A high-temperature resistant clay stabilizer and its preparation method

Abstract

The present invention belongs to the field of oil production technology, and in particular to a high temperature resistant clay stabilizer and a preparation method thereof. The preparation method is as follows: N, N-bis (2-hydroxyethyl) methacrylamide, aminosulfonic acid powder, and urea are added to a four-necked flask, heated while stirring, and the reaction is kept warm; distilled water, (3-acrylamidopropyl) trimethylammonium chloride, 2-methacryloyloxyethyl phosphorylcholine, and buffer salt are added to the above-mentioned four-necked flask in sequence and stirred evenly; an initiator is added dropwise to the above-mentioned four-necked flask, the system automatically heats up, the reaction is kept warm, potassium dimethyldithiocarbamate solution is added to terminate the reaction, the pH value is adjusted, and the temperature is lowered to below 40 ° C to obtain a viscous liquid; the viscous liquid is dried and granulated to obtain a product clay stabilizer. The clay stabilizer of the invention has the advantages of a wide source of raw materials, a simple preparation process, a high anti-swelling rate, water resistance, and high temperature resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and particularly relates to a high-temperature resistant clay stabilizer and a preparation method thereof. Background Art

[0002] Most low-permeability oil and gas formations contain clay minerals. Some are deposited by sedimentation of crushed clay, others are formed by the long-term effects of heat and pressure on ores, and still others are formed by the deposition of authigenic clay when water flows through bedrock. Clay minerals in reservoirs hydrate and expand when they come into contact with incompatible external fluids. During this expansion, the clay absorbs water into its crystal structure, increasing its volume and thus clogging the formation pores. During migration, the clay material is dispersed by external fluids or carried by produced fluids, forming bridges or choke points at the pore throats of capillaries. This leads to a decrease in reservoir permeability and dispersed migration, clogging reservoir channels and damaging the oil and gas formations.

[0003] Based on the water-sensitive damage mechanism of clay minerals, if some additives are added to the injection water to make the injection water a cationic solution, the cations will interact with the negative ions on the surface of the clay crystal layer, and the two will combine to form an anti-swelling system, thereby forming a hydrophobic protective film on the clay surface, isolating the attraction of the dipole of the oxygen bond or amino oxygen bond of the clay crystal layer to water molecules, thus preventing the hydration and swelling of the clay. At the same time, inter-ionic repulsion is generated in the hydrated clay system, which plays a role in polymerization and condensation, causing the clay particles to coalesce into clay particles, ultimately preventing the dispersion and migration of the clay. This additive is called a clay stabilizer.

[0004] Generally speaking, clay stabilizers used for water injection are not only required to have high anti-swelling effect and low effective use concentration, but also to carry a certain amount of positive charge, have good compatibility with formation water, have a stable and long-lasting effect on inhibiting the expansion of clay in the formation, and be resistant to erosion by various fluids.

[0005] Clay stabilizers are used more and more widely and there are more and more types. According to their chemical composition, they can be divided into inorganic salts, inorganic polymers, cationic surfactants, nonionic and cationic organic polymers.

[0006] CN106147739A discloses a fracturing clay stabilizer and a preparation method thereof. The fracturing clay stabilizer is prepared from the following raw materials in parts by weight: 35-50 parts of choline chloride, 3-8 parts of calcium chloride, 40-50 parts of water, 5-10 parts of methanol, and 1-5 parts of an alcohol ether solvent. The preparation method of the fracturing clay stabilizer comprises the following specific steps: (1) weighing choline chloride and methanol according to the above formula and mixing them uniformly to obtain component a; (2) adding the formulated amount of water, calcium chloride, and an alcohol ether solvent to component a obtained in step (1) in sequence, stirring until the solid is completely dissolved, and then discharging the material. The fracturing clay stabilizer prepared by this method has excellent anti-swelling properties and good compatibility. However, the clay stabilizer of the invention contains a large amount of methanol and alcohol ether, which are water-soluble substances and are easily miscible with water, indicating that the clay stabilizer has poor water washability. In addition, the anti-swelling rate of the clay stabilizer of the invention is only about 50%, which cannot meet production needs.

[0007] CN104098738A discloses a method for preparing a low-molecular-weight polymer clay stabilizer. The clay stabilizer is prepared by polymerization in an aqueous solution using carbon-containing ammonium salt and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as raw materials in the presence of an initiator. The polymer number-average molecular weight is less than 50,000. Sulfonic acid groups are introduced into the polymer stabilizer to increase the water solubility and temperature resistance of the polymer. It can simultaneously form multi-point adsorption with multiple clay particles in water. After adsorption, a layer of adsorption protective film is formed on the surface of the clay particles to prevent the expansion and migration of the clay particles; the stabilizer has high-temperature resistance, and the temperature resistance reaches above 120°C. However, the stabilizer is easily adsorbed to the rock surface, reducing the permeability of the formation, or directly blocking the formation. At the same time, the temperature and salt resistance of the clay stabilizer are poor, which limits its scope of application. Summary of the Invention

[0008] The present invention addresses the deficiencies of the prior art and provides a high-temperature resistant clay stabilizer and a preparation method thereof. The clay stabilizer of the invention has the advantages of a wide range of raw material sources, a simple preparation process, a high anti-swelling rate, water-resistant and high-temperature resistance.

[0009] One of the purposes of the present invention is to disclose a high temperature resistant clay stabilizer, the molecular structure of the clay stabilizer is as follows:

[0010]

[0011] Where, x = 2000-20000;

[0012] y = 200-10000;

[0013] z=200-6000.

[0014] Preferably, the viscosity average molecular weight of the clay stabilizer is 500,000-5,000,000.

[0015] Another object of the present invention is to disclose a method for preparing a high temperature resistant clay stabilizer, wherein the specific steps of the preparation method are as follows:

[0016] (1) Add N,N-bis(2-hydroxyethyl)methacrylamide, aminosulfonic acid powder, and urea to a four-necked flask, heat with stirring, and keep at 60-65°C for 60-120 minutes, adjusting the pH to 7-8;

[0017] (2) Add distilled water, (3-acrylamidopropyl)trimethylammonium chloride, 2-methacryloyloxyethyl phosphorylcholine, and buffer salt to the above four-necked flask in sequence and stir evenly;

[0018] (3) Add the initiator dropwise to the four-necked flask, and the system will automatically heat up. After the temperature stops rising, continue to keep the temperature and react for 30-60 minutes. Add 10 wt% potassium dimethyldithiocarbamate solution to terminate the reaction, adjust the pH to 7-8, and cool to below 40°C to obtain a viscous liquid.

[0019] (4) Drying and granulating the viscous liquid to obtain a clay stabilizer product.

[0020] In the present invention, preferably, based on 1 mole of N,N-bis(2-hydroxyethyl)methacrylamide, the amounts of aminosulfonic acid, (3-acrylamidopropyl)trimethylammonium chloride, and 2-methacryloyloxyethylphosphocholine are 2-3 mole parts, 0.1-0.5 mole parts, and 0.1-0.3 mole parts, respectively.

[0021] Preferably, the weight ratio of urea to N,N-bis(2-hydroxyethyl)methacrylamide in step (1) is 0.01-0.05:1.

[0022] In the present invention, preferably, the weight ratio of distilled water to N,N-bis(2-hydroxyethyl)methacrylamide in step (2) is 8-10:1.

[0023] Preferably, the buffer salt in step (2) is one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, dipotassium hydrogen phosphate, and diammonium hydrogen phosphate, and the weight ratio of the buffer salt to N,N-bis(2-hydroxyethyl)methacrylamide is 0.05-0.2:1.

[0024] In the present invention, preferably, the initiator in step (3) is one of a mixed aqueous solution of 10 wt% potassium persulfate + 5 wt% potassium bisulfite and a mixed aqueous solution of 10 wt% ammonium persulfate + 5 wt% potassium bisulfite, and the weight ratio of the initiator to N,N-bis(2-hydroxyethyl)methacrylamide is 0.1-0.5:1.

[0025] Preferably, the weight ratio of the 10 wt% potassium dimethyldithiocarbamate solution to N,N-bis(2-hydroxyethyl)methacrylamide in step (3) is 0.02-0.1:1.

[0026] The reaction equation for the synthesis of the high temperature resistant clay stabilizer of the present invention is as follows:

[0027]

[0028]

[0029] The high temperature resistant clay stabilizer of the present invention is a ternary high molecular polymer, wherein N, N-bis (2-hydroxyethyl) methacrylamide reacts with aminosulfuric acid under the action of urea as a catalyst to generate a functional monomer. The present invention has two quaternary ammonium salts and two ammonium ions in its molecule, which can mutually adsorb and neutralize with clay with a negative surface charge, reduce repulsion between crystal layers, and play an anti-swelling role. Polar groups such as amide groups and phosphate groups in the molecule can form hydrogen bonds with oxygen layers or hydroxyl layers on the clay crystal surface to achieve a strong bond. During the synthesis process of the present invention, a large amount of potassium ions and ammonium ions are introduced through neutralization, initiation, and buffering. The potassium ion has a diameter of 266 μm and the ammonium ion has a radius of 286 μm, which is very close to the structural pores of the clay of 280 μm. They can easily enter the pore space and are not easily released, resulting in a strong bond. Strong van der Waals attraction exists between the macromolecular chain of the present invention and the clay, so that the macromolecule can form a strong monomolecular adsorption layer on the clay crystal surface, which is not easily desorbed to form a diffuse double layer. The macromolecular chain of the present invention is relatively long and can be adsorbed to multiple crystal layers at the same time. The outer side of the macromolecular chain of the present invention is a hydrophobic polymeric alkyl chain, which has an oleophilic structure and can prevent water molecules from contacting and wetting the clay, thereby inhibiting expansion.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] (1) The high temperature resistant clay stabilizer of the present invention has the advantage of a high anti-swelling rate, which is over 98%;

[0032] (2) The high temperature resistant clay stabilizer of the present invention has the advantage of being resistant to water washing, and the anti-swelling rate after water washing reaches more than 94%;

[0033] (3) The high temperature resistant clay stabilizer of the present invention has the advantage of high temperature resistance, and the maximum temperature resistance reaches above 340°C. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to specific embodiments:

[0035] Example 1

[0036] (1) Add 0.1 mol N,N-bis(2-hydroxyethyl)methacrylamide, 0.2 mol aminosulfonic acid powder, and 0.173 g urea to a four-necked flask, heat with stirring, and keep at 60°C for 120 min. Adjust the pH to 7-8 with potassium hydroxide solution.

[0037] (2) 138.4 g of distilled water, 0.01 mol of (3-acrylamidopropyl)trimethylammonium chloride, 0.03 mol of 2-methacryloyloxyethyl phosphorylcholine, and 0.865 g of potassium dihydrogen phosphate were added to the above four-necked flask in sequence and stirred evenly;

[0038] (3) Add an initiator dropwise to the four-necked flask. The initiator is 1.73 g of a 10 wt% potassium persulfate + 5 wt% potassium bisulfite aqueous solution. The system automatically heats up. After the temperature stops rising, the reaction is continued for 60 min. 0.346 g of a 10 wt% potassium dimethyldithiocarbamate solution is added to terminate the reaction. The pH is adjusted to 7-8 with potassium hydroxide solution, and the temperature is lowered to below 40° C. to obtain a viscous liquid.

[0039] (4) Drying and granulating the viscous liquid to obtain a clay stabilizer product.

[0040] Example 2

[0041] (1) Add 0.1 mol N,N-bis(2-hydroxyethyl)methacrylamide, 0.22 mol aminosulfonic acid powder, and 0.315 g urea to a four-necked flask, heat with stirring, and keep at 65°C for 60 min. Adjust the pH to 7-8 with potassium hydroxide solution.

[0042] (2) 144 g of distilled water, 0.015 mol of (3-acrylamidopropyl)trimethylammonium chloride, 0.025 mol of 2-methacryloyloxyethyl phosphorylcholine, and 1.332 g of dipotassium hydrogen phosphate were added to the above four-necked flask in sequence and stirred evenly;

[0043] (3) Add an initiator dropwise to the four-necked flask. The initiator is 2.44 g of a 10 wt% potassium persulfate + 5 wt% potassium bisulfite aqueous solution. The system automatically heats up. After the temperature stops rising, the reaction is continued for 30 min. 0.763 g of a 10 wt% potassium dimethyldithiocarbamate solution is added to terminate the reaction. The pH is adjusted to 7-8 with potassium hydroxide solution, and the temperature is lowered to below 40° C. to obtain a viscous liquid.

[0044] (4) Drying and granulating the viscous liquid to obtain a clay stabilizer product.

[0045] Example 3

[0046] (1) Add 0.1 mol N,N-bis(2-hydroxyethyl)methacrylamide, 0.23 mol aminosulfonic acid powder, and 0.474 g urea to a four-necked flask, heat with stirring, and keep at 63°C for 90 min. Adjust the pH to 7-8 with potassium hydroxide solution.

[0047] (2) 152 g of distilled water, 0.02 mol of (3-acrylamidopropyl)trimethylammonium chloride, 0.02 mol of 2-methacryloyloxyethyl phosphorylcholine, and 1.688 g of ammonium dihydrogen phosphate were added to the above four-necked flask in sequence and stirred evenly;

[0048] (3) Add an initiator dropwise to the four-necked flask. The initiator is 3.98 g of a 10 wt% potassium persulfate + 5 wt% potassium bisulfite aqueous solution. The system automatically heats up. After the temperature stops rising, the reaction is continued for 40 min. 1.73 g of a 10 wt% potassium dimethyldithiocarbamate solution is added to terminate the reaction. The pH is adjusted to 7-8 with potassium hydroxide solution, and the temperature is lowered to below 40° C. to obtain a viscous liquid.

[0049] (4) Drying and granulating the viscous liquid to obtain a clay stabilizer product.

[0050] Example 4

[0051] (1) Add 0.1 mol N,N-bis(2-hydroxyethyl)methacrylamide, 0.25 mol aminosulfonic acid powder, and 0.655 g urea to a four-necked flask and heat with stirring at 62°C for 100 min. Adjust the pH to 7-8 with potassium hydroxide solution.

[0052] (2) 166 g of distilled water, 0.025 mol of (3-acrylamidopropyl)trimethylammonium chloride, 0.015 mol of 2-methacryloyloxyethyl phosphorylcholine, and 2.147 g of diammonium hydrogen phosphate were added to the above four-necked flask in sequence and stirred evenly;

[0053] (3) Add 5.15 g of a 10 wt% potassium persulfate + 5 wt% potassium bisulfite aqueous solution of an initiator dropwise to the four-necked flask. The system automatically heats up. After the temperature stops rising, the reaction is continued for 50 min. 1.52 g of a 10 wt% potassium dimethyldithiocarbamate solution is added to terminate the reaction. The pH is adjusted to 7-8 with potassium hydroxide solution, and the temperature is lowered to below 40° C. to obtain a viscous liquid.

[0054] (4) Drying and granulating the viscous liquid to obtain a clay stabilizer product.

[0055] Example 5

[0056] (1) Add 0.1 mol N,N-bis(2-hydroxyethyl)methacrylamide, 0.27 mol aminosulfonic acid powder, and 0.74 g urea to a four-necked flask, heat at 63°C with stirring, and react for 120 min. Adjust the pH to 7-8 with potassium hydroxide solution.

[0057] (2) 173 g of distilled water, 0.03 mol of (3-acrylamidopropyl)trimethylammonium chloride, 0.015 mol of 2-methacryloyloxyethyl phosphorylcholine, and 3.46 g of potassium dihydrogen phosphate were added to the above four-necked flask in sequence and stirred evenly;

[0058] (3) Add 7.68 g of a 10 wt% ammonium persulfate + 5 wt% potassium bisulfite aqueous solution of an initiator dropwise to the four-necked flask. The system automatically heats up. After the temperature stops rising, the reaction is continued for 30 min. 1.44 g of a 10 wt% potassium dimethyldithiocarbamate solution is added to terminate the reaction. The pH is adjusted to 7-8 with potassium hydroxide solution, and the temperature is lowered to below 40° C. to obtain a viscous liquid.

[0059] (4) Drying and granulating the viscous liquid to obtain a clay stabilizer product.

[0060] Example 6

[0061] (1) Add 0.1 mol N,N-bis(2-hydroxyethyl)methacrylamide, 0.28 mol aminosulfonic acid powder, and 0.865 g urea to a four-necked flask and heat with stirring at 64°C for 100 min. Adjust the pH to 7-8 with potassium hydroxide solution.

[0062] (2) 158 g of distilled water, 0.04 mol of (3-acrylamidopropyl)trimethylammonium chloride, 0.01 mol of 2-methacryloyloxyethyl phosphorylcholine, and 2.645 g of potassium dihydrogen phosphate were added to the above four-necked flask in sequence and stirred evenly;

[0063] (3) Add 8.65 g of a 10 wt% ammonium persulfate + 5 wt% potassium bisulfite aqueous solution of an initiator dropwise to the four-necked flask. The system automatically heats up. After the temperature stops rising, the reaction is continued for 45 min. 1.286 g of a 10 wt% potassium dimethyldithiocarbamate solution is added to terminate the reaction. The pH is adjusted to 7-8 with potassium hydroxide solution, and the temperature is lowered to below 40° C. to obtain a viscous liquid.

[0064] (4) Drying and granulating the viscous liquid to obtain a clay stabilizer product.

[0065] Example 7

[0066] (1) Add 0.1 mol N,N-bis(2-hydroxyethyl)methacrylamide, 0.3 mol aminosulfonic acid powder, and 0.82 g urea to a four-necked flask, heat with stirring, and keep at 60°C for 80 min. Adjust the pH to 7-8 with potassium hydroxide solution.

[0067] (2) 171 g of distilled water, 0.05 mol of (3-acrylamidopropyl)trimethylammonium chloride, 0.01 mol of 2-methacryloyloxyethyl phosphorylcholine, and 2.78 g of potassium dihydrogen phosphate were added to the above four-necked flask in sequence and stirred evenly;

[0068] (3) An initiator (6.64 g of a 10 wt% ammonium persulfate + 5 wt% potassium bisulfite aqueous solution) was added dropwise to the four-necked flask. The system heated automatically. After the temperature stopped rising, the reaction was continued for 35 min. 1.11 g of a 10 wt% potassium dimethyldithiocarbamate solution was added to terminate the reaction. The pH was adjusted to 7-8 with potassium hydroxide solution, and the temperature was lowered to below 40° C. to obtain a viscous liquid.

[0069] (4) Drying and granulating the viscous liquid to obtain a clay stabilizer product.

[0070] Example 8 Evaluation of the Anti-Swelling Capacity of Clay Stabilizer

[0071] The evaluation method refers to SY / T5971-2016 "Performance Evaluation Method of Clay Stabilizers for Oil and Gas Field Fracturing, Acidizing and Water Injection" and the centrifuge method is used to test the anti-swelling rate.

[0072] 0.5 g of the clay stabilizer of the present invention (Example 1-7) was added to 100 g of distilled water and shaken to obtain a clay stabilizer solution.

[0073] Weigh 0.50 g of sodium bentonite, put it into a 10 mL centrifuge tube, add 10 mL of clay stabilizer solution, shake well, place at room temperature for 2 hours, put it into a centrifuge, centrifuge at a speed of 1500 r / min for 15 minutes, and read the volume V1 of the sodium bentonite after expansion.

[0074] The volume of sodium bentonite after expansion is V2 after replacing the clay stabilizer solution with distilled water.

[0075] The volume of sodium bentonite after expansion is V0 when kerosene is used to replace the clay stabilizer solution.

[0076] Calculation method of anti-swelling rate:

[0077] B=(V2-V1) / (V2-V0)×100%

[0078] A comparative experiment was conducted using Clay Stabilizer No. 3 from Tianjin Binpu Technology Development Co., Ltd.

[0079] The test results of the anti-swelling rate of clay stabilizer are shown in Table 1.

[0080] As can be seen from Table 1, the anti-swelling rate of the clay stabilizer of the present invention (Examples 1-7) reached 98% or above when the concentration was 0.5wt%, with the highest reaching 99% (Example 7). The anti-swelling rate of the clay stabilizer No. 3 of Tianjin Binpu Technology Development Co., Ltd. in the comparative example was 83.6%, which was significantly lower than that of the present invention.

[0081] Example 9 Evaluation of Heat Resistance of Clay Stabilizer

[0082] The clay stabilizer solution was sealed and placed in a thermostat set at different temperatures and taken out after 24 hours. The anti-swelling rate was tested according to the method of Example 8.

[0083] As the temperature rises, the anti-swelling rate gradually decreases. When the anti-swelling rate drops to 80%, the corresponding temperature is the temperature resistance of the clay stabilizer.

[0084] A comparative experiment was conducted using Clay Stabilizer No. 3 from Tianjin Binpu Technology Development Co., Ltd.

[0085] The test results of the temperature resistance of the clay stabilizer are shown in Table 1.

[0086] As can be seen from Table 1, the maximum temperature resistance of the clay stabilizer of the present invention (Examples 1-7) all reached 340°C and above, with the highest reaching 365°C (Examples 1 and 2), while the maximum temperature resistance of the clay stabilizer No. 3 of Tianjin Binpu Technology Development Co., Ltd. in the comparative example was 205°C, which is significantly lower than that of the present invention.

[0087] Example 10 Evaluation of the water washability of clay stabilizers

[0088] Discard the supernatant in the centrifuge tube after centrifugation in Example 8, add 10 mL of distilled water, shake thoroughly, let stand for 2 hours, place in a centrifuge, and centrifuge at 1500 r / min for 15 minutes. Repeat this process twice, and read the volume of the sodium bentonite after expansion. Calculate the volume in the same manner as in Example 8.

[0089] A comparative experiment was conducted using Clay Stabilizer No. 3 from Tianjin Binpu Technology Development Co., Ltd.

[0090] The test results of the water washability of the clay stabilizer are shown in Table 1.

[0091] Table 1 Test results of anti-swelling rate, temperature resistance and water washing resistance

[0092]

[0093]

[0094] As can be seen from Table 1, the anti-swelling rate of the clay stabilizer of the present invention (Examples 1-7) after washing with water all reached 94% or above, with the highest reaching 95.3% (Example 7). However, the anti-swelling rate of the clay stabilizer No. 3 of Tianjin Binpu Technology Development Co., Ltd. after washing with water was 80%, which was significantly lower than that of the present invention.

[0095] In summary, the high temperature resistant clay stabilizer of the present invention has the advantages of high anti-swelling rate, water washability and high temperature resistance.

[0096] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a high temperature resistant clay stabilizer, characterized in that: The specific steps of the preparation method are as follows: (1) Add N,N-bis(2-hydroxyethyl)methacrylamide, aminosulfonic acid powder, and urea to a four-necked flask, heat with stirring, and keep at 60-65°C for 60-120 minutes, then adjust the pH to 7-8. (2) Add distilled water, (3-acrylamidopropyl)trimethylammonium chloride, 2-methacryloyloxyethyl phosphorylcholine, and buffer salt to the above four-necked flask in sequence and stir evenly; (3) Add the initiator dropwise to the above four-necked flask. The system will automatically heat up. After the temperature stops rising, continue to keep the temperature and react for 30-60 minutes. Add 10 wt% potassium dimethyldithiocarbamate solution to terminate the reaction. Adjust the pH to 7-8 and cool to below 40°C to obtain a viscous liquid. (4) drying and granulating the viscous liquid to obtain a clay stabilizer product; Based on 1 mole of N,N-bis(2-hydroxyethyl)methacrylamide, the amounts of aminosulfonic acid, (3-acrylamidopropyl)trimethylammonium chloride, and 2-methacryloyloxyethylphosphocholine are 2-3 moles, 0.1-0.5 moles, and 0.1-0.3 moles, respectively.

2. The method for preparing a high temperature resistant clay stabilizer according to claim 1, wherein: The weight ratio of urea to N,N-bis(2-hydroxyethyl)methacrylamide in step (1) is 0.01-0.05:

1.

3. The method for preparing a high temperature resistant clay stabilizer according to claim 1, wherein: The weight ratio of distilled water to N,N-bis(2-hydroxyethyl)methacrylamide in step (2) is 8-10:

1.

4. The method for preparing a high temperature resistant clay stabilizer according to claim 1, wherein: The buffer salt in step (2) is one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, dipotassium hydrogen phosphate, and diammonium hydrogen phosphate, and the weight ratio of the buffer salt to N,N-bis(2-hydroxyethyl)methacrylamide is 0.05-0.2:

1.

5. The method for preparing a high temperature resistant clay stabilizer according to claim 1, wherein: The initiator in step (3) is one of a mixed aqueous solution of 10 wt% potassium persulfate + 5 wt% potassium bisulfite and a mixed aqueous solution of 10 wt% ammonium persulfate + 5 wt% potassium bisulfite, and the weight ratio of the initiator to N, N-bis (2-hydroxyethyl) methacrylamide is 0.1-0.5:

1.

6. The method for preparing a high temperature resistant clay stabilizer according to claim 1, wherein: The weight ratio of the 10 wt % potassium dimethyldithiocarbamate solution to N,N-bis(2-hydroxyethyl)methacrylamide in step (3) is 0.02-0.1:

1.

7. A high temperature resistant clay stabilizer, characterized in that: The molecular structural formula of the clay stabilizer is as follows: Where x=2000-20000; y=200-10000； z=200-6000。 8. A high temperature resistant clay stabilizer as claimed in claim 7, characterized in that: The viscosity average molecular weight of the clay stabilizer is 500,000-5,000,000.

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