Polymerizable monomers and methods for their preparation, polymer viscosifiers and methods for their preparation, and fracturing fluids and uses thereof

Abstract

The application relates to the field of oil field chemistry, and discloses a polymerizable monomer and a preparation method thereof, a polymer thickening agent and a preparation method thereof, and a fracturing fluid and application thereof. The polymerizable monomer has a structure shown in formula (I), wherein R1, R2, R3 and R4 are each independently hydrogen or a C1-C6 linear or branched alkyl. The fracturing fluid comprises water, inorganic salts and the polymer thickening agent. The copolymer formed by polymerization of the zwitterionic polymerizable monomer and other monomers has a significant antipolyelectrolyte effect and good salt tolerance by utilizing intermolecular hydrogen bonds and electrostatic force interaction, and can be used as a fracturing fluid thickening agent in a 10-50 wt% inorganic salt aqueous solution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oilfield chemicals, in particular to a polymerizable monomer and a preparation method thereof, a polymer thickening agent and a preparation method thereof, and a fracturing fluid and application thereof. BACKGROUND

[0002] Hydraulic fracturing is an important means for improving low-permeability oil and gas reservoirs. With the increasing demand for improvement and the continuous progress of fracturing technology, volume fracturing technology, which mainly improves the scale of transformation, has been widely used. In volume fracturing, synthetic polymer fracturing fluid, which can reduce the friction of fracturing fluid and improve the sand-carrying capacity, is increasingly valued by people. The thickening agent in the synthetic polymer fracturing fluid is the key to the performance of the system.

[0003] In the practice of fracturing development, in addition to meeting the requirements of reducing friction and improving sand-carrying capacity, the fracturing fluid is also required to be prepared with different water quality. For high-temperature deep wells, the fracturing fluid is also required to have strong salt tolerance, so improving the salt tolerance of the fracturing fluid has become one of the directions of fracturing fluid development. Zwitterionic polymers have "counterion effect" and have the characteristic of viscosity increase in salt solution, which can be used to prepare fracturing fluid with salt-containing water. Zwitterionic polymer molecular structure usually contains amine groups, quaternary ammonium ions, carboxyl groups, sulfonic groups and other groups, which have good water solubility and certain anti-swelling ability.

[0004] Zwitterionic polymers can be obtained by copolymerization of anionic monomers and cationic monomers, or by polymerization of betaine polymerizable monomers. Research has found that copolymers with betaine internal salt structure have stronger salt tolerance.

[0005] CN110256275A discloses a preparation method of a salt-tolerant zwitterionic hydrophobic associating polymer and its application in fracturing fluid. The preparation method of the hydrophobic associating polymer includes (1) first, an intermediate di-n-hexadecylamine is obtained by reacting hexadecylamine with bromohexadecane, and then a polymerizable hydrophobic monomer is obtained by reacting the di-n-hexadecylamine with methacryloyl chloride; (2) the monomer is subjected to photoinitiated polymerization with acrylamide, methacryloyloxyethyl trimethylammonium chloride and 2-acrylamido-2-methylpropanesulfonic acid at room temperature, and after drying and crushing, a polymer powder is obtained.

[0006] CN110483687A discloses a fracturing fluid thickening agent and a preparation method thereof, which comprises a monomer, an oxidation-reduction initiator, white oil, an emulsifier, an additive, an azo initiator and water; the monomer comprises acrylamide, an acrylic monomer, 2-acrylamido-2-methylpropanesulfonic acid, a salt-resistant monomer and a temperature-resistant monomer; the mass ratio of the acrylamide, the acrylic monomer, the 2-acrylamido-2-methylpropanesulfonic acid, the salt-resistant monomer and the temperature-resistant monomer is 100:5-20:20-50:1-10:5-15.

[0007] "Synthesis and Properties of Acrylamide Polymers" (Ding Wei, Daqing Petroleum College, 2005: 81-85.) discloses the preparation of two sulfobetaines (ammonium acryloyloxyethyl dimethyl propyl sulfonate, methacryloyloxyethyl dimethyl propyl sulfonate) and one carboxybetaine (methacryloyloxyethyl dimethyl betaine), and copolymerization with acrylamide.

[0008] "Preparation Method of Salt-tolerant Zwitterionic Hydrophobic Association Polymer and Application in Fracturing Fluid" (Mao Jincheng, Tian Jizhen, Zhang Wenlong, et al., 2019) discloses a preparation method of zwitterionic hydrophobic association polymer, which is prepared by acrylamide, acryloyloxyethyl trimethyl ammonium chloride, 2-acrylamido-2-methyl propyl sulfonic acid and a double-tailed hydrophobic monomer.

[0009] "Synthesis and Mechanism of Salt-thickening Betaine-type Amphiphilic Polymer" (Zhu Zhou, China University of Petroleum, 2018: 16-31.) discloses the preparation of N-methyl-N-allyl lauryl propyl sulfonate inner salt, and polymerization with acrylamide to obtain acrylamide betaine-type amphiphilic polymer with salt-thickening properties.

[0010] The prior art starts from the preparation of single betaine polymerizable monomer, and prepares zwitterionic polymer through copolymerization reaction. The charge density of the prepared polymer is not high, and the salt tolerance is limited. SUMMARY

[0011] The purpose of the present application is to overcome the problem of insufficient salt tolerance of fracturing fluid in the prior art, and to provide a polymerizable monomer and a preparation method thereof, a polymer thickening agent and a preparation method thereof, and a fracturing fluid and its application.

[0012] In order to achieve the above purpose, the first aspect of the present application provides a polymerizable monomer, which has the structure shown in formula (I),

[0013]

[0014] wherein R1, R2, R3 and R4 are each independently hydrogen or C1-C6 linear or branched alkyl.

[0015] The second aspect of the present application provides a preparation method of a polymerizable monomer, comprising the following steps:

[0016] (1) a first intermediate is generated by first reacting a lower secondary amine with 1,3-propane sultone;

[0017] (2) a second intermediate is generated by second reacting the first intermediate with epichlorohydrin;

[0018] (3) The second intermediate is reacted with acryloyl chloride in a third reaction to generate a polymerizable monomer.

[0019] A third aspect of the present invention provides a polymerizable monomer obtained by the aforementioned preparation method.

[0020] A fourth aspect of the present invention provides a polymer thickener comprising structural unit A and structural unit B; wherein structural unit A has the structure shown in formula (1), and structural unit B has the structure shown in formula (2).

[0021]

[0022] R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C6 straight-chain or branched alkyl groups.

[0023] The fifth aspect of the present invention provides a method for preparing a polymer thickener, the method comprising: subjecting a monomer shown in formula (I) and a monomer shown in formula (II) to a polymerization reaction under polymerization reaction conditions and in the presence of an initiator;

[0024]

[0025] R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C6 straight-chain or branched alkyl groups.

[0026] The sixth aspect of the present invention provides a polymer thickener obtained by the aforementioned preparation method.

[0027] A seventh aspect of the present invention provides a fracturing fluid comprising: water; an inorganic salt; and the aforementioned polymer thickener.

[0028] The eighth aspect of the present invention provides the application of the aforementioned fracturing fluid in hydraulic fracturing.

[0029] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0030] (1) The polymerizable monomer provided by this invention is an amphoteric polymerizable monomer with two betaine structures. The monomer has a high charge density, which can improve the salt resistance of the corresponding polymer.

[0031] (2) The present invention provides a method for preparing the above-mentioned zwitterionic polymerizable monomer. The raw materials are readily available and the preparation steps are simple.

[0032] (3) The copolymers formed by the polymerization of zwitterionic polymerizable monomers and other monomers provided by the present invention have significant anti-polyelectrolyte effect and good salt resistance by utilizing intermolecular hydrogen bonds and electrostatic interactions. They can be used as fracturing fluid thickeners in 10-50wt% inorganic salt aqueous solutions. Attached Figure Description

[0033] Figure 1 It is the zwitterionic polymerizable monomer 2-acryloyloxy-1,3-bis(dimethylammonium propanesulfonate betaine)propane prepared in Example 1. 1 H NMR spectrum.

[0034] Figure 2 This is the rheological curve of 0.5 wt% polymer thickener in 30 wt% CaCl2 aqueous solution, 100℃, 170 s. -1 90 minutes. Detailed Implementation

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] A first aspect of the present invention provides a polymerizable monomer having the structure shown in formula (I).

[0037]

[0038] R1, R2, R3 and R4 are each independently hydrogen or C1-C6 straight-chain or branched alkyl groups.

[0039] In this invention, examples of the C1-C6 straight-chain or branched alkyl groups can 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.

[0040] In some embodiments, R1, R2, R3 and R4 are each independently hydrogen or a C1-C4 straight-chain or branched alkyl group, preferably hydrogen, methyl or ethyl.

[0041] In some preferred embodiments, R1, R2, R3, and R4 are all methyl groups. In this case, the polymerizable monomer is 2-acryloyloxy-1,3-bis(dimethylammonium propanesulfonate betaine)propane.

[0042] The polymerizable monomer described in this invention is an amphoteric polymerizable monomer with two betaine structures. This monomer has a high charge density, which can improve the salt resistance of the corresponding polymer.

[0043] A second aspect of the present invention provides a method for preparing a polymerizable monomer, comprising the following steps:

[0044] (1) A lower secondary amine is reacted with 1,3-propanesulfonic acid lactone to generate a first intermediate;

[0045] (2) The first intermediate is reacted with epichlorohydrin to generate the second intermediate;

[0046] (3) The second intermediate is reacted with acryloyl chloride in a third reaction to generate a polymerizable monomer.

[0047] In some embodiments, the lower secondary amine is dimethylamine. In this case, the final polymerizable monomer is 2-acryloyloxy-1,3-bis(dimethylammonium propanesulfonate betaine)propane.

[0048] In some preferred embodiments, the molar ratio of the lower secondary amine to 1,3-propanesulfonic acid lactone is 0.8-1.4:1, for example 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, and any value within the range of any two of the above values, preferably 1-1.1:1.

[0049] In some preferred embodiments, the first reaction temperature is 25-60°C, for example 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, and any value within the range of any two of the above values, preferably 30-50°C; the first reaction time is 4-15h, for example 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, and any value within the range of any two of the above values, preferably 6-12h.

[0050] In some preferred embodiments, the molar ratio of the first intermediate to epichlorohydrin is 1.9-2.2:1, for example 1.9:1, 2:1, 2.1:1, 2.2:1, and any value within the range of any two of the above values, preferably 2-2.05:1.

[0051] In some preferred embodiments, the second reaction temperature is 30-70°C, for example, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or any value within the range of any two of the above values, preferably 40-60°C; the second reaction time is 1.5-7h, for example, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, or any value within the range of any two of the above values, preferably 2-6h.

[0052] In some preferred embodiments, the molar ratio of the second intermediate to acryloyl chloride is 1:0.8-1.2, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, or any value within the range of any two of the above values, preferably 1:1-1.1.

[0053] In some preferred embodiments, the third reaction temperature is 20-30°C, for example 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, and any value within the range of any two of the above values, preferably 22-28°C; the third reaction time is 0.5-6h, for example 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, and any value within the range of any two of the above values, preferably 1-5h.

[0054] In some preferred embodiments, the preparation of a polymerizable monomer is achieved through a three-step chemical reaction:

[0055] (1) Dimethylamine is reacted with 1,3-propanesulfonic acid lactone to generate the first intermediate 3-(N,N-dimethylamino)propanesulfonic acid. The reaction equation is as follows:

[0056]

[0057] (2) The first intermediate 3-(N,N-dimethylamino)propanesulfonic acid is reacted with epichlorohydrin in a second reaction to generate the second intermediate 2-hydroxy-1,3-bis(dimethylammonium propanesulfonate betaine)propane. The reaction equation is as follows:

[0058]

[0059] (3) The second intermediate 2-hydroxy-1,3-bis(dimethylammonium propanesulfonate betaine)propane is reacted with acryloyl chloride in a third reaction to generate the polymerizable monomer 2-acryloyloxy-1,3-bis(dimethylammonium propanesulfonate betaine)propane. The reaction equation is as follows:

[0060]

[0061] According to a particularly preferred embodiment of the present invention, a method for preparing a polymerizable monomer includes the following steps:

[0062] (1) Dimethylamine and 1,3-propanesulfonic acid lactone were reacted at a molar ratio of 1-1.1:1 at 30-50℃ for 6-12 hours to generate the first intermediate;

[0063] (2) The first intermediate is reacted with epichlorohydrin at a molar ratio of 2-2.05:1 at 40-60°C for 2-6 hours to generate the second intermediate;

[0064] (3) The second intermediate and acryloyl chloride are reacted at a molar ratio of 1:1-1.1 at 22-28℃ for 1-5 hours to generate a polymerizable monomer.

[0065] A third aspect of the present invention provides a polymerizable monomer obtained by the aforementioned preparation method.

[0066] A fourth aspect of the present invention provides a polymer thickener comprising structural unit A and structural unit B; wherein structural unit A has the structure shown in formula (1), and structural unit B has the structure shown in formula (2).

[0067]

[0068] R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C6 straight-chain or branched alkyl groups.

[0069] In some embodiments, the thickener further includes structural unit C and / or structural unit D, wherein structural unit C has the structure shown in formula (3) and structural unit D has the structure shown in formula (4).

[0070]

[0071] Among them, R7, R8, R 11 and R 12 Each is independently hydrogen or a C1-C4 straight-chain or branched alkyl group; R9 and R 10 Each is independently a C1-C6 straight-chain or branched alkyl group, either hydrogen- or hydroxyl-substituted or unsubstituted, and R9 and R 10 They are not both hydrogen.

[0072] In this invention, examples of the C1-C6 straight-chain or branched alkyl groups can 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.

[0073] In some embodiments, R1, R2, R3, R4, R5 and R6 are each independently hydrogen or a straight-chain or branched alkyl group of C1-C4, preferably hydrogen, methyl or ethyl.

[0074] In some preferred embodiments, R1, R2, R3 and R4 are all methyl groups.

[0075] In some preferred embodiments, R7, R8, R 11 and R 12 Each can be independently hydrogen, methyl, or ethyl.

[0076] In some preferred embodiments, R7 and R8 are not both alkyl groups.

[0077] In some preferred embodiments, R 11 and R 12 They are not both alkyl groups.

[0078] In some preferred embodiments, R9 and R 10 Each is a C1-C4 straight-chain or branched alkyl group, which may be substituted with or unsubstituted with hydrogen or hydroxyl groups.

[0079] In some preferred embodiments, R9 and R 10 At least one of them is methyl.

[0080] In some preferred embodiments, R9 or R 10 It is hydroxyethyl.

[0081] In some preferred embodiments, the structural unit shown in formula (1) can be a structural unit from 2-acryloyloxy-1,3-bis(dimethylammonium propanesulfonic acid betaine)propane, the structural unit shown in formula (2) can be a structural unit from acrylamide, the structural unit shown in formula (3) can be a structural unit from N-substituted acrylamide, and the structural unit shown in formula (4) can be a structural unit from N-vinylpyrrolidone.

[0082] In this invention, the thickener is a random copolymer, in which the structural units are randomly distributed along the main chain. The structural units A, B, C, and D contained in the random copolymer are repeated units formed in the molecular chain of the copolymer through addition polymerization of the olefin carbon-carbon double bonds contained in their respective monomers.

[0083] In some embodiments, 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.

[0084] In some preferred embodiments, the thickener has a viscosity-average molecular weight of 100 × 10⁻⁶. 4 -800×10 4 g / mol, preferably 200 × 10⁻⁶ g / mol, 4 -500×10 4 g / mol.

[0085] In this invention, the viscosity-average molecular weight of the thickener is tested using an Ubbelohde viscometer.

[0086] In some embodiments, a 30 wt% CaCl2 aqueous solution containing 0.5 wt% polymer thickener is heated at 100°C for 170 seconds. -1The apparent viscosity after 90 min of shearing is not less than 35 mPa·s.

[0087] In this invention, the apparent viscosity was measured using a HAAKE Mars III high-temperature rheometer at 100°C for 170 seconds. -1 The test was conducted under 90-minute conditions.

[0088] The fifth aspect of the present invention provides a method for preparing a polymer thickener, the method comprising: subjecting a monomer shown in formula (I) and a monomer shown in formula (II) to a polymerization reaction under polymerization reaction conditions and in the presence of an initiator;

[0089]

[0090] R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C6 straight-chain or branched alkyl groups.

[0091] In some embodiments, the monomers of the polymerization reaction further include the monomers shown in formula (III) and / or formula (IV).

[0092]

[0093] Among them, R7, R8, R 11 and R 12 Each is independently hydrogen or a C1-C4 straight-chain or branched alkyl group; R9 and R 10 Each is independently a C1-C6 straight-chain or branched alkyl group, either hydrogen- or hydroxyl-substituted or unsubstituted, and R9 and R 10 They are not both hydrogen.

[0094] Examples of C1-C6 straight-chain or branched alkyl groups described in the fifth aspect of the present invention are as described in the fourth aspect of the present invention above, and will not be repeated here.

[0095] In some embodiments, R1, R2, R3, R4, R5 and R6 are each independently hydrogen or a straight-chain or branched alkyl group of C1-C4, preferably hydrogen, methyl or ethyl.

[0096] In some preferred embodiments, R1, R2, R3 and R4 are all methyl groups.

[0097] In some preferred embodiments, R7, R8, R 11 and R 12 Each can be independently hydrogen, methyl, or ethyl.

[0098] In some preferred embodiments, R7 and R8 are not both alkyl groups.

[0099] In some preferred embodiments, R 11 and R12 They are not both alkyl groups.

[0100] In some preferred embodiments, R9 and R 10 Each is a C1-C4 straight-chain or branched alkyl group, which may be substituted with or unsubstituted with hydrogen or hydroxyl groups.

[0101] In some preferred embodiments, R9 and R 10 At least one of them is methyl.

[0102] In some preferred embodiments, R9 or R 10 It is hydroxyethyl.

[0103] In some preferred embodiments, the monomer shown in formula (I) is 2-acryloyloxy-1,3-bis(dimethylammonium propanesulfonate betaine)propane, the monomer shown in formula (II) is acrylamide, the monomer shown in formula (III) is N,N-dimethylacrylamide, N-methylacrylamide, N-hydroxyethylacrylamide, and the monomer shown in formula (IV) is N-vinylpyrrolidone.

[0104] In this invention, the salt resistance of the thickener can be improved by introducing 2-acryloyloxy-1,3-bis(dimethylammonium propanesulfonate betaine)propane, which has a high charge density; the molecular weight of the copolymer can be increased by introducing acrylamide, thereby increasing its viscosity in salt water solutions; and the hydrolysis rate of the copolymer aqueous solution at high temperatures can be reduced by introducing N,N-dimethylacrylamide, N-methylacrylamide, N-hydroxyethylacrylamide, and N-vinylpyrrolidone, thereby improving its salt resistance at high temperatures.

[0105] In some embodiments, the polymerization reaction temperature is 30-60°C, for example 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, and any value within the range of any two of the above values, preferably 40-50°C; the polymerization reaction time is 3-12h, for example 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, and any value within the range of any two of the above values, preferably 4-10h.

[0106] In some preferred embodiments, the molar ratio of the monomer shown in formula (I), the monomer shown in formula (II), the monomer shown in formula (III), and the monomer shown in formula (IV) is 5-25:60-80:0-25:0-25, preferably 10-20:70:0-20:0-20.

[0107] In some preferred embodiments, the initiator is selected from at least one of ammonium persulfate, sodium bisulfite, azobisisobutylamidine hydrochloride, and azobisisobutylimidazoline hydrochloride, preferably a complex of ammonium persulfate and sodium bisulfite. The ammonium persulfate and sodium bisulfite complex is an oxidizing / epoxy initiator, which can significantly reduce the polymerization temperature and increase the molecular weight of the copolymer. The mass ratio of ammonium persulfate to sodium bisulfite in the complex is preferably 0.5-2:1, for example, 0.5:1, 1:1, 1.5:1, 2:1, and any value within the range of any two of the above values, more preferably 1-2:1.

[0108] In some preferred embodiments, the amount of initiator is 0.03-0.15 wt% of the total weight of the monomers shown in formula (I), formula (II), and formulas (III) and / or formula (IV), for example, 0.03 wt%, 0.05 wt%, 0.1 wt%, 0.15 wt%, and any value within the range of any two of the above values, preferably 0.05-0.1 wt%. If the initiator is too small, monomer polymerization cannot be initiated; if the initiator is too large, a large number of free radicals are generated, which easily leads to a decrease in the molecular weight of the copolymer and a decrease in the apparent viscosity of the brine solution of the system.

[0109] According to a particularly preferred embodiment of the present invention, a method for preparing a polymer thickener includes: subjecting the monomers shown in formula (I), formula (II), formula (III), and / or formula (IV) to a polymerization reaction at 40-50°C and in the presence of an initiator for 4-10 hours.

[0110]

[0111]

[0112] Among them, R1, R2, R3, R4, R5, and R6 are each independently hydrogen or C1-C4 straight-chain or branched alkyl groups; R7, R8, and R6 are... 11 and R 12 Each is independently hydrogen, methyl, or ethyl, and R7 and R8 are not simultaneously alkyl. 11 and R 12 Not both are alkyl groups; R9 and R 10 Each is independently a C1-C4 straight-chain or branched alkyl group, either hydrogen- or hydroxyl-substituted or unsubstituted, and R9 and R 10 They are not both hydrogen;

[0113] The molar ratio of the monomer shown in formula (I), the monomer shown in formula (II), the monomer shown in formula (III), and the monomer shown in formula (IV) is 10-20:70:0-20:0-20;

[0114] The initiator is a complex of ammonium persulfate and sodium bisulfite; wherein the mass ratio of ammonium persulfate to sodium bisulfite in the complex is 1-2:1.

[0115] The amount of the initiator is 0.05-0.1 wt% of the total weight of the monomers shown in formula (I), formula (II), and formulas (III) and / or (IV).

[0116] The sixth aspect of the present invention provides a polymer thickener obtained by the aforementioned preparation method.

[0117] A seventh aspect of the present invention provides a fracturing fluid comprising: water; an inorganic salt; and the aforementioned polymer thickener.

[0118] In some preferred embodiments, the water is deionized water.

[0119] 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.

[0120] In some preferred embodiments, the amount of inorganic salt is 10-50 wt% of the total mass of the fracturing fluid, for example 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, and any value within the range of any two of the above values, preferably 20-35 wt%.

[0121] In some preferred embodiments, the amount of the fracturing fluid thickener accounts for 0.05-1 wt% of the total mass of the fracturing fluid, for example, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, and any value within any range of any two of the above values, preferably 0.3-0.8 wt%.

[0122] In some preferred embodiments, the fracturing fluid is prepared by adding a certain amount of inorganic salt to deionized water, stirring to dissolve it, then adding a certain amount of fracturing fluid thickener, stirring to dissolve it, and then setting it aside for later use.

[0123] In practical applications, fracturing fluids can be prepared using different water qualities, such as distilled water, deionized water, ocean water, and formation water.

[0124] The eighth aspect of the present invention provides the application of the aforementioned fracturing fluid in hydraulic fracturing.

[0125] The polymerizable monomer provided by this invention is an amphoteric polymerizable monomer with two betaine structures. This monomer has a high charge density, which can improve the salt resistance of the corresponding polymer. Its preparation method uses readily available raw materials and involves simple steps. The copolymers formed by polymerizing the amphoteric polymerizable monomer provided by this invention with other monomers exhibit significant anti-polyelectrolyte effects and good salt resistance through intermolecular hydrogen bonding and electrostatic interactions, and can be used as fracturing fluid thickeners in 10-50 wt% inorganic salt aqueous solutions.

[0126] Unless otherwise specified in the following examples and comparative examples, conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products. The molar ratio of the structural units in the resulting thickener product was determined based on the amount of raw materials fed.

[0127] Example 1

[0128] I. Preparation of polymerizable monomers

[0129] (1) Mix 0.1 mol of 1,3-propanesulfonic acid lactone with 100 mL of deionized water and stir to dissolve. Add 0.1 mol of 40% dimethylamine aqueous solution to the reactor, wherein the molar ratio of dimethylamine to 1,3-propanesulfonic acid lactone is 1:1. Slowly add 1,3-propanesulfonic acid lactone dropwise to the reactor over 30 min, and heat to 30 °C and stir for 6 h. After the reaction is complete, distill under reduced pressure, add 50 mL of water for recrystallization, wash the filter cake twice with an ethanol-water solution (1:1), and dry under vacuum to obtain the first intermediate 3-(N,N-dimethylamino)propanesulfonic acid, a white crystal with a yield of 82%.

[0130] (2) Add 100 mL of deionized water and 0.1 mol of the first intermediate 3-(N,N-dimethylamino)propanesulfonic acid obtained in step (1) to the reactor, and add 0.1 mol of epichlorohydrin dropwise. After the addition is complete, stir for 1 h, raise the temperature to 40 °C and stir for 1 h, then add 4 g of sodium hydroxide and 0.1 mol of the first intermediate 3-(N,N-dimethylamino)propanesulfonic acid obtained in step (1), wherein the molar ratio of the first intermediate to epichlorohydrin is 2:1. React at 40 °C for 1 h, and then raise the temperature to 60 °C and react for 1 h. After the reaction is complete, adjust the pH of the solution to 7.0 with dilute hydrochloric acid, distill under reduced pressure, wash the crude product twice with acetone, filter the residue, distill the filtrate under reduced pressure, and dry under vacuum to obtain the second intermediate 2-hydroxy-1,3-bis(dimethylammonium propanesulfonic acid betaine)propane, with a yield of 91%.

[0131] (3) 0.11 mol of acryloyl chloride was added to 100 mL of acetone and mixed thoroughly. Then, 0.1 mol of the second intermediate obtained in step (2), 2-hydroxy-1,3-di(dimethylammonium propanesulfonic acid betaine)propane, and 100 mL of acetone were added to the reactor and mixed thoroughly. The molar ratio of the second intermediate to acryloyl chloride was 1:1.1. The temperature was lowered to 5°C, and the acryloyl chloride solution was slowly added dropwise to the reactor over 30 min. After mixing thoroughly, the temperature was raised to 22°C, and the reaction was carried out for 5 h. After the reaction was completed, the mixture was filtered, and the filtrate was distilled under reduced pressure, washed twice with ethanol / water solution, and dried under vacuum to obtain the zwitterionic polymerizable monomer 2-acryloyloxy-1,3-di(dimethylammonium propanesulfonic acid betaine)propane. 1 The H NMR spectrum is shown in [reference]. Figure 1 It can be seen that the multiplet at chemical shift δ = 6.1 belongs to the -CH2 and -CH groups on the olefin bond of the acryloyloxy group; the multiplet near δ = 5.6 belongs to the -CH group on the acryloyloxypropyl group; the multiplet near δ = 3.8 belongs to the -CH2 group on the acryloyloxypropyl group; the multiplet near δ = 3.6 belongs to the γ-CH2 group attached to the N atom on the propanesulfonic acid group; the singlet at δ = 3.3 belongs to the -CH3 group directly attached to the N atom; the multiplet near δ = 2.8 belongs to the α-CH2 group attached to the sulfonic acid group on the propanesulfonic acid group; and the multiplet near δ = 2.0 belongs to the β-CH2 group on the propanesulfonic acid group.

[0132] II. Preparation of Polymer Thickeners

[0133] Add 44g of the polymerizable monomer obtained in step I, 49g of acrylamide, and 20g of N,N-dimethylacrylamide (molar ratio of 10:70:20) to the reactor, along with 400mL of deionized water. Stir until the monomers are completely dissolved. Adjust the pH of the solution to 7.0 with sodium hydroxide. Purge with nitrogen for 30 minutes. Then, add 0.08g of ammonium persulfate and 0.04g of sodium bisulfite sequentially, with a mass ratio of ammonium persulfate to sodium bisulfite of 2:1. The initiator amount is 0.1wt% of the total weight of all monomers. Stop purging with nitrogen after the solution has thickened significantly. Seal the reaction flask and react at 40°C for 4 hours, then at 50°C for 6 hours. After the reaction, wash and soak with acetone, filter, and vacuum dry to constant weight. Crush to obtain the polymer thickener.

[0134] III. Preparation of fracturing fluid

[0135] Take deionized water, add CaCl2, stir to dissolve, and obtain a CaCl2 aqueous solution for later use. Take the polymer thickener obtained in step II and prepare a fracturing fluid with the CaCl2 aqueous solution. The amount of thickener is 0.5 wt%, and the amount of inorganic salt is 30 wt%. The rheological curve (temperature and shear resistance curve) of this fracturing fluid is shown in [reference needed]. Figure 2(100℃, 170s) -1 (90 min), it can be seen that the fracturing fluid has good temperature resistance.

[0136] Examples 2-5

[0137] Fracturing fluid was prepared according to the method of Example 1. The molar ratios of materials and reaction conditions used in each example are shown in Table 1.

[0138] Table 1

[0139]

[0140]

[0141] Note: "a / b" in the table indicates that the reaction is carried out first under condition a and then under condition b. For example, "reaction temperature is 45℃ / 60℃, reaction time is 3h / 3h" means that the reaction is carried out first at 45℃ for 3h and then at 60℃ for 3h.

[0142] Example 6

[0143] The fracturing fluid was prepared according to the method of Example 1, except that the reaction monomer in step II did not include N-methylacrylamide.

[0144] Comparative Example 1

[0145] The fracturing fluid was prepared according to the method of Example 3, except that the polymerizable monomer prepared in this invention was not used.

[0146] Comparative Example 2

[0147] The fracturing fluid was prepared according to the method in Example 3, except that N-hydroxyethylacrylamide was not used.

[0148] Test case

[0149] The viscosity-average molecular weight of the thickener products prepared in the examples and comparative examples was tested using the viscosity method (Ubbelohde viscometer, inner diameter 0.5 mm, 30 °C).

[0150] Using a HAAKE Mars III high-temperature rheometer, at 100℃ for 170s... -1 The temperature and shear resistance of the sample in a salt solution was determined by shearing for 90 minutes.

[0151] The results are shown in Table 2.

[0152] Table 2

[0153]

[0154] As can be seen from the results in Table 2, the polymer thickener described in this invention can significantly thicken the solution in high-concentration salt water, exhibits good high-temperature stability under high-temperature and high-shear conditions, and demonstrates good salt resistance.

[0155] In addition, according to Figure 2 The fracturing fluid prepared by this invention can withstand 100°C for 170 seconds. -1 After shearing for 90 minutes, the apparent viscosity is not less than 35 mPa·s, indicating that the fracturing fluid of the present invention has good temperature resistance and can be applied in reservoirs below 100℃.

[0156] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polymerizable monomer, characterized in that, The polymerizable monomer has the structure shown in formula (I). Formula (I) R1, R2, R3 and R4 are each independently hydrogen or C1-C6 straight-chain or branched alkyl groups.

2. The polymerizable monomer according to claim 1, wherein, R1, R2, R3 and R4 are each independently hydrogen or C1-C4 straight-chain or branched alkyl groups.

3. The polymerizable monomer according to claim 2, wherein, R1, R2, R3, and R4 are each independently hydrogen, methyl, or ethyl.

4. The polymerizable monomer according to claim 3, wherein, R1, R2, R3, and R4 are all methyl groups.

5. A method for preparing a polymerizable monomer according to any one of claims 1-4, characterized in that, Includes the following steps: (1) A lower secondary amine is reacted with 1,3-propanesulfonic acid lactone in a first reaction to generate a first intermediate; (2) The first intermediate is reacted with epichlorohydrin in a second reaction to generate a second intermediate; (3) The second intermediate is reacted with acryloyl chloride in a third reaction to generate a polymerizable monomer.

6. The preparation method according to claim 5, wherein, The lower secondary amine is dimethylamine.

7. The preparation method according to claim 5, wherein, The molar ratio of the lower secondary amine to 1,3-propanesulfonic acid lactone is 0.8-1.4:

1.

8. The preparation method according to claim 7, wherein, The molar ratio of the lower secondary amine to 1,3-propanesulfonic acid lactone is 1-1.1:

1.

9. The preparation method according to claim 5, wherein, The first reaction temperature is 25-60℃; the first reaction time is 4-15h.

10. The preparation method according to claim 9, wherein, The first reaction temperature is 30-50℃; the first reaction time is 6-12h.

11. The preparation method according to claim 5, wherein, The molar ratio of the first intermediate to epichlorohydrin is 1.9-2.2:

1.

12. The preparation method according to claim 11, wherein, The molar ratio of the first intermediate to epichlorohydrin is 2-2.05:

1.

13. The preparation method according to claim 5, wherein, The second reaction temperature is 30-70℃; the second reaction time is 1.5-7h.

14. The preparation method according to claim 13, wherein, The second reaction temperature is 40-60℃; the second reaction time is 2-6h.

15. The preparation method according to claim 5, wherein, The molar ratio of the second intermediate to acryloyl chloride is 1:0.8-1.

2.

16. The preparation method according to claim 15, wherein, The molar ratio of the second intermediate to acryloyl chloride is 1:1-1.

1.

17. The preparation method according to claim 5, wherein, The third reaction temperature is 20-30℃; the third reaction time is 0.5-6h.

18. The preparation method according to claim 17, wherein, The third reaction temperature is 22-28℃; the third reaction time is 1-5h.

19. A polymerizable monomer obtained by the preparation method according to any one of claims 5-18.

20. A polymer thickener, characterized in that, The thickener comprises structural unit A and structural unit B; wherein structural unit A has the structure shown in formula (1), and structural unit B has the structure shown in formula (2). Equation (1), Equation (2) R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C6 straight-chain or branched alkyl groups.

21. The polymer thickener according to claim 20, wherein, The thickener further includes structural unit C and / or structural unit D, wherein structural unit C has the structure shown in formula (3) and structural unit D has the structure shown in formula (4). Equation (3), Equation (4), Among them, R7, R8, R 11 and R 12 Each is independently hydrogen or a C1-C4 straight-chain or branched alkyl group; R9 and R 10 Each is independently a C1-C6 straight-chain or branched alkyl group, either hydrogen- or hydroxyl-substituted or unsubstituted, and R9 and R 10 They are not both hydrogen.

22. The polymer thickener according to claim 20, wherein, R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C4 straight-chain or branched alkyl groups.

23. The polymer thickener according to claim 22, wherein, R1, R2, R3, R4, R5, and R6 are each independently hydrogen, methyl, or ethyl.

24. The polymer thickener according to claim 23, wherein, R1, R2, R3, and R4 are all methyl groups.

25. The polymer thickener according to claim 21, wherein, R7, R8, R 11 and R 12 Each can be independently hydrogen, methyl, or ethyl.

26. The polymer thickener according to claim 25, wherein, R7 and R8 are not both alkyl groups.

27. The polymer thickener according to claim 25, wherein, R 11 and R 12 They are not both alkyl groups.

28. The polymer thickener according to claim 21, wherein, R9 and R 10 Each is a C1-C4 straight-chain or branched alkyl group, which may be substituted with or unsubstituted with hydrogen or hydroxyl groups.

29. The polymer thickener according to claim 28, wherein, R9 and R 10 At least one of them is methyl.

30. The polymer thickener according to claim 29, wherein, R9 or R 10 It is hydroxyethyl.

31. The polymer thickener according to any one of claims 20-30, 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.

32. The polymer thickener according to claim 31, wherein, The molar ratio of structural unit A, structural unit B, structural unit C and structural unit D is 10-20:70:0-20:0-20.

33. The polymer thickener according to any one of claims 20-30, wherein, The viscosity-average molecular weight of the thickener is 100 × 10⁻⁶. 4 -800×10 4 g / mol.

34. The polymer thickener according to claim 33, wherein, The thickener has a viscosity-average molecular weight of 200 × 10⁻⁶. 4 -500×10 4 g / mol.

35. The polymer thickener according to any one of claims 20-30, wherein, A 30wt% CaCl2 salt aqueous solution containing 0.5wt% polymer thickener was subjected to an incubation period of 170 seconds at 100°C. -1 The apparent viscosity under shearing conditions of 90 min is not less than 35 mPa·s.

36. A method for preparing a polymer thickener, characterized in that, The preparation method includes: under polymerization reaction conditions and in the presence of an initiator, causing the monomers shown in formula (I) and formula (II) to undergo a polymerization reaction; Formula (I), Equation (II), R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C6 straight-chain or branched alkyl groups.

37. The preparation method according to claim 36, wherein, The monomers in the polymerization reaction also include the monomers shown in formula (III) and / or formula (IV). Equation (III), Formula (IV), Among them, R7, R8, R 11 and R 12 Each is independently hydrogen or a C1-C4 straight-chain or branched alkyl group; R9 and R 10 Each is independently a C1-C6 straight-chain or branched alkyl group, either hydrogen- or hydroxyl-substituted or unsubstituted, and R9 and R 10 They are not both hydrogen.

38. The preparation method according to claim 36, wherein, R1, R2, R3, R4, R5 and R6 are each independently hydrogen or C1-C4 straight-chain or branched alkyl groups.

39. The preparation method according to claim 38, wherein, R1, R2, R3, R4, R5, and R6 are each independently hydrogen, methyl, or ethyl.

40. The preparation method according to claim 39, wherein, R1, R2, R3, and R4 are all methyl groups.

41. The preparation method according to claim 37, wherein, R7, R8, R 11 and R 12 Each can be independently hydrogen, methyl, or ethyl.

42. The preparation method according to claim 41, wherein, R7 and R8 are not both alkyl groups.

43. The preparation method according to claim 41, wherein, R 11 and R 12 They are not both alkyl groups.

44. The preparation method according to claim 37, wherein, R9 and R 10 Each is a C1-C4 straight-chain or branched alkyl group, which may be substituted with or unsubstituted with hydrogen or hydroxyl groups.

45. The preparation method according to claim 44, wherein, R9 and R 10 At least one of them is methyl.

46. ​​The preparation method according to claim 45, wherein, R9 or R 10 It is hydroxyethyl.

47. The preparation method according to any one of claims 36-46, wherein, The polymerization reaction temperature is 30-60℃; the polymerization reaction time is 3-12h.

48. The preparation method according to claim 47, wherein, The polymerization reaction temperature is 40-50℃; the polymerization reaction time is 4-10h.

49. The preparation method according to any one of claims 36-46, wherein, The molar ratio of the monomers shown in formula (I), (II), (III), and (IV) is 5-25:60-80:0-25:0-25.

50. The preparation method according to claim 49, wherein, The molar ratio of the monomers shown in formula (I), (II), (III), and (IV) is 10-20:70:0-20:0-20.

51. The preparation method according to claim 36, wherein, The initiator is selected from at least one of ammonium persulfate, sodium bisulfite, azobisisobutylamidine hydrochloride, and azobisisobutylimidazoline hydrochloride.

52. The preparation method according to claim 51, wherein, The initiator is a complex of ammonium persulfate and sodium bisulfite.

53. The preparation method according to claim 52, wherein, The mass ratio of ammonium persulfate to sodium bisulfite in the complex of ammonium persulfate and sodium bisulfite is 0.5-2:

1.

54. The preparation method according to claim 53, wherein, In the complex of ammonium persulfate and sodium bisulfite, the mass ratio of ammonium persulfate to sodium bisulfite is 1-2:

1.

55. The preparation method according to claim 36 or 37, wherein, The amount of the initiator is 0.03-0.15 wt% of the total weight of the monomers shown in Formula (I), Formula (II), and Formula (III) and / or Formula (IV).

56. The preparation method according to claim 55, wherein, The amount of the initiator is 0.05-0.1 wt% of the total weight of the monomers shown in Formula (I), Formula (II), and Formula (III) and / or Formula (IV).

57. A polymer thickener obtained by the preparation method according to any one of claims 36-56.

58. A fracturing fluid, characterized in that, include: Water; inorganic salts; And the polymer thickener according to any one of claims 20-35 and 57.

59. The fracturing fluid according to claim 58, wherein, The water is deionized water.

60. The fracturing fluid according to claim 58, wherein, The inorganic salt is selected from at least one of sodium chloride, potassium chloride, calcium chloride, magnesium chloride, and potassium formate.

61. The fracturing fluid according to claim 58, wherein, The amount of inorganic salts used accounts for 10-50 wt% of the total mass of the fracturing fluid.

62. The fracturing fluid according to claim 61, wherein, The amount of inorganic salts used accounts for 20-30 wt% of the total mass of the fracturing fluid.

63. The fracturing fluid according to claim 58, wherein, The amount of the polymer thickener is 0.05-1 wt% of the total mass of the fracturing fluid.

64. The fracturing fluid according to claim 63, wherein, The amount of the polymer thickener is 0.3-0.8 wt% of the total mass of the fracturing fluid.

65. The application of the fracturing fluid of claim 58 in hydraulic fracturing.

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