Low-molecular salt-resistant thickening agent and preparation method thereof

Abstract

The application discloses a low-molecular anti-salt thickening agent and a preparation method thereof, and belongs to the technical field of oil and gas yield increase. The raw materials of the low-molecular anti-salt thickening agent disclosed by the application include acrylamide hydrophilic monomers, sodium acrylate hydrophilic monomers, salt-resistant monomers containing sulfonic acid groups, associated monomers containing amphiphilic groups, nano cross-linking agents with two-dimensional planar structures, composite initiators, molecular weight regulators and water; the mass ratio of the acrylamide hydrophilic monomers, the sodium acrylate hydrophilic monomers, the salt-resistant monomers containing sulfonic acid groups, the associated monomers containing amphiphilic groups and the nano cross-linking agents with two-dimensional planar structures is 1: (0.12-0.2): (0.025-0.2): (0.004-0.02): (0.002-0.004). The low-molecular anti-salt thickening agent disclosed by the application greatly improves the salt resistance and temperature resistance and shear resistance of the low-molecular anti-salt thickening agent.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas production enhancement technology, specifically relating to a low-molecular-weight salt-resistant thickener and its preparation method. Background Technology

[0002] With the continuous advancement and improvement of oil and gas exploration and development technologies and methods, a large number of unconventional oil and gas resources (tight gas, shale oil and gas, and coalbed methane, etc.) have been continuously discovered and have become an important replacement area for oil and gas development, making a significant contribution to global energy supply. Due to the tightness of unconventional oil and gas reservoirs and the difficulty in utilizing recoverable reserves, large-scale volumetric fracturing has become an essential path for the efficient development and production of unconventional oil and gas. During fracturing and production, large amounts of high-salinity flowback fluids and produced water are discharged from the well bottom or extracted to the surface in a surge. Flowback fluids and produced water generally have complex compositions, high salinity, high content of high-valence metal ions, high content of suspended solids, and high oil content. The technology for treating and discharging flowback fluids and produced water is extremely difficult and expensive. Under the current urgent need for cost reduction and efficiency improvement and stringent environmental protection requirements, this presents a huge challenge to oil and gas operators and workers. Therefore, the reuse of flowback fluid and produced water to prepare fracturing fluid has received continuous attention and has been regarded as one of the most economical and environmentally friendly technologies.

[0003] Fracturing fluid is an indispensable and widely used chemical working fluid in large-scale volumetric fracturing, playing a crucial role in fracturing, proppant transport, and placement. Its performance largely determines the efficiency of the fracturing operation and the final implementation effect. However, in the reuse of flowback fluid and produced water, high salinity (especially high-valence metal ions) significantly weakens the hydration and swelling capacity, solubility, and cross-linking properties of thickeners. Consequently, fracturing fluids formed using widely used guar gum and conventional polymers as thickeners cannot adequately meet the performance requirements under high salinity conditions, exhibiting problems such as insufficient thickening capacity, poor proppant carrying capacity, large dosage requirements, and high cost. To mitigate and avoid these problems, many methods have been proposed to reduce salinity and remove high-valence ions and other unfavorable components through different water treatment equipment and technologies or metal ion chelating agents, and these methods have been applied to a certain extent in oil and gas development sites. However, these technologies still suffer from long treatment cycles and additional investment in equipment and reagents, which can no longer meet the ever-increasing demand for cost reduction and efficiency improvement. Achieving direct utilization of flowback fluid and produced water without treatment has become an inevitable path. Therefore, developing a thickener with high salt resistance has become an indispensable technical means to solve the problems of high-salinity flowback fluid and direct utilization of produced water.

[0004] Chinese patent CN115947891B discloses a temperature- and salt-resistant, fast-dissolving polyacrylamide, its preparation method, and its applications. It obtains a narrow-distribution, low-molecular-weight modified polyacrylamide by introducing a benzene-ring-containing rigid, temperature- and salt-resistant monomer and a fluorine-containing cationic hydrophobic monomer, based on acrylamide monomer and sodium acrylate monomer. The molecular weight ranges from 3 million to 15 million Daltons. At a salinity of 100,000 mg / L (20,000 mg / L calcium and magnesium ions), the drag reduction rate of 0.03% powder reaches a maximum of 77.5%, and the viscosity of 0.2% powder at room temperature reaches a maximum of 27.75 mPa·s. This solves the problem of insufficient drag reduction performance of drag-reducing agents at low dosages. However, the patent does not mention the temperature resistance, shear strength, and debinding performance of the thickener at higher powder dosages. Chinese patent CN116285936B discloses a high-temperature resistant, salt-resistant, fast-dissolving fracturing fluid thickener and its preparation method. It modifies polyacrylamide by introducing a carboxylic acid-containing monomer, a salt-resistant monomer containing benzenesulfonic acid or benzoic acid groups, and a fluorinated cationic hydrophobic monomer into the polyacrylamide molecular structure. The modified polyacrylamide has a molecular weight between 4 million and 14 million Daltons. At a salinity of 120,000 mg / L (10,000 mg / L calcium and magnesium ions), the drag reduction rate of 0.03% powder reaches a maximum of 77.6%, and at room temperature, the viscosity of 0.2% powder reaches a maximum of 27.86 mPa·s. This also solves the problem of insufficient drag reduction performance of drag-reducing agents at low dosages. However, this patent also fails to mention the temperature resistance, shear strength, and gel breaking performance of the thickener at higher powder dosages. Chinese patent CN106190088B discloses a temperature-resistant and salt-resistant fast-dissolving thickener for seawater-based fracturing fluids and its preparation method. The thickener is prepared by copolymerization of acrylic acid, acrylamide, a separating monomer, a functional anionic monomer, a functional cationic monomer, and an associative intermediate. At a salinity of 45000 mg / L (calcium and magnesium ions 2720 mg / L) and room temperature, the viscosity of 0.5% thickener is greater than 80 mPa·s, and at 120°C and 170 s... -1At this temperature, the shear viscosity is approximately 45 mPa·s, but the patent does not mention the molecular weight range of the thickener, its gel breaking performance, or its salt resistance under higher salinity conditions. Chinese patent CN109265605B discloses a low-adsorption, salt-resistant drag-reducing agent suitable for fracturing in shale reservoirs. The drag-reducing agent is obtained through reverse emulsion polymerization of acrylamide and its derivatives, quaternary ammonium salt monomers, and low-adsorption cationic monomers. Under salinity conditions of 200,000 mg / L, 0.1% of the drag-reducing agent achieves a drag reduction rate of 67.84%. However, this patent does not mention its resistance to high-valence ions such as calcium and magnesium, or whether this drag-reducing agent can be used as a thickener and its related properties. Chinese patent CN106590614B discloses a fast-dissolving, salt-resistant, high-viscosity drag-reducing agent and its preparation method. The drag-reducing agent is obtained by reverse emulsion polymerization of salt-resistant monomers such as acrylamide and 2-acrylamide-2-methylpropanesulfonic acid with polymethacryloyloxyethyltrimethylammonium chloride. Under a mineralization of 30,000 mg / L, the drag reduction rate of 0.05% drag-reducing agent can reach more than 70%. However, the patent does not mention the ability to resist high-valence ions such as calcium and magnesium, or whether the drag-reducing agent can be used as a thickener and related properties. Chinese patent CN111732687B discloses a shear-resistant and salt-resistant fracturing fluid thickener. The thickener is obtained by polymerization initiated with acrylamide, acryloylglycine, acryloylglycine, or vinylguanidine as monomers and N,N'-methylenebisacrylamide as a crosslinking agent. The thickener can achieve good thickening ability and temperature and shear resistance at a salinity of 150,000 mg / L. However, the patent does not mention the ability to resist high-valence ions such as calcium and magnesium, or the gel breaking performance under corresponding conditions. Chinese Patent CN115636908B discloses a salt-resistant thickener for fracturing, its preparation method, and its application. The salt-resistant thickener is obtained by reverse emulsion polymerization of disodium maleate, acrylamide, 1-vinyl-3-ethylimidazolium bromide, 2-acrylamido-2-methylpropanesulfonic acid, and octadecyl acrylate in the presence of polydopamine-modified polyvinyl alcohol. A 1% thickener achieves an apparent viscosity of 204 mPa·s at room temperature and a salinity of 200,000 mg / L, and a viscosity of 170 s⁻¹ at room temperature. -1The viscosity retention rate after 4 hours of shearing is greater than 91%, but the patent does not mention its ability to resist high-valence ions such as calcium and magnesium, or its temperature resistance, shear resistance, and gel breaking performance at high temperatures. Furthermore, due to the introduction of the oil phase, low solid content, and large dosage, it poses a high risk of reservoir damage. Chinese patent CN118684820B discloses a low-molecular-weight powder salt-resistant drag-reducing agent, which is composed of a low-molecular-weight polymer formed by the polymerization of methacryloyl dopamine and diphenyl-1,3-butadiene in the presence of a polymerization initiator and under heating conditions, and an auxiliary agent formed by the polymerization of sodium 2-acrylamido-2-methylpropanesulfonate and sodium acrylate. Its molecular weight is preferably between 30,000 and 60,000 Daltons. It indicates that the drag-reducing agent can withstand salt concentrations up to 200,000 (calcium and magnesium ion content up to 20,000), but this patent does not provide specific data to support the dosage, viscosity, and drag reduction rate at high salt concentrations, nor does it mention whether the drag-reducing agent can be used as a thickener or its related properties.

[0005] Liu Tongyi et al. from Southwest Petroleum University prepared a fracturing fluid thickener by copolymerizing acrylamide, N-hydroxymethylacrylamide (NMA), and a hydrophobic cationic monomer. Under the conditions of 1% KCl and 100℃, 0.35wt% of the polymer was almost completely dissolved within 40 min, and the stable viscosity was greater than 53 mPa·s at 60 min (Liu Tongyi et al., Synthesis and Evaluation of an Aluminum Crosslinked Fracturing Fluid Thickener, Petrochemical Technology, 2018, 47(2)). Tang Tang from Southwest Petroleum University prepared a thickener for fracturing fluid with high suspension ratio and low damage by copolymerizing acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl dimethyl allyl ammonium chloride, and N,N-methylenebisacrylamide. Under the conditions of 1% KCl and 90℃, the viscosity of 0.4wt% of the polymer was greater than 57.44 mPa·s (Tang Tang, Research on a Fracturing Fluid with High Suspension Ratio and Low Damage, Southwest Petroleum University, 2018). Chen Hong et al. from Yangtze University synthesized an associative salt-resistant thickener using acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyl dimethylallyl ammonium chloride as comonomers. Under the condition of 2.0% mineralization, the 0.35wt% thickener solution still maintained a high viscosity (Chen Hong et al., Synthesis and performance of novel salt-resistant polymer fracturing fluid, Modern Chemical Industry, 2019, 48(3)). Liu Yameng et al. from Shaanxi University of Science and Technology prepared an associative salt-resistant polymer by reverse emulsion copolymerization of acrylamide, sodium 2-acrylamide-dodecyl sulfonate and hydrophobic monomer 29-(4-octylphenoxy)-3,6,9,12,15,18,21,24,27-nonoxyketone methacrylate. Under the condition of mixed aqueous solution of NaCl and CaCl2 with a mass concentration of 20000 mg / L, the apparent viscosity of 0.7% polymer solution was 64.8 mPa·s and 54.1 mPa·s, respectively (Liu Yameng et al., Preparation of associative salt-resistant polymer by reverse emulsion polymerization and its rheological properties, Fine Chemicals, 2024, 41(1)).

[0006] In summary, existing patents and published research mainly use the copolymerization of salt-resistant monomers and hydrophobic monomers to obtain associative salt-resistant thickeners. However, these thickeners generally suffer from problems such as high molecular weight, poor solubility under high salinity, poor thickening and temperature shear resistance, large dosage requirements, incomplete gel breaking, and high risk of reservoir damage, making them difficult to meet real-world needs. Summary of the Invention

[0007] The purpose of this invention is to provide a low-molecular-weight salt-resistant thickener and its preparation method, so as to solve the technical problem of high molecular weight of existing fracturing thickeners.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] This invention discloses a low-molecular-weight anti-salt thickener, the raw materials of which include: acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, anti-salt monomer containing sulfonic acid group, associative monomer containing amphiphilic group, nano crosslinking agent with two-dimensional planar structure, composite initiator, molecular weight regulator and water;

[0010] The mass ratio of the acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid groups, associative monomer containing amphiphilic groups, and nano-crosslinking agent with a two-dimensional planar structure is: 1: (0.12~0.2): (0.025~0.2): (0.004~0.02): (0.002~0.004).

[0011] The preparation method of the nano-crosslinking agent with a two-dimensional planar structure includes the following steps:

[0012] A nano-crosslinking agent with a two-dimensional planar structure was prepared using solid powder C, deionized water, metallic zirconium salt, and multifunctional compounds as reaction raw materials.

[0013] The structural formula of the solid powder C is as follows:

[0014] .

[0015] Furthermore, the salt-resistant monomer containing sulfonic acid groups is one or more of acrylamide short-chain alkyl sulfonic acid, acrylamide naphthalene sulfonate, acrylamide benzene sulfonate, ethylene benzene sulfonate, and ethylene naphthalene sulfonate;

[0016] The amphiphilic associating monomer is one or both of acrylamide long-chain alkyl sulfonate and long-chain alkyl unsaturated quaternary ammonium salt;

[0017] The alkyl carbon chain length in the acrylamide short-chain alkyl sulfonate is C3~C5;

[0018] The alkyl carbon chain length in the acrylamide long-chain alkyl sulfonate or long-chain alkyl unsaturated quaternary ammonium salt is C12~C20.

[0019] The low molecular weight salt-resistant thickener has a molecular weight of 3 million to 5 million Daltons; the dry powder particle size of the low molecular weight salt-resistant thickener is 80 to 120 mesh.

[0020] Furthermore, the specific steps for preparing the nano-crosslinking agent with a two-dimensional planar structure are as follows:

[0021] Solid powder C was ultrasonically dispersed in deionized water to obtain a dispersion. Zirconium salt was added to deionized water to obtain a zirconium salt solution. The zirconium salt solution and the dispersion were stirred and mixed for more than 5-10 minutes. Then, a multifunctional compound was added and the mixture was stirred for more than 5-10 minutes. The pH was adjusted to 7.5-8.5 with a pH adjuster. The mixture was then reacted at 55-65℃ for 4.5-5 hours to obtain a nano-crosslinking agent with a two-dimensional planar structure.

[0022] The multifunctional compound is a polyol or a polyacid.

[0023] Further, the mass ratio of the solid powder C, deionized water, zirconium salt, and polyfunctional compound is (0.8~0.9):(9~11):1:(1.3~1.6); the polyol is one or more of glycerol, 1,3-propanediol, sorbitol, and xylitol; the polyacid is one or more of lactic acid, citric acid, and phosphoric acid; and the pH adjuster is one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and sodium carbonate.

[0024] Furthermore, the method for preparing the solid powder C is as follows:

[0025] Solid powder A was prepared using molybdenum disulfide and hydrogen peroxide solution as reactants. The structural formula of solid powder A is as follows:

[0026] ;

[0027] Solid powder B was prepared by using solid powder A, ethanol aqueous solution, silane coupling agent and acetic acid as reaction raw materials. The structural formula of solid powder B is as follows:

[0028] ;

[0029] Solid powder C was prepared by using solid powder B, anhydrous N,N-dimethylformamide, succinic anhydride and triethylamine as reaction raw materials.

[0030] Furthermore, the specific preparation method of the solid powder C is as follows:

[0031] S1: Molybdenum disulfide was dispersed in hydrogen peroxide solution under ultrasonic conditions, followed by ultrasonic dispersion for 30-35 min, and then stirred in a water bath at 50-52℃ for 24-25 h or more to obtain a reaction solution; the reaction solution was centrifuged to obtain a precipitate, which was washed with deionized water until neutral, and then vacuum dried at 60-65℃ for 12-15 h or more to obtain solid powder A;

[0032] S2: Add solid powder A to an ethanol-water solution and ultrasonically disperse for 30-35 min. Then add silane coupling agent and acetic acid in sequence. Then reflux the reaction at 80-82℃ for more than 8-9 h to obtain a reaction solution. After centrifuging the reaction solution, obtain a precipitate. Wash the precipitate with anhydrous ethanol 3-4 times and vacuum dry it at 50-55℃ for more than 20-24 h to obtain solid powder B.

[0033] S3: Add solid powder B to N,N-dimethylformamide and disperse it by ultrasonication for 15-20 min. Then add succinic anhydride and triethylamine in sequence, and then reflux the reaction at 60-65℃ for more than 12-14 h to obtain a reaction solution. After centrifuging the reaction solution, a precipitate is obtained. The precipitate is washed three times with a mixture of N,N-dimethylformamide and anhydrous ethanol, and then vacuum dried at 60-65℃ for more than 12-15 h to obtain solid powder C.

[0034] Further, in S1, the mass concentration of the hydrogen peroxide solution is 30%~35%; the mass ratio of molybdenum disulfide to hydrogen peroxide solution is 1:(0.1~0.11).

[0035] In S2, the mass ratio of solid powder A, ethanol aqueous solution, silane coupling agent, and acetic acid is 1:(1.5~1.6):(0.02~0.025):(0.001~0.0012); the mass concentration of the ethanol aqueous solution is 95%~98%.

[0036] The silane coupling agent is one or more selected from γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane;

[0037] In S3, the mass ratio of the solid powder B, N,N-dimethylformamide, succinic anhydride, and triethylamine is 1:(0.8~0.9):2:(0.002~0.0025).

[0038] This invention also discloses a method for preparing the above-mentioned low-molecular-weight anti-salt thickener, comprising the following steps:

[0039] Weigh out the following components according to their mass ratio: acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, associative monomer containing amphiphilic group, and nano-crosslinking agent with two-dimensional planar structure for later use.

[0040] Acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group and associative monomer containing amphiphilic group are added to water in sequence to obtain a mixed solution;

[0041] The composite initiator and the molecular weight regulator were respectively prepared into a composite initiator solution and a molecular weight regulator solution;

[0042] A composite initiator solution, a molecular weight regulator solution, and a nano-crosslinking agent with a two-dimensional planar structure were simultaneously added dropwise to a mixed solution, followed by a reaction. After the reaction was completed, a colloidal product was obtained.

[0043] The colloidal product was post-processed to obtain a low-molecular-weight salt-resistant thickener.

[0044] Further, while stirring, acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group and associative monomer containing amphiphilic group are added to water in sequence to obtain a mixed solution; the pH value of the mixed solution is adjusted to 7.8~8.2;

[0045] In the mixed solution, the total mass concentration of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group and associative monomer containing amphiphilic group is 20%~30%.

[0046] Furthermore, the composite initiator solution is obtained by mixing a composite initiator and water; the molecular weight regulator solution is obtained by mixing a molecular weight regulator and water.

[0047] The mass concentration of the composite initiator solution is 5.0%~6.0%; the mass concentration of the molecular weight regulator solution is 2.0%~3.0%.

[0048] The composite initiator is a mixture of cerium ammonium nitrate, sodium bisulfite, and persulfate; the mass ratio of cerium ammonium nitrate, sodium bisulfite, and persulfate is (0.12~0.15):1:(1.2~1.25).

[0049] The molecular weight regulator is one or more of isopropanol, sodium formate, urea, dodecyl mercaptan, and n-butyl mercaptan.

[0050] Furthermore, the composite initiator solution, the molecular weight regulator solution, and the nano-crosslinking agent with a two-dimensional planar structure are simultaneously added dropwise to a mixed solution at a temperature of 15-18°C within 5-6 minutes;

[0051] The reaction is carried out in an adiabatic polymerization apparatus for 5-6 hours.

[0052] The amount of the composite initiator is 0.02% to 0.025% of the total mass of the acrylamide hydrophilic monomer, the sodium acrylate hydrophilic monomer, and the salt-resistant monomer containing sulfonic acid groups;

[0053] The amount of the molecular weight regulator is 0.015% to 0.016% of the total mass of the acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, and salt-resistant monomer containing sulfonic acid groups.

[0054] Furthermore, the post-processing includes sequential chopping, drying, and sieving.

[0055] The drying temperature is 105~110℃, and the drying time is 7~8 hours or more.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] This invention discloses a low-molecular-weight salt-resistant thickener. By innovatively setting the raw materials of the low-molecular-weight salt-resistant thickener, a nano-crosslinking agent with a two-dimensional planar structure is introduced into the polymerization reaction system. This enables the copolymerization reaction of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid groups, and associating monomer containing amphiphilic groups. The micro-crosslinking reaction of the resulting copolymer by the nano-crosslinking agent with a two-dimensional planar structure is carried out simultaneously. Due to the presence of the associating monomer containing amphiphilic groups, the molecular weight of the thickener is reduced and the micro-crosslinking effect of the nano-crosslinking agent with a two-dimensional planar structure is enhanced. The above material system can achieve micro-crosslinking and low molecular weight design, solving the technical problem of high molecular weight of existing fracturing thickeners.

[0058] Furthermore, the low-molecular-weight salt-resistant thickener disclosed in this invention utilizes the triple effect of "salt resistance of sulfonic acid groups in salt-resistant monomers containing sulfonic acid groups, association promotion of association groups in associative monomers containing amphiphilic groups, and micro-crosslinking structure enhancement of nano-crosslinking agents with two-dimensional planar structures" to synergistically and significantly improve the salt resistance and temperature and shear resistance of the low-molecular-weight salt-resistant thickener, reducing the amount of thickener required. At the same time, the low molecular weight of the low-molecular-weight salt-resistant thickener improves the solubility, shear resistance, and gel breaking performance under high salinity, simultaneously solving the problems of existing fracturing thickeners such as high molecular weight, poor solubility, thickening, and temperature and shear resistance under high salinity, large dosage, incomplete gel breaking, and high risk of reservoir damage.

[0059] Furthermore, according to relevant experimental results, when the molecular weight of the low-molecular-weight salt-resistant thickener of the present invention is ≤5 million Daltons, under the condition of 100,000 mg / L mineralization (calcium and magnesium ion content 5,000 mg / L), the tackifying time is less than 12s, the viscosity release rate is greater than 95% in 2 minutes, and the viscosity of the thickener with a mass concentration of 0.7% can reach 148 mPa·s at room temperature, and the viscosity can reach 170s at 120℃. -1 After 2 hours of downward shearing, the stable viscosity reaches 83 mPa·s, and the viscosity of the broken gel is less than 4.4 mm within 1.5 hours at 90℃ and 0.015% ammonium persulfate. 2 With a residue content of less than 30 mg / L, it exhibits excellent solubility at high mineralization with low molecular weight, high efficiency in thickening and temperature resistance and shear resistance at low dosage, as well as good debinding performance and low residue content.

[0060] Furthermore, the salt-resistant monomer containing sulfonic acid groups of the present invention is one or more of acrylamide short-chain alkyl sulfonic acid, acrylamide naphthalene sulfonate, acrylamide benzene sulfonate, ethylene benzene sulfonate, and ethylene naphthalene sulfonate, which has the advantage of being insensitive to salt and improving salt resistance.

[0061] Furthermore, the alkyl carbon chain length in the acrylamide short-chain alkyl sulfonic acid or acrylamide naphthalene sulfonate is C3~C5, which has the advantages of being insensitive to salt and rapidly dissolving in highly mineralized water.

[0062] Furthermore, the amphiphilic associating monomer of the present invention is one or more of acrylamide long-chain alkyl sulfonate and long-chain alkyl unsaturated quaternary ammonium salt, which has the advantage of generating a self-association effect and improving salt-resistant thickening performance.

[0063] Furthermore, the alkyl carbon chain length in the acrylamide long-chain alkyl sulfonate or long-chain alkyl unsaturated quaternary ammonium salt is C12~C20, which has the advantages of strong self-association thickening ability and rapid aggregation and thickening in water with high mineralization.

[0064] Furthermore, the molecular weight of the low-molecular-weight salt-resistant thickener is 3 million to 5 million Daltons; the dry powder particle size of the low-molecular-weight salt-resistant thickener is 80 to 120 mesh, which has the advantages of large contact surface area during hydration and swelling, high dissolution rate in high-mineralization water, less prone to fish-eye formation, fast adhesion, easy glue breaking, and low residue content.

[0065] Furthermore, the nano-crosslinking agent with a two-dimensional planar structure of the present invention can achieve micro-crosslinking of the thickener through the crosslinking effect of the two-dimensional planar structure and the carboxyl groups dissociated by the hydrophilic monomer of sodium acrylate. It has the advantages of high micro-crosslinking efficiency, strong micro-crosslinking ability, and significantly improved thickening performance in high-mineralization water at low molecular weight and low dosage.

[0066] This invention also discloses a method for preparing the above-mentioned nano-crosslinking agent with a two-dimensional planar structure. This method achieves the polyhydroxylation and carboxylation of nano-molybdenum disulfide through a stepwise reaction with sodium hydroxide, silane coupling agent, and succinic anhydride. Then, through its complexation reaction with zirconium salt and polyol or polyacid, it achieves efficient coordination complexation of zirconium ions with polyhydroxylated and carboxylated nano-molybdenum disulfide and polyol or polyacid. This method has the advantages of multiple crosslinking sites, high crosslinking efficiency, and high controllability.

[0067] This invention also discloses a method for preparing the aforementioned low-molecular-weight salt-resistant thickener. This method involves simultaneously performing a copolymerization reaction of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid groups, and associative monomer containing amphiphilic groups with a micro-crosslinking reaction of the resulting copolymer by a nano-crosslinking agent with a two-dimensional planar structure. This achieves the growth of the thickener's macromolecular chain and the structuring of the micro-crosslinking, and has the advantages of being able to prepare a low-molecular-weight thickener that is resistant to high salt concentrations and rapid dissolution, temperature and shear resistance, easy to break, and has low residue.

[0068] Furthermore, the total mass concentration of the acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, and associative monomer containing amphiphilic group in this invention is 20%~30%, which has the advantages of controllable degree of hydrolysis, which is conducive to ensuring good water solubility of thickener and preventing excessive complexation of high-valence metal ions under high mineralization to produce flocculants and precipitates.

[0069] Furthermore, the mass concentration of the composite initiator solution is 5.0%~6.0%, and the amount of the composite initiator is 0.02%~0.025% of the total mass of the acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, and salt-resistant monomer containing sulfonic acid groups, which has the advantages of controllable polymerization reaction and mild molecular chain growth.

[0070] Furthermore, the mass concentration of the molecular weight regulator solution is 2.0% to 3.0%, and the amount of the molecular weight regulator is 0.015% to 0.016% of the total mass of the acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, and salt-resistant monomer containing sulfonic acid groups, which has the advantages of moderate molecular weight adjustment and high adjustment efficiency of the thickener. Attached Figure Description

[0071] Figure 1 This is a comparison chart showing the temperature resistance and shear strength of the thickeners prepared in Example 18 and Comparative Example 7 of the present invention at a mass concentration of 0.7%.

[0072] Figure 2 This is a comparison chart showing the temperature resistance and shear strength of the thickeners prepared in Example 19 and Comparative Example 8 at a mass concentration of 0.7%.

[0073] Figure 3 This is a comparison chart showing the temperature resistance and shear strength of the thickeners prepared in Examples 29, 31, and Comparative Example 18 of the present invention at a mass concentration of 0.7%. Detailed Implementation

[0074] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0075] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0076] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0077] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0078] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0079] This invention provides a low molecular weight anti-salt thickener, the raw materials of which include: acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, anti-salt monomer containing sulfonic acid group, associative monomer containing amphiphilic group, nano crosslinking agent with two-dimensional planar structure, composite initiator, molecular weight regulator and water;

[0080] The mass ratio of the acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, associative monomer containing amphiphilic group, and nano-crosslinking agent with two-dimensional planar structure is 1: (0.12~0.2): (0.025~0.2): (0.004~0.02): (0.002~0.004).

[0081] Preferably, the salt-resistant monomer containing sulfonic acid groups is one or more selected from acrylamide short-chain alkyl sulfonic acid, acrylamide naphthalene sulfonate, acrylamide benzene sulfonate, ethylene benzene sulfonate, and ethylene naphthalene sulfonate;

[0082] The amphiphilic associating monomer is one or more of acrylamide long-chain alkyl sulfonate and long-chain alkyl unsaturated quaternary ammonium salt;

[0083] The alkyl carbon chain length in the acrylamide short-chain alkyl sulfonate is C3~C5;

[0084] The alkyl carbon chain length in the acrylamide long-chain alkyl sulfonate or long-chain alkyl unsaturated quaternary ammonium salt is C12~C20.

[0085] The low molecular weight salt-resistant thickener has a molecular weight of 3 million to 5 million Daltons; the dry powder particle size of the low molecular weight salt-resistant thickener is 80 to 120 mesh.

[0086] This invention also discloses a method for preparing the above-mentioned low-molecular-weight anti-salt thickener, comprising the following steps:

[0087] Step 1: Under stirring, add the required acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid groups, and associating monomer containing amphiphilic groups sequentially to deionized water. After stirring and dissolving evenly, add a pH adjuster to adjust the pH to 7.8-8.2 to obtain a mixed solution. The total mass concentration of the acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid groups, and associating monomer containing amphiphilic groups in the mixed solution is 20%-30%. The pH adjuster is one or more of glacial acetic acid, citric acid, sodium hydroxide, sodium bicarbonate, and potassium hydroxide.

[0088] Step 2: Mix the composite initiator with water to obtain a composite initiator solution; mix the molecular weight regulator with water to obtain a molecular weight regulator solution; wherein, the mass concentration of the composite initiator solution is 5.0%~6.0%; the mass concentration of the molecular weight regulator solution is 2%~3.0%; the composite initiator is a mixture of cerium ammonium nitrate, sodium bisulfite, and persulfate; the mass ratio of cerium ammonium nitrate, sodium bisulfite, and persulfate is (0.12~0.15):1:(1.2~1.25); the molecular weight regulator is one or more of isopropanol, sodium formate, urea, dodecyl mercaptan, and n-butyl mercaptan;

[0089] Step 3: Cool the mixed solution to 15-18℃, and simultaneously add the composite initiator solution, molecular weight regulator solution, and nano-crosslinking agent with a two-dimensional planar structure to the mixed solution dropwise over 5-6 minutes using a constant-speed peristaltic pump. Then, carry out the reaction in an adiabatic polymerization apparatus. After the reaction is complete, a colloidal product is obtained. The reaction time is 5-6 hours. The amount of composite initiator is 0.02%-0.025% of the total mass of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, and salt-resistant monomer containing sulfonic acid groups; the amount of molecular weight regulator is 0.015%-0.016% of the total mass of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, and salt-resistant monomer containing sulfonic acid groups.

[0090] Step 4: Post-process the colloidal product to obtain a low-molecular-weight salt-resistant thickener; the post-processing includes chopping, drying and sieving in sequence, the drying temperature is 105~110℃ and the drying time is 7~8 hours or more.

[0091] The preparation method of the nano-crosslinking agent with a two-dimensional planar structure used in this invention includes the following steps:

[0092] S1: Molybdenum disulfide was dispersed in hydrogen peroxide solution under ultrasonic conditions, followed by ultrasonic dispersion for 30-35 min, and then stirred in a water bath at 50-52℃ for 24-25 h or more to obtain a reaction solution; the reaction solution was centrifuged to obtain a precipitate, which was washed with deionized water until neutral, and then vacuum dried at 60-65℃ for 12-15 h or more to obtain solid powder A; wherein, the mass concentration of hydrogen peroxide solution was 30%-35%; the mass ratio of molybdenum disulfide to hydrogen peroxide solution was 1:(0.1-0.11);

[0093] The structural formula of the solid powder A is:

[0094] ;

[0095] S2: Solid powder A is added to an ethanol-water solution and ultrasonically dispersed for 30-35 min. Then, a silane coupling agent and acetic acid are added sequentially. Nitrogen gas is then introduced and the mixture is refluxed at 80-82°C for 8-9 h or more to obtain a reaction solution. After centrifugation, a precipitate is obtained. The precipitate is washed 3-4 times with anhydrous ethanol and vacuum dried at 50-55°C for 20-24 h or more to obtain solid powder B. The mass ratio of solid powder A, ethanol-water solution, silane coupling agent, and acetic acid is 1:(1.5-1.6):(0.02-0.025):(0.001-0.0012). The mass concentration of the ethanol-water solution is 95%-98%. The silane coupling agent is one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0096] The structural formula of solid powder B is:

[0097] ;

[0098] S3: Solid powder B is added to N,N-dimethylformamide and ultrasonically dispersed for 15-20 min. Then, succinic anhydride and triethylamine are added sequentially, followed by reflux at 60-65℃ for 12-14 h or more to obtain a reaction solution. After centrifugation, a precipitate is obtained. The precipitate is washed three times with a mixture of N,N-dimethylformamide and anhydrous ethanol, and then vacuum dried at 60-65℃ for 12-15 h or more to obtain solid powder C. The mass ratio of solid powder B, N,N-dimethylformamide, succinic anhydride, and triethylamine is 1:(0.8-0.9):2:(0.002-0.0025). The structural formula of solid powder C is:

[0099] ;

[0100] S4: Solid powder C is ultrasonically dispersed in deionized water to obtain a dispersion. Zirconium salt is added to deionized water to obtain a zirconium salt solution. The zirconium salt solution and the dispersion are stirred and mixed for 5-10 minutes or more. Then, a multifunctional compound is added and stirring is continued for 5-10 minutes or more. The pH value is adjusted to 7.5-8.5 with a pH adjuster. The mixture is then reacted at 55-65℃ for 4.5-5 hours to obtain a nano-crosslinking agent with a two-dimensional planar structure. The mass ratio of solid powder C, deionized water, zirconium salt, and multifunctional compound is (0.8-0.9):(9-11):1:(1.3-1.6). The polyol is one or more of glycerol, 1,3-propanediol, sorbitol, and xylitol. The polyacid is one or more of lactic acid, citric acid, and phosphoric acid. The pH adjuster is one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and sodium carbonate. The multifunctional compound is a polyol or a polyacid.

[0101] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0102] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0103] Example 1

[0104] A method for preparing a nano-crosslinking agent with a two-dimensional planar structure includes the following steps:

[0105] S1: Under ultrasonic conditions, 100g of molybdenum disulfide was dispersed in 10.5g of a 30% hydrogen peroxide solution. After ultrasonic dispersion for 30min, the solution was stirred in a water bath at 50℃ for 24h to obtain a reaction solution. The reaction solution was centrifuged at 5000r / min for 15min to obtain a precipitate. The precipitate was washed with deionized water until neutral and then vacuum dried at 60℃ for 12h to obtain hydroxylated molybdenum disulfide powder (solid powder A). The structural formula of the hydroxylated molybdenum disulfide powder is:

[0106] ;

[0107] S2: 100g of hydroxylated molybdenum disulfide powder was added to 150g of a 95% ethanol aqueous solution and ultrasonically dispersed for 30min. Then, 2g of γ-aminopropyltriethoxysilane and 0.1g of acetic acid were added sequentially. Nitrogen gas was then introduced and the mixture was refluxed at 80℃ for 8h to obtain a reaction solution. The reaction solution was centrifuged at 5000r / min for 15min using a high-speed centrifuge to obtain a precipitate. The precipitate was washed three times with anhydrous ethanol and vacuum dried at 50℃ for 20h to obtain γ-aminopropyltriethoxysilane-modified molybdenum disulfide powder (solid powder B). The structural formula of the γ-aminopropyltriethoxysilane-modified molybdenum disulfide powder is:

[0108] ;

[0109] S3: 100g of γ-aminopropyltriethoxysilane-modified molybdenum disulfide powder was added to 80g of N,N-dimethylformamide and ultrasonically dispersed for 15min. Then, 200g of succinic anhydride and 0.2g of triethylamine were added sequentially, followed by reflux at 60℃ for 12h under nitrogen to obtain a reaction solution. The reaction solution was centrifuged at 5000r / min for 15min using a high-speed centrifuge to obtain a precipitate. The precipitate was washed three times with a mixture of N,N-dimethylformamide and anhydrous ethanol (volume ratio 1:1) and vacuum dried at 60℃ for 12h to obtain hydroxylated and carboxylated molybdenum disulfide powder (solid powder C). The structural formula of the hydroxylated and carboxylated molybdenum disulfide powder is:

[0110] ;

[0111] S4: 3.9g of hydroxylated and carboxylated molybdenum disulfide powder was ultrasonically dispersed in 40g of deionized water to obtain a dispersion. 4.8g of zirconium oxychloride was added to 5g of deionized water to obtain a zirconium salt solution. The zirconium salt solution and the dispersion were stirred and mixed for more than 5min. Then, 6.3g of lactic acid was added and stirred for more than 5min to mix evenly. The pH value was adjusted to 8.0 with sodium hydroxide. Then, the reaction was carried out at 55℃ for 4.5h to obtain a nano-crosslinking agent with a two-dimensional planar structure, denoted as NJL-1.

[0112] Example 2

[0113] The difference between this embodiment and Example 1 is that the silane coupling agent γ-aminopropyltriethoxysilane in Example 1 is replaced with N-β-(aminoethyl)-γ-aminopropylmethyltrimethoxysilane. The remaining preparation process and parameters are the same as in Example 1, resulting in a nano-crosslinking agent with a two-dimensional planar structure, denoted as NJL-2. The structural formula of the prepared solid powder B is:

[0114] ;

[0115] The structural formula of the prepared solid powder C is:

[0116] .

[0117] Example 3

[0118] The difference between this embodiment and Example 1 is that the silane coupling agent γ-aminopropyltriethoxysilane in Example 1 is replaced with N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane. The remaining preparation process and parameters are the same as in Example 1, resulting in a nano-crosslinking agent with a two-dimensional planar structure, denoted as NJL-3. The structural formula of the prepared solid powder B is:

[0119] ;

[0120] The structural formula of the prepared solid powder C is:

[0121] .

[0122] Example 4

[0123] Step 1: While stirring, in a 1000mL beaker, add 217.2g of acrylamide hydrophilic monomer, 26.06g of sodium acrylate hydrophilic monomer, 5.43g of 2-acrylamido-2-methylpropanesulfonic acid, and 0.87g of sodium 2-acrylamidotetradecyl sulfonate to 747.13g of water sequentially. After stirring until dissolved, add sodium hydroxide to adjust the pH to 8.0 to obtain a mixed solution. The total mass concentration of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, and sodium 2-acrylamidotetradecyl sulfonate in the mixed solution is 25%. The mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, and sodium 2-acrylamidotetradecyl sulfonate is 1:0.12:0.025:0.004.

[0124] Step 2: Mix 5g of composite initiator (a mixture of cerium ammonium nitrate, sodium bisulfite and ammonium persulfate in a mass ratio of 0.12:1:1.2) and 2g of sodium formate with water to obtain composite initiator solution and molecular weight regulator solution with mass concentrations of 5.0% and 2%, respectively.

[0125] Step 3: Cool the mixed solution from Step 1 to 15°C. Simultaneously add 1g of composite initiator solution, 1.88g of molecular weight regulator solution, and 0.43g of NJL-1 to the mixed solution over 5 minutes using a constant-speed peristaltic pump. Then, react in an adiabatic polymerization apparatus for 5 hours. After the reaction is complete, a colloidal product is obtained. The mass ratio of NJL-1 to the hydrophilic acrylamide monomer in Step 1 is 0.002:1.

[0126] Step 4: Chop the colloidal product, dry it at 105℃ for 7 hours, then pulverize it through a high-power pulverizer and pass it through an 80-120 mesh stainless steel sieve to obtain a low molecular weight salt-resistant thickener with a dry powder particle size of 80-120 mesh, denoted as LMKY-1.

[0127] The viscosity-average molecular weight of LMKY-1 obtained in Example 4 was determined to be 4.76 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0128] Example 5

[0129] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.2:0.025:0.004:0.002, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-2.

[0130] The viscosity-average molecular weight of LMKY-2 obtained in Example 5 was determined to be 4.46 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0131] Example 6

[0132] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.12:0.2:0.004:0.002, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-3.

[0133] The viscosity-average molecular weight of LMKY-3 obtained in Example 6 was determined to be 4.28 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0134] Example 7

[0135] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.2:0.2:0.004:0.002, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-4.

[0136] The viscosity-average molecular weight of LMKY-4 obtained in Example 7 was determined to be 3.85 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0137] Example 8

[0138] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.12:0.025:0.02:0.002, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-5.

[0139] The viscosity-average molecular weight of LMKY-5 obtained in Example 8 was determined to be 4.16 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0140] Example 9

[0141] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.2:0.025:0.02:0.002, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-6.

[0142] The viscosity-average molecular weight of LMKY-6 obtained in Example 9 was determined to be 3.81 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0143] Example 10

[0144] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.12:0.2:0.02:0.002, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-7.

[0145] The viscosity-average molecular weight of LMKY-7 obtained in Example 10 was determined to be 3.55 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0146] Example 11

[0147] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.2:0.2:0.02:0.002, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-8.

[0148] The viscosity-average molecular weight of LMKY-8 obtained in Example 11 was determined to be 3 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0149] Example 12

[0150] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.12:0.025:0.004:0.004, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-9.

[0151] The viscosity-average molecular weight of LMKY-9 obtained in Example 12 was determined to be 5 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0152] Example 13

[0153] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.2:0.025:0.004:0.004, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-10.

[0154] The viscosity-average molecular weight of LMKY-10 obtained in Example 13 was determined to be 4.78 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0155] Example 14

[0156] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.12:0.2:0.004:0.004, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-11.

[0157] The viscosity-average molecular weight of LMKY-11 obtained in Example 14 was determined to be 4.51 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0158] Example 15

[0159] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.2:0.2:0.004:0.004, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-12.

[0160] The viscosity-average molecular weight of LMKY-12 obtained in Example 15 was determined to be 4.13 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0161] Example 16

[0162] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.12:0.025:0.02:0.004, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-13.

[0163] The viscosity-average molecular weight of LMKY-13 obtained in Example 16 was determined to be 4.33 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0164] Example 17

[0165] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.2:0.025:0.02:0.004, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-14.

[0166] The viscosity-average molecular weight of LMKY-14 obtained in Example 17 was determined to be 4.01 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0167] Example 18

[0168] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.12:0.2:0.02:0.004, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-15.

[0169] The viscosity-average molecular weight of LMKY-15 obtained in Example 18 was determined to be 3.92 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0170] Example 19

[0171] The difference from Example 4 is that the mass ratio of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamidotetradecyl sulfonate and NJL-1 is changed to 1:0.2:0.2:0.02:0.004, resulting in a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-16.

[0172] The viscosity-average molecular weight of LMKY-16 obtained in Example 19 was determined to be 3.67 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0173] Example 20

[0174] The difference from Example 4 is that 2-acrylamido-2-methylpropanesulfonic acid is replaced with sodium 5-acrylamidonaphthalenesulfonate, resulting in a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80-120 mesh, denoted as LMKY-17.

[0175] The viscosity-average molecular weight of LMKY-17 obtained in Example 20 was determined to be 4.23 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0176] Example 21

[0177] The difference from Example 19 is that 2-acrylamido-2-methylpropanesulfonic acid is replaced with sodium 5-acrylamidonaphthalenesulfonate to obtain a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-18.

[0178] The viscosity-average molecular weight of LMKY-16 obtained in Example 21 was determined to be 3.15 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0179] Example 22

[0180] The difference from Example 4 is that 2-acrylamido-2-methylpropanesulfonic acid is replaced with sodium p-acrylamidobenzenesulfonate to obtain a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-19.

[0181] The viscosity-average molecular weight of LMKY-19 obtained in Example 22 was determined to be 4.36 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0182] Example 23

[0183] The difference from Example 19 is that 2-acrylamido-2-methylpropanesulfonic acid is replaced with sodium p-acrylamidobenzenesulfonate to obtain a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80-120 mesh, denoted as LMKY-20.

[0184] The viscosity-average molecular weight of LMKY-20 obtained in Example 23 was determined to be 3.32 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0185] Example 24

[0186] The difference from Example 4 is that 2-acrylamido-2-methylpropanesulfonic acid is replaced with sodium p-ethylenebenzenesulfonate to obtain a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80-120 mesh, denoted as LMKY-21.

[0187] The viscosity-average molecular weight of LMKY-21 obtained in Example 24 was determined to be 4.48 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0188] Example 25

[0189] The difference from Example 19 is that 2-acrylamido-2-methylpropanesulfonic acid is replaced with sodium p-ethylenebenzenesulfonate to obtain a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80-120 mesh, denoted as LMKY-22.

[0190] The viscosity-average molecular weight of LMKY-22 obtained in Example 25 was determined to be 3.54 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0191] Example 26

[0192] The difference from Example 4 is that 2-acrylamido-2-methylpropanesulfonic acid is replaced with sodium 5-vinylnaphthalenesulfonate to obtain a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-23.

[0193] The viscosity-average molecular weight of LMKY-23 obtained in Example 26 was determined to be 4.31 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0194] Example 27

[0195] The difference from Example 19 is that 2-acrylamido-2-methylpropanesulfonic acid is replaced with sodium 5-vinylnaphthalenesulfonate to obtain a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80-120 mesh, denoted as LMKY-24.

[0196] The viscosity-average molecular weight of LMKY-24 obtained in Example 27 was determined to be 3.46 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0197] Example 28

[0198] The difference from Example 4 is that 2-acrylamidotetradecylsulfonic acid is replaced with hexadecyldimethylallylammonium chloride, resulting in a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80-120 mesh, denoted as LMKY-25.

[0199] The viscosity-average molecular weight of LMKY-25 obtained in Example 28 was determined to be 4.95 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0200] Example 29

[0201] The difference from Example 19 is that 2-acrylamidotetradecylsulfonic acid is replaced with hexadecyldimethylallylammonium chloride, resulting in a low-molecular-weight salt-resistant thickener with a dry powder particle size of 80-120 mesh, denoted as LMKY-26.

[0202] The viscosity-average molecular weight of LMKY-26 obtained in Example 29 was determined to be 3.87 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0203] Example 30

[0204] The difference from Example 4 is that NJL-1 is replaced with NJL-2 to obtain a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-27.

[0205] The viscosity-average molecular weight of LMKY-27 obtained in Example 30 was determined to be 4.68 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0206] Example 31

[0207] The difference from Example 19 is that NJL-1 is replaced with NJL-2 to obtain a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-28.

[0208] The viscosity-average molecular weight of LMKY-28 obtained in Example 31 was determined to be 3.59 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0209] Example 32

[0210] The difference from Example 4 is that NJL-1 is replaced with NJL-3 to obtain a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-29.

[0211] The viscosity-average molecular weight of LMKY-29 obtained in Example 32 was determined to be 4.75 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0212] Example 33

[0213] The difference from Example 19 is that NJL-1 is replaced with NJL-3 to obtain a low molecular weight salt-resistant thickener with a dry powder particle size of 80~120 mesh, denoted as LMKY-30.

[0214] The viscosity-average molecular weight of LMKY-30 obtained in Example 33 was determined to be 3.64 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0215] Comparative Example 1

[0216] The difference from Example 4 is that NJL-1 was not added, resulting in thickener DB-1 with a dry powder particle size of 80~120 mesh.

[0217] The viscosity-average molecular weight of the thickener DB-1 obtained in Comparative Example 1 was determined to be 4.05 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0218] Comparative Example 2

[0219] The difference from Example 5 is that NJL-1 was not added, resulting in thickener DB-2 with a dry powder particle size of 80~120 mesh.

[0220] The viscosity-average molecular weight of the thickener DB-2 obtained in Comparative Example 2 was determined to be 3.75 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0221] Comparative Example 3

[0222] The difference from Example 6 is that NJL-1 was not added, resulting in thickener DB-3 with a dry powder particle size of 80~120 mesh.

[0223] The viscosity-average molecular weight of the thickener DB-3 obtained in Comparative Example 3 was determined to be 3.42 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0224] Comparative Example 4

[0225] The difference from Example 7 is that NJL-1 was not added, resulting in thickener DB-4 with a dry powder particle size of 80~120 mesh.

[0226] The viscosity-average molecular weight of the thickener DB-4 obtained in Comparative Example 4 was determined to be 3.12 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0227] Comparative Example 5

[0228] The difference from Example 8 is that NJL-1 was not added, resulting in thickener DB-5 with a dry powder particle size of 80~120 mesh.

[0229] The viscosity-average molecular weight of the thickener DB-5 obtained in Comparative Example 5 was determined to be 3.35 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0230] Comparative Example 6

[0231] The difference from Example 9 is that NJL-1 was not added, resulting in thickener DB-6 with a dry powder particle size of 80~120 mesh.

[0232] The viscosity-average molecular weight of the thickener DB-6 obtained in Comparative Example 6 was determined to be 2.98 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0233] Comparative Example 7

[0234] The difference from Example 10 is that NJL-1 was not added, resulting in thickener DB-7 with a dry powder particle size of 80~120 mesh.

[0235] The viscosity-average molecular weight of the thickener DB-7 obtained in Comparative Example 7 was determined to be 2.55 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0236] Comparative Example 8

[0237] The difference from Example 11 is that NJL-1 was not added, resulting in thickener DB-8 with a dry powder particle size of 80~120 mesh.

[0238] The viscosity-average molecular weight of the thickener DB-8 obtained in Comparative Example 8 was determined to be 2.22 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0239] Comparative Example 9

[0240] The difference from Example 20 is that NJL-1 was not added, resulting in thickener DB-9 with a dry powder particle size of 80~120 mesh.

[0241] The viscosity-average molecular weight of the thickener DB-9 obtained in Comparative Example 9 was determined to be 3.75 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0242] Comparative Example 10

[0243] The difference from Example 21 is that NJL-1 was not added, resulting in thickener DB-10 with a dry powder particle size of 80~120 mesh.

[0244] The viscosity-average molecular weight of the thickener DB-10 obtained in Comparative Example 10 was determined to be 2.08 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0245] Comparative Example 11

[0246] The difference from Example 22 is that NJL-1 was not added, resulting in thickener DB-11 with a dry powder particle size of 80~120 mesh.

[0247] The viscosity-average molecular weight of the thickener DB-11 obtained in Comparative Example 11 was determined to be 3.85 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0248] Comparative Example 12

[0249] The difference from Example 23 is that NJL-1 was not added, resulting in a thickener DB-12 with a dry powder particle size of 80~120 mesh.

[0250] The viscosity-average molecular weight of the thickener DB-12 obtained in Comparative Example 12 was determined to be 2.13 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0251] Comparative Example 13

[0252] The difference from Example 24 is that NJL-1 was not added, resulting in thickener DB-13 with a dry powder particle size of 80~120 mesh.

[0253] The viscosity-average molecular weight of the thickener DB-13 obtained in Comparative Example 13 was determined to be 3.96 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0254] Comparative Example 14

[0255] The difference from Example 25 is that NJL-1 was not added, resulting in thickener DB-14 with a dry powder particle size of 80~120 mesh.

[0256] The viscosity-average molecular weight of the thickener DB-14 obtained in Comparative Example 14 was determined to be 2.24 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0257] Comparative Example 15

[0258] The difference from Example 26 is that NJL-1 was not added, resulting in thickener DB-15 with a dry powder particle size of 80~120 mesh.

[0259] The viscosity-average molecular weight of the thickener DB-15 obtained in Comparative Example 15 was determined to be 3.89 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0260] Comparative Example 16

[0261] The difference from Example 27 is that NJL-1 was not added, resulting in thickener DB-16 with a dry powder particle size of 80~120 mesh.

[0262] The viscosity-average molecular weight of the thickener DB-16 obtained in Comparative Example 16 was determined to be 1.98 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0263] Comparative Example 17

[0264] The difference from Example 28 is that NJL-1 was not added, resulting in thickener DB-17 with a dry powder particle size of 80~120 mesh.

[0265] The viscosity-average molecular weight of the thickener DB-17 obtained in Comparative Example 17 was determined to be 3.98 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0266] Comparative Example 18

[0267] The difference from Example 29 is that NJL-1 was not added, resulting in thickener DB-18 with a dry powder particle size of 80~120 mesh.

[0268] The viscosity-average molecular weight of the thickener DB-18 obtained in Comparative Example 18 was determined to be 2.1 million Daltons using an Ubbelohde viscometer (0.55 mm capillary inner diameter) according to the standard GB / T 12005.10-1992 Determination of Molecular Weight of Polyacrylamide.

[0269] The thickener performance testing method involved in this invention is as follows:

[0270] (1) Adhesion time

[0271] Accurately weigh the calculated amount of thickener powder into a 500mL beaker pre-filled with an appropriate amount of brine (total mineralization 100000mg / L, of which calcium and magnesium ion content is 5000mg / L). Dissolve the powder by stirring with a high-powered stirrer at a speed of 600±50rad / min at room temperature. The time corresponding to when the powder forms a string when lifted with a glass rod is the viscous time.

[0272] (2) Viscosity and viscosity release rate

[0273] Prepare a thickener salt solution of the target mass concentration according to the method in (1), and use a six-speed rotational viscometer at 100 r / min (170 s) at room temperature. -1 The viscosity values ​​were tested at different dissolution times, and the viscosity release rate was calculated using the following formula. When the viscosity was below 10 mPa·s, a capillary viscometer was used to test the kinematic viscosity of the product.

[0274] ;

[0275] In the formula, V R The viscosity before stabilization is in mPa·s; V F The final stable viscosity is measured in mPa·s. R V The viscosity release rate is expressed as %.

[0276] (3) Temperature resistance and shear resistance

[0277] Using the RS6000 advanced rheometer PZ38 coaxial cylindrical rotor system at 120℃ for 170s-1 The obtained thickener salt solution was subjected to a temperature resistance and shear resistance test. The viscosity change curve over time and the final stable viscosity value were recorded. The duration from heating to the end of the test was 2 hours.

[0278] (4) Debonding performance

[0279] Weigh 100g of thickener brine solution and put it into a metal sealed container. Add ammonium persulfate with a mass concentration of 0.015%. After sealing and aging at 90℃ for different times, take it out and test the viscosity and residue content of the fracturing fluid at room temperature according to the industry standard SY / T 5107-2016 "Performance Evaluation Method of Water-based Fracturing Fluid".

[0280] The thickeners obtained in Examples 4 to 33 and Comparative Examples 1 to 18 were tested at different dosages using the above method at a mineralization of 100,000 mg / L (calcium and magnesium ion content of 5,000 mg / L). The results are listed in Table 1.

[0281] Table 1. Test results of thickener's tack time, viscosity at 2 min, and viscosity release rate.

[0282]

[0283] As shown in Table 1, the thickeners (LMKY-1~30) obtained by introducing a nano-crosslinking agent with a two-dimensional planar structure to achieve micro-crosslinking in Examples 4~33 all had a tack time of less than 12s at thickener additions of 0.15wt% and 0.7wt%, and a viscosity release rate of more than 95% at 2min. More surprisingly, the 2min viscosity of thickeners LMKY-1~33 at 0.15wt% and 0.7wt% additions was at least 2.9 mPa·s and 20 mPa·s higher than the viscosity of the thickeners (DB-1~18) obtained in Comparative Examples 1~18 without the introduction of a nano-crosslinking agent with a two-dimensional planar structure, respectively. In particular, at a dosage of 0.7 wt%, the viscosity of the thickener (LMKY-15) obtained in Example 18 was 43 mPa·s higher than that of the thickener (DB-7) obtained in Comparative Example 7; the viscosity of the thickener (LMKY-16) obtained in Example 19 was 52 mPa·s higher than that of Comparative Example 8 (DB-8); the viscosity of the thickener (LMKY-26) obtained in Example 29 was 51 mPa·s higher than that of Comparative Example 18 (DB-18); and the viscosity of the thickener (LMKY-28) obtained in Example 31 was 63 mPa·s higher than that of Comparative Example 18 (DB-18). This indicates that introducing a nano-crosslinking agent with a two-dimensional planar structure into the thickener molecular structure can significantly improve the thickening ability of the obtained thickener at high salinity with low molecular weight, achieving excellent solubility and high salt resistance at high salinity.

[0284] The thickeners obtained in Examples 4 to 33 and Comparative Examples 1 to 18 were tested at a mineralization of 100,000 mg / L (calcium and magnesium ion content of 5,000 mg / L) and 120°C at a mass concentration of 0.7%. The results are listed in Table 2.

[0285] Table 2. Test results of the temperature resistance and shear strength of the thickener.

[0286]

[0287] As shown in Table 2, the thickeners (LMKY-1~30) obtained by introducing a nano-crosslinking agent with a two-dimensional planar structure in Examples 4~33 to achieve micro-crosslinking, with a thickener addition of 0.7wt%, have a temperature-resistant shear-resistant viscosity that is at least 15 mPa·s higher than that of the thickeners (DB-1~18) obtained in Comparative Examples 1~18 without introducing a nano-crosslinking agent with a two-dimensional planar structure. More significantly, the temperature-resistant shear-stable viscosity of the thickener (LMKY-15) obtained in Example 18 is 27 mPa·s higher than that of the thickener (DB-7) obtained in Comparative Example 7; the temperature-resistant shear-stable viscosity of the thickener (LMKY-16) obtained in Example 19 is 33 mPa·s higher than that of Comparative Example 8 (DB-8); the temperature-resistant shear-stable viscosity of the thickener (LMKY-26) obtained in Example 29 is 33 mPa·s higher than that of Comparative Example 18 (DB-18); and the temperature-resistant shear-stable viscosity of the thickener (LMKY-28) obtained in Example 31 is 37 mPa·s higher than that of Comparative Example 18 (DB-18). This indicates that introducing a nano-crosslinking agent with a two-dimensional planar structure into the thickener molecular structure can significantly improve the temperature-resistant shear-stable performance of the obtained thickener at high salinity through the strengthening effect of the micro-crosslinking structure at low molecular weight.

[0288] The thickeners obtained in Examples 4 to 33 and the thickeners obtained in Comparative Examples 1 to 18 were tested at a mineralization of 100,000 mg / L (calcium and magnesium ion content of 5,000 mg / L) and 90°C with a mass concentration of 0.7% and an ammonium persulfate content of 0.015%. The results are listed in Table 3.

[0289] Table 3. Test results of the thickener's gel breaking performance.

[0290]

[0291] As shown in Table 3, the thickeners (LMKY-1~30) obtained by introducing a nano-crosslinking agent with a two-dimensional planar structure in Examples 4~33 to achieve micro-crosslinking exhibited comparable debriding performance to the thickeners (DB-1~18) obtained in Comparative Examples 1~18 without introducing a nano-crosslinking agent with a two-dimensional planar structure. All thickeners could be completely debrided within 1.5 hours at 90°C and with 0.015% ammonium persulfate, and the viscosity of the debrided solution was less than 4.4 mm. 2 The concentrations of both the solids and residues are less than 30 mg / L. This indicates that introducing a micro-crosslinked structure into the thickener based on a low molecular weight design did not significantly affect the thickener's debonding performance. The thickener still possesses excellent debonding ability and very low residue content, resulting in a low risk of reservoir damage.

[0292] The above data results indicate that by introducing a nano-crosslinking agent with a two-dimensional planar structure into the fracturing thickener, achieving micro-crosslinking and low molecular weight design, the resulting low molecular weight salt-resistant thickener can not only improve the solubility and debriding performance of the thickener at a lower molecular weight, but also significantly improve the high salt resistance performance at a lower dosage, achieving excellent thickening performance and temperature resistance and shear resistance under high salinity water conditions.

[0293] In summary, this invention introduces a nano-crosslinking agent with a two-dimensional planar structure into the fracturing thickener, achieving micro-crosslinking and low molecular weight design. Through the synergistic effect of "sulfonic acid group salt resistance + associative group association promotion + micro-crosslinking structure strengthening," its high-salt resistance is significantly improved. Simultaneously, the low molecular weight characteristic significantly enhances its solubility and breaking performance at high salinity. This addresses the problems of existing fracturing thickeners, such as high molecular weight, poor solubility, thickening, and temperature and shear resistance at high salinity, large dosage, incomplete breaking, and high risk of reservoir damage. With a molecular weight ≤ 5 million Daltons and a salinity of 100,000 mg / L (calcium and magnesium ion content 5000 mg / L), the thickener achieves a viscosity release time of less than 12 seconds and a viscosity release rate of greater than 95% in 2 minutes. A 0.7% concentration thickener can reach a viscosity of 148 mPa•s at room temperature and 120℃ in 170 seconds. -1 After 2 hours of downward shearing, the stable viscosity reaches 83 mPa•s, and the viscosity of the broken gel is less than 4.4 mm within 1.5 hours at 90℃ and 0.015% ammonium persulfate. 2 / s, residue content less than 30mg / L.

[0294] Figure 1 The figure shows a comparison of the temperature and shear resistance of the thickeners prepared in Example 18 and Comparative Example 7 of this invention at a mass concentration of 0.7%. As can be seen from the figure, the temperature and shear resistance stable viscosity of the low molecular weight salt-resistant thickener (LMKY-15) prepared by introducing a nano-crosslinking agent with a two-dimensional planar structure is 27 mPa·s higher than that of the thickener (DB-7) prepared without introducing a nano-crosslinking agent with a two-dimensional planar structure. This demonstrates high salt resistance and excellent temperature and shear resistance under low molecular weight and low dosage.

[0295] Figure 2The figure shows a comparison of the temperature and shear resistance of the thickeners prepared in Example 19 and Comparative Example 8 at a mass concentration of 0.7%. As can be seen from the figure, the temperature and shear resistance stable viscosity of the low molecular weight salt-resistant thickener (LMKY-16) prepared by introducing a nano-crosslinking agent with a two-dimensional planar structure is 33 mPa·s higher than that of the thickener (DB-8) prepared without introducing a nano-crosslinking agent with a two-dimensional planar structure. This shows that the thickener has high salt resistance and excellent temperature and shear resistance under low molecular weight and low dosage.

[0296] Figure 3 The figure shows a comparison of the temperature and shear resistance of the thickeners prepared in Examples 29, 31 and Comparative Example 18 of this invention at a mass concentration of 0.7%. As can be seen from the figure, the temperature and shear resistance stable viscosity of the low molecular weight salt-resistant thickeners (LMKY-26 and LMKY-28) prepared by introducing nano-crosslinking agents with two-dimensional planar structures is 33 mPa·s and 37 mPa·s higher, respectively, than that of the thickener (DB-18) prepared without introducing nano-crosslinking agents with two-dimensional planar structures. This demonstrates high salt resistance and excellent temperature and shear resistance under low molecular weight and low dosage.

[0297] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A low-molecular-weight salt-resistant thickener, characterized in that, The raw materials of the low molecular weight salt-resistant thickener include: acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, associative monomer containing amphiphilic group, nano crosslinking agent with two-dimensional planar structure, composite initiator, molecular weight regulator and water; The mass ratio of the acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid groups, associative monomer containing amphiphilic groups, and nano-crosslinking agent with a two-dimensional planar structure is: 1: (0.12~0.2): (0.025~0.2): (0.004~0.02): (0.002~0.004). The preparation method of the nano-crosslinking agent with a two-dimensional planar structure includes the following steps: A nano-crosslinking agent with a two-dimensional planar structure was prepared using solid powder C, deionized water, metallic zirconium salt, and multifunctional compounds as reaction raw materials. The structural formula of the solid powder C is as follows: ； The multifunctional compound is one or more of glycerol, 1,3-propanediol, sorbitol, xylitol, lactic acid, citric acid, and phosphoric acid; The mass ratio of the solid powder C, deionized water, zirconium salt, and multifunctional compound is (0.8~0.9):(9~11):1:(1.3~1.6). The viscosity-average molecular weight of the low-molecular-weight salt-resistant thickener was determined to be 300-500 million Daltons using an Ubbelohde viscometer.

2. The low molecular weight salt-resistant thickener according to claim 1, characterized in that, The salt-resistant monomer containing sulfonic acid groups is one or more of acrylamide short-chain alkyl sulfonic acid, acrylamide naphthalene sulfonate, acrylamide benzene sulfonate, and ethylene benzene sulfonate; The amphiphilic associating monomer is one or both of acrylamide long-chain alkyl sulfonate and long-chain alkyl unsaturated quaternary ammonium salt; The alkyl carbon chain length in the acrylamide short-chain alkyl sulfonate is C3~C5; The alkyl carbon chain length in the acrylamide long-chain alkyl sulfonate or long-chain alkyl unsaturated quaternary ammonium salt is C12~C20. The dry powder particle size of the low molecular weight salt-resistant thickener is 80-120 mesh.

3. The low molecular weight salt-resistant thickener according to claim 1, characterized in that, The specific steps for preparing a nano-crosslinking agent with a two-dimensional planar structure are as follows: Solid powder C was ultrasonically dispersed in deionized water to obtain a dispersion. Zirconium salt was added to the deionized water to obtain a zirconium salt solution. The zirconium salt solution and the dispersion were stirred and mixed for more than 5-10 minutes. Then, a multifunctional compound was added and the mixture was stirred for more than 5-10 minutes. The pH was adjusted to 7.5-8.5 with a pH adjuster. The mixture was then reacted at 55-65℃ for 4.5-5 hours to obtain a nano-crosslinking agent with a two-dimensional planar structure.

4. The low molecular weight salt-resistant thickener according to claim 3, characterized in that, The pH adjuster is one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and sodium carbonate.

5. The low molecular weight salt-resistant thickener according to claim 4, characterized in that, The preparation method of the solid powder C is as follows: Solid powder A was prepared using molybdenum disulfide and hydrogen peroxide solution as reactants. The structural formula of solid powder A is as follows: ； Solid powder B was prepared by using solid powder A, ethanol aqueous solution, silane coupling agent and acetic acid as reaction raw materials. The structural formula of solid powder B is as follows: ； Solid powder C was prepared by using solid powder B, anhydrous N,N-dimethylformamide, succinic anhydride and triethylamine as reaction raw materials.

6. The low molecular weight salt-resistant thickener according to claim 5, characterized in that, The specific preparation method of the solid powder C is as follows: S1: Molybdenum disulfide was dispersed in hydrogen peroxide solution under ultrasonic conditions, followed by ultrasonic dispersion for 30-35 min, and then stirred in a water bath at 50-52℃ for 24-25 h or more to obtain a reaction solution; the reaction solution was centrifuged to obtain a precipitate, which was washed with deionized water until neutral, and then vacuum dried at 60-65℃ for 12-15 h or more to obtain solid powder A; S2: Add solid powder A to an ethanol-water solution and ultrasonically disperse for 30-35 min. Then add silane coupling agent and acetic acid in sequence. Then reflux the reaction at 80-82℃ for more than 8-9 h to obtain a reaction solution. After centrifuging the reaction solution, obtain a precipitate. Wash the precipitate with anhydrous ethanol 3-4 times and vacuum dry it at 50-55℃ for more than 20-24 h to obtain solid powder B. S3: Add solid powder B to N,N-dimethylformamide and disperse it by ultrasonication for 15-20 min. Then add succinic anhydride and triethylamine in sequence, and then reflux the reaction at 60-65℃ for more than 12-14 h to obtain a reaction solution. After centrifuging the reaction solution, a precipitate is obtained. The precipitate is washed three times with a mixture of N,N-dimethylformamide and anhydrous ethanol, and then vacuum dried at 60-65℃ for more than 12-15 h to obtain solid powder C.

7. The low molecular weight salt-resistant thickener according to claim 6, characterized in that, In S1, the mass concentration of the hydrogen peroxide solution is 30%~35%; the mass ratio of molybdenum disulfide to hydrogen peroxide solution is 1:(0.1~0.11). In S2, the mass ratio of solid powder A, ethanol aqueous solution, silane coupling agent, and acetic acid is 1:(1.5~1.6):(0.02~0.025):(0.001~0.0012); the mass concentration of the ethanol aqueous solution is 95%~98%. The silane coupling agent is one of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane; In S3, the mass ratio of the solid powder B, N,N-dimethylformamide, succinic anhydride, and triethylamine is 1:(0.8~0.9):2:(0.002~0.0025).

8. A method for preparing a low-molecular-weight anti-salt thickener according to any one of claims 1 to 7, characterized in that, Includes the following steps: Weigh out the following components according to their mass ratio: acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group, associative monomer containing amphiphilic group, and nano-crosslinking agent with two-dimensional planar structure for later use. Acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group and associative monomer containing amphiphilic group are added to water in sequence to obtain a mixed solution; The composite initiator and the molecular weight regulator were respectively prepared into a composite initiator solution and a molecular weight regulator solution; A composite initiator solution, a molecular weight regulator solution, and a nano-crosslinking agent with a two-dimensional planar structure were simultaneously added dropwise to a mixed solution, followed by a reaction. After the reaction was completed, a colloidal product was obtained. The colloidal product was post-processed to obtain a low-molecular-weight salt-resistant thickener.

9. The method for preparing a low-molecular-weight anti-salt thickener according to claim 8, characterized in that, While stirring, acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group and associative monomer containing amphiphilic group are added to water in sequence to obtain a mixed solution; the pH value of the mixed solution is adjusted to 7.8~8.2; In the mixed solution, the total mass concentration of acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, salt-resistant monomer containing sulfonic acid group and associative monomer containing amphiphilic group is 20%~30%.

10. The method for preparing a low-molecular-weight anti-salt thickener according to claim 8, characterized in that, The composite initiator solution is obtained by mixing a composite initiator with water; the molecular weight regulator solution is obtained by mixing a molecular weight regulator with water. The mass concentration of the composite initiator solution is 5.0%~6.0%; the mass concentration of the molecular weight regulator solution is 2.0%~3.0%. The composite initiator is a mixture of cerium ammonium nitrate, sodium bisulfite, and persulfate; the mass ratio of cerium ammonium nitrate, sodium bisulfite, and persulfate is (0.12~0.15):1:(1.2~1.25). The molecular weight regulator is one or more of isopropanol, sodium formate, urea, dodecyl mercaptan, and n-butyl mercaptan.

11. The method for preparing a low-molecular-weight anti-salt thickener according to claim 8, characterized in that, The composite initiator solution, molecular weight regulator solution, and nano-crosslinking agent with a two-dimensional planar structure are simultaneously added dropwise to a mixed solution at a temperature of 15-18℃ within 5-6 minutes. The reaction is carried out in an adiabatic polymerization apparatus for 5-6 hours. The amount of the composite initiator is 0.02% to 0.025% of the total mass of the acrylamide hydrophilic monomer, the sodium acrylate hydrophilic monomer, and the salt-resistant monomer containing sulfonic acid groups; The amount of the molecular weight regulator is 0.015% to 0.016% of the total mass of the acrylamide hydrophilic monomer, sodium acrylate hydrophilic monomer, and salt-resistant monomer containing sulfonic acid groups.

12. The method for preparing a low-molecular-weight anti-salt thickener according to claim 8, characterized in that, The post-processing includes chopping, drying, and sieving processes performed sequentially. The drying temperature is 105~110℃, and the drying time is 7~8 hours or more.

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