A fracturing fluid thickener for oil production and preparation method thereof

Abstract

The present invention belongs to the technical field of oilfield fracturing fluids, and specifically relates to a fracturing fluid thickener for oil production and a preparation method thereof. In the present invention, acrylamide and acrylic acid are selected as the molecular backbone of the fracturing fluid thickener for oil production, effectively improving the solubility of the thickener molecules. Long-chain alkyl esters, phosphoric acid groups, benzenesulfonic acid groups, and caprolactam groups are introduced into the fracturing fluid thickener molecules by using octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate, and N-vinylcaprolactam. This allows the resulting fracturing fluid thickener molecules to form a non-linear comb-like structure. Through the dual effects of physical crosslinking between molecular side chains and chemical crosslinking by the crosslinking agent, the high-temperature shear resistance of the fracturing fluid thickener is significantly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield fracturing fluids, and in particular relates to a fracturing fluid thickener for oil production and a preparation method thereof. Background Art

[0002] Fracturing fluid is a heterogeneous, unstable chemical system composed of multiple additives in a specific ratio. It is used during the fracturing of oil and gas reservoirs. Its primary function is to transmit the high pressure generated by surface equipment into the formation, causing it to fracture and form cracks, along which proppant is transported. Thickeners are polymer additives used to increase the viscosity and improve the rheological properties of aqueous systems and are one of the main components of fracturing fluid.

[0003] Currently, common thickeners on the domestic and international markets include natural polymers, biopolymers, and synthetic polymers. Compared to natural polymers, synthetic polymers offer improved temperature and shear resistance, stronger thickening capacity, better sand suspension and gel breaking properties, and are insensitive to bacteria, outperforming natural polymers in all respects. Synthetic polymer thickeners available domestically and internationally primarily include acrylamide polymers, ethylene polymers, and cross-linked polymers. Acrylamide polymer thickeners have become the mainstream thickener due to their excellent performance, but they still suffer from issues such as slow dissolution, poor salt and temperature resistance, and weak sand-carrying capacity. Chinese patent application document with application publication number CN110964496A discloses a fracturing fluid thickening and viscosifying agent, comprising white oil, acrylamide monomer, ethanol, sorbitan fatty acid ester, cetyltrimethylammonium bromide, a suspension stabilizer, and water. The suspension stabilizer is composed of gum arabic and acrylic acid-sodium styrene sulfonate-hydroxyethyl methacrylate. This thickening agent has good sand suspension and viscosity-increasing effects, and is resistant to high temperatures and salt. The polymerizable monomer used is acrylamide. When the temperature rises, the amide group decomposes. Although the suspension stabilizer is present in the system, the solution system does not experience stratification. However, the thickener has poor temperature resistance, resulting in a poor thickening effect at high temperatures.

[0004] In addition, the polymer thickeners currently in use still have the following problems: (1) Poor storage stability: obvious oil-liquid separation often occurs after about two months of storage, and there is also a phenomenon of wall adhesion in the casing and oil pipe during use; (2) Poor temperature resistance: At high temperatures, the viscosity of the product decreases and the thickening performance of the product deteriorates. Chinese patent application publication number CN119161526A discloses a method for synthesizing a polymer thickener. Specifically, the method comprises the following steps: 4-trifluoromethylcinnamic acid, deionized water, hydroxyethyl cellulose, TX-10, and potassium dihydrogen phosphate are sequentially added to a reactor, stirred evenly, and the pH adjusted to 7-8; 4,4'-diaminostilbene-2,2'-disulfonic acid, 2-allyloxymethyl-2-hydroxymethylpropane-1,3-diol, and deionized water are added to a second reactor, stirred evenly, and the pH adjusted to 7-8; an initiator is added via a high-level addition tank and added dropwise to the first reactor with continuous stirring. When the viscosity begins to rise, the mixed liquid from the second reactor is added, stirred continuously, and then the temperature is raised and the mixture is kept warm for reaction to obtain a viscous liquid; the mixture is then dried and granulated to obtain the thickener product. The thickener produced by this method decomposes its molecular chains at high temperatures, resulting in poor viscosity and poor thickening properties. Furthermore, the thickener exhibits stratification during storage, resulting in poor storage stability. Summary of the Invention

[0005] In order to solve the technical problems of poor temperature resistance and poor storage stability in the prior art, the purpose of the present invention is to provide a fracturing fluid thickener for oil production and a preparation method thereof.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for preparing a fracturing fluid thickener for oil production comprises the following steps:

[0008] S1: uniformly mixing acrylamide, acrylic acid, emulsifier and deionized water to obtain an aqueous phase;

[0009] S2: Glycerol, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam are mixed to obtain an oil phase;

[0010] S3: Add the aqueous phase obtained in step S1 to the oil phase obtained in step S2 under stirring, stir evenly, add an initiator under a nitrogen atmosphere, heat, react for 4-5 hours, add a chain transfer agent and a cross-linking agent, stir to react, and cool to obtain a fracturing fluid thickener for oil production.

[0011] In the present invention, acrylamide and acrylic acid are selected as the molecular backbone of the fracturing fluid thickener for oil production, effectively improving the solubility of the thickener molecules. Long-chain alkyl esters, phosphoric acid groups, benzenesulfonic acid groups and caprolactam groups are introduced into the fracturing fluid thickener molecules through octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam, so that the prepared fracturing fluid thickener molecules form a non-linear comb-like structure. Through the dual effects of physical crosslinking between molecular side chains and chemical crosslinking of the crosslinking agent, the high-temperature shear resistance of the fracturing fluid thickener for oil production is greatly improved.

[0012] The sulfonic acid groups in the sodium 4-vinylbenzenesulfonate used in the present invention are directly connected to the carbon atoms on the benzene ring, which effectively improves the stability of the sulfonic acid groups in the side chains of the thickener molecules, thereby improving the storage stability of the thickener. Octadecanyl methacrylate can introduce long hydrophobic side chains into the side chains of the thickener molecules, so that the thickener molecules in the solution form an associative network, effectively improving the thickening ability of the thickener. Vinyl phosphoric acid can introduce phosphoric acid groups into the side chains of the thickener molecules. The phosphoric acid groups have good water solubility and can ensure that the thickener can be fully dissolved in water to form a stable solution system, effectively improving the solubility and storage stability of the thickener. N-vinyl caprolactam and sodium 4-vinylbenzenesulfonate can introduce cyclic rigid structures such as benzene rings into the molecular side chains of the thickener, effectively improving the temperature resistance of the thickener, making it suitable for acidizing and fracturing on-site construction in high-temperature deep wells.

[0013] Furthermore, the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam is 19-21:11-13:3-5:4-7:3-5.

[0014] The present invention controls the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphonic acid, sodium 4-vinylbenzenesulfonate, and N-vinylcaprolactam to control the number and structure of molecular side chains in the resulting fracturing fluid thickener, thereby influencing the solubility, temperature resistance, and storage stability of the resulting fracturing fluid thickener. The fracturing fluid thickener produced within the ratio range provided by the present invention can form a comb-like structure with alternating side chains of varying lengths, effectively improving the performance of the fracturing fluid thickener.

[0015] Furthermore, the chain transfer agent in step S3 is one of trichloroethylene, tetrachloromethane and 2,6-di-tert-butyl-p-cresol, and the mass fraction of the chain transfer agent is 3-5 parts.

[0016] In the present invention, the molecular weight of the oil fracturing fluid thickener molecule and the branching of the polymer molecular chain are adjusted by adding a chain transfer agent, so that the molecular weight distribution of the prepared oil fracturing fluid thickener is more uniform.

[0017] Furthermore, the cross-linking agent in step S3 is composed of N-hydroxymethyl acrylamide and p-toluenesulfonic acid in a mass ratio of 3-5:7-9, and the mass fraction of the cross-linking agent is 6-9 parts.

[0018] Crosslinkers can enhance the bonding between thickener molecules, forming a network structure. This increases solution viscosity while also improving storage stability. The addition of N-hydroxymethyl acrylamide stabilizes internal crosslinking between thickener molecules, while the addition of p-toluenesulfonic acid stabilizes crosslinking between thickener molecules, increasing both viscosity and storage stability.

[0019] Furthermore, the mass proportions of acrylamide, acrylic acid, emulsifier and deionized water in step S1 are respectively: 23-27 parts of acrylamide, 30-35 parts of acrylic acid, 5-8 parts of emulsifier and 50-60 parts of deionized water.

[0020] Furthermore, the emulsifier in step S1 is one of sodium carboxymethyl cellulose, sodium glycerate, fatty acid glyceride and sorbitol fatty acid ester.

[0021] Furthermore, the mass fraction of the glycerol in step S2 is 32-37 parts.

[0022] Furthermore, in step S3, the stirring speed of the stirring state is 1000-1500 rpm, the stirring reaction time is 30-40 min, and the heating temperature is 45-50°C.

[0023] Furthermore, the initiators in step S3 are sodium bisulfite and ammonium persulfate, the mass fraction of sodium bisulfite is 2-3 parts, and the mass fraction of ammonium persulfate is 2-3 parts.

[0024] The present invention also provides a fracturing fluid thickener for oil production prepared by utilizing the preparation method of the fracturing fluid thickener for oil production.

[0025] Compared with the prior art, the fracturing fluid thickener for oil production and the preparation method thereof provided by the present invention have the following technical advantages:

[0026] (1) In the present invention, acrylamide and acrylic acid are used as the molecular backbone of the fracturing fluid thickener for oil production, and a phosphoric acid group is introduced into the molecule of the fracturing fluid thickener for oil production, thereby effectively improving the solubility of the thickener;

[0027] (2) The present invention introduces a long hydrophobic side chain and a rigid ring structure into the molecular structure of the fracturing fluid thickener for oil production, thereby effectively improving the temperature resistance of the thickener;

[0028] (3) The present invention uses sodium 4-vinylbenzenesulfonate and vinyl phosphoric acid as functional monomers and adds a cross-linking agent during the polymerization process, which effectively improves the storage stability of the thickener. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope image of the thickener prepared in Example 3. DETAILED DESCRIPTION

[0030] The following will be further described in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. Those skilled in the art can make various modifications based on the basic concept of the present invention, but as long as they do not deviate from the basic concept of the present invention, they are all within the scope of the present invention.

[0031] Example 1

[0032] A method for preparing a fracturing fluid thickener for oil production comprises the following steps:

[0033] S1: 23 g acrylamide, 35 g acrylic acid, 5 g sodium carboxymethyl cellulose and 50 g deionized water were mixed to obtain an aqueous phase;

[0034] S2: 32 g of glycerol was mixed with octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate, and N-vinylcaprolactam to obtain an oil phase;

[0035] S3: adding the aqueous phase obtained in step S1 to the oil phase obtained in step S2 under stirring at a speed of 1000 rpm, stirring evenly, adding 2 g of sodium bisulfite and 2 g of ammonium persulfate under a nitrogen atmosphere, heating to 45° C., reacting for 4 h, adding 3 g of trichloroethylene and 6 g of a cross-linking agent, stirring and reacting for 30 min, and cooling to obtain a fracturing fluid thickener for oil production;

[0036] The molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam is 19:11:3:4:3; the crosslinking agent is composed of N-hydroxymethyl acrylamide and p-toluenesulfonic acid in a mass ratio of 3:7.

[0037] Example 2

[0038] A method for preparing a fracturing fluid thickener for oil production comprises the following steps:

[0039] S1: 27 g acrylamide, 30 g acrylic acid, 8 g fatty acid glyceride and 60 g deionized water were mixed to obtain an aqueous phase;

[0040] S2: 37 g of glycerol, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate, and N-vinylcaprolactam were mixed to obtain an oil phase;

[0041] S3: adding the aqueous phase obtained in step S1 to the oil phase obtained in step S2 under stirring at a speed of 1500 rpm, stirring evenly, adding 3 g of sodium bisulfite and 3 g of ammonium persulfate under a nitrogen atmosphere, heating to 50° C., reacting for 5 h, adding 5 g of tetrachloromethane and 9 g of a cross-linking agent, stirring and reacting for 40 min, and cooling to obtain a fracturing fluid thickener for oil production;

[0042] The molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam is 21:13:5:7:5; the crosslinking agent is composed of N-hydroxymethyl acrylamide and p-toluenesulfonic acid in a mass ratio of 5:9.

[0043] Example 3

[0044] A method for preparing a fracturing fluid thickener for oil production comprises the following steps:

[0045] S1: 25 g acrylamide, 33 g acrylic acid, 5 g sorbitan fatty acid ester and 58 g deionized water were mixed to obtain an aqueous phase;

[0046] S2: 36 g of glycerol, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate, and N-vinylcaprolactam were mixed to obtain an oil phase;

[0047] S3: The aqueous phase obtained in step S1 was added to the oil phase obtained in step S2 under stirring at a speed of 1350 rpm, and the mixture was stirred evenly. Under a nitrogen atmosphere, 2.5 g of sodium bisulfite and 2.3 g of ammonium persulfate were added, and the mixture was heated to 48° C. and reacted for 4.3 h. 4 g of 2,6-di-tert-butyl-p-cresol and 8 g of a cross-linking agent were added, and the mixture was stirred and reacted for 35 min. The mixture was cooled to obtain a fracturing fluid thickener for oil production.

[0048] The molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam is 20:12:4:5:4; the crosslinking agent is composed of N-hydroxymethyl acrylamide and p-toluenesulfonic acid in a mass ratio of 4:9.

[0049] Comparative Example 1

[0050] The preparation method of the fracturing fluid thickener for oil production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that an equal amount of acrylic acid is used instead of octadecyl methacrylate in this comparative example.

[0051] Comparative Example 2

[0052] The preparation method of the fracturing fluid thickener for oil production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that an equal amount of methyl acrylate is used instead of vinyl phosphoric acid in this comparative example.

[0053] Comparative Example 3

[0054] The preparation method of the fracturing fluid thickener for oil production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that an equal amount of methyl acrylate is used instead of N-vinyl caprolactam in this comparative example.

[0055] Comparative Example 4

[0056] The preparation method of the fracturing fluid thickener for oil production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that an equal amount of methyl acrylate is used instead of sodium 4-vinylbenzenesulfonate in this comparative example.

[0057] Comparative Example 5

[0058] The preparation method of the fracturing fluid thickener for oil production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam in this comparative example is 20:4:9:11:13.

[0059] Comparative Example 6

[0060] The preparation method of the fracturing fluid thickener for oil production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the cross-linking agents in this comparative example are all N-hydroxymethyl acrylamide.

[0061] Comparative Example 7

[0062] The preparation method of the fracturing fluid thickener for oil production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the crosslinking agent in this comparative example is composed of N-hydroxymethyl acrylamide and p-toluenesulfonic acid in a mass ratio of 13:2.

[0063] Test example

[0064] Temperature resistance test: The thickeners prepared in Examples 1 to 3, Comparative Example 1, Comparative Example 3, Comparative Example 4 and Comparative Example 5 were dissolved in a 15% hydrochloric acid solution to prepare an acid solution with a mass fraction of 0.8%. The acid solution was tested at 30°C, 100°C, 150°C, 200°C and 250°C at a shear rate of 170s. -1 The endpoint apparent viscosity under the conditions is shown in Table 1.

[0065] Storage stability test: The thickeners prepared in Examples 1-3, Comparative Example 2, and Comparative Examples 5-7 were stored at room temperature (25-30°C) for 6 months and 12 months, respectively, to observe whether the thickeners separated. The test results are shown in Table 2.

[0066] Salt resistance test: According to Q / JRF135-2021 "Thickener Polymers for Fracturing Fluids JRYLZG", the thickeners prepared in Examples 1 to 3 were subjected to salt resistance tests, and their viscosity retention rates in brine were recorded. The test results are shown in Table 3.

[0067] Scanning electron microscope test: The thickener prepared in Example 3 was placed in a vacuum drying oven to dry, and then gold-plated. The microscopic morphology and structural characteristics of the polymer were observed using a scanning electron microscope. Figure 1 .

[0068] Table 1 Temperature resistance test results

[0069]

[0070] As shown in Table 1, the apparent viscosity of the fracturing fluid thickener provided by the present invention is 109-121 mPa·s at 30°C, 102-117 mPa·s at 100°C, 91-103 mPa·s at 150°C, 82-95 mPa·s at 200°C, and 77-89 mPa·s at 250°C, fully demonstrating that the fracturing fluid thickener provided by the present invention has good temperature resistance. Among them, the thickener prepared in Example 3 has the best apparent viscosity and is the best embodiment of the present invention.

[0071] Compared with Example 3, Comparative Example 1 uses an equal amount of acrylic acid instead of octadecyl methacrylate, but the temperature resistance of the obtained thickener deteriorates, which indicates that octadecyl methacrylate can introduce long-chain alkyl esters into the molecular side chain of the thickener, enhance the interaction force between the thickener molecules, and improve the temperature resistance of the thickener; Comparative Example 3 uses an equal amount of methyl acrylate instead of N-vinyl caprolactam, and Comparative Example 4 uses an equal amount of methyl acrylate instead of sodium 4-vinylbenzenesulfonate, but the temperature resistance of the obtained thickener deteriorates, which indicates that N-vinyl caprolactam and 4-vinylbenzenesulfonate have a strong interaction effect on the thickener. Sodium sulfonate can introduce a rigid ring structure into the molecular side chain of the thickener, effectively improving the temperature resistance of the thickener; Comparative Example 5 changed the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinyl caprolactam, but the temperature resistance of the obtained thickener deteriorated. This shows that the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinyl caprolactam in the present invention has been optimized. Changing its molar ratio will affect the side chain structure of the thickener molecule, resulting in poor temperature resistance.

[0072] Table 2 Storage stability test results

[0073]

[0074] As shown in Table 2, the fracturing fluid thickener for oil production provided by the present invention did not show stratification phenomenon after being stored at room temperature for 6 months and 12 months, which fully demonstrates that the fracturing fluid thickener for oil production provided by the present invention has good storage stability.

[0075] Compared with Example 3, Comparative Example 2 uses an equal amount of methyl acrylate instead of vinyl phosphoric acid, but the obtained thickener shows stratification after being placed for 12 months, which shows that vinyl phosphoric acid can introduce water-soluble phosphoric acid groups into the thickener molecules, which can improve the storage stability of the thickener; Comparative Example 5 changes the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam, but the obtained thickener shows stratification after being placed for 12 months, which shows that changing the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam can improve the storage stability of the thickener. The molar ratio of sodium vinylbenzenesulfonate and N-vinylcaprolactam affects the side chain structure of the thickener molecule, thereby affecting its storage stability. In Comparative Example 6, the crosslinker is entirely N-methylolacrylamide. In Comparative Example 7, the mass ratio of N-methylolacrylamide and p-toluenesulfonic acid is changed. However, the resulting thickener exhibits stratification after six months of storage. This demonstrates that the use of N-methylolacrylamide and p-toluenesulfonic acid in a certain mass ratio as a crosslinker in the present invention can effectively improve the storage stability of the thickener, while changing the components or ratios can lead to a deterioration in the storage stability of the thickener.

[0076] Table 3 Salt tolerance test results

[0077]

[0078] As shown in Table 3, the viscosity retention rate of the fracturing fluid thickener for oil production provided by the present invention in brine is 74.9%-81.3%, which shows that the fracturing fluid thickener for oil production provided by the present invention has good salt resistance.

[0079] Depend on Figure 1 It can be seen that the molecular chains of the fracturing fluid thickener for oil production provided by the present invention are a network structure, and the molecular chains are entangled with each other, which is beneficial to improving the temperature resistance and salt resistance of the thickener molecules.

[0080] The above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Persons skilled in the art should not modify the above embodiments without departing from the spirit and scope of the present invention. Any equivalent modifications or alterations made by persons skilled in the art without departing from the technical spirit of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a fracturing fluid thickener for oil production, characterized in that: The following steps are involved: S1: uniformly mixing acrylamide, acrylic acid, emulsifier and deionized water to obtain an aqueous phase; S2: Glycerol, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam are mixed to obtain an oil phase; S3: adding the aqueous phase obtained in step S1 to the oil phase obtained in step S2 under stirring, stirring evenly, adding an initiator under a nitrogen atmosphere, heating, reacting for 4-5 hours, adding a chain transfer agent and a cross-linking agent, stirring to react, and cooling to obtain a fracturing fluid thickener for oil production; The mass proportions of acrylamide, acrylic acid, emulsifier and deionized water in step S1 are: 23-27 parts of acrylamide, 30-35 parts of acrylic acid, 5-8 parts of emulsifier and 50-60 parts of deionized water respectively; The molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinylcaprolactam is 19-21:11-13:3-5:4-7:3-5; The cross-linking agent is composed of N-hydroxymethyl acrylamide and p-toluenesulfonic acid in a mass ratio of 3-5:7-9.

2. The method for preparing a fracturing fluid thickener for oil production according to claim 1, wherein: The chain transfer agent in step S3 is one of trichloroethylene, tetrachloromethane and 2,6-di-tert-butyl-p-cresol.

3. The method for preparing a fracturing fluid thickener for oil production according to claim 1, wherein: The mass fraction of the chain transfer agent is 3-5 parts, and the mass fraction of the cross-linking agent is 6-9 parts.

4. The method for preparing a fracturing fluid thickener for oil production according to claim 1, wherein: The emulsifier in step S1 is one of sodium carboxymethyl cellulose, sodium glycerate, fatty acid glyceride and sorbitol fatty acid ester.

5. The method for preparing a fracturing fluid thickener for oil production according to claim 1, wherein: The mass fraction of the glycerol in step S2 is 32-37 parts.

6. The method for preparing a fracturing fluid thickener for oil production according to claim 1, wherein: The stirring speed in the stirring state in step S3 is 1000-1500 rpm, the stirring reaction time is 30-40 min, and the heating temperature is 45-50°C.

7. The method for preparing a fracturing fluid thickener for oil production according to claim 1, wherein: The initiator in step S3 is composed of sodium bisulfite and ammonium persulfate, with the mass fraction of sodium bisulfite being 2-3 parts and the mass fraction of ammonium persulfate being 2-3 parts.

8. A fracturing fluid thickener for oil production prepared according to the method for preparing a fracturing fluid thickener for oil production according to any one of claims 1 to 7.

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