Oil gas fracturing salt-resistant thickening agent and preparation method thereof

Abstract

The invention relates to the technical field of oil field chemicals, in particular to an oil and gas fracturing salt-resistant thickening agent and a preparation method, and aims to solve the problem that a traditional polyacrylamide thickening agent is easy to degrade and lose efficacy in a high-salinity environment, so that the fracturing effect is poor. According to the preparation method, acrylamide, a polyalkenyl monomer, a double-ion monomer and a cyclodextrin monomer are used as polymerization monomers for polymerization to obtain the oil and gas fracturing salt-resistant thickening agent, and under the synergistic effect of the polyalkenyl monomer, the double-ion monomer and the cyclodextrin monomer as modified monomers, the oil and gas fracturing salt-resistant thickening agent is obtained. The polyacrylamide thickening agent has the advantages that the salt resistance, the high temperature resistance, the shear resistance and the thickening effect of the polyacrylamide thickening agent are jointly improved, the operation efficiency can be obviously improved, the fracturing effect can be optimized, the problems caused by salt pollution can be reduced in oil and gas fracturing operation, and the polyacrylamide thickening agent is an important breakthrough for finding an efficient and environment-friendly fracturing fluid treatment technology in the field of modern oil and gas exploitation.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemicals, and in particular to an oil and gas fracturing anti-salt thickener and a preparation method thereof. Background Art

[0002] In the process of oil and gas field development, fracturing technology is one of the important means to increase oil and gas production. The safety and effectiveness of the fracturing fluid system are directly related to the fracturing effect. Among them, polyacrylamide thickeners are one of the indispensable additives in the fracturing fluid system, which can effectively improve the viscosity of the fracturing fluid, enhance the support of the formation, and ultimately increase oil and gas production. However, the underground environment of oil and gas fields is complex and changeable, especially the highly mineralized salt water environment poses a severe challenge to the performance of fracturing fluids. In a high-salt environment, the molecular structure of traditional polyacrylamide thickeners is easily hydrolyzed and degraded, which reduces its thickening efficiency and affects the fracturing effect. The degraded polyacrylamide molecular fragments will reduce the viscosity of the fracturing fluid, which is not conducive to the stable flow of the liquid.

[0003] How to improve the traditional polyacrylamide thickeners that are prone to degradation and failure in high salinity environments, resulting in poor fracturing effects, is the key to the present invention. Therefore, it is particularly important to develop an oil and gas fracturing salt-resistant thickener and preparation method. Summary of the invention

[0004] In order to overcome the above technical problems, the purpose of the present invention is to provide an oil and gas fracturing salt-resistant thickener and a preparation method, which solves the problem that traditional polyacrylamide thickeners are prone to degradation and failure in high salinity environments, resulting in poor fracturing effects.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing an oil and gas fracturing anti-salt thickener comprises the following steps:

[0007] Step 1: Add methyl acrylate, ethylenediamine and anhydrous methanol into a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, introduce nitrogen protection, stir the reaction at a temperature of -5-0°C and a stirring rate of 300-400r / min for 1-2h, then heat the temperature to 25-30°C and continue stirring the reaction for 8-10h. After the reaction is completed, the reaction product is subjected to reduced pressure distillation at a temperature of 40-45°C to remove the solvent to obtain intermediate 1;

[0008] Step 2: Add intermediate 1, allylamine, dibutyltin dilaurate, hydroquinone and anhydrous ethanol to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, introduce nitrogen protection, stir and react for 20-30 minutes at a temperature of 25-30° C. and a stirring rate of 300-400 r / min, then heat to 105-110° C. and continue stirring and reacting for 3-5 hours. After the reaction is completed, cool the reaction product to room temperature, then vacuum filter, and rotary evaporate the filtrate to remove the solvent to obtain a polyene monomer;

[0009] Step 3: Add methyl acrylate, N,N-dimethylethanolamine, hydroquinone and tetrabutyl titanate into a three-necked flask equipped with a stirrer, a thermometer, an air duct and a reflux condenser, introduce nitrogen protection, stir and react for 20-30 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then heat to 85-90°C and continue to stir and react for 1-1.5 hours, then heat to 110-115°C and continue to stir and react for 6-8 hours, and after the reaction is completed, distill the reaction product under atmospheric pressure, remove the 65°C fraction, and obtain intermediate 2;

[0010] Step 4: Add the intermediate 2, sodium 2-bromoethylsulfonate and anhydrous acetonitrile to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, introduce nitrogen protection, stir the reaction at a temperature of 45-50°C and a stirring rate of 300-400r / min for 3-5h, then heat the mixture to reflux and continue stirring the reaction for 6-8h. After the reaction is completed, cool the reaction product to room temperature, add it to ice ether, let it stand and precipitate, then vacuum filter, wash the filter cake with anhydrous ether 2-3 times, then place it in a vacuum drying oven, and dry it at a temperature of 30-35°C for 3-5h to obtain a diionic monomer;

[0011] Step 5: Add β-cyclodextrin and deionized water to a three-necked flask equipped with an agitator, a thermometer and an air duct, introduce nitrogen protection, stir the reaction for 40-50 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then heat the temperature to 35-40°C and adjust the pH to 8-8.5 with a sodium carbonate solution, then add octenyl succinic anhydride solution and continue stirring the reaction for 8-10 hours, after the reaction is completed, cool the reaction product to room temperature, then adjust the pH to 6-6.5 with a hydrochloric acid solution, then vacuum filter, wash the filter cake with an ethanol solution for 2-3 times, then place it in a vacuum drying oven, and dry it at a temperature of 50-55°C for 3-5 hours to obtain a cyclodextrin monomer;

[0012] Step six: Add acrylamide, polyene monomer, diionic monomer, cyclodextrin monomer and deionized water to a three-necked flask equipped with an agitator, a thermometer and an air duct, introduce nitrogen protection, stir and react for 10-15 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then heat to 40-45°C and continue to stir and react for 40-50 minutes, then add ammonium persulfate, azobisisobutyronitrile and sodium dodecyl sulfate and continue to stir and react for 8-10 hours, after the reaction is completed, cool the reaction product to room temperature, then let it stand for 3-4 hours, then add it to anhydrous ethanol, then vacuum filter, place the filter cake in a vacuum drying oven, dry it at a temperature of 60-65°C for 3-5 hours, then crush it, and filter it through a 100-150 mesh sieve to obtain an oil and gas fracturing anti-salt thickener.

[0013] As a further solution of the present invention: the usage ratio of the methyl acrylate, ethylenediamine and anhydrous methanol in step 1 is 44-48 mmol: 10 mmol: 50-60 mL.

[0014] As a further scheme of the present invention: the usage ratio of the intermediate 1, allylamine, dibutyltin dilaurate, hydroquinone and anhydrous ethanol in step 2 is 10 mmol: 42-45 mmol: 0.02-0.06 g: 0.005-0.015 g: 60-80 mL.

[0015] As a further solution of the present invention: the dosage ratio of the methyl acrylate, N,N-dimethylethanolamine, hydroquinone and tetrabutyl titanate in step three is 22-26 mmol: 10 mmol: 0.008-0.016 g: 0.12-0.16 g.

[0016] As a further scheme of the present invention: the usage ratio of the intermediate 2, sodium 2-bromoethylsulfonate and anhydrous acetonitrile in step 4 is 10 mmol: 11-13 mmol: 40-50 mL.

[0017] As a further solution of the present invention: the dosage ratio of the β-cyclodextrin, deionized water and octenylsuccinic anhydride solution in step five is 10 mmol: 20-25 mL: 10-15 mL.

[0018] As a further solution of the present invention: the molar concentration of the sodium carbonate solution in step five is 2-2.5 mol / L.

[0019] As a further solution of the present invention: the octenyl succinic anhydride solution is a solution formed by dissolving octenyl succinic anhydride in anhydrous ethanol at a ratio of 10-15 mmol:10 mL.

[0020] As a further solution of the present invention: the mass fraction of the hydrochloric acid solution is 3-5%.

[0021] As a further solution of the present invention: the volume fraction of the ethanol solution is 85-90%.

[0022] As a further scheme of the present invention: the usage ratio of the acrylamide, polyene monomer, diionic monomer, cyclodextrin monomer, deionized water, ammonium persulfate, azobisisobutyronitrile and sodium dodecyl sulfate in step six is ​​13-15g: 0.5-1.7g: 5.2-9.6g: 1.2-2.6g: 100-120mL: 0.05-0.07g: 0.12-0.16g: 1-3g.

[0023] As a further solution of the present invention: the oil and gas fracturing anti-salt thickener is prepared according to the preparation method of the oil and gas fracturing anti-salt thickener.

[0024] Beneficial effects of the present invention:

[0025] The invention discloses an oil and gas fracturing anti-salt thickener and preparation method. The invention comprises the following steps: methyl acrylate and ethylenediamine are reacted, and the alkenyl group on the methyl acrylate and the amino group on the ethylenediamine undergo a M i chael addition reaction to form an intermediate 1 with a hyperbranched polyester structure. Then, the intermediate 1 and allylamine are reacted, and the ester group on the intermediate 1 and the amino group on the allylamine undergo an amidation reaction to introduce a large number of alkenyl groups to obtain a polyalkenyl monomer. Then, methyl acrylate and N,N-dimethylethanolamine are reacted, and the ester group on the methyl acrylate and the hydroxyl group on the N,N-dimethylethanolamine undergo an ester exchange reaction to introduce a tertiary amine group to obtain an intermediate 2. Then, the intermediate 2 and sodium 2-bromoethyl sulfonate are reacted, and the tertiary amine group on the intermediate 2 reacts with the bromine atom on the sodium 2-bromoethyl sulfonate to form A quaternary ammonium group is introduced, and a sulfonic acid group is introduced at the same time to obtain a diionic monomer, and then β-cyclodextrin and octenyl succinic anhydride are reacted, and the hydroxyl group on the β-cyclodextrin reacts with the anhydride group on the octenyl succinic anhydride to obtain a cyclodextrin monomer containing a carboxyl group and a cyclodextrin structure, and finally acrylamide, a polyene monomer, a diionic monomer, and a cyclodextrin monomer are used as polymerization monomers to obtain an oil and gas fracturing anti-salt thickener; multiple alkenyl groups of the polyene monomer can form cross-linking points during the polymerization process, which increases the rigidity and steric hindrance of the polymer molecular chain, and this rigid structure helps to resist the separation of salt ions. The penetration and destruction of the sub-chains can improve the salt resistance, and at high shear rates, the rigid molecular chains are not easy to break or disentangle, so they can maintain good viscosity and rheological properties; the diionic monomer contains both quaternary ammonium groups and sulfonic acid groups, the quaternary ammonium groups are positively charged, and the sulfonic acid groups are negatively charged, forming a double electric layer structure, which not only enhances the electrostatic repulsion between polymer molecular chains, but also increases the interaction between polymers and water molecules to form a stable hydration layer. The presence of the hydration layer effectively isolates the direct contact of salt ions with the polymer molecular chains, thereby improving the salt resistance and improving the The solubility and stability of the polymer are improved, and its thickening effect in a high-salinity environment is enhanced; the hydrophobic cavity of the cyclodextrin structure of the cyclodextrin monomer can encapsulate the hydrophobic part or sensitive group (such as amide group) of the polymer molecular chain to form a protective shell, which effectively isolates the destructive effects of salt ions and high-temperature environment on the polymer molecular chain, improves the stability and temperature resistance of the polymer, and the introduction of carboxyl groups increases the number of hydrophilic groups in the polymer, making it easier for the polymer to form a stable hydration layer and a more complex network structure, further enhancing the physical properties and chemical stability of the polymer.

[0026] In summary, under the synergistic effect of polyene monomers, diionic monomers and cyclodextrin monomers as modified monomers, the salt resistance, high temperature resistance, shear resistance and thickening effect of polyacrylamide thickeners are jointly improved. In oil and gas fracturing operations, it can significantly improve operating efficiency, optimize fracturing effects, and reduce problems caused by salt pollution. It is an important breakthrough in finding efficient and environmentally friendly fracturing fluid treatment technology in the field of modern oil and gas extraction. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Embodiment 1:

[0029] This embodiment is a method for preparing an oil and gas fracturing anti-salt thickener, comprising the following steps:

[0030] Step 1: 44 mmol methyl acrylate, 10 mmol ethylenediamine and 50 mL anhydrous methanol were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at a temperature of -5°C and a stirring rate of 300 r / min for 1 hour, and then the temperature was raised to 25°C and the stirring reaction was continued for 8 hours. After the reaction was completed, the reaction product was subjected to reduced pressure distillation at a temperature of 40°C to remove the solvent to obtain intermediate 1;

[0031] Step 2: 10 mmol of intermediate 1, 42 mmol of allylamine, 0.02 g of dibutyltin dilaurate, 0.005 g of hydroquinone and 60 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 25° C. and a stirring rate of 300 r / min for 20 min, and then the temperature was raised to 105° C. and the stirring reaction was continued for 3 h. After the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtered, and the filtrate was rotary evaporated to remove the solvent to obtain a polyene monomer;

[0032] Step 3: 22 mmol methyl acrylate, 10 mmol N, N-dimethylethanolamine, 0.008 g hydroquinone and 0.12 g tetrabutyl titanate were added to a three-necked flask equipped with a stirrer, a thermometer, a gas duct and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 25°C and a stirring rate of 300 r / min for 20 min, and then the mixture was heated to 85°C and stirred for 1 h, and then heated to 110°C and stirred for 6 h. After the reaction was completed, the reaction product was distilled at atmospheric pressure, and the fraction at 65°C was removed to obtain intermediate 2;

[0033] Step 4: Add 10 mmol of intermediate 2, 11 mmol of sodium 2-bromoethylsulfonate and 40 mL of anhydrous acetonitrile to a three-necked flask equipped with a stirrer, a thermometer, an air duct and a reflux condenser, introduce nitrogen protection, stir and react for 3 hours at a temperature of 45°C and a stirring rate of 300 r / min, then heat to reflux and continue stirring and reacting for 6 hours. After the reaction is completed, the reaction product is cooled to room temperature, then added to ice ether, then allowed to stand and precipitate, then vacuum filtered, the filter cake is washed twice with anhydrous ether, then placed in a vacuum drying oven, and dried at a temperature of 30°C for 3 hours to obtain a diionic monomer;

[0034] Step 5: 10 mmol β-cyclodextrin and 20 mL deionized water are added to a three-necked flask equipped with an agitator, a thermometer and an air duct, and nitrogen is introduced for protection. The reaction is stirred at a temperature of 25°C and a stirring rate of 300 r / min for 40 minutes, and then the temperature is raised to 35°C and the pH is adjusted to 8 with a sodium carbonate solution with a molar concentration of 2 mol / L. Then, 10 mL of octenyl succinic anhydride is added according to 10 mmol:10 mL of octenyl succinic anhydride solution dissolved in anhydrous ethanol to continue stirring and reacting for 8 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then the pH is adjusted to 6 with a hydrochloric acid solution with a mass fraction of 3%, and then vacuum filtered. The filter cake is washed twice with an ethanol solution with a volume fraction of 85%, and then placed in a vacuum drying oven and dried at a temperature of 50°C for 3 hours to obtain a cyclodextrin monomer;

[0035] Step six: Add 13g acrylamide, 0.5g polyene monomer, 5.2g diionic monomer, 1.2g cyclodextrin monomer and 100mL deionized water to a three-necked flask equipped with a stirrer, a thermometer and an air duct, introduce nitrogen protection, stir and react for 10min at a temperature of 25°C and a stirring rate of 300r / min, then heat to 40°C and continue stirring and reacting for 40min, then add 0.05g ammonium persulfate, 0.12g azobisisobutyronitrile and 1g sodium dodecyl sulfate and continue stirring and reacting for 8h. After the reaction, the reaction product is cooled to room temperature, then allowed to stand for 3h, then added to anhydrous ethanol, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 60°C for 3h, then crushed and filtered through a 100-mesh sieve to obtain an oil and gas fracturing anti-salt thickener.

[0036] Embodiment 2:

[0037] This embodiment is a method for preparing an oil and gas fracturing anti-salt thickener, comprising the following steps:

[0038] Step 1: 46 mmol methyl acrylate, 10 mmol ethylenediamine and 55 mL anhydrous methanol were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The reaction was stirred at a temperature of -3°C and a stirring rate of 350 r / min for 1.5 h, and then the temperature was raised to 28°C and the stirring reaction was continued for 9 h. After the reaction was completed, the reaction product was subjected to reduced pressure distillation at a temperature of 42°C to remove the solvent to obtain intermediate 1;

[0039] Step 2: 10 mmol of intermediate 1, 44 mmol of allylamine, 0.04 g of dibutyltin dilaurate, 0.01 g of hydroquinone and 70 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 28° C. and a stirring rate of 350 r / min for 25 min, and then the mixture was heated to 108° C. and stirred for 4 h. After the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtered. The filtrate was rotary evaporated to remove the solvent to obtain a polyene monomer;

[0040] Step 3: 24 mmol methyl acrylate, 10 mmol N, N-dimethylethanolamine, 0.012 g hydroquinone and 0.14 g tetrabutyl titanate were added to a three-necked flask equipped with a stirrer, a thermometer, a gas duct and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 28°C and a stirring rate of 350 r / min for 25 min, and then the mixture was heated to 88°C and stirred for 1 h, and then heated to 112°C and stirred for 7 h. After the reaction was completed, the reaction product was distilled at atmospheric pressure, and the fraction at 65°C was removed to obtain intermediate 2;

[0041] Step 4: 10 mmol of intermediate 2, 12 mmol of sodium 2-bromoethylsulfonate and 45 mL of anhydrous acetonitrile were added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen was introduced for protection. The reaction was stirred at a temperature of 48°C and a stirring rate of 350 r / min for 4 hours, and then the temperature was raised to reflux and the stirring reaction was continued for 7 hours. After the reaction was completed, the reaction product was cooled to room temperature, and then added to ice ether, and then allowed to stand and precipitate, and then vacuum filtered. The filter cake was washed twice with anhydrous ether, and then placed in a vacuum drying oven and dried at a temperature of 32°C for 4 hours to obtain a diionic monomer;

[0042] Step 5: 10 mmol β-cyclodextrin and 22 mL deionized water were added to a three-necked flask equipped with an agitator, a thermometer and an air duct, and nitrogen was introduced for protection. The reaction was stirred at a temperature of 28°C and a stirring rate of 350 r / min for 45 minutes, and then the temperature was raised to 38°C and the pH was adjusted to 8.2 with a sodium carbonate solution having a molar concentration of 2.2 mol / L, and then 12 mL of octenyl succinic anhydride was added according to 12 mmol:10 mL of octenyl succinic anhydride solution dissolved in anhydrous ethanol to continue stirring and reacting for 9 hours. After the reaction was completed, the reaction product was cooled to room temperature, and then the pH was adjusted to 6.2 with a hydrochloric acid solution having a mass fraction of 4%, and then vacuum filtered. The filter cake was washed twice with an ethanol solution having a volume fraction of 88%, and then placed in a vacuum drying oven and dried at a temperature of 52°C for 4 hours to obtain a cyclodextrin monomer;

[0043] Step six: 14g acrylamide, 1.1g polyene monomer, 7.4g diionic monomer, 1.9g cyclodextrin monomer and 110mL deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and an air duct, and nitrogen is introduced for protection. The mixture is stirred and reacted for 12min at a temperature of 28°C and a stirring rate of 350r / min, and then the mixture is heated to 42°C and stirred for 42min. Then, 0.06g ammonium persulfate, 0.14g azobisisobutyronitrile and 2g sodium dodecyl sulfate are added and stirred for 9h. After the reaction, the reaction product is cooled to room temperature, and then allowed to stand for 3.5h, and then added to anhydrous ethanol, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 62°C for 4h, then crushed and filtered through a 125-mesh sieve to obtain an oil and gas fracturing anti-salt thickener.

[0044] Embodiment 3:

[0045] This embodiment is a method for preparing an oil and gas fracturing anti-salt thickener, comprising the following steps:

[0046] Step 1: Add 48 mmol methyl acrylate, 10 mmol ethylenediamine and 60 mL anhydrous methanol into a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, introduce nitrogen protection, stir and react for 2 hours at a temperature of 0°C and a stirring rate of 400 r / min, then heat to 30°C and continue stirring and reacting for 10 hours. After the reaction is completed, the reaction product is subjected to reduced pressure distillation at a temperature of 45°C to remove the solvent to obtain intermediate 1;

[0047] Step 2: 10 mmol of intermediate 1, 45 mmol of allylamine, 0.06 g of dibutyltin dilaurate, 0.015 g of hydroquinone and 80 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at a temperature of 30° C. and a stirring rate of 400 r / min for 30 min, and then the temperature was raised to 110° C. and the stirring reaction was continued for 5 h. After the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtered, and the filtrate was rotary evaporated to remove the solvent to obtain a polyene monomer;

[0048] Step 3: 26 mmol methyl acrylate, 10 mmol N, N-dimethylethanolamine, 0.016 g hydroquinone and 0.16 g tetrabutyl titanate were added to a three-necked flask equipped with a stirrer, a thermometer, a gas duct and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 30°C and a stirring rate of 400 r / min for 30 min, and then the mixture was heated to 90°C and stirred for 1.5 h, and then heated to 115°C and stirred for 8 h. After the reaction was completed, the reaction product was distilled at atmospheric pressure, and the fraction at 65°C was removed to obtain intermediate 2;

[0049] Step 4: Add 10 mmol of intermediate 2, 13 mmol of sodium 2-bromoethylsulfonate and 50 mL of anhydrous acetonitrile to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, introduce nitrogen protection, stir and react for 5 hours at a temperature of 50°C and a stirring rate of 400 r / min, then heat to reflux and continue stirring and reacting for 8 hours. After the reaction is completed, the reaction product is cooled to room temperature, then added to ice ether, then allowed to stand and precipitate, then vacuum filtered, the filter cake is washed 3 times with anhydrous ether, then placed in a vacuum drying oven, and dried at a temperature of 35°C for 5 hours to obtain a diionic monomer;

[0050] Step 5: 10 mmol β-cyclodextrin and 25 mL deionized water are added to a three-necked flask equipped with an agitator, a thermometer and an air guide tube, and nitrogen is introduced for protection. The reaction is stirred at a temperature of 30°C and a stirring rate of 400 r / min for 50 minutes, and then the temperature is raised to 40°C and the pH is adjusted to 8.5 with a sodium carbonate solution with a molar concentration of 2.5 mol / L, and then 15 mL of octenyl succinic anhydride is added according to 15 mmol:10 mL of octenyl succinic anhydride solution dissolved in anhydrous ethanol to continue stirring and reacting for 10 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then the pH is adjusted to 6.5 with a hydrochloric acid solution with a mass fraction of 5%, and then vacuum filtered. The filter cake is washed 3 times with a 90% volume fraction ethanol solution, and then placed in a vacuum drying oven and dried at a temperature of 55°C for 5 hours to obtain a cyclodextrin monomer;

[0051] Step six: Add 15g acrylamide, 1.7g polyene monomer, 9.6g diionic monomer, 2.6g cyclodextrin monomer and 120mL deionized water to a three-necked flask equipped with a stirrer, a thermometer and an air duct, introduce nitrogen protection, stir and react for 15min at a temperature of 30°C and a stirring rate of 400r / min, then heat to 45°C and continue stirring and reacting for 50min, then add 0.07g ammonium persulfate, 0.16g azobisisobutyronitrile and 3g sodium dodecyl sulfate and continue stirring and reacting for 10h. After the reaction, the reaction product is cooled to room temperature, then allowed to stand for 4h, then added to anhydrous ethanol, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 65°C for 5h, then crushed and filtered through a 150-mesh sieve to obtain an oil and gas fracturing anti-salt thickener.

[0052] Comparative Example 1:

[0053] This comparative example is a method for preparing an oil and gas fracturing anti-salt thickener, comprising the following steps:

[0054] 15 g of acrylamide and 120 mL of deionized water were added to a three-necked flask equipped with a stirrer, a thermometer and an air duct, and nitrogen was introduced for protection. The mixture was stirred at 30°C and a stirring rate of 400 r / min for 15 min, and then the mixture was heated to 45°C and stirred for 50 min. Then, 0.07 g of ammonium persulfate, 0.16 g of azobisisobutyronitrile and 3 g of sodium dodecyl sulfate were added and stirred for 10 h. After the reaction, the reaction product was cooled to room temperature, allowed to stand for 4 h, and then added to anhydrous ethanol. The filter cake was then vacuum filtered and placed in a vacuum drying oven. It was dried at 65°C for 5 h, then crushed and filtered through a 150-mesh sieve to obtain an oil and gas fracturing anti-salt thickener.

[0055] Comparative Example 2:

[0056] This comparative example is a method for preparing an oil and gas fracturing anti-salt thickener, comprising the following steps:

[0057] Step 1: Add 48 mmol methyl acrylate, 10 mmol ethylenediamine and 60 mL anhydrous methanol into a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, introduce nitrogen protection, stir and react for 2 hours at a temperature of 0°C and a stirring rate of 400 r / min, then heat to 30°C and continue stirring and reacting for 10 hours. After the reaction is completed, the reaction product is subjected to reduced pressure distillation at a temperature of 45°C to remove the solvent to obtain intermediate 1;

[0058] Step 2: 10 mmol of intermediate 1, 45 mmol of allylamine, 0.06 g of dibutyltin dilaurate, 0.015 g of hydroquinone and 80 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at a temperature of 30° C. and a stirring rate of 400 r / min for 30 min, and then the temperature was raised to 110° C. and the stirring reaction was continued for 5 h. After the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtered, and the filtrate was rotary evaporated to remove the solvent to obtain a polyene monomer;

[0059] Step 3: 26 mmol methyl acrylate, 10 mmol N, N-dimethylethanolamine, 0.016 g hydroquinone and 0.16 g tetrabutyl titanate were added to a three-necked flask equipped with a stirrer, a thermometer, a gas duct and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 30°C and a stirring rate of 400 r / min for 30 min, and then the mixture was heated to 90°C and stirred for 1.5 h, and then heated to 115°C and stirred for 8 h. After the reaction was completed, the reaction product was distilled at atmospheric pressure, and the fraction at 65°C was removed to obtain intermediate 2;

[0060] Step 4: Add 10 mmol of intermediate 2, 13 mmol of sodium 2-bromoethylsulfonate and 50 mL of anhydrous acetonitrile to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, introduce nitrogen protection, stir and react for 5 hours at a temperature of 50°C and a stirring rate of 400 r / min, then heat to reflux and continue stirring and reacting for 8 hours. After the reaction is completed, the reaction product is cooled to room temperature, then added to ice ether, then allowed to stand and precipitate, then vacuum filtered, the filter cake is washed 3 times with anhydrous ether, then placed in a vacuum drying oven, and dried at a temperature of 35°C for 5 hours to obtain a diionic monomer;

[0061] Step 5: Add 15g acrylamide, 1.7g polyene monomer, 9.6g diionic monomer and 120mL deionized water to a three-necked flask equipped with an agitator, a thermometer and an air duct, introduce nitrogen protection, stir and react for 15min at a temperature of 30°C and a stirring rate of 400r / min, then heat to 45°C and continue stirring and reacting for 50min, then add 0.07g ammonium persulfate, 0.16g azobisisobutyronitrile and 3g sodium dodecyl sulfate and continue stirring and reacting for 10h. After the reaction, the reaction product is cooled to room temperature, then allowed to stand for 4h, then added to anhydrous ethanol, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 65°C for 5h, then crushed and filtered through a 150-mesh sieve to obtain an oil and gas fracturing anti-salt thickener.

[0062] Comparative Example 3:

[0063] This comparative example is a method for preparing an oil and gas fracturing anti-salt thickener, comprising the following steps:

[0064] Step 1: Add 48 mmol methyl acrylate, 10 mmol ethylenediamine and 60 mL anhydrous methanol into a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, introduce nitrogen protection, stir and react for 2 hours at a temperature of 0°C and a stirring rate of 400 r / min, then heat to 30°C and continue stirring and reacting for 10 hours. After the reaction is completed, the reaction product is subjected to reduced pressure distillation at a temperature of 45°C to remove the solvent to obtain intermediate 1;

[0065] Step 2: 10 mmol of intermediate 1, 45 mmol of allylamine, 0.06 g of dibutyltin dilaurate, 0.015 g of hydroquinone and 80 mL of anhydrous ethanol were added to a three-necked flask equipped with a stirrer, a thermometer, an air guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at a temperature of 30° C. and a stirring rate of 400 r / min for 30 min, and then the temperature was raised to 110° C. and the stirring reaction was continued for 5 h. After the reaction was completed, the reaction product was cooled to room temperature, and then vacuum filtered, and the filtrate was rotary evaporated to remove the solvent to obtain a polyene monomer;

[0066] Step 3: 10 mmol β-cyclodextrin and 25 mL deionized water are added to a three-necked flask equipped with an agitator, a thermometer and an air duct, and nitrogen is introduced for protection. The reaction is stirred at a temperature of 30°C and a stirring rate of 400 r / min for 50 minutes, and then the temperature is raised to 40°C and the pH is adjusted to 8.5 with a sodium carbonate solution with a molar concentration of 2.5 mol / L, and then 15 mL of octenyl succinic anhydride is added according to 15 mmol:10 mL of octenyl succinic anhydride solution dissolved in anhydrous ethanol to continue stirring and reacting for 10 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then the pH is adjusted to 6.5 with a hydrochloric acid solution with a mass fraction of 5%, and then vacuum filtered. The filter cake is washed 3 times with a 90% volume fraction ethanol solution, and then placed in a vacuum drying oven and dried at a temperature of 55°C for 5 hours to obtain a cyclodextrin monomer;

[0067] Step 4: Add 15g acrylamide, 1.7g polyene monomer, 2.6g cyclodextrin monomer and 120mL deionized water to a three-necked flask equipped with an agitator, a thermometer and an air duct, introduce nitrogen protection, stir and react for 15min at a temperature of 30°C and a stirring rate of 400r / min, then heat to 45°C and continue stirring and reacting for 50min, then add 0.07g ammonium persulfate, 0.16g azobisisobutyronitrile and 3g sodium dodecyl sulfate and continue stirring and reacting for 10h. After the reaction, the reaction product is cooled to room temperature, then allowed to stand for 4h, then added to anhydrous ethanol, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 65°C for 5h, then crushed and filtered through a 150-mesh sieve to obtain an oil and gas fracturing anti-salt thickener.

[0068] Comparative Example 4:

[0069] This comparative example is a method for preparing an oil and gas fracturing anti-salt thickener, comprising the following steps:

[0070] Step 1: 26 mmol methyl acrylate, 10 mmol N, N-dimethylethanolamine, 0.016 g hydroquinone and 0.16 g tetrabutyl titanate were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and nitrogen was introduced for protection. The mixture was stirred at 30°C and a stirring rate of 400 r / min for 30 min, and then the mixture was heated to 90°C and stirred for 1.5 h, and then heated to 115°C and stirred for 8 h. After the reaction was completed, the reaction product was distilled at atmospheric pressure, and the fraction at 65°C was removed to obtain intermediate 2;

[0071] Step 2: Add 10 mmol of intermediate 2, 13 mmol of sodium 2-bromoethylsulfonate and 50 mL of anhydrous acetonitrile to a three-necked flask equipped with a stirrer, a thermometer, an air duct and a reflux condenser, introduce nitrogen protection, stir and react for 5 hours at a temperature of 50°C and a stirring rate of 400 r / min, then heat to reflux and continue stirring and reacting for 8 hours. After the reaction is completed, the reaction product is cooled to room temperature, then added to ice ether, then allowed to stand and precipitate, then vacuum filtered, the filter cake is washed 3 times with anhydrous ether, then placed in a vacuum drying oven, and dried at a temperature of 35°C for 5 hours to obtain a diionic monomer;

[0072] Step 3: 10 mmol β-cyclodextrin and 25 mL deionized water are added to a three-necked flask equipped with an agitator, a thermometer and an air duct, and nitrogen is introduced for protection. The reaction is stirred at a temperature of 30°C and a stirring rate of 400 r / min for 50 minutes, and then the temperature is raised to 40°C and the pH is adjusted to 8.5 with a sodium carbonate solution with a molar concentration of 2.5 mol / L, and then 15 mL of octenyl succinic anhydride is added according to 15 mmol:10 mL of octenyl succinic anhydride solution dissolved in anhydrous ethanol to continue stirring and reacting for 10 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then the pH is adjusted to 6.5 with a hydrochloric acid solution with a mass fraction of 5%, and then vacuum filtered. The filter cake is washed 3 times with a 90% volume fraction ethanol solution, and then placed in a vacuum drying oven and dried at a temperature of 55°C for 5 hours to obtain a cyclodextrin monomer;

[0073] Step 4: Add 15g acrylamide, 9.6g diionic monomer, 2.6g cyclodextrin monomer and 120mL deionized water to a three-necked flask equipped with an agitator, a thermometer and an air duct, introduce nitrogen protection, stir and react for 15min at a temperature of 30°C and a stirring rate of 400r / min, then heat to 45°C and continue stirring and reacting for 50min, then add 0.07g ammonium persulfate, 0.16g azobisisobutyronitrile and 3g sodium dodecyl sulfate and continue stirring and reacting for 10h. After the reaction, the reaction product is cooled to room temperature, then allowed to stand for 4h, then added to anhydrous ethanol, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 65°C for 5h, then crushed and filtered through a 150-mesh sieve to obtain an oil and gas fracturing anti-salt thickener.

[0074] The oil and gas fracturing anti-salt thickeners of Examples 1-3 and Comparative Examples 1-4 were added to deionized water or 100 g / L sodium chloride solution to prepare a solution with a mass fraction of 1%, and tested at 30°C and 170 s -1 The apparent viscosity after shearing for 120 minutes at the shear rate is shown in the following table:

[0075]

[0076] Referring to the data in the above table, based on the comparison between Examples 1-3 and Comparative Examples 1-4, it can be known that adding polyene monomers, diionic monomers, and cyclodextrin monomers as modified monomers can significantly improve the viscosity and salt resistance of polyacrylamide.

[0077] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0078] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing an oil and gas fracturing anti-salt thickener, characterized in that: The following steps are involved: Step 1: stirring methyl acrylate, ethylenediamine and anhydrous methanol for reaction, and after the reaction is completed, distilling the reaction product under reduced pressure to obtain intermediate 1; Step 2: Stir the intermediate 1, allylamine, dibutyltin dilaurate, hydroquinone and anhydrous ethanol for reaction. After the reaction is completed, cool the reaction product, then vacuum filter it, and rotary evaporate the filtrate to obtain a polyene monomer; Step 3: stirring methyl acrylate, N,N-dimethylethanolamine, hydroquinone and tetrabutyl titanate for reaction, and after the reaction is completed, distilling the reaction product under normal pressure to obtain intermediate 2; Step 4: Stir the intermediate 2, sodium 2-bromoethylsulfonate and anhydrous acetonitrile to react. After the reaction is completed, cool the reaction product, add it to icy ether, let it stand and precipitate, and then vacuum filter it, wash and dry the filter cake to obtain a diionic monomer; Step 5: stirring β-cyclodextrin and deionized water for reaction, then adjusting the pH with sodium carbonate solution, then adding octenyl succinic anhydride solution and continuing stirring the reaction, cooling the reaction product after the reaction is completed, then adjusting the pH with hydrochloric acid solution, then vacuum filtering, washing and drying the filter cake to obtain cyclodextrin monomer; Step six: Stir acrylamide, polyene monomer, diionic monomer, cyclodextrin monomer and deionized water for reaction, then add ammonium persulfate, azobisisobutyronitrile and sodium dodecyl sulfate and continue stirring the reaction. After the reaction is completed, cool the reaction product, let it stand, then add it to anhydrous ethanol, and then vacuum filter it, dry the filter cake, and then crush and sieve it to obtain an oil and gas fracturing anti-salt thickener.

2. The method for preparing an oil and gas fracturing anti-salt thickener according to claim 1, characterized in that: The usage ratio of the methyl acrylate, ethylenediamine and anhydrous methanol in step 1 is 44-48 mmol: 10 mmol: 50-60 mL.

3. The method for preparing an oil and gas fracturing anti-salt thickener according to claim 1, characterized in that: The usage ratio of the intermediate 1, allylamine, dibutyltin dilaurate, hydroquinone and anhydrous ethanol in step 2 is 10mmol:42-45mmol:0.02-0.06g:0.005-0.015g:60-80mL.

4. The method for preparing an oil and gas fracturing anti-salt thickener according to claim 1, characterized in that: The usage ratio of the methyl acrylate, N,N-dimethylethanolamine, hydroquinone and tetrabutyl titanate in step 3 is 22-26 mmol: 10 mmol: 0.008-0.016 g: 0.12-0.16 g.

5. The method for preparing an oil and gas fracturing anti-salt thickener according to claim 1, characterized in that: The usage ratio of the intermediate 2, sodium 2-bromoethylsulfonate and anhydrous acetonitrile in step 4 is 10 mmol: 11-13 mmol: 40-50 mL.

6. The method for preparing an oil and gas fracturing anti-salt thickener according to claim 1, characterized in that: The dosage ratio of the β-cyclodextrin, deionized water and octenyl succinic anhydride solution in step 5 is 10 mmol: 20-25 mL: 10-15 mL.

7. The method for preparing an oil and gas fracturing anti-salt thickener according to claim 1, characterized in that: The molar concentration of the sodium carbonate solution in step 5 is 2-2.5 mol / L; the octenyl succinic anhydride solution is a solution formed by dissolving octenyl succinic anhydride in anhydrous ethanol at a ratio of 10-15 mmol:10 mL; and the mass fraction of the hydrochloric acid solution is 3-5%.

8. The method for preparing an oil and gas fracturing anti-salt thickener according to claim 1, characterized in that: The usage ratio of the acrylamide, polyene monomer, diionic monomer, cyclodextrin monomer, deionized water, ammonium persulfate, azobisisobutyronitrile and sodium dodecyl sulfate in step six is ​​13-15g: 0.5-1.7g: 5.2-9.6g: 1.2-2.6g: 100-120mL: 0.05-0.07g: 0.12-0.16g: 1-3g.

9. An oil and gas fracturing anti-salt thickener, characterized in that: The oil and gas fracturing salt-resistant thickener is prepared according to the preparation method of the oil and gas fracturing salt-resistant thickener according to any one of claims 1 to 8.

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