A high-temperature and salt-resistant composite polymer viscosifier and its preparation method

Abstract

The present invention belongs to the technical field of petrochemical engineering, and particularly relates to a high-temperature and salt-resistant composite polymer viscosifier and a preparation method thereof. The high-temperature and salt-resistant composite polymer viscosifier is prepared by the following method: (1) Using acrylamide, N-isopropylmethacrylamide, hydroxybutyl acrylate and methoxypolyethylene glycol acrylate as polymerization monomers, and ammonium persulfate as an initiator, heating to 70 °C in an aqueous solution under nitrogen protection and reacting for 3 to 8 hours to obtain a quaternary copolymer; (2) Mixing the obtained quaternary copolymer with hydroxyethyl cellulose in an aqueous solution to obtain a composite polymer viscosifier solution. The quaternary copolymer and hydroxyethyl cellulose of the present invention have a synergistic thickening effect, and the prepared composite polymer viscosifier solution can achieve good high-temperature and salt-resistant properties. The composite polymer solution has potential application value in the field of high-temperature and salt-resistant oil displacement agents.

Description

Technical Field

[0001] The present invention belongs to the technical field of petrochemical engineering, and particularly relates to a high-temperature and salt-resistant composite polymer thickener and a preparation method thereof. Background Art

[0002] Hydroxyethyl cellulose is used as an oil displacement agent in oil fields, and has advantages such as good thickening effect, strong shear resistance, and less environmental pollution. However, the effect of using it alone is not ideal. Although hydroxyethyl cellulose has certain high-temperature and salt-resistant properties, its cost is high and the dosage is large, so the economic benefit of using it as an oil displacement agent in oil fields is not ideal. Researchers compounded the ionic polymer sodium carboxymethyl cellulose with hydroxyethyl cellulose to reduce costs, but the salt resistance is not good. Compared with ionic polymers, non-ionic polymers have the advantage of good salt resistance. Using the principle of intermolecular compounding between macromolecules, compounding hydroxyethyl cellulose with a non-ionic copolymer of polyacrylamide with lower cost may produce a synergistic thickening effect and maintain good salt resistance, so as to reduce the dosage of hydroxyethyl cellulose while ensuring the use effect, reduce the cost of the thickener, and increase economic benefits. However, the influence of the structural composition of the non-ionic copolymer of polyacrylamide on the properties of the composite polymer solution is still not clear, and the technical problems of how to prepare a non-ionic copolymer of polyacrylamide that can have a good synergistic thickening effect with hydroxyethyl cellulose and how to prepare a composite polymer solution with good salt resistance still need to be solved. Summary of the Invention

[0003] One of the purposes of the present invention is to provide a composite polymer solution, which has a synergistic thickening effect and good high-temperature and salt-resistant properties.

[0004] To achieve this purpose, the present invention is realized by adopting the following technical solutions: a composite polymer thickener solution is prepared by mixing a quaternary copolymer and hydroxyethyl cellulose in an aqueous solution.

[0005] The mass ratio of the quaternary copolymer to hydroxyethyl cellulose is 1-2:1; the concentration of the composite polymer thickener solution is 1.5%-5%.

[0006] The structural general formula of the quaternary copolymer is shown in Formula I.

[0007]

[0008] Among them, y:w:z:x is 2-3:0.1-0.3:1:0.1-0.2, and n = 9.

[0009] The preparation reaction formula of the compound of Formula I is shown as follows.

[0010]

[0011] The preparation method of the compound of formula I is as follows: Dissolve acrylamide, N-isopropylmethacrylamide, hydroxybutyl acrylate and methoxypolyethylene glycol acrylate in ultrapure water, add ammonium persulfate, stir and dissolve at room temperature, pass nitrogen to remove the air in the reaction system, and heat to initiate the polymerization reaction under nitrogen protection. After the reaction is completed, cool the reaction solution to room temperature, dialyze with ultrapure water, and freeze-dry to obtain the quaternary copolymer.

[0012] Among them, the molar ratio of acrylamide, N-isopropylmethacrylamide, hydroxybutyl acrylate and methoxypolyethylene glycol acrylate is 24-32:1-2:10:2.

[0013] The feeding amount of ammonium persulfate is 0.08-0.2% of the total feeding mass of the polymerization monomers.

[0014] The molecular weight of methoxypolyethylene glycol acrylate is 480 Da.

[0015] The heating reaction temperature is 70 °C and the reaction time is 3-8 hours.

[0016] The prepared composite polymer viscosifier is used in the field of high-temperature and salt-tolerant oil displacement agents.

[0017] The advantages of the present invention are as follows: In the composite polymer solution provided by the present invention, the quaternary copolymer and hydroxyethyl cellulose have a synergistic thickening effect, and the composite polymer solution has good high-temperature and salt-tolerant properties. Description of the Drawings

[0018] Figure 1 1H NMR spectrum of the copolymer prepared in Example 1 in deuterated dimethyl sulfoxide.

[0019] Figure 2 1H NMR spectrum of the copolymer prepared in Example 2 in deuterated dimethyl sulfoxide.

[0020] Figure 3 1H NMR spectrum of the copolymer prepared in Example 3 in deuterated dimethyl sulfoxide.

[0021] Figure 4 1H NMR spectrum of the copolymer prepared in Example 4 in deuterated dimethyl sulfoxide.

[0022] Figure 5 1H NMR spectrum of the copolymer prepared in Example 8 in deuterated water.

[0023] Figure 6 1H NMR spectrum of the copolymer prepared in Example 9 in deuterated dimethyl sulfoxide.

[0024] Figure 7 1H NMR spectrum of the copolymer prepared in Example 10 in deuterated dimethyl sulfoxide.

[0025] Figure 8 1H NMR spectrum of the copolymer prepared in Example 11 in deuterated water. Detailed implementation manners

[0026] The present invention will be further described below in conjunction with specific embodiments.

[0027] Preparation of poly(acrylamide-N-isopropylmethacrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate) (2.06:0.42:1:0.17) in Example 1

[0028] 1.065 g of acrylamide, 0.318 g of N-isopropylmethacrylamide, 0.9 g of hydroxybutyl acrylate and 0.6 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water, stirred and dissolved at room temperature, 3 mg of ammonium persulfate was added, and nitrogen was passed for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring conditions, the reaction system was heated to 70 °C and reacted for 8 hours. Then the reaction solution was cooled to room temperature, dialyzed with ultrapure water for 3 days (molecular weight cut-off 8000 - 14000 Da), and freeze-dried to obtain the quaternary copolymer.

[0029] The prepared copolymer was characterized by 1H NMR, as Figure 1 shown. By the integral ratio of the amide hydrogen signal of acrylamide (chemical shift 6.5 - 7.5), the methyl hydrogen signal of N-isopropylmethacrylamide (chemical shift 1.0), the hydroxyl hydrogen signal of hydroxybutyl acrylate (chemical shift 4.5) and the polyethylene glycol hydrogen signal of methoxypolyethylene glycol acrylate (chemical shift 3.5), the molar ratio of the polymerization units acrylamide, N-isopropylmethacrylamide, hydroxybutyl acrylate and methoxypolyethylene glycol acrylate in the copolymer was calculated to be 2.06:0.42:1:0.17. The number-average molecular weight of the copolymer was measured to be 221887 by gel permeation chromatography, and the polydispersity index was 1.9.

[0030] Preparation of poly(acrylamide-N-isopropylmethacrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate) (1.88:0.25:1:0.15) in Example 2

[0031] 1.065 g of acrylamide, 0.159 g of N-isopropylmethacrylamide, 0.9 g of hydroxybutyl acrylate, and 0.6 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water and stirred at room temperature until dissolved. 3 mg of ammonium persulfate was added, and nitrogen gas was bubbled through the solution for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring, the reaction system was heated to 70 °C and reacted for 8 hours. Then the reaction solution was cooled to room temperature and dialyzed against ultrapure water for 3 days (molecular weight cut-off 8000 - 14000 Da), and freeze-dried to obtain the quaternary copolymer.

[0032] The prepared copolymer was characterized by nuclear magnetic resonance hydrogen spectroscopy, as Figure 2 shown. The molar ratio of the polymerization units acrylamide, N-isopropylmethacrylamide, hydroxybutyl acrylate, and methoxypolyethylene glycol acrylate in the copolymer was calculated to be 1.88:0.25:1:0.15 from the integral ratios of the amide hydrogen signal of acrylamide (chemical shift 6.5 - 7.5), the methyl hydrogen signal of N-isopropylmethacrylamide (chemical shift 1.0), the hydroxyl hydrogen signal of hydroxybutyl acrylate (chemical shift 4.5), and the polyethylene glycol hydrogen signal of methoxypolyethylene glycol acrylate (chemical shift 3.5). The number-average molecular weight of the copolymer was measured to be 211754 by gel permeation chromatography, and the polydispersity index was 1.7.

[0033] Example 3 Preparation of poly(acrylamide-N-isopropylmethacrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate) (2.03:0.11:1:0.17)

[0034] 1.065 g of acrylamide, 0.08 g of N-isopropylmethacrylamide, 0.9 g of hydroxybutyl acrylate, and 0.6 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water and stirred at room temperature until dissolved. 3 mg of ammonium persulfate was added, and nitrogen gas was bubbled through the solution for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring, the reaction system was heated to 70 °C and reacted for 3 hours. Then the reaction solution was cooled to room temperature and dialyzed against ultrapure water for 3 days (molecular weight cut-off 8000 - 14000 Da), and freeze-dried to obtain the quaternary copolymer.

[0035] The prepared copolymer was characterized by nuclear magnetic resonance hydrogen spectroscopy, as Figure 3As shown. By the integral ratio of the amide hydrogen signal (chemical shift 6.5 - 7.5) of acrylamide, the methyl hydrogen signal (chemical shift 1.0) of N-isopropylmethacrylamide, the hydroxyl hydrogen signal (chemical shift 4.5) of hydroxybutyl acrylate, and the polyethylene glycol hydrogen signal (chemical shift 3.5) of methoxypolyethylene glycol acrylate, the molar ratio of the polymerization units acrylamide, N-isopropylmethacrylamide, hydroxybutyl acrylate, and methoxypolyethylene glycol acrylate in the copolymer was calculated to be 2.03:0.11:1:0.17. The number-average molecular weight of the copolymer measured by gel permeation chromatography was 204438, and the polydispersity index was 1.6.

[0036] Example 4 Preparation of poly(acrylamide-N-isopropylmethacrylamide-hydroxybutyl acrylate)

[0037] (2.17:0.14:1)

[0038] 1.065 g of acrylamide, 0.08 g of N-isopropylmethacrylamide, and 0.9 g of hydroxybutyl acrylate were added to 50 mL of ultrapure water, stirred and dissolved at room temperature, 3 mg of ammonium persulfate was added, and nitrogen was bubbled for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring, the reaction system was heated to 70 °C and reacted for 3 hours. Then the reaction solution was cooled to room temperature and dialyzed with ultrapure water for 3 days (molecular weight cut-off 8000 - 14000 Da), and freeze-dried to obtain the terpolymer.

[0039] The prepared copolymer was characterized by nuclear magnetic resonance hydrogen spectroscopy, as Figure 4 shown. By the integral ratio of the amide hydrogen signal (chemical shift 6.5 - 7.5) of acrylamide, the methyl hydrogen signal (chemical shift 1.0) of N-isopropylmethacrylamide, and the hydroxyl hydrogen signal (chemical shift 4.5) of hydroxybutyl acrylate, the molar ratio of the polymerization units acrylamide, N-isopropylmethacrylamide, and hydroxybutyl acrylate in the copolymer was calculated to be 2.17:0.14:1. The number-average molecular weight of the copolymer measured by gel permeation chromatography was 225749, and the polydispersity index was 1.5.

[0040] Example 5 Preparation of poly(acrylamide-N-isopropylmethacrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate)

[0041] 1.065 g of acrylamide, 0.08 g of N-isopropylmethacrylamide, 0.9 g of hydroxybutyl acrylate, and 1.2 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water, stirred and dissolved at room temperature, 3 mg of ammonium persulfate was added, and nitrogen was bubbled for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring, the reaction system was heated to 70 °C and reacted for 1 hour, and gelation occurred.

[0042] Preparation of Poly(acrylamide - hydroxybutyl acrylate - methoxypolyethylene glycol acrylate) in Example 6

[0043] 1.065 g of acrylamide, 0.9 g of hydroxybutyl acrylate and 0.6 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water, stirred and dissolved at room temperature. 3 mg of ammonium persulfate was added, and nitrogen was passed through for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring conditions, the reaction system was heated to 70 °C and reacted for 1 hour, and gelation occurred.

[0044] Preparation of Poly(acrylamide - hydroxybutyl acrylate - methoxypolyethylene glycol acrylate) in Example 7

[0045] 1.065 g of acrylamide, 1.08 g of hydroxybutyl acrylate and 0.6 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water, stirred and dissolved at room temperature. 3 mg of ammonium persulfate was added, and nitrogen was passed through for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring conditions, the reaction system was heated to 70 °C and reacted for 2 hours, and gelation occurred.

[0046] Preparation of Poly(acrylamide - hydroxybutyl acrylate - methoxypolyethylene glycol acrylate) in Example 8

[0047] (2.23:1.40:0.18)

[0048] 1.065 g of acrylamide, 1.26 g of hydroxybutyl acrylate and 0.6 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water, stirred and dissolved at room temperature. 3 mg of ammonium persulfate was added, and nitrogen was passed through for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring conditions, the reaction system was heated to 70 °C and reacted for 8 hours. Then the reaction solution was cooled to room temperature, dialyzed against ultrapure water for 3 days (molecular weight cut-off 8000 - 14000 Da), and freeze-dried to obtain the terpolymer.

[0049] The prepared copolymer was characterized by nuclear magnetic resonance hydrogen spectrum and elemental analysis. The nuclear magnetic resonance hydrogen spectrum is as Figure 5 shown. By the integral ratio of the methylene hydrogen signal of hydroxybutyl acrylate (chemical shift 4.1) and the polyethylene glycol hydrogen signal of methoxypolyethylene glycol acrylate (chemical shift 3.6), as well as the results of elemental analysis, the molar ratio of the polymerization units acrylamide, hydroxybutyl acrylate, and methoxypolyethylene glycol acrylate in the copolymer was calculated to be 2.23:1.4:0.18. The number-average molecular weight of the copolymer measured by gel permeation chromatography was 206438 and the polydispersity index was 1.6.

[0050] Preparation of Poly(acrylamide-N-isopropylmethacrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate) (2.52:0.22:1:0.19)

[0051] 1.43 g of acrylamide, 0.16 g of N-isopropylmethacrylamide, 0.9 g of hydroxybutyl acrylate and 0.6 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water, stirred and dissolved at room temperature. 3 mg of ammonium persulfate was added, and nitrogen was bubbled through for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring, the reaction system was heated to 70 °C and reacted for 8 hours. Then the reaction solution was cooled to room temperature, dialyzed against ultrapure water for 3 days (molecular weight cut-off 8000 - 14000 Da), and freeze-dried to obtain the quaternary copolymer.

[0052] The prepared copolymer was characterized by 1H NMR, as Figure 6 shown. The molar ratio of the polymerization units acrylamide, N-isopropylmethacrylamide, hydroxybutyl acrylate and methoxypolyethylene glycol acrylate in the copolymer was calculated to be 2.52:0.22:1:0.19 from the integral ratio of the amide hydrogen signal of acrylamide (chemical shift 6.5 - 7.5), the methyl hydrogen signal of N-isopropylmethacrylamide (chemical shift 1.0), the hydroxyl hydrogen signal of hydroxybutyl acrylate (chemical shift 4.5) and the polyethylene glycol hydrogen signal of methoxypolyethylene glycol acrylate (chemical shift 3.5). The number-average molecular weight of the copolymer was measured to be 271425 by gel permeation chromatography, and the polydispersity index was 1.6.

[0053] Example 10 Preparation of Poly(acrylamide-N-isopropylmethacrylamide-hydroxybutyl acrylate)

[0054] (2.66:0.23:1)

[0055] 1.43 g of acrylamide, 0.16 g of N-isopropylmethacrylamide and 0.9 g of hydroxybutyl acrylate were added to 50 mL of ultrapure water, stirred and dissolved at room temperature. 3 mg of ammonium persulfate was added, and nitrogen was bubbled through for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring, the reaction system was heated to 70 °C and reacted for 8 hours. Then the reaction solution was cooled to room temperature, dialyzed against ultrapure water for 3 days (molecular weight cut-off 8000 - 14000 Da), and freeze-dried to obtain the ternary copolymer.

[0056] The prepared copolymer was characterized by 1H NMR, as Figure 7As shown in the figure. By the integral ratios of the amide hydrogen signal of acrylamide (chemical shift 6.5 - 7.5), the methyl hydrogen signal of N-isopropylmethacrylamide (chemical shift 1.0), and the hydroxyl hydrogen signal of hydroxybutyl acrylate (chemical shift 4.5), the molar ratio of the polymerization units acrylamide, N-isopropylmethacrylamide, and hydroxybutyl acrylate in the copolymer was calculated to be 2.66:0.23:1. The number-average molecular weight of the copolymer was measured to be 284743 by gel permeation chromatography, and the polydispersity index was 1.7.

[0057] Example 11 Preparation of Poly(acrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate)

[0058] (2.48:1.80:0.13)

[0059] 1.43 g of acrylamide, 1.62 g of hydroxybutyl acrylate, and 0.6 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water and stirred to dissolve at room temperature. 3 mg of ammonium persulfate was added, and nitrogen was bubbled through for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring, the reaction system was heated to 70 °C and reacted for 8 hours. Then the reaction solution was cooled to room temperature, dialyzed against ultrapure water for 3 days (molecular weight cut-off 8000 - 14000 Da), and freeze-dried to obtain the terpolymer.

[0060] The prepared copolymer was characterized by nuclear magnetic resonance hydrogen spectroscopy, as Figure 8 shown. By the integral ratios of the methylene hydrogen signal of hydroxybutyl acrylate (chemical shift 4.1) and the polyethylene glycol hydrogen signal of methoxypolyethylene glycol acrylate (chemical shift 3.6), as well as the results of elemental analysis, the molar ratio of the polymerization units acrylamide, hydroxybutyl acrylate, and methoxypolyethylene glycol acrylate in the copolymer was calculated to be 2.48:1.80:0.13. The number-average molecular weight of the copolymer was measured to be 253812 by gel permeation chromatography, and the polydispersity index was 1.8.

[0061] Comparative Example 1 Preparation of Poly(acrylamide-N-isopropylmethacrylamide-sodium acrylate-methoxypolyethylene glycol acrylate) (2.11:0.13:1:0.19)

[0062] 1.065 g of acrylamide, 0.08 g of N-isopropylmethacrylamide, 0.58 g of sodium acrylate, and 0.6 g of methoxypolyethylene glycol acrylate were added to 50 mL of ultrapure water and stirred to dissolve at room temperature. 3 mg of ammonium persulfate was added, and nitrogen was bubbled through for 1 hour to remove the air in the reaction system. Under nitrogen protection and stirring, the reaction system was heated to 70 °C and reacted for 3 hours. Then the reaction solution was cooled to room temperature, dialyzed against ultrapure water for 3 days (molecular weight cut-off 8000 - 14000 Da), and freeze-dried to obtain the quaternary copolymer.

[0063] Example 12 Preparation of 2% copolymer aqueous solution

[0064] Dissolve the copolymers prepared in Examples 1 - 4, 8 - 11 and Comparative Example 1 in ultrapure water to prepare aqueous solutions with a mass concentration of 2% of each copolymer respectively.

[0065] Example 13 Preparation of 2% copolymer aqueous solution containing 4% sodium chloride

[0066] Add sodium chloride to the aqueous solution of the 2% copolymer prepared in Example 12, and stir to dissolve at room temperature to prepare a 2% copolymer aqueous solution containing 4% sodium chloride.

[0067] Example 14 Preparation of 0.5% hydroxyethyl cellulose solution and 0.5% sodium carboxymethyl cellulose solution Dissolve hydroxyethyl cellulose and sodium carboxymethyl cellulose in ultrapure water respectively to prepare an aqueous solution of hydroxyethyl cellulose with a mass concentration of 0.5% and an aqueous solution of sodium carboxymethyl cellulose.

[0068] Example 15 Preparation of 1% hydroxyethyl cellulose solution and 1% sodium carboxymethyl cellulose solution

[0069] Dissolve hydroxyethyl cellulose and sodium carboxymethyl cellulose in ultrapure water respectively to prepare an aqueous solution of hydroxyethyl cellulose with a mass concentration of 1% and an aqueous solution of sodium carboxymethyl cellulose.

[0070] Example 16 Preparation of 0.5% hydroxyethyl cellulose solution containing 4% sodium chloride and 0.5% sodium carboxymethyl cellulose solution containing 4% sodium chloride

[0071] Add sodium chloride to the 0.5% hydroxyethyl cellulose aqueous solution and sodium carboxymethyl cellulose aqueous solution prepared in Example 14, and stir to dissolve at room temperature to prepare a 0.5% hydroxyethyl cellulose aqueous solution containing 4% sodium chloride and a 0.5% sodium carboxymethyl cellulose aqueous solution containing 4% sodium chloride.

[0072] Example 17 Preparation of 1% hydroxyethyl cellulose solution containing 4% sodium chloride and 1% sodium carboxymethyl cellulose solution containing 4% sodium chloride

[0073] Add sodium chloride to the 1% hydroxyethyl cellulose aqueous solution and sodium carboxymethyl cellulose aqueous solution prepared in Example 15, and stir to dissolve at room temperature to prepare a 1% hydroxyethyl cellulose aqueous solution containing 4% sodium chloride and a 1% sodium carboxymethyl cellulose aqueous solution containing 4% sodium chloride.

[0074] Example 18 Preparation of composite polymer solution containing 0.5% hydroxyethyl cellulose and 1% copolymer

[0075] The copolymers prepared in Examples 1-4 and 8-11 were respectively dissolved in ultrapure water, and then hydroxyethyl cellulose was added and stirred to dissolve, obtaining an aqueous solution containing 0.5% hydroxyethyl cellulose and 1% copolymer.

[0076] Preparation of the composite polymer solution containing 4% sodium chloride in Example 19

[0077] Sodium chloride was added to the composite polymer solution prepared in Example 18 and stirred to dissolve at room temperature, obtaining a composite polymer solution containing 4% sodium chloride.

[0078] Preparation of the composite polymer solution containing 1% hydroxyethyl cellulose and 1% copolymer in Example 20

[0079] The copolymers prepared in Examples 1-4 and 8-11 were respectively dissolved in ultrapure water, and then hydroxyethyl cellulose was added and stirred to dissolve, obtaining an aqueous solution containing 1% hydroxyethyl cellulose and 1% copolymer.

[0080] Preparation of the composite polymer solution containing 4% sodium chloride in Example 21

[0081] Sodium chloride was added to the composite polymer solution prepared in Example 20 and stirred to dissolve at room temperature, obtaining a composite polymer solution containing 4% sodium chloride.

[0082] Measurement of the viscosity-temperature property in Example 22

[0083] The solutions prepared in Examples 12-21 were taken, and the change of the solution viscosity with temperature was measured by a digital rotational viscometer at a shear rate of 100 s -1 .

[0084] Table 1. Viscosities of 2% copolymer aqueous solutions at different temperatures

[0085]

[0086] As shown in Table 1, by comparing the viscosities of the copolymer aqueous solutions prepared in Example 1, Example 2, and Example 3, it can be seen that when the molar ratios of the polymer units acrylamide, hydroxybutyl acrylate, and methoxypolyethylene glycol acrylate in the quaternary copolymer change little, the viscosity of the prepared quaternary copolymer increases as the molar ratio of the polymerization monomer N-isopropylmethacrylamide decreases. Among them, the viscosity of poly(acrylamide-N-isopropylmethacrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate) (2.03:0.11:1:0.17) prepared in Example 3 is the highest. Based on Example 3, if the polymerization monomer methoxypolyethylene glycol acrylate is not added during polymerization and only acrylamide, N-isopropylmethacrylamide, and hydroxybutyl acrylate are used as polymerization monomers, the viscosity of the obtained terpolymer (Example 4) is slightly higher than that of the quaternary copolymer prepared in Example 3. Based on Example 3, if the feed amount of methoxypolyethylene glycol acrylate is increased to twice the original amount, gelation occurs during the reaction, as shown in Example 5, indicating that gelation is likely to occur when the molar ratio of methoxypolyethylene glycol acrylate increases. Based on Example 3, if N-isopropylmethacrylamide is not added during polymerization and only acrylamide, hydroxybutyl acrylate, and methoxypolyethylene glycol acrylate are used as polymerization monomers, gelation occurs during the reaction and the target polymer cannot be obtained, as shown in Example 6, indicating that N-isopropylmethacrylamide can play a role in preventing gelation. Based on Example 6, when the feed amount of hydroxybutyl acrylate is increased to 1.2 times the original amount, gelation still cannot be prevented, as shown in Example 7. When the feed amount of hydroxybutyl acrylate is increased to 1.4 times the original amount, poly(acrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate) (2.23:1.40:0.18) is successfully obtained, as shown in Example 8. The viscosity of this terpolymer is slightly lower than that of the copolymers prepared in Example 3 and Example 4. Based on Example 3, with the feed amounts of hydroxybutyl acrylate and methoxypolyethylene glycol acrylate fixed, the feed amounts of acrylamide and N-isopropylmethacrylamide are increased to 1.33 times and 2 times the original amounts respectively, and poly(acrylamide-N-isopropylmethacrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate) (2.52:0.22:1:0.19) quaternary copolymer is prepared, as shown in Example 9. The viscosity of the quaternary copolymer prepared in Example 9 is similar to that of the quaternary copolymer prepared in Example 3. Based on Example 9, if the polymerization monomer methoxypolyethylene glycol acrylate is not added during polymerization and only acrylamide, N-isopropylmethacrylamide, and hydroxybutyl acrylate are used as polymerization monomers, the viscosity of the obtained terpolymer (Example 10) is the highest.On the basis of Example 9, if N-isopropylmethacrylamide is not added during polymerization and the feeding amount of hydroxybutyl acrylate is increased to 1.8 times the original amount, a poly(acrylamide-hydroxybutyl acrylate-methoxypolyethylene glycol acrylate) (2.48:1.80:0.13) terpolymer is prepared, as shown in Example 11. The viscosity of the terpolymer prepared in Example 11 is lower than that of the copolymers prepared in Examples 3, 4, 8, 9, and 10. On the basis of Example 3, if the polymerization monomer hydroxybutyl acrylate is replaced with sodium acrylate, a poly(acrylamide-N-isopropylmethacrylamide-sodium acrylate-methoxypolyethylene glycol acrylate) (2.11:0.13:1:0.19) quaternary copolymerization is prepared, as shown in Comparative Example 1. The thickening effect of this quaternary copolymer is not as good as that of the quaternary copolymer prepared in Example 3. The results in Table 1 show that the copolymers prepared in Examples 3, 4, 9, and 10 have good thickening effects.

[0087] Table 2. Viscosity of 2% copolymer aqueous solution containing 4% sodium chloride at different temperatures

[0088]

[0089]

[0090] Comparing Table 1 and Table 2, it can be seen that the viscosities of the quaternary copolymers prepared in Examples 3 and 9 basically remain unchanged in the presence of 4% sodium chloride. In comparison, the viscosities of the terpolymers prepared in Examples 4, 8, 10, and 11 decrease significantly in the presence of 4% sodium chloride, and the viscosity of the quaternary copolymer prepared in Comparative Example 1 also decreases significantly in the presence of 4% sodium chloride, indicating that the quaternary copolymers prepared in Examples 3 and 9 have good high-temperature and salt tolerance properties.

[0091] Table 3. Viscosity of composite polymer aqueous solution (hydroxyethyl cellulose concentration is 0.5%, copolymer concentration is 1%) at different temperatures

[0092]

[0093] Table 4. Viscosity of composite polymer aqueous solution (hydroxyethyl cellulose concentration is 1%, copolymer concentration is 1%) at different temperatures

[0094]

[0095] Comparing Table 1, Table 3 and Table 4, it can be seen that the copolymers prepared in Examples 3, 4, 8, 9, 10 and 11 have a synergistic thickening effect when compounded with hydroxyethyl cellulose in an aqueous solution. Although the viscosity of the aqueous solutions of the quaternary copolymers prepared in Examples 3 and 9 is slightly lower than that of the aqueous solutions of the ternary copolymers prepared in Examples 4 and 10, after compounding with hydroxyethyl cellulose, the viscosities of the composite polymer solutions formed by Examples 3, 9 and hydroxyethyl cellulose are higher than those of the composite polymer solutions formed by Examples 4, 10 and hydroxyethyl cellulose. At the same time, the viscosities of the composite polymer solutions formed by Examples 3, 9 and hydroxyethyl cellulose are also higher than those of the composite polymer solutions formed by Examples 8, 11 and hydroxyethyl cellulose. The above results show that the composite polymer solutions formed by the quaternary copolymers prepared in Examples 3 and 9 and hydroxyethyl cellulose have excellent synergistic thickening effects.

[0096] Table 5. Viscosities of Composite Polymer Aqueous Solutions Containing 4% Sodium Chloride (Hydroxyethyl Cellulose Concentration is 0.5%, Copolymer Concentration is 1%) at Different Temperatures

[0097]

[0098] Table 6. Viscosities of Composite Polymer Aqueous Solutions Containing 4% Sodium Chloride (Hydroxyethyl Cellulose Concentration is 1%, Copolymer Concentration is 1%) at Different Temperatures

[0099]

[0100] Comparing Table 3 with Table 5 and Table 4 with Table 6, it can be seen that the viscosity of the hydroxyethyl cellulose aqueous solution remains basically unchanged in the presence of 4% sodium chloride, while the viscosity of the sodium carboxymethyl cellulose aqueous solution decreases significantly in the presence of 4% sodium chloride. This is mainly because sodium carboxymethyl cellulose is an ionic polymer and its viscosity is easily affected by the charge shielding effect of salts, indicating that hydroxyethyl cellulose has good high-temperature and salt resistance properties. The viscosities of the composite polymer solutions formed by Examples 3, 9 and hydroxyethyl cellulose also remain basically unchanged in the presence of 4% sodium chloride, indicating that the composite polymer solutions formed by Examples 3, 9 and hydroxyethyl cellulose can maintain good high-temperature and salt resistance while having a synergistic thickening effect. In comparison, the viscosities of the composite polymer solutions formed by Examples 4, 8, 10, 11 and hydroxyethyl cellulose decrease significantly in the presence of 4% sodium chloride, which is due to the poor salt resistance of the ternary copolymers prepared in Examples 4, 8, 10, 11. The above results show that the composite polymer solutions formed by the quaternary copolymers prepared in Examples 3 and 9 and hydroxyethyl cellulose have excellent synergistic thickening effects and good high-temperature and salt resistance.

Claims

1. A high-temperature and salt-resistant composite polymer viscosifier, characterized in that, The high-temperature and salt-resistant composite polymer viscosifier is prepared by compounding a quaternary copolymer and hydroxyethyl cellulose in an aqueous solution according to a mass ratio of 1-2:0.5; The structural general formula of the quaternary copolymer is shown in Formula I: wherein, y:w:z:x is 2-3:0.1-0.3:1:0.1-0.2, and n = 9; The preparation method of the quaternary copolymer is as follows: acrylamide, N-isopropylmethacrylamide, hydroxybutyl acrylate and methoxypolyethylene glycol acrylate are dissolved in ultrapure water, ammonium persulfate is added, and the mixture is stirred and dissolved at room temperature. Nitrogen is introduced to remove the air in the reaction system, and the polymerization reaction is initiated by heating under nitrogen protection. After the reaction is completed, the reaction solution is cooled to room temperature, dialyzed with ultrapure water, and freeze-dried to obtain the quaternary copolymer; The molar ratio of acrylamide, N-isopropylmethacrylamide, hydroxybutyl acrylate and methoxypolyethylene glycol acrylate is 24-32:1-2:10:

2.

2. The high-temperature and salt-resistant composite polymer tackifier according to claim 1, wherein The feeding amount of ammonium persulfate is 0.08-0.2% of the total feeding mass of the polymerization monomers.

3. The high-temperature and salt-resistant composite polymer viscosifier according to claim 1, characterized in that, The molecular weight of methoxypolyethylene glycol acrylate is 480 Da.

4. The high-temperature and salt-resistant composite polymer viscosifier according to claim 1, characterized in that, The heating reaction temperature is 70 °C, and the reaction time is 3-8 hours.

5. A method for preparing a high-temperature and salt-resistant composite polymer viscosifier according to any one of claims 1-4, characterized in that, The preparation method is as follows: the quaternary copolymer and hydroxyethyl cellulose are dissolved in water to prepare the high-temperature and salt-resistant composite polymer viscosifier.

6. Use of the high-temperature and salt-resistant composite polymer viscosifier according to claim 1, characterized in that, The composite polymer viscosifier is used in the field of high-temperature and salt-resistant oil displacement agents.

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