Hydrophobically associating acrylamide copolymer, alcohol-based slickwater polymer viscosifier and preparation method thereof

Abstract

The present application relates to the oil field chemical technology field, it is a kind of hydrophobic association type acrylamide copolymer, alcohol base slick water high molecular thickening agent and its preparation method, the former is prepared according to the following method: under the protection of inert gas, acrylamide, 2-acrylamido-2-methylpropane sulfonic acid and long-chain alkyl acrylate are dissolved in solvent, auxiliary solvent is added, after stirring and mixing, first mixed solution is obtained;Part of initiator is added to the first mixed solution, first-stage reaction is carried out, then the remaining initiator is added, second-stage reaction is carried out, second mixed solution is obtained;Composite regulator is added to the second mixed solution, the pH value of system is adjusted, stirring, the product is dried, crushed to obtain hydrophobic association type acrylamide copolymer.The present application realizes long-acting stable viscosity of alcohol base slick water under high salinity, high temperature conditions, and the surface tension of gel breaking liquid and core damage rate are low, suitable for fracturing operation under high temperature and high salt reservoir conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry, and specifically relates to a hydrophobically associating acrylamide copolymer and a preparation method thereof, as well as an alcohol-based high-molecular thickener for slick water using the hydrophobically associating acrylamide copolymer as a raw material and a preparation method thereof. Background Art

[0002] Fracturing is an important technical means for the development of unconventional gas reservoirs. The performance of the fracturing fluid during the fracturing operation is an important technical guarantee for the fracturing operation. With the deepening of the development of unconventional oil and gas resources, high temperature (>120℃), high salt (mineralization>15×10 4 mg / L) reservoirs are increasing year by year. Traditional water-based fracturing fluids rely on polyacrylamide (HPAM) thickeners, but their molecular chains are prone to hydrolysis and chain scission at high temperatures, and high-valent metal ions (such as Ca 2+ Mg 2+ ) compresses the double layer, leading to viscosity collapse (viscosity retention <40% at 150°C). Although methanol-based slickwater can partially alleviate salt sensitivity, it suffers from high volatility, high biotoxicity (LC50 <500 mg / L), and poor compatibility with formation water. Existing improvements include: Chinese patent publication CN118895115A discloses a modified ethylene glycol fracturing fluid system for sensitivity and salt suppression, as well as its preparation method and application. The system comprises the following components by mass fraction: 10-15% 2-acrylamide-2-methylpropanesulfonic acid, 2-5% acrylic acid, 5-8% acrylamide, 20-50% acryloyloxyethyltrimethylammonium chloride, 5-10% epoxy acrylic resin, 0.1-1.0% organozirconium catalyst, and 50-90% modified ethylene glycol solution, with the total mass fraction of these components totaling 100%. It uses an ethylene glycol-based system, which reduces environmental risks, but its viscosity-increasing efficiency is difficult to meet the high sand-carrying requirements of deep reservoirs, and the residual surfactants after gel breaking will increase the oil-water interfacial tension and aggravate the blockage of reservoir pore throats.

[0003] Furthermore, traditional linear polymers lack a stable network structure that resists shear and salt. Therefore, a thermodynamically stable three-dimensional thickening system must be constructed through the coordinated design of hydrophobic association and rigid groups (such as sulfonic acid groups). Furthermore, to address the dual pressures of environmental and cost, the use of methanol-based solvents presents transportation and operational safety risks. Environmentally friendly alcohols (such as isopropyl alcohol) have insufficient solubility, resulting in polymer dispersion times exceeding 5 minutes, making them unsuitable for continuous on-site mixing. Therefore, a thickening agent system with improved high-temperature resistance, salt tolerance, and stability is urgently needed to meet the requirements of fracturing treatment in high-temperature, high-salinity reservoirs. Summary of the Invention

[0004] The present invention provides a hydrophobically associating acrylamide copolymer, an alcohol-based polymer thickener for slick water, and a preparation method thereof, which overcome the deficiencies of the above-mentioned prior art and can effectively solve the problem that the existing thickening system for fracturing fluid has poor high temperature resistance, salt resistance, and stability, and is difficult to meet the requirements of fracturing transformation of high-temperature and high-salt reservoirs.

[0005] One of the technical solutions of the present invention is achieved by the following measures: a hydrophobically associating acrylamide copolymer is prepared according to the following method:

[0006] In the first step, under the protection of inert gas, acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and long-chain alkyl acrylate are dissolved in a solvent, a co-solvent is added, and the mixture is stirred to obtain a first mixed solution;

[0007] In the second step, a portion of the initiator is added to the first mixed solution to carry out a first stage reaction, and then the remaining initiator is added to carry out a second stage reaction to obtain a second mixed solution;

[0008] The third step is to add a composite regulator to the second mixed solution, adjust the pH value of the system, stir, and obtain a hydrophobically associating acrylamide copolymer after drying and crushing the product.

[0009] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions:

[0010] The molecular weight distribution index (PDI) of the hydrophobically associating acrylamide copolymer is 1.0 to 1.8.

[0011] In the first step, the mass ratio of the total amount of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain alkyl acrylate to the solvent is 3% to 10%; the mass ratio of the total amount of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and long-chain alkyl acrylate to the co-solvent is 1:2 to 2:1.

[0012] In the first step, the stirring and mixing temperature is 35°C to 45°C.

[0013] In the first step, the molar ratio of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and long-chain alkyl acrylate is 65 to 75:20 to 30:2 to 8, wherein the structural formula of the long-chain alkyl acrylate is:

[0014]

[0015] R is a C12 to C18 long chain alkyl group.

[0016] In the first step, the solvent comprises, by mass, 1 to 3 parts of a low-carbon alcohol, 1 to 2 parts of a polyhydric alcohol, and 1 to 3 parts of water; wherein the low-carbon alcohol is methanol, ethanol, or isopropanol, and the polyhydric alcohol is glycerol or polyethylene glycol 200.

[0017] In the first step, the cosolvent is 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6).

[0018] In the second step, the initiator is a mixture of ammonium persulfate and sodium bisulfite, and the total amount of the initiator added is 0.02% to 0.05% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain alkyl acrylate.

[0019] In the second step, 55% to 70% of the total mass of the initiator is added to the first mixed solution to carry out the first stage reaction. When the viscosity of the system reaches 80 mPa·s to 120 mPa·s, the remaining initiator is added.

[0020] In the above second step, the reaction temperature of the first stage reaction is 45° C. to 50° C., the reaction temperature of the second stage reaction is 50° C. to 60° C., and the reaction time of the second stage reaction is 0.5 h to 2 h.

[0021] In the third step, the composite regulator is a mixture of sodium citrate and triethanolamine, the mass ratio of sodium citrate to triethanolamine is 1:2 to 1:4, and the pH value of the system is adjusted to between 6.5 and 7.5.

[0022] In the third step, vacuum low-temperature drying is used for drying, the drying temperature is 45°C to 55°C, the vacuum degree is between -0.08MPa and -0.15MPa, and the moisture content of the dried product is less than 3%.

[0023] The second technical solution of the present invention is achieved by the following measures: A method for preparing a hydrophobically associating acrylamide copolymer is carried out according to the following steps:

[0024] In the first step, under the protection of inert gas, acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and long-chain alkyl acrylate are dissolved in a solvent, a co-solvent is added, and the mixture is stirred to obtain a first mixed solution;

[0025] In the second step, a portion of the initiator is added to the first mixed solution to carry out a first stage reaction, and then the remaining initiator is added to carry out a second stage reaction to obtain a second mixed solution;

[0026] The third step is to add a composite regulator to the second mixed solution, adjust the pH value of the system, stir, and obtain a hydrophobically associating acrylamide copolymer after drying and crushing the product.

[0027] The third technical solution of the present invention is achieved by the following measures: an alcohol-based polymer thickener for slippery water, the raw materials of which are composed by mass percentage: 0.1% to 5% of a hydrophobically associating acrylamide copolymer, 0.1% to 1.0% of nano-silica, 50% to 85% of a main alcohol solvent, 0.1% to 5% of an ionic liquid cosolvent, and the remainder being water.

[0028] The following are further optimizations and / or improvements to the third technical solution of the above invention:

[0029] The nano-silicon dioxide is a hydrophobic nano-silicon material.

[0030] The main alcohol solvent is a mixture of a low-carbon alcohol and a polyhydric alcohol in a mass ratio of 3:1 to 1:2, wherein the low-carbon alcohol is methanol, ethanol or isopropanol, and the polyhydric alcohol is glycerol or polyethylene glycol 200.

[0031] The ionic liquid cosolvent is 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6).

[0032] The fourth technical solution of the present invention is achieved by the following measures: a method for preparing a polymer thickener for alcohol-based slick water, comprising the following steps:

[0033] After the required amount of hydrophobically associating acrylamide copolymer and nano-silica are uniformly mixed, a main alcohol solvent, an ionic liquid cosolvent and water are added in sequence, and the mixture is stirred to obtain an alcohol-based high molecular thickener for slippery water.

[0034] The present invention provides a hydrophobically associating acrylamide copolymer and a high molecular thickener for alcohol-based slippery water from the aspects of molecular structure and solvent. The high molecular thickener for alcohol-based slippery water of the present invention has the functions of drag reduction, sand carrying and low damage. The prepared alcohol-based slippery water has a viscosity of 20×10 4 The product has a high salinity of mg / L, long-term stable viscosity (viscosity > 50 mPa·s) at 150°C, a breaker surface tension ≤ 28.5 mN / m, and a core damage rate < 15%, providing a solution that combines high efficiency and environmental adaptability for reservoir reconstruction under extreme conditions. Furthermore, the degraded alcohol monomer has the function of reducing water lock damage, making it particularly suitable for the development of unconventional oil and gas reservoirs. DETAILED DESCRIPTION

[0035] The present invention is not limited to the following embodiments; specific implementation methods may be determined based on the technical solutions of the present invention and actual conditions. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all known and commonly used chemical reagents and chemicals in the prior art. Unless otherwise specified, percentages in the present invention are by mass. Normal temperature and room temperature in the present invention generally refer to temperatures between 15°C and 25°C, with 25°C generally defined as the room temperature.

[0036] The present invention will be further described below in conjunction with the embodiments:

[0037] Example 1: The hydrophobically associating acrylamide copolymer was prepared according to the following method:

[0038] In the first step, under the protection of inert gas, acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and long-chain alkyl acrylate are dissolved in a solvent, a co-solvent is added, and the mixture is stirred to obtain a first mixed solution;

[0039] In the second step, a portion of the initiator is added to the first mixed solution to carry out a first stage reaction, and then the remaining initiator is added to carry out a second stage reaction to obtain a second mixed solution;

[0040] The third step is to add a composite regulator to the second mixed solution, adjust the pH value of the system, stir, and obtain a hydrophobically associating acrylamide copolymer after drying and crushing the product.

[0041] Example 2: As an optimization of the above example, the molecular weight distribution index (PDI) of the hydrophobically associating acrylamide copolymer is 1.0 to 1.8.

[0042] Example 3: As an optimization of the above example, in the first step, the mass ratio of the total amount of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain alkyl acrylate to the solvent is 3% to 10%; the mass ratio of the total amount of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and long-chain alkyl acrylate to the co-solvent is 1:2 to 2:1.

[0043] Example 4: As an optimization of the above example, in the first step, the stirring and mixing temperature is 35°C to 45°C.

[0044] Example 5: As an optimization of the above example, in the first step, the molar ratio of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain alkyl acrylate is 65 to 75:20 to 30:2 to 8, wherein the structural formula of the long-chain alkyl acrylate is:

[0045]

[0046] R is a C12 to C18 long chain alkyl group.

[0047] Example 6: As an optimization of the above example, in the first step, the solvent includes, by mass, 1 to 3 parts of low-carbon alcohol, 1 to 2 parts of polyhydric alcohol and 1 to 3 parts of water; wherein the low-carbon alcohol is methanol, ethanol or isopropanol, and the polyhydric alcohol is glycerol or polyethylene glycol 200.

[0048] Example 7: As an optimization of the above example, in the first step, the cosolvent is 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6).

[0049] Example 8: As an optimization of the above example, in the second step, the initiator is a mixture of ammonium persulfate and sodium bisulfite, and the total amount of the initiator added is 0.02% to 0.05% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain alkyl acrylate.

[0050] Example 9: As an optimization of the above example, in the second step, 55% to 70% of the total mass of the initiator is added to the first mixed liquid to carry out the first stage reaction. When the viscosity of the system reaches 80 mPa·s to 120 mPa·s, the remaining initiator is added.

[0051] Example 10: As an optimization of the above example, in the second step, the reaction temperature of the first reaction is 45°C to 50°C, the reaction temperature of the second reaction is 50°C to 60°C, and the reaction time of the second reaction is 0.5h to 2h.

[0052] Example 11: As an optimization of the above example, in the third step, the composite regulator is a mixture of sodium citrate and triethanolamine, the mass ratio of sodium citrate to triethanolamine is 1:2 to 1:4, and the pH value of the system is adjusted to between 6.5 and 7.5.

[0053] Example 12: As an optimization of the above example, in the third step, vacuum low-temperature drying is used for drying, the drying temperature is 45°C to 55°C, the vacuum degree is between -0.08MPa and -0.15MPa, and the moisture content of the product after drying is <3%.

[0054] Example 13: The alcohol-based polymer thickener for slippery water is composed of the following raw materials by mass percentage: 0.1% to 5% of a hydrophobically associating acrylamide copolymer, 0.1% to 1.0% of nano-silica, 50% to 85% of a main alcohol solvent, 0.1% to 5% of an ionic liquid cosolvent, and the remainder being water.

[0055] Example 14: As an optimization of the above example, the nano-silicon dioxide is a hydrophobic nano-silicon material. The nano-silicon dioxide in the present invention is BASF TS-421 nano-silicon dioxide.

[0056] Example 15: As an optimization of the above example, the main alcohol solvent is a mixture of a low-carbon alcohol and a polyhydric alcohol in a mass ratio of 3:1 to 1:2, the low-carbon alcohol is methanol, ethanol or isopropanol, and the polyhydric alcohol is glycerol or polyethylene glycol 200.

[0057] Example 16: As an optimization of the above example, the ionic liquid cosolvent is 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6).

[0058] Example 17: A method for preparing the alcohol-based polymer thickener for slick water, comprising the following steps:

[0059] After the required amount of hydrophobically associating acrylamide copolymer and nano-silica are uniformly mixed, a main alcohol solvent, an ionic liquid cosolvent and water are added in sequence, and the mixture is stirred to obtain an alcohol-based high molecular thickener for slippery water.

[0060] Example 18:

[0061] (1) Preparation of hydrophobically associating acrylamide copolymer:

[0062] Under nitrogen protection, 5 parts by mass of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and octadecyl methacrylate (SMA) (the molar ratio of AM, AMPS, and SMA is 70:25:5) are dissolved in 80 parts of a solvent (the mass ratio of isopropanol, glycerol, and water is 1:1:1) at a temperature of 40°C and a magnetic stirring speed of 500 r / min until complete dissolution (about 30 min). 5 parts of a cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) are added, and the mixture is stirred for 10 min to obtain a first mixed solution.

[0063] Preparation of oxidation-reduction initiation system: ammonium persulfate (APS) and sodium bisulfite (SHS) were mixed in a mass ratio of 1:1, and the total addition amount was 0.04% of the monomer mass.

[0064] To the first mixed solution, 60% of the initiator (APS+SHS) was added, the temperature was raised to 50°C, and the reaction was allowed to proceed for 2 hours until the viscosity of the system increased to 100 mPa·s. The remaining 40% of the initiator was added, and the temperature was continued to be raised to 55°C. The reaction was maintained for 1 hour to promote the formation of a hydrophobic association network, thereby obtaining a second mixed solution.

[0065] A sodium citrate-triethanolamine composite regulator (sodium citrate:triethanolamine mass ratio of 1:3) was added to the second mixed solution, the pH value of the system was adjusted to 7.0±0.2, and the mixture was stirred for 10 minutes. The product was transferred to a vacuum dryer, the temperature was controlled at 50°C, the vacuum degree was -0.09 MPa, and the product was dried to a moisture content of <3% to obtain a hydrophobically associating acrylamide copolymer.

[0066] The hydrophobically associating acrylamide copolymer obtained in this example has a molecular weight distribution index PDI=1.5.

[0067] (2) Preparation of polymer thickener for alcohol-based slippery water:

[0068] The raw materials of the alcohol-based polymer thickener for slippery water are composed of the following by mass percentage:

[0069] The main alcohol solvent is 80% (isopropyl alcohol and glycerol are mixed in a mass ratio of 2:1), the hydrophobically associating acrylamide copolymer is 2.5%, the ionic liquid cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) is 2%, the nano-silica is 0.2%, and the rest is deionized water.

[0070] Preparation process:

[0071] The hydrophobically associating acrylamide copolymer is ground into 100 mesh powder by a pulverizer, mechanically mixed with nano-silica, and then a main alcohol solvent, an ionic liquid cosolvent and water are added in sequence. After stirring and mixing, an alcohol-based polymer thickener for slippery water is obtained.

[0072] Example 19:

[0073] (1) Preparation of hydrophobically associating acrylamide copolymer:

[0074] Under nitrogen protection, a total of 5 parts by mass of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and C14 alkyl acrylate (the molar ratio of AM, AMPS, and C14 alkyl acrylate is 65:30:5) are dissolved in 80 parts of a solvent (the mass ratio of isopropanol, glycerol, and water is 1:1:1) at a temperature of 45°C and a magnetic stirring speed of 500 r / min until complete dissolution (about 30 minutes). 5 parts of a cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) are added, and the mixture is stirred for 10 minutes to obtain a first mixed solution.

[0075] Preparation of oxidation-reduction initiation system: ammonium persulfate (APS) and sodium bisulfite (SHS) were mixed in a mass ratio of 1:1, and the total addition amount was 0.04% of the monomer mass.

[0076] To the first mixed solution, 60% of the initiator (APS+SHS) was added, the temperature was raised to 50°C, and the reaction was carried out for 2 hours until the viscosity of the system increased to 80 mPa·s. The remaining 40% of the initiator was added, and the temperature was continued to be raised to 55°C and the reaction was maintained for 2 hours to promote the formation of the hydrophobic association network, thereby obtaining the second mixed solution.

[0077] A sodium citrate-triethanolamine composite regulator (sodium citrate:triethanolamine mass ratio of 1:3) was added to the second mixed solution, the pH value of the system was adjusted to 7.0±0.2, and the mixture was stirred for 10 minutes. The reaction solution was transferred to a vacuum dryer, the temperature was controlled at 50°C, the vacuum degree was -0.09 MPa, and the mixture was dried to a moisture content of <3% to obtain a hydrophobically associating acrylamide copolymer.

[0078] The hydrophobically associating acrylamide copolymer obtained in this example has a molecular weight distribution index PDI=1.7.

[0079] (2) Preparation of polymer thickener for alcohol-based slippery water:

[0080] The raw materials are composed of the following in percentage by mass:

[0081] The main alcohol solvent is 75% (isopropyl alcohol and polyethylene glycol 200 are mixed in a mass ratio of 1:2), the hydrophobically associating acrylamide copolymer is 2.5%, the ionic liquid cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) is 1.5%, the nano-silica is 0.2%, and the rest is deionized water.

[0082] Preparation process:

[0083] The hydrophobically associating acrylamide copolymer is ground into 100 mesh powder by a pulverizer, mechanically mixed with nano-silica, and then a main alcohol solvent, an ionic liquid cosolvent and water are added in sequence. After stirring and mixing, an alcohol-based polymer thickener for slippery water is obtained.

[0084] Example 20:

[0085] (1) Preparation of hydrophobically associating acrylamide copolymer:

[0086] Under nitrogen protection, a total of 5 parts by mass of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and octadecyl methacrylate (SMA) (the molar ratio of AM, AMPS, and SMA is 68:24:8) are dissolved in 85 parts of a solvent (the mass ratio of isopropanol, glycerol, and water is 2:1:1) at a temperature of 40°C and a magnetic stirring speed of 500 r / min until complete dissolution (about 30 min). Then, 5 parts of a cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) are added, and the mixture is stirred for 10 min to obtain a first mixed solution.

[0087] Preparation of oxidation-reduction initiation system: ammonium persulfate (APS) and sodium bisulfite (SHS) were mixed in a mass ratio of 1:1, and the total addition amount was 0.04% of the monomer mass.

[0088] To the first mixed solution, 70% of the initiator was added, the temperature was raised to 45°C, and the reaction was carried out for 3 hours, until the viscosity of the system increased to 110 mPa·s. The remaining 30% of the initiator was added, the temperature was continued to be raised to 55°C, and the reaction was maintained for 1.5 hours to promote the formation of the hydrophobic association network, thereby obtaining the second mixed solution.

[0089] A sodium citrate-triethanolamine composite regulator (sodium citrate:triethanolamine mass ratio of 1:3) was added to the second mixed solution, the pH value of the system was adjusted to 7.0±0.2, and the mixture was stirred for 10 minutes. The reaction solution was transferred to a vacuum dryer, the temperature was controlled at 50°C, the vacuum degree was -0.09 MPa, and the mixture was dried to a moisture content of <3% to obtain a hydrophobically associating acrylamide copolymer.

[0090] The hydrophobically associating acrylamide copolymer obtained in this example has a molecular weight distribution index PDI=1.3.

[0091] (2) Preparation of polymer thickener for alcohol-based slippery water:

[0092] The raw materials are composed of the following in percentage by mass:

[0093] The main alcohol solvent is 80% (isopropyl alcohol and glycerol are mixed in a mass ratio of 2:1), the hydrophobically associating acrylamide copolymer is 2.5%, the ionic liquid cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) is 1.0%, the nano-silica is 0.2%, and the rest is deionized water.

[0094] Preparation process:

[0095] The hydrophobically associating acrylamide copolymer is ground into 100 mesh powder by a pulverizer, mechanically mixed with nano-silica, and then a main alcohol solvent, an ionic liquid cosolvent and water are added in sequence. After stirring and mixing, an alcohol-based polymer thickener for slippery water is obtained.

[0096] Example 21:

[0097] (1) Preparation of hydrophobically associating acrylamide copolymer:

[0098] Under nitrogen, dissolve 5 parts by mass of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and octadecyl methacrylate (SMA) (the molar ratio of AM, AMPS, and SMA is 70:28:2) in 70 parts of solvent (ethanol, polyethylene glycol 200, and water in a 2:1:2 mass ratio) at 40°C with magnetic stirring at 500 r / min until completely dissolved (approximately 30 minutes). Add 3 parts of a cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) and stir for 10 minutes to obtain a first mixed solution.

[0099] Preparation of oxidation-reduction initiation system: ammonium persulfate (APS) and sodium bisulfite (SHS) are mixed in a mass ratio of 1:1, and the total addition amount is 0.05% of the monomer mass.

[0100] To the first mixed solution, 60% of the initiator (APS+SHS) was added, the temperature was raised to 50°C, and the reaction was allowed to proceed for 2 hours until the viscosity of the system increased to 100 mPa·s. The remaining 40% of the initiator was added, and the temperature was continued to be raised to 55°C. The reaction was maintained for 1 hour to promote the formation of a hydrophobic association network, thereby obtaining a second mixed solution.

[0101] A sodium citrate-triethanolamine composite regulator (sodium citrate:triethanolamine mass ratio of 1:3) was added to the second mixed solution, the pH value of the system was adjusted to 7.0±0.2, and the mixture was stirred for 10 minutes. The reaction solution was transferred to a vacuum dryer, the temperature was controlled at 50°C, the vacuum degree was -0.09 MPa, and the mixture was dried to a moisture content of <3% to obtain a hydrophobically associating acrylamide copolymer.

[0102] The hydrophobically associating acrylamide copolymer obtained in this example has a molecular weight distribution index PDI=1.5.

[0103] (2) Preparation of polymer thickener for alcohol-based slippery water:

[0104] The raw materials are composed of the following in percentage by mass:

[0105] The main alcohol solvent is 60% (ethanol and polyethylene glycol 200 are mixed in a mass ratio of 1:1), the hydrophobically associating acrylamide copolymer is 3.5%, the ionic liquid cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) is 0.8%, the nano-silica is 0.5%, and the rest is deionized water.

[0106] Preparation process:

[0107] The hydrophobically associating acrylamide copolymer is ground into 100 mesh powder by a pulverizer, mechanically mixed with nano-silica, and then a main alcohol solvent, an ionic liquid cosolvent and water are added in sequence. After stirring and mixing, an alcohol-based polymer thickener for slippery water is obtained.

[0108] Example 22:

[0109] (1) Preparation of hydrophobically associating acrylamide copolymer:

[0110] Under nitrogen protection, a total of 5 parts by mass of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and octadecyl methacrylate (SMA) (the molar ratio of AM, AMPS, and SMA is 70:28:2) are dissolved in 80 parts of a solvent (the mass ratio of isopropanol, glycerol, and water is 1:1:1) at a temperature of 40°C and a magnetic stirring speed of 500 r / min until complete dissolution (about 30 minutes). 5 parts of a cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) are added, and the mixture is stirred for 10 minutes to obtain a first mixed solution.

[0111] Preparation of oxidation-reduction initiation system: ammonium persulfate (APS) and sodium bisulfite (SHS) are mixed in a mass ratio of 1:1, and the total addition amount is 0.05% of the monomer mass.

[0112] To the first mixed solution, 60% of the initiator (APS+SHS) was added, the temperature was raised to 50°C, and the reaction was allowed to proceed for 2 hours until the viscosity of the system increased to 100 mPa·s. The remaining 40% of the initiator was added, and the temperature was continued to be raised to 55°C. The reaction was maintained for 1 hour to promote the formation of a hydrophobic association network, thereby obtaining a second mixed solution.

[0113] A sodium citrate-triethanolamine composite regulator (sodium citrate:triethanolamine mass ratio of 1:4) was added to the second mixed solution, the pH value of the system was adjusted to 7.0±0.2, and the mixture was stirred for 10 minutes. The reaction solution was transferred to a vacuum dryer, the temperature was controlled at 50°C, the vacuum degree was -0.09 MPa, and the mixture was dried to a moisture content of <3% to obtain a hydrophobically associating acrylamide copolymer.

[0114] The hydrophobically associating acrylamide copolymer obtained in this example has a molecular weight distribution index PDI=1.5.

[0115] (2) Preparation of polymer thickener for alcohol-based slippery water:

[0116] The raw materials are composed of the following in percentage by mass:

[0117] The main alcohol solvent is 80% (isopropyl alcohol and glycerol are mixed in a mass ratio of 2:1), the hydrophobically associating acrylamide copolymer is 2.5%, the ionic liquid cosolvent (1-butyl-3-methylimidazolium hexafluorophosphate) is 0.8%, the nano-silica is 0.5%, and the rest is deionized water.

[0118] Preparation process:

[0119] The hydrophobically associating acrylamide copolymer is ground into 100 mesh powder by a pulverizer, mechanically mixed with nano-silica, and then a main alcohol solvent, an ionic liquid cosolvent and water are added in sequence. After stirring and mixing, an alcohol-based polymer thickener for slippery water is obtained.

[0120] Comparative Example 1: Different from Example 18, in the preparation of the hydrophobically associating acrylamide copolymer, the molar ratio of the three monomers was acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and octadecyl methacrylate (SMA) = 80:20:10, and the molecular weight distribution index (PDI) of the prepared polymer was 0.9.

[0121] Comparative Example 2: The difference from Example 18 is that in the preparation of the hydrophobically associating acrylamide copolymer, all the initiators were added at one time and the reaction was carried out at a temperature of 50° C. for 3 hours.

[0122] Comparative Example 3: The difference from Example 18 is that 1-butyl-3-methylimidazole hexafluorophosphate is not added in the preparation of the hydrophobically associating acrylamide copolymer.

[0123] Comparative Example 4: The difference from Example 18 is that in the preparation of the polymer thickener for alcohol-based slick water, 1-butyl-3-methylimidazolium hexafluorophosphate is replaced by an equal amount of sodium metaphosphate solution.

[0124] System performance testing

[0125] According to the shale oil and gas industry standards, a friction tester and a Hake Marrs-III rheometer were used to carry out resistance reduction performance and temperature and shear resistance tests.

[0126] The mineralization degree is 15×10 4 The alcohol-based slickwater prepared in Examples 18 to 22 was treated with a polymer thickener and the thickener prepared in Comparative Examples 1 to 4 to prepare a 1.0 wt% thickener solution. A 0.05 wt% breaker (ammonium persulfate) was also added. The thickener solution was placed in an aging tank and aged for 120 minutes at reservoir temperature (150°C). The viscosity of the solution was then tested. After aging for 12 hours, the viscosity of the degraded breaker solution was also tested. The polymer breaker solution was also collected and tested for reservoir damage according to industry standards. The test results are shown in Table 1.

[0127] Table 1

[0128] .

[0129] Test results show that the fracturing fluid system prepared using the alcohol-based slickwater polymer thickener of the present invention meets the industry standards for fracturing fluid (the industry standards require the fracturing fluid system to simultaneously meet the following requirements: viscosity > 50 mPa·s, drag reduction > 70%, and core damage rate < 30%), has higher temperature and salt resistance and stability than the industry standards, and the reservoir damage caused by the gel breaker is far lower than the industry standards.

[0130] The present invention has the following advantages:

[0131] ① "Hydrophobic association + ionic liquid synergistic solubilization" dual-effect enhancement: This invention innovatively combines hydrophobic associating acrylamide copolymer with ionic liquid cosolvent to construct a thermodynamically stable three-dimensional network structure through hydrophobic association. At the same time, it utilizes the strong solubility and salt resistance of ionic liquid to synergistically improve the fracturing fluid under high temperature (≥150℃) and high salt (≥15×10 4 mg / L) environment (viscosity retention rate > 70%), solving the problem of easy hydrolysis and viscosity collapse of traditional water-based systems.

[0132] ② Precise design of salt-tolerant polymer molecular structure and control of polymerization narrow distribution. The present invention adopts copolymerization of acrylamide (AM), sulfonic acid monomer (AMPS) and long-chain alkyl acrylate in a specific molar ratio, and introduces molecular weight distribution index control technology to enhance the shear resistance and thermal stability of the polymer; combined with the segmented initiation polymerization process, it ensures the efficient formation of the hydrophobic associating network, and realizes the fracturing fluid in 170s. -1 Long-lasting stable viscosity at high shear rates (≥50mPa·s).

[0133] ③ The organic external phase adopts a main alcohol solvent, a compound of low-carbon alcohol and polyhydroxy alcohol. The present invention significantly improves the solubility and environmental adaptability of the solvent system by optimizing the compounding ratio of low-carbon alcohol and polyhydroxy alcohol, shortens the polymer dispersion time to within 5 minutes, and reduces volatility and biological toxicity, thereby meeting the safety and continuous mixing requirements under extreme reservoir conditions.

[0134] ④ Introducing nano-silica to enhance viscoelastic sand-carrying performance. The present invention innovatively introduces nano-silica to enhance the viscoelasticity of the system, taking into account both sand-carrying performance and resource recycling under extreme conditions, thereby reducing operating costs and reservoir damage.

[0135] In summary, the present invention provides a hydrophobically associating acrylamide copolymer and a polymer thickener for alcohol-based slippery water and a preparation method thereof, adopting the technical concept of "hydrophobic association + ionic liquid synergistic solubilization", achieving the alcohol-based slippery water in the range of 15×10 4 mg / L mineralization, long-term stable viscosity at 150°C, and a core damage rate of less than 15%, providing a solution that combines high efficiency and environmental adaptability for reservoir reconstruction under extreme conditions.

[0136] The above technical features respectively constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or removed according to actual needs to meet the requirements of different situations.

Claims

1. A hydrophobically associating acrylamide copolymer, characterized in that Prepared as follows: In the first step, under the protection of an inert gas, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and a long-chain alkyl acrylate are dissolved in a solvent, a co-solvent is added, and the mixture is stirred to obtain a first mixed solution; In the second step, a portion of the initiator is added to the first mixed solution to carry out a first stage reaction, and then the remaining initiator is added to carry out a second stage reaction to obtain a second mixed solution; The third step is to add a composite regulator to the second mixed solution, adjust the pH value of the system, stir, and dry and crush the product to obtain a hydrophobically associating acrylamide copolymer; In the first step, the molar ratio of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain alkyl acrylate is 65 to 75:20 to 30:2 to 8, wherein the structural formula of the long-chain alkyl acrylate is: R is a C12 to C18 long chain alkyl group; The cosolvent is 1-butyl-3-methylimidazolium hexafluorophosphate.

2. The hydrophobically associating acrylamide copolymer according to claim 1, characterized in that The molecular weight distribution index PDI of the hydrophobically associating acrylamide copolymer is 1.0 to 1.

8.

3. The hydrophobically associating acrylamide copolymer according to claim 1 or 2, characterized in that In the first step, the mass ratio of the total amount of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain alkyl acrylate to the solvent is 3% to 10%; the mass ratio of the total amount of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain alkyl acrylate to the co-solvent is 1:2 to 2:1; or / and, the stirring and mixing temperature is 35°C to 45°C.

4. The hydrophobically associating acrylamide copolymer according to claim 1, characterized in that In the first step, the solvent includes, by mass, 1 to 3 parts of a low-carbon alcohol, 1 to 2 parts of a polyhydric alcohol, and 1 to 3 parts of water, wherein the low-carbon alcohol is methanol, ethanol, or isopropanol, and the polyhydric alcohol is glycerol or polyethylene glycol 200.

5. The hydrophobically associating acrylamide copolymer according to claim 1, characterized in that In the second step, the initiator is a mixture of ammonium persulfate and sodium bisulfite, and the total amount of the initiator added is 0.02% to 0.05% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain alkyl acrylate; or / and, adding 55% to 70% of the total mass of the initiator to the first mixed solution to carry out the first stage reaction, and adding the remaining initiator when the viscosity of the system reaches 80 mPa·s to 120 mPa·s; Or / and, the reaction temperature of the first stage reaction is 45° C. to 50° C., the reaction temperature of the second stage reaction is 50° C. to 60° C., and the reaction time of the second stage reaction is 0.5 h to 2 h.

6. The hydrophobically associating acrylamide copolymer according to claim 1, characterized in that In the third step, the composite regulator is a mixture of sodium citrate and triethanolamine, the mass ratio of sodium citrate to triethanolamine is 1:2 to 1:4, and the pH value of the system is adjusted to between 6.5 and 7.5; Or / and, drying is carried out by vacuum low-temperature drying, the drying temperature is 45° C. to 55° C., the vacuum degree is between -0.08 MPa and -0.15 MPa, and the moisture content of the dried product is less than 3%.

7. A method for preparing a hydrophobically associating acrylamide copolymer according to any one of claims 2 to 6, characterized in that Follow these steps: In the first step, under the protection of an inert gas, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and a long-chain alkyl acrylate are dissolved in a solvent, a co-solvent is added, and the mixture is stirred to obtain a first mixed solution; In the second step, a portion of the initiator is added to the first mixed solution to carry out a first stage reaction, and then the remaining initiator is added to carry out a second stage reaction to obtain a second mixed solution; The third step is to add a composite regulator to the second mixed solution, adjust the pH value of the system, stir, and obtain a hydrophobically associating acrylamide copolymer after drying and crushing the product.

8. An alcohol-based polymer thickener for slippery water using the hydrophobically associating acrylamide copolymer according to any one of claims 1 to 6 as a raw material, characterized in that The raw materials are composed of 0.1% to 5% of hydrophobically associated acrylamide copolymer, 0.1% to 1.0% of nano-silicon dioxide, 50% to 85% of main alcohol solvent, 0.1% to 5% of ionic liquid cosolvent, and the rest of water in percentage by mass.

9. The alcohol-based polymer thickener for slippery water according to claim 8, characterized in that Nano-silica is a hydrophobic nano-silicon material; Or / and, the main alcohol solvent is a mixture of a low-carbon alcohol and a polyhydric alcohol in a mass ratio of 3:1 to 1:2, the low-carbon alcohol is methanol, ethanol or isopropanol, and the polyhydric alcohol is glycerol or polyethylene glycol 200; Or / and, the ionic liquid cosolvent is 1-butyl-3-methylimidazolium hexafluorophosphate.

10. A method for preparing the alcohol-based polymer thickener for slick water according to claim 8 or 9, characterized in that The following steps are involved: After the required amount of hydrophobically associating acrylamide copolymer and nano-silica are uniformly mixed, a main alcohol solvent, an ionic liquid cosolvent and water are added in sequence, and the mixture is stirred to obtain an alcohol-based high molecular thickener for slippery water.

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