. However, with the large-scale development of oil and gas fields, the total amount of fracturing flowback fluid has increased significantly. This flowback fluid has a complex composition, high pollutant content, and poor biodegradability, making it a significant factor polluting the environment around the well site. Recycling fracturing flowback fluid is an effective way to solve this problem.

[0003] In existing technologies, the recycling of fracturing flowback fluid, both domestically and internationally, mostly involves first treating the flowback fluid for metal ions (calcium, magnesium, iron, etc.) and solid impurities, and then using the treated flowback fluid with low calcium and magnesium content and extremely low iron ion content to prepare a new thickener for reuse. However, in practical applications, the need to treat the fracturing flowback fluid before reuse leads to high costs for pipeline construction and transportation, and limited storage space, significantly increasing application costs and placing considerable environmental pressure on the system. Summary of the Invention

[0004] In view of this, the present invention provides an anti-salt thickener, its preparation method and application, in order to solve the technical problems of low economic efficiency, high cost and great environmental pressure that exist in the prior art of fracturing flowback fluid which requires the prior treatment of metal ions (calcium, magnesium and iron) and solid impurities.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0006] In a first aspect, the present invention provides an anti-salt thickener, comprising, by weight, 53-60 parts of acrylamide, 45-55 parts of acrylic acid, 1.5-2 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.1-1 parts of styrene, and 3-6 parts of modified polyethylene glycol.

[0007] Preferably, the anti-salt thickener comprises, by weight, 55 parts acrylamide, 50 parts acrylic acid, 1.5 parts 2-acrylamide-2-methylpropanesulfonic acid, 0.6 parts styrene, and 5 parts modified polyethylene glycol.

[0008] Preferably, the modified polyethylene glycol is tannic acid-modified polyethylene glycol;

[0009] More preferably, the preparation method of the tannic acid-modified polyethylene glycol includes the following steps:

[0010] A1: Take dried polyethylene glycol and dissolve it in dichloromethane by stirring. Add triethylamine and stir to dissolve to obtain mixed solution one.

[0011] A2: Dissolve p-toluenesulfonyl chloride in dichloromethane, stir and mix well to obtain mixed solution two;

[0012] A3: Under ice-water bath conditions, add mixture two dropwise to mixture one. After the addition is complete, keep the mixture at 20-25℃ for 22-24 hours. After the reaction is complete, wash with hydrochloric acid 2-3 times, concentrate the reaction solution, precipitate with cold diethyl ether at 0-3℃, filter to obtain a solid, dry, and obtain intermediate product one.

[0013] A4: Add intermediate product one and ammonia water to the reaction vessel and keep it at 120-140℃ for 5-8 hours. Cool to room temperature, extract the reaction solution with dichloromethane multiple times, combine the organic phases, add sodium hydroxide aqueous solution to the organic phase, stir, filter, and wash the solid with distilled water until neutral to obtain intermediate product two.

[0014] A5: Dissolve the prepared intermediate product II in distilled water, adjust the pH to 7-8, add tannic acid, and stir the reaction at 50-60℃ for 12-24 hours. After the reaction is complete, evaporate the reaction solution to obtain modified polyethylene glycol.

[0015] Preferably, in step A1, the polyethylene glycol is one or more of PEG-3000 and PEG-4000.

[0016] Preferably, in step A1, the molar ratio of polyethylene glycol to triethylamine is 1:10-12.

[0017] Preferably, in step A1, the mass ratio of polyethylene glycol to dichloromethane is 1:2-2.5.

[0018] Preferably, in step A2, the molar ratio of p-toluenesulfonyl chloride to polyethylene glycol is 8-10:1.

[0019] Preferably, in step A2, the mass ratio of p-toluenesulfonyl chloride to dichloromethane is 1:2.5-3.

[0020] Preferably, in step A2, the concentration method is distillation or rotary evaporation; more preferably, the distillation is vacuum distillation.

[0021] Preferably, in step A3, the dripping rate is 2-3 d / s.

[0022] Preferably, in step A3, the concentration of the hydrochloric acid is 3 mol / L.

[0023] Preferably, in step A3, the volume of the cold ether is 5-6 times the volume of the reaction liquid.

[0024] Preferably, in step A4, the molar ratio of ammonia to polyethylene glycol in step A1 is 3-4:1.

[0025] Preferably, in step A4, the concentration of the sodium hydroxide aqueous solution is 10 wt%, and the amount of the sodium hydroxide aqueous solution used is equal to the volume of the organic phase.

[0026] Preferably, in step A4, the stirring time is 5-6 hours after adding the sodium hydroxide aqueous solution.

[0027] Preferably, in step A5, the molar ratio of tannic acid to polyethylene glycol in step A1 is 3-5:1.

[0028] Preferably, in step A5, the pH is adjusted using a glycine-sodium hydroxide buffer solution, wherein the concentration of the glycine-sodium hydroxide buffer solution is 0.05 mol / L and the pH is 8.5-9.5.

[0029] Secondly, the present invention also provides a method for preparing the above-mentioned anti-salt thickener, comprising the following steps:

[0030] Modified polyethylene glycol was added to water and stirred to dissolve. Acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and styrene were then added and stirred until well mixed. The pH was adjusted to 6-9, and an inert atmosphere was introduced. The reaction was first kept at an inert atmosphere for 30-60 minutes, then the temperature was raised to 35-55℃ and kept at that temperature for 20-40 minutes. An initiator was added, and an inert atmosphere was introduced for another 10-12 minutes. The reaction was then kept at a sealed temperature for 12-15 hours to obtain a crude reaction product. The crude reaction product was then purified, dried, and pulverized to obtain an anti-salt thickener.

[0031] Preferably, the pH is adjusted using a 25 wt% sodium hydroxide solution.

[0032] Preferably, the inert atmosphere is nitrogen.

[0033] Preferably, the initiator is any one of hydrogen peroxide, ammonium persulfate, potassium persulfate, and cerium ammonium nitrate, and the amount of the initiator added is 1-1.2 parts by weight.

[0034] Preferably, the process of purifying the crude reaction product is as follows: the crude reaction product is added to anhydrous diethyl ether, stirred for 1-2 hours, soaked for 10-12 hours, filtered, evaporated under reduced pressure, and the resulting solid is soaked and washed in anhydrous ethanol 2-3 times, and then filtered.

[0035] Thirdly, the present invention also provides the application of the above-mentioned anti-salt thickener in the reuse of fracturing flowback fluid.

[0036] The principle of this invention is as follows:

[0037] 1. The salt-resistant thickener of the present invention uses acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrene, and modified polyethylene glycol as raw materials. Among them, the sulfonic acid group introduced by 2-acrylamido-2-methylpropanesulfonic acid has strong electrostatic repulsion, which can improve the salt resistance of the thickener; the steric hindrance of the benzene ring of styrene can better maintain the molecular chain without deformation, thus improving the salt resistance of the thickener; the modified polyethylene glycol is interspersed between the molecular chains of polyacrylamide, which is beneficial to maintaining the spatial structure of polyacrylamide.

[0038] 2. The modified polyethylene glycol of this invention first undergoes ammoniation treatment to increase the accessibility of potential binding sites, and then is modified using tannic acid. On the one hand, introducing polyhydroxy tannic acid into the thickener not only increases the water solubility of the polymer, but also provides good complexing ability for salt ions, especially iron ions. The introduction of tannic acid can complex and fix salt ions, thereby stabilizing them, reducing their impact on polymer molecules, and improving the thickener's salt resistance. On the other hand, the presence of tannic acid facilitates the softening of polyethylene glycol, allowing it to better integrate into the polyacrylamide molecular chain, and also improves its thickening ability to a certain extent.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1. The salt-resistant thickener of the present invention introduces polyhydroxy groups, which can increase its water solubility to a certain extent. At the same time, the introduced tannic acid can complex and fix salt particles, especially iron ions, thereby reducing their impact on the thickener and increasing the salt resistance of the thickener. Furthermore, the addition of polyethylene glycol can make the molecular chain spatial structure of polyacrylamide more stable, thereby improving the salt resistance of the thickener.

[0041] 2. The salt-resistant thickener of the present invention can not only withstand fracturing flowback fluid with a total mineralization of ≤1wppm and a calcium and magnesium ion concentration of ≤500ppm, but also withstand fracturing flowback fluid with an iron ion concentration of less than 50ppm, thus providing a basis for the direct use of fracturing flowback fluid. Detailed Implementation

[0042] The method of the present invention will be described below through embodiments. The embodiments are merely specific descriptions of the claims of the present invention, and the claims include, but are not limited to, the contents of the embodiments.

[0043] Unless otherwise specified, the reagents and materials described in the following examples are commercially available; and the test methods described are conventional methods unless otherwise specified.

[0044] Example 1

[0045] Step 1: Preparation of modified polyethylene glycol

[0046] A1: Take dried polyethylene glycol (PEG-4000) and stir to dissolve it in dichloromethane with a mass equal to that of polyethylene glycol. Add triethylamine and stir to dissolve to obtain mixed solution one. The molar ratio of polyethylene glycol to triethylamine is 1:10.

[0047] A2: Dissolve p-toluenesulfonyl chloride in 2.5 times the mass of p-toluenesulfonyl chloride in dichloromethane, stir and mix well to obtain mixed solution two, the molar ratio of p-toluenesulfonyl chloride and polyethylene glycol is 10:1.

[0048] A3: Under ice-water bath conditions, add mixed solution 2 dropwise to mixed solution 1 at a rate of 2-3 d / s. After the addition is complete, keep the mixture at 22℃ for 24 h. After the reaction is complete, wash the mixture 2-3 times with 3 mol / L hydrochloric acid, concentrate the reaction solution by vacuum distillation, precipitate the solution with 5 times the volume of cold diethyl ether at 0-3℃, filter the precipitate, and dry the solid to obtain intermediate product 1.

[0049] A4: Add intermediate product one to an autoclave, add ammonia water, the molar ratio of ammonia water to polyethylene glycol is 3:1, keep the reaction at 140℃ for 6 hours, cool to room temperature, extract the reaction solution multiple times with dichloromethane, combine the organic phases, add an equal volume of 10wt% sodium hydroxide aqueous solution to the organic phase, stir for 6 hours, filter, wash the solid with distilled water until neutral to obtain intermediate product two.

[0050] A5: Dissolve the prepared intermediate product II in 100 times its mass of distilled water, adjust the pH to 7-8 with 0.05 mol / L glycine-sodium hydroxide buffer solution with pH 8.5-9.5, add tannic acid, and add tannic acid to polyethylene glycol in a molar ratio of 4:1. Stir and react at 50°C for 24 h. After the reaction is complete, evaporate the reaction solution to dryness to obtain modified polyethylene glycol.

[0051] Step 2: Preparation of anti-salt thickener

[0052] Take 5 parts of modified polyethylene glycol and add it to water. After stirring and dissolving, add 55 parts of acrylamide, 50 parts of acrylic acid, 1.5 parts of 2-acrylamide-2-methylpropanesulfonic acid and 0.6 parts of styrene. After stirring and mixing, add 25 wt% sodium hydroxide solution to adjust the pH to 6-9. Purge with nitrogen and keep the reaction at a nitrogen atmosphere for 45 min. Raise the temperature to 55℃ and keep it at that temperature for 20 min. Add 1 part of initiator ammonium persulfate. Purge with nitrogen again for 10 min. Keep the reaction at a sealed temperature for 14 h to obtain the crude product. Add it to anhydrous diethyl ether, stir for 1-2 h and soak for 10 h. Filter and evaporate under reduced pressure to obtain the solid. Soak and wash it in anhydrous ethanol 2-3 times, filter and dry to obtain the refined anti-salt thickener.

[0053] Example 2

[0054] Step 1: Preparation of modified polyethylene glycol

[0055] A1: Take dried polyethylene glycol (PEG-3000) and stir to dissolve it in 2.5 times the mass of polyethylene glycol in dichloromethane. Add triethylamine and stir to dissolve to obtain mixed solution one. The molar ratio of polyethylene glycol to triethylamine is 1:11.

[0056] A2: Dissolve p-toluenesulfonyl chloride in dichloromethane at a mass equal to 3 times that of p-toluenesulfonyl chloride, stir and mix well to obtain mixed solution two, with a molar ratio of p-toluenesulfonyl chloride to polyethylene glycol of 8:1.

[0057] A3: Under ice-water bath conditions, add mixed solution 2 dropwise to mixed solution 1 at a rate of 2-3 d / s. After the addition is complete, keep the mixture at 25℃ for 24 h. After the reaction is complete, wash the mixture 2-3 times with 3 mol / L hydrochloric acid, concentrate the reaction solution by vacuum distillation, precipitate the solution with 5 times the volume of cold diethyl ether at 0-3℃, filter the precipitate, and dry the solid to obtain intermediate product 1.

[0058] A4: Add intermediate product one to an autoclave, add ammonia water, the molar ratio of ammonia water to polyethylene glycol is 4:1, keep the reaction at 120℃ for 8 hours, cool to room temperature, extract the reaction solution multiple times with dichloromethane, combine the organic phases, add an equal volume of 10wt% sodium hydroxide aqueous solution to the organic phase, stir for 6 hours, filter, wash the solid with distilled water until neutral to obtain intermediate product two.

[0059] A5: Dissolve the prepared intermediate product II in 100 times its mass of distilled water, adjust the pH to 7-8 with 0.05 mol / L glycine-sodium hydroxide buffer solution with pH 8.5-9.5, add tannic acid, and add tannic acid to polyethylene glycol in a molar ratio of 3:1. Stir and react at 55℃ for 16 h. After the reaction is complete, evaporate the reaction solution to dryness to obtain modified polyethylene glycol.

[0060] Step 2: Preparation of anti-salt thickener

[0061] Take 3 parts of modified polyethylene glycol and add it to water. After stirring and dissolving, add 60 parts of acrylamide, 55 parts of acrylic acid, 2 parts of 2-acrylamide-2-methylpropanesulfonic acid and 1 part of styrene. After stirring and mixing, add 25 wt% sodium hydroxide solution to adjust the pH to 6-9. Purge with nitrogen and keep the reaction at a nitrogen atmosphere for 30 min. Raise the temperature to 35℃ and keep it at that temperature for 40 min. Add 1.2 parts of cerium ammonium nitrate initiator. Purge with nitrogen again for 10 min. Keep the reaction at a sealed temperature for 12 h to obtain the crude product. Add it to anhydrous diethyl ether, stir for 1-2 h and soak for 12 h. Filter and evaporate under reduced pressure to obtain the solid. Soak and wash it in anhydrous ethanol 2-3 times, filter and dry to obtain the refined anti-salt thickener.

[0062] Example 3

[0063] Step 1: Preparation of modified polyethylene glycol

[0064] A1: Take dried polyethylene glycol (PEG-4000) and stir to dissolve it in dichloromethane with a mass equal to that of polyethylene glycol. Add triethylamine and stir to dissolve to obtain mixed solution one. The molar ratio of polyethylene glycol to triethylamine is 1:12.

[0065] A2: Dissolve p-toluenesulfonyl chloride in 2.8 times the mass of p-toluenesulfonyl chloride in dichloromethane, stir and mix well to obtain mixed solution two, the molar ratio of p-toluenesulfonyl chloride and polyethylene glycol is 9:1.

[0066] A3: Under ice-water bath conditions, add mixed solution 2 dropwise to mixed solution 1 at a rate of 2-3 d / s. After the addition is complete, keep the mixture at 20℃ for 24 h. After the reaction is complete, wash the mixture 2-3 times with 3 mol / L hydrochloric acid, concentrate the reaction solution by vacuum distillation, precipitate the solution with 5 times the volume of cold diethyl ether at 0-3℃, filter the precipitate, and dry the solid to obtain intermediate product 1.

[0067] A4: Add intermediate product one to an autoclave, add ammonia water, the molar ratio of ammonia water to polyethylene glycol is 3:1, keep the reaction at 130℃ for 5h, cool to room temperature, extract the reaction solution multiple times with dichloromethane, combine the organic phases, add an equal volume of 10wt% sodium hydroxide aqueous solution to the organic phase, stir for 6h, filter, wash the solid with distilled water until neutral to obtain intermediate product two.

[0068] A5: Dissolve the prepared intermediate product II in 100 times its mass of distilled water, adjust the pH to 7-8 with 0.05 mol / L glycine-sodium hydroxide buffer solution with pH 8.5-9.5, add tannic acid, and add tannic acid to polyethylene glycol in a molar ratio of 5:1. Stir and react at 60℃ for 12 h. After the reaction is complete, evaporate the reaction solution to dryness to obtain modified polyethylene glycol.

[0069] Step 2: Preparation of anti-salt thickener

[0070] Take 4 parts of modified polyethylene glycol and add it to water. After stirring and dissolving, add 53 parts of acrylamide, 45 parts of acrylic acid, 1.8 parts of 2-acrylamido-2-methylpropanesulfonic acid and 0.1 parts of styrene. After stirring and mixing, add 25 wt% sodium hydroxide solution to adjust the pH to 6-9. Purge with nitrogen and keep the reaction at a nitrogen atmosphere for 60 min. Raise the temperature to 40℃ and keep it at that temperature for 30 min. Add 1.1 parts of potassium persulfate initiator. Purge with nitrogen again for 10 min. Keep the reaction at a sealed temperature for 15 h to obtain the crude product. Add it to anhydrous diethyl ether, stir for 1-2 h and soak for 11 h. Filter and evaporate under reduced pressure to obtain the solid. Soak and wash it in anhydrous ethanol 2-3 times, filter and dry to obtain the refined anti-salt thickener.

[0071] The salt-resistant thickener prepared in Example 1 was mixed with brine containing 1000 ppm total mineralization, 500 ppm calcium and magnesium ions, and 50 ppm iron ions to obtain an aqueous solution with a salt-resistant thickener concentration of 1.5 wt%, which is fracturing fluid one.

[0072] Meanwhile, the salt-resistant thickener prepared in Examples 2 and 3 was used to replace the salt-resistant thickener in Example 1 to prepare fracturing fluid 2 and fracturing fluid 3, respectively. The salt-resistant thickener of the present invention was replaced with a commercially available thickener to prepare fracturing fluid 4 and fracturing fluid 5, respectively. The apparent viscosity of fracturing fluid 1 to fracturing fluid 5 was tested, and the temperature and shear viscosity were tested after shearing at 170 s⁻¹ and 110 °C for 60 min. The results are shown in Table 1.

[0073] Table 1 Apparent viscosity and temperature- and shear-resistant viscosity of fracturing fluids 1-5

[0074]

[0075] As can be seen from the data in the table above, the thickener of the present invention, after undergoing temperature and shear resistance tests under saline conditions of 10,000 ppm total mineralization, 500 ppm calcium and magnesium ions, and 50 ppm iron ions, still exhibits an apparent viscosity of ≥50 mPa·s, demonstrating excellent salt resistance. Therefore, the backflow solution can be used directly without prior desalination, saving both time and application costs.

[0076] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A salt-resistant thickener, characterized in that, By weight, the raw materials include 53-60 parts acrylamide, 45-55 parts acrylic acid, 1.5-2 parts 2-acrylamido-2-methylpropanesulfonic acid, 0.1-1 parts styrene, and 3-6 parts modified polyethylene glycol.

2. The anti-salt thickener according to claim 1, characterized in that, The anti-salt thickener, by weight, comprises 55 parts acrylamide, 50 parts acrylic acid, 1.5 parts 2-acrylamide-2-methylpropanesulfonic acid, 0.6 parts styrene, and 5 parts modified polyethylene glycol.

3. The anti-salt thickener according to claim 1, characterized in that, The modified polyethylene glycol is tannic acid-modified polyethylene glycol.

4. The anti-salt thickener according to claim 3, characterized in that, The preparation method of the tannic acid-modified polyethylene glycol includes the following steps: A1: Take dried polyethylene glycol and dissolve it in dichloromethane by stirring. Add triethylamine and stir to dissolve to obtain mixed solution one. A2: Dissolve p-toluenesulfonyl chloride in dichloromethane, stir and mix well to obtain mixed solution two; A3: Under ice-water bath conditions, add mixture two dropwise to mixture one. After the addition is complete, keep the mixture at 20-25℃ for 22-24 hours. After the reaction is complete, wash with hydrochloric acid 2-3 times, concentrate the reaction solution, precipitate with cold diethyl ether at 0-3℃, filter to obtain a solid, dry, and obtain intermediate product one. A4: Add intermediate product one and ammonia water to the reaction vessel and keep it at 120-140℃ for 5-8 hours. Cool to room temperature, extract the reaction solution with dichloromethane multiple times, combine the organic phases, add sodium hydroxide aqueous solution to the organic phase, stir, filter, and wash the solid with distilled water until neutral to obtain intermediate product two. A5: Dissolve the prepared intermediate product II in distilled water, adjust the pH to 7-8, add tannic acid, and stir the reaction at 50-60℃ for 12-24h. After the reaction is complete, evaporate the reaction solution to obtain tannic acid modified polyethylene glycol.

5. The anti-salt thickener according to claim 4, characterized in that, The molar ratio of polyethylene glycol, triethylamine, p-toluenesulfonyl chloride, ammonia, and tannic acid is 1:10-12:8-10:3-4:3-5.

6. The anti-salt thickener according to claim 4, characterized in that, In step A3, the concentration of the hydrochloric acid is 3 mol / L; And / or, in step A4, the concentration of the sodium hydroxide aqueous solution is 10 wt%, the amount of the sodium hydroxide aqueous solution is equal to the volume of the organic material, and the stirring time is 5-6 hours after adding the sodium hydroxide aqueous solution; And / or, in step A5, the pH is adjusted using a glycine-sodium hydroxide buffer solution, wherein the concentration of the glycine-sodium hydroxide buffer solution is 0.05 mol / L and the pH is 8.5-9.

5.

7. The method for preparing the anti-salt thickener according to any one of claims 1-6, characterized in that, The steps are as follows: Modified polyethylene glycol was added to water and stirred to dissolve. Acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and styrene were then added and stirred until well mixed. The pH was adjusted to 6-9, and an inert atmosphere was introduced. The reaction was first kept at an inert atmosphere for 30-60 minutes, then the temperature was raised to 35-55℃ and kept at that temperature for 20-40 minutes. An initiator was added, and an inert atmosphere was introduced for another 10 minutes. The reaction was then kept at a sealed temperature for 12-15 hours to obtain a crude reaction product. The crude reaction product was then purified, dried, and pulverized to obtain an anti-salt thickener.

8. The method for preparing the anti-salt thickener according to claim 7, characterized in that, The initiator is any one of hydrogen peroxide, ammonium persulfate, potassium persulfate, and cerium ammonium nitrate, and the amount of the initiator added is 1-1.2 parts by weight. And / or, the inert atmosphere is nitrogen.

9. The method for preparing the anti-salt thickener according to claim 7, characterized in that, The process of purifying the crude reaction product is as follows: the crude reaction product is added to anhydrous diethyl ether, stirred for 1-2 hours, soaked for 10-12 hours, filtered, evaporated under reduced pressure, and the resulting solid is soaked and washed in anhydrous ethanol 2-3 times, and then filtered.

10. The application of the anti-salt thickener according to any one of claims 1-6 in the reuse of fracturing flowback fluid.

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