A thickener for high-temperature acidification and its preparation method

Abstract

This invention relates to a thickener for high-temperature acidizing and its preparation method, belonging to the field of petroleum additives technology. The thickener comprises the following components by weight percentage: 37-45 wt% modified CMC thickener, 5.2-7.0 wt% co-solvent, 1.2-1.6 wt% dispersant, and 2.4-3.1 wt% stabilizer, with the balance being water. The modified CMC thickener uses carboxymethyl cellulose as a matrix and incorporates side chains containing sulfobetaine and cyclosiloxanes for modification. During acid injection, the cyclosiloxane structure undergoes hydrolysis and condensation, significantly increasing the viscosity of the acidizing fluid in the well. This creates a slow-flow splitting effect downhole, maintaining a sustained high-temperature acidic environment. The carboxymethyl cellulose backbone decomposes and breaks down, resulting in adaptive thickening that meets the thickening requirements of downhole acidizing. Simultaneously, it avoids the use of recalcitrant polymers, possessing profound research significance in environmentally friendly oil and gas extraction technologies.

Description

Technical Field

[0001] This invention belongs to the field of petroleum additives technology, specifically relating to a thickener for high-temperature acidification and its preparation method. Background Technology

[0002] In oil and gas well enhancement processes, acidizing is a key technology that involves injecting acid (such as hydrochloric acid or argonic acid) into the formation to dissolve rock minerals, expand pore channels, and improve permeability. However, conventional acids have low viscosity and a fast acid-rock reaction rate, leading to excessive consumption of acid in the near-wellbore zone, making it difficult to effectively stimulate deep formations. Thickeners, as acid additives, increase viscosity to slow down the acid-rock reaction rate, enabling deeper acid migration and uniform dissolution.

[0003] Currently, acrylamide-based multi-component polymers are commonly used as thickeners in deep well high-temperature acidizing. Their molecular chains contain heat-resistant groups (such as sulfonic acid groups and tert-butylacrylamide), which maintain good stability at high temperatures, thereby maintaining the viscosity of the acid solution. Moreover, the molecular chains of this type of thickener are highly designable, and thermal stability can be improved by introducing heat-resistant monomers, as well as providing basic thickening effects at low concentrations. However, this type of polymer thickener has unavoidable drawbacks: the linear polymer chains depolymerize at high temperatures, leading to a continuous decrease in viscosity, making it impossible to dynamically adapt to changes in well temperature and thus preventing dissolution, resulting in difficulty in achieving breakthroughs in production enhancement. Furthermore, this type of polymer is difficult to biodegrade naturally, and the waste returned to the well is difficult to process, which does not meet the requirements of environmental protection development. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background art, the purpose of this invention is to provide a thickener for high-temperature acidification and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A thickener for high-temperature acidification comprises, by weight percentage: 37-45 wt% modified CMC thickener, 5.2-7.0 wt% co-solvent, 1.2-1.6 wt% dispersant, and 2.4-3.1 wt% stabilizer, with the balance being water.

[0007] The modified CMC thickener is prepared by the following method:

[0008] Step A1: Carboxymethyl cellulose and anhydrous acetone are mixed and swollen under dry nitrogen protection. Triethylamine is added and mixed, and the temperature is controlled at 25-40℃ in a water bath. Acryloyl chloride is slowly added and stirred for 4.5-6.5h. Then the temperature is raised to reflux for 1.2-1.8h. After the reaction is completed, acetone is removed by rotary evaporation and the mixture is dried under vacuum to obtain the intermediate.

[0009] Furthermore, the ratio of carboxymethyl cellulose, acryloyl chloride, triethylamine, and anhydrous acetone is 50g:15-22mmol:10-15mL:350-400mL. The highly active acryloyl chloride is esterified with carboxymethyl cellulose, introducing an acrylate structure into the molecular side chain.

[0010] Preferably, the degree of substitution of carboxymethyl cellulose is 0.8-1.2, at which level it exhibits good swelling properties and reactivity.

[0011] Step A2: Mix the intermediate, methacryloyl ethyl sulfobetaine and ethanol solution, heat to 55-65℃, add azobisisobutyronitrile solution and stir for 2.2-3.5h. After the reaction is completed, remove ethanol and water under reduced pressure to obtain the modified matrix.

[0012] Furthermore, the ratio of intermediate, methacryloylethyl sulfobetaine, azobisisobutyronitrile, and ethanol solution is 50g: 25-30mmol: 0.1-0.13g: 280-330mL. Under the initiation of azobisisobutyronitrile, methacryloylethyl sulfobetaine undergoes addition with the acrylate structure grafted into the intermediate molecule, and the sulfobetaine structure is modified by introducing a side chain.

[0013] Step A3: Tetramethylcyclotetrasiloxane, allyl glycidyl ether and anhydrous toluene are premixed, heated to 70-80℃ under dry nitrogen protection, platinum catalyst is added and the reaction is stirred for 3-4 hours. After the reaction is completed, toluene is removed by rotary evaporation under reduced pressure to obtain the modifier.

[0014] Furthermore, the ratio of tetramethylcyclotetrasiloxane, allyl glycidyl ether, platinum catalyst, and anhydrous toluene is 0.1 mol: 0.15-0.18 mol: 0.15-0.2 g: 170-220 mL. Allyl glycidyl ether undergoes hydrosilylation with tetramethylcyclotetrasiloxane to introduce an epoxy structure.

[0015] Step A4: Mix the modified matrix, modifier and tetrahydrofuran, purge with dry nitrogen, stir in a water bath at 45-60℃ for 8-11 hours, then add 4-dimethylaminopyridine and reflux for 0.4-0.6 hours. After the reaction is complete, remove the tetrahydrofuran by rotary evaporation to obtain the modified CMC thickener.

[0016] Furthermore, the ratio of modified matrix, modifier, 4-dimethylaminopyridine and tetrahydrofuran is 50g:8.5-12g:0.2-0.3g:200-280mL. The betaine structure introduced into the side chain of the modified matrix molecule promotes the ring-opening reaction between the epoxy group of the modifier and the oxygen-containing group (carboxyl group and residual hydroxyl group) on the cellulose molecule, thereby introducing cyclosiloxane into the side chain of cellulose.

[0017] Preferably, the dispersant is sodium dodecyl sulfate, which interacts with the side-chain sulfobetaine structure of the modified CMC thickener to improve its dispersibility.

[0018] A method for preparing a thickener for high-temperature acidification specifically involves: grinding and dispersing a modified CMC thickener, a cosolvent, a dispersant, and water, followed by adding a stabilizer and mixing to obtain the thickener.

[0019] The beneficial effects of this invention are:

[0020] This invention is based on the bio-based raw material carboxymethyl cellulose (CMC). The CMC is modified to serve as the main thickening agent. The modification involves esterification of some hydroxyl groups in the CMC molecule with acryloyl chloride, introducing an acrylate structure. Then, methacryloyl ethyl sulfobetaine is added to the introduced acrylate, introducing sulfobetaine side chains to obtain a modified matrix. Allyl glycidyl ether undergoes hydrosilylation with tetramethylcyclotetrasiloxane, grafting epoxy groups onto the cyclosiloxane structure to create a modifier. Finally, the modifier ring-opens with the oxygen-containing groups in the modified matrix molecule, introducing cyclosiloxane structures into the cellulose side chains of the modified matrix, thus obtaining the modified CMC thickener. Compared with existing technologies, the modified CMC thickener of this invention contains sulfobetaine in its molecular side chains. With hydrophilic structures such as hydroxyl groups, it is compatible with aqueous acidizing systems. It provides a suitable initial viscosity through water absorption and swelling. As the acidizing fluid is injected and the well temperature rises, under acidic conditions, the cyclosiloxane structure of the side chain hydrolyzes and condenses, significantly increasing the viscosity of the acidizing fluid in the well. This forms a slow flow distribution downhole, which is conducive to the acid agent fully dissolving underground fractures and improving oil and gas extraction efficiency. As acidizing proceeds and the high-temperature acidic environment continues, the carboxymethyl cellulose backbone decomposes and then self-decomposes, which is conducive to flowback. The modified CMC thickener realizes an adaptive thickening mechanism, which is suitable for the thickening requirements of downhole acidizing. In addition, this invention avoids the use of recalcitrant polymers and uses bio-based carboxymethyl cellulose as the matrix, which has profound research significance in the environmentally friendly extraction technology of oil and gas. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The dynamic viscosity change curves of the acid solutions prepared with thickeners in Example 4 and the comparative example of the present invention as a function of temperature. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: Preparation of a thickener for high-temperature acidification. The specific implementation process is as follows:

[0025] (1) Preparation of modified CMC thickener

[0026] Step A1: Carboxymethyl cellulose (CMC) and anhydrous acetone were mixed under dry nitrogen protection and heated to 50°C for 2 hours to swell. After cooling, the temperature was controlled at 25°C in a water bath. Triethylamine was added and mixed, followed by the slow addition of acryloyl chloride and stirring for 6.5 hours. Then, the mixture was refluxed for 1.8 hours. The degree of substitution of carboxymethyl cellulose was approximately 0.85. The ratio of carboxymethyl cellulose, acryloyl chloride, triethylamine, and anhydrous acetone was 50 g: 15 mmol: 10 mL: 350 mL. After the reaction was completed, the acetone was removed by rotary evaporation and the mixture was dried under vacuum to obtain the intermediate.

[0027] Step A2: Mix the intermediate, methacryloylethyl sulfobetaine, and ethanol solution, heat to 55°C, add azobisisobutyronitrile solution, and stir for 3.5 h. The volume fraction of the ethanol solution is 65%, and the azobisisobutyronitrile solution is a saturated ethanol solution at room temperature. The ratio of the intermediate, methacryloylethyl sulfobetaine, azobisisobutyronitrile, and ethanol solution is 50 g: 25 mmol: 0.1 g: 280 mL. After the reaction is completed, remove ethanol and water under reduced pressure to obtain the modified matrix.

[0028] Step A3: Take tetramethylcyclotetrasiloxane, allyl glycidyl ether and anhydrous toluene as a premix, heat to 70°C under dry nitrogen protection, add platinum catalyst and stir for 4 hours. The platinum catalyst is a Castrol catalyst with an active platinum content of 5000 ppm. The ratio of tetramethylcyclotetrasiloxane, allyl glycidyl ether, platinum catalyst and anhydrous toluene is 0.1 mol: 0.15 mol: 0.15 g: 170 mL. After the reaction is completed, remove toluene by rotary evaporation under reduced pressure to obtain the modifier.

[0029] Step A4: Mix the modified matrix, modifier, and tetrahydrofuran, purge with dry nitrogen, and stir in a water bath at 45°C for 11 hours. Then add 4-dimethylaminopyridine and reflux for 0.6 hours. The ratio of modified matrix, modifier, 4-dimethylaminopyridine, and tetrahydrofuran is 50g:8.5g:0.2g:200mL. After the reaction is complete, remove the tetrahydrofuran by rotary evaporation to obtain the modified CMC thickener.

[0030] (2) Preparation of thickener

[0031] The raw materials are calculated by weight percentage as follows: 37 wt% modified CMC thickener, which is self-made in this embodiment; 5.2 wt% cosolvent, which is ethylene glycol monotert-butyl ether; 1.2 wt% dispersant, which is sodium dodecyl sulfate; 3.1 wt% stabilizer, which is polyethylene glycol 400; and the balance is water.

[0032] Modified CMC thickener, cosolvent, dispersant and water are mixed, fed into the mixture and ground to disperse. Then, a stabilizer is added and mixed to obtain a thickener.

[0033] Example 2: Preparation of a thickener for high-temperature acidification. The specific implementation process is as follows:

[0034] (1) Preparation of modified CMC thickener

[0035] Step A1: Carboxymethyl cellulose and anhydrous acetone were mixed under dry nitrogen protection and heated to 50°C for swelling for 1.5 h. After cooling, the temperature was controlled at 40°C in a water bath. Triethylamine was added and mixed, followed by the slow addition of acryloyl chloride and stirring for 4.5 h. Then, the mixture was refluxed for 1.2 h. The degree of substitution of carboxymethyl cellulose was approximately 1.2. The ratio of carboxymethyl cellulose, acryloyl chloride, triethylamine, and anhydrous acetone was 50 g: 22 mmol: 15 mL: 400 mL. After the reaction was completed, the acetone was removed by rotary evaporation and the mixture was dried under vacuum to obtain the intermediate.

[0036] Step A2: Mix the intermediate, methacryloylethyl sulfobetaine, and ethanol solution, heat to 65°C, add azobisisobutyronitrile solution, and stir for 2.2 h. The volume fraction of the ethanol solution is 65%, and the azobisisobutyronitrile solution is a saturated ethanol solution at room temperature. The ratio of the intermediate, methacryloylethyl sulfobetaine, azobisisobutyronitrile, and ethanol solution is 50 g: 30 mmol: 0.13 g: 330 mL. After the reaction is completed, remove ethanol and water under reduced pressure to obtain the modified matrix.

[0037] Step A3: Take tetramethylcyclotetrasiloxane, allyl glycidyl ether and anhydrous toluene as a premix, heat to 80°C under dry nitrogen protection, add platinum catalyst and stir for 3 hours. The platinum catalyst is a Castrol catalyst with an active platinum content of 5000 ppm. The ratio of tetramethylcyclotetrasiloxane, allyl glycidyl ether, platinum catalyst and anhydrous toluene is 0.1 mol: 0.18 mol: 0.2 g: 220 mL. After the reaction is completed, remove toluene by rotary evaporation under reduced pressure to obtain the modifier.

[0038] Step A4: Mix the modified matrix, modifier, and tetrahydrofuran, purge with dry nitrogen, and stir in a water bath at 60°C for 8 hours. Then add 4-dimethylaminopyridine and reflux for 0.4 hours. The ratio of the modified matrix, modifier, 4-dimethylaminopyridine, and tetrahydrofuran is 50g:12g:0.3g:280mL. After the reaction is complete, remove the tetrahydrofuran by rotary evaporation to obtain the modified CMC thickener.

[0039] (2) Preparation of thickener

[0040] The raw materials are calculated by weight percentage as follows: 45 wt% modified CMC thickener, which is self-made in this embodiment; 7.0 wt% cosolvent, which is ethylene glycol monotert-butyl ether; 1.6 wt% dispersant, which is sodium dodecyl sulfate; 2.4 wt% stabilizer, which is polyethylene glycol 400; and the balance is water.

[0041] Modified CMC thickener, cosolvent, dispersant and water are mixed, fed into the mixture and ground to disperse. Then, a stabilizer is added and mixed to obtain a thickener.

[0042] Example 3: Preparation of a thickener for high-temperature acidification. The specific implementation process is as follows:

[0043] (1) Preparation of modified CMC thickener

[0044] Step A1: Carboxymethyl cellulose and anhydrous acetone were mixed under dry nitrogen protection and heated to 50°C for swelling for 1.5 h. After cooling, the temperature was controlled at 30°C in a water bath. Triethylamine was added and mixed, followed by the slow addition of acryloyl chloride and stirring for 5.5 h. Then, the mixture was refluxed for 1.6 h. The degree of substitution of carboxymethyl cellulose was approximately 1.1. The ratio of carboxymethyl cellulose, acryloyl chloride, triethylamine, and anhydrous acetone was 50 g: 20 mmol: 12 mL: 380 mL. After the reaction was completed, the acetone was removed by rotary evaporation and the mixture was dried under vacuum to obtain the intermediate.

[0045] Step A2: Mix the intermediate, methacryloylethyl sulfobetaine, and ethanol solution, heat to 60°C, add azobisisobutyronitrile solution, and stir for 2.8 h. The volume fraction of the ethanol solution is 65%, and the azobisisobutyronitrile solution is a saturated ethanol solution at room temperature. The ratio of the intermediate, methacryloylethyl sulfobetaine, azobisisobutyronitrile, and ethanol solution is 50 g: 27 mmol: 0.11 g: 300 mL. After the reaction is completed, remove ethanol and water under reduced pressure to obtain the modified matrix.

[0046] Step A3: Take tetramethylcyclotetrasiloxane, allyl glycidyl ether and anhydrous toluene as a premix, heat to 75°C under dry nitrogen protection, add platinum catalyst and stir for 3.5 h. The platinum catalyst is a Castrol catalyst with an active platinum content of 5000 ppm. The ratio of tetramethylcyclotetrasiloxane, allyl glycidyl ether, platinum catalyst and anhydrous toluene is 0.1 mol: 0.17 mol: 0.15 g: 200 mL. After the reaction is completed, remove toluene by rotary evaporation under reduced pressure to obtain the modifier.

[0047] Step A4: Mix the modified matrix, modifier, and tetrahydrofuran, purge with dry nitrogen, and stir in a water bath at 55°C for 10 hours. Then add 4-dimethylaminopyridine and reflux for 0.6 hours. The ratio of the modified matrix, modifier, 4-dimethylaminopyridine, and tetrahydrofuran is 50g:10g:0.25g:250mL. After the reaction is complete, remove the tetrahydrofuran by rotary evaporation to obtain the modified CMC thickener.

[0048] (2) Preparation of thickener

[0049] The raw materials are calculated by weight percentage as follows: 40 wt% modified CMC thickener, which is self-made in this embodiment; 5.8 wt% cosolvent, which is ethylene glycol monotert-butyl ether; 1.3 wt% dispersant, which is sodium dodecyl sulfate; 2.7 wt% stabilizer, which is polyethylene glycol 400; and the balance is water.

[0050] Modified CMC thickener, cosolvent, dispersant and water are mixed, fed into the mixture and ground to disperse. Then, a stabilizer is added and mixed to obtain a thickener.

[0051] Example 4: Preparation of a thickener for high-temperature acidification. The specific implementation process is as follows:

[0052] (1) Preparation of modified CMC thickener

[0053] Step A1: Carboxymethyl cellulose and anhydrous acetone were mixed under dry nitrogen protection and heated to 50°C for 2 hours to swell. After cooling, the temperature was controlled at 35°C in a water bath. Triethylamine was added and mixed, followed by the slow addition of acryloyl chloride and stirring for 5.2 hours. Then, the mixture was refluxed for 1.8 hours. The degree of substitution of carboxymethyl cellulose was approximately 1.1. The ratio of carboxymethyl cellulose, acryloyl chloride, triethylamine, and anhydrous acetone was 50 g: 20 mmol: 13 mL: 350 mL. After the reaction was completed, the acetone was removed by rotary evaporation and the mixture was dried under vacuum to obtain the intermediate.

[0054] Step A2: Mix the intermediate, methacryloylethyl sulfobetaine, and ethanol solution, heat to 65°C, add azobisisobutyronitrile solution, and stir for 3.2 h. The volume fraction of the ethanol solution is 65%, and the azobisisobutyronitrile solution is a saturated ethanol solution at room temperature. The ratio of the intermediate, methacryloylethyl sulfobetaine, azobisisobutyronitrile, and ethanol solution is 50 g: 25 mmol: 0.12 g: 300 mL. After the reaction is completed, remove ethanol and water under reduced pressure to obtain the modified matrix.

[0055] Step A3: Take tetramethylcyclotetrasiloxane, allyl glycidyl ether and anhydrous toluene as a premix, heat to 80°C under dry nitrogen protection, add platinum catalyst and stir for 3.3 h. The platinum catalyst is a Castrol catalyst with an active platinum content of 5000 ppm. The ratio of tetramethylcyclotetrasiloxane, allyl glycidyl ether, platinum catalyst and anhydrous toluene is 0.1 mol: 0.18 mol: 0.2 g: 190 mL. After the reaction is completed, remove toluene by rotary evaporation under reduced pressure to obtain the modifier.

[0056] Step A4: Mix the modified matrix, modifier, and tetrahydrofuran, purge with dry nitrogen, and stir in a water bath at 50°C for 11 hours. Then add 4-dimethylaminopyridine and reflux for 0.5 hours. The ratio of the modified matrix, modifier, 4-dimethylaminopyridine, and tetrahydrofuran is 50g:11g:0.3g:270mL. After the reaction is complete, remove the tetrahydrofuran by rotary evaporation to obtain the modified CMC thickener.

[0057] (2) Preparation of thickener

[0058] The raw materials are calculated by weight percentage as follows: 42 wt% modified CMC thickener, which is self-made in this embodiment; 6.5 wt% cosolvent, which is ethylene glycol monotert-butyl ether; 1.3 wt% dispersant, which is sodium dodecyl sulfate; 2.5 wt% stabilizer, which is polyethylene glycol 400; and the balance is water.

[0059] Modified CMC thickener, cosolvent, dispersant and water are mixed, fed into the mixture and ground to disperse. Then, a stabilizer is added and mixed to obtain a thickener.

[0060] For comparison, commercially available KHF071 type polyacrylamide high-temperature resistant thickener was selected.

[0061] Acid preparation: Use 15% hydrochloric acid as the acid agent, add 0.12wt% of YTY-04 quinoline quaternary ammonium salt as the corrosion inhibitor, 0.08wt% of ascorbic acid as the iron ion stabilizer, and 1.5wt% of the above thickener, mix evenly to obtain the acid solution.

[0062] Dynamic viscosity test: Using the acid solutions prepared with the thickeners of Example 4 and the comparative example as the test objects, the acid solutions were subjected to a 170s viscosity test. -1 Shearing was performed, the temperature was increased from 30℃ to 180℃ and held at that temperature, the viscosity of the acid was measured, and a dynamic viscosity change curve was plotted, as detailed below. Figure 1 As shown;

[0063] In simulated acid injection dynamic viscosity tests, by Figure 1 It can be seen that the initial viscosity of the thickened acid solution prepared in Example 4 is slightly lower than that of the comparative example. As the temperature increases, the viscosity of Example 4 first decreases and then increases, with a peak viscosity of about 125 mPa·s. The viscosity of the comparative example shows a visible phased decrease as the temperature increases.

[0064] Core dissolution test: Artificial marble cores (porosity 18%) with dimensions of Φ25×50mm were taken and injected with the prepared acid solution. The temperature was controlled at 150℃, and the compressed air was pressurized to 2.0MPa. The dissolution cycles were 120min and 240h, respectively. The dissolution rate and dissolution depth of the cores were measured. The specific test results are shown in Table 1.

[0065]

[0066] As shown in Table 1, the acid solution prepared with the thickener in the example has good dissolving properties for the rock core, especially during long-term dissolution, the dissolution efficiency and depth are significantly better than those of the comparative example.

[0067] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0068] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A thickener for high-temperature acidification, characterized in that, The weight percentage components are: 37-45 wt% modified CMC thickener, 5.2-7.0 wt% cosolvent, 1.2-1.6 wt% dispersant, and 2.4-3.1 wt% stabilizer, with the balance being water; The modified CMC thickener is prepared by the following method: Step A1: Carboxymethyl cellulose and anhydrous acetone are mixed and swollen under dry nitrogen protection. Triethylamine is added and mixed, and the temperature is controlled at 25-40℃ in a water bath. Acryloyl chloride is slowly added and stirred for 4.5-6.5h. Then the temperature is raised and refluxed for 1.2-1.8h to obtain the intermediate. Step A2: Mix the intermediate, methacryloyl ethyl sulfobetaine and ethanol solution, heat to 55-65℃, add azobisisobutyronitrile solution and stir for 2.2-3.5h to obtain the modified matrix; Step A3: Tetramethylcyclotetrasiloxane, allyl glycidyl ether and anhydrous toluene are premixed, heated to 70-80℃ under dry nitrogen protection, platinum catalyst is added and the reaction is stirred for 3-4 hours to obtain the modifier. Step A4: Mix the modified matrix, modifier and tetrahydrofuran, purge with dry nitrogen, stir in a water bath at 45-60℃ for 8-11 hours, then add 4-dimethylaminopyridine and reflux for 0.4-0.6 hours to obtain the modified CMC thickener.

2. The thickener for high-temperature acidification according to claim 1, characterized in that, The ratio of carboxymethyl cellulose, acryloyl chloride, triethylamine and anhydrous acetone is 50g: 15-22mmol: 10-15mL: 350-400mL.

3. The thickener for high-temperature acidification according to claim 2, characterized in that, The degree of substitution of carboxymethyl cellulose is 0.8-1.

2.

4. The thickener for high-temperature acidification according to claim 2, characterized in that, The ratio of intermediate, methacryloylethyl sulfobetaine, azobisisobutyronitrile and ethanol solution is 50g: 25-30mmol: 0.1-0.13g: 280-330mL.

5. A thickener for high-temperature acidification according to claim 4, characterized in that, The ratio of tetramethylcyclotetrasiloxane, allyl glycidyl ether, platinum catalyst, and anhydrous toluene is 0.1 mol: 0.15-0.18 mol: 0.15-0.2 g: 170-220 mL.

6. The thickener for high-temperature acidification according to claim 5, characterized in that, The ratio of modified matrix, modifier, 4-dimethylaminopyridine and tetrahydrofuran is 50g: 8.5-12g: 0.2-0.3g: 200-280mL.

7. The thickener for high-temperature acidification according to claim 1, characterized in that, The dispersant is sodium dodecyl sulfate.

8. A method for preparing a thickener for high-temperature acidification according to any one of claims 1-7, characterized in that, Specifically, the modified CMC thickener, cosolvent, dispersant and water are milled and dispersed, and then a stabilizer is added and mixed to obtain the thickener.

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