Temperature-resistant and salt-resistant thickening agent for fracturing and preparation method thereof

Abstract

The present application relates to the technical field of thickening agent, and is a kind of temperature-resistant and salt-resistant thickening agent for fracturing and a preparation method thereof.The raw materials of the former include acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer, associated monomer and functional monomer, and are obtained by the following method: a required amount of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer, associated monomer and functional monomer are mixed and dissolved in water to obtain a mixed solution, then the pH of the mixed solution is adjusted, the mixed solution is refrigerated, a required amount of low-temperature composite initiator is added to generate a polymerization reaction to obtain a colloidal product, and the colloidal product is cut, sieved and dried to obtain the product.The present application utilizes the triple action of "intrinsic strengthening + association promotion + electrostatic retention" to greatly improve the temperature resistance and salt resistance of the temperature-resistant and salt-resistant thickening agent for fracturing.

Description

Technical Field

[0001] This invention relates to the field of thickener technology, specifically a temperature- and salt-resistant thickener for fracturing and its preparation method. Background Technology

[0002] Fracturing is a crucial technology for achieving large-scale, efficient development of unconventional resources such as tight oil and gas. Fracturing fluid is an essential chemical working fluid used in the fracturing process, and its performance significantly impacts the final stimulation effect and oil and gas recovery rate. Thickeners, as a key component of fracturing fluids, are particularly important for ensuring the drag reduction and proppant carrying properties of the fracturing fluid system due to their temperature and salt resistance. Because of their high drag reduction, strong thickening ability, good gel breaking performance, low residue content, and insensitivity to bacteria, synthetic polymers have gradually become one of the mainstream directions for the research and application of fracturing fluid thickeners.

[0003] As reservoir stimulation continues to advance and expand in scale, fracturing for increased production is moving towards deeper oil and gas formations with greater burial depth, higher temperatures, and higher formation salinity. Simultaneously, the urgent need to reuse flowback fluid to prepare fracturing fluids in the field poses a significant challenge to the salt resistance of fracturing fluid thickeners. Currently, conventional polyacrylamide polymers are the most mature synthetic polymers used, but their temperature and salt resistance are quite limited. Under high temperature and high salinity conditions (especially in the presence of high-valence ions), viscosity loss is significant, and even flocculation and precipitation occur, leading to a significant decrease in overall viscoelasticity and sand-carrying capacity.

[0004] Chinese patent document CN105646772A discloses a hydrophobic associating polymer and its preparation method. The method uses one or more of allyl alkyl quaternary ammonium salt, acrylamide alkyl sulfonic acid and its sulfonate, alkylphenol polyoxyethylene acrylate and alkyl acrylate polyoxyethylene alkyl ester as hydrophobic monomers to prepare a hydrophobic associating polymer. Under the conditions of 50000 mg / L (calcium and magnesium ions 2000 mg / L) mineralization and 90℃, the viscosity of 0.2% polymer is 40 mPa·s.

[0005] Chinese patent document CN113402660A discloses a polymer for oil production in high-temperature, high-salinity, and high-hardness reservoirs, its preparation method, and its application. The polymer incorporates organic carboxylic acid monomer units containing acrylimide groups, acrylamide monomer units, N-alkyl-substituted acrylamide sulfonic acid monomer units, and polyol monomer units containing ethylene aniline groups. Under conditions of 40,000 mg / L (calcium and magnesium ions 2,000 mg / L) salinity and 90°C, the viscosity of 0.2% polymer is greater than 35 mPa·s.

[0006] Chinese patent document CN109705834A discloses a composition, a temperature-resistant and salt-resistant fracturing fluid thickener prepared using the composition, and a method for preparing the same. The thickener is prepared by copolymerization of acrylamide, acrylic acid, hydrophobic monomer, 2-acrylamide-2-methylpropanesulfonic acid, rigid monomer, surfactant, and shielding agent. Under conditions of 50,000 mg / L (calcium and magnesium ions 3,500 mg / L) salinity and 160°C, the viscosity of the 0.35% polymer is greater than 70.5 mPa·s after aging for 2 hours.

[0007] Chinese patent document CN110540618A discloses a method for preparing a temperature- and salt-resistant copolymer. The method uses polyacryloyloxyethyltrimethylammonium chloride or polymethacrylamidepropyltrimethylammonium chloride as a template and sulfonic acid derivatives containing terminal alkenyl groups and their sulfonate derivatives as functional monomers to copolymerize with acrylamide to prepare a temperature- and salt-resistant copolymer. Under the conditions of 55000 mg / L (calcium and magnesium ions 5000 mg / L) mineralization and 100℃, the viscosity of 0.2% polymer is greater than 15 mPa·s.

[0008] Liu Tongyi et al. from Southwest Petroleum University prepared a fracturing fluid thickener by copolymerizing acrylamide, N-hydroxymethylacrylamide (NMA) and hydrophobic cationic monomers. Under the conditions of 1% KCl and 100℃, the viscosity of 0.35% polymer was greater than 53 mPa·s (Liu Tongyi, Synthesis and Evaluation of an Aluminum Crosslinked Fracturing Fluid Thickener, Petrochemical Technology, 2018, 47(2)).

[0009] Tang Tang of Southwest Petroleum University prepared a thickener for high-sand-ratio, low-damage fracturing fluid by copolymerizing acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl dimethyl allyl ammonium chloride, and N,N-methylenebisacrylamide. Under the conditions of 1% KCl and 90℃, the viscosity of 0.4% polymer was greater than 57.44 mPa·s (Tang Tang, Research on a High-Sand-Ratio, Low-Damage Fracturing Fluid, Southwest Petroleum University, 2018).

[0010] The existing publicly available Chinese patent and journal articles mainly use copolymerization of acrylamide short-chain alkyl sulfonic acids or sulfonates or (and) rigid monomers containing unsaturated double bonds, as well as self-associative acrylamide long-chain alkyl sulfonic acids or sulfonates or long-chain alkyl quaternary ammonium salts or long-chain alkyl acrylamides to prepare temperature- and salt-resistant thickeners. However, their temperature, salt, and shear resistance are very limited. For example, under conditions of 50,000 mg / L (5,000 mg / L calcium and magnesium ions) salinity and 120°C, 0.15% to 0.2% thickener fails to achieve the desired effect within 170 seconds. -1 After shearing for 2 hours, the viscosity is difficult to reach 25 mPa·s or higher. Summary of the Invention

[0011] This invention provides a temperature- and salt-resistant thickener for fracturing and its preparation method, which overcomes the shortcomings of the prior art and can effectively solve the problem of poor temperature resistance, salt resistance and shear resistance of existing thickeners.

[0012] One of the technical solutions of the present invention is achieved through the following measures: a temperature-resistant and salt-resistant thickener for fracturing, the raw materials comprising acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer, associative monomer and functional monomer in a mass ratio of 1:(0.15 to 0.3):(0.02 to 0.2):(0.004 to 0.06):(0.00004 to 0.0005).

[0013] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0014] The aforementioned salt-resistant monomers are one or more of acrylamide short-chain alkyl sulfonic acid / sulfonate salt-resistant monomers and rigid salt-resistant monomers containing unsaturated double bonds, and the associating monomers are one or more of acrylamide long-chain alkyl sulfonic acid / sulfonate associating monomers.

[0015] The above-mentioned acrylamide short-chain alkyl sulfonic acid / sulfonate salt-resistant monomer has the following structural formula:

[0016]

[0017] Where n is between 1 and 3.

[0018] The above-mentioned rigid salt-resistant monomer containing unsaturated double bonds has the following structural formula:

[0019]

[0020] The above-mentioned acrylamide long-chain alkyl sulfonic acid / sulfonate associating monomer has the following structural formula:

[0021]

[0022] Where n is between 11 and 19.

[0023] The aforementioned functional monomers are modified graphene oxide functional monomers containing unsaturated double bonds.

[0024] The above-mentioned modified graphene oxide functional monomers containing unsaturated double bonds were obtained by the following method:

[0025] The first step involves adding the required amount of graphene oxide to a 95% ethanol aqueous solution under stirring, followed by the required amount of silane coupling agent containing unsaturated double bonds. The mixture is then refluxed at 65°C to 90°C for 2.5 to 4.5 hours to obtain a reaction mixture. The mass ratio of graphene oxide to silane coupling agent containing unsaturated double bonds is 1:(3 to 5).

[0026] The second step involves cooling and allowing the reaction mixture to stand for 12 hours, then washing it with acetone, vacuum filtering it, and drying it at 70°C to 90°C for 12 hours to obtain a modified graphene oxide functional monomer containing unsaturated double bonds.

[0027] In the first step above, the vinyl silane coupling agent is one or more of the following: vinyltrimethoxysilane, vinyltriethoxysilane, methacryloyloxymethyltrimethoxysilane, methacryloyloxymethyltriethoxysilane, methacryloyloxyethyltrimethoxysilane, methacryloyloxyethyltriethoxysilane, methacryloyloxypropyltrimethoxysilane, methacryloyloxypropyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane.

[0028] The above-mentioned temperature-resistant and salt-resistant thickener for fracturing is obtained by the following method:

[0029] S1, mix the required amounts of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer, associative monomer and functional monomer in water to obtain a mixed solution;

[0030] S2, after adjusting the pH of the mixed solution, refrigerate the mixed solution, and then add the required amount of low-temperature composite initiator to carry out a polymerization reaction to obtain a colloidal product. After cutting, sieving and drying the colloidal product, a temperature-resistant and salt-resistant thickener for fracturing is obtained.

[0031] In step S1 above, the mass concentration of the solute in the mixed solution is 20% to 30%.

[0032] In step S2 above, the pH of the mixed solution is adjusted to 7 to 9 using sodium bicarbonate solution, the refrigeration time is 30 to 40 minutes, and the polymerization reaction temperature is 0°C to 25°C.

[0033] In step S2 above, the low-temperature composite initiator is a mixture of sodium persulfate, sodium bisulfite and azobisisobutyramidine hydrochloride in a volume ratio of 1:1:0.5, and the volume ratio of the low-temperature composite initiator to the mixed solution is 1:200.

[0034] The second technical solution of the present invention is achieved through the following measures: a method for preparing a temperature-resistant and salt-resistant thickener for fracturing, which is carried out according to the following method:

[0035] S1, mix the required amounts of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer, associative monomer and functional monomer in water to obtain a mixed solution;

[0036] S2, after adjusting the pH of the mixed solution, refrigerate the mixed solution, and then add the required amount of low-temperature composite initiator to carry out a polymerization reaction to obtain a colloidal product. After cutting, sieving and drying the colloidal product, a temperature-resistant and salt-resistant thickener for fracturing is obtained.

[0037] This invention integrates acrylamide short-chain alkyl sulfonic acid / sulfonate salt-resistant monomers or rigid salt-resistant monomers containing unsaturated double bonds, acrylamide long-chain alkyl sulfonic acid / sulfonate associative monomers with self-association ability, and modified graphene oxide functional monomers with strong thermal stability and two-dimensional planar structure containing unsaturated double bonds into a polymer backbone. By utilizing the triple effects of "inherent reinforcement + association promotion + electrostatic enhancement", the temperature and salt resistance performance of the fracturing temperature and salt-resistant thickener of this invention is significantly improved. Attached Figure Description

[0038] Figure 1 The infrared spectrum of the graphene oxide modified with unsaturated double bonds prepared in Example 16 of this invention is shown.

[0039] Figure 2 A comparison diagram of the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 16 of the present invention at a concentration of 0.15% and the temperature-resistant and shear-resistant thickener of Comparative Example 1.

[0040] Figure 3 A comparison diagram of the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 27 of the present invention at a concentration of 0.15% and the temperature-resistant and shear-resistant thickener of Comparative Example 3.

[0041] Figure 4 A comparison diagram of the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 29 of the present invention at a concentration of 0.15% and the temperature-resistant and shear-resistant thickener of Comparative Example 5.

[0042] Figure 5 A comparison diagram of the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 31 of the present invention at a concentration of 0.15% and the temperature-resistant and shear-resistant thickener of Comparative Example 7.

[0043] Figure 6 A comparison diagram of the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 33 of the present invention at a concentration of 0.15% and the temperature-resistant and shear-resistant thickener of Comparative Example 1.

[0044] Figure 7 A comparison diagram of the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 35 of the present invention at a concentration of 0.15% and the temperature-resistant and shear-resistant thickener of Comparative Example 1.

[0045] Figure 8 The figure shows a comparison between the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 26 of the present invention at a concentration of 0.3% and the temperature-resistant and shear-resistant thickener of Comparative Example 2.

[0046] Figure 9 A comparison diagram of the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 28 of the present invention at a concentration of 0.3% and the temperature-resistant and shear-resistant thickener of Comparative Example 4.

[0047] Figure 10A comparison diagram of the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 30 of the present invention at a concentration of 0.3% and the temperature-resistant and shear-resistant thickener of Comparative Example 6.

[0048] Figure 11 The image shows a comparison between the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 32 of the present invention at a concentration of 0.3% and the temperature-resistant and shear-resistant thickener of Comparative Example 8.

[0049] Figure 12 The figure shows a comparison between the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 34 of the present invention at a concentration of 0.3% and the temperature-resistant and shear-resistant thickener of Comparative Example 2.

[0050] Figure 13 The figure shows a comparison between the temperature-resistant and salt-resistant thickener for fracturing prepared in Example 36 of the present invention at a concentration of 0.3% and the temperature-resistant and shear-resistant thickener of Comparative Example 2.

[0051] Figure 14 The image shows a comparison of the thixotropic energy of the 0.15% concentration of the temperature- and salt-resistant thickener for fracturing according to this invention.

[0052] Figure 15 The image shows a comparison of the thixotropic energy of the 0.3% concentration of the temperature- and salt-resistant thickener for fracturing according to this invention. Detailed Implementation

[0053] This invention is not limited to the following embodiments; specific implementation methods can be determined according to the technical solution of this invention and actual conditions. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art; unless otherwise specified, all percentages in this invention are mass percentages.

[0054] The present invention will be further described below with reference to embodiments:

[0055] Example 1: The fracturing temperature-resistant and salt-resistant thickener comprises acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer, associative monomer and functional monomer in a mass ratio of 1:(0.15 to 0.3):(0.02 to 0.2):(0.004 to 0.06):(0.00004 to 0.0005).

[0056] Example 2: As an optimization of the above example, the salt-resistant monomer is one or more of acrylamide short-chain alkyl sulfonic acid / sulfonate salt-resistant monomer and rigid salt-resistant monomer containing unsaturated double bonds, and the associating monomer is one or more of acrylamide long-chain alkyl sulfonic acid / sulfonate associating monomer.

[0057] Example 3: As an optimization of the above examples, the acrylamide short-chain alkyl sulfonic acid / sulfonate salt-resistant monomer has the following structural formula:

[0058]

[0059] Where n is between 1 and 3.

[0060] In this invention, the acrylamide short-chain alkyl sulfonic acid / sulfonate salt-resistant monomer is one or more of sodium 2-acrylamido-2-methylpropanesulfonate, sodium 2-acrylamido-2-ethylbutanesulfonate, sodium 2-acrylamido-2-propylpentanesulfonate, and sodium 2-acrylamido-2-butylhexanesulfonate.

[0061] Example 4: As an optimization of the above examples, a rigid salt-resistant monomer containing unsaturated double bonds has the following structural formula:

[0062]

[0063] In this invention, one or more of the rigid salt-resistant monomers containing unsaturated double bonds, namely sodium p-acrylamidobenzenesulfonate, sodium p-vinylbenzenesulfonate, and N-vinylpyrrolidone, are used.

[0064] Example 5: As an optimization of the above examples, the acrylamide long-chain alkyl sulfonic acid / sulfonate associative monomer has the following structural formula:

[0065]

[0066] Where n is between 11 and 19.

[0067] In this invention, the acrylamide long-chain alkyl sulfonic acid / sulfonate associating monomer is one or more of sodium 2-acrylamidododecyl sulfonate, sodium 2-acrylamidotetradecyl sulfonate, sodium 2-acrylamidohexadecyl sulfonate, sodium 2-acrylamidooctadecyl sulfonate, and sodium 2-acrylamidoeicosyl sulfonate.

[0068] Example 6: As an optimization of the above examples, the functional monomer is a modified graphene oxide functional monomer containing unsaturated double bonds.

[0069] Example 7: As an optimization of the above examples, a modified graphene oxide functional monomer containing unsaturated double bonds was obtained by the following method:

[0070] The first step involves adding the required amount of graphene oxide to a 95% ethanol aqueous solution under stirring, followed by the required amount of silane coupling agent containing unsaturated double bonds. The mixture is then refluxed at 65°C to 90°C for 2.5 to 4.5 hours to obtain a reaction mixture. The mass ratio of graphene oxide to silane coupling agent containing unsaturated double bonds is 1:(3 to 5).

[0071] The second step involves cooling and allowing the reaction mixture to stand for 12 hours, then washing it with acetone, vacuum filtering it, and drying it at 70°C to 90°C for 12 hours to obtain a modified graphene oxide functional monomer containing unsaturated double bonds.

[0072] The modified graphene oxide functional monomer containing unsaturated double bonds prepared in this invention has the following structural formula:

[0073]

[0074] Example 8: As an optimization of the above embodiment, in the first step, the vinyl silane coupling agent is one or more of vinyltrimethoxysilane, vinyltriethoxysilane, methacryloyloxymethyltrimethoxysilane, methacryloyloxymethyltriethoxysilane, methacryloyloxyethyltrimethoxysilane, methacryloyloxyethyltriethoxysilane, methacryloyloxypropyltrimethoxysilane, methacryloyloxypropyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane.

[0075] Example 9: As an optimization of the above examples, a temperature- and salt-resistant thickener for fracturing is obtained by the following method:

[0076] S1, mix the required amounts of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer, associative monomer and functional monomer in water to obtain a mixed solution;

[0077] S2, after adjusting the pH of the mixed solution, refrigerate the mixed solution, and then add the required amount of low-temperature composite initiator to carry out a polymerization reaction to obtain a colloidal product. After cutting, sieving and drying the colloidal product, a temperature-resistant and salt-resistant thickener for fracturing is obtained.

[0078] The fracturing thickener prepared by this invention has a molecular weight of 5 million to 18 million Daltons.

[0079] Example 10: As an optimization of the above example, in step S1, the mass concentration of the solute in the mixed solution is 20% to 30%.

[0080] Example 11: As an optimization of the above example, in step S2, the pH of the mixed solution is adjusted to 7 to 9 with sodium bicarbonate solution, the refrigeration time is 30 min to 40 min, and the polymerization reaction temperature is 0°C to 25°C.

[0081] Example 12: As an optimization of the above example, in step S2, the low-temperature composite initiator is a mixture of sodium persulfate, sodium bisulfite and azobisisobutyramidine hydrochloride in a volume ratio of 1:1:0.5, and the volume ratio of the low-temperature composite initiator to the mixed solution is 1:200.

[0082] Example 13:

[0083] The modified graphene oxide functional monomer containing unsaturated double bonds was obtained by the following method:

[0084] The first step involves adding the required amount of graphene oxide to a 95% ethanol aqueous solution under stirring, followed by the required amount of silane coupling agent (vinyltrimethoxysilane) containing unsaturated double bonds. The mixture is then refluxed at 65°C for 2.5 hours to obtain a reaction mixture. The mass ratio of graphene oxide to silane coupling agent containing unsaturated double bonds is 1:3.

[0085] The second step involves cooling and allowing the reaction mixture to stand for 12 hours, then washing it with acetone, vacuum filtering it, and drying it at 70°C for 12 hours to obtain a modified graphene oxide functional monomer containing unsaturated double bonds.

[0086] This fracturing temperature-resistant and salt-resistant thickener comprises acrylamide, sodium acrylate, salt-resistant monomer (sodium 2-acrylamido-2-methylpropanesulfonate), associative monomer (sodium 2-acrylamido-dodecyl sulfonate), and functional monomer (modified graphene oxide functional monomer containing unsaturated double bonds) in a mass ratio of 1:0.15:0.02:0.004:0.00004, obtained by the following method:

[0087] S1, mix the required amounts of acrylamide, sodium acrylate, salt-resistant monomer, associating monomer and functional monomer and dissolve them in water to obtain a mixed solution with a mass concentration of 20%;

[0088] S2, after adjusting the pH of the mixed solution to 7 with sodium bicarbonate solution, the mixed solution was placed in a freezer for 30 minutes to cool to 0°C. Then, the required amount of low-temperature composite initiator (a mixture of sodium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride in a volume ratio of 1:1:0.5) was added to initiate a polymerization reaction. The reaction ended when the temperature rose to its maximum and then dropped by no more than 1°C, yielding a colloidal product. The colloidal product was then cut, sieved, and dried to obtain a temperature-resistant and salt-resistant thickener for fracturing. The volume ratio of the low-temperature composite initiator to the mixed solution was 1:200.

[0089] Example 14:

[0090] The modified graphene oxide functional monomer containing unsaturated double bonds was obtained by the following method:

[0091] The first step involves adding the required amount of graphene oxide to a 95% ethanol aqueous solution under stirring, followed by the required amount of a silane coupling agent containing unsaturated double bonds (methacryloyloxymethyltrimethoxysilane). The mixture is then refluxed at 90°C for 4.5 hours to obtain a reaction mixture. The mass ratio of graphene oxide to the silane coupling agent containing unsaturated double bonds is 1:5.

[0092] The second step involves cooling and allowing the reaction mixture to stand for 12 hours, then washing it with acetone, vacuum filtering it, and drying it at 90°C for 12 hours to obtain a modified graphene oxide functional monomer containing unsaturated double bonds.

[0093] This fracturing temperature-resistant and salt-resistant thickener comprises acrylamide, sodium acrylate, salt-resistant monomer (sodium 2-acrylamido-2-ethylbutanesulfonate), associative monomer (sodium 2-acrylamidotetradecyl sulfonate), and functional monomer (modified graphene oxide functional monomer containing unsaturated double bonds) in a mass ratio of 1:0.3:0.2:0.06:0.0005, obtained by the following method:

[0094] S1, mix the required amounts of acrylamide, sodium acrylate, salt-resistant monomer, associating monomer and functional monomer and dissolve them in water to obtain a mixed solution with a mass concentration of 30%;

[0095] S2, after adjusting the pH of the mixed solution to 9 with sodium bicarbonate solution, the mixed solution was placed in a freezer for 40 minutes to lower the temperature to 25°C. Then, the required amount of low-temperature composite initiator (a mixture of sodium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride in a volume ratio of 1:1:0.5) was added to initiate a polymerization reaction. The reaction ended when the temperature rose to its maximum and then dropped by no more than 1°C, yielding a colloidal product. The colloidal product was then cut, sieved, and dried to obtain a temperature-resistant and salt-resistant thickener for fracturing. The volume ratio of the low-temperature composite initiator to the mixed solution was 1:200.

[0096] Example 15:

[0097] The modified graphene oxide functional monomer containing unsaturated double bonds was obtained by the following method:

[0098] The first step involves adding the required amount of graphene oxide to a 95% ethanol aqueous solution under stirring, followed by the required amount of a silane coupling agent (allyltriethoxysilane) containing unsaturated double bonds. The mixture is then refluxed at 80°C for 3.5 hours to obtain a reaction mixture. The mass ratio of graphene oxide to the silane coupling agent containing unsaturated double bonds is 1:4.

[0099] The second step involves cooling and allowing the reaction mixture to stand for 12 hours, then washing it with acetone, vacuum filtering it, and drying it at 80°C for 12 hours to obtain a modified graphene oxide functional monomer containing unsaturated double bonds.

[0100] This fracturing temperature-resistant and salt-resistant thickener comprises acrylamide, sodium acrylate, salt-resistant monomer (N-vinylpyrrolidone), associative monomer (sodium 2-acrylamidoeicosyl sulfonate), and functional monomer (modified graphene oxide functional monomer containing unsaturated double bonds) in a mass ratio of 1:0.2:0.1:0.03:0.0002, and is obtained by the following method:

[0101] S1, mix the required amounts of acrylamide, sodium acrylate, salt-resistant monomer, associating monomer and functional monomer and dissolve them in water to obtain a mixed solution with a mass concentration of 20% to 30%;

[0102] S2, after adjusting the pH of the mixed solution to 8 with sodium bicarbonate solution, the mixed solution was placed in a freezer for 35 minutes to lower the temperature to 15°C. Then, the required amount of low-temperature composite initiator (a mixture of sodium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride in a volume ratio of 1:1:0.5) was added to initiate a polymerization reaction. The reaction ended when the temperature reached its maximum and then dropped by no more than 1°C, yielding a colloidal product. The colloidal product was then cut, sieved, and dried to obtain a temperature-resistant and salt-resistant thickener for fracturing. The volume ratio of the low-temperature composite initiator to the mixed solution was 1:200.

[0103] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0104] This invention integrates acrylamide short-chain alkyl sulfonic acid / sulfonate salt-resistant monomers or rigid salt-resistant monomers containing unsaturated double bonds, acrylamide long-chain alkyl sulfonic acid / sulfonate associative monomers with self-association ability, and modified graphene oxide functional monomers with strong thermal stability and two-dimensional planar structure containing unsaturated double bonds into a polymer backbone. Utilizing the triple effects of "inherent reinforcement + association promotion + electrostatic enhancement," the temperature and salt resistance performance of the fracturing temperature-resistant and salt-resistant thickener of this invention is significantly improved. Under conditions of 50,000 mg / L mineralization (calcium and magnesium ion content 5,000 mg / L) and 120°C, a concentration of 0.15% to 0.30% of the thickener can achieve a temperature and salt resistance of 170 seconds. -1 After shearing for 2 hours, the viscosity reaches 25 mPa·s to 55 mPa·s, and the thixotropic energy reaches 1000 Pa / s to 2300 Pa / s.

[0105] Example 16:

[0106] The modified graphene oxide functional monomer containing unsaturated double bonds was obtained by the following method:

[0107] First, at a stirring speed of 500 r / min, 1 g of graphene oxide was added to 800 mL of 95% ethanol aqueous solution, followed by 3 g of silane coupling agent (vinyltriethoxysilane) containing unsaturated double bonds. The mixture was then subjected to reflux at 80 °C for 2.5 h to obtain a reaction mixture.

[0108] The second step involved cooling and allowing the reaction mixture to stand for 12 hours. After washing with 100 mL of acetone, the mixture was vacuum filtered and dried at 70 °C for 12 hours to obtain a modified graphene oxide functional monomer containing unsaturated double bonds, labeled as MGO-1.

[0109] This fracturing-resistant, temperature- and salt-tolerant thickener is obtained according to the following method:

[0110] S1, acrylamide, sodium acrylate, salt-resistant monomer (sodium 2-acrylamido-2-methylpropanesulfonate), associative monomer (sodium 2-acrylamidotetradecyl sulfonate), and functional monomer (modified graphene oxide functional monomer MGO-1 containing unsaturated double bonds) in a mass ratio of 1:0.15:0.02:0.004:0.00004 are mixed and dissolved in water to obtain a mixed solution with a mass concentration of 25%.

[0111] S2, after adjusting the pH of the mixed solution to 8 with sodium bicarbonate solution, 1000 mL of the mixed solution was placed in a freezer for 30 to 40 minutes to lower the temperature to 0°C. Then, 5 mL of low-temperature composite initiator (a mixture of sodium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride in a volume ratio of 1:1:0.5) was added to initiate the polymerization reaction. An electronic thermometer was inserted to monitor the reaction temperature. The reaction ended when the temperature reached its maximum and then dropped by no more than 1°C, yielding a colloidal product. The colloidal product was cut into small particles of about 5 mm, sieved through an 80-mesh sieve, and dried at 95°C to obtain a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80, labeled as NTSP-1.

[0112] Comparative Example 1: The difference from Example 16 of the present invention is that, in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the modified graphene oxide functional monomer MGO-1 containing unsaturated double bonds was not added to the raw materials, and the fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥ 80 mesh was obtained, which was labeled as DBP-1.

[0113] Example 17: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.3:0.02:0.004:0.00004. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 is obtained, which is labeled as NTSP-2.

[0114] Example 18: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.15:0.2:0.004:0.00004. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 is obtained, which is marked as NTSP-3.

[0115] Example 19: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.15:0.02:0.06:0.00004. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 mesh is obtained, which is marked as NTSP-4.

[0116] Example 20: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.15:0.02:0.004:0.0005. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 is obtained, which is marked as NTSP-5.

[0117] Example 21: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.3:0.2:0.004:0.00004. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 is obtained, which is marked as NTSP-6.

[0118] Example 22: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.3:0.02:0.06:0.00004. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 is obtained, which is marked as NTSP-7.

[0119] Example 23: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.3:0.02:0.004:0.0005. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 is obtained, which is marked as NTSP-8.

[0120] Example 24: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.3:0.2:0.004:0.00004. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 is obtained, which is marked as NTSP-9.

[0121] Example 25: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.3:0.2:0.06:0.00004. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 is obtained, which is marked as NTSP-10.

[0122] Example 26: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the mass ratio of the raw materials in step S1 is changed to 1:0.3:0.2:0.06:0.0005. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 is obtained, which is marked as NTSP-11.

[0123] Comparative Example 2: The difference from Example 26 of the present invention is that, in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the modified graphene oxide functional monomer MGO-1 containing unsaturated double bonds was not added to the raw materials, and the fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥ 80 mesh was obtained, which was labeled as DBP-2.

[0124] Example 27: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the salt-resistant monomer is replaced with sodium p-acrylamidobenzenesulfonate. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 mesh is obtained, which is marked as NTSP-12.

[0125] Comparative Example 3: The difference from Example 27 of the present invention is that, in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the modified graphene oxide functional monomer MGO-1 containing unsaturated double bonds was not added to the raw materials, and the fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥ 80 mesh was obtained, which was labeled as DBP-3.

[0126] Example 28: The difference from Example 26 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the salt-resistant monomer is replaced with sodium p-acrylamidobenzenesulfonate. The remaining steps are the same as in Example 26, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 mesh is obtained, which is marked as NTSP-13.

[0127] Comparative Example 4: The difference from Example 28 of the present invention is that, in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the modified graphene oxide functional monomer MGO-1 containing unsaturated double bonds was not added to the raw materials, and the fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥ 80 mesh was obtained, which was labeled as DBP-4.

[0128] Example 29: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the salt-resistant monomer is replaced with sodium p-vinylbenzenesulfonate. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 mesh is obtained, which is marked as NTSP-14.

[0129] Comparative Example 5: The difference from Example 29 of the present invention is that, in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the modified graphene oxide functional monomer MGO-1 containing unsaturated double bonds was not added to the raw materials, and the fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥ 80 mesh was obtained, which was labeled as DBP-5.

[0130] Example 30: The difference from Example 26 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the salt-resistant monomer is replaced with sodium p-vinylbenzenesulfonate. The remaining steps are the same as in Example 26, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 mesh is obtained, which is marked as NTSP-15.

[0131] Comparative Example 6: The difference from Example 30 of the present invention is that, in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the modified graphene oxide functional monomer MGO-1 containing unsaturated double bonds was not added to the raw materials, and the fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥ 80 mesh was obtained, which was labeled as DBP-6.

[0132] Example 31: The difference from Example 16 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the salt-resistant monomer is replaced with N-vinylpyrrolidone. The remaining steps are the same as in Example 16, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 mesh is obtained, which is marked as NTSP-16.

[0133] Comparative Example 7: The difference from Example 31 of the present invention is that, in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the modified graphene oxide functional monomer MGO-1 containing unsaturated double bonds was not added to the raw materials, and the fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥ 80 mesh was obtained, which was labeled as DBP-7.

[0134] Example 32: The difference from Example 26 of the present invention is that the salt-resistant monomer is replaced with N-vinylpyrrolidone. The remaining steps are the same as in Example 26, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 mesh is obtained, which is marked as NTSP-17.

[0135] Comparative Example 8: The difference from Example 32 of the present invention is that, in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the modified graphene oxide functional monomer MGO-1 containing unsaturated double bonds was not added to the raw materials, and the fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥ 80 mesh was obtained, which was marked as DBP-8.

[0136] Example 33: The difference from Example 16 of the present invention is that in the preparation process of the modified graphene oxide functional monomer containing unsaturated double bonds, the silane coupling agent of the raw material unsaturated double bonds is replaced with methacryloyloxypropyltrimethoxysilane. The remaining steps are the same as in Example 16. The modified graphene oxide functional monomer containing unsaturated double bonds is labeled as MGO-2, and the obtained fracturing temperature-resistant and salt-resistant thickener NTSP-18 with a mesh size ≥80 mesh is obtained.

[0137] Example 34: The difference from Example 26 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the raw material functional monomer is changed to the modified graphene oxide functional monomer MGO-2 containing unsaturated double bonds. The remaining steps are the same as in Example 26, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 mesh is obtained, which is marked as NTSP-19.

[0138] Example 35: The difference from Example 16 of the present invention is that in the preparation process of the modified graphene oxide functional monomer containing unsaturated double bonds, the silane coupling agent of the raw material unsaturated double bonds is replaced with allyltrimethoxysilane. The remaining steps are the same as in Example 16. The modified graphene oxide functional monomer containing unsaturated double bonds is labeled as MGO-3, and the obtained fracturing temperature-resistant and salt-resistant thickener NTSP-20 with a mesh size ≥80 mesh is obtained.

[0139] Example 36: The difference from Example 26 of the present invention is that in the preparation process of the fracturing temperature-resistant and salt-resistant thickener, the raw material functional monomer is changed to the modified graphene oxide functional monomer MGO-3 containing unsaturated double bonds. The remaining steps are the same as in Example 26, and a fracturing temperature-resistant and salt-resistant thickener with a mesh size ≥80 mesh is obtained, which is marked as NTSP-21.

[0140] Example 37: The modified graphene oxide functional monomer containing unsaturated double bonds prepared in Example 16 of this invention was characterized by Fourier transform infrared spectroscopy using the KBr pellet method. Simultaneously, the unmodified graphene oxide was used as a control. The results are as follows: Figure 1 As shown, by Figure 1 It can be seen that most of the absorption peaks corresponding to graphene oxide after modification have undergone a blue shift to some extent, at 1396 cm⁻¹. -1 The corresponding hydroxyl bending vibration peak disappears at 2920 cm⁻¹, and the peak at 2920 cm⁻¹ disappears. -1 and 2847cm -1 The newly appearing characteristic absorption peaks can be attributed to the symmetric and antisymmetric stretching vibrations of the CH bond in the methylene group (-CH2-), respectively; simultaneously, at a comparable overall absorption peak intensity, the 1622 cm⁻¹ peak... -1 The absorption peak attributable to the carbon-carbon double bond (C=C) is red-shifted to 1613 cm⁻¹ in MGO-1. -1 Furthermore, the strength was relatively enhanced, confirming that vinyl-modified graphene oxide, i.e., a modified graphene oxide functional monomer containing unsaturated double bonds, was successfully prepared.

[0141] Example 38: The viscosity-average molecular weight of the fracturing temperature-resistant and salt-resistant thickener of the present invention was determined using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the method specified in GB / T 12005.10-1992 "Determination of Molecular Weight of Polyacrylamide". The results are shown in Table 2. As can be seen from Table 2, the molecular weight range of the fracturing temperature-resistant and salt-resistant thickener of the present invention is from 5 million Daltons to 18 million Daltons.

[0142] Example 39: The performance of the temperature-resistant and salt-resistant thickener for fracturing of the present invention was tested, including temperature resistance, shear resistance and thixotropic energy.

[0143] Test method:

[0144] Solution preparation: The fracturing temperature-resistant and salt-resistant thickener of the present invention is placed in brine (total mineralization 50000 mg / L, of which calcium and magnesium ion content 5000 mg / L), and dissolved evenly at room temperature and stirring speed of 400±50 r / min to prepare a fracturing temperature-resistant and salt-resistant thickener solution with a concentration of 0.15% to 0.3% for later use.

[0145] Temperature and shear resistance: Using the RS6000 advanced rheometer PZ38 coaxial cylindrical rotor system, the temperature and shear resistance were tested at 120℃ and 170s. -1 The temperature and salt resistance thickener solution for fracturing was subjected to a temperature and shear resistance test. The viscosity change curve over time was recorded and the final stable viscosity value was recorded. The duration from heating to the end of the test was 2 hours.

[0146] Thixotropic energy: Using a Physica MCR301 advanced rheometer in rotation mode at 120°C, the thixotropic energy was measured in 0.01 s⁻¹. -1 up to 500s -1 Shear rate testing was conducted from low to high shear within the range of shear rates (stage 1, the resulting curve is an upward curve), 500s. -1 Constant shear test for 1 min (2 stages), 500 s -1 up to 0.01s -1 The test proceeded from high shear to low shear (3 stages, the resulting curves are downward curves). The hysteresis area A of the thixotropic ring, composed of the upward and downward curves showing the change of shear stress with shear rate, was calculated using the Hysteresis Area I model, thus obtaining the thixotropic energy.

[0147] The temperature resistance, shear resistance, and thixotropic energy of the fracturing temperature-resistant and salt-resistant thickeners prepared in Examples 16, 26 to 36 and Comparative Examples 1 to 8 of the present invention were tested according to the above method.

[0148] Test results: The temperature resistance and salt resistance of the fracturing thickener of this invention are as follows: Figures 2 to 13As shown, the thixotropic energy of the temperature-resistant and salt-resistant thickener for fracturing in this invention is as follows: Figure 14 and Figure 15 As shown,

[0149] Depend on Figure 2 and Figure 14 It can be seen that in Example 16 of the present invention, after introducing sodium 2-acrylamide-2-methylpropanesulfonate as the salt-resistant monomer and introducing graphene oxide MGO-1 modified with unsaturated double bonds in the raw material, the resulting temperature-resistant and salt-resistant thickener NTSP-1 for fracturing has a temperature-resistant shear-stable viscosity and thixotropic energy that are 10.89 mPa·s and 391 Pa / s higher than those of the temperature-resistant and salt-resistant thickener DBP-1 for fracturing obtained in Comparative Example 1 (without the introduction of MGO-1).

[0150] from Figures 3 to 7 and Figure 14 As can be seen, when the salt-resistant monomer is replaced with sodium p-acrylamidobenzenesulfonate, sodium p-vinylbenzenesulfonate, or N-vinylpyrrolidone, or when the unsaturated double-bond modified graphene oxide MGO-1 is replaced with MGO-2 or MGO-3, the resulting temperature-resistant and salt-resistant thickener for fracturing, at a dosage of 0.15%, exhibits a temperature-resistant shear-stabilized viscosity and thixotropic energy that are 9.84 mPa·s to 13.34 mPa·s and 299 Pa / s to 657 Pa / s, respectively, higher than those without the introduction of modified graphene oxide.

[0151] Similarly, from Figure 8 and Figure 15 As can be seen, in Example 26 of the present invention, after introducing sodium 2-acrylamide-2-methylpropanesulfonate as the salt-resistant monomer and introducing graphene oxide MGO-1 modified with unsaturated double bonds, the resulting temperature-resistant and salt-resistant thickener NTSP-1 for fracturing has a temperature-resistant shear-stable viscosity and thixotropic energy at a dosage of 0.3% that are 13.3 mPa·s and 626 Pa / s higher than those of the thickener DBP-2 (without MGO-1) obtained in Comparative Example 2.

[0152] from Figures 9 to 13 and Figure 15 As can be seen, when the salt-resistant monomer is replaced with sodium p-acrylamidobenzenesulfonate, or sodium p-vinylbenzenesulfonate, or N-vinylpyrrolidone, or when the graphene oxide containing unsaturated double bonds is replaced with MGO-2 or MGO-3, the resulting temperature-resistant and salt-resistant thickener for fracturing, at a dosage of 0.3%, exhibits a temperature-resistant shear-stabilized viscosity and thixotropic energy that are 11.46 mPa·s to 15.66 mPa·s and 495 Pa / s to 805 Pa / s, respectively, higher than those without the introduction of modified graphene oxide.

[0153] The above data results indicate that the temperature resistance, salt resistance, and shear resistance of the fracturing thickener of this invention, obtained by introducing graphene oxide modified with unsaturated double bonds, are significantly improved.

[0154] In summary, this invention utilizes a triple effect of "inherent enhancement + association promotion + electrostatic enhancement" to significantly improve the temperature and salt resistance of the fracturing temperature- and salt-resistant thickener of this invention. Under conditions of 50,000 mg / L mineralization (calcium and magnesium ion content 5,000 mg / L) and 120°C, a concentration of 0.15% to 0.30% of the thickener can achieve a temperature and salt resistance of 170 seconds. -1 After shearing for 2 hours, the viscosity reaches 25 mPa·s to 55 mPa·s, and the thixotropic energy reaches 1000 Pa / s to 2300 Pa / s.

[0155] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0156] Table 1

[0157]

[0158]

[0159] Table 2

[0160] Example 16 1800 Example 31 1704 Example 17 1720 Example 32 568 Example 18 1450 Example 33 1685 Example 19 1080 Example 34 516 Example 20 780 Example 35 1729 Example 21 950 Example 36 534 Example 22 815 Comparative Example 1 1912 Example 23 753 Comparative Example 2 678 Example 24 647 Comparative Example 3 1867 Example 25 605 Comparative Example 4 634 Example 26 565 Comparative Example 5 1829 Example 27 1725 Comparative Example 6 603 Example 28 500 Comparative Example 7 1854 Example 29 1751 Comparative Example 8 632 Example 30 548

Claims

1. A temperature-resistant and salt-resistant thickener for fracturing, characterized in that... The raw materials include acrylamide hydrophilic monomers, sodium acrylate hydrophilic monomers, salt-resistant monomers, associative monomers, and functional monomers in a mass ratio of 1:0.15 to 0.3:0.02 to 0.2:0.004 to 0.06:0.00004 to 0.0005. The salt-resistant monomer is one of acrylamide short-chain alkyl sulfonic acid / sulfonate salt-resistant monomers and rigid salt-resistant monomers containing unsaturated double bonds. The structural formula of the acrylamide short-chain alkyl sulfonic acid / sulfonate salt-resistant monomer is: n is 1 to 3; The structural formula of the rigid salt-resistant monomer containing unsaturated double bonds is: ； The associating monomer is an acrylamide long-chain alkyl sulfonic acid / sulfonate associating monomer, and its structural formula is: n is between 11 and 19; The functional monomer is a modified graphene oxide functional monomer containing unsaturated double bonds, obtained by the following method: The first step involves adding the required amount of graphene oxide to a 95% ethanol aqueous solution under stirring, followed by the required amount of silane coupling agent containing unsaturated double bonds. The mixture is then refluxed at 65°C to 90°C for 2.5 to 4.5 hours to obtain a reaction mixture. The mass ratio of graphene oxide to silane coupling agent containing unsaturated double bonds is 1:3 to 5. The second step involves cooling and allowing the reaction mixture to stand for 12 hours, then washing it with acetone, vacuum filtering it, and drying it at 70°C to 90°C for 12 hours to obtain a modified graphene oxide functional monomer containing unsaturated double bonds.

2. The temperature-resistant and salt-resistant thickener for fracturing according to claim 1, characterized in that... In the first step, the vinyl silane coupling agent is one or more of the following: vinyltrimethoxysilane, vinyltriethoxysilane, methacryloyloxymethyltrimethoxysilane, methacryloyloxymethyltriethoxysilane, methacryloyloxyethyltrimethoxysilane, methacryloyloxyethyltriethoxysilane, methacryloyloxypropyltrimethoxysilane, methacryloyloxypropyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane.

3. The fracturing-resistant and salt-resistant thickener according to claim 1 or 2, characterized in that... Obtained using the following method: S1, mix the required amounts of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer, associative monomer and functional monomer in water to obtain a mixed solution; S2, after adjusting the pH of the mixed solution, refrigerate the mixed solution, and then add the required amount of low-temperature composite initiator to carry out a polymerization reaction to obtain a colloidal product. After cutting, sieving and drying the colloidal product, a temperature-resistant and salt-resistant thickener for fracturing is obtained.

4. The temperature-resistant and salt-resistant thickener for fracturing according to claim 3, characterized in that... In step S1, the mass concentration of the solute in the mixed solution is 20% to 30%; or / and in step S2, the pH of the mixed solution is adjusted to 7 to 9 with sodium bicarbonate solution, the refrigeration time is 30 min to 40 min, and the polymerization reaction temperature is 0°C to 25°C; or / and in step S2, the low-temperature composite initiator is a mixture of sodium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride in a volume ratio of 1:1:0.5, and the volume ratio of the low-temperature composite initiator to the mixed solution is 1:

200.

5. A method for preparing a temperature-resistant and salt-resistant thickener for fracturing according to any one of claims 1 to 4, characterized in that... Perform it as follows: S1, mix the required amounts of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer, associative monomer and functional monomer in water to obtain a mixed solution; S2, after adjusting the pH of the mixed solution, refrigerate the mixed solution, and then add the required amount of low-temperature composite initiator to carry out a polymerization reaction to obtain a colloidal product. After cutting, sieving and drying the colloidal product, a temperature-resistant and salt-resistant thickener for fracturing is obtained.

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