Self-crosslinking thickening agent and preparation method thereof

Abstract

The invention relates to the technical field of oilfield chemistry, in particular to a self-crosslinking thickening agent and a preparation method thereof, the self-crosslinking thickening agent is obtained by copolymerization of acrylamide, acrylic acid, a physical crosslinking monomer and a chemical crosslinking monomer; the physical crosslinking monomer is N-cinnamyl-N, N-dimethyl hexadecyl ammonium chloride; the chemical cross-linking monomer is N-allyl-N, N-dimethyl p-benzaldehyde ammonium bromide, and the chemical cross-linking monomer is N-allyl-N, N-dimethyl p-benzaldehyde ammonium bromide; the molar ratio of the acrylamide to the acrylic acid to the physical crosslinking monomer to the chemical crosslinking monomer is (70-80): (15-25): (0.1-0.5): (0.1-0.5). According to the self-crosslinking thickening agent and the preparation method thereof, the thickening agent has good temperature resistance and salt resistance, meets the current oil and gas field development requirements, is reliable in method principle, easy and convenient to operate and mild in reaction condition, has wide market application prospects and can be widely applied to oil and gas resource development of high-temperature and ultrahigh-temperature reservoirs.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil field chemistry, and is a self-crosslinking thickening agent and a preparation method thereof. BACKGROUND

[0002] China is rich in oil and gas resources, but the exploitation is difficult, among which the proportion of low permeability reserves is as high as 66%. According to the geological conditions of China's reservoirs, hydraulic fracturing technology has become one of the key measures for oil and gas reservoir stimulation. With the progress of deep and ultra-deep well technology in China, the reservoir temperature also gradually increases with the deepening of drilling depth.

[0003] Hydraulic fracturing fluid is mainly plant gum fracturing and polymer fracturing fluid. The advantages of plant gum fracturing fluid are good thickening effect, strong sand carrying capacity and small filtration loss, and the disadvantages are poor temperature resistance and higher friction. Synthetic polymer thickening agents are mainly modified polyacrylamide polymers of different types and different molecular weights, which can form chemical crosslinking with organic titanium, zirconium and other metal crosslinking agents, and have the advantages of temperature resistance, salt resistance and shear resistance, and are currently widely used in high-temperature and ultra-high-temperature reservoirs.

[0004] The Chinese patent document with publication number CN104449643A discloses a high-temperature-resistant polymer thickening agent for oil field fracturing fluid and its preparation method and application. The thickening agent is formed by solution polymerization of acrylamide, other olefin monomers, initiator and chain transfer agent in an aqueous solution, wherein the weight ratio of acrylamide, other olefin monomers and water is 10-20:6-18:62-84; the other olefin monomers are selected from one or more of anionic, cationic or non-ionic olefin monomers, preferably two or three. The solution polymerization forms anionic high molecular weight polyacrylamide polymer with a molecular weight of 4-8.5 million. The thickening agent and the crosslinking agent form a gel with good elasticity and can withstand high temperatures above 210℃. The Chinese patent document with publication number CN111019042A discloses a high-temperature-resistant thickening agent for fracturing fluid and its preparation method. The high-temperature-resistant thickening agent for fracturing fluid includes acrylamide, salt-resistant functional monomer and temperature-sensitive functional monomer free radicals; the molar ratio of acrylamide, salt-resistant functional monomer and temperature-sensitive functional monomer is 1:(0.01-0.08):(0.05-0.15). The copolymerization of acrylamide, salt-resistant monomer and temperature-sensitive functional monomer forms a polyacrylamide thickening agent, which can have good temperature resistance and thickening effect at high temperatures above 200℃ when crosslinked with an organic zirconium crosslinking agent. However, the above two polymers need to be used with metal crosslinking agents to improve the temperature resistance.

[0005] The Chinese patent document with the publication number CN109705834A discloses a composition for preparing a temperature-resistant and salt-resistant fracturing fluid thickening agent, a temperature-resistant and salt-resistant fracturing fluid thickening agent prepared by using the composition, and a preparation method of the temperature-resistant and salt-resistant fracturing fluid thickening agent. The composition comprises the following components: acrylamide, acrylic acid, a hydrophobic monomer, 2-acrylamide-2-methylpropanesulfonic acid, a rigid monomer, a surfactant, and a shielding agent. The shielding agent cooperates with the rigid monomer to enhance the stability of the network structure, but only relies on the rigid group to support at high temperatures, and lacks dynamic crosslinking repair capability.

[0006] The Chinese patent document with the publication number CN113880983A discloses a self-associating enhanced integrated water-based high-temperature-resistant thickening agent and a preparation method thereof. The high-temperature-resistant type of high molecular polymer dispersant is made of acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, octadecyl dimethyl allyl ammonium chloride, and high-temperature-resistant monomers by aqueous solution polymerization. The dispersant and the dispersion stabilizer are mixed uniformly, and then the dispersant, the dispersion aid, and the surfactant are added and stirred at high speed to form the water-based high-temperature-resistant thickening agent. The hydrophobic association enhancement technology is adopted to improve the temperature resistance by introducing a hydrophobic monomer (such as octadecyl dimethyl allyl ammonium chloride) through physical association, but lacks chemical crosslinking support, and the dynamic crosslinking is easily dissociated under high shear conditions. The salt resistance depends on the cooperation of the surfactant, and the adaptability to high salinity brine is limited.

[0007] Therefore, it is urgent to develop a temperature-resistant and salt-resistant polymer to meet the needs of slick water fracturing in high-temperature and ultra-high-temperature reservoirs. SUMMARY

[0008] The present application provides a self-crosslinking thickening agent and a preparation method thereof, which overcomes the shortcomings of the prior art and effectively solves the problem that the existing temperature-resistant and salt-resistant polymer cannot meet the needs of slick water fracturing in high-temperature and ultra-high-temperature reservoirs.

[0009] One of the technical solutions of the present application is achieved by the following measures: a self-crosslinking thickening agent is obtained by copolymerization of acrylamide, acrylic acid, a physical crosslinking monomer, and a chemical crosslinking monomer; The physical crosslinking monomer is N-cinnamyl-N,N-dimethylhexadecyl ammonium chloride; The chemical crosslinking monomer is N-allyl-N,N-dimethyl-p-tolualdehyde bromide; The molar ratio of the acrylamide, the acrylic acid, the physical crosslinking monomer, and the chemical crosslinking monomer is (70 to 80):(15 to 25):(0.1 to 0.5):(0.1 to 0.5).

[0010] The following is a further optimization or / and improvement of one of the above technical solutions: The self-crosslinking thickening agent has the following structure: In the formula, m1, m2, m3 and m4 are the number of repeating units of each structural unit, and the ratio of m1, m2, m3 and m4 is (70 to 80):(15 to 25):(0.1 to 0.5):(0.1 to 0.5).

[0011] The self-crosslinking thickener has a molecular weight of 3 million to 9 million.

[0012] The self-crosslinking thickener is prepared by the following steps: Step one, acrylamide, acrylic acid, physical crosslinking monomer and chemical crosslinking monomer are added to water, and the pH is adjusted to neutral to obtain a monomer mixture; Step two, remove dissolved oxygen in the monomer mixture; Step three, add a photoinitiator to the monomer mixture to perform a photopolymerization reaction, and the reaction product is crushed, soaked, dried, and crushed to obtain a self-crosslinking thickener.

[0013] In step one, the total mass fraction of acrylamide, acrylic acid, physical crosslinking monomer and chemical crosslinking monomer in the monomer mixture is 20% to 30%.

[0014] In step three, the photopolymerization reaction time is 3 to 6 hours, and the reaction temperature is 10 to 30°C.

[0015] The photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and the amount of photoinitiator is 0.01wt% to 0.1wt% of the total mass of acrylamide, acrylic acid, physical crosslinking monomer and chemical crosslinking monomer.

[0016] The N-cinnamyl-N,N-dimethylhexadecyl ammonium chloride (physical crosslinking monomer) is prepared by the following steps: The required amount of hexadecylamine and cinnamyl chloride is dissolved in a solvent, and the reaction product is concentrated and recrystallized to obtain N-cinnamyl-N,N-dimethylhexadecyl ammonium chloride.

[0017] The solvent is anhydrous ethanol.

[0018] The reflux reaction temperature is 80 to 85°C, and the reaction time is 12 to 36 hours.

[0019] The molar ratio of hexadecylamine to cinnamyl chloride is 1 to 1.2:1.

[0020] The N-allyl-N,N-dimethyl-p-tolualdehyde bromide (chemical crosslinking monomer) is prepared by the following steps: The required amount of p-dimethylaminobenzaldehyde and bromopropylene are dissolved in the reaction solvent and refluxed. After the reaction product is concentrated and recrystallized, N-allyl-N,N-dimethylp-benzaldehyde ammonium bromide (chemical crosslinking monomer) is obtained.

[0021] The solvent used in the above reaction is acetonitrile.

[0022] The reflux reaction temperature is 80°C to 85°C, and the reaction time is 6 hours to 24 hours.

[0023] The above molar ratio of p-dimethylaminobenzaldehyde to bromopropylene is 1:1 to 1.2.

[0024] The second technical solution of the present invention is achieved through the following measures: a method for preparing a self-crosslinking thickener, comprising the following steps: Step 1: Add acrylamide, acrylic acid, physical crosslinking monomer, and chemical crosslinking monomer to water, and adjust the pH to neutral to obtain a monomer mixture. Step 2: Remove dissolved oxygen from the monomer mixture; Step 3: Add a photoinitiator to the monomer mixture to carry out a photopolymerization reaction. After the reaction product is crushed, soaked, dried, and pulverized, a self-crosslinking thickener is obtained.

[0025] This invention provides a self-crosslinking thickener and its preparation method. The thickener has good temperature and salt resistance properties, which meets the current needs of oil and gas field development. The method is reliable in principle, simple to operate, and has mild reaction conditions. It has broad market application prospects and can be widely used in the development of oil and gas resources in high-temperature and ultra-high-temperature reservoirs. Attached Figure Description

[0026] Appendix Figure 1 This is a viscosity-concentration relationship curve of self-crosslinking thickener S1 to S4 and thickener D1 in Test Example 1 of the present invention.

[0027] Appendix Figure 2 This is a graph showing the viscosity-mineralization (NaCl) relationship between self-crosslinking thickeners S1 to S4 and thickener D1 in Test Example 2 of the present invention.

[0028] Appendix Figure 3 This is a graph showing the viscosity-mineralization (CaCl) relationship between self-crosslinking thickeners S1 to S4 and thickener D1 in Test Example 2 of the present invention.

[0029] Appendix Figure 4 This is a viscosity-temperature curve of polymer D1 in test example 3 of the present invention.

[0030] Appendix Figure 5 This is a viscosity-temperature curve of polymer S3 in test example 3 of the present invention. Detailed Implementation

[0031] The present application is not limited by the following examples, and the specific implementation can be determined according to the technical solutions of the present application and the actual situation. The various chemical reagents and chemical supplies mentioned in the present application are well-known and commonly used chemical reagents and chemical supplies in the prior art unless otherwise specified; the percentages in the present application are mass percentages unless otherwise specified; the solutions in the present application are aqueous solutions with water as the solvent unless otherwise specified, for example, a hydrochloric acid solution is an aqueous hydrochloric acid solution; the normal temperature and room temperature in the present application generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0032] The present application will be further described below in conjunction with examples: Example 1: The self-crosslinking thickening agent is obtained by copolymerization of acrylamide, acrylic acid, a physical crosslinking monomer and a chemical crosslinking monomer; The physical crosslinking monomer is N-cinnamyl-N,N-dimethylhexadecyl ammonium chloride; The chemical crosslinking monomer is N-allyl-N,N-dimethyl-p-tolualdehyde ammonium bromide; The molar ratio of the acrylamide, the acrylic acid, the physical crosslinking monomer and the chemical crosslinking monomer is (70 to 80):(15 to 25):(0.1 to 0.5):(0.1 to 0.5).

[0033] Example 2: As an optimization of the above examples, the self-crosslinking thickening agent has the following structure: In the formula, m1, m2, m3 and m4 are the number of repeating units of each structural unit, and the ratio of m1, m2, m3 and m4 is (70 to 80):(15 to 25):(0.1 to 0.5):(0.1 to 0.5).

[0034] Example 3: As an optimization of the above examples, the molecular weight of the self-crosslinking thickening agent is 3 million to 9 million.

[0035] Example 4: As an optimization of the above examples, the self-crosslinking thickening agent is prepared by the following steps: Step one: acrylamide, acrylic acid, a physical crosslinking monomer and a chemical crosslinking monomer are added to water, and the pH is adjusted to neutral to obtain a monomer mixture; Step two: the dissolved oxygen in the monomer mixture is removed; Step three: a photoinitiator is added to the monomer mixture to perform a photopolymerization reaction, and the reaction product is subjected to crushing, soaking, drying and crushing to obtain the self-crosslinking thickening agent.

[0036] Example 5: As an optimization of the above examples, in step one, the total mass fraction of acrylamide, acrylic acid, a physical crosslinking monomer and a chemical crosslinking monomer in the monomer mixture is 20% to 30%.

[0037] Example 6: As an optimization of the above examples, in step three, the photopolymerization reaction is carried out for a period of 3 to 6 hours at a temperature of 10 to 30 °C.

[0038] Example 7: As an optimization of the above examples, the photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone; the amount of photoinitiator is 0.01 to 0.1 wt% of the total mass of acrylamide, acrylic acid, physical crosslinking monomer, and chemical crosslinking monomer.

[0039] Example 8: As an optimization of the above examples, N-cinnamyl-N,N-dimethylhexadecylammonium chloride (physical crosslinking monomer) is prepared according to the following procedure: The required amount of hexadecylamine and cinnamyl chloride are dissolved in a solvent and subjected to reflux reaction. The reaction product is obtained by concentration and recrystallization to obtain N-cinnamyl-N,N-dimethylhexadecylammonium chloride.

[0040] The reaction process is as follows: .

[0041] Example 9: As an optimization of the above examples, the solvent is anhydrous ethanol.

[0042] Example 10: As an optimization of the above examples, the reflux reaction temperature is 80 to 85 °C, and the reaction time is 12 to 36 hours.

[0043] Example 11: As an optimization of the above examples, the molar ratio of hexadecylamine to cinnamyl chloride is 1 to 1.2:1.

[0044] Example 12: As an optimization of the above examples, N-allyl-N,N-dimethyl-p- toluylammonium bromide (chemical crosslinking monomer) is prepared according to the following procedure: The required amount of p-dimethylaminobenzaldehyde and bromoallyl are dissolved in a reaction solvent and subjected to reflux reaction. The reaction product is obtained by concentration and recrystallization to obtain N-allyl-N,N-dimethyl-p-tolylammonium bromide.

[0045] The reaction process is as follows: .

[0046] Example 13: As an optimization of the above examples, the reaction solvent is acetonitrile.

[0047] Example 14: As an optimization of the above examples, the reflux reaction temperature is 80 to 85 °C, and the reaction time is 6 to 24 hours.

[0048] Example 15: As an optimization of the above example, the molar ratio of p-dimethylaminobenzaldehyde to bromopropylene is 1:1 to 1.2.

[0049] Example 16: (1) Preparation of physically crosslinked monomers: 0.12 mol of hexadecylamine and 0.1 mol of cinnamyl chloride were weighed and dissolved in 100 mL of anhydrous ethanol; the mixture was refluxed at 85 °C for 36 hours; the reaction was stopped, and the reaction product was subjected to rotary evaporation, recrystallization with ethyl acetate, and vacuum drying to obtain the physically crosslinked monomer N-cinnamyl-N,N-dimethylhexadecylammonium chloride, with a yield of 98.8%.

[0050] (2) Preparation of chemically crosslinked monomers: 0.1 mol of p-dimethylaminobenzaldehyde and 0.12 mol of bromopropene were dissolved in 100 mL of acetonitrile; the mixture was refluxed at 85 °C for 24 hours; the reaction was stopped, and the reaction product was subjected to rotary evaporation, recrystallization with ethyl acetate, and vacuum drying to obtain the chemically crosslinked monomer N-allyl-N,N-dimethylp-benzaldehyde ammonium bromide with a yield of 99.1%.

[0051] (3) Preparation of self-crosslinking thickener: Acrylamide, acrylic acid, the physically crosslinking monomer N-cinnamyl-N,N-dimethylhexadecyl ammonium chloride, and the chemically crosslinking monomer N-allyl-N,N-dimethyl-p-benzaldehyde ammonium bromide were weighed out in a molar ratio of 79.8:20:0.1:0.1. An appropriate amount of distilled water was added, and the mixture was stirred and dissolved evenly. The pH was adjusted to 7 with a 10% NaOH solution, and an appropriate amount of distilled water was added to obtain a monomer mixture with a total monomer mass fraction of 20%.

[0052] Nitrogen gas was bubbled into the monomer mixture for 15 minutes to remove dissolved oxygen from the water; 0.01 wt% of the total monomer mass of the initiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone was added; the mixture was placed under a photoinitiator and the photopolymerization reaction temperature was controlled between 10°C and 30°C. After 6 hours of reaction, a white colloid was obtained. The white colloid was cut into small pieces, soaked in ethanol, dried, and pulverized to obtain a self-crosslinking thickener, denoted as S1.

[0053] Example 17: (1) Preparation of physically crosslinked monomers: 0.12 mol of hexadecylamine and 0.1 mol of cinnamyl chloride were weighed and dissolved in 100 mL of anhydrous ethanol; the mixture was refluxed at 85 °C for 24 hours; the reaction was stopped, and the reaction product was subjected to rotary evaporation, recrystallization with ethyl acetate, and vacuum drying to obtain the physically crosslinked monomer N-cinnamyl-N,N-dimethylhexadecylammonium chloride, with a yield of 98.6%.

[0054] (2) Preparation of chemically crosslinked monomers: 0.1 mol of p-dimethylaminobenzaldehyde and 0.12 mol of bromopropene were dissolved in 100 mL of acetonitrile; the mixture was refluxed at 85 °C for 12 hours; the reaction was stopped, and the reaction product was subjected to rotary evaporation, recrystallization with ethyl acetate, and vacuum drying to obtain the chemically crosslinked monomer N-allyl-N,N-dimethylp-benzaldehyde ammonium bromide with a yield of 98.9%.

[0055] (3) Preparation of self-crosslinking thickener: Acrylamide, acrylic acid, the physically crosslinking monomer N-cinnamyl-N,N-dimethylhexadecyl ammonium chloride, and the chemically crosslinking monomer N-allyl-N,N-dimethyl-p-benzaldehyde ammonium bromide were weighed out in a molar ratio of 79.8:20:0.1:0.1. An appropriate amount of distilled water was added, and the mixture was stirred and dissolved evenly. The pH was adjusted to 7 with a 10% NaOH solution, and an appropriate amount of distilled water was added to obtain a monomer mixture with a total monomer mass fraction of 25%.

[0056] Nitrogen gas was bubbled into the monomer mixture for 15 minutes to remove dissolved oxygen from the water; 0.01 wt% of the total monomer mass of the initiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone was added; the mixture was placed under a photoinitiator and the photopolymerization reaction temperature was controlled between 10°C and 30°C. After 5 hours of reaction, a white colloid was obtained. The white colloid was cut into small pieces, soaked in ethanol, dried, and pulverized to obtain a self-crosslinking thickener, denoted as S2.

[0057] Example 18: (1) Preparation of physically crosslinked monomers: 0.11 mol of hexadecylamine and 0.1 mol of cinnamyl chloride were weighed and dissolved in 100 mL of anhydrous ethanol; the mixture was refluxed at 85 °C for 24 hours; the reaction was stopped, and the reaction product was subjected to rotary evaporation, recrystallization with ethyl acetate, and vacuum drying to obtain the physically crosslinked monomer N-cinnamyl-N,N-dimethylhexadecylammonium chloride, with a yield of 98.4%.

[0058] (2) Preparation of chemically crosslinked monomers: 0.1 mol of p-dimethylaminobenzaldehyde and 0.12 mol of bromopropene were dissolved in 100 mL of acetonitrile; the mixture was refluxed at 85 °C for 24 hours; the reaction was stopped, and the reaction product was subjected to rotary evaporation, recrystallization with ethyl acetate, and vacuum drying to obtain the chemically crosslinked monomer N-allyl-N,N-dimethylp-benzaldehyde ammonium bromide with a yield of 99.1%.

[0059] (3) Preparation of self-crosslinking thickener: Acrylamide, acrylic acid, the physically crosslinking monomer N-cinnamyl-N,N-dimethylhexadecyl ammonium chloride, and the chemically crosslinking monomer N-allyl-N,N-dimethyl-p-benzaldehyde ammonium bromide were weighed out in a molar ratio of 74.5:25:0.25:0.25. An appropriate amount of distilled water was added, and the mixture was stirred and dissolved evenly. The pH was adjusted to 7 with a 10% NaOH solution, and an appropriate amount of distilled water was added to obtain a monomer mixture with a total monomer mass fraction of 30%.

[0060] Nitrogen gas was bubbled into the monomer mixture for 15 minutes to remove dissolved oxygen from the water; 0.025 wt% of the total monomer mass of the initiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone was added; the mixture was placed under a photoinitiator and the photopolymerization reaction temperature was controlled between 10°C and 30°C. The reaction was carried out for 4 hours to obtain a white colloid; the white colloid was cut into small pieces, soaked in ethanol, dried, and pulverized to obtain a self-crosslinking thickener, denoted as S3.

[0061] Example 19: (1) Preparation of physically crosslinked monomers: 0.11 mol of hexadecylamine and 0.1 mol of cinnamyl chloride were weighed and dissolved in 100 mL of anhydrous ethanol; the mixture was refluxed at 80 °C for 12 hours; the reaction was stopped, and the reaction product was subjected to rotary evaporation, recrystallization with ethyl acetate, and vacuum drying to obtain the physically crosslinked monomer N-cinnamyl-N,N-dimethylhexadecylammonium chloride, with a yield of 97.6%.

[0062] (2) Preparation of chemically crosslinked monomers: 0.1 mol of p-dimethylaminobenzaldehyde and 0.11 mol of bromopropene were dissolved in 100 mL of acetonitrile; the mixture was refluxed at 80 °C for 12 hours; the reaction was stopped, and the reaction product was subjected to rotary evaporation, recrystallization with ethyl acetate, and vacuum drying to obtain the chemically crosslinked monomer N-allyl-N,N-dimethylp-benzaldehyde ammonium bromide with a yield of 98.2%.

[0063] (3) Preparation of self-crosslinking thickener: Weigh acrylamide, acrylic acid, the physically crosslinking monomer N-cinnamyl-N,N-dimethylhexadecyl ammonium chloride, and the chemically crosslinking monomer N-allyl-N,N-dimethyl-p-benzaldehyde ammonium bromide in a molar ratio of 79:20:0.5:0.5. Add an appropriate amount of distilled water, stir to dissolve evenly, adjust the pH to 7 with a 10% NaOH solution, and add an appropriate amount of distilled water to obtain a mixture with a total monomer mass fraction of 25%.

[0064] Nitrogen gas was bubbled into the monomer mixture for 15 minutes to remove dissolved oxygen from the water; 0.025 wt% of the total monomer mass of the initiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone was added; the mixture was placed under a photoinitiator and the photopolymerization reaction temperature was controlled between 10°C and 30°C. The reaction was carried out for 4 hours to obtain a white colloid; the white colloid was cut into small pieces, soaked in ethanol, dried, and pulverized to obtain a self-crosslinking thickener, denoted as S4.

[0065] Comparative example: Weigh acrylamide and acrylic acid in a molar ratio of 80:20, add an appropriate amount of distilled water, stir to dissolve evenly, adjust the pH to 7 with a 10% NaOH solution, and add an appropriate amount of distilled water to obtain a mixture with a total monomer mass fraction of 25%.

[0066] Nitrogen gas was bubbled into the monomer mixture for 15 minutes to remove dissolved oxygen from the water; 0.025 wt% of the total monomer mass of the initiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone was added; the mixture was placed under a photoinitiator and the photopolymerization reaction temperature was controlled between 10°C and 30°C. The reaction was carried out for 4 hours to obtain a white colloid; the white colloid was cut into small pieces, soaked in ethanol, vacuum dried, and pulverized to obtain a thickener, denoted as D1.

[0067] Test Example 1: Tackification Performance Analysis Self-crosslinking thickeners S1 to S4 and thickener D1 were prepared into solutions of a series of concentrations, and the viscosity-concentration relationship curves of each polymer were measured at room temperature using a six-speed viscometer (see...). Figure 1 ).

[0068] from Figure 1 As can be seen, when the polymer concentration is low (0.04%), the polymer viscosity is similar; as the polymer concentration increases, the thickening effect of self-crosslinking thickeners S1 to S4 becomes more significant, and the viscosity of the self-crosslinking thickener at a concentration of 0.6% is nearly twice that of the partially hydrolyzed polyacrylamide.

[0069] Test Example 2: Salt Resistance Performance Analysis Self-crosslinking thickeners S1 to S4 and thickener D1 were prepared into 0.6% polymer solutions at different salinities. The viscosity-salinity relationship curves of the polymers were measured at room temperature using a six-speed viscometer (see...). Figure 2 and Figure 3 ).

[0070] from Figure 2 and Figure 3 As can be seen, with the increase of mineralization, the apparent viscosity of crosslinking thickeners S1 to S4 and thickener D1 gradually decreases; at 12×10 4The viscosity retention rate of the self-crosslinking thickener remains above 40% under high salinity conditions of mg / L NaCl; under high divalent ion conditions of 5000 mg / L CaCl2, the viscosity retention rate of self-crosslinking thickeners S1 to S4 remains above 35%, and the viscosity retention rate of D1 is approximately 12%. This indicates that the self-crosslinking thickener of the present invention exhibits excellent salt resistance.

[0071] Test Example 3: Temperature Resistance Performance Analysis Thickener D1 and self-crosslinking thickener S3 were formulated into a polymer solution with a concentration of 6000 mg / L. The solution was then tested using a Hacker RS600 high-temperature, high-pressure rheometer at a shear rate of 100 s⁻¹. -1 Under a heating rate of 3℃ / min, the viscosity-temperature relationship curve of the polymer solution was measured (see...). Figure 4 , Figure 5 ).

[0072] from Figure 4 and Figure 5 As can be seen from this, with increasing temperature, thickener D1 (see...) Figure 4 Polymer D1) and self-crosslinking thickener S3 (see Figure 5 The viscosity of polymer S3 decreased. Thickener D1 had a viscosity below 50 mPa·s after the temperature exceeded 155℃; self-crosslinking thickener S3 maintained a viscosity of around 100 mPa·s after the temperature exceeded 180℃, showing better temperature resistance.

[0073] In summary, the self-crosslinking thickener of this invention exhibits excellent temperature and salt resistance, maintaining high viscosity even in high-temperature and high-salinity brine, making it suitable for high-temperature ultra-deep well mining. It also demonstrates outstanding thickening effect, achieving a viscosity nearly twice that of traditional polyacrylamide at the same concentration. Furthermore, it requires no external metal crosslinking agent and exhibits good structural stability. Moreover, the preparation process of this self-crosslinking thickener is mild and simple, with easily controllable conditions, making it suitable for large-scale production and showing promising application prospects.

[0074] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A self-crosslinking thickener, characterized in that... It is obtained by copolymerization of acrylamide, acrylic acid, physically crosslinking monomers and chemically crosslinking monomers; The physical crosslinking monomer is N-cinnamyl-N,N-dimethylhexadecylammonium chloride; The chemical crosslinking monomer is N-allyl-N,N-dimethyl-p-benzaldehyde ammonium bromide; The molar ratio of acrylamide, acrylic acid, physical crosslinking monomer, and chemical crosslinking monomer is 70 to 80: 15 to 25: 0.1 to 0.5: 0.1 to 0.

5.

2. The self-crosslinking thickener according to claim 1, characterized in that... It has the structure shown in the following formula: In the formula, m1, m2, m3 and m4 are the number of repeating units in each structural unit, and the ratio of m1 to m2, m3 and m4 is 70 to 80: 15 to 25: 0.1 to 0.5: 0.1 to 0.

5.

3. The self-crosslinking thickener according to claim 2, characterized in that... The molecular weight ranges from 3 million to 9 million.

4. The self-crosslinking thickener according to claim 1, characterized in that... It is prepared according to the following steps: Step 1: Add acrylamide, acrylic acid, physical crosslinking monomer, and chemical crosslinking monomer to water, and adjust the pH to neutral to obtain a monomer mixture. Step 2: Remove dissolved oxygen from the monomer mixture; Step 3: Add a photoinitiator to the monomer mixture to carry out a photopolymerization reaction. After the reaction product is crushed, soaked, dried, and pulverized, a self-crosslinking thickener is obtained.

5. The self-crosslinking thickener according to claim 4, characterized in that... In step one, the total mass fraction of acrylamide, acrylic acid, physically crosslinked monomers, and chemically crosslinked monomers in the monomer mixture is 20% to 30%.

6. The self-crosslinking thickener according to claim 4 or 5, characterized in that... In step three, the photopolymerization reaction lasts for 3 to 6 hours, and the reaction temperature is 10°C to 30°C. Or / and, the photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone; the amount of photoinitiator is 0.01wt% to 0.1wt% of the total mass of acrylamide, acrylic acid, physical crosslinking monomer, and chemical crosslinking monomer.

7. The self-crosslinking thickener according to claim 1, characterized in that... N-Cinnamyl-N,N-Dimethylhexadecylammonium chloride was prepared according to the following steps: The required amounts of hexadecylamine and cinnamyl chloride were dissolved in a solvent and refluxed. The reaction product was concentrated and recrystallized to obtain N-cinnamyl-N,N-dimethylhexadecylammonium chloride.

8. The self-crosslinking thickener according to claim 7, characterized in that... The solvent is anhydrous ethanol.

9. The self-crosslinking thickener according to claim 7 or 8, characterized in that... The reflux reaction temperature is 80°C to 85°C, and the reaction time is 12 to 36 hours.

10. The self-crosslinking thickener according to claim 7 or 8, characterized in that... The molar ratio of hexadecylamine to cinnamyl chloride is 1 to 1.2:

1.

11. The self-crosslinking thickener according to claim 1, characterized in that... N-Allyl-N,N-Dimethyl-p-benzaldehyde ammonium bromide was prepared according to the following steps: The required amount of p-dimethylaminobenzaldehyde and bromopropylene were dissolved in the reaction solvent and refluxed. The reaction product was concentrated and recrystallized to obtain N-allyl-N,N-dimethylp-benzaldehyde ammonium bromide.

12. The self-crosslinking thickener according to claim 11, characterized in that... The reaction solvent is acetonitrile.

13. The self-crosslinking thickener according to claim 11 or 12, characterized in that... The reflux reaction temperature is 80°C to 85°C, and the reaction time is 6 hours to 24 hours.

14. The self-crosslinking thickener according to claim 11 or 12, characterized in that... The molar ratio of p-dimethylaminobenzaldehyde to bromopropene is 1:1 to 1.

2.

15. A method for preparing a self-crosslinking thickener according to any one of claims 1 to 14, comprising the following steps: Step 1: Add acrylamide, acrylic acid, physical crosslinking monomer, and chemical crosslinking monomer to water, and adjust the pH to neutral to obtain a monomer mixture. Step 2: Remove dissolved oxygen from the monomer mixture; Step 3: Add a photoinitiator to the monomer mixture to carry out a photopolymerization reaction. After the reaction product is crushed, soaked, dried, and pulverized, a self-crosslinking thickener is obtained.

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