CN117903014A

CN117903014A - Polymerizable monomer and preparation method thereof, polymer thickening agent and preparation method thereof, fracturing fluid and application thereof

Info

Publication number: CN117903014A
Application number: CN202211271540.4A
Authority: CN
Inventors: 陈凯; 崔佳; 王海波; 李凤霞; 史爱萍; 蒋尔梁
Original assignee: China Petroleum and Chemical Corp; Sinopec Exploration and Production Research Institute
Current assignee: China Petroleum and Chemical Corp; Sinopec Exploration and Production Research Institute
Priority date: 2022-10-18
Filing date: 2022-10-18
Publication date: 2024-04-19
Anticipated expiration: 2042-10-18
Also published as: CN117903014B

Abstract

The present invention relates to the field of oilfield chemistry, and discloses a polymerizable monomer and a preparation method thereof, a polymer thickener and a preparation method thereof, a fracturing fluid and an application thereof. The polymerizable monomer has a structure as shown in formula (I), wherein _R1 , _R2 , _R3 and _R4 are each independently hydrogen or a _C1 - _C6 straight-chain or branched alkyl group. The fracturing fluid comprises: water, an inorganic salt and a polymer thickener. The copolymer formed by the polymerization of the zwitterionic polymerizable monomer provided by the present invention and other monomers has a significant anti-polyelectrolyte effect and good salt resistance by utilizing intermolecular hydrogen bonds and electrostatic force interactions, and can be used as a fracturing fluid thickener in a 10-50wt% inorganic salt aqueous solution.

Description

Polymerizable monomer and preparation method thereof, polymer thickening agent and preparation method thereof, fracturing fluid and application thereof

Technical Field

The invention relates to the field of oilfield chemistry, in particular to a polymerizable monomer and a preparation method thereof, a polymer thickener and a preparation method thereof, a fracturing fluid and application thereof.

Background

Hydraulic fracturing is an important means of modifying low permeability reservoirs. With the improvement of the transformation requirement and the continuous progress of the fracturing technology, the volume fracturing technology mainly used for improving the transformation scale is widely applied. In volume fracturing, synthetic polymer fracturing fluids capable of reducing the friction resistance of the fracturing fluid and improving the sand suspending capacity are increasingly receiving attention. Thickeners in synthetic polymer fracturing fluids are critical to system performance.

In the fracturing development practice, the fracturing fluid is required to be prepared with different water qualities in addition to meeting the requirements of reducing friction resistance and improving sand suspending capacity. The high-temperature deep well is also required to have stronger salt tolerance, so that the improvement of the salt tolerance of the fracturing fluid is one of the development directions of the fracturing fluid. The zwitterionic polymer has the characteristic of 'inverse polyelectrolyte effect', has the characteristic of viscosity increase in salt solution, and can be used for preparing fracturing fluid with salt-containing water. The molecular structure of the amphoteric ion polymer generally contains amino, quaternary ammonium ion, carboxyl, sulfo and other groups, and has good water solubility and certain anti-swelling capacity.

The amphoteric ion polymer can be obtained by copolymerizing an anionic monomer and a cationic monomer, can also be obtained by polymerizing a betaine polymerizable monomer, and is found that the copolymer with a betaine inner salt structure has stronger salt tolerance.

CN110256275A discloses a preparation method of a salt-tolerant zwitterionic hydrophobic association polymer and application thereof in fracturing fluid. The preparation method of the hydrophobic association polymer comprises the steps of (1) reacting hexadecylamine with bromohexadecane to obtain an intermediate di-n-hexadecylamine, and then reacting di-n-hexadecylamine with methacryloyl chloride to obtain a polymerizable hydrophobic monomer; (2) The monomer, acrylamide, methacryloxyethyl trimethyl ammonium chloride and 2-acrylamide-2-methylpropanesulfonic acid are subjected to photoinitiated polymerization at room temperature, and are dried and crushed to obtain polymer powder.

CN110483687a discloses a fracturing fluid thickener and a preparation method thereof, comprising monomer, redox initiator, white oil, emulsifier, auxiliary agent, azo initiator and water; the monomer comprises acrylamide, acrylic monomer, 2-acrylamido-2-methylpropanesulfonic acid, salt-resistant monomer and temperature-resistant monomer; the mass ratio of the acrylamide to the acrylic monomer to the 2-acrylamido-2-methylpropanesulfonic acid to the salt-resistant monomer to the temperature-resistant monomer is 100:5-20:20-50:1-10:5-15.

Synthesis and Property studies of acrylamide polymers (Ding Wei, daqing Petroleum institute, 2005:81-85.) disclose the preparation of two sulfobetaines (ammonium acryloyloxyethyl dimethyl propane sulfonate, ammonium methacryloyloxyethyl dimethyl propane sulfonate) and one carboxybetaine (methacryloyloxyethyl dimethyl betaine) and copolymerization with acrylamide.

A process for preparing a salt-tolerant hydrophobic associated polymer prepared from acrylamide, acryloxyethyl trimethyl ammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and a double-tail hydrophobic monomer is disclosed, and its application in fracturing fluid (Mao Jincheng, tian Ji, zhang Wenlong, etc. 2019).

Synthesis and mechanism of action research of salt tackifying betaine type amphiphilic polymers (Zhu Zhou, china university of Petroleum, 2018:16-31.) discloses preparation of N-methyl-N-allyl lauroyl propane sulfonic acid inner salt, and polymerization with acrylamide to obtain acrylamide type betaine type amphiphilic polymers with salt tackifying property.

In the prior art, starting from the preparation of a monomer capable of polymerizing monostaine, a zwitterionic polymer is prepared through copolymerization reaction, and the prepared polymer has low charge density and limited salt tolerance.

Disclosure of Invention

The invention aims to solve the problem of insufficient salt tolerance of fracturing fluid in the prior art, and provides a polymerizable monomer and a preparation method thereof, a polymer thickener and a preparation method thereof, and fracturing fluid and application thereof.

In order to achieve the above object, a first aspect of the present invention provides a polymerizable monomer having a structure represented by formula (I),

Wherein R ₁、R₂、R₃ and R ₄ are each independently hydrogen or C ₁-C₆ linear or branched alkyl.

In a second aspect, the present invention provides a method for preparing a polymerizable monomer, comprising the steps of:

(1) Carrying out a first reaction on lower secondary amine and 1, 3-propane sultone to generate a first intermediate;

(2) Carrying out a second reaction on the first intermediate and epichlorohydrin to generate a second intermediate;

(3) And carrying out a third reaction on the second intermediate and the acryloyl chloride to generate a polymerizable monomer.

In a third aspect, the present invention provides a polymerizable monomer obtainable by the aforementioned process.

The fourth aspect of the invention provides a polymer thickener comprising a structural unit A and a structural unit B; wherein the structural unit A has a structure shown in formula (1), the structural unit B has a structure shown in formula (2),

Wherein R ₁、R₂、R₃、R₄、R₅ and R ₆ are each independently hydrogen or C ₁-C₆ linear or branched alkyl.

In a fifth aspect, the present invention provides a method for preparing a polymeric thickener, the method comprising: polymerizing a monomer shown in a formula (I) and a monomer shown in a formula (II) under polymerization reaction conditions and in the presence of an initiator;

The sixth aspect of the invention provides a polymer thickener obtained by the preparation method.

A seventh aspect of the present invention provides a fracturing fluid comprising: water; an inorganic salt; the polymer thickeners described above.

An eighth aspect of the invention provides the use of a fracturing fluid as hereinbefore described in hydraulic fracturing.

Through the technical scheme, the beneficial technical effects obtained by the invention are as follows:

(1) The polymerizable monomer provided by the invention is a zwitterionic polymerizable monomer and has two betaine structures. The monomer has high charge density, and can improve the salt tolerance of the corresponding polymer.

(2) The invention provides a preparation method of the zwitterionic polymerizable monomer, which has the advantages of easily available raw materials and simple preparation steps.

(3) The copolymer formed by polymerizing the amphoteric ion polymerizable monomer and other monomers provided by the invention has obvious anti-polyelectrolyte effect and good salt resistance by utilizing intermolecular hydrogen bond and electrostatic force interaction, and can be used as a fracturing fluid thickening agent in 10-50wt% of inorganic salt aqueous solution.

Drawings

FIG. 1 is a ¹ H NMR spectrum of the zwitterionic polymerizable monomer 2-acryloyloxy-1, 3-bis (dimethylammonium propane sulfonate betaine) propane prepared in example 1.

FIG. 2 is a graph of the rheology of 0.5wt% polymer thickener in 30wt% CaCl ₂ brine solution at 100℃for 170s ^-1, 90min.

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

The first aspect of the present invention provides a polymerizable monomer having a structure represented by formula (I),

In the present invention, the straight-chain or branched alkyl group of C ₁-C₆ may be, for example, any one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, n-hexyl, and isohexyl.

In some embodiments, R ₁、R₂、R₃ and R ₄ are each independently hydrogen or a linear or branched alkyl group of C ₁-C₄, preferably hydrogen, methyl or ethyl.

In some preferred embodiments, R ₁、R₂、R₃ and R ₄ are both methyl. In this case, the polymerizable monomer is 2-acryloyloxy-1, 3-bis (dimethylammonium propane sulfonate betaine) propane.

The polymerizable monomer is a zwitterionic polymerizable monomer, and has two betaine structures. The monomer has high charge density, and can improve the salt tolerance of the corresponding polymer.

In some embodiments, the lower secondary amine is dimethylamine. At this time, the finally produced polymerizable monomer is 2-acryloyloxy-1, 3-bis (dimethylammonium propane sulfonate betaine) propane.

In some preferred embodiments, the molar ratio of the lower secondary amine to 1, 3-propane sultone is from 0.8 to 1.4:1, for example from 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, and any value in the range of any two values set forth above, preferably from 1 to 1.1:1.

In some preferred embodiments, the first reaction temperature is from 25 to 60 ℃, such as 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃,60 ℃, and any value in the range consisting of any two of the foregoing values, preferably from 30 to 50 ℃; the first reaction time is 4 to 15h, for example 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, and any value in the range of any two values mentioned above, preferably 6 to 12h.

In some preferred embodiments, the molar ratio of the first intermediate to epichlorohydrin is from 1.9 to 2.2:1, for example from 1.9:1, 2:1, 2.1:1, 2.2:1, and any value in the range of any two values recited above, preferably from 2 to 2.05:1.

In some preferred embodiments, the second reaction temperature is from 30 to 70 ℃, such as 30 ℃, 35 ℃, 40 ℃, 45 ℃,50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, and any value in the range consisting of any two of the foregoing values, preferably from 40 to 60 ℃; the second reaction time is 1.5 to 7 hours, for example 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, and any value in the range of any two values mentioned above, preferably 2 to 6 hours.

In some preferred embodiments, the molar ratio of the second intermediate to the acryloyl chloride is in the range of 1:0.8 to 1.2,1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, and any value in the range of any two values recited above, preferably 1:1 to 1.1.

In some preferred embodiments, the third reaction temperature is from 20 to 30 ℃, such as 20 ℃,22 ℃,24 ℃, 26 ℃,28 ℃, 30 ℃, and any value in the range consisting of any two of the foregoing values, preferably from 22 to 28 ℃; the third reaction time is 0.5 to 6 hours, for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, and any value in the range of any two values mentioned above, preferably 1 to 5 hours.

In some preferred embodiments, the preparation of one polymerizable monomer is accomplished by a three-step chemical reaction:

(1) Dimethylamine and 1, 3-propane sultone are subjected to a first reaction to generate a first intermediate 3- (N, N-dimethylamino) propane sulfonic acid, wherein the reaction equation is as follows:

(2) The first intermediate 3- (N, N-dimethylamino) propane sulfonic acid and epichlorohydrin are subjected to a second reaction to generate a second intermediate 2-hydroxy-1, 3-bis (dimethyl ammonium propane sulfonic acid betaine) propane, wherein the reaction equation is as follows:

(3) The second intermediate 2-hydroxy-1, 3-bis (dimethyl ammonium propane sulfonate betaine) propane and acryloyl chloride are subjected to a third reaction to generate a polymerizable monomer 2-acryloyloxy-1, 3-bis (dimethyl ammonium propane sulfonate betaine) propane, wherein the reaction equation is as follows:

According to a particularly preferred embodiment of the present invention, a process for the preparation of a polymerizable monomer comprises the steps of:

(1) Dimethylamine and 1, 3-propane sultone are subjected to a first reaction for 6-12 hours at the temperature of 30-50 ℃ in the molar ratio of 1-1.1:1 to generate a first intermediate;

(2) Carrying out a second reaction on the first intermediate and epichlorohydrin for 2-6h at the temperature of 40-60 ℃ in a molar ratio of 2-2.05:1 to generate a second intermediate;

(3) And carrying out a third reaction on the second intermediate and the acryloyl chloride at the temperature of 22-28 ℃ for 1-5h according to the mol ratio of 1:1-1.1 to obtain the polymerizable monomer.

In some embodiments, the thickener further comprises a structural unit C having a structure represented by formula (3) and/or a structural unit D having a structure represented by formula (4),

Wherein R ₇、R₈、R₁₁ and R ₁₂ are each independently hydrogen or C ₁-C₄ linear or branched alkyl; r ₉ and R ₁₀ are each independently hydrogen or a linear or branched alkyl group of C ₁-C₆ substituted or unsubstituted with hydroxy, and R ₉ and R ₁₀ are not both hydrogen.

In some embodiments, R ₁、R₂、R₃、R₄、R₅ and R ₆ are each independently hydrogen or a linear or branched alkyl group of C ₁-C₄, preferably hydrogen, methyl or ethyl.

In some preferred embodiments, R ₁、R₂、R₃ and R ₄ are both methyl.

In some preferred embodiments, R ₇、R₈、R₁₁ and R ₁₂ are each independently hydrogen, methyl or ethyl.

In some preferred embodiments, R ₇ and R ₈ are not both alkyl.

In some preferred embodiments, R ₁₁ and R ₁₂ are not both alkyl.

In some preferred embodiments, R ₉ and R ₁₀ are each independently hydrogen or a linear or branched alkyl group of C ₁-C₄ substituted or unsubstituted with a hydroxyl group.

In some preferred embodiments, at least one of R ₉ and R ₁₀ is methyl.

In some preferred embodiments, R ₉ or R ₁₀ is hydroxyethyl.

In some preferred embodiments, the structural unit of formula (1) may be a structural unit derived from 2-acryloyloxy-1, 3-bis (dimethylammonium propane sulfonate betaine) propane, the structural unit of formula (2) may be a structural unit derived from acrylamide, the structural unit of formula (3) may be a structural unit derived from N-substituted acrylamide, and the structural unit of formula (4) may be a structural unit derived from N-vinylpyrrolidone.

In the invention, the thickener is a random copolymer, and each structural unit is randomly distributed on the main chain. The above-mentioned structural units A, B, C and D contained in the random copolymer are repeating units formed in the molecular chain of the copolymer by addition polymerization of olefin carbon-carbon double bonds contained in the respective corresponding monomers.

In some embodiments, the molar ratio of building blocks A, B, C and D is from 5 to 25:60 to 80:0 to 25:0 to 25, preferably from 10 to 20:70:0 to 20:0 to 20.

In some preferred embodiments, the thickener has a viscosity average molecular weight of 100X 10 ⁴-800×10⁴ g/mol, preferably 200X 10 ⁴-500×10⁴ g/mol.

In the present invention, the viscosity average molecular weight of the thickener was measured using an Ubbelohde viscometer.

In some embodiments, a 30wt% CaCl ₂ brine solution containing 0.5wt% polymeric thickener has an apparent viscosity of not less than 35 mPas at 100℃for 170s ^-1 under shear for 90 minutes.

In the present invention, apparent viscosity was measured using HAAKE MARS III high temperature rheometer at 100deg.C under 170s ^-1 for 90 min.

In some embodiments, the monomers of the polymerization reaction further comprise a monomer of formula (III) and/or a monomer of formula (IV),

Examples of the straight or branched alkyl group of C ₁-C₆ according to the fifth aspect of the present invention are as described above in the fourth aspect of the present invention, and are not described here.

In some preferred embodiments, R ₁、R₂、R₃ and R ₄ are both methyl.

In some preferred embodiments, R ₇ and R ₈ are not both alkyl.

In some preferred embodiments, R ₁₁ and R ₁₂ are not both alkyl.

In some preferred embodiments, at least one of R ₉ and R ₁₀ is methyl.

In some preferred embodiments, R ₉ or R ₁₀ is hydroxyethyl.

In some preferred embodiments, the monomer of formula (I) is 2-acryloyloxy-1, 3-bis (dimethylammonium propane sulfonate betaine) propane, the monomer of formula (II) is acrylamide, the monomer of formula (III) is N, N-dimethylacrylamide, N-methacrylamide, N-hydroxyethyl acrylamide, and the monomer of formula (IV) is N-vinylpyrrolidone.

In the invention, the salt tolerance of the thickener can be improved by introducing 2-acryloyloxy-1, 3-bis (dimethyl ammonium propane sulfonate betaine) propane with high charge density; by introducing acrylamide, the molecular weight of the copolymer can be increased, and the viscosity of the copolymer in saline solution can be increased; by introducing N, N-dimethylacrylamide, N-methylacrylamide, N-hydroxyethyl acrylamide and N-vinyl pyrrolidone, the hydrolysis rate of the copolymer aqueous solution at high temperature can be reduced, and the salt tolerance of the copolymer aqueous solution at high temperature can be improved.

In some embodiments, the polymerization temperature is from 30 to 60 ℃, such as 30 ℃, 35 ℃,40 ℃,45 ℃,50 ℃, 55 ℃,60 ℃, and any value in the range consisting of any two of the foregoing values, preferably from 40 to 50 ℃; the polymerization time is 3 to 12 hours, for example 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, and any value in the range of any two values mentioned above, preferably 4 to 10 hours.

In some preferred embodiments, the molar ratio of the monomer of formula (I), the monomer of formula (II), the monomer of formula (III) and the monomer of formula (IV) is from 5 to 25:60 to 80:0 to 25:0 to 25, preferably from 10 to 20:70:0 to 20:0 to 20.

In some preferred embodiments, the initiator is selected from at least one of ammonium persulfate, sodium bisulfite, azobisisobutylamidine hydrochloride, and azobisiso Ding Mi, hydrochloride, preferably a complex of ammonium persulfate and sodium bisulfite. The compound of ammonium persulfate and sodium bisulphite is an oxidation/epoxy initiator, so that the polymerization temperature can be obviously reduced, and the molecular weight of the copolymer can be improved. Wherein the mass ratio of ammonium persulfate to sodium bisulfite in the compound of ammonium persulfate and sodium bisulfite is preferably 0.5-2:1, for example 0.5:1, 1:1, 1.5:1, 2:1, and any value in the range of any two values mentioned above, further preferably 1-2:1.

In some preferred embodiments, the initiator is used in an amount of from 0.03 to 0.15wt%, for example from 0.03wt%, 0.05wt%, 0.1wt%, 0.15wt%, and any value in the range of any two values set forth above, preferably from 0.05 to 0.1wt%, based on the total weight of the monomer of formula (I), the monomer of formula (II), and the monomer of formula (III) and/or formula (IV). Too little initiator to initiate polymerization of the monomer; if the initiator is too much, a large amount of radicals are generated, which tends to cause a decrease in the molecular weight of the copolymer and a decrease in the apparent viscosity of the aqueous salt solution of the system.

According to a particularly preferred embodiment of the present invention, a process for the preparation of a polymeric thickener comprises: polymerizing a monomer shown in a formula (I), a monomer shown in a formula (II) and a monomer shown in a formula (III) and/or a monomer shown in a formula (IV) for 4-10h at a temperature of 40-50 ℃ in the presence of an initiator;

Wherein R ₁、R₂、R₃、R₄、R₅ and R ₆ are each independently hydrogen or C ₁-C₄ linear or branched alkyl; r ₇、R₈、R₁₁ and R ₁₂ are each independently hydrogen, methyl or ethyl, and R ₇ and R ₈ are not simultaneously alkyl, and R ₁₁ and R ₁₂ are not simultaneously alkyl; r ₉ and R ₁₀ are each independently hydrogen or a linear or branched alkyl group of C ₁-C₄ substituted or unsubstituted with hydroxy, and R ₉ and R ₁₀ are not both hydrogen;

The molar ratio of the monomer shown in the formula (I), the monomer shown in the formula (II), the monomer shown in the formula (III) and the monomer shown in the formula (IV) is 10-20:70:0-20:0-20;

The initiator is a compound of ammonium persulfate and sodium bisulfite; wherein the mass ratio of ammonium persulfate to sodium bisulfite in the compound of ammonium persulfate and sodium bisulfite is 1-2:1;

The initiator is used in an amount of 0.05 to 0.1wt% based on the total weight of the monomer of formula (I), the monomer of formula (II) and the monomer of formula (III) and/or formula (IV).

In some preferred embodiments, the water is deionized water.

In some preferred embodiments, the inorganic salt is selected from at least one of sodium chloride, potassium chloride, calcium chloride, magnesium chloride, and potassium formate.

In some preferred embodiments, the inorganic salt is used in an amount of 10-50wt%, such as 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, and any value in the range of any two values set forth above, preferably 20-35wt%, of the total mass of the fracturing fluid.

In some preferred embodiments, the fracturing fluid thickener is used in an amount of 0.05 to 1wt%, such as 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, and any value in the range of any two values set forth above, preferably 0.3 to 0.8wt%.

In some preferred embodiments, the fracturing fluid is formulated by: adding a certain amount of inorganic salt into deionized water, stirring and dissolving, adding a certain amount of fracturing fluid thickening agent, and stirring and dissolving for standby.

In practical applications, fracturing fluids may be formulated with different water qualities, such as distilled water, deionized water, ocean water, formation water, and the like.

The polymerizable monomer provided by the invention is a zwitterionic polymerizable monomer and has two betaine structures. The monomer has high charge density, and can improve the salt tolerance of the corresponding polymer. The preparation method has the advantages of easily available raw materials and simple preparation steps. The copolymer formed by polymerizing the amphoteric ion polymerizable monomer and other monomers provided by the invention has obvious anti-polyelectrolyte effect and good salt resistance by utilizing intermolecular hydrogen bond and electrostatic force interaction, and can be used as a fracturing fluid thickening agent in 10-50wt% of inorganic salt aqueous solution.

The following examples and comparative examples were conducted under conventional conditions or conditions recommended by the manufacturer, where specific conditions were not noted. The reagents or apparatus used were conventional products available commercially without the manufacturer's knowledge. The molar ratio relation of each structural unit contained in the prepared thickener product is determined according to the raw material feeding amount.

Example 1

I. Preparation of polymerizable monomers

(1) 0.1Mol of 1, 3-propane sultone and 100mL of deionized water are mixed and dissolved by stirring, and a 40% aqueous solution of dimethylamine 0.1mol is added into a reactor, wherein the molar ratio of dimethylamine to 1, 3-propane sultone is 1:1. 1, 3-propane sultone is slowly dripped into the reactor within 30min, and the temperature is raised to 30 ℃ and the reaction is stirred for 6h. After the reaction, the mixture is distilled under reduced pressure, 50mL of water is added for recrystallization, the filter cake is washed twice by ethanol water solution (1:1), and the mixture is dried in vacuum to obtain a first intermediate 3- (N, N-dimethylamino) propanesulfonic acid, white crystals with the yield of 82 percent.

(2) 100ML of deionized water and 0.1mol of the first intermediate 3- (N, N-dimethylamino) propanesulfonic acid obtained in the step (1) are added into a reactor, 0.1mol of epichlorohydrin is added dropwise, stirring is carried out for 1h after the completion of the dropwise addition, the temperature is raised to 40 ℃ and stirring is carried out for 1h, and 4g of sodium hydroxide and 0.1mol of the first intermediate 3- (N, N-dimethylamino) propanesulfonic acid obtained in the step (1) are added, wherein the mol ratio of the first intermediate to the epichlorohydrin is 2:1. The reaction is carried out for 1h at 40 ℃, and the temperature is raised to 60 ℃ for 1h. After the reaction, the pH value of the solution is regulated to 7.0 by dilute hydrochloric acid, reduced pressure distillation is carried out, the crude product is washed twice by acetone, residues are filtered, the filtrate is distilled under reduced pressure and dried in vacuum, and the second intermediate 2-hydroxy-1, 3-bis (dimethyl ammonium propane sulfobetaine) propane is obtained, and the yield is 91%.

(3) 0.11Mol of acryloyl chloride is added into 100mL of acetone to be uniformly mixed, 0.1mol of 2-hydroxy-1, 3-bis (dimethyl ammonium propane sulfonate betaine) propane serving as the second intermediate obtained in the step (2) is added into a reactor to be uniformly mixed with 100mL of acetone, wherein the mol ratio of the second intermediate to the acryloyl chloride is 1:1.1. Cooling to 5 ℃, slowly dripping the acryloyl chloride solution into the reactor within 30min, uniformly mixing, heating to 22 ℃, and reacting for 5h. Filtering after the reaction is finished, distilling the filtrate under reduced pressure, washing twice by using ethanol/water solution, and vacuum drying to obtain the product, namely, zwitterionic polymerizable monomer 2-acryloyloxy-1, 3-bis (dimethyl ammonium propane sulfonate betaine) propane, wherein ¹ H NMR spectrum is shown in figure 1, and the multiple peaks with chemical shift delta=6.1 can be seen to be attributed to-CH ₂ and-CH groups on olefinic bonds in acryloyloxy groups; the multiple peaks around δ=5.6 are ascribed to the-CH group on the acryloxypropyl group; the multiple peaks around δ=3.8 are ascribed to the-CH ₂ group on the acryloxypropyl group; the multiple peaks around δ=3.6 are attributed to the γ -CH ₂ group attached to the N atom on the propanesulfonic acid group; the single peak at δ=3.3 is attributed to the-CH ₃ group directly attached to the N atom; the multiple peaks around δ=2.8 are attributed to the α -CH ₂ group attached to the sulfonic acid group on the propane sulfonic acid group; the multiple peaks around δ=2.0 are attributed to β -CH ₂ groups on the propane sulfonic acid group.

II, preparing polymer thickener

44G of the polymerizable monomer obtained in the step I, 49g of acrylamide, 20g of N, N-dimethylacrylamide (the molar ratio of the acrylamide to the N, N-dimethylacrylamide is 10:70:20) and 400mL of deionized water are added into a reactor, the solution is stirred to be completely dissolved, the pH value of the solution is regulated to 7.0 by sodium hydroxide, nitrogen is introduced for 30min, 0.08g of ammonium persulfate and 0.04g of sodium bisulfite are sequentially added, the mass ratio of the ammonium persulfate to the sodium bisulfite is 2:1, and the initiator is used for 0.1 weight percent of the total weight of all the monomers. Stopping introducing nitrogen after the solution is obviously thickened, sealing a reaction bottle, reacting for 4 hours at 40 ℃ and reacting for 6 hours at 50 ℃. Washing and soaking the mixture with acetone after the reaction is finished, filtering, vacuum drying the mixture to constant weight, and crushing the mixture to obtain the polymer thickening agent.

III, preparing fracturing fluid

Adding deionized water into CaCl ₂, stirring and dissolving to obtain CaCl ₂ water solution for later use. And (3) taking the polymer thickener obtained in the step (II) and preparing a fracturing fluid by using an aqueous solution of CaCl ₂. Wherein, the consumption of the thickening agent is 0.5wt percent, and the consumption of the inorganic salt is 30wt percent. The rheological curve (temperature-resistant and shearing-resistant curve) of the fracturing fluid is shown in figure 2 (100 ℃,170s ^-1 and 90 min), and the fracturing fluid has good temperature resistance.

Examples 2 to 5

A fracturing fluid was prepared as in example 1. The molar ratios of the materials and the reaction conditions used in each example are shown in Table 1.

TABLE 1

Note that: "a/b" in the tables means that the reaction is carried out under conditions a and then under conditions b. For example, "the reaction temperature is 45 ℃ C./60 ℃ C., the reaction time is 3h/3h" means that the reaction is carried out at 45 ℃ for 3h and then at 60 ℃ for 3h.

Example 6

A fracturing fluid was prepared as in example 1, except that the reactive monomer in step II did not include N-methylacrylamide.

Comparative example 1

A fracturing fluid was prepared as in example 3, except that the polymerizable monomer prepared in accordance with the present invention was not used.

Comparative example 2

A fracturing fluid was prepared as described in example 3, except that N-hydroxyethyl acrylamide was not used.

Test case

The viscosity average molecular weight of the thickener products prepared in the examples and comparative examples was measured by the viscosity method (Ubbelohde viscometer, internal diameter 0.5mm,30 ℃).

And (3) measuring the temperature and shear resistance of the sample in the saline solution by adopting a HAAKE MARS III high-temperature rheometer and shearing for 90min at 100 ℃ for 170s ^-1.

The results are shown in Table 2.

TABLE 2

As can be seen from the results in Table 2, the polymer thickener of the present invention can be obviously thickened in high-concentration saline solution, has good high-temperature stability under high-temperature and high-shear conditions, and shows good salt resistance.

In addition, according to FIG. 2, the fracturing fluid prepared by the invention is sheared for 90min at the temperature of 100 ℃ and the temperature of 170s ^-1, and the apparent viscosity is not less than 35 mPa.s, which indicates that the fracturing fluid of the invention has good temperature resistance and can be applied to reservoirs below 100 ℃.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. A polymerizable monomer, characterized in that the polymerizable monomer has a structure represented by formula (I),

Wherein, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or a C ₁ -C ₆ straight chain or branched chain alkyl group.

2. The polymerizable monomer according to claim 1, wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or a C ₁ -C ₄ straight or branched alkyl group, preferably hydrogen, methyl or ethyl;

Preferably, R ₁ , R ₂ , R ₃ and R ₄ are all methyl groups.

3. A method for preparing a polymerizable monomer, characterized in that it comprises the following steps:

(1) reacting a lower secondary amine with 1,3-propane sultone to generate a first intermediate;

(2) subjecting the first intermediate to a second reaction with epichlorohydrin to generate a second intermediate;

(3) subjecting the second intermediate to a third reaction with acryloyl chloride to generate a polymerizable monomer.

4. The preparation method according to claim 3, wherein the lower secondary amine is dimethylamine;

Preferably, the molar ratio of the lower secondary amine to 1,3-propane sultone is 0.8-1.4:1, preferably 1-1.1:1;

Preferably, the first reaction temperature is 25-60°C, preferably 30-50°C; the first reaction time is 4-15h, preferably 6-12h;

Preferably, the molar ratio of the first intermediate to epichlorohydrin is 1.9-2.2:1, preferably 2-2.05:1;

Preferably, the second reaction temperature is 30-70°C, preferably 40-60°C; the second reaction time is 1.5-7h, preferably 2-6h;

Preferably, the molar ratio of the second intermediate to acryloyl chloride is 1:0.8-1.2, preferably 1:1-1.1;

Preferably, the third reaction temperature is 20-30°C, preferably 22-28°C; the third reaction time is 0.5-6h, preferably 1-5h.

5. A polymerizable monomer obtained by the preparation method according to claim 3 or 4.

6. A polymer thickener, characterized in that the thickener comprises a structural unit A and a structural unit B; wherein the structural unit A has a structure shown in formula (1), and the structural unit B has a structure shown in formula (2),

Wherein, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently hydrogen or a C ₁ -C ₆ straight or branched chain alkyl group.

7. The polymer thickener according to claim 6, wherein the thickener further comprises a structural unit C and/or a structural unit D, wherein the structural unit C has a structure shown in formula (3), and the structural unit D has a structure shown in formula (4),

Wherein, R ₇ , R ₈ , R ₁₁ and R ₁₂ are each independently hydrogen or C ₁ -C ₄ straight or branched alkyl; R ₉ and R ₁₀ are each independently hydrogen or hydroxy-substituted or unsubstituted C ₁ -C ₆ straight or branched alkyl, and R ₉ and R ₁₀ are not hydrogen at the same time.

8. The polymer thickener according to claim 6 or 7, wherein _R1 , _R2 , _R3 , _R4 , _R5 and _R6 are each independently hydrogen or a _C1 - _C4 straight or branched alkyl group, preferably hydrogen, methyl or ethyl;

Preferably, R ₁ , R ₂ , R ₃ and R ₄ are all methyl groups;

Preferably, R ₇ , R ₈ , R ₁₁ and R ₁₂ are each independently hydrogen, methyl or ethyl;

Preferably, R ₇ and R ₈ are not alkyl at the same time;

Preferably, R ₁₁ and R ₁₂ are not alkyl groups at the same time;

Preferably, R ₉ and R ₁₀ are each independently hydrogen or hydroxy substituted or unsubstituted C ₁ -C ₄ straight or branched alkyl;

Preferably, at least one of R ₉ and R ₁₀ is methyl;

Preferably, R ₉ or R ₁₀ is hydroxyethyl.

9. The polymer thickener according to any one of claims 6 to 8, wherein the molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is 5-25:60-80:0-25:0-25, preferably 10-20:70:0-20:0-20;

Preferably, the viscosity average molecular weight of the thickener is 100×10 ⁴ -800×10 ⁴ g/mol, preferably 200×10 ⁴ -500×10 ⁴ g/mol.

10. The polymer thickener according to any one of claims 6 to 9, wherein the apparent viscosity of a 30 wt% _CaCl2 saline solution containing 0.5 wt% of the polymer thickener at 100°C, 170 s ^-1 , and shearing for 90 min is not less than 35 mPa·s.

11. A method for preparing a polymer thickener, characterized in that the preparation method comprises: allowing a monomer represented by formula (I) and a monomer represented by formula (II) to undergo polymerization reaction under polymerization reaction conditions and in the presence of an initiator;

12. The preparation method according to claim 11, wherein the monomers of the polymerization reaction further include a monomer represented by formula (III) and/or a monomer represented by formula (IV),

13. The preparation method according to claim 11 or 12, wherein _R1 , _R2 , _R3 , _R4 , _R5 and _R6 are each independently hydrogen or a _C1 - _C4 straight or branched alkyl group, preferably hydrogen, methyl or ethyl;

Preferably, R ₁ , R ₂ , R ₃ and R ₄ are all methyl groups;

Preferably, R ₇ and R ₈ are not alkyl at the same time;

Preferably, R ₁₁ and R ₁₂ are not alkyl groups at the same time;

Preferably, at least one of R ₉ and R ₁₀ is methyl;

Preferably, R ₉ or R ₁₀ is hydroxyethyl.

14. The preparation method according to any one of claims 11 to 13, wherein the polymerization reaction temperature is 30-60°C, preferably 40-50°C; the polymerization reaction time is 3-12h, preferably 4-10h;

Preferably, the molar ratio of the monomer represented by formula (I), the monomer represented by formula (II), the monomer represented by formula (III) and the monomer represented by formula (IV) is 5-25:60-80:0-25:0-25, preferably 10-20:70:0-20:0-20;

Preferably, the initiator is selected from at least one of ammonium persulfate, sodium bisulfite, azobis(isobutyl)amidine hydrochloride and azobis(isobutyl)imidazoline hydrochloride, preferably a complex of ammonium persulfate and sodium bisulfite; wherein the mass ratio of ammonium persulfate to sodium bisulfite in the complex of ammonium persulfate and sodium bisulfite is preferably 0.5-2:1, more preferably 1-2:1;

Preferably, the amount of the initiator used is 0.03-0.15 wt %, preferably 0.05-0.1 wt %, of the total weight of the monomer represented by formula (I), the monomer represented by formula (II) and the monomer represented by formula (III) and/or formula (IV).

15. A polymer thickener obtained by the preparation method according to any one of claims 11 to 14.

16. A fracturing fluid, comprising:

Water; inorganic salt; and a polymer thickener as claimed in any one of claims 6-10 and 15;

Preferably, the water is deionized water;

Preferably, the inorganic salt is selected from at least one of sodium chloride, potassium chloride, calcium chloride, magnesium chloride and potassium formate;

Preferably, the amount of the inorganic salt is 10-50wt% of the total mass of the fracturing fluid, preferably 20-30wt%;

Preferably, the amount of the polymer thickener used accounts for 0.05-1 wt%, preferably 0.3-0.8 wt%, of the total mass of the fracturing fluid.

17. Use of the fracturing fluid according to claim 16 in hydraulic fracturing.