Cyclic structure betaine and double-tailed hydrophobic association polymer fracturing thickening agent and preparation method thereof

Abstract

The invention relates to a ring structure betaine and double-tailed hydrophobic association polymer fracturing thickening agent and a preparation method thereof. The thickening agent is formed by copolymerization of four monomers, namely acrylamide, 2-allyl methylamino sodium ethanesulfonate, methyl diallyl sulfoethyl betaine and hydrophobic monomer double-tailed long-chain alkyl methyl allyl ammonium chloride. The preparation method comprises the following steps: firstly adding distilled water, then sequentially adding acrylamide, 2-allyl methylamino sodium ethanesulfonate, methyl diallyl sulfoethyl betaine and a hydrophobic monomer double-tailed long-chain alkyl methyl allyl ammonium chloride, adjusting the total concentration, introducing N2 to remove oxygen, adding an initiator, and reacting to prepare an AM / AMES / MDASBA / DCnMAAC quadripolymer, namely the polymer fracturing thickening agent. The thickening agent provided by the invention has good water solubility, and shows good salt resistance in mixed brine with the mineralization degree of greater than or equal to 30000 mg / L. The prepared linear solution and gel 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 having a cyclic structure betaine base and a double-tail hydrophobic type, specifically a cyclic structure betaine and a double-tail hydrophobic associating polymer fracturing thickener. The present invention also relates to a preparation method of the cyclic structure betaine and the double-tail hydrophobic associating polymer fracturing thickener. Background Art

[0002] In recent years, oil extraction has developed rapidly, and there are more and more "low pressure, low yield, 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 yield is very low or even no yield. They need to be transformed by fracturing to have a certain production value. On the other hand, there are harsh conditions such as high temperature, high salt and high mineralization during the development process. Commonly used plant gum fracturing fluids have high insoluble content, incomplete gel breaking, and a large amount of residue, which can easily cause damage to the formation. Compared with conventional fracturing fluids, viscoelastic surfactant (VES) fracturing fluids have the characteristics of low residue content and less reservoir damage, but their temperature resistance is poor and the production cost is too high, and the market benefits are low, which restricts the widespread use of this type of thickener. The preparation method of polyacrylamide thickening thickener is simple and low cost. It is widely used in the field of oil and gas extraction. This type of polymer fracturing fluid usually uses anionic polyacrylamide as a thickener. Anionic polyacrylamide has a certain viscosity-increasing effect, but poor salt resistance. Although cationic polyacrylamide has greatly improved the salt resistance of polyacrylamide, it still has problems such as water solubility and low viscosity. Hydrophobic associating water-soluble polymers are water-soluble polymers formed by introducing a very small amount of hydrophobic groups into the hydrophilic main chain of the polymer. They show good viscosity enhancement, temperature resistance, salt resistance and shear resistance, making them a water-soluble polymer material with good application prospects (Chen Hong, Li Erxiao, Ye Zhongbin, et al. Interaction between hydrophobic associating polyacrylamide and gemini surfactants [J]. Acta Physico-Chimica Sinica, 2011, 27 (3): 671-676.). This type of polymer has attracted widespread attention due to its good viscosity enhancement, temperature resistance, salt resistance and shear resistance. The currently used hydrophobic associating polymers are copolymerized by acrylamide monomers, acrylic acid monomers and hydrophobic monomers. When the mineralization exceeds 20000 mg / L, their salt resistance is poor. Therefore, it is necessary to develop thickening thickeners for fracturing fluids with better viscosity enhancement, temperature resistance, salt resistance and shear resistance.

[0003] 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 has 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.

[0004] 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

[0005] The purpose of the present invention is to provide a fracturing thickener of cyclic betaine and double-tail hydrophobic associating polymer, which has good performance and good viscosity increasing ability at low concentration. The prepared polymer linear solution and 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 thickener on the market, so as to ensure 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.

[0006] To this end, another object of the present invention is to provide a method for preparing a cyclic structure betaine and a double-tailed hydrophobic associating polymer fracturing thickener.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A ring-structured betaine and a double-tailed hydrophobic associating polymer fracturing thickener (or a water-soluble ring-structured betaine and a double-tailed hydrophobic associating polymer fracturing thickener), the technical scheme of which is that it is composed of acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, methyl diallyl sulfoethyl betaine MDASBA and a hydrophobic monomer double-tailed long-chain alkyl methyl allyl ammonium chloride DC n MAAC is copolymerized from four monomers, and the structural formula of the polymer fracturing thickener is as follows:

[0009]

[0010] In the above structural formula, x, y, z, and p are the molar percentage ranges of the structural units: x = 67.5% to 83.9%, y = 15% to 30%, z = 1% to 2%, p = 0.1% to 0.5%, x + y + z + p = 100%. Among them, n = 8, 10, 12, and the long-chain alkyl group is an alkane with the same carbon number.

[0011] The molar fractions of the monomers used to prepare the polymer fracturing thickener are as follows (i.e., the fracturing thickener is made from the following molar fractions of monomers): 67.5-83.9 parts of acrylamide AM, 15-30 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-2 parts of methyldiallylsulfoethyl betaine MDASBA, and 1-2 parts of hydrophobic monomer double-tail long-chain alkyl methylallyl ammonium chloride DC n MAAC 0.1~0.5 parts.

[0012] 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.

[0013] The preparation method of the salt-resistant monomer methyl diallyl sulfoethyl betaine MDASBA 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 70 to 100 g of sodium 2-chloroethyl sulfonate at room temperature (temperature is 23 to 25° C.) and turning on magnetic stirring, then slowly adding 50 to 70 g of N-methyl diallyl amine 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 diallyl amine by reduced pressure distillation, and then using acetone to separate and purify to obtain methyl diallyl sulfoethyl betaine MDASBA.

[0014] The above hydrophobic monomer double tail long chain alkyl methyl allyl ammonium chloride DC n The preparation method of MAAC comprises the following process steps: adding an appropriate amount of anhydrous ethanol as a solvent to a three-necked flask (500 mL) equipped with a thermometer, a reflux condenser and a magnetic rotor, slowly adding 20 to 30 g of allyl chloride at a temperature of 5 to 8° C. and with magnetic stirring turned on, then slowly adding 80 to 120 g of a double-tailed long-chain alkyl methyl tertiary amine, adding 0.15 to 0.25 g of a polymerization inhibitor methyl hydroquinone, raising the temperature to reflux, reacting at a constant temperature for 10 to 15 hours, removing the solvent and excess allyl chloride by reduced pressure distillation using a rotary evaporator, and then separating and purifying with acetone to obtain a hydrophobic monomer double-tailed long-chain alkyl methyl allyl ammonium chloride DC n MAAC.

[0015] The preparation method of the cyclic structure betaine and double-tail hydrophobic associating polymer fracturing thickener comprises the following process steps: firstly, 1000-1500 mole parts of distilled water are added into a reactor, and 67.5-83.9 mole parts of acrylamide AM, 15-30 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-2 mole parts of methyldiallylsulfoethyl betaine MDASBA, an emulsifier, a hydrophobic monomer double-tail long-chain alkyl methylallyl ammonium chloride DC are added in sequence under stirring. n MAAC 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 at 30-60°C; after the reaction, the obtained gel product is washed with anhydrous ethanol, and the product is crushed, dried, and sieved to obtain AM / AMES / MDASBA / DCn MAAC tetrapolymer is a fracturing thickener composed of cyclic structure betaine and double-tailed hydrophobic associating polymer.

[0016] In the above technical scheme, the preferred technical scheme may be that the acid binding agent may be potassium carbonate or sodium carbonate. The emulsifier may be hexadecyltrimethylammonium bromide, and the amount of hexadecyltrimethylammonium 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 described above. The 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 a combination of azobisisobutylamidine hydrochloride V-50, azobisisobutylimidazoline hydrochloride VA-044, and azobis(N-2-carboxyethyl-2-methylpropionamidine) hydrate VA-057, and the ratio of the combination is arbitrary; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1-2.

[0017] In the above technical solution, the preferred technical solution can also be that the hydrophobic monomer double-tail long-chain alkyl methyl allyl ammonium chloride DC n In MAAC, the long-chain alkyl group can be selected from decyl groups. The double-tailed long-chain alkyl methyl tertiary amine described in the preparation is didecyl methyl tertiary amine, and the final product is a hydrophobic monomer didecyl methyl allyl ammonium chloride DC 10 MAAC. See Example 1.

[0018] In the above technical solution, the preferred technical solution can also be that the hydrophobic monomer double-tail long-chain alkyl methyl allyl ammonium chloride DC n In MAAC, the long-chain alkyl group can be selected from dodecyl. The double-tailed long-chain alkyl methyl tertiary amine described in the preparation is didodecyl methyl tertiary amine, and the final product is a hydrophobic monomer didodecyl methyl allyl ammonium chloride DC 12 MAAC. See Example 2.

[0019] Among the above technical solutions, a preferred technical solution may also be Embodiment 1 of the present invention.

[0020] The cyclic structure betaine and double-tail hydrophobic associating polymer fracturing thickener of the present invention are composed of acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, methyl diallyl sulfoethyl betaine MDASBA and hydrophobic monomer double-tail long-chain alkyl methyl allyl ammonium chloride DC nMAAC is copolymerized by four monomers. Preparation method: first add an appropriate amount of distilled water to the reactor, then add acrylamide, 2-allylmethylaminoethylsulfonic acid sodium, methyldiallylsulfoethyl betaine, hexadecyltrimethylammonium bromide, hydrophobic monomer double-tail long-chain alkyl methylallyl ammonium chloride, add distilled water, stir evenly, pass N2 to deoxygenate, add initiator, react at a certain temperature to obtain AM / AMES / MDASBA / DC n The MAAC tetrapolymer is the polymer fracturing thickener. The present invention introduces a double-tailed hydrophobic chain into the polymer chain, which improves the viscosity increasing ability and temperature resistance of the polymer, and increases the rigidity of the molecular chain by introducing a ring structure, thereby improving the thermal stability and shear resistance of the polymer. Sulfonic acid groups are introduced into the molecular chain to improve the water solubility and salt resistance of the polymer, meeting the actual construction needs of increasing oil and gas production 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 shows good salt resistance in mixed brine with a mineralization of ≥30,000 mg / L; the prepared linear solution has good water solubility at 150°C and a shear rate of 170s -1 Under the condition of shearing for 120 minutes, it has a high viscosity retention capacity; the gel formed after cross-linking has a high viscosity retention capacity at 190℃ and a shear rate of 170s -1 The viscosity remains over 250 mPa·s.

[0021] Compared with the prior art, the present invention has the following effects: (1) the introduction of a double-tail long chain on the hydrophobic monomer enhances the hydrophobic association between copolymer molecules, thereby increasing the viscosity of the polymer; (2) the introduction of a diallyl group and a sulfonic acid group to form a ring structure after reaction increases the rigidity of the polymer molecular chain, greatly improves the polymer's temperature resistance and salt resistance, and enhances the polymer's shear resistance; (3) the fracturing thickener exhibits good temperature resistance, salt resistance and shear resistance, and better meets the requirements for increasing oil and gas production in high-temperature and high-mineralization oil fields on site.

[0022] Referring to the experimental (test) part of the present invention below, in summary, the present invention provides a (water-soluble) cyclic structure betaine and 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, 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

[0023] Figure 1 This is the infrared spectrum of the copolymer (fracturing thickener) synthesized (prepared) in Example 1 of the present invention.

[0024] 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.

[0025] 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.

[0026] Figure 4 This is a graph showing the relationship between the apparent viscosity of the copolymer (fracturing thickener) synthesized in Example 1 of the present invention and the shear time.

[0027] 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

[0028] 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.

[0029] Example 1: The (aqueous) cyclic betaine and double-tail hydrophobic associating polymer fracturing thickener of the present invention is prepared from the following monomers in molar fractions (copolymerized from four monomers): 78.48 parts of acrylamide AM, 19.73 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1.47 parts of methyldiallylsulfoethyl betaine MDASBA, and 1.47 parts of hydrophobic monomer double-tail long-chain alkyl methylallyl ammonium chloride DC n MAAC 0.32 parts. The structural formula of the polymer fracturing thickener is as follows:

[0030]

[0031] In the above structural formula, x, y, z, and p are the molar percentage ranges of the structural units: x = 78.48%, y = 19.73%, z = 1.47%, p = 0.32%, and x + y + z + p = 100%. Where n = 8, 10, 12, and in this embodiment n = 8. The above hydrophobic monomer double-tail long-chain alkyl methyl allyl ammonium chloride DC nIn MAAC, the long-chain alkyl group can be selected from decyl groups. The double-tailed long-chain alkyl methyl tertiary amine described in the preparation is didecyl methyl tertiary amine, and the final product is a hydrophobic monomer didecyl methyl allyl ammonium chloride DC 10 MAAC.

[0032] 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 75 g of sodium 2-chloroethylsulfonate at a temperature of 25° C., then slowly adding 34 g of N-methylallylamine under stirring, adding 0.16 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 22 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.

[0033] The preparation method of the salt-resistant monomer methyl diallyl sulfoethyl betaine MDASBA 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 85 g of sodium 2-chloroethyl sulfonate at a temperature of 25° C. and with magnetic stirring turned on, then slowly adding 60 g of N-methyl diallyl amine under stirring, adding 0.22 g of a polymerization inhibitor methyl hydroquinone, raising the temperature to reflux, reacting at a constant temperature for 12 hours, removing the solvent and excess N-methyl diallyl amine by reduced pressure distillation using a rotary evaporator, and then separating and purifying with acetone to obtain methyl diallyl sulfoethyl betaine MDASBA.

[0034] The hydrophobic monomer didecyl methyl allyl ammonium chloride DC 10 The preparation method of MAAC 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, slowly adding 26 g of allyl chloride at a temperature of 5° C. and with magnetic stirring turned on, then slowly adding 95 g of didecyl methyl tertiary amine, adding 0.17 g of methyl hydroquinone as an inhibitor, raising the temperature to reflux, reacting at a constant temperature for 14 hours, removing the solvent and excess allyl chloride by reduced pressure distillation using a rotary evaporator, and then separating and purifying with acetone to obtain a hydrophobic monomer didecyl methyl allyl ammonium chloride DC 10 MAAC.

[0035] The preparation method of the cyclic structure betaine and double-tail hydrophobic associating polymer fracturing thickener comprises the following process steps: firstly, 1000 mole parts of distilled water are added into a reactor, and 78.48 mole parts of acrylamide AM, 19.73 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1.47 mole parts of methyldiallylsulfoethyl betaine MDASBA, emulsifier hexadecyltrimethylammonium bromide (the amount of hexadecyltrimethylammonium bromide added is 0.09% of the total mass of the reaction solution), hydrophobic monomer didecylmethylallyl ammonium chloride DC are added in sequence under stirring. 10 0.32 molar parts of MAAC, and then distilled water was added to control the total mass percentage concentration of the reaction monomers to 20%. After stirring evenly, N2 was passed (deoxygenation) for 30 minutes; then 0.08% of the initiator of the total mass of the reaction monomers was added (the total mass of the reaction monomers was the total mass of the four monomers mentioned above); N2 was continued to be passed, and the reaction was carried out under nitrogen protection at 50°C for 7 hours; after the reaction, the obtained gel product was washed with anhydrous ethanol, and the product was crushed, dried, and sieved to obtain AM / AMES / MDASBA / DC 10 The MAAC tetrapolymer is a cyclic structure betaine and a double-tailed hydrophobic associating polymer fracturing thickener (ie, the polymer fracturing thickener of the present invention).

[0036] 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 ammonium persulfate, the reductant is sodium bisulfite, and the molar ratio of the oxidant to the reductant is 1:1.1; the above-mentioned water-soluble azo initiator is azobisisobutylamidine hydrochloride (V-50); in the above-mentioned composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1.5.

[0037] For the convenience of presentation in the experimental part of the present invention, the above AM / AMES / MDASBA / DC 10 The MAAC tetrapolymer is abbreviated as PAAMD (ie, the polymer fracturing thickener of the present invention).

[0038] Example 2: The cyclic structure betaine and double-tail hydrophobic associating polymer fracturing thickener of the present invention is made of the following monomers in molar fractions (copolymerized from four monomers): 76.15 parts of acrylamide AM, 22.08 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1.55 parts of methyldiallylsulfoethyl betaine MDASBA, and hydrophobic monomer double-tail long-chain alkyl methylallyl ammonium chloride DC n MAAC 0.22 parts. The structural formula of the polymer fracturing thickener is the same as that of Example 1.

[0039] In the above structural formula, x, y, z, and p are the molar percentage ranges of the structural units: x = 76.15%, y = 22.08%, z = 1.55%, p = 0.22%, and x + y + z + p = 100%. Where n = 8, 10, 12, and in this embodiment n = 10. The above hydrophobic monomer double-tail long-chain alkyl methyl allyl ammonium chloride DC n In MAAC, the long-chain alkyl group can be selected from dodecyl, and the double-tailed long-chain alkyl methyl tertiary amine described in the preparation is didodecyl methyl tertiary amine, and the final product is a hydrophobic monomer didodecyl methyl allyl ammonium chloride DC 12 MAAC.

[0040] 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 89 g of sodium 2-chloroethylsulfonate at a temperature of 25° C., then slowly adding 40 g of N-methylallylamine under stirring, adding 0.19 g of methylhydroquinone as an inhibitor, and charging 44 g of potassium carbonate wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 24 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.

[0041] The preparation method of the salt-resistant monomer methyl diallyl sulfoethyl betaine MDASBA 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 80 g of sodium 2-chloroethyl sulfonate at a temperature of 25° C. and with magnetic stirring turned on, then slowly adding 58 g of N-methyl diallyl amine under stirring, adding 0.17 g of a polymerization inhibitor methyl hydroquinone, raising the temperature to reflux, reacting at a constant temperature for 11 hours, removing the solvent and excess N-methyl diallyl amine by reduced pressure distillation using a rotary evaporator, and then separating and purifying with acetone to obtain methyl diallyl sulfoethyl betaine MDASBA.

[0042] The hydrophobic monomer didodecyl methyl allyl ammonium chloride DC 12The preparation method of MAAC 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, slowly adding 24 g of allyl chloride at a temperature of 5° C. and with magnetic stirring turned on, then slowly adding 100 g of didodecyl methyl tertiary amine, adding 0.17 g of methyl hydroquinone as an inhibitor, raising the temperature to reflux, reacting at a constant temperature for 14 hours, removing the solvent and excess allyl chloride by reduced pressure distillation using a rotary evaporator, and then separating and purifying with acetone to obtain a hydrophobic monomer didodecyl methyl allyl ammonium chloride DC 12 MAAC.

[0043] The preparation method of the cyclic structure betaine and double-tail hydrophobic associating polymer fracturing thickener comprises the following process steps: firstly, 1200 mole parts of distilled water are added into a reactor, and 76.15 mole parts of acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na2 2.08 parts, methyldiallylsulfoethyl betaine MDASBA 1.55 mole parts, emulsifier hexadecyltrimethylammonium bromide (the amount of hexadecyltrimethylammonium bromide added is 0.1% of the total mass of the reaction solution), hydrophobic monomer didodecylmethylallyl ammonium chloride DC are added in sequence under stirring. 12 MAAC 0.22 mole parts, and then distilled water was added to control the total mass percentage concentration of the reaction monomers to 25%. After stirring evenly, N2 was passed (deoxygenation) for 30 minutes; then 0.1% of the initiator of the total mass of the reaction monomers was added (the total mass of the reaction monomers was the total mass of the four monomers mentioned above); N2 was continued to be passed, and the reaction was carried out under nitrogen protection at 45°C for 8 hours; after the reaction was completed, the obtained gel product was washed with anhydrous ethanol, and the product was crushed, dried, and sieved to obtain AM / AMES / MDASBA / DC 12 The MAAC tetrapolymer is a cyclic structure betaine and a double-tailed hydrophobic associating polymer fracturing thickener (ie, the polymer fracturing thickener of the present invention).

[0044] 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 1:1.1; the above-mentioned water-soluble azo initiator is a combination of azobisisobutylimidazoline hydrochloride (VA-044) and azobisisobutylamidine hydrochloride (V-50), and the mass ratio of VA-044 to V-50 is 2:1; in the above-mentioned composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1.6.

[0045] The following is the experimental (test) part of the present invention:

[0046] Experiment 1: AM / AMES / MDASBA / DC 10 Structural characterization of the MAAC tetrapolymer fracturing thickener (ie, the polymer fracturing thickener of the present invention).

[0047] AM / AMES / MDASBA / DC prepared in Example 1 10 The structure of the MAAC tetrapolymer (i.e., the polymer fracturing thickener of the present invention) is analyzed as follows: The FTIR spectrum of the polymer is as follows: Figure 1 Shown: 3332cm -1 -NH (antisymmetric) stretching vibration absorption peak; 3189cm -1 is the stretching vibration absorption peak of -NH (symmetrical); 2930cm -1 and 2853cm -1 They are the asymmetric and symmetric stretching vibration absorption peaks of methylene respectively; 1659cm -1 It is -C=O stretching vibration absorption peak; 1451cm -1 It is the absorption peak of the in-plane bending vibration of methylene; 1414cm -1 is the absorption peak of amide CN stretching vibration; 1341cm -1 The CN stretching vibration absorption peaks of amine and quaternary ammonium salt are at 1183cm -1 and 1038cm -1 The infrared spectrum confirms that the product contains structures such as -CONH2, -SO3, -CH2-, -CH3, tertiary amine, and quaternary ammonium salt. The infrared spectrum data proves that the target product is AM / AMES / MDASBA / DC 12 MAAC tetrapolymer.

[0048] Experiment 2: AM / AMES / MDASBA / DC n Viscosity testing experiment of MAAC tetrapolymer fracturing thickener (i.e., polymer fracturing thickener of the present invention).

[0049] At room temperature (25±1°C), the apparent viscosity of the polymer solutions (prepared with distilled water) prepared in Example 1 and Example 2 with different concentrations was measured using an NDJ-5S digital rotational viscometer to investigate the changes in the apparent viscosity of the two solutions with the polymer concentration. Figure 2 .Depend on Figure 2It 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 56.8 mPa·s and 48.5 mPa·s, respectively; at 2000 mg / L, they can reach 265.2 mPa·s and 235.4 mPa·s, respectively; and at 4000 mg / L, they can reach 1416 mPa·s and 1195 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.

[0050] Experiment 3: AM / AMES / MDASBA / DC n Experimental test on salt resistance of MAAC tetrapolymer fracturing thickener (i.e., polymer fracturing thickener of the present invention).

[0051] The copolymers prepared in Example 1 and Example 2 (i.e., the polymer fracturing thickener of the present invention) 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 107.7 mPa·s and 97.9 mPa·s, respectively; the results show that the synthesized polymer (i.e., the polymer fracturing thickener of the present invention) exhibits good salt resistance.

[0052] Experiment 4: AM / AMES / MDASBA / DC 10 Experimental test on the temperature resistance of the MAAC tetrapolymer fracturing thickener (i.e., the polymer fracturing thickener of the present invention).

[0053] The polymer prepared in Example 1 (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 brine was NaCl: KCl: CaCl2: MgCl2 = 7:2:0.6:0.4, mass ratio) and heated at 150°C for 170 s. -1 High temperature shear polymer solution 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 66.5 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.

[0054] Experiment 5: AM / AMES / MDASBA / DC n Experimental test on the temperature resistance of gel prepared by MAAC tetrapolymer fracturing thickener (i.e., polymer fracturing thickener of the present invention).

[0055] 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 high viscosity at high temperature after cross-linking with organic zirconium. The apparent viscosities at 190°C are 349.2 mPa·s and 287.4 mPa·s, respectively. It maintains good temperature resistance and thickening effect under high temperature conditions of 190°C.

[0056] In summary, the cyclic betaine and double-tailed hydrophobic associating polymer fracturing thickener prepared in the above embodiments of the present invention have good viscosity increasing properties, show good salt resistance in brine with a mineralization of ≥30000 mg / L, maintain a high viscosity under high temperature shear, and have good salt resistance, temperature resistance and shear resistance. The invention provides a water-soluble cyclic structure betaine and double-tail hydrophobic associating polymer fracturing thickener, which has good performance and good viscosity increasing ability at low concentration. The prepared polymer linear solution and cross-linked gel have good viscosity retention ability and good shear resistance under high temperature, high mineralization and high shear rate, play a good fracture-making ability and sand-carrying ability in the fracturing construction process, and 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 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-mineralization (mineralization ≥30000 mg / L) brine.

Claims

1. A ring structure betaine and double-tailed hydrophobic associating polymer fracturing thickener, characterized in that It is composed of acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, methyldiallylsulfoethyl betaine MDASBA and hydrophobic monomer double-tail long-chain alkyl methylallyl ammonium chloride DC n MAAC is copolymerized from four monomers, and the structural formula of the polymer fracturing thickener is as follows: In the above structural formula, x, y, z, and p are the molar percentage ranges of the structural units: x=67.5% to 83.9%, y=15% to 30%, z=1% to 2%, p=0.1% to 0.5%, x+y+z+p=100%, and n=8, 10, or 12.

2. The cyclic structure betaine and double-tailed hydrophobically associating polymer fracturing thickener according to claim 1, characterized in that The molar fractions of the monomers used to prepare the polymer fracturing thickener are as follows: 67.5-83.9 parts of acrylamide AM, 15-30 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-2 parts of methyldiallylsulfoethyl betaine MDASBA, and 1-2 parts of hydrophobic monomer double-tail long-chain alkyl methylallyl ammonium chloride DC. n MAAC 0.1~0.5 parts.

3. The cyclic structure betaine and 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 cyclic structure betaine and 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 sulfoethyl betaine MDASBA 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 70-100 g of sodium 2-chloroethyl sulfonate at room temperature and with magnetic stirring turned on, then slowly adding 50-70 g of N-methyl diallyl amine under stirring, adding 0.17-0.25 g of inhibitor methyl hydroquinone, raising the temperature to reflux, reacting at a constant temperature for 10-12 hours, using a rotary evaporator to remove the solvent and excess N-methyl diallyl amine by reduced pressure distillation, and then using acetone to separate and purify to obtain methyl diallyl sulfoethyl betaine MDASBA.

5. The cyclic structure betaine and double-tailed hydrophobically associating polymer fracturing thickener according to claim 1 or 2, characterized in that The above hydrophobic monomer double tail long chain alkyl methyl allyl ammonium chloride DC n The preparation method of MAAC 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, slowly adding 20 to 30 g of allyl chloride at a temperature of 5 to 8° C. and with magnetic stirring turned on, then slowly adding 80 to 120 g of a double-tailed long-chain alkyl methyl tertiary amine, adding 0.15 to 0.25 g of a polymerization inhibitor methyl hydroquinone, raising the temperature to reflux, reacting at a constant temperature for 10 to 15 hours, removing the solvent and excess allyl chloride by reduced pressure distillation using a rotary evaporator, and then separating and purifying with acetone to obtain a hydrophobic monomer double-tailed long-chain alkyl methyl allyl ammonium chloride DC n MAAC.

6. The cyclic structure betaine and double-tailed hydrophobically associating polymer fracturing thickener according to claim 1, characterized in that The preparation method comprises the following process steps: firstly, 1000-1500 mole parts of distilled water are added into a reactor, and then 67.5-83.9 mole parts of acrylamide AM, 15-30 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-2 mole parts of methyldiallylsulfoethyl betaine MDASBA, an emulsifier, a hydrophobic monomer double-tail long-chain alkyl methylallyl ammonium chloride DC are added in sequence under stirring. n MAAC 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 the initiator is added, and N2 is continued to be passed, and the reaction is carried out under nitrogen protection at 30-60°C for 4-10 hours; after the reaction is completed, the obtained gel product is washed with anhydrous ethanol, and the product is crushed, dried, and sieved to obtain AM / AMES / MDASBA / DC n MAAC tetrapolymer is a fracturing thickener composed of cyclic structure betaine and double-tailed hydrophobic associating polymer.

7. The cyclic structure betaine and 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 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 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 to 2.

8. The cyclic structure betaine and double-tailed hydrophobically associating polymer fracturing thickener according to claim 5, characterized in that The above hydrophobic monomer double tail long chain alkyl methyl allyl ammonium chloride DC n In MAAC, the long-chain alkyl group can be selected from decyl groups. The double-tailed long-chain alkyl methyl tertiary amine described in the preparation is didecyl methyl tertiary amine, and the final product is a hydrophobic monomer didecyl methyl allyl ammonium chloride DC 10 MAAC; or The above hydrophobic monomer double tail long chain alkyl methyl allyl ammonium chloride DC n In MAAC, the long-chain alkyl group can be selected from dodecyl, and the double-tailed long-chain alkyl methyl tertiary amine described in the preparation is didodecyl methyl tertiary amine, and the final product is a hydrophobic monomer didodecyl methyl allyl ammonium chloride DC 12 MAAC.

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

10. A method for preparing the cyclic structure betaine and double-tailed hydrophobic associating polymer fracturing thickener according to claim 1, characterized in that The method comprises the following process steps: firstly, 1000-1500 mole parts of distilled water are added into a reactor, and then 67.5-83.9 mole parts of acrylamide AM, 15-30 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-2 mole parts of methyldiallylsulfoethyl betaine MDASBA, an emulsifier, a hydrophobic monomer double-tail long-chain alkyl methylallyl ammonium chloride DC are added in sequence under stirring. n MAAC 0.1-0.5 molar part, 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 the initiator is added, and N2 is continued to be passed, and the reaction is carried out under nitrogen protection at 30-60°C for 4-10 hours; after the reaction is completed, the obtained gel product is washed with anhydrous ethanol, and the product is crushed, dried, and sieved to obtain AM / AMES / MDASBA / DC n MAAC tetrapolymer is a fracturing thickener composed of cyclic structure betaine and double-tailed hydrophobic associating polymer.

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