Betaine type double-tailed hydrophobic association polymer fracturing thickening agent and preparation method thereof

Abstract

The invention relates to a betaine type double-tailed hydrophobic association polymer fracturing thickening agent and a preparation method thereof. The thickening agent is prepared by the following steps: copolymerizing four monomers, namely acrylamide, 2-allyl methylamino sodium ethanesulfonate, methyl diallyl hydroxypropyl sulfobetaine and double-tailed long-chain alkyl allyl sulfoethyl betaine to form gel, chopping, hydrolyzing, neutralizing and purifying. The preparation method comprises the following steps: firstly adding distilled water, adding acrylamide, 2-allylmethylamino sodium ethanesulfonate, methyldiallyl hydroxypropyl sulfobetaine and other remaining raw materials, adjusting the total concentration, introducing N2 to remove oxygen, adding an initiator, reacting to prepare gel, chopping the gel, and hydrolyzing to obtain the water-soluble polymer. The fracturing thickening agent has good water solubility and shows good salt resistance in mixed saline water with the mineralization degree larger than or equal to 30000 mg / L, a prepared linear solution and jelly formed after crosslinking have high viscosity retention capacity at the temperature of 150 DEG C and the shearing rate of 170 s <-1 >, and the actual construction requirement for fracturing yield increase with the on-site mineralization degree larger than or equal to 30000 mg / L is met.

Description

Technical Field

[0001] The present invention relates to an oil and gas production-increasing additive, in particular to a hydrophobically associating polymer fracturing thickener with a betaine structure hydrophobic group, specifically a betaine type double-tailed hydrophobically associating polymer fracturing thickener. The present invention also relates to a preparation method of the betaine type double-tailed hydrophobically associating polymer fracturing thickener. Background Art

[0002] As an important reservoir transformation technology, hydraulic fracturing plays a very important role in increasing oil and gas production. With the development of the oil and gas industry around the world, oil and gas resources with high oil and gas content and low development difficulty are becoming less and less, and there are more and more "low pressure, low production, and low permeability" oil and gas fields. In particular, in recent years, many tight oil and gas reservoirs and shale oil and gas reservoirs have been found. In the early stage of production, the production is very low or even zero, and they need to be transformed by fracturing to have a certain production value. On the other hand, with the continuous deepening of exploration and development, the temperature of newly developed oil and gas wells exceeds 150℃, and the mineralization of formation water is also relatively high. There is an urgent need to develop clean fracturing fluids that are resistant to temperature, salt, and shear.

[0003] Currently, guar gum-based water-based fracturing fluid is widely used in fracturing operations. This plant gum fracturing fluid has a good thickening effect, but its disadvantages are also prominent: high insoluble content, incomplete gel breaking, large amount of residue that can easily cause damage to the formation, and the cost is increasing day by day.

[0004] Viscoelastic surfactant (VES) fracturing fluid is a new type of fracturing fluid system that uses small molecule surfactants as thickeners. Compared with conventional fracturing fluids, fracturing fluids with this type of thickener have the characteristics of low residue content and less reservoir damage, so they are also called "clean fracturing fluids". According to the different functional groups in the surfactant thickener molecules, they are mainly divided into cationic, anionic and non-ionic types. At present, the main reason restricting the widespread use of this type of thickener is its poor temperature resistance and high production cost, and low market benefits.

[0005] Synthetic polymers: Common ones include polyacrylamide, partially hydrolyzed polyacrylamide, methylene polyacrylamide, etc. Compared with guar gum and cellulose derivatives, this type of polymer has stronger viscosity-increasing ability, strong antibacterial ability and good thermal stability. At the same time, the residue content after degelling is low, and it is easy to flow back, which can reduce the damage to oil and gas reservoirs. This type of polymer fracturing fluid usually uses anionic polyacrylamide as a thickener. Anionic polyacrylamide has a certain viscosity-increasing effect, but its salt resistance is poor. Although cationic polyacrylamide has greatly improved the salt resistance of polyacrylamide, it still has problems such as water solubility and low viscosity.

[0006] Related patent literature: CN109536154A discloses a fracturing thickener and a preparation method thereof for realizing the reuse of oilfield fracturing flowback fluid. The raw materials of the former include acrylamide, dimethyldiallyl ammonium chloride, acrylic acid, 2-acrylamide-2-methylpropane sulfonic acid, glycerol, sodium dodecyl polyoxyethylene ether sulfate, hexadecyl trimethyl ammonium chloride, sodium hydroxide and deionized water. The above raw materials are polymerized under the conditions of catalyst and redox initiator to obtain the product. The preparation method of the technical scheme is simple, and the molecular structure of the obtained fracturing thickener has multiple functional side chains, which have the characteristics of easy solubility of fracturing fluid, salt resistance and high temperature resistance, shear resistance, good sand carrying performance, low friction, easy flowback and low residue. At the same time, fracturing flowback fluid can be added to the thickener to prepare fracturing fluid, so as to realize the reuse of fracturing flowback fluid, reduce the cost of flowback fluid sewage treatment, and improve the environmental pollution caused by the flowback fluid. CN104087283A discloses a fracturing thickener with rapid dispersion and viscosity increase under acidic conditions and a preparation method thereof. The thickener is obtained by a three-step etherification reaction of guar gum under alkaline conditions, which are respectively chloroalkyl alcohol, alkylene oxide and anion etherification modification reaction treatment, followed by acid neutralization, alcohol water washing, solid-liquid separation, rolling and crushing, and drying. The technical solution provides a guar gum fracturing thickener with rapid dispersion and viscosity increase, strong thickening ability, temperature resistance, and shear resistance. The thickener reaches more than 90% of the final viscosity in 3 minutes under acidic conditions, is ready for use, meets the requirements of on-site continuous mixing, greatly saves liquid costs, and improves production efficiency.

[0007] The above technical solution does not solve the problem that the existing plant gum fracturing fluid produces high residues that damage the formation, and the problem that ordinary synthetic polymers have poor temperature and salt resistance in high-mineralization (mineralization ≥ 30000 mg / L) brine. Summary of the invention

[0008] The purpose of the present invention is to provide a betaine type double-tailed hydrophobic associating polymer fracturing thickener, which has good performance and good viscosity increasing ability at low concentration. The prepared polymer linear solution and the cross-linked gel have good viscosity retention ability and good shear resistance under high temperature, high salinity and high shear rate, can play a good role in seam forming ability and sand carrying ability in the fracturing construction process, and can meet the technical requirements of the widely used fracturing thickeners on the market, thereby ensuring the smooth construction of oil and gas production increase in high-temperature and high-salinity oil and gas reservoirs, so as to solve the problems that the existing plant gum fracturing fluid produces high residues that damage the formation, and the common synthetic polymer has poor temperature and salt resistance in high-salinity (mineralization ≥30000mg / L) brine.

[0009] To this end, another object of the present invention is to provide a method for preparing a betaine-type double-tailed hydrophobically associating polymer fracturing thickener.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0011] A betaine-type double-tailed hydrophobically associating polymer fracturing thickener (or a water-soluble double-tailed long-chain hydrophobically associating polymer fracturing thickener with a betaine structure), the technical scheme of which is that it is composed of acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, methyl diallyl hydroxypropyl sulfobetaine MDAHPSBA and a hydrophobic monomer with a betaine structure, double-tailed long-chain alkyl allyl sulfoethyl betaine DC n The four monomers of ASBA are copolymerized to form a gel. After the reaction is completed, the gel is chopped and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, it is neutralized and purified to obtain the final product. The structural formula of the polymer fracturing thickener is as follows:

[0012]

[0013] In the above structural formula, x, y, z, p, q are the molar percentage ranges of the structural units: x = 67.5% to 83.9%, y = 10% to 20%, z = 5% to 10%, p = 1% to 2%, q = 0.1% to 0.5%, x + y + z + p + q = 100%. Where n = 8, 10, 12, 14, and the long-chain alkyl group is an alkane with the same carbon number.

[0014] In the betaine-type double-tailed hydrophobic associating polymer fracturing thickener, the molar fractions of each monomer are as follows (i.e., the fracturing thickener is made of the following molar fractions of monomers): 87.5-93.9 parts of acrylamide AM, 5-10 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-2 parts of methyldiallylhydroxypropylsulfobetaine MDAHPSBA, and 1-2 parts of double-tailed long-chain alkyl allylsulfoethylbetaine DC having a betaine structure hydrophobic monomer. n ASBA 0.1~0.5 parts.

[0015] The preparation method of the above-mentioned 2-allylmethylaminoethanesulfonic acid sodium AMES-Na comprises the following process steps: in a (500mL) three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding an appropriate amount of anhydrous ethanol as a solvent, adding 65-95g of 2-chloroethylsulfonic acid sodium at room temperature (temperature is 23-25°C), then slowly adding 30-43g of N-methylallylamine under stirring, adding 0.15-0.21g of inhibitor methylhydroquinone, and charging 32-47g of an acid binding agent wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 20-25 hours, and removing the solvent and excess N-methylallylamine by reduced pressure distillation using a rotary evaporator to obtain 2-allylmethylaminoethanesulfonic acid sodium AMES-Na.

[0016] The preparation method of the salt-resistant monomer methyl diallyl hydroxypropyl sulfobetaine MDAHPSBA comprises the following process steps: adding an appropriate amount of anhydrous ethanol as a solvent to a (500 mL) three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, adding 75 to 110 g of sodium 3-chloro-2-hydroxypropane sulfonate (i.e., 3-chloro-2-hydroxypropane sulfonic acid sodium salt) at room temperature (temperature of 23 to 25° C.) and turning on magnetic stirring, then slowly adding 45 to 65 g of N-methyl diallylamine under stirring, adding 0.17 to 0.25 g of inhibitor methyl hydroquinone, raising the temperature to reflux, reacting at a constant temperature for 10 to 12 hours, using a rotary evaporator to remove the solvent and excess N-methyl diallylamine by reduced pressure distillation, and then using acetone for separation and purification to obtain methyl diallyl hydroxypropyl sulfobetaine MDAHPSBA.

[0017] The above hydrophobic monomer with betaine structure double-tail long-chain alkyl allyl sulfoethyl betaine DC nThe preparation method of ASBA comprises the following process steps: (1) adding an appropriate amount of hexafluoroisopropanol as a solvent (using hexafluoroisopropanol can improve selectivity and yield) to a three-necked flask (500 mL) equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 35 to 50 g of a long-chain alkylamine at room temperature (temperature of 23 to 25° C.) and with magnetic stirring on, then slowly adding 30 to 40 g of sodium 2-chloroethylsulfonate under stirring, and charging the Soxhlet extractor with a reflux condenser and a magnetic rotor; 13-20 g of the acid-binding agent wrapped with filter paper is heated to reflux, and reacted at constant temperature for 30-35 hours, and then the solvent is removed by vacuum distillation using a rotary evaporator, and the long-chain alkylamine is separated by distilled water, and the filtrate is recrystallized to obtain a long-chain alkyl sulfonethylamine; (2) In a three-necked flask (500 mL) equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, an appropriate amount of anhydrous ethanol is added as a solvent, and 40-60% of the ethanol is added at room temperature (temperature is 23-25° C.) and magnetic stirring is turned on. g of chlorinated long-chain alkane, then slowly add 60-90 g of long-chain alkyl sulfonethyl amine under stirring, put 17-26 g of acid binding agent wrapped with filter paper into the Soxhlet extractor, raise the temperature to reflux, react at constant temperature for 20-25 hours, remove the solvent by vacuum distillation using a rotary evaporator, and separate and purify with petroleum ether to obtain a double-tailed long-chain alkyl sulfonethyl tertiary amine; (3) add an appropriate amount of anhydrous ethanol to a three-necked flask (500 mL) equipped with a thermometer, a reflux condenser and a magnetic rotor. As a solvent, 12 to 20 g of allyl chloride is added at a temperature of 5 to 8 ° C and under magnetic stirring, and then 70 to 100 g of double-tailed long-chain alkyl sulfoethyl tertiary amine is slowly added under stirring, and 0.12 to 0.20 g of methyl hydroquinone as an inhibitor is added, and the temperature is raised to reflux. After constant temperature reaction for 10 to 12 hours, the solvent and excess allyl chloride are removed by reduced pressure distillation using a rotary evaporator, and recrystallization is performed using acetone to obtain a hydrophobic monomer double-tailed long-chain alkyl allyl sulfoethyl betaine DC having a betaine structure. n ASBA.

[0018] The preparation method of the betaine type double-tailed hydrophobic associating polymer fracturing thickener comprises the following process steps: firstly, 1000-1500 mole parts of distilled water are added into a reactor, and 87.5-93.9 mole parts of acrylamide AM, 5-10 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-2 mole parts of methyldiallylhydroxypropyl sulfobetaine MDAHPSBA, an emulsifier, a hydrophobic monomer with a betaine structure and a double-tailed long-chain alkyl allyl sulfoethyl betaine DC are sequentially added under stirring. nASBA 0.1-0.5 molar parts, and then distilled water is added to control the total mass percentage concentration of the reaction monomers to be between 15% and 30% (the total mass percentage concentration of the reaction monomers is the mass percentage concentration of the above four monomers combined, the same below), and after stirring evenly (stirring the solution until the solution is a nearly transparent homogeneous system), N2 is passed for 30-35 minutes; then an initiator is added, and N2 is continued to be passed, and the reaction is carried out for 4-10 hours under nitrogen protection and 30-60°C; after the reaction, the obtained gel-like product, i.e., the copolymer, is chopped, sodium carbonate solution is added, and then distilled water is added to dilute the copolymer to a mass percentage concentration of 5%-8%, and hydrolysis reaction is carried out at a temperature of 85-90°C for 1.5-2.5 hours. After the reaction, dilute hydrochloric acid is used for neutralization, and the product is washed with anhydrous ethanol, and then the product is crushed, dried, and sieved to obtain a betaine type double-tailed hydrophobic associating polymer fracturing thickener.

[0019] In the above technical scheme, the preferred technical scheme may be that the emulsifier may be hexadecyl trimethyl ammonium bromide, and the amount of hexadecyl trimethyl ammonium bromide added is 0.06% to 0.1% of the total mass of the reaction solution; the amount of the initiator added is 0.05% to 0.2% of the total mass of the reaction monomers, and the total mass of the reaction monomers is the total mass of the four monomers mentioned above; the amount of the sodium carbonate solution added is 45% to 75% of the weight (mass) of the acrylamide monomer, and the sodium carbonate solution is a sodium carbonate aqueous solution with a mass percentage concentration of 15% to 20%; the mass fraction of the dilute hydrochloric acid is 5%. The above initiator may be a composite initiator, including an oxidation-reduction system initiator and a water-soluble azo initiator. In the oxidation-reduction system initiator, the oxidant is potassium persulfate or ammonium persulfate, the reductant is sodium bisulfite, and the molar ratio of the oxidant to the reductant is 1:1-1.5; the water-soluble azo initiator is one or more of azobisisobutylamidine hydrochloride V-50, azobisisobutylimidazoline hydrochloride VA-044, and azobis(N-2-carboxyethyl-2-methylpropionamidine) hydrate VA-057, and the ratio is arbitrary when combined; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1-2. The above-mentioned acid binding agent can be potassium carbonate or sodium carbonate, etc.

[0020] In the above technical solution, the preferred technical solution can also be that the hydrophobic monomer with betaine structure double-tail long-chain alkyl allyl sulfoethyl betaine DC n In ASBA, the long-chain alkyl group can be dodecyl; the long-chain alkylamine in step (1) is dodecylamine, and the chlorinated long-chain alkane in step (2) is chlorododecane (i.e., 1-chlorododecane); the final product in step (3) is a hydrophobic monomer having a betaine structure, didodecyl allyl sulfoethyl betaine DC 12 ASBA.

[0021] In the above technical solution, the preferred technical solution can also be that the hydrophobic monomer with betaine structure double-tail long-chain alkyl allyl sulfoethyl betaine DC n In ASBA, the long-chain alkyl group can be selected from decyl groups; the long-chain alkylamine in step (1) is decylamine, and the chlorinated long-chain alkane in step (2) is chlorodecane (i.e., 1-chlorodecane); and the final product in step (3) is a hydrophobic monomer having a betaine structure, didecyl allyl sulfoethyl betaine DC 10 ASBA.

[0022] Among the above technical solutions, a preferred technical solution may also be Embodiment 1 of the present invention.

[0023] The polymer fracturing thickener of the present invention is composed of acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, methyldiallylhydroxypropylsulfonyl betaine MDAHPSBA and a hydrophobic monomer with a betaine structure and a double-tailed long-chain alkyl allyl sulfonyl betaine DC n ASBA four monomers copolymerize to form gel, after the reaction is completed, the gel is chopped up, hydrolyzed in an appropriate amount of sodium carbonate solution, and purified after hydrolysis to obtain the final product. Preparation method: first add an appropriate amount of distilled water to the reactor, then add acrylamide, 2-allylmethylaminoethylsulfonic acid sodium, methyldiallylhydroxypropylsulfobetaine, hexadecyltrimethylammonium bromide, and betaine structure hydrophobic monomer double tail long chain alkyl allyl sulfoethyl betaine in sequence, then add distilled water, stir evenly, pass N2 to deoxygenate, then add initiator, react and hydrolyze at a certain temperature to obtain temperature and salt resistant fracturing thickener. The present invention introduces a double-tailed hydrophobic chain structure into the polymer chain, which improves the polymer's viscosity-increasing ability and temperature and salt resistance. By introducing a double-tailed long chain structure, the molecular chain rigidity can be increased as well as its hydrophobicity, thereby improving the polymer's thermal stability and shear resistance. The sulfonic acid group is introduced to improve the polymer's salt resistance, meeting the actual construction needs of oil and gas production increase at a site with a mineralization of ≥30,000 mg / L. The polymer fracturing thickener prepared by the present invention has good water solubility and exhibits good salt resistance in mixed brine with a mineralization of ≥30,000 mg / L; the prepared linear solution has a water solubility of 150°C and a shear rate of 170s -1 The viscosity retention capacity of the cross-linked gel was higher at 190℃ and shear rate of 170s. -1 The viscosity remains over 300 mPa·s.

[0024] Compared with the prior art, the present invention has the following effects: (1) a double-tail long chain structure is introduced into the hydrophobic monomer, so that the rigidity of the polymer molecular chain is greatly enhanced and the hydrophobic association between the copolymer molecules is increased, thereby greatly increasing the viscosity and rheological properties of the polymer and greatly improving the heat resistance of the polymer; (2) a cyclic quaternary ammonium salt structure is formed after the introduction of the diallyl group, thereby improving the rigidity of the polymer molecular chain, thereby improving the temperature resistance, salt resistance and shear resistance of the polymer; (3) the polymer exhibits good temperature resistance, salt resistance and shear resistance.

[0025] Referring to the experimental (test) part of the present invention below, in summary, the present invention provides a (water-soluble) betaine type double-tailed hydrophobic associating polymer fracturing thickener, which has good performance and good viscosity increasing ability at low concentrations. The prepared polymer linear solution and the cross-linked gel have good viscosity retention ability and good shear resistance at high temperature, high mineralization and high shear rate, and play a good fracture-making ability and sand-carrying ability in the fracturing construction process, and can meet the technical requirements of the widely used fracturing thickeners on the market, thereby ensuring the smooth construction of oil and gas production increase in high-temperature and high-mineralization oil and gas reservoirs, and solving the problems of high residues that damage the formation produced by the existing plant gum fracturing fluid, and poor temperature and salt resistance of ordinary synthetic polymers in high-mineralization (mineralization ≥ 30000 mg / L) brine. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the infrared spectrum of the copolymer (fracturing thickener) synthesized (prepared) in Example 1 of the present invention.

[0027] Figure 2 Graph showing the relationship between the apparent viscosity of the copolymers (fracturing thickeners) synthesized in Examples 1 and 2 of the present invention and the changes in concentration.

[0028] Figure 3 The figure is a relationship diagram of the apparent viscosity of the copolymer (fracturing thickener) synthesized in Example 1 and Example 2 of the present invention as a function of the salinity.

[0029] Figure 4 This is a graph showing the relationship between the apparent viscosity of the copolymer (fracturing thickener) synthesized in Example 2 of the present invention and the shear time.

[0030] Figure 5 The figure is a relationship diagram of the apparent viscosity of the jelly formed by the copolymers (fracturing thickeners) synthesized in Examples 1 and 2 of the present invention as a function of temperature. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described in conjunction with the embodiments below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on this embodiment, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0032] Example 1: The (water-soluble) betaine-type double-tailed hydrophobic associating polymer fracturing thickener of the present invention is composed of acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, methyldiallylhydroxypropyl sulfobetaine MDAHPSBA and a betaine-structured hydrophobic monomer double-tailed long-chain alkyl allyl sulfoethyl betaine DC n The four monomers of ASBA are copolymerized to form a gel. After the reaction is completed, the gel is chopped and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, it is neutralized and purified to obtain the final product. The structural formula of the polymer fracturing thickener is as follows:

[0033]

[0034] In the above structural formula, x, y, z, p, and q are the molar percentage ranges of the structural units: x = 67.5% to 83.9%, y = 10% to 20%, z = 5% to 10%, p = 1% to 2%, q = 0.1% to 0.5%, x + y + z + p + q = 100%. Wherein n = 8, 10, 12, 14, in this embodiment, n = 10.

[0035] In the betaine-type double-tailed hydrophobic associating polymer fracturing thickener, the molar fractions of each monomer added are as follows: 90.13 parts of acrylamide AM, 8.31 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1.31 parts of methyldiallylhydroxypropylsulfobetaine MDAHPSBA, and 1.31 parts of double-tailed long-chain alkyl allyl sulfoethyl betaine DC having a betaine structure hydrophobic monomer. n ASBA 0.25 parts.

[0036] The preparation method of the above-mentioned 2-allylmethylaminoethanesulfonic acid sodium AMES-Na comprises the following process steps: adding 180 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 74 g of sodium 2-chloroethylsulfonate at 25° C., then slowly adding 33 g of N-methylallylamine under stirring, adding 0.19 g of methylhydroquinone as an inhibitor, and charging 37 g of potassium carbonate wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 23 hours, and removing the solvent and excess N-methylallylamine by reduced pressure distillation using a rotary evaporator to obtain 2-allylmethylaminoethanesulfonic acid sodium AMES-Na.

[0037] The preparation method of the salt-resistant monomer methyl diallyl hydroxypropyl sulfobetaine MDAHPSBA comprises the following process steps: adding 200 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, adding 83 g of sodium 3-chloro-2-hydroxypropane sulfonate at a temperature of 25° C. and with magnetic stirring turned on, then slowly adding 50 g of N-methyl diallylamine under stirring, adding 0.19 g of inhibitor methyl hydroquinone, raising the temperature to reflux, reacting at a constant temperature for 11 hours, using a rotary evaporator to remove the solvent and excess N-methyl diallylamine by reduced pressure distillation, and then using acetone for separation and purification to obtain methyl diallyl hydroxypropyl sulfobetaine MDAHPSBA.

[0038] The above hydrophobic monomer with betaine structure double-tail long-chain alkyl allyl sulfoethyl betaine DC n In ASBA, the long-chain alkyl is dodecyl; in the following step (1), the long-chain alkylamine is dodecylamine; in the following step (2), the chlorinated long-chain alkane is chlorododecane (i.e., 1-chlorododecane); in the following step (3), the final product is a hydrophobic monomer having a betaine structure, didodecyl allyl sulfoethyl betaine DC 12 ASBA.

[0039] The above-mentioned hydrophobic monomer having a betaine structure, didodecyl allyl sulfoethyl betaine DC 12The preparation method of ASBA comprises the following process steps: (1) adding 180 mL of hexafluoroisopropanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 43 g of dodecylamine at a temperature of 25° C. and with magnetic stirring on, then slowly adding 36 g of sodium 2-chloroethylsulfonate under stirring, placing 15 g of potassium carbonate (acid binding agent) wrapped with filter paper in the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 34 hours, removing the solvent by reduced pressure distillation using a rotary evaporator, separating the dodecylamine with distilled water, and recrystallizing the filtrate to obtain dodecylsulfoethylamine; (2) adding 200 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 50 g of chlorododecane at a temperature of 25° C. and with magnetic stirring on, Then, 79 g of dodecylsulfoethylamine was slowly added under stirring, 21 g of potassium carbonate (acid binding agent) wrapped with filter paper was placed in a Soxhlet extractor, the temperature was raised to reflux, and after isothermal reaction for 22 hours, the solvent was removed by vacuum distillation using a rotary evaporator, and petroleum ether was used for separation and purification to obtain didodecylsulfoethyl tertiary amine; (3) In a 500 mL three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, 180 mL of anhydrous ethanol was added as a solvent, 16 g of allyl chloride was added at a temperature of 5° C. and with magnetic stirring turned on, then 85 g of didodecylsulfoethyl tertiary amine was slowly added under stirring, 0.13 g of methyl hydroquinone as an inhibitor was added, the temperature was raised to reflux, and after isothermal reaction for 11 hours, the solvent and excess allyl chloride were removed by vacuum distillation using a rotary evaporator, and recrystallization was performed using acetone to obtain didodecyl allyl sulfoethyl betaine DC, a hydrophobic monomer having a betaine structure. 12 ASBA.

[0040] The preparation method of the betaine type double-tailed hydrophobic associating polymer fracturing thickener (i.e., partially hydrolyzed AM / AMES / MDAHPSBA / DC 12 The synthesis process of ASBA hydrophobically associating polymer fracturing thickener comprises the following process steps: firstly, 1000 mole parts of distilled water are added into a reactor, and then 90.13 mole parts of acrylamide AM, 8.31 mole parts of 2-allylmethylaminoethylsulfonate AMES-Na, 1.31 mole parts of methyldiallylhydroxypropylsulfobetaine MDAHPSBA, emulsifier hexadecyltrimethylammonium bromide (the amount of hexadecyltrimethylammonium bromide added is 0.08% of the total mass of the reaction solution), and hydrophobic monomer didodecylallylsulfoethylbetaine DC having a betaine structure are added in sequence under stirring. 12ASBA 0.25 mole part, and then distilled water is added to control the total mass percentage concentration of the reaction monomers to 20%. After stirring evenly, N2 is passed for 30 minutes; then 0.10% of the total mass of the reaction monomers is added (the total mass of the reaction monomers is the total mass of the four monomers mentioned above), and N2 is continued to be passed, and the reaction is carried out under nitrogen protection and 45°C for 7 hours; after the reaction, the obtained gel product, i.e., the copolymer, is chopped up and a sodium carbonate solution is added (the amount of the sodium carbonate solution added is 55% of the weight of the acrylamide monomer, and the sodium carbonate solution is a sodium carbonate aqueous solution with a mass percentage concentration of 15%); then distilled water is added to dilute the copolymer to a mass percentage concentration of 5%, and a hydrolysis reaction is carried out at a temperature of 90°C for 2.5 hours. After the reaction, 5% dilute hydrochloric acid is used for neutralization, and the product is washed with anhydrous ethanol, and then the product is crushed, dried, and sieved to obtain a betaine-type double-tailed hydrophobic associating polymer fracturing thickener (that is, partially hydrolyzed AM / AMES / MDAHPSBA / DC 12 ASBA tetrapolymer fracturing thickener, that is, the polymer fracturing thickener of the present invention).

[0041] The above-mentioned initiator is a composite initiator, including an oxidation-reduction system initiator and a water-soluble azo initiator. In the above-mentioned oxidation-reduction system initiator, the oxidant is potassium persulfate, the reductant is sodium bisulfite, and the molar ratio of the oxidant to the reductant is 1:1; the above-mentioned water-soluble azo initiator is a combination of azobisisobutylimidazoline hydrochloride (VA-044) and azobisisobutylamidine hydrochloride (V-50), and the mass ratio thereof is 1:1; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1.7.

[0042] For the convenience of the experimental part of the present invention, the above-mentioned partial hydrolysis of AM / AMES / MDAHPSBA / DC 12 ASBA tetrapolymer fracturing thickener is abbreviated as PAAAMD (ie, the polymer fracturing thickener of the present invention).

[0043] Example 2: The betaine-type double-tailed hydrophobic associating polymer fracturing thickener of the present invention is composed of acrylamide AM, 2-allylmethylaminoethylsulfonate AMES-Na, methyldiallylhydroxypropylsulfonate MDAHPSBA and a betaine-structured hydrophobic monomer double-tailed long-chain alkyl allyl sulfonate DC n The four monomers of ASBA are copolymerized to form a gel. After the reaction is completed, the gel is chopped and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, it is neutralized and purified to obtain the final product. The structural formula of the polymer fracturing thickener is the same as that of Example 1.

[0044] In the above structural formula, x, y, z, p, and q are the molar percentage ranges of the structural units: x = 67.5% to 83.9%, y = 10% to 20%, z = 5% to 10%, p = 1% to 2%, q = 0.1% to 0.5%, x + y + z + p + q = 100%. Wherein n = 8, 10, 12, 14, in this embodiment, n = 8.

[0045] In the betaine-type double-tailed hydrophobic associating polymer fracturing thickener, the molar fractions of each monomer added are as follows: 90.70 parts of acrylamide AM, 7.36 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1.57 parts of methyldiallylhydroxypropyl sulfobetaine MDAHPSBA, and 1.57 parts of double-tailed long-chain alkyl allyl sulfoethyl betaine DC having a betaine structure hydrophobic monomer. n ASBA 0.37 parts.

[0046] The preparation method of the above-mentioned 2-allylmethylaminoethanesulfonic acid sodium AMES-Na comprises the following process steps: adding 200 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 80 g of sodium 2-chloroethylsulfonate at 25° C., then slowly adding 36 g of N-methylallylamine under stirring, adding 0.21 g of methylhydroquinone as an inhibitor, and charging 40 g of potassium carbonate wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 23 hours, and removing the solvent and excess N-methylallylamine by reduced pressure distillation using a rotary evaporator to obtain 2-allylmethylaminoethanesulfonic acid sodium AMES-Na.

[0047] The preparation method of the salt-resistant monomer methyl diallyl hydroxypropyl sulfobetaine MDAHPSBA comprises the following process steps: adding 200 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, adding 95 g of sodium 3-chloro-2-hydroxypropane sulfonate at a temperature of 25° C. and with magnetic stirring turned on, then slowly adding 57 g of N-methyl diallylamine under stirring, adding 0.22 g of inhibitor methyl hydroquinone, raising the temperature to reflux, reacting at a constant temperature for 12 hours, removing the solvent and excess N-methyl diallylamine by reduced pressure distillation using a rotary evaporator, and then separating and purifying using acetone to obtain methyl diallyl hydroxypropyl sulfobetaine MDAHPSBA.

[0048] The above hydrophobic monomer with betaine structure double-tail long-chain alkyl allyl sulfoethyl betaine DC nIn ASBA, the long-chain alkyl group can be selected from decyl groups; the long-chain alkylamine in step (1) is decylamine, and the chlorinated long-chain alkane in step (2) is chlorodecane (i.e., 1-chlorodecane); and the final product in step (3) is a hydrophobic monomer having a betaine structure, didecyl allyl sulfoethyl betaine DC 10 ASBA.

[0049] The above hydrophobic monomer having a betaine structure, didecyl sulfoethyl allyl betaine DC 10 The preparation method of ASBA comprises the following process steps: (1) adding 180 mL of hexafluoroisopropanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 40 g of decylamine at a temperature of 25° C. and with magnetic stirring on, then slowly adding 40 g of sodium 2-chloroethylsulfonate under stirring, placing 16 g of anhydrous sodium carbonate (acid binding agent) wrapped with filter paper in the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 33 hours, removing the solvent by reduced pressure distillation using a rotary evaporator, separating the decylamine with distilled water, and recrystallizing the filtrate to obtain decylsulfoethylamine; (2) adding 200 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 43 g of chlorodecane at a temperature of 25° C. and with magnetic stirring on. , then slowly add 72g of decylsulfoethylamine under stirring, load 20g of potassium carbonate (acid binding agent) wrapped with filter paper into the Soxhlet extractor, raise the temperature to reflux, react at constant temperature for 22 hours, remove the solvent by vacuum distillation using a rotary evaporator, and separate and purify with petroleum ether to obtain didecylsulfoethyl tertiary amine; (3) add 200mL of anhydrous ethanol as solvent to a 500mL three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, add 14.5g of allyl chloride at a temperature of 5°C and with magnetic stirring turned on, then slowly add 90g of didecylsulfoethyl tertiary amine under stirring, add 0.15g of methyl hydroquinone as an inhibitor, raise the temperature to reflux, react at constant temperature for 12 hours, remove the solvent and excess allyl chloride by vacuum distillation using a rotary evaporator, and recrystallize with acetone to obtain didecyl allyl sulfoethyl betaine DC, a hydrophobic monomer with a betaine structure. 10 ASBA.

[0050] The preparation method of the betaine type double-tailed hydrophobic associating polymer fracturing thickener comprises the following process steps: firstly, 1200 mole parts of distilled water are added into a reactor, and 90.70 mole parts of acrylamide AM, 7.36 mole parts of 2-allylmethylaminoethylsulfonate AMES-Na, 1.57 mole parts of methyldiallylhydroxypropylsulfobetaine MDAHPSBA, emulsifier hexadecyltrimethylammonium bromide (the amount of hexadecyltrimethylammonium bromide added is 0.1% of the total mass of the reaction solution), hydrophobic monomer didecylallylsulfoethylbetaine DC having a betaine structure are added in sequence under stirring. 10 ASBA 0.37 mole parts, and then distilled water is added to control the total mass percentage concentration of the reaction monomers to 20%. After stirring, N2 is passed for 30 minutes; then 0.15% of the total mass of the reaction monomers is added (the total mass of the reaction monomers is the total mass of the four monomers mentioned above), and N2 is continued to be passed, and the reaction is carried out under nitrogen protection and 40° C. for 9 hours; after the reaction, the obtained gel-like product, i.e., the copolymer, is chopped up and a sodium carbonate solution is added (the amount of the sodium carbonate solution added is 50% of the weight of the acrylamide monomer, and the sodium carbonate solution is a sodium carbonate aqueous solution with a mass percentage concentration of 15%); then distilled water is added to dilute the copolymer to a mass percentage concentration of 5%, and the hydrolysis reaction is carried out at a temperature of 90° C. for 2.0 hours. After the reaction, it is neutralized with dilute hydrochloric acid with a mass fraction of 5%, and the product is washed with anhydrous ethanol, and then the product is crushed, dried, and sieved to obtain a betaine-type double-tailed hydrophobic associating polymer fracturing thickener (that is, partially hydrolyzed AM / AMES / MDAHPSBA / DC 10 ASBA tetrapolymer fracturing thickener, that is, the polymer fracturing thickener of the present invention).

[0051] The above-mentioned initiator is a composite initiator, including an oxidation-reduction system initiator and a water-soluble azo initiator. In the above-mentioned oxidation-reduction system initiator, the oxidant is potassium persulfate, the reductant is sodium bisulfite, and the molar ratio of the oxidant to the reductant is 1:1.2; the above-mentioned water-soluble azo initiator is azobisisobutylimidazoline hydrochloride (VA-044); in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1.5.

[0052] The following is the experimental (test) part of the present invention:

[0053] Experiment 1: Partial hydrolysis of AM / AMES / MDAHPSBA / DC 12 Structural characterization of the ASBA tetrapolymer fracturing thickener (ie, the polymer fracturing thickener of the present invention).

[0054] The structure of the polymer prepared in Example 1 (i.e., the polymer fracturing thickener of the present invention) was analyzed as follows: The FTIR spectrum of the polymer is as follows: Figure 1 Shown: 3700~3331cm -1 -OH and -NH (antisymmetric) stretching vibration absorption peak; 3195cm -1 is the stretching vibration absorption peak of -NH (symmetric); 2931cm -1 and 2860cm -1 They are the asymmetric and symmetric stretching vibration absorption peaks of methylene respectively; 1657cm -1 It is -C=O stretching vibration absorption peak; 1450cm -1 It is the absorption peak of the in-plane bending vibration of methylene; 1415cm -1 is the absorption peak of amide CN stretching vibration; 1348cm -1 The CN stretching vibration absorption peaks of amine and quaternary ammonium salt are at 1318 cm -1 It is the CO stretching vibration absorption peak of carboxylic acid; 1184cm -1 and 1039cm -1 The infrared spectrum confirms that the product contains structures such as -CONH2, -SO3, -CH2-, -CH3, -COO-, tertiary amine, and quaternary ammonium salt. The infrared spectrum data proves that the target product is partially hydrolyzed AM / AMES / MDAHPSBA / DC 12 ASBA tetrapolymer.

[0055] Experiment 2: Partial hydrolysis of AM / AMES / MDAHPSBA / DC n Viscosity test experiment of ASBA tetrapolymer fracturing thickener (ie, polymer fracturing thickener of the present invention).

[0056] At room temperature (25±1°C), the apparent viscosities of the polymer solutions (prepared with distilled water) obtained in Example 1 and Example 2 of different concentrations were measured using an NDJ-5S digital rotational viscometer to investigate the changes in the apparent viscosities of the two solutions with concentration. Figure 2 .Depend on Figure 2 It can be seen that at 1000 mg / L, the apparent viscosities of the solutions of the two polymers in Example 1 and Example 2 can reach 62.2 mPa·s and 72.8 mPa·s, respectively; at 2000 mg / L, they can reach 246.3 mPa·s and 274.7 mPa·s, respectively; and at 4000 mg / L, they can reach 1247 mPa·s and 1544 mPa·s, respectively. The results show that the synthesized polymer (i.e., the polymer fracturing thickener of the present invention) exhibits good viscosity increasing ability.

[0057] Experiment 3: Partial hydrolysis of AM / AMES / MDAHPSBA / DCn Salt resistance test experiment of ASBA tetrapolymer fracturing thickener (ie, polymer fracturing thickener of the present invention).

[0058] The copolymers obtained in Example 1 and Example 2 were prepared into 2000 mg / L aqueous solutions using mixed brine of different concentrations (the ratio of various salts in the mixed brine was NaCl: KCl: CaCl2: MgCl2 = 7:2:0.6:0.4, mass ratio). The apparent viscosities of the two polymer solutions were measured at 25°C. Figure 3 .Depend on Figure 3 It can be seen that when the mineralization of the brine increases, the apparent viscosity of the two polymers increases first and then decreases. When the content of the brine increases to 50000 mg / L, the apparent viscosities of the two copolymer solutions are 101.5 mPa·s and 113.3 mPa·s respectively; the results show that the synthesized polymer (i.e., the polymer fracturing thickener of the present invention) exhibits good salt resistance.

[0059] Experiment 4: Partial hydrolysis of AM / AMES / MDAHPSBA / DC 10 Experimental test on the temperature resistance of ASBA tetrapolymer fracturing thickener (i.e., the polymer fracturing thickener of the present invention).

[0060] The polymer prepared in Example 2 (i.e., the polymer fracturing thickener of the present invention) was prepared into a 5000 mg / L aqueous solution using 30000 mg / L composite brine (the ratio of various salts in the composite brine was NaCl: KCl: CaCl2: MgCl2 = 7:2:0.6:0.4, mass ratio) and heated at 150°C for 170 s. -1 Shear polymer solutions under shear rate conditions, see Figure 4 .Depend on Figure 4 It can be seen that the apparent viscosity of the polymer decreases with the extension of the shear time. When the shear time is 120 min, the apparent viscosity of the polymer reaches 69.3 mPa·s. The results show that the synthesized polymer (i.e., the polymer fracturing thickener of the present invention) exhibits good temperature and shear resistance.

[0061] Experiment 5: Partial hydrolysis of AM / AMES / MDAHPSBA / DC n Experimental test on the temperature resistance of gel prepared by ASBA tetrapolymer fracturing thickener (i.e., polymer fracturing thickener of the present invention).

[0062] The mother solutions of Example 1 and Example 2 were prepared into appropriate concentrations, and then mixed with an organic zirconium crosslinking agent to form a gel (wherein the polymer concentration was 0.5% and the crosslinking agent concentration was 0.6%). The mother solutions were ... -1 The temperature resistance of the gels of Example 1 and Example 2 was evaluated at a shear rate of Figure 5 .Depend on Figure 5 It can be seen that the synthesized copolymer maintains a relatively high viscosity at high temperature after being cross-linked with organic zirconium. At 190°C, the apparent viscosities of the synthesized polymer (i.e., the polymer fracturing thickener of the present invention) are 368.7 mPa·s and 394.3 mPa·s, respectively, maintaining good temperature resistance and thickening effect under high temperature conditions of 190°C.

[0063] In summary, the betaine-type double-tailed hydrophobically associating polymer fracturing thickener prepared in the above embodiments of the present invention has good viscosity increasing property and exhibits good salt resistance in mixed brine with a salinity of ≥30000 mg / L; the prepared linear solution has good viscosity increasing property at 150°C and a shear rate of 170s -1 The viscosity retention capacity of the cross-linked gel was higher at 190℃ and shear rate of 170s. -1 The viscosity retention exceeds 300mPa·s. The present invention provides a water-soluble betaine type double-tailed hydrophobic associating polymer fracturing thickener, which has good performance and good viscosity increasing ability at low concentrations. The prepared polymer linear solution and the cross-linked gel have good viscosity retention ability and good shear resistance at high temperature, high mineralization and high shear rate. It can play a good role in seam-making ability and sand carrying ability during fracturing construction, and can meet the technical requirements of the widely used fracturing thickeners on the market, thereby ensuring the smooth construction of oil and gas production increase in high-temperature and high-mineralization oil and gas reservoirs, solving the problems of high residues that damage the formation produced by the existing plant gum fracturing fluid, and poor temperature and salt resistance of ordinary synthetic polymers in high-mineralization (mineralization ≥ 30000mg / L) brine.

Claims

1. A betaine type double-tailed hydrophobically associating polymer fracturing thickener, characterized in that It is composed of acrylamide AM, 2-allylmethylaminoethylsulfonate AMES-Na, methyldiallylhydroxypropylsulfonyl betaine MDAHPSBA and a hydrophobic monomer with a betaine structure and a double-tailed long-chain alkyl allyl sulfonyl betaine DC n The four monomers of ASBA are copolymerized to form a gel. After the reaction is completed, the gel is chopped and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, it is neutralized and purified to obtain the final product. The structural formula of the polymer fracturing thickener is as follows: In the above structural formula, x, y, z, p, q are the molar percentage ranges of the structural units: x = 67.5% to 83.9%, y = 10% to 20%, z = 5% to 10%, p = 1% to 2%, q = 0.1% to 0.5%, x + y + z + p + q = 100%. Where n = 8, 10, 12, 14.

2. The betaine type double-tailed hydrophobically associating polymer fracturing thickener according to claim 1, characterized in that The molar proportions of each monomer added are as follows: 87.5-93.9 parts of acrylamide AM, 5-10 parts of 2-allylmethylaminoethylsulfonate AMES-Na, 1-2 parts of methyldiallylhydroxypropylsulfobetaine MDAHPSBA, and 1-2 parts of double-tailed long-chain alkyl allylsulfoethylbetaine DC, a hydrophobic monomer having a betaine structure. n ASBA 0.1~0.5 parts.

3. The betaine type double-tailed hydrophobically associating polymer fracturing thickener according to claim 1 or 2, characterized in that The preparation method of 2-allylmethylaminoethanesulfonic acid sodium AMES-Na comprises the following process steps: adding an appropriate amount of anhydrous ethanol as a solvent to a three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 65-95 g of sodium 2-chloroethylsulfonate at room temperature, then slowly adding 30-43 g of N-methylallylamine under stirring, adding 0.15-0.21 g of methylhydroquinone as an inhibitor, and charging 32-47 g of an acid binding agent wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 20-25 hours, and removing the solvent and excess N-methylallylamine by reduced pressure distillation using a rotary evaporator to obtain 2-allylmethylaminoethanesulfonic acid sodium AMES-Na.

4. The betaine type double-tailed hydrophobically associating polymer fracturing thickener according to claim 1 or 2, characterized in that The preparation method of the salt-resistant monomer methyl diallyl hydroxypropyl sulfobetaine MDAHPSBA comprises the following process steps: adding an appropriate amount of anhydrous ethanol as a solvent to a three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, adding 75 to 110 g of sodium 3-chloro-2-hydroxypropane sulfonate at room temperature and with magnetic stirring turned on, then slowly adding 45 to 65 g of N-methyl diallylamine under stirring, adding 0.17 to 0.25 g of inhibitor methyl hydroquinone, raising the temperature to reflux, reacting at a constant temperature for 10 to 12 hours, using a rotary evaporator to remove the solvent and excess N-methyl diallylamine by reduced pressure distillation, and then using acetone for separation and purification to obtain methyl diallyl hydroxypropyl sulfobetaine MDAHPSBA.

5. The betaine type double-tailed hydrophobically associating polymer fracturing thickener according to claim 1 or 2, characterized in that The above hydrophobic monomer with betaine structure double-tail long-chain alkyl allyl sulfoethyl betaine DC n The preparation method of ASBA comprises the following process steps: (1) adding an appropriate amount of hexafluoroisopropanol as a solvent to a three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 35-50 g of a long-chain alkylamine at room temperature with magnetic stirring on, then slowly adding 30-40 g of sodium 2-chloroethylsulfonate under stirring, placing 13-20 g of an acid binding agent wrapped with filter paper in the Soxhlet extractor, raising the temperature to reflux, reacting at constant temperature for 30-35 hours, removing the solvent by reduced pressure distillation using a rotary evaporator, separating the long-chain alkylamine with distilled water, and recrystallizing the filtrate to obtain a long-chain alkyl sulfonethylamine; (2) adding an appropriate amount of anhydrous ethanol as a solvent to a three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 40-60 g of a chlorinated long-chain alkane at room temperature with magnetic stirring on, then slowly adding 60-90 g of (3) in a three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, add an appropriate amount of anhydrous ethanol as a solvent, add 12 to 20 g of allyl chloride at a temperature of 5 to 8 ° C and turn on magnetic stirring, then slowly add 70 to 100 g of the di-tailed long-chain alkyl sulfoethyl tertiary amine under stirring, add 0.12 to 0.20 g of methyl hydroquinone as an inhibitor, raise the temperature to reflux, react at a constant temperature for 10 to 12 hours, remove the solvent and excess allyl chloride by vacuum distillation on a rotary evaporator, and recrystallize with acetone to obtain a hydrophobic monomer di-tailed long-chain alkyl allyl sulfoethyl betaine DC having a betaine structure. n ASBA.

6. The betaine type double-tailed hydrophobically associating polymer fracturing thickener according to claim 1, characterized in that The preparation method comprises the following process steps: firstly, adding 1000-1500 mole parts of distilled water into a reactor, and then sequentially adding 87.5-93.9 mole parts of acrylamide AM, 5-10 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-2 mole parts of methyldiallylhydroxypropylsulfobetaine MDAHPSBA, an emulsifier, a hydrophobic monomer with a betaine structure and a double-tailed long-chain alkyl allyl sulfoethyl betaine DC under stirring; n ASBA 0.1-0.5 molar parts, and then distilled water is added to control the total mass percentage concentration of the reaction monomers between 15% and 30%, and after stirring evenly, N2 is passed for 30-35 minutes; then an initiator is added, and N2 is continued to be passed, and the reaction is carried out for 4-10 hours under nitrogen protection and 30-60°C; after the reaction, the obtained gel-like product, i.e., the copolymer, is chopped up, sodium carbonate solution is added, and then distilled water is added to dilute the copolymer to a mass percentage concentration of 5%-8%, and the reaction is hydrolyzed at a temperature of 85-90°C for 1.5-2.5 hours. After the reaction, dilute hydrochloric acid is used for neutralization, and the product is washed with anhydrous ethanol, and then the product is crushed, dried, and sieved to obtain a betaine type double-tailed hydrophobic associating polymer fracturing thickener.

7. The betaine type double-tailed hydrophobically associating polymer fracturing thickener according to claim 6, characterized in that The emulsifier is hexadecyltrimethylammonium bromide, and the amount of hexadecyltrimethylammonium bromide added is 0.06% to 0.1% of the total mass of the reaction solution; the initiator is added in an amount of 0.05% to 0.2% of the total mass of the reaction monomers, and the total mass of the reaction monomers is the total mass of the four monomers described above; the sodium carbonate solution is added in an amount of 45% to 75% of the weight of the acrylamide monomer, and the sodium carbonate solution is a sodium carbonate aqueous solution with a mass percentage concentration of 15% to 20%; the mass fraction of the dilute hydrochloric acid is 5%; The above-mentioned initiator is a composite initiator, including an oxidation-reduction system initiator and a water-soluble azo initiator. In the oxidation-reduction system initiator, the oxidant is potassium persulfate or ammonium persulfate, the reductant is sodium bisulfite, and the molar ratio of the oxidant to the reductant is 1:1 to 1.5; the water-soluble azo initiator is one or a combination of azobisisobutylamidine hydrochloride V-50, azobisisobutylimidazoline hydrochloride VA-044, and azobis(N-2-carboxyethyl-2-methylpropionamidine) hydrate VA-057, and the ratio is arbitrary when combined; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1 to 2.

8. The betaine type double-tailed hydrophobically associating polymer fracturing thickener according to claim 5, characterized in that The above hydrophobic monomer with betaine structure double-tail long-chain alkyl allyl sulfoethyl betaine DC n In ASBA, the long-chain alkyl is dodecyl; the long-chain alkylamine in step (1) is dodecylamine, the chlorinated long-chain alkane in step (2) is chlorododecane; the final product in step (3) is a hydrophobic monomer having a betaine structure, didodecyl allyl sulfoethyl betaine DC 12 ASBA; or The above hydrophobic monomer with betaine structure double-tail long-chain alkyl allyl sulfoethyl betaine DC n In ASBA, the long-chain alkyl is selected from decyl; the long-chain alkylamine in step (1) is decylamine, the chlorinated long-chain alkane in step (2) is chlorodecane; the final product in step (3) is a hydrophobic monomer having a betaine structure, didecyl allyl sulfoethyl betaine DC 10 ASBA.

9. The betaine type double-tailed hydrophobically associating polymer fracturing thickener according to claim 3 or 5, characterized in that The above acid binding agent is potassium carbonate or sodium carbonate.

10. A method for preparing the betaine type double-tailed hydrophobically associating polymer fracturing thickener according to claim 1, characterized in that The method comprises the following process steps: firstly, adding 1000-1500 mole parts of distilled water into a reactor, and then sequentially adding 87.5-93.9 mole parts of acrylamide AM, 5-10 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-2 mole parts of methyldiallylhydroxypropylsulfonyl betaine MDAHPSBA, an emulsifier, a hydrophobic monomer with a betaine structure and a double-tailed long-chain alkyl allyl sulfonyl betaine DC under stirring; n ASBA 0.1-0.5 molar parts, and then distilled water is added to control the total mass percentage concentration of the reaction monomers between 15% and 30%, and the mixture is stirred evenly and N2 is passed through for 30-35 minutes; then an initiator is added, and N2 is continued to be passed through, and the mixture is reacted for 4-10 hours under nitrogen protection and 30-60°C; after the reaction, the obtained gel-like product, i.e., the copolymer, is chopped up, and a sodium carbonate solution is added, and then distilled water is added to dilute the copolymer to a mass percentage concentration of 5%-8%, and the copolymer is hydrolyzed at a temperature of 85-90°C for 1.5-2.5 hours. After the reaction, the mixture is neutralized with dilute hydrochloric acid, and the product is washed with anhydrous ethanol, and then the product is crushed, dried, and sieved to obtain a betaine-type double-tailed hydrophobically associating polymer fracturing thickener.

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