A polymer, its preparation and use

Abstract

The application discloses a polymer and a preparation method and application thereof. The polymer comprises monomer A, monomer B and monomer C, the monomer A is 2-acrylamide-2-methylpropanesulfonic acid, the monomer B is acryloyloxyethyl trimethyl ammonium chloride, and the monomer C is selected from monomers containing polyethylene glycol and alkyl structures in side chains. The polymer can improve the high-temperature and salt resistance of the fluid loss additive.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil exploration and development, and particularly relates to a polymer, a preparation method and application thereof. BACKGROUND

[0002] With the drilling target gradually turning to deep strata, the probability of drilling into ultra-high temperature and high pressure strata increases during drilling in deep strata. In the United States, the North Sea and other regions, the bottom hole temperature is often higher than 200℃, and the maximum bottom hole pressure is higher than 110MPa; in the Yingqiong Basin of the South China Sea, the geothermal gradient is high, the formation pressure is abnormally high, and the maximum drilling bottom hole temperature reaches 249℃. Under the condition of ultra-high temperature, the performance of the drilling fluid deteriorates, and the decline of the filtration and rheological properties is particularly prominent, resulting in the phenomena of mud cake thickening, increased filtration, and difficult to maintain viscosity. If salt and gypsum layers, high-temperature salt water layers are drilled, the above problems will be further intensified, which is easy to cause a series of downhole complex accidents and brings great risk to the safety drilling of deep and ultra-deep wells. Therefore, it is necessary to study a high-temperature and salt-resistant fluid loss additive.

[0003] At present, the high-temperature and salt-resistant fluid loss additive is mainly sulfonate polymer, and a monomer containing a sulfonate group is polymerized with other functional monomers. Patent CN105733524A discloses a high-temperature and salt-resistant fluid loss additive and a preparation method thereof, which provides a fluid loss additive polymerized from a sulfonate monomer 2-acrylamide-2-methyl-propane sulfonic acid, acrylamide, sodium styrene sulfonate and maleic anhydride. Patent CN104263329B discloses a high-temperature and salt-resistant fluid loss additive for drilling fluid and a preparation method thereof, which provides a polymer formed by emulsion polymerization of acrylamide, 2-acrylamide-2-methyl-propane sulfonic acid and itaconic acid. Patent CN102559156B discloses a high-temperature and high-salt fluid loss additive for drilling fluid and a preparation method thereof, which provides a fluid loss additive copolymerized from acrylamide, acrylic acid and alkyl sulfonate containing acryloyloxy groups. The above polymers have good fluid loss characteristics under high temperature and high salt conditions. The literature "Development of DMAA / AMPS / DMDAAC / NVP Quaternary Copolymer Temperature and Salt Tolerant Drilling Fluid Fluid Loss Additive" (Oilfield Chemistry, 34(1), 2017) uses N,N-dimethyl acrylamide, dimethyl diallyl ammonium chloride, N-vinyl pyrrolidone and 2-acrylamide-2-methyl propane sulfonic acid to copolymerize a temperature and salt resistant fluid loss additive, which is expected to be used in high temperature and high salt strata.

[0004] The polymer in the above patent or document mainly considers the water-solubility, steric hindrance effect and rigidity effect of the cyclic structure monomer in the molecular structure design, thereby maintaining the stability of the molecular structure and playing the temperature resistance role, and then some cationic monomers are introduced to play a certain inhibition and synergistic fluid loss reduction effect. Although the polymer fluid loss reducer has a certain fluid loss reduction effect under high temperature and high salt conditions, it is limited to low salt ions such as sodium chloride brine conditions, and does not consider the fluid loss reduction effect under high salt ions such as calcium chloride and magnesium chloride conditions, and does not make special structure design for high salt ions.

[0005] In summary, the fluid loss reducer in the prior art is affected by the high temperature and salt conditions, and a fluid loss reducer capable of improving the high temperature resistance and salt resistance is needed. SUMMARY

[0006] In view of the above problems in the prior art, the present application provides a polymer, which selects specific functional monomers, can maintain the fluid loss reduction performance under high temperature, and has good fluid loss reduction effect under low salt ions and high salt ions, and can be used for preparing a high temperature resistant and salt resistant drilling fluid fluid loss reducer, and can significantly reduce the fluid loss of the drilling fluid. The present application also provides a preparation method and application of the polymer.

[0007] The present application provides a polymer, which is a polymer comprising monomer A, monomer B and monomer C, the monomer A is 2-acrylamide-2-methylpropane sulfonic acid (AMPS); the monomer B is acryloyloxyethyl trimethyl ammonium chloride (DAC); and the monomer C is selected from a monomer containing polyethylene glycol and alkyl structure in the side chain.

[0008] The copolymer side chain contains a certain length of oxyethylene segment, which can effectively resist high salt ion pollution and improve the high salt resistance of the whole molecule through coordination with metal cations; the alkyl hydrophobic group at the end of the oxyethylene segment can play a high temperature solubilization role and improve the high temperature resistance of the molecule. The sulfonic anion group in the side chain provides good adsorption and hydration for the polymer, so that the molecule is more likely to form a hydration film on the clay surface, fix a large amount of free water, reduce the damage of free water to clay, and maintain the stability of the drilling fluid system. The cationic group in the side chain can interact with the clay surface with negative charge in the form of electrostatic force, and can inhibit the dispersion of clay.

[0009] According to some embodiments of the present application, the structural formula of the polymer is:

[0010]

[0011] According to some embodiments of the present application, R is selected from C1-C 20Alkyl groups, with or without substituents, C1-C 20 The alkenyl group.

[0012] According to some embodiments of the present invention, n is an integer from 1 to 100.

[0013] According to some embodiments of the present invention, x:y:z = 2-7:1-5:1, more preferably x:y:z = 2-4.5:1-3:1. The x:y:z ratio can be the molar ratio of monomer A, monomer B, and monomer C.

[0014] According to some embodiments of the present invention, the molecular weight of the polymer of the present invention is selected using conventional molecular weight methods.

[0015] According to some implementations of the invention, x, y, and z are each independently an integer from 1 to 50.

[0016] According to some embodiments of the present invention, the substituent is selected from one or more of hydroxyl, ketone and heteroatom groups.

[0017] According to some embodiments of the present invention, n = 17, 22 or 42.

[0018] According to some embodiments of the present invention, R = alkyl or alkenyl, preferably one or more of methyl, ethyl, propyl, butyl, vinyl and propylene.

[0019] According to some embodiments of the present invention, the polymer is copolymerized from materials including monomer A, monomer B and monomer C in the presence of an initiator and a solvent.

[0020] According to some embodiments of the present invention, the monomer C is a polyethylene glycol methacrylate compound (PEG-MA).

[0021] According to some embodiments of the present invention, the monomer C is one or more of (methyl)polyethylene glycol methacrylate, (ethyl)polyethylene glycol methacrylate, (vinyl)polyethylene glycol methacrylate, and (propylene)polyethylene glycol methacrylate.

[0022] According to some embodiments of the present invention, the monomer C is (methyl)polyethylene glycol methacrylate.

[0023] According to some embodiments of the present invention, the initiator is an azo initiator, more preferably azobisisobutyronitrile, and / or azobisisobutyramidine hydrochloride.

[0024] According to some embodiments of the present invention, the total amount of monomer A, monomer B and monomer C accounts for 10-20% by weight of the total amount of monomers and solvents, more preferably 12-17% by weight.

[0025] According to some embodiments of the present application, the initiator accounts for 0.1-0.5% by weight of the total amount of monomer A, monomer B and monomer C, preferably 0.2-0.4% by weight.

[0026] According to some embodiments of the present application, the weight ratio of monomer A: monomer B: monomer C: initiator = 2-10.8: 1.5-7.6: 1.6-10: 0.01-0.1.

[0027] The second aspect of the present application provides a method for preparing a polymer, comprising the following steps:

[0028] A. mixing a solution containing monomer A, a solution containing monomer B and monomer C and heating to obtain a first solution;

[0029] B. mixing the first solution with an initiator and reacting, drying.

[0030] According to some embodiments of the present application, the solution is an aqueous solution.

[0031] According to some specific embodiments of the present application, in step A, monomer A is first dissolved in water, then monomer B is dissolved in water, and the aqueous solution of monomer B is added to the aqueous solution of monomer A, and then monomer C is dissolved in the solution containing monomer A and monomer B.

[0032] According to some embodiments of the present application, the heating conditions include heating to 40-60℃, preferably 50℃.

[0033] According to some embodiments of the present application, the specific embodiments of step B can be: flushing nitrogen into the container, and adding the initiator to the first solution.

[0034] According to some embodiments of the present application, the reaction conditions include a temperature of 60-90℃, preferably 65-80℃, and a time of 5-7 hours, more preferably 6 hours.

[0035] According to some embodiments of the present application, after the reaction is completed, the product is cooled to room temperature.

[0036] According to some embodiments of the present application, the drying conditions include a temperature of 100-110℃, preferably 105℃, and a time of 10-20 hours, preferably 16 hours.

[0037] According to some embodiments of the present application, after drying is completed, crushing is performed to obtain a fine and uniform powder of the fluid loss additive.

[0038] The third aspect of the present application provides the use of the above-mentioned polymer and the polymer prepared by the above-mentioned method in the field of preparing fluid loss additives.

[0039] Compared with the prior art, the present application comprises the following beneficial effects:

[0040] (1) The polymer provided by the present application has excellent fluid loss performance in a composite brine containing 4% by weight of sodium chloride, 0.5% by weight of calcium chloride and 0.7% by weight of magnesium chloride, and can achieve good salt resistance under the conditions of high-valence salt and low-valence salt.

[0041] (2) The polymer provided by the present application has good high-temperature resistance, and the system can resist a temperature of 200°C.

[0042] (3) The polymer provided by the present application and the polymer obtained by the preparation method provided by the present application can be applied to the preparation of fluid loss agents, and can significantly enhance the temperature resistance and salt resistance of the fluid loss agents. DETAILED DESCRIPTION

[0043] In order to make the present application easier to understand, the present application will be described in detail below in combination with embodiments, which are only illustrative and do not limit the application range of the present application.

[0044] The test method for the fluid loss amount used in the present application is as follows:

[0045] Preparation of the composite brine-based slurry: 400 mL of tap water is added to a high-speed stirring cup, and 16 g of sodium chloride, 2.0 g of calcium chloride, 2.8 g of magnesium chloride and 3.6 g of sodium bicarbonate are sequentially added under the stirring speed of 10,000 rpm, and after complete dissolution, 60 g of drilling fluid test soil is added, stirred uniformly, and sealed and left to stand for 24 hours to obtain the composite brine-based slurry.

[0046] Preparation of the composite brine test slurry: 3% by weight of the sample is added to the composite brine-based slurry under the stirring speed of 10,000 rpm, and after uniform stirring, the sample is placed under the condition of 180°C for heat rolling aging for 16 hours, and the fluid loss performance of the test slurry is tested. Specifically, the pressure filtration loss amount at room temperature or the high-temperature and high-pressure filtration loss amount is determined according to the provisions of GB / T 16783.1.

[0047] The materials used in the present application are all commercially available, and are specifically shown in Table 1.

[0048] Table 1: Materials and manufacturers

[0049]

[0050]

[0051] Example 1

[0052] Preparation of the polymer.

[0053] (1) 20.7 g of AMPS is dissolved in 200 mL of water, and stirred uniformly.

[0054] (2) Dissolve 19.3 g of DAC in 200 mL of water and add to the solution of step (1) and stir well.

[0055] (3) Add 42.4 g of polyethylene glycol methacrylate PEG-MA (n = 17, R = methyl) to the solution of step (2), add 150 mL of water, heat to 50°C and stir well.

[0056] (4) Bubble nitrogen into the vessel of step (3), add 0.16 g of azobisisobutyronitrile to the solution of step (3) and stir while heating to 60°C. After 6 hours of reaction, cool to room temperature.

[0057] (5) Dry the liquid product of step (4) at 105°C, pulverize and obtain a fine, uniform powder of the polymer.

[0058] Example 2

[0059] Prepare the polymer.

[0060] (1) Dissolve 31.5 g of AMPS in 300 mL of water and stir well.

[0061] (2) Dissolve 19.3 g of DAC in 200 mL of water and add to the solution of step (1) and stir well.

[0062] (3) Add 54.1 g of PEG-MA (n = 22, R = ethyl) to the solution of step (2), add 150 mL of water, heat to 50°C and stir well.

[0063] (4) Bubble nitrogen into the vessel of step (3), add 0.31 g of azobisisobutyronitrile to the solution of step (3) and stir while heating to 70°C. After 6 hours of reaction, cool to room temperature.

[0064] (5) Dry the liquid product of step (4) at 105°C, pulverize and obtain a fine, uniform powder of the polymer.

[0065] Example 3

[0066] Prepare the polymer.

[0067] (1) Dissolve 41.4 g of AMPS in 400 mL of water and stir well.

[0068] (2) Dissolve 28.9 g of DAC in 300 mL of water and add to the solution of step (1) and stir well.

[0069] (3) Add 98.1 g of PEG-MA (n = 42, R = ethyl) to the solution of step (2), add 420 mL of water, heat to 50°C and stir well.

[0070] (4) The container of step (3) was filled with nitrogen gas, and 0.50 g of azobisisobutyronitrile was added to the solution of step (3) and stirred and heated to 80°C. After 6 hours of reaction, it was cooled to room temperature.

[0071] (5) The liquid product of (4) was dried at 105°C, and then pulverized to obtain a fine and uniform powder of the polymer.

[0072] Example 4

[0073] The polymer was prepared.

[0074] (1) 41.4 g of AMPS was dissolved in 400 mL of water and stirred to homogeneity.

[0075] (2) 28.9 g of DAC was dissolved in 300 mL of water and added to the solution of step (1) and stirred to homogeneity.

[0076] (3) 54.1 g of PEG-MA (n = 22, R = ethyl) was added to the solution of step (2) and 130 mL of water was added and heated to 50°C and stirred to homogeneity.

[0077] (4) The container of step (3) was filled with nitrogen gas, and 0.49 g of azobisisobutyramidine hydrochloride was added to the solution of step (3) and stirred and heated to 75°C. After 6 hours of reaction, it was cooled to room temperature.

[0078] (5) The liquid product of (4) was dried at 105°C, and then pulverized to obtain a fine and uniform powder of the polymer.

[0079] Example 5

[0080] The polymer was prepared.

[0081] The same materials and methods as in Example 2 were used, except that the molar ratio of the monomers was x:y:z = 6:4:1.

[0082] Examples 6-11

[0083] The polymer was prepared.

[0084] The same materials and methods as in Example 2 were used, except that the molar ratio of the monomers was different, and the molar ratio of the monomers is shown in Tables 2 and 3.

[0085] Comparative Example 1

[0086] The polymer was prepared.

[0087] The same materials and methods as in Example 2 were used, except that monomer C was not added and the molar ratio of the monomers was x:y = 4:3.

[0088] Comparative Example 2

[0089] The polymer was prepared.

[0090] The substances and methods used were the same as in Example 2, except that no monomer A was added and the monomer molar ratio was y:z = 2:1.

[0091] Comparative Example 3

[0092] The polymer was prepared.

[0093] The substances and methods used were the same as in Example 2, except that no monomer B was added and the monomer molar ratio was x:z = 3:1.

[0094] Experimental Example 1

[0095] Effect of monomer PEG-MA addition amount.

[0096] Comparative Example 1 and Examples 1-8 were subjected to fluid loss testing in a composite saltwater base slurry, and the specific addition amounts and testing results are shown in Table 2.

[0097] Table 2 Testing results of comparative example samples in a composite saltwater base slurry

[0098]

[0099]

[0100] According to the testing results in Table 2, the fluid loss after aging of Examples 1-4 was significantly less than the fluid loss of the composite saltwater base slurry and Comparative Example 1, indicating that adding PEG-MA to the molecular structure of the polymer can significantly improve the fluid loss reduction performance of the polymer. Moreover, too high or too low an addition amount of PEG-MA will affect the fluid loss reduction performance, and the fluid loss reduction performance of Example 2 is best.

[0101] Experimental Example 2

[0102] Effect of AMPS and DAC ratio.

[0103] Examples 2, 5, and Comparative Example 2 were subjected to fluid loss testing in a composite saltwater base slurry, and the specific addition amounts and testing results are shown in Table 3.

[0104] Table 3 Testing results of comparative example samples in a composite saltwater base slurry

[0105] Sample Monomer mole ratio MIL after aging, mL Composite brine-based mud - 166 Comparative Example 2 y:z = 2:1 120 Comparative Example 3 x:z = 3:1 77 Example 9 x:y:z = 1:3:1 26.2 Example 2 x:y:z = 3:2:1 11.8 Example 10 x:y:z = 4:2:1 18.8 Example 11 x:y:z = 7:2:1 23.4

[0106] According to the test results in Table 3, the aged medium-pressure filtration loss of Examples 2 and 9-11 is obviously smaller than that of the composite salt water base slurry and the filtration loss of Comparative Examples 2 and 3, indicating that the addition of AMPS and DAC in the molecular structure of the polymer can significantly improve the filtration reduction performance of the polymer, and the ratio between AMPS and DAC will affect the filtration reduction performance, and the filtration reduction performance of Example 2 is the best.

[0107] Experimental Example 3

[0108] Test in saturated salt water.

[0109] Preparation of saturated salt water base slurry: 400 mL tap water was added to a high-speed stirring cup, 0.48 g of anhydrous sodium bicarbonate, 8 g of drilling fluid test soil were added in sequence under the stirring speed of 10,000 rpm, and stirred for 2 hours, 12 g of sulfonated lignite was added after being sealed and standing for 24 hours, stirred for 5 minutes, and then 105 sodium chloride was added, stirred for 20 minutes, to obtain the saturated salt water base slurry.

[0110] Preparation and test of saturated salt water test slurry: 5% by weight of the sample was added to the saturated salt water slurry under the stirring speed of 10,000 rpm, and after being stirred uniformly, it was placed in a hot rolling aging condition at 200°C for 16 hours, and the performance of the test slurry was tested. For example, the polymer obtained in Example 2 was used as a sample, and Dristemp, a representative high-temperature and salt-resistant filtration reducer abroad, was used as a comparative sample, and the test results are shown in Table 4.

[0111] Table 4 Test results in saturated salt water base slurry

[0112] Sample Apparent viscosity, mPa-s MIL after aging, mL Saturated brine-based mud 4 187 Example 2 40 5.6 Dristemp 38 6.4

[0113] According to the results in Table 4, the polymer provided by the application has good filtration reduction performance in saturated salt water base slurry, which is better than the common high-temperature and salt-resistant filtration reducer on the market.

[0114] Experimental Example 4

[0115] Test in composite salt water.

[0116] For example, the sample of Example 2 was used as a sample, Dristemp and DSP-2, a representative temperature-resistant and salt-resistant sulfonate filtration reducer in China, were used as comparative samples, and the performance in the composite salt water base slurry was tested, and the test results are shown in Table 5.

[0117] Table 5 Test results in composite salt water base slurry

[0118] Sample Apparent viscosity, mPa-s MIL after aging, mL Composite brine-based mud 6 166 Example 2 40 11.8 Dristemp 38 12.8 DSP-2 18 24

[0119] According to the test results in Table 5, the filtration reduction performance of the polymer provided by the application in the composite salt water is better than other filtration reducers on the market.

[0120] Experimental Example 5

[0121] Testing in water-based drilling fluids.

[0122] Preparation of calcium-based slurry: Add 400mL of tap water to a high-speed stirring cup, and add 0.48g of anhydrous sodium bicarbonate, 16g of sodium chloride, and 2.0g of calcium chloride in sequence while stirring at 10000 rpm. After complete dissolution, add 8g of drilling fluid test soil and stir evenly. Seal and let stand for 24 hours to obtain calcium-based slurry.

[0123] The formulation of the composite brine-based drilling fluid is as follows: In 400 mL of fresh water-based slurry, under stirring speed of 10,000 rpm, add sequentially 0.4 wt% sodium hydroxide, 1 wt% high-temperature resistant polymer filtration reducer, 3 wt% sulfonated lignite, 4 wt% sulfonated phenolic resin type II, 3 wt% sulfonated lignite resin, 0.5 wt% lubricant, 2 wt% high-temperature resistant anti-collapse agent, and 2 wt% high-density dispersant. Finally, add barite to prepare a solution with a density of 2.1 g / cm³. 3 Composite salt drilling fluid.

[0124] Tests: 1.5% by weight of the polymer prepared in Example 2 was added to the composite brine-based drilling fluid at a stirring speed of 10,000 rpm. After stirring evenly, the fluid was subjected to hot rolling aging at 200°C for 16 hours. The rheological properties of the slurry, medium-pressure filtration loss, and high-temperature, high-pressure filtration loss at 150°C were tested. The polymer prepared in Example 2 was added to the composite brine-based drilling fluid as a sample, with no sample added serving as a control. The test results are shown in Table 6.

[0125] Table 6. Test results in composite salt-based drilling fluids.

[0126]

[0127] According to the test results in Table 6, the polymer prepared by the present invention can improve the filtration loss reduction performance of high-density drilling fluid containing high-valence salt ions under high temperature and high pressure conditions, and the apparent viscosity is within a suitable range, which will not affect the normal use of the drilling fluid.

[0128] In summary, the polymer provided by this invention exhibits excellent resistance to high temperatures and low- and high-valence salts under various environments, thereby improving the filtration loss reduction performance of drilling fluids.

[0129] The above description is merely a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, based on the technical teachings provided by the present invention and as common knowledge in the field, other equivalent modifications and improvements can be made, and these should also be considered within the scope of protection of the present invention.

Claims

1. A polymer for use as a fluid loss additive, characterized in that, The monomers of the polymer include monomer A, monomer B and monomer C, the monomer A is 2-acrylamido-2-methylpropane sulfonic acid; the monomer B is acryloyloxyethyl trimethyl ammonium chloride; the monomer C is selected from monomers containing polyethylene glycol and alkyl structure in side chain; The polymer has the following structural formula: Wherein, R is selected from C1-C with or without substituents. 20 Alkyl groups, with or without substituents, C1-C 20 The alkenyl group; n is an integer from 1 to 100, and the molar ratio of x:y:z is 2.5-3 : 1-3 :

1.

2. The polymer of claim 1, wherein, The substituent group is selected from one or more of hydroxyl, ketone and heteroatom.

3. The polymer according to claim 1 or 2, characterized in that, x, y and z are each independently an integer of 1-50; and / or, n = 17, 22 or 42; and / or, R = alkyl or alkenyl.

4. The polymer of claim 3, wherein R is one or more of methyl, ethyl, propyl, butyl, vinyl and propenyl.

5. The polymer according to claim 1 or 2, characterized in that, The polymer is copolymerized from a material including monomer A, monomer B and monomer C in the presence of an initiator and a solvent.

6. The polymer of claim 5, wherein, The monomer C is a polyethylene glycol methacrylate compound.

7. The polymer of claim 6, wherein, The monomer C is one or more of (methyl) polyethylene glycol methacrylate, (ethyl) polyethylene glycol methacrylate, (vinyl) polyethylene glycol methacrylate, (propenyl) polyethylene glycol methacrylate.

8. The polymer of claim 7, wherein, The monomer C is (methyl) polyethylene glycol methacrylate.

9. The polymer of claim 5, wherein, The initiator is an azo initiator.

10. The polymer of claim 8, wherein, The initiator is azobisisobutyronitrile, and / or azobisisobutyramidine hydrochloride.

11. The polymer of claim 5, wherein, The total amount of the monomer A, monomer B and monomer C accounts for 10-20% by weight of the total amount of monomers and solvent; and / or, The initiator accounts for 0.1-0.5% by weight of the total amount of the monomer A, monomer B and monomer C; and / or The weight ratio of monomer A: monomer B: monomer C: initiator = 2-10.8 : 1.5-7.6 : 1.6-10 : 0.01-0.

1.

12. The polymer of claim 11, wherein, The total amount of the monomer A, monomer B and monomer C accounts for 12-17% by weight of the total amount of monomers and solvent; and / or, The initiator accounts for 0.2-0.4% by weight of the total amount of the monomer A, monomer B and monomer C.

13. A process for the preparation of the polymer of claim 1 or 2, characterized in that, The method comprises the following steps: A, mixing and heating a solution containing monomer A, a solution containing monomer B and monomer C to obtain a first solution; B, mixing and reacting the first solution with an initiator, and drying.

14. The method of claim 13, wherein, The heating condition includes heating to 40-60℃.

15. The method of claim 14, wherein, The heating condition includes heating to 50℃.

16. The method according to any one of claims 13-15, characterized by, The reaction condition includes a temperature of 60-90℃ and a time of 5-7 hours.

17. The method of claim 16, wherein, The reaction condition includes a temperature of 65-80℃ and a time of 6 hours.

18. The method of any one of claims 13-15, wherein, The drying condition includes a temperature of 100-110℃ and a time of 10-20 hours.

19. The method of claim 18, wherein, The drying condition includes a temperature of 105℃ and a time of 16 hours.

20. Use of the polymer of any one of claims 1-12 and the polymer prepared by the method of any one of claims 13-19 in the field of preparing a fluid loss additive.

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