High-pressure salt water invasion resistant fluid loss additive and preparation method thereof

Abstract

This application discloses a high-pressure brine-resistant filtration loss reducer and its preparation method, belonging to the field of oil and gas well drilling engineering. Based on the requirements for resistance to complex salts, especially calcium and magnesium, this application optimizes the molecular structure of the high-pressure brine-resistant filtration loss reducer and introduces an acryloylmorpholine monomer, significantly improving its temperature resistance, stability, and salt tolerance. Since the copolymerization reaction of the selected monomer is relatively simple, the polymerization reaction adopts free radical solution polymerization. The prepared filtration loss reducer has achieved good performance in both laboratory and field application evaluations.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well drilling engineering, and specifically relates to a high-pressure brine erosion filtration reducer and its preparation method. Background Technology

[0002] As global oil and gas exploration and development expands towards deeper oil and gas resources, the probability of encountering complex formations is constantly increasing. Facing the high-temperature and complex environment of deep wells, drilling fluid aging becomes more difficult to control, making the regulation of drilling fluid rheology and control of filtration loss particularly important. With the increasing complexity of formations, the probability of encountering high-pressure brine layers is constantly rising, and drilling fluids contaminated with oil, gas, salt, or poor soil are highly susceptible to contamination. Filtration loss reducers, as important additives in drilling fluids, play a crucial role in adjusting filtration loss and rheology. By designing and optimizing the molecular structure of filtration loss reducers, temperature and salt resistance can be achieved.

[0003] Investigations into the fouling mechanism of high-pressure brine revealed that it significantly impacts the filtration loss of water-based drilling fluids, primarily due to the influence of divalent cations. Firstly, it contaminates clay particles; for example, calcium ions can adsorb onto the surface of clay particles or enter the interlayer space for ion exchange, severely compressing the electric double layer and disrupting the stability of colloidal particles, leading to agglomeration and flocculation of hydrated bentonite particles. Secondly, high temperature and high calcium environments easily destroy the adsorption and protective effects of polymer treatment agents, ultimately making it difficult to adjust the filtration loss and rheological properties of the drilling fluid. Currently, commonly used polymer filtration loss reducers have strong temperature resistance but weak calcium resistance; their effectiveness is significantly reduced in the face of high-pressure brine fouling, severely impacting safe well completion and drilling efficiency.

[0004] Chinese patent CN202011612777.5 discloses a high-temperature and saturated brine-resistant filtration reducer for drilling fluids, comprising the following components: acrylamide, formaldehyde, 2-acrylamido-2-methylpropanesulfonic acid, dimethyldiallyl ammonium chloride, N-vinylpyrrolidone, sodium hydroxide, initiator, and water. This filtration reducer exhibits strong filtration reduction properties in freshwater slurries, compound brine slurries, and saturated brine slurries. It is suitable for reducing filtration in drilling fluids of various densities, especially high densities. It possesses strong salt resistance and inhibition properties, and also has a certain diluting effect. It can be added directly or formulated into a gel to drilling fluids.

[0005] Chinese patent CN201811495476.1 discloses a high-temperature, high-salinity-water-based drilling fluid filtration reducer and its preparation method. The filtration reducer is prepared from the following raw materials in parts by weight: 700 parts sulfonyl phenolic resin, 3-8 parts formaldehyde, 6-15 parts melamine, 10-25 parts polybasic acid, 4-8 parts polyol, 10-22 parts sulfite, 6-20 parts metabisulfite, and 60-80 parts water. By modifying the sulfonyl phenolic resin and introducing melamine, the resulting filtration reducer contains more aromatic rings, thus enhancing its temperature resistance.

[0006] The literature "Research and Application of High-Saltification Saltwater Drilling Fluid System" (Hou Jie et al., Western Exploration Engineering) discloses a viscosity-enhancing and filtration-reducing agent, DSP-1, which is synthesized from acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, acrylonitrile, and N-isopropylacrylamide monomers. DSP-1 has a high-bond-energy C-C bond as the main chain, with sulfonic acid, cyano, amide, and carboxyl groups as hydration groups. It has a large molecular weight and a moderately cross-linked network structure, which makes it exhibit good viscosity-enhancing, shear-lifting, and high-temperature degradation resistance effects. After introducing the N-isopropylacrylamide monomer, the polymer exhibits a temperature-sensitive effect at high temperatures, and the hydrophobic part aggregates, which can not only improve the viscosity and shear force of the drilling fluid, but also form insoluble micelles, thereby achieving the effect of plugging and reducing filtration loss.

[0007] The literature "Development of a Quaternary Copolymer of DMAA / AMPS / DMDAAC / NVP for Temperature and Salt Resistance Drilling Fluid Filtration Reduction" (Bai Qiuyue et al., Oilfield Chemistry) describes the development of a temperature and salt resistance drilling fluid filtration reduction agent, WB-FLA-2, which is obtained through the copolymerization reaction of N,N-dimethylacrylamide (DMAA), dimethyl diallyl ammonium chloride (DMDAAC), N-vinylpyrrolidone (NVP), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). The API filtration loss of the salt cement slurry containing 30% NaCl + 2% WB-FLA-2 after aging at 150℃ for 24 hours showed little difference before and after aging, both being less than 15 mL, demonstrating excellent filtration reduction performance and temperature and salt resistance.

[0008] The research on temperature and salt resistant filtration loss reducers has made great progress, and the performance of some products has reached the international advanced level. Some experience has been accumulated in application. However, the research on polymer-based filtration loss reducers with good resistance to complex salts, high-pressure brine, and especially calcium in high-pressure brine is not yet ideal. Therefore, this invention is proposed. Summary of the Invention

[0009] Based on the above problems, the purpose of this invention is to provide a drilling fluid resistant to high-pressure brine immersion and its preparation method for drilling fluids suitable for deep wells in high-pressure brine formations. Based on the requirements of resistance to complex salts, especially calcium and magnesium, the molecular structure of the resistant high-pressure brine immersion and filtration reduction agent is optimized and an acryloylmorpholine monomer is introduced, which significantly improves the temperature resistance, stability and salt resistance.

[0010] To achieve the above objectives, this application adopts the following technical solution:

[0011] On the one hand, this application provides a filtration loss reducer resistant to high-pressure brine erosion, the molecular structure of which is shown in Formula 1 below:

[0012]

[0013] In the formula: x, y, z and w represent the molar number of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, ethyl 2-(dimethylamino)methacrylate and acryloylmorpholine, respectively, where x:y:z:w=(1-5):(3-6):(0.5-2):(0.5-2).

[0014] On the other hand, this application also provides a method for preparing the above-mentioned high-pressure brine immersion filtration reducer, comprising the following steps:

[0015] (1) Add the reactant monomer to a three-necked flask, dissolve it in distilled water, adjust the pH of the solution, stir with a magnetic stirrer, and keep the temperature of the reaction system below 20°C during stirring to obtain a mixture;

[0016] (2) Purge the mixture obtained in step (1) with nitrogen for 20 minutes, then heat and maintain the nitrogen atmosphere to carry out the reaction. After the reaction is completed, take out the product, wash it with anhydrous ethanol to remove impurities, dry it in an 80°C oven for 16 hours, grind it, and the filtration loss reducer is obtained.

[0017] The reaction monomers mentioned in step (1) above are 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, ethyl 2-(dimethylamino)methacrylate and acryloylmorpholine.

[0018] The molar ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, ethyl 2-(dimethylamino)methacrylate and acryloylmorpholine is (1-5):(3-6):(0.5-2):(0.5-2);

[0019] Preferably, the molar ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, ethyl 2-(dimethylamino)methacrylate and acryloylmorpholine is (2-3):(5-6):(1.5-2):(0.5-1).

[0020] The total weight of the reactants in step (1) above accounts for 10-25 wt% of the total weight of the solution formed by the reactants and distilled water, preferably 12-18 wt%.

[0021] The pH of the solution adjusted in step (1) above is 5-9, preferably 8.

[0022] The stirring speed mentioned in step (1) above is 360-500 r / min; preferably 450 r / min.

[0023] The temperature for heating in step (2) above is 40-80℃, preferably 50-60℃.

[0024] The reaction time described in step (2) above is 3.5-4.5 h; preferably 4 h.

[0025] In some preferred embodiments, the mixture in step (1) above further contains an initiator, wherein the initiator is azobisisobutyrazoline hydrochloride, and the amount of the initiator added is 0.05-0.50 wt% of the total weight of the reactants, preferably 0.20-0.35 wt%.

[0026] In the implementation of this invention, the molecular structure of the polymer filtration loss reducer was optimized by studying the fouling mechanism of high-pressure brine. Acryloylmorpholine monomer was introduced, possessing double bonds and cyclic morpholine groups, effectively improving the rigidity and compatibility of the polymer. 2-Acrylamido-2-methylpropanesulfonic acid was introduced to enhance the temperature and salt resistance of the polymer filtration loss reducer. Ethyl 2-(dimethylamino)methacrylate was introduced to enhance the dispersibility of the polymer with clay under high salinity and high temperature conditions. Finally, acrylamide was used to formulate the filtration loss reducer. Since the copolymerization reaction of the selected monomers is relatively simple, free radical solution polymerization was employed. The prepared filtration loss reducer achieved good performance in both indoor and field application evaluations.

[0027] Compared with the prior art, the beneficial effects of this application are as follows:

[0028] The drilling fluid filtration reducer provided in this application for high-pressure brine formations has a temperature resistance of up to 180℃. When applied to drilling in high-pressure brine formations, it can effectively avoid the influence of divalent cations in the brine, increase the protective effect of the drilling fluid to effectively reduce filtration loss, thereby maintaining wellbore stability and improving drilling efficiency and safety. Attached Figure Description

[0029] Figure 1 The infrared spectrum of the filtration loss reducer prepared in Example 1. Detailed Implementation

[0030] The implementation methods of this application are described below through specific embodiments. Those skilled in the art should recognize that these specific embodiments are only specific implementation schemes selected to achieve the purpose of this application, and are not intended to limit the technical solutions of this application.

[0031] Example 1: A high-pressure brine immersion filtration reducer and its preparation method

[0032] (1) First, weigh 23.29g of 2-acrylamide-2-methyl-propanesulfonic acid and place it in a beaker. Dissolve it in 381g of distilled water and adjust the pH of the solution to 8. Then add 18.64g of acrylamide, 13.74g of ethyl 2-(dimethylamino)methacrylate, 5.29g of acryloylmorpholine and 0.165g of initiator azobisisobutyrazoline hydrochloride to the container. Stir with a magnetic stirrer at 450r / min. During stirring, keep the temperature of the reaction system below 20℃. Transfer the reaction system to a reaction vessel. First, purge with nitrogen for 20 minutes. Then, heat the mixture to 55℃ using a water bath and maintain the nitrogen atmosphere for 4 hours. Take out the product, remove impurities with anhydrous ethanol, dry it in an 80℃ drying oven for 16 hours, and grind it to obtain the filtration loss reducer.

[0033] The molar ratio of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, ethyl 2-(dimethylamino)methacrylate and acryloylmorpholine in the product is 2.25:5.25:1.75:0.75.

[0034] Example 1-1

[0035] The difference from Example 1 is that the molar percentage of acryloylmorpholine in the product is 0.5, that is, the amount of acryloylmorpholine added is 3.53g. Other operations and steps are the same as in Example 1.

[0036] Examples 1-2

[0037] The difference from Example 1 is that the molar percentage of acryloylmorpholine in the product is 1.0, that is, the amount of acryloylmorpholine added is 7.06g. Other operations and steps are the same as in Example 1.

[0038] Examples 1-3

[0039] The difference from Example 1 is that the molar ratio of acrylomorpholine in the product is 1.5, that is, the amount of acrylomorpholine added is 10.59g. Other operations and steps are the same as in Example 1.

[0040] Example 2: A high-pressure brine immersion filtration reducer and its preparation method

[0041] Add 500 kg of tap water to a stainless steel corrosion-resistant reactor with a capacity of 3-3.5 tons. Turn on the stirrer and add 117 kg of 2-acrylamide-2-methyl-propanesulfonic acid to the reactor at a rate of 25 kg per minute. After stirring for 10 minutes, add sodium hydroxide at a rate of 5 kg per minute to adjust the pH to about 8. Add 1000 kg of tap water and stir for 10 minutes. Add 93 kg of acrylamide to the reactor at a rate of 20 kg per minute and stir for 10 minutes. Add 69 kg of ethyl 2-(dimethylamino)methacrylate to the reactor at a rate of 20 kg per minute and stir for 10 minutes. Add 0.82 kg of azobisisobutyrazoline hydrochloride and 400 kg of tap water. Purge with nitrogen gas and stir for 20 minutes. Turn on the heater and heat to 55°C. React for 4 hours. Cool to room temperature, remove the reactants, dry them, pulverize and sieve them to obtain the product, which is the filtration loss reducer.

[0042] Comparative Example 1

[0043] The difference from Example 1 is that no acrylomorpholine is added, and the product does not contain acrylomorpholine molecular chain segments. Other operations and steps are the same as in Example 1.

[0044] Comparative Example 2

[0045] The difference from Example 1 is that the molar ratio of acrylomorpholine in the product is 2.5, that is, the amount of acrylomorpholine added is 17.65g. Other operations and steps are the same as in Example 1.

[0046] Effect verification:

[0047] Test Example 1: Rheological and Filtration Properties of Filtration Reducer

[0048] Preparation of composite saline-based slurry: 400mL tap water + 20g NaCl + 40g CaCl2 + 1g NaHCO3 + 10% evaluation soil.

[0049] Preparation and testing of test slurries: 1% by mass of the sample was added to the composite brine-based slurry, and the mixture was stirred at a high speed of 8000 rpm until homogeneous. The rheological properties and filtration loss of each test slurry were then measured. The slurries were then aged at 180℃ for 16 hours, and the rheological properties and filtration loss of each test slurry were tested again. The results are shown in Table 1.

[0050] Table 1. Related comparative experimental data

[0051]

[0052]

[0053] The test results in Table 1 above show that introducing the rigid large side group monomer acryloylmorpholine into the polymer molecular chain is beneficial to improving the polymer's resistance to high temperature, resistance to complex salts, and filtration loss. At the same time, the molar ratio of this monomer should not be too high or too low, and the molar ratio between 0.5 and 1 is most suitable.

[0054] Test Example 2: Determination of the relative molecular mass of the filtration loss reducer

[0055] The relative molecular mass of the sample prepared in Example 1 was determined using gel permeation chromatography (GPC), and the test results are shown in Table 2.

[0056] Table 2 Relative Molecular Mass Analysis

[0057] Number average molecular weight Mn Weight-average molecular weight Mw Z-average molecular weight Mz Dispersion D 514424 874256 1285242 1.699

[0058] Test Example 3: Detection of thickening properties of filtrate loss reducer in aqueous solution

[0059] The sample prepared in Example 1 was prepared into aqueous solutions of different concentrations, and its viscosity change curve was tested. The testing instrument was HAAKE MARS, the temperature was at room temperature, and the rotation speed was 600 r / min. The results are shown in Table 3.

[0060] Table 3. Results of viscosity-enhancing performance tests in water.

[0061] Increase / % Apparent viscosity / mPa·s 0.1 8.6 0.2 21.3 0.3 27.7 0.4 38.9 0.5 76.3

[0062] The test results in Table 3 show that the sample prepared in Example 1 significantly increased viscosity in water, and the viscosity-increasing effect became more pronounced with increasing dosage. When the sample dosage increased to 0.5%, the viscosity of the aqueous solution increased by 1.9 times. The viscosity in the polymer aqueous solution is mainly due to the hydrogen bonding between the hydrophilic groups in the polymer molecular chain and water molecules, which fixes the water molecules in a "lock-in" manner within the network structure. The larger the molecular weight, the more chain segments a single molecular chain contains, and the shear viscosity of the polymer increases with increasing molecular weight.

[0063] Experimental Example 4: Effect of Temperature on Viscosity of Filtration Loss Reducer

[0064] To investigate the effect of temperature on the viscosity of the filtration loss reducer solution prepared in Example 1, a 0.5% aqueous solution of the filtration loss reducer was prepared and tested using a Hacker rheometer at a speed of 600 r / min. The experimental results are shown in Table 4.

[0065] Table 4 Effect of Temperature on Viscosity

[0066] Serial Number Temperature / °C Viscosity / mPa·s 1 30 76 2 40 72 3 50 68 4 60 65 5 70 63 6 80 58 7 90 56

[0067] According to the test results in Table 4, the apparent viscosity of the sample solution in Example 1 decreased slightly with increasing temperature, decreasing by 26% between 30-90℃. Since the intrusion of composite brine can reduce the rheological properties of drilling fluid, and excessive intrusion volume can even lead to instability, the CLG-12 solution, with its certain viscosity, helps improve the rheological stability of drilling fluid when exposed to composite brine.

[0068] Test Example 5: Performance Testing of Filtration Loss Reducer in Freshwater-Based Slurry

[0069] To study the filtration loss reduction performance of this product in freshwater-based slurry, 1% of the sample prepared in Example 1 and 1% of the domestic high-temperature resistant polymer filtration loss reducer DSP-2 and 1% of the foreign high-temperature resistant polymer thickening and filtration loss reducer HE300 were added to 4% freshwater-based slurry. The two filtration loss reducers are currently the best treatment agents with good temperature and salt resistance at home and abroad. The experimental results are shown in Table 5 below (aging conditions: 180℃, 16h).

[0070] Preparation of freshwater-based slurry: Take 1000mL of tap water, add 4.0% bentonite by mass, then add 5% soda ash by mass of bentonite, and stir in a slurry mixer at 8000 rpm for 30min. Then place it in a sealed container and cure for 24.0h to obtain 4% freshwater-based slurry.

[0071] Table 5 Performance test of samples in freshwater-based pulp

[0072]

[0073] The test results in Table 5 show that when 1% of the Sample 1 (by mass) was added to the freshwater-based slurry, the medium-pressure filtration loss before and after aging was 4.8 mL and 5.6 mL, respectively. Compared to DSP-2 (76% reduction rate) and HE300 (64% reduction rate), the Sample 1 (81.7% reduction rate) of the medium-pressure filtration loss of the aged freshwater-based slurry demonstrates excellent filtration loss reduction performance.

[0074] Test Example 6: Performance Testing of Filtration Loss Reducer in Saturated Brine-Based Slurry

[0075] To evaluate the salt resistance of the samples prepared in Example 1, saturated brine slurry refers to fresh water slurry with different filtration loss reducers added and then 36% sodium chloride added. The rheological properties and medium-pressure filtration loss were measured. The experimental results are shown in Table 6 (aging conditions: 180°C, 16h).

[0076] Table 6 Performance Tests of Samples in Saturated Brine-Based Slurry

[0077]

[0078] The test results in Table 6 show that the apparent viscosity, plastic viscosity, and dynamic shear force of the saturated brine-based slurry are significantly increased compared to the freshwater-based slurry, and the medium-pressure filtration loss increases substantially after aging. The synthesized sample from Example 1 exhibits better salt resistance than DSP-2 and HE300, especially maintaining a very low medium-pressure filtration loss even after aging.

[0079] Test Example 7: Performance Testing of Filtration Loss Reducer in Composite Brine-Based Slurry

[0080] To evaluate the resistance of the sample prepared in Example 1 to composite salt, 1% by mass of a filtration loss reducer was added to the composite salt slurry (the composite salt slurry formula is as follows: 400mL tap water + 20g NaCl + 40g CaCl2 + 1g NaHCO3 + 10% evaluation soil), and its rheological properties and medium-pressure filtration loss were measured. The experimental results are shown in Table 7 (aging conditions were 180℃ for 16h).

[0081] Table 7 Performance Tests of Samples in Composite Salt-Based Slurry

[0082]

[0083] According to the test results in Table 7, the sample of Example 1 had the lowest medium-pressure filtration loss after aging at 180℃, with a filtration loss of only 2.4mL. However, the filtration loss of the experimental slurries with added DSP-2 and HE300 increased to varying degrees after high-temperature aging. This indicates that the sample of Example 1 has a good effect on resisting composite salt and temperature drop filtration loss.

[0084] Example 8: Performance Testing of Filtration Loss Reducer in High-Temperature, High-Density Drilling Fluid

[0085] Preparation of base slurry: Preparation of fresh water base slurry: Take 1000mL of tap water, add 4.0% bentonite by mass, then add 5% soda ash by mass of bentonite, and stir in a slurry mixer at 8000 rpm for 30min. Then place it in a sealed container and cure for 24.0h to obtain 4% fresh water base slurry.

[0086] Preparation of high-temperature, high-density water-based drilling fluid completion fluid base slurry: Take 400 mL of fresh water-based slurry, stir at 8000 rpm for 20 minutes, and add 0.3-1 parts of anionic polymer filtration reducer, 3-5 parts of sulfonated methylphenol resin type I, 2-6 parts of sulfonated lignite resin, 2-9 parts of sulfonated asphalt powder, 5-8 parts of potassium chloride, and 3-5 parts of lubricant in sequence, and add the corresponding barite. After each addition of a treatment agent, stir at high speed for 20-30 minutes. The high-temperature, high-density water-based drilling fluid of the present invention can be prepared by following the above method.

[0087] Take 400ml of the prepared high-temperature, high-density water-based drilling fluid, stir at 8000 rpm, add 0.3-1 part of the product from Example 1, stir for 30 minutes, and then test its rheology and filtration properties before and after aging (aging conditions are 180℃, 16h). The results are shown in Table 8 below.

[0088] Table 8 Performance Tests of the Product in High-Temperature, High-Density Drilling Fluids

[0089]

[0090] According to the test results in Table 8, the viscosity of the sample from Example 1 increased slightly after being added to the high-temperature, high-density drilling fluid system. The rheological filtration performance of the system remained basically unchanged before and after aging. The high-temperature and high-pressure filtration loss of the experimental slurry after aging was only 9.4 mL, which showed good filtration loss reduction performance compared with the system without the sample from Example 1.

[0091] In summary, the filtration loss reducer provided in this application has good resistance to high-temperature thickening and filtration loss reduction. The introduction of acrylomorpholine monomer significantly improves its temperature resistance, stability and salt resistance. It can also significantly reduce its filtration loss in complex salt environments. Its resistance to complex salt filtration loss reduction performance is superior to similar products at home and abroad.

Claims

1. A high pressure salt water invasion resistant fluid loss additive characterized by: Its molecular structure is shown in Formula 1 below: Equation (1) Where x, y, z and w represent the molar amounts of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, ethyl 2-(dimethylamino)methacrylate and acryloylmorpholine, respectively; x:y:z:w=(2-3):(5-6):(1.5-2):(0.5-1).

2. A method for preparing the high-pressure brine immersion filtration reducer according to claim 1, characterized in that: Includes the following steps: (1) Add the reactant monomer to a three-necked flask, dissolve it in distilled water, adjust the pH of the solution, stir with a magnetic stirrer, and keep the temperature of the reaction system below 20°C during stirring to obtain a mixture; (2) Purge nitrogen into the mixture obtained in step (1) for 20 minutes, then heat and maintain the nitrogen atmosphere to carry out the reaction. After the reaction is completed, take out the product, wash it with anhydrous ethanol to remove impurities, place it in an 80°C drying oven for 16 hours to dry and grind it to obtain the filter loss reducer.

3. The preparation method according to claim 2, characterized in that: The reaction monomers mentioned in step (1) are 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, ethyl 2-(dimethylamino)methacrylate and acryloylmorpholine.

4. The preparation method according to claim 2, characterized in that: The total weight of the reactants in step (1) accounts for 10-25 wt% of the total weight of the solution formed by the reactants and distilled water.

5. The preparation method according to claim 4, characterized in that: The total weight of the reactants mentioned in step (1) accounts for 12-18 wt% of the total weight of the solution formed by the reactants and distilled water.

6. The preparation method according to claim 2, characterized in that: The pH of the solution is adjusted to 5-9 as described in step (1).

7. The preparation method according to claim 6, characterized in that: The solution pH is adjusted to 8 as described in step (1).

8. The preparation method according to claim 2, characterized in that: The stirring speed mentioned in step (1) is 360-500 r / min.

9. The preparation method according to claim 2, characterized in that: The temperature for heating in step (2) is 40-80℃.

10. The preparation method according to claim 9, characterized in that: The temperature for heating in step (2) is 50-60℃.

11. The preparation method according to claim 2, characterized in that: The reaction time described in step (2) is 3.5-4.5 h.

12. The preparation method according to claim 2, characterized in that: The mixture in step (1) also contains an initiator, which is azobisisobutyrazoline hydrochloride, and the amount of initiator added is 0.05-0.50 wt% of the total weight of the reactants.

13. The application of the anti-high-pressure brine immersion filtration reducer according to claim 1 or the anti-high-pressure brine immersion filtration reducer prepared by any one of claims 2-12 in the preparation of drilling fluid.

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