Physical-chemical self-crosslinking thickeners and their preparation methods

Abstract

This invention relates to the field of oilfield chemistry, specifically a physical-chemical self-crosslinking thickener and its preparation method. This physical-chemical self-crosslinking thickener is based on a synergistic physical-chemical dual crosslinking mechanism and is obtained by a mild polymerization reaction of acrylamide, acrylic acid, physically crosslinking monomers, and chemically crosslinking monomers under photoinitiation. The physical-chemical self-crosslinking thickener of this invention exhibits excellent temperature and salt resistance, meeting the current needs of oil and gas field development. It can be widely applied to the development of oil and gas resources in high-temperature and ultra-high-temperature reservoirs. Its preparation method is reliable in principle, simple to operate, and operates under mild reaction conditions, showing broad market application prospects.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically a physical-chemical self-crosslinking thickener and its preparation method. Background Technology

[0002] Hydrophobic associating polymers are water-soluble polymers with a small amount of hydrophobic groups (typically <2 mol%) introduced into their molecular chains. Due to hydrophobic association, these hydrophobic groups aggregate in aqueous solutions, resulting in intramolecular and intermolecular associations within the polymer macromolecules. Therefore, hydrophobic associating polymers exhibit unique properties distinct from ordinary partially hydrolyzed polyacrylamide. When the polymer concentration exceeds the critical associative concentration, the hydrophobic associating polymer macromolecules form a dynamic, physically cross-linked three-dimensional network structure dominated by intermolecular associations. This significantly increases the hydrodynamic volume and substantially enhances viscosity, salt resistance, and temperature and shear resistance. Consequently, hydrophobic associating polymers are widely used in oilfield enhanced oil recovery and hydraulic fracturing.

[0003] Reported hydrophobic monomers include (meth)acrylate type, styrene type, (meth)acrylamide type, and allyl type. Acrylate type hydrophobic monomers (Li Zhongjun, Yao Junjian, Wang Yongli, et al. Synthesis and performance study of a hydrophobic associative sodium acrylate thickener [J]. Synthetic Materials Aging and Application, 2023, 52(5):19-22.) are extremely sensitive to temperature and pH, and easily lose their hydrophobic associative effect due to monomer hydrolysis, resulting in a significant decrease in polymer solution viscosity. Styrene type hydrophobic monomers contain rigid benzene ring groups (Song Fangyu. Synthesis and viscosity performance study of oilfield thickeners [D]. China University of Geosciences (Beijing), 2023.), which can effectively improve the temperature resistance and hydrolysis resistance of polymers. However, the low reactivity of vinyl structures and the excessive proximity of the benzene ring to the molecular backbone are not conducive to the copolymerization of hydrophobic monomers with acrylamide, nor are they conducive to improving the thickening effect of polymers. Allyl hydrophobic monomers have low polymerization rates (Fan Meiling. Synthesis and Performance Study of Enhanced Permeation Polymer-Based Fracturing Fluid Thickener [D]. Shaanxi University of Science and Technology, 2023.), making them difficult to copolymerize with acrylamide. The resulting hydrophobic associating polymers have low molecular weights and insignificant thickening effects. Acrylamide-type hydrophobic monomers have structures similar to acrylamide (Geng Tongmou. Hydrophobic Associating Water-Soluble Polymer P(AM / NaAA / DiAC)). 16 (Viscosity behavior of aqueous solution. Fine Chemicals, 2007, 24(9): 914-918). High reactivity ratio is beneficial to the polymerization reaction, but it also has the disadvantage of poor hydrolysis resistance.

[0004] "Deep conditions present numerous challenges." The harsh conditions such as ultra-high temperature, ultra-high pressure, ultra-high stress, and high salinity place higher demands on polymers used to improve oil recovery and hydraulic fracturing. Therefore, developing polymers with superior temperature and salt resistance has become an urgent problem to be solved. Summary of the Invention

[0005] This invention provides a physical-chemical self-crosslinking thickener and its preparation method, which overcomes the shortcomings of the prior art. It can effectively solve the problem that existing thickeners cannot simultaneously possess temperature resistance, salt resistance and viscosity-enhancing properties, making it difficult to meet the fracturing requirements of ultra-deep wells under high temperature and high salt conditions.

[0006] One of the technical solutions of this invention is achieved through the following measures: a physicochemical self-crosslinking thickener having the following chemical structural formula:

[0007]

[0008] In the formula, m1, m2, m3 and m4 are the degrees of polymerization of acrylamide monomer, acrylic acid monomer, physically crosslinked monomer and chemically crosslinked monomer, respectively, m1 is 65% to 80%, m2 is 15% to 30%, m3 is 0.05% to 0.5%, and m4 = 1 - m1 - m2 - m3; n is an integer from 12 to 18.

[0009] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0010] The molecular weight of the aforementioned physical-chemical self-crosslinking thickener is between 5 million and 9 million.

[0011] The above-mentioned physical-chemical self-crosslinking thickener was prepared according to the following steps:

[0012] Step 1: Add the four monomer compounds and solubilizer to water to obtain a monomer mixture;

[0013] Step 2: Remove dissolved oxygen from the monomer mixture;

[0014] 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 physical-chemical self-crosslinking thickener is obtained.

[0015] The four monomeric compounds are acrylamide, acrylic acid, physically crosslinked monomers, and chemically crosslinked monomers.

[0016] The above four monomer compounds, in molar amounts, consist of: 70 to 80 parts acrylamide, 15 to 30 parts acrylic acid, 0.05 to 0.5 parts physically crosslinking monomers, and the remainder being chemically crosslinking monomers.

[0017] The above-mentioned physical crosslinking monomer is an N-long-chain alkyl-N,N-dimethylpropene sulfonate inner salt, and the long-chain alkyl is a C12 to C18 long-chain alkyl.

[0018] The aforementioned chemical crosslinking monomer is 2-propenoxybenzaldehyde.

[0019] The solubilizer is sodium dodecyl sulfate, and the molar ratio of the solubilizer to the chemical crosslinking monomer is 1 to 2:1.

[0020] The photoinitiator mentioned above is azobisisobutyramidine hydrochloride or 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the amount of photoinitiator added is 0.01wt% to 0.1wt% of the total mass of the four monomer compounds.

[0021] In step one above, the total mass fraction of the monomer mixture is 20% to 30%, and the pH of the monomer mixture is 7 ± 0.5.

[0022] In step three above, the photopolymerization reaction time is 3 to 6 hours, the reaction temperature is 10°C to 30°C, and the light wavelength is 300 nm to 400 nm.

[0023] The above-mentioned physically crosslinked monomers are prepared according to the following steps:

[0024] The first step is to dissolve the long-chain tertiary amine and propenyl-1,3-sulfonyl lactone in solvents respectively;

[0025] The second step involves adding a solution of propenyl-1,3-sulfonyl lactone dropwise to a long-chain tertiary amine solution to obtain a reaction mixture.

[0026] The third step involves heating the reaction mixture and stirring it to obtain N-long-chain alkyl-N,N-dimethylpropene sulfonate inner salt.

[0027] In the first step above, the molar ratio of long-chain tertiary amine to propenyl-1,3-sulfonyl lactone is 1 to 1.2:1.

[0028] In the first step above, the solvent is acetone.

[0029] In the second step above, a solution of propenyl-1,3-sulfonyl lactone is added dropwise to a long-chain tertiary amine solution at a temperature of 15°C to 35°C.

[0030] In the third step above, the reaction temperature for stirring is 50°C to 60°C, and the reaction time is 6 to 12 hours.

[0031] The second technical solution of the present invention is achieved through the following measures: a method for preparing a physical-chemical self-crosslinking thickener, comprising the following steps:

[0032] Step 1: Add the four monomer compounds and solubilizer to water to obtain a monomer mixture;

[0033] Step 2: Remove dissolved oxygen from the monomer mixture;

[0034] 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 physical-chemical self-crosslinking thickener is obtained.

[0035] The four monomeric compounds are acrylamide, acrylic acid, physically crosslinked monomers, and chemically crosslinked monomers.

[0036] This invention provides a physical-chemical self-crosslinking thickener and its preparation method. The physical-chemical self-crosslinking thickener has good temperature and salt resistance properties, which meets the current needs of oil and gas field development. It can be widely used in the development of oil and gas resources in high-temperature and ultra-high-temperature reservoirs. Its preparation method is reliable in principle, simple to operate, and has mild reaction conditions, and has broad market application prospects. Attached Figure Description

[0037] Appendix Figure 1 This is a viscosity-concentration relationship curve of polymers D1 and S4 in Test Example 1 of the present invention.

[0038] Appendix Figure 2 This is a viscosity-mineralization (NaCl) relationship curve of polymers D1 and S4 in Test Example 2 of the present invention.

[0039] Appendix Figure 3 This is a viscosity-mineralization (CaCl) relationship curve of polymers D1 and S4 in Test Example 2 of the present invention.

[0040] Appendix Figure 4 This is a viscosity-temperature curve of polymer D1 in test example 3 of the present invention.

[0041] Appendix Figure 5 This is a viscosity-temperature curve of polymer S1 in test example 3 of the present invention.

[0042] Appendix Figure 6 This is a viscosity-temperature curve of polymer S2 in test example 3 of the present invention.

[0043] Appendix Figure 7 This is a viscosity-temperature curve of polymer S3 in test example 3 of the present invention.

[0044] Appendix Figure 8 This is a viscosity-temperature curve of polymer S4 in test example 3 of the present invention. Detailed Implementation

[0045] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0046] The present invention will be further described below with reference to embodiments:

[0047] Example 1: This physicochemical self-crosslinking thickener has the following chemical structural formula:

[0048]

[0049] In the formula, m1, m2, m3 and m4 are the degrees of polymerization of acrylamide monomer, acrylic acid monomer, physically crosslinked monomer and chemically crosslinked monomer, respectively, m1 is 65% to 80%, m2 is 15% to 30%, m3 is 0.05% to 0.5%, and m4 = 1 - m1 - m2 - m3; n is an integer from 12 to 18.

[0050] Example 2: As an optimization of the above example, the molecular weight of the physical-chemical self-crosslinking thickener is 5 million to 9 million.

[0051] Example 3: As an optimization of the above examples, this physicochemical self-crosslinking thickener was prepared according to the following steps:

[0052] Step 1: Add the four monomer compounds and solubilizer to water to obtain a monomer mixture;

[0053] Step 2: Remove dissolved oxygen from the monomer mixture;

[0054] 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 physical-chemical self-crosslinking thickener is obtained.

[0055] The four monomeric compounds are acrylamide, acrylic acid, physically crosslinked monomers, and chemically crosslinked monomers.

[0056] Example 4: As an optimization of the above example, the four monomer compounds, in molar amounts, consist of: 70 to 80 parts acrylamide, 15 to 30 parts acrylic acid, 0.05 to 0.5 parts physically crosslinking monomer, and the remainder being chemically crosslinking monomer.

[0057] Example 5: As an optimization of the above examples, the physical crosslinking monomer is N-long-chain alkyl-N,N-dimethylpropene sulfonate inner salt, and the long-chain alkyl is a C12 to C18 long-chain alkyl.

[0058] Example 6: As an optimization of the above examples, the chemical crosslinking monomer is 2-propenoxybenzaldehyde.

[0059] Example 7: As an optimization of the above examples, the solubilizer is sodium dodecyl sulfate, and the molar ratio of the solubilizer to the chemical crosslinking monomer is 1 to 2:1.

[0060] Example 8: As an optimization of the above example, the photoinitiator is azobisisobutyramidine hydrochloride or 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the amount of photoinitiator added is 0.01wt% to 0.1wt% of the total mass of the four monomer compounds.

[0061] Example 9: As an optimization of the above example, in step one, the total mass fraction of the monomer mixture is 20% to 30%, and the pH of the monomer mixture is 7 ± 0.5. The pH of the monomer mixture is adjusted using a NaOH solution with a mass concentration of 5% to 10%.

[0062] Example 10: As an optimization of the above example, in step three, the photopolymerization reaction time is 3h to 6h, the reaction temperature is 10℃ to 30℃, and the light wavelength is 300nm to 400nm.

[0063] Example 11: As an optimization of the above examples, a physically crosslinked monomer was prepared according to the following steps:

[0064] The first step is to dissolve the long-chain tertiary amine and propenyl-1,3-sulfonyl lactone in solvents respectively;

[0065] The second step involves adding a solution of propenyl-1,3-sulfonyl lactone dropwise to a long-chain tertiary amine solution to obtain a reaction mixture.

[0066] The third step involves heating the reaction mixture and stirring it to obtain N-long-chain alkyl-N,N-dimethylpropene sulfonate inner salt.

[0067] Example 12: As an optimization of the above example, in the first step, the molar ratio of long-chain tertiary amine to propenyl-1,3-sulfonyl lactone is 1 to 1.2:1.

[0068] Example 13: As an optimization of the above example, in the first step, the solvent is acetone.

[0069] Example 14: As an optimization of the above example, in the second step, a solution of propenyl-1,3-sulfonyl lactone is added dropwise to a long-chain tertiary amine solution at a temperature of 15°C to 35°C.

[0070] Example 15: As an optimization of the above example, in the third step, the reaction temperature of the stirring reaction is 50°C to 60°C, and the reaction time is 6h to 12h.

[0071] In this invention, the chemical reaction in the preparation process of the physically crosslinked monomer N-long-chain alkyl-N,N-dimethylpropene sulfonate inner salt is as follows:

[0072]

[0073] Wherein, R is a long-chain alkyl group from C12 to C18.

[0074] Example 16: The preparation process of this physical-chemical self-crosslinking thickener is as follows:

[0075] (1) Synthesis of physically crosslinked monomers:

[0076] 0.1 mol of dodecylamine was dissolved in 100 mL of acetone to obtain an acetone solution of dodecylamine; 0.1 mol of propenyl-1,3-sulfonyl lactone was dissolved in an appropriate amount of acetone to obtain an acetone solution of propenyl-1,3-sulfonyl lactone; at room temperature (25 °C), the acetone solution of propenyl-1,3-sulfonyl lactone was slowly added dropwise to the acetone solution of dodecylamine; after the addition was complete, the temperature was raised to 60 °C and the reaction was stirred for 12 h; the reaction was stopped, cooled, filtered, and dried under vacuum to obtain the physically crosslinked monomer N-dodecyl-N,N-dimethylpropenylsulfonate inner salt, with a yield of 95.1%.

[0077] (2) Synthesis of physicochemical self-crosslinking thickeners:

[0078] Weigh acrylamide, acrylic acid, physical crosslinking monomer N-dodecyl-N,N-dimethylpropenylsulfonic acid inner salt, chemical crosslinking monomer 2-propenoxybenzaldehyde, and solubilizer sodium dodecyl sulfate in a molar ratio of 74.9:25:0.05:0.05. Add an appropriate amount of distilled water, stir to dissolve evenly, adjust the pH to 7 with 5% NaOH solution, and add a small amount of distilled water to obtain a monomer mixture with a total mass fraction of 20%.

[0079] Nitrogen gas was bubbled through the monomer mixture for 15 minutes to remove dissolved oxygen. Azobisisobutyramidine hydrochloride photoinitiator (0.02 wt% of total monomer mass) was added and placed under a photoinitiator to carry out photopolymerization. The reaction temperature was controlled between 10°C and 30°C. After 6 hours of reaction, a white colloid was obtained. The colloid was cut, soaked in ethanol, dried, and pulverized to obtain a physical-chemical self-crosslinking thickener, denoted as polymer S1.

[0080] Example 17: The preparation process of this physical-chemical self-crosslinking thickener is as follows:

[0081] (1) Synthesis of physically crosslinked monomers:

[0082] 0.12 mol of tetradecylamine was dissolved in 100 mL of acetone to obtain an acetone solution of tetradecylamine; 0.1 mol of propenyl-1,3-sulfonyl lactone was dissolved in an appropriate amount of acetone to obtain an acetone solution of propenyl-1,3-sulfonyl lactone; at room temperature (25 °C), the acetone solution of propenyl-1,3-sulfonyl lactone was slowly added dropwise to the acetone solution of tetradecylamine; after the addition was complete, the temperature was raised to 55 °C and the reaction was stirred for 8 h; the reaction was stopped, cooled, filtered, and dried under vacuum to obtain the physically crosslinked monomer N-tetradecyl-N,N-dimethylpropenylsulfonate inner salt, with a yield of 96.8%.

[0083] (2) Synthesis of physicochemical self-crosslinking thickeners:

[0084] Weigh acrylamide, acrylic acid, physical crosslinking monomer N-tetradecyl-N,N-dimethylpropenylsulfonic acid inner salt, chemical crosslinking monomer 2-propenoxybenzaldehyde, and solubilizer sodium dodecyl sulfate in a molar ratio of 74.9:25:0.05:0.05. Add an appropriate amount of distilled water, stir to dissolve evenly, adjust the pH to 7 with 5% NaOH solution, and add an appropriate amount of distilled water to obtain a monomer mixture with a total mass fraction of 25%.

[0085] Nitrogen gas was bubbled into the monomer mixture for 15 minutes to remove dissolved oxygen from the water. Azobisisobutyramidine hydrochloride photoinitiator (0.02 wt% of total monomer mass) was added and placed under a photoinitiation device. The reaction temperature was controlled between 10°C and 30°C. After 5 hours of reaction, a white colloid was obtained. The colloid was cut into small pieces, soaked in ethanol, dried, and pulverized to obtain a physical-chemical self-crosslinking thickener, denoted as polymer S2.

[0086] Example 18: The preparation process of this physical-chemical self-crosslinking thickener is as follows:

[0087] (1) Synthesis of physically crosslinked monomers:

[0088] 0.11 mol of hexadecylamine was dissolved in 100 mL of acetone to obtain an acetone solution of hexadecylamine; 0.1 mol of propenyl-1,3-sulfonyl lactone was dissolved in an appropriate amount of acetone to obtain an acetone solution of propenyl-1,3-sulfonyl lactone; at room temperature (25 °C), the acetone solution of propenyl-1,3-sulfonyl lactone was slowly added dropwise to the acetone solution of hexadecylamine; after the addition was complete, the temperature was raised to 55 °C and the reaction was stirred for 6 h; the reaction was stopped, cooled, filtered, and dried under vacuum to obtain the physically crosslinked monomer N-hexadecyl-N,N-dimethylpropenylsulfonate inner salt, with a yield of 98.5%.

[0089] (2) Synthesis of physicochemical self-crosslinking thickeners:

[0090] Weigh acrylamide, acrylic acid, physical crosslinking monomer N-tetradecyl-N,N-dimethylpropenylsulfonic acid inner salt, chemical crosslinking monomer 2-propenoxybenzaldehyde, and solubilizer sodium dodecyl sulfate in a molar ratio of 74.7:25:0.25:0.05:0.05. Add an appropriate amount of distilled water, stir to dissolve evenly, adjust the pH to 7 with 5% NaOH solution, and add an appropriate amount of distilled water to obtain a monomer mixture with a total mass fraction of 30%.

[0091] Nitrogen gas was bubbled into the monomer mixture for 15 minutes to remove dissolved oxygen from the water. Azobisisobutyramidine hydrochloride photoinitiator (0.03 wt% of total monomer mass) was added and placed under a photoinitiator to carry out photopolymerization. The reaction temperature was controlled between 10°C and 30°C. After 4 hours of reaction, a white colloid was obtained. The colloid was cut, soaked in ethanol, dried, and pulverized to obtain a physical-chemical self-crosslinking thickener, denoted as polymer S3.

[0092] Example 19: The preparation process of this physical-chemical self-crosslinking thickener is as follows:

[0093] (1) The synthesis of the physically crosslinked monomer in this embodiment is the same as in Example 18.

[0094] (2) Synthesis of physicochemical self-crosslinking thickeners:

[0095] Weigh acrylamide, acrylic acid, physical crosslinking monomer N-tetradecyl-N,N-dimethylpropenylsulfonic acid inner salt, chemical crosslinking monomer 2-propenoxybenzaldehyde, and solubilizer sodium dodecyl sulfate in a molar ratio of 79.4:20:0.5:0.1:0.2. Add an appropriate amount of distilled water, stir to dissolve evenly, adjust the pH to 7 with 5% NaOH solution, and add an appropriate amount of distilled water to obtain a monomer mixture with a total mass fraction of 25%.

[0096] Nitrogen gas was bubbled through the monomer mixture for 15 minutes to remove dissolved oxygen from the water. 0.02 wt% of the total monomer mass of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone was added, and the mixture was placed under a photoinitiator. The reaction temperature was controlled between 10°C and 30°C, and a white colloid was obtained after 4 hours of reaction. The colloid was cut into small pieces, soaked in ethanol, dried, and pulverized to obtain a physical-chemical self-crosslinking thickener, denoted as polymer S4.

[0097] Comparative example:

[0098] Weigh acrylamide and acrylic acid at a molar ratio of 80:20, add an appropriate amount of distilled water, stir to dissolve evenly, adjust the pH to 7 with a 5% NaOH solution, and add an appropriate amount of distilled water to obtain a monomer mixture with a total mass fraction of 25%.

[0099] Nitrogen gas was bubbled through the monomer mixture for 15 minutes to remove dissolved oxygen from the water. 0.02 wt% of the total monomer mass of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone was added, and the mixture was placed under a photoinitiator. The reaction temperature was controlled between 10°C and 30°C. After 4 hours of reaction, a white colloid was obtained. The colloid was cut into small pieces, soaked in ethanol, dried, and pulverized to obtain a thickener, denoted as polymer D1.

[0100] Test Example 1: Analysis of Thickening Performance

[0101] Polymers D1 and S4 were prepared into solutions of various concentrations, and their viscosity-concentration curves were measured at room temperature using a six-speed viscometer. (See figure). Figure 1 .

[0102] from Figure 1 As can be seen, within the mass concentration range of 0.05% to 0.6%, the viscosity of polymer S4 is consistently greater than that of polymer D1, and the viscosity difference increases with increasing polymer concentration. This indicates that the physicochemical self-crosslinking thickener of the present invention has a better thickening effect than partially hydrolyzed polyacrylamide (polymer D1).

[0103] Test Example 2: Salt Resistance Performance Analysis

[0104] Polymer solutions of D1 and S4 were prepared at different mineralization levels to a concentration of 6000 mg / L. Viscosity-mineralization curves of the polymer solutions were measured at room temperature using a six-speed viscometer. (See figure). Figure 2 and Figure 3 .

[0105] from Figure 2 and Figure 3 As can be seen, the physicochemical self-crosslinking thickener (polymer S4) of this invention has significantly better salt resistance than partially hydrolyzed polyacrylamide (polymer D1), and at 12 × 10⁻⁶... 4 It can maintain a high viscosity even under high mineralization conditions of mg / L NaCl and 5000 mg / L CaCl2.

[0106] Test Example 3: Temperature Resistance Performance Analysis

[0107] Polymer D1 and polymers S1 to S4 were each prepared into polymer solutions with a concentration of 6000 mg / L. The solutions were then analyzed using a Hacker RS600 high-temperature, high-pressure rheometer at a shear rate of 100 s⁻¹. -1 The viscosity-temperature relationship curve of the polymer solution was measured under a heating rate of 3℃ / min, as shown in the figure. Figures 4 to 8 .

[0108] from Figures 4 to 8As can be seen, the viscosity of the polymers decreases with increasing temperature. The viscosity of polymer D1 is below 50 mPa·s after the temperature exceeds 144.5℃; polymers S1 to S4 still have a viscosity above 50 mPa·s after the temperature reaches 180℃, exhibiting better temperature resistance.

[0109] In summary, this invention synthesizes a physical-chemical self-crosslinking thickener. Based on a physical-chemical dual crosslinking synergistic mechanism, it undergoes mild polymerization under photoinitiation to obtain a product that combines excellent thickening properties, outstanding salt resistance (adapting to ultra-high salinity), and excellent temperature resistance (stable performance at 180℃). This effectively meets the exploitation needs of high-temperature and high-salinity oil and gas reservoirs, providing strong support for the economical and efficient development of deep and ultra-deep oil and gas resources.

[0110] 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 physicochemical self-crosslinking thickener, characterized in that... It has the following chemical structural formula: In the formula, m1, m2, m3 and m4 are the molar percentage contents of acrylamide monomer, acrylic acid monomer, physically crosslinked monomer and chemically crosslinked monomer in the copolymer, respectively, m1 is 65% to 80%, m2 is 15% to 30%, m3 is 0.05% to 0.5%, m4 = 1 - m1 - m2 - m3; n is an integer from 12 to 18; The molecular weight of the physical-chemical self-crosslinking thickener is between 5 million and 9 million.

2. The physicochemical self-crosslinking thickener according to claim 1, characterized in that... The physical-chemical self-crosslinking thickener was prepared according to the following steps: Step 1: Add the four monomer compounds and solubilizer to water 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 physical-chemical self-crosslinking thickener is obtained. The four monomeric compounds are acrylamide, acrylic acid, physically crosslinked monomers, and chemically crosslinked monomers.

3. The physicochemical self-crosslinking thickener according to claim 2, characterized in that... The four monomeric compounds, in molar amounts, consist of: 65 to 80 parts acrylamide, 15 to 30 parts acrylic acid, 0.05 to 0.5 parts physically crosslinking monomers, and the remainder being chemically crosslinking monomers.

4. The physicochemical self-crosslinking thickener according to claim 2 or 3, characterized in that... The physical crosslinking monomer is an N-long-chain alkyl-N,N-dimethylpropene sulfonate inner salt, where the long-chain alkyl group is a C12 to C18 long-chain alkyl group.

5. The physicochemical self-crosslinking thickener according to claim 2 or 3, characterized in that... The chemical crosslinking monomer is 2-propenoxybenzaldehyde.

6. The physicochemical self-crosslinking thickener according to claim 2, characterized in that... The solubilizer is sodium dodecyl sulfate, and the molar ratio of the solubilizer to the chemical crosslinking monomer is 1 to 2:

1.

7. The physicochemical self-crosslinking thickener according to claim 2, characterized in that... The photoinitiator is azobisisobutyramidine hydrochloride or 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the amount of photoinitiator added is 0.01wt% to 0.1wt% of the total mass of the four monomer compounds.

8. The physicochemical self-crosslinking thickener according to claim 2, characterized in that... In step one, the total mass fraction of the monomer mixture is 20% to 30%, and the pH of the monomer mixture is 7 ± 0.

5.

9. The physicochemical self-crosslinking thickener according to claim 2 or 8, characterized in that... In step three, the photopolymerization reaction lasts for 3 to 6 hours, the reaction temperature is 10°C to 30°C, and the light wavelength is 300 nm to 400 nm.

10. The physicochemical self-crosslinking thickener according to claim 4, characterized in that... Physically crosslinked monomers are prepared according to the following steps: The first step is to dissolve the long-chain tertiary amine and propenyl-1,3-sulfonyl lactone in solvents respectively; The second step involves adding a solution of propenyl-1,3-sulfonyl lactone dropwise to a long-chain tertiary amine solution to obtain a reaction mixture. The third step involves heating the reaction mixture and stirring it to obtain N-long-chain alkyl-N,N-dimethylpropene sulfonate inner salt.

11. The physicochemical self-crosslinking thickener according to claim 10, characterized in that... In the first step, the molar ratio of long-chain tertiary amine to propenyl-1,3-sulfonyl lactone is 1 to 1.2:

1.

12. The physicochemical self-crosslinking thickener according to claim 10, characterized in that... In the first step, the solvent is acetone.

13. The physicochemical self-crosslinking thickener according to claim 10, characterized in that... In the second step, a solution of propenyl-1,3-sulfonyl lactone is added dropwise to a long-chain tertiary amine solution at a temperature of 15°C to 35°C; or / and in the third step, the reaction temperature is 50°C to 60°C and the reaction time is 6 to 12 hours.

14. A method for preparing a physicochemical self-crosslinking thickener according to any one of claims 1 to 13, characterized in that... Follow these steps: Step 1: Add the four monomer compounds and solubilizer to water 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 physical-chemical self-crosslinking thickener is obtained. The four monomeric compounds are acrylamide, acrylic acid, physically crosslinked monomers, and chemically crosslinked monomers.

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