A 240-degree-celsius high-temperature resistant saturated salt clay protective agent for water-based drilling fluid and a preparation method and application thereof

Abstract

The application provides a 240 DEG C high-temperature and saturated salt-resistant clay protector for a water-based drilling fluid and a preparation method and application thereof. The preparation method of the clay protector comprises the following steps: DL-homocysteine thio lactone hydrochloride and sodium bicarbonate are added into a mixed solvent of water and ethyl acetate at 0-5 DEG C, allyl sulfonic acid sodium and acryloyl chloride are continuously added at 0-5 DEG C after uniform stirring, and then reaction is carried out after uniform stirring to obtain an intermediate product A; the intermediate product A is dispersed in anhydrous ethanol, short-chain alkyl amine, isophorone diisocyanate and polyvinyl pyrrolidone are added, uniform stirring is carried out, and then reaction is carried out to obtain the clay protector. The clay protector can effectively protect the clay in the water-based drilling fluid under the condition of 240 DEG C high temperature and saturated salt, and the performance of the drilling fluid in a high-temperature and high-salt environment is improved.

Description

Technical Field

[0001] This invention relates to a water-based drilling fluid protective agent resistant to high temperature of 240℃ and saturated salt clay, its preparation method and application, belonging to the field of oilfield drilling technology. Background Technology

[0002] Deep and ultra-deep oil and gas resources are abundant, but deep and ultra-deep wells are typically characterized by high temperatures, high salinity, and complex geological conditions. This makes the clay in the drilling fluid easily damaged, severely deteriorating the rheological and filtration properties of the drilling fluid, leading to frequent accidents. Researchers have attempted to modify clay using organic modifiers (such as quaternary ammonium ions and ionic liquids), or by using oxygen scavengers or peroxy free radical scavengers (such as sodium sulfite), or by using small molecule polymers or surfactants (such as β-cyclodextrin) to improve the clay's resistance to high temperatures and salt. However, the results are still unsatisfactory. Chinese patent document CN109054798A discloses a high-temperature clay stabilizer for oilfields, prepared from γ-(2,3-epoxypropoxy)propyltrimethoxysilane and trimethylamine hydrochloride, which can effectively stabilize clay at 150℃. Chinese patent document CN105462570A discloses a temperature-resistant clay stabilizer prepared from maleic anhydride and diamine compounds. This clay stabilizer does not decompose at temperatures up to 210℃. Chinese patent document CN106675534A discloses a temperature- and salt-resistant anti-swelling clay stabilizer prepared from phthalic anhydride, n-octanol, 2-(dimethylamino)chloromethane hydrochloride, and benzyl bromide. This stabilizer effectively adsorbs onto the clay surface at 250℃ and a mineralization of 200,000 mg / L, thus protecting the clay.

[0003] Currently used treatment agents, while capable of adsorbing and protecting clay under high-temperature and high-salt conditions, primarily target clay within formations, aiming to prevent its hydration, expansion, dispersion, and migration. However, the clay in water-based drilling fluids is already fully hydrated and expanded, making it difficult to integrate with these clay stabilizers. Therefore, developing a clay protectant that can effectively adsorb onto the clay surface in drilling fluids under high-temperature and high-salt conditions, providing highly efficient protection, is of great significance for improving drilling fluid performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay, its preparation method, and its application.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing a water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay includes the following steps:

[0007] (1) At 0-5℃, DL-homocysteine ​​thiolactone hydrochloride and sodium bicarbonate were added to a mixed solvent of water and ethyl acetate. After stirring evenly, sodium allyl sulfonate and acryloyl chloride were added at 0-5℃. After stirring evenly, the reaction was carried out to obtain intermediate product A.

[0008] (2) Disperse intermediate product A in anhydrous ethanol, add short-chain alkylamine, isophorone diisocyanate and polyvinylpyrrolidone, stir evenly and react to obtain a water-based drilling fluid anti-240℃ high temperature and anti-saturated salt clay protectant.

[0009] According to a preferred embodiment of the present invention, the mass ratio of sodium bicarbonate and DL-homocysteine ​​thiolactone hydrochloride in step (1) is 2-3:1.

[0010] According to a preferred embodiment of the present invention, the mass ratio of water to ethyl acetate in the mixed solvent in step (1) is 1-2:1; and the mass ratio of the total mass of DL-homocysteine ​​thiolactone hydrochloride, sodium allyl sulfonate and acryloyl chloride to the mass of the mixed solvent is 1:2-8.

[0011] According to a preferred embodiment of the present invention, the molar ratio of DL-homocysteine ​​thiolactone hydrochloride, sodium allyl sulfonate and acryloyl chloride in step (1) is 1:0.5-2:0.5-2; more preferably 1:1:1.

[0012] According to a preferred embodiment of the present invention, the temperature of the reaction in step (1) is 15-25°C and the reaction time is 10-15h.

[0013] According to a preferred embodiment of the present invention, in step (1), after the reaction is completed, a post-processing step is further included, the specific steps of which are as follows: the reaction solution obtained from the reaction is added to a saturated sodium chloride solution, wherein the mass ratio of the saturated sodium chloride solution to the mixed solvent is 1-2:1; then the liquid is separated, the solvent is removed by rotary evaporation of the obtained ethyl acetate phase, the obtained solid is washed with anhydrous ethanol 3-5 times, and dried at 70-90°C to constant weight to obtain intermediate product A.

[0014] According to a preferred embodiment of the present invention, the mass ratio of anhydrous ethanol to intermediate product A in step (2) is 10-30:1.

[0015] According to a preferred embodiment of the present invention, the short-chain alkylamine in step (2) is one of n-propylamine, n-butylamine, n-pentylamine, and n-hexylamine; the molar ratio of the short-chain alkylamine to DL-homocysteine ​​thiolactone hydrochloride is 0.2-1:1, more preferably 0.7-0.8:1.

[0016] According to a preferred embodiment of the present invention, the molar ratio of isophorone diisocyanate and DL-homocysteine ​​thiolactone hydrochloride in step (2) is 0.2-1:1, and more preferably 0.4-0.6:1.

[0017] According to a preferred embodiment of the present invention, the polyvinylpyrrolidone in step (2) is PVP-K30; the mass ratio of the polyvinylpyrrolidone to intermediate product A is 0.04-0.1:1; PVP is added as a dispersant to promote the dispersion of intermediate product, alkylamine and isophorone diisocyanate and stabilize the system.

[0018] According to a preferred embodiment of the present invention, the temperature of the reaction in step (2) is 35-45°C, and the reaction time is 3-5 hours.

[0019] According to a preferred embodiment of the present invention, in step (2), after the reaction is completed, a post-processing step is further included, the specific steps of which are as follows: the product obtained from the reaction is dried at 70-80°C to constant weight, the solid obtained is washed with anhydrous ethanol and dried again at 70-80°C to constant weight, and finally washed with deionized water and dried at 70-80°C to constant weight to obtain a water-based drilling fluid resistant to 240°C high temperature and saturated salt clay protection agent.

[0020] The present invention also provides a water-based drilling fluid protective agent resistant to high temperature of 240℃ and saturated salt clay, which is prepared by the above preparation method.

[0021] According to the present invention, the above-mentioned water-based drilling fluid anti-high temperature and anti-saturated salt clay protectant is applied in deep well and ultra-deep well water-based drilling fluid. The mass fraction of the clay protectant in the drilling fluid is 3-5%, and a very small amount can play a good protective role for the clay in the drilling fluid.

[0022] The technical features and beneficial effects of this invention are as follows:

[0023] 1. The water-based drilling fluid anti-240℃ high-temperature and anti-saturated salt clay protectant of the present invention is an amphiphilic small molecule polymer prepared from DL-homocysteine ​​thiolactone hydrochloride, sodium allyl sulfonate, acryloyl chloride, isophorone diisocyanate, and short-chain alkylamines. It can effectively and directionally adsorb onto the surface of clay under high temperature and high salt conditions. The outer alkylamines enhance the repulsive force between clay particles, increase the absolute value of the zeta potential on the clay surface, maintain good dispersion of the clay, and prevent agglomeration failure. Simultaneously, the polymer chains can form a temperature- and salt-resistant protective film on the clay surface, preventing the clay from being damaged by high temperature and high salt, thus protecting the clay under high temperature or high temperature and high salt conditions.

[0024] 2. The clay protectant of this invention has a small molecular weight, allowing it to bind tightly to clay without needing to coil. It can form multi-point adsorption with clay, resulting in high efficiency and strong salt resistance. It uses highly stable structural units as the polymer backbone, and the molecular chain contains amide groups, sulfonic acid groups, and other groups with strong hydrophilicity. The aromatic rings on the molecular chain have a certain degree of rigidity, strong temperature resistance, and are not sensitive to salt, maintaining good performance in high-temperature and high-salt environments.

[0025] 3. The clay protectant of this invention is obtained through the ring-opening polymerization reaction of thiolactones. DL-homocysteine ​​thiolactone hydrochloride is the thiolactone monomer. The sulfonic acid group in sodium allyl sulfonate enhances the temperature and salt resistance of the clay protectant. Acryloyl chloride monomer has high activity and can polymerize well with the thiolactone monomer. Furthermore, the acyl chloride group can react with alkylamines to generate strongly adsorbing amide groups, enhancing the clay protectant's adsorption capacity for clay. The outward-facing chains of the alkylamine enhance the repulsive force between clay particles. Isophorone diisocyanate introduces heterocycles, enhancing the rigidity of the clay protectant's molecular chain and improving its temperature and salt resistance. The function of the clay protectant of this invention is to protect the fully hydrated and dispersed clay in the drilling fluid, thereby improving the temperature and salt resistance of the drilling fluid system. It maintains good hydration, expansion, and dispersion of the clay under high temperature and high salt conditions through directional adsorption on the surface of the clay, thus stabilizing the drilling fluid system. Detailed Implementation

[0026] The specific embodiments of the present invention will be further described below. The present invention can be better understood from the following examples. However, those skilled in the art will readily understand that the specific material ratios, process conditions, and results described in the embodiments are for illustrative purposes only and should not, and will not, limit the present invention as described in detail in the claims.

[0027] Unless otherwise specified, all materials used in the following examples and comparative examples are commercially available, and all methods used are conventional methods in the art.

[0028] Example 1

[0029] A method for preparing a water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay includes the following steps:

[0030] (1) Mix 195g of water and 195g of ethyl acetate to obtain a mixed solvent. Cool the mixed solvent to 0-5℃ in an ice-water bath. Add 30.72g (200mmol) of DL-homocysteine ​​thiolactone hydrochloride and 76.8g of sodium bicarbonate to the mixed solvent. Stir at 300r / min for 30min in an ice-water bath at 0-5℃. Continue to add 28.8g (200mmol) of sodium allyl sulfonate and 18.1g (200mmol) of acryloyl chloride. Stir in an ice-water bath at 0-5℃. The mixture was stirred at 300 rpm for 30 min in a bath, then heated to 20 °C and stirred at 300 rpm for 12 h at 20 °C. After the reaction was complete, 390 g of saturated sodium chloride solution was added to the reaction solution, and the mixture was transferred to a separatory funnel for extraction. The resulting upper ethyl acetate phase was placed in a rotary evaporator and the ethyl acetate was removed by rotary evaporation. The solid obtained by rotary evaporation was washed three times with anhydrous ethanol and then dried in an oven at 80 °C to constant weight to obtain intermediate product A52.3 g.

[0031] (2) 52.3g of intermediate product A was dispersed in 1046g of anhydrous ethanol, and 11.68g (160mmol) of n-butylamine, 22.2g (100mmol) of isophorone diisocyanate and 2.6g of PVP-K30 were added. The mixture was stirred at 300r / min for 30min and then transferred to a flask. The mixture was reacted at 40℃ for 4h. The product obtained from the reaction was dried in an 80℃ oven to constant weight. The solid obtained was washed with anhydrous ethanol and dried again in an 80℃ oven to constant weight. Then it was washed again with deionized water and dried in an 80℃ oven to constant weight to obtain water-based drilling fluid anti-240℃ high temperature and anti-saturated salt clay protective agent A1.

[0032] Example 2

[0033] A method for preparing a water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay includes the following steps:

[0034] (1) Mix 195g of water and 195g of ethyl acetate to obtain a mixed solvent. Cool the mixed solvent to 0-5℃ in an ice-water bath. Add 30.72g (200mmol) of DL-homocysteine ​​thiolactone hydrochloride and 76.8g of sodium bicarbonate to the mixed solvent. Stir at 300r / min for 30min in an ice-water bath at 0-5℃. Continue to add 43.2g (300mmol) of sodium allyl sulfonate and 27.15g (300mmol) of acryloyl chloride. Stir at 0-5℃. The mixture was stirred at 300 rpm for 30 min in a water bath, then heated to 20 °C and stirred at 300 rpm for 12 h at 20 °C. After the reaction was complete, 390 g of saturated sodium chloride solution was added to the reaction solution, and the mixture was transferred to a separatory funnel for extraction. The resulting upper ethyl acetate phase was placed in a rotary evaporator and the ethyl acetate was removed by rotary evaporation. The solid obtained by rotary evaporation was washed three times with anhydrous ethanol and then dried in an oven at 80 °C to constant weight to obtain intermediate product A63.2 g.

[0035] (2) 63.2g of intermediate product A was dispersed in 1264g of anhydrous ethanol, and 11.68g (160mmol) of n-butylamine, 22.2g (100mmol) of isophorone diisocyanate and 3.2g of PVP-K30 were added. The mixture was stirred at 300r / min for 30min and then transferred to a flask. The mixture was reacted at 40℃ for 4h. The product was dried in an oven at 80℃ to constant weight. The solid was washed with anhydrous ethanol and dried again in an oven at 80℃ to constant weight. Then it was washed again with deionized water and dried in an oven at 80℃ to constant weight to obtain 240℃ high temperature saturated salt clay protectant A2.

[0036] Example 3

[0037] A method for preparing a water-based drilling fluid anti-high temperature and anti-saturated salt clay protectant at 240℃ is as described in Example 1, except that: in step (2), 13.14g (180mmol) of n-butylamine and 33.3g (150mmol) of isophorone diisocyanate are added, and the other conditions are the same as in Example 1, to obtain water-based drilling fluid anti-high temperature and anti-saturated salt clay protectant A3.

[0038] Comparative Example 1

[0039] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that sodium allyl sulfonate is not added in step (1) to obtain clay protectant DA1.

[0040] Comparative Example 2

[0041] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that acryloyl chloride is not added in step (1) to obtain clay protectant DA2.

[0042] Comparative Example 3

[0043] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that isophorone diisocyanate is not added in step (2), and clay protectant DA3 is obtained.

[0044] Comparative Example 4

[0045] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that in step (1), the short-chain alkylamine n-butylamine is replaced with the long-chain alkylamine octadecylamine to obtain clay protectant DA4.

[0046] Comparative Example 5

[0047] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that PVP-K30 is not added in step (2), and clay protectant DA5 is obtained.

[0048] Comparative Example 6

[0049] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that sodium bicarbonate is not added in step (1), and clay protectant DA6 is obtained.

[0050] Comparative Example 7

[0051] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that: in step (1), an ice-water bath is not performed, but stirring is carried out at room temperature to obtain clay protectant DA7.

[0052] Comparative Example 8

[0053] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that: in step (1), the molar ratio of DL-homocysteine ​​thiolactone hydrochloride to sodium allyl sulfonate is 1:2.5, and clay protectant DA8 is obtained.

[0054] Comparative Example 9

[0055] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that: in step (1), the molar ratio of DL-homocysteine ​​thiolactone hydrochloride to acryloyl chloride is 1:2.5, and clay protectant DA9 is obtained.

[0056] Comparative Example 10

[0057] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that in step (2), the molar ratio of DL-homocysteine ​​thiolactone hydrochloride to isophorone diisocyanate is 1:1.5, and clay protectant DA10 is obtained.

[0058] Comparative Example 11

[0059] A method for preparing a clay protectant for water-based drilling fluid is described in Example 1, except that in step (2), the molar ratio of DL-homocysteine ​​thiolactone hydrochloride to short-chain alkylamine n-butylamine is 1:1.5, and clay protectant DA11 is obtained.

[0060] Experimental Example 1

[0061] The bentonite used in the test example was purchased from Shandong Huawai Bentonite Co., Ltd., and the drilling fluid used sodium-based bentonite.

[0062] Sodium carbonate was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0063] DSP-1, a filtration loss reducer, was purchased from Shandong Deshunyuan Petroleum Technology Co., Ltd.

[0064] The chelated bitumen was purchased from Beijing Hongqin Petroleum Additives Co., Ltd., model number HQ-10;

[0065] The potassium polyacrylamide inhibitor was purchased from Henan Haiyun Environmental Protection Technology Co., Ltd., and the model was KPAM.

[0066] Lubricant RH-3 was purchased from Zhengzhou Jingyuan Slurry Materials Co., Ltd., and the product conforms to the standard SY / T 5662-1994.

[0067] Silica was purchased from Shandong Yousuo Chemical Technology Co., Ltd., via the gas phase method, with a median particle size of 5 μm.

[0068] Unless otherwise specified, all “parts” in the following tests refer to parts by weight.

[0069] The clay protectants prepared in the examples and comparative examples were used to formulate water-based drilling fluids, and their performance was tested.

[0070] The composition of the water-based drilling fluid is as follows: 100 parts water, 4 parts bentonite, 0.3 parts sodium carbonate, 2.5 parts DSP-1 filtration loss reducer, 0.5 parts potassium polyacrylamide inhibitor, 3 parts chelated asphalt HQ-10, 3 parts lubricant RH-3, 3 parts silica plugging agent, and 5 parts clay protectant.

[0071] According to the above proportions, water was added to a high-speed mixing cup, and bentonite and sodium carbonate were added under low-speed stirring for 24 hours. Filtration loss reducer DSP-1 was added, and the mixture was stirred at high speed for 20 minutes. Potassium polyacrylamide inhibitor was added, and the mixture was stirred at high speed for 20 minutes. Chelated asphalt HQ-10 was added, and the mixture was stirred at high speed for 20 minutes. Lubricant RH-3 was added, and the mixture was stirred at high speed for 20 minutes. Silica, a plugging agent, was added, and the mixture was stirred at high speed for 20 minutes. Clay protectant was added, and the mixture was stirred at high speed for 20 minutes to obtain the test water-based drilling fluid. The low-speed stirring speed was 2000 r / min, and the high-speed stirring speed was 8000 r / min. The clay protectant prepared in Examples 1-3 was added. The water-based drilling fluids without clay protectant and those with clay protectant prepared in Comparative Examples 1-11 were respectively designated as F1, F2, F3, DF0, DF1, DF2, DF3, DF4, DF5, DF6, DF7, DF8, DF9, DF10, and DF11.

[0072] 1. Drilling fluid performance testing

[0073] Take 400 mL of each of the above drilling fluids F1-F3 and DF0-DF11, add 36 wt% NaCl, stir at 5000 rpm for 20 min, then transfer to an aging tank and place in a roller furnace. Roll at 240℃ for 16 hours, then remove and cool to room temperature. Stir again at 5000 rpm for 20 min. Then, determine the apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), dynamic shear force (YP, Pa), and medium-pressure API filtration loss (FL) of the above drilling fluids according to GB / T16783.1-2006. API ,mL), high temperature and high pressure HTHP filtration loss (FL HTHP (mL), the results are shown in Table 1.

[0074] Table 1 Drilling Fluid Performance Tests

[0075] Fl 58.5 43.5 15 0.8 22.4 F2 57 42.5 14.5 1.0 24.6 F3 56.5 41 15.5 1.0 26.2 DF0 47.5 39 8.5 1.4 46.4 DFl 45 37.5 7.5 2.2 48.6 DF2 54 39 15 1.2 34.4 DF3 50.5 36.5 14 1.4 37.6 DF4 47 41 6 2.0 40.6 DF5 46 39.5 6.5 2.2 47.4 DF6 50 43 7 2.0 39.8 DF7 46 38.5 7.5 2.2 43.8 DF8 42 36 6 3.0 47.6 DF9 49 39.5 9.5 2.8 44.4 DF10 48.5 40 8.5 3.2 49.8 DF11 50 43.5 6.5 2.6 43.2

[0076] As can be seen from the data in Table 1, when the water-based drilling fluid protectant against 240°C high temperature and saturated salt clay of the present invention is used in the drilling fluid, the viscosity of the drilling fluid increases slightly, and the API and HTHP filtration loss can be reduced by about 50%, indicating that the clay is effectively protected and the drilling fluid exhibits good performance.

[0077] 2. Drilling fluid particle size and zeta potential

[0078] 400 mL of drilling fluids F1-F3 and DF0-DF11 were taken respectively, and 36 wt% NaCl was added. After stirring at 5000 rpm for 20 min, the mixture was transferred to an aging tank and placed in a roller furnace. The tank was then rolled at 240℃ for 16 hours. After cooling to room temperature, the mixture was stirred at 5000 rpm for another 20 min. The zeta potential of the aged drilling fluids was measured using a Mastersizer-3000 zeta potential analyzer, with each sample repeated three times and the average value taken. The particle size of the aged drilling fluids was measured using a Mastersizer-3000 particle size analyzer at a scan rate of 10,000 times per second. The results are shown in Table 2.

[0079] Table 2. Drilling fluid particle size and zeta potential

[0080]

[0081]

[0082] The data shows that the water-based drilling fluid protectant with high temperature resistance (240℃) and saturated salt resistance of this invention can reduce the average particle size of the drilling fluid. This indicates that the clay particles in the drilling fluid can maintain a small size, and the clay protectant plays a role in preventing the clay from agglomerating and failing under high temperature and high salt conditions. This is also verified by the Zeta potential; the clay protectant increases the absolute value of the drilling fluid's Zeta potential, thus improving the stability of the drilling fluid.

[0083] In summary, the water-based drilling fluid protectant for 240°C high-temperature and saturated salt clay of the present invention can effectively protect the hydrated and swollen clay in the drilling fluid under high-temperature and high-salt conditions, improving the performance of the drilling fluid and meeting the needs of deep and ultra-deep drilling. Furthermore, the composition and proportion of raw materials must be controlled within the range of the present invention to obtain a clay protectant with excellent performance.

[0084] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. In addition, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be considered as the content disclosed by the present invention.

Claims

1. A method for preparing a water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay, comprising the following steps: (1) At 0-5℃, DL-homocysteine ​​thiolactone hydrochloride and sodium bicarbonate were added to a mixed solvent of water and ethyl acetate. After stirring until homogeneous, sodium allyl sulfonate and acryloyl chloride were added at 0-5℃. After stirring until homogeneous, the reaction was carried out to obtain intermediate product A. The mass ratio of sodium bicarbonate to DL-homocysteine ​​thiolactone hydrochloride was 2-3:

1. The molar ratio of DL-homocysteine ​​thiolactone hydrochloride, sodium allyl sulfonate and acryloyl chloride was 1:0.5-2:0.5-2. The reaction temperature was 15-25℃. The reaction time was 10-15h. (2) Disperse intermediate product A in anhydrous ethanol, add short-chain alkylamine, isophorone diisocyanate and polyvinylpyrrolidone, stir evenly and react to obtain a water-based drilling fluid anti-240℃ high temperature and anti-saturated salt clay protectant; the short-chain alkylamine is one of n-propylamine, n-butylamine, n-pentylamine and n-hexylamine; the molar ratio of the short-chain alkylamine and DL-homocysteine ​​thiolactone hydrochloride is 0.2-1:1; the molar ratio of isophorone diisocyanate and DL-homocysteine ​​thiolactone hydrochloride is 0.2-1:1; the mass ratio of polyvinylpyrrolidone to intermediate product A is 0.04-0.1:

1.

2. The preparation method of the water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay according to claim 1, characterized in that, In step (1), the mass ratio of water to ethyl acetate in the mixed solvent is 1-2:1; the total mass ratio of DL-homocysteine ​​thiolactone hydrochloride, sodium allyl sulfonate and acryloyl chloride to the mass of the mixed solvent is 1:2-8.

3. The preparation method of the water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay according to claim 1, characterized in that, The molar ratio of DL-homocysteine ​​thiolactone hydrochloride, sodium allyl sulfonate and acryloyl chloride in step (1) is 1:1:

1.

4. The preparation method of the water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay according to claim 1, characterized in that, After the reaction in step (1) is completed, a post-processing step is also included. The specific steps are as follows: the reaction solution obtained from the reaction is added to a saturated sodium chloride solution, wherein the mass ratio of the saturated sodium chloride solution to the mixed solvent is 1-2:1; then the liquid is separated, the solvent is removed by rotary evaporation of the obtained ethyl acetate phase, the obtained solid is washed with anhydrous ethanol 3-5 times, and dried at 70-90℃ to constant weight to obtain intermediate product A.

5. The preparation method of the water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay according to claim 1, characterized in that, The mass ratio of anhydrous ethanol to intermediate product A in step (2) is 10-30:1; The molar ratio of the short-chain alkylamine to DL-homocysteine ​​thiolactone hydrochloride is 0.7-0.8:

1.

6. The preparation method of the water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay according to claim 1, characterized in that, The molar ratio of isophorone diisocyanate and DL-homocysteine ​​thiolactone hydrochloride in step (2) is 0.4-0.6:

1.

7. The preparation method of the water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay according to claim 1, characterized in that, The polyvinylpyrrolidone mentioned in step (2) is PVP-K30.

8. The preparation method of the water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay according to claim 1, characterized in that, The reaction temperature in step (2) is 35-45℃, and the reaction time is 3-5h; After the reaction is complete, a post-processing step is also included, the specific steps of which are as follows: the product obtained from the reaction is dried at 70-80℃ to constant weight, the solid obtained is washed with anhydrous ethanol and dried again at 70-80℃ to constant weight, and finally washed with deionized water and dried at 70-80℃ to constant weight to obtain a water-based drilling fluid resistant to 240℃ high temperature and saturated salt clay protection agent.

9. A water-based drilling fluid protective agent resistant to 240℃ high temperature and saturated salt clay, characterized in that, It was prepared using the preparation method described in claim 1.

10. The application of the 240℃ high-temperature resistant and saturated salt resistant clay protective agent for water-based drilling fluid according to claim 9 in deep well or ultra-deep well water-based drilling fluid, wherein the mass fraction of the clay protective agent in the drilling fluid is 3-5%.

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