Fracturing fluid thickening agent for oil extraction and preparation method thereof

Abstract

The invention belongs to the technical field of oil field fracturing fluid, and particularly relates to a fracturing fluid thickening agent for oil extraction and a preparation method thereof. Acrylamide and acrylic acid are selected as molecular main chains of the fracturing fluid thickening agent for oil extraction, so that the dissolving property of molecules of the thickening agent is effectively improved; long-chain alkyl ester, a phosphate group, a benzenesulfonic acid group and a caprolactam group are introduced into molecules of the fracturing fluid thickening agent for oil extraction through octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinyl benzenesulfonate and N-ethylene caprolactam, so that the molecules of the prepared fracturing fluid thickening agent for oil extraction form a non-linear chain comb-shaped structure; the high-temperature shear resistance of the fracturing fluid thickening agent for oil extraction is greatly improved through the dual effects of physical crosslinking between molecular side chains and chemical crosslinking of the crosslinking agent.

Description

Technical Field

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

[0002] Fracturing fluid refers to a heterogeneous and unstable chemical system formed by a certain ratio of multiple additives. It is a working fluid used for fracturing oil and gas layers. Its main function is to transfer the high pressure formed by ground equipment to the formation, so that the formation breaks and cracks are formed, and proppant is transported along the cracks. Thickener is a polymer additive used to increase the viscosity of the water-based system and improve the rheology. It is one of the main components of fracturing fluid.

[0003] At present, the common thickeners in the domestic and foreign markets mainly include natural polymers, biopolymers and synthetic polymers. Compared with natural polymers, synthetic polymers have better temperature and shear resistance, strong thickening ability, good sand suspension ability and gel breaking ability, and are insensitive to bacteria. Their performance is superior to that of natural polymers in all aspects. The synthetic polymer thickeners at home and abroad mainly include acrylamide polymers, ethylene polymers and cross-linked polymers. Among them, acrylamide polymer thickeners have become the mainstream product among thickeners due to their good performance, but they still have problems such as slow dissolution, poor salt and temperature resistance, and weak sand carrying capacity. A Chinese patent application document with application publication number CN110964496A discloses a fracturing fluid thickening and tackifying agent, comprising white oil, acrylamide monomer, ethanol, sorbitan fatty acid ester, hexadecyltrimethylammonium bromide, a suspension stabilizer and water. The suspension stabilizer is composed of gum arabic and acrylic acid-sodium styrene sulfonate-hydroxyethyl methacrylate. The thickening agent has good sand suspension effect, good viscosity increasing effect, high temperature resistance and good salt resistance. The polymerized monomer used is acrylamide. When the temperature rises, the amide group decomposes. Although there is a suspension stabilizer in the system, the solution system will not show stratification, but the temperature resistance of the thickener is poor, resulting in poor thickening effect of the product at high temperature.

[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 wall adhesion phenomenon 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. The Chinese patent application document with application publication number CN119161526A discloses a method for synthesizing a polymer thickener, specifically: 4-trifluoromethylcinnamic acid, deionized water, hydroxyethyl cellulose, TX-10, potassium dihydrogen phosphate are added to the reactor in sequence, stirred evenly, and the pH is adjusted to 7-8; 4,4'-diaminobenzene-2,2'-disulfonic acid, 2-allyloxymethyl-2-hydroxymethylpropane-1,3-diol, and deionized water are added to the second reactor, stirred evenly, and the pH is adjusted to 7-8; the initiator is added to the high-position drop tank, dripped into the first reactor, and stirred continuously. When the viscosity begins to rise, the mixed liquid in the second reactor is added, and stirring is continued, and then the temperature is raised, and the reaction is kept warm to obtain a viscous liquid; drying and granulation are performed to obtain the product thickener. The thickener prepared by this method will decompose the molecular chain at high temperature, the viscosity of the product will deteriorate, resulting in poor thickening performance of the product, and stratification will occur during storage, and the storage stability is poor. 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 object 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: A method for preparing a fracturing fluid thickener for oil production comprises the following steps: S1: uniformly mixing acrylamide, acrylic acid, emulsifier and deionized water to obtain an aqueous phase; S2: mixing glycerol, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzene sulfonate and N-vinyl caprolactam to obtain an oil phase; S3: Add the water 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, cool, and obtain a fracturing fluid thickener for oil production.

[0007] In the present invention, acrylamide and acrylic acid are selected as the main molecular chains of the thickener for oil production fracturing fluid, so as to effectively improve the solubility of the thickener molecules. Long-chain alkyl esters, phosphoric acid groups, benzenesulfonic acid groups and caprolactam groups are introduced into the thickener molecules for oil production fracturing fluid through octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinyl caprolactam, so that the prepared thickener molecules for oil production fracturing fluid form a non-linear comb-like structure. Through the dual effects of physical crosslinking between molecular side chains and chemical crosslinking of a crosslinking agent, the high-temperature shear resistance of the thickener for oil production fracturing fluid is greatly improved.

[0008] The sulfonic acid group in the sodium 4-vinylbenzenesulfonate used in the present invention is directly connected to the carbon atom on the benzene ring, which effectively improves the stability of the sulfonic acid group in the side chain of the thickener molecule, thereby improving the storage stability of the thickener; octadecyl methacrylate can introduce a long hydrophobic side chain into the side chain of the thickener molecule, so that the thickener molecules in the solution form an association network, effectively improving the viscosity-increasing ability of the thickener; vinyl phosphoric acid can introduce a phosphoric acid group into the side chain of the thickener molecule, and the phosphoric acid group has good water solubility, which can ensure that the thickener can be fully dissolved in water and form a stable solution system, effectively improving the solubility and storage stability of the thickener; N-vinyl caprolactam and sodium 4-vinylbenzenesulfonate can introduce a cyclic rigid structure such as a benzene ring into the molecular side chain of the thickener, effectively improving the temperature resistance of the thickener, so that the thickener is suitable for acidification and fracturing on-site construction of high-temperature deep wells.

[0009] Furthermore, the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinyl caprolactam is 19-21:11-13:3-5:4-7:3-5.

[0010] In the present invention, the number and structure of molecular side chains of the prepared oil fracturing fluid thickener are controlled by controlling the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzene sulfonate and N-vinyl caprolactam, thereby affecting the solubility, temperature resistance and storage stability of the prepared oil fracturing fluid thickener. The oil fracturing fluid thickener prepared within the ratio range provided by the present invention can form a comb-like structure with staggered side chains, effectively improving the performance of the oil fracturing fluid thickener.

[0011] 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.

[0012] In the present invention, the molecular weight of the thickener molecules for oil production fracturing fluid 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 thickener for oil production fracturing fluid is more uniform.

[0013] 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.

[0014] The cross-linking agent can enhance the binding force between thickener molecules, form a network structure between thickener molecules, increase the viscosity of the solution, and improve the storage stability of the solution. Among them, the addition of N-hydroxymethyl acrylamide can make the thickener molecules cross-linked internally and maintain a stable state, and the addition of p-toluenesulfonic acid can make the thickener molecules cross-linked and maintain stability, which can not only increase the viscosity of the thickener, but also improve the storage stability of the thickener.

[0015] Furthermore, in step S1, the mass proportions of acrylamide, acrylic acid, emulsifier and deionized water 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.

[0016] Furthermore, the emulsifier in step S1 is one of sodium carboxymethyl cellulose, sodium glycerate, fatty acid glyceride and sorbitan fatty acid ester.

[0017] Furthermore, the mass fraction of glycerol in step S2 is 32-37 parts.

[0018] 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.

[0019] 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.

[0020] The present invention also provides a fracturing fluid thickener for oil production prepared by using the preparation method of the fracturing fluid thickener for oil production.

[0021] 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: (1) In the present invention, acrylamide and acrylic acid are used as the molecular backbone of the thickener for oil fracturing fluid, and a phosphoric acid group is introduced into the thickener molecule for oil fracturing fluid, thereby effectively improving the solubility of the thickener; (2) The present invention introduces a hydrophobic long 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; (3) The present invention uses sodium 4-vinylbenzene sulfonate 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

[0022] Figure 1 This is a scanning electron microscope image of the thickener prepared in Example 3. DETAILED DESCRIPTION

[0023] 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 idea of ​​the present invention, but as long as they do not deviate from the basic idea of ​​the present invention, they are all within the scope of the present invention.

[0024] Example 1 A method for preparing a fracturing fluid thickener for oil production comprises the following steps: 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; S2: 32 g of glycerol, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzene sulfonate, and N-vinyl caprolactam were mixed uniformly to obtain an oil phase; S3: adding the aqueous phase obtained in step S1 to the oil phase obtained in step S2 under stirring at a rotation 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, cooling, and obtaining a fracturing fluid thickener for oil production; The molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinyl caprolactam 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.

[0025] Example 2 A method for preparing a fracturing fluid thickener for oil production comprises the following steps: 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; S2: 37 g of glycerol, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate, and N-vinyl caprolactam were mixed uniformly to obtain an oil phase; S3: adding the aqueous phase obtained in step S1 to the oil phase obtained in step S2 under stirring at a rotation 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, cooling, and obtaining a fracturing fluid thickener for oil production; The molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinyl caprolactam 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.

[0026] Example 3 A method for preparing a fracturing fluid thickener for oil production comprises the following steps: 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; S2: 36 g of glycerol, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate, and N-vinyl caprolactam were mixed uniformly to obtain an oil phase; S3: adding the aqueous phase obtained in step S1 to the oil phase obtained in step S2 under stirring at a rotation speed of 1350 rpm, stirring evenly, adding 2.5 g of sodium bisulfite and 2.3 g of ammonium persulfate under a nitrogen atmosphere, heating to 48° C., reacting for 4.3 h, adding 4 g of 2,6-di-tert-butyl-p-cresol and 8 g of a cross-linking agent, stirring and reacting for 35 min, cooling, and obtaining a fracturing fluid thickener for oil production; The molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinyl caprolactam 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.

[0027] Comparative Example 1 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.

[0028] Comparative Example 2 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.

[0029] Comparative Example 3 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.

[0030] Comparative Example 4 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-vinylbenzene sulfonate in this comparative example.

[0031] Comparative Example 5 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-vinylbenzene sulfonate and N-vinyl caprolactam in this comparative example is 20:4:9:11:13.

[0032] Comparative Example 6 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.

[0033] Comparative Example 7 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.

[0034] Test example 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%, and the acid solution was tested at a shear rate of 170s at 30°C, 100°C, 150°C, 200°C and 250°C. -1 The endpoint apparent viscosity under the conditions is shown in Table 1.

[0035] Storage stability test: The thickeners prepared in Examples 1 to 3, Comparative Example 2, Comparative Example 5 to Comparative Example 7 were placed at room temperature (25-30° C.) for 6 months and 12 months respectively to observe whether the thickeners were stratified. The test results are shown in Table 2.

[0036] Salt resistance test: According to Q / JRF135-2021 "Thickener Polymers for Fracturing Fluids JRYLZG", the thickeners prepared in Examples 1 to 3 were tested for salt resistance, and their viscosity retention rates in brine were recorded. The test results are shown in Table 3.

[0037] Scanning electron microscope test: The thickener prepared in Example 3 was placed in a vacuum drying oven for drying, and then gold-plated. The microscopic morphology and structural characteristics of the polymer were observed using a scanning electron microscope. Figure 1 .

[0038] Table 1 Temperature resistance test results

[0039] As shown in Table 1, the apparent viscosity of the fracturing fluid thickener for oil production 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, which fully demonstrates that the fracturing fluid thickener for oil production 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.

[0040] Compared with Example 3, Comparative Example 1 uses an equal amount of acrylic acid to replace octadecyl methacrylate, but the temperature resistance of the obtained thickener is poor, which shows that octadecyl methacrylate can introduce long-chain alkyl esters into the molecular side chains of the thickener, enhance the interaction between the thickener molecules, and improve the temperature resistance of the thickener; Comparative Example 3 uses an equal amount of methyl acrylate to replace N-vinyl caprolactam, and Comparative Example 4 uses an equal amount of methyl acrylate to replace sodium 4-vinylbenzene sulfonate, but the temperature resistance of the obtained thickener is poor, which shows that N-vinyl caprolactam and 4-vinylbenzene 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-vinylbenzene sulfonate and N-vinyl caprolactam, but the temperature resistance of the prepared thickener deteriorated, which shows that the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzene sulfonate and N-vinyl caprolactam in the present invention has been optimized, and changing the molar ratio will affect the side chain structure of the thickener molecule, resulting in poor temperature resistance.

[0041] Table 2 Storage stability test results

[0042] As can be seen from Table 2, the thickener for oil fracturing fluid provided by the present invention does not show stratification phenomenon after being placed at room temperature for 6 months and 12 months, which fully demonstrates that the thickener for oil fracturing fluid provided by the present invention has good storage stability.

[0043] 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 indicates 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-vinyl caprolactam, but the obtained thickener shows stratification after being placed for 12 months, which indicates that the molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinyl caprolactam is changed. -The molar ratio of sodium vinylbenzenesulfonate and N-vinylcaprolactam will affect the side chain structure of the thickener molecule, and thus affect its storage stability; the crosslinking agent in Comparative Example 6 is all N-hydroxymethyl acrylamide, and the mass ratio of N-hydroxymethyl acrylamide and p-toluenesulfonic acid is changed in Comparative Example 7, but the obtained thickener shows stratification after being placed for 6 months, which shows that the use of N-hydroxymethyl acrylamide and p-toluenesulfonic acid in a certain mass ratio to form a crosslinking agent in the present invention can effectively improve the storage stability of the thickener, and changing the components or ratios will lead to poor storage stability of the thickener.

[0044] Table 3 Salt resistance test results

[0045] It can be seen from Table 3 that the viscosity retention rate of the oil fracturing fluid thickener provided by the present invention in brine is 74.9%-81.3%, which indicates that the oil fracturing fluid thickener provided by the present invention has good salt resistance.

[0046] Depend on Figure 1 It can be seen that the molecular chains of the thickener for oil fracturing fluid provided by the present invention are in 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.

[0047] The above embodiments are merely illustrative of the present invention, and are not intended to limit the present invention. Those skilled in the art should not modify the above embodiments without violating the spirit and scope of the present invention. All equivalent modifications or changes made by those with ordinary knowledge in the relevant technical field without departing from the technical concept of the present invention still 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: mixing glycerol, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzene sulfonate and N-vinyl caprolactam to obtain an oil phase; S3: Add the water 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, cool, and obtain a fracturing fluid thickener for oil production.

2. The method for preparing a fracturing fluid thickener for oil production according to claim 1, characterized in that: The molar ratio of acrylic acid, octadecyl methacrylate, vinyl phosphoric acid, sodium 4-vinylbenzenesulfonate and N-vinyl caprolactam is 19-21:11-13:3-5:4-7:3-5.

3. The method for preparing a fracturing fluid thickener for oil production according to claim 1, characterized in that: In step S3, the chain transfer agent is one of trichloroethylene, tetrachloromethane and 2,6-di-tert-butyl-p-cresol, and the cross-linking agent is composed of N-hydroxymethyl acrylamide and p-toluenesulfonic acid in a mass ratio of 3-5:7-9.

4. The method for preparing a fracturing fluid thickener for oil production according to claim 3, characterized in that: 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.

5. The method for preparing a fracturing fluid thickener for oil production according to claim 1, characterized in that: 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.

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

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

8. The method for preparing a fracturing fluid thickener for oil production according to claim 1, characterized in that: 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.

9. The method for preparing a fracturing fluid thickener for oil production according to claim 1, characterized in that: The initiator in step S3 is composed of 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.

10. A fracturing fluid thickener for oil production obtained according to the method for preparing a fracturing fluid thickener for oil production according to any one of claims 1 to 9.

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