Bicapped hydrophobic monomers and methods of making same, polysaccharide modified polyacrylamide emulsions, and fracturing fluids

Abstract

The application provides a double-tail type hydrophobic monomer and a preparation method thereof, a polysaccharide modified polyacrylamide emulsion and a fracturing fluid, the double-tail type hydrophobic monomer has the following structure: wherein R1 is selected from a C6-C18 saturated alkyl group, a C6-C18 aryl group, a C6-C18 alkyl aryl group, a C6-C18 alkyl acid group, a C6-C18 alkyl alcohol group, a C6-C18 alkyl ester group or a C6-C18 alkyl benzene sulfonic acid group; and X is selected from chlorine, bromine or iodine. The double-tail type hydrophobic monomer, a water-soluble monomer and a functional monomer N,N'-methylene bisacrylamide are copolymerized by using a dispersion polymerization method, reversible physical cross-linking is formed through the association of hydrophobic groups, a huge molecular space network structure is formed, and the polymer solution has high viscosity, good temperature resistance, salt resistance and shear resistance at a low concentration.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field fracturing fluid technology, specifically relating to a double-tailed hydrophobic monomer and its preparation method, a polysaccharide-modified polyacrylamide emulsion, and a fracturing fluid. Background Technology

[0002] Synthetic polymers and natural polymers are the two main types of polymers used for reservoir fracturing. Synthetic polymers with added crosslinking agents are suitable for high temperatures and a wide pH range. While natural polymers remain stable at high temperatures and high salinity, they are expensive and susceptible to bacterial degradation. Graft copolymers of natural polysaccharides and synthetic copolymers can be used to improve the physical properties of polymers; pregelatinized starch, etherified starch, and grafted starch are all used as additives. Graft copolymers of natural and synthetic polymers have a wide range of applications because they combine the common properties of both natural and synthetic polymers within a single molecular chain. Graft copolymerization is an effective method for modifying the structure of natural and synthetic copolymers, making them suitable for enhanced oil recovery technologies in oil and gas fields. Attaching a rigid polysaccharide backbone to the polyacrylamide molecular chain can give the graft copolymer good thermal stability and shear resistance.

[0003] CN105521350A discloses a low-residue starch fracturing fluid, the composition and weight percentage of which are: thickener: 2%-4%, clay stabilizer: 0.5%-2%, temperature stabilizer: 0.1%-0.5%, drainage aid: 0.1%-1%, bactericide: 0.1%-0.3%, pH adjuster: 0.1%-0.3%, and the balance being water. CN110184043A discloses a fast-dissolving, residue-free modified cellulose fracturing fluid and its preparation method. The fracturing fluid is composed of the following components in parts by weight: MH-028 modified cellulose with acid thickener for fracturing (0.2-0.6 parts by weight); MH-031 aminotriethanol-based stabilizer for fracturing (0.1-0.4 parts by weight); MH-016 flow-out aid for fracturing and acidizing (0.2-0.6 parts by weight); MH-032 modified cellulose with hydroxyzirconium crosslinking agent for fracturing (0.2-0.5 parts by weight); MH-030 glycolic acid-based crosslinking accelerator (0.2-0.7 parts by weight); ammonium persulfate (0.003-0.001 parts by weight); and water (99.1-97.2 parts by weight). The above technology uses modified natural polymer fracturing fluids, which are more expensive and less damaging to reservoirs than synthetic polymer fracturing fluids.

[0004] Therefore, there is an urgent need to find a low-cost, low-residue, and low-damage fracturing fluid for unconventional oil and gas reservoir stimulation. This would reduce the cost of fracturing fluid, minimize its damage to unconventional reservoirs, and enhance the post-fracturing production increase and stabilization effect. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a dual-tailed hydrophobic monomer and its preparation method, a polysaccharide-modified polyacrylamide emulsion, and a fracturing fluid.

[0006] To achieve the above objectives, the present invention provides a double-tailed hydrophobic monomer having the structure shown in formula (Ⅰ):

[0007]

[0008] Wherein, R1 is selected from C6-C18 saturated alkyl, C6-C18 aryl, C6-C18 alkylaryl, C6-C18 alkyl acid, C6-C18 alkyl alcohol, C6-C18 alkyl ester or C6-C18 alkylbenzene sulfonic acid; X is selected from chlorine, bromine or iodine.

[0009] In the above-mentioned double-tailed hydrophobic monomers, preferably, R1 is selected from acetyl, nonyl, dodecyl, hexadecyl, phenyl, ethylphenyl, dodecylphenyl, dodecyl acid, hexadecyl acid, dodecyl alcohol, hexadecyl alcohol, ethyl hexadecyl acid, methyl hexadecyl acid, or ethylbenzenesulfonic acid.

[0010] This invention also provides a method for preparing a double-tailed hydrophobic monomer, comprising:

[0011] An amidation reaction was carried out between 3,3-iminobis(N,N-dimethylpropylamine) and acryloyl chloride to obtain a ditertiary amine monomer containing acrylamide;

[0012] The acrylamide-containing ditertiary amine monomer is subjected to a quaternization reaction with a haloalkane R1-X to obtain the double-tailed hydrophobic monomer.

[0013] The synthetic route of the double-tailed hydrophobic monomer of the present invention is as follows: Figure 1 As shown.

[0014] In the above-mentioned method for preparing the double-tailed hydrophobic monomer, preferably, the mass ratio of 3,3-iminobis(N,N-dimethylpropylamine) to acryloyl chloride is 40-80:12-24.

[0015] In the above-mentioned method for preparing the double-tailed hydrophobic monomer, preferably, the amidation reaction is carried out at a temperature of 40-80°C for a time of 4-8 hours.

[0016] In the above-mentioned method for preparing the double-tailed hydrophobic monomer, preferably, the amidation reaction is carried out in a first solvent, wherein the first solvent is selected from one or more combinations of dichloromethane, acetone, isopropanol, 70% ethanol, diethyl ether, and ethyl acetate.

[0017] In the above-mentioned method for preparing a double-tailed hydrophobic monomer, preferably, the mass ratio of the acrylamide-containing ditertiary amine monomer to the haloalkane R1-X is 20-40:15-50.

[0018] In the above-mentioned method for preparing the double-tailed hydrophobic monomer, preferably, the quaternization reaction is carried out at a temperature of 50-90℃ for 6-10 hours.

[0019] In the above-mentioned method for preparing the double-tailed hydrophobic monomer, preferably, the quaternization reaction is carried out in a second solvent, which is selected from one or more combinations of acetone, tetrahydrofuran, isopropanol, methanol, 70% ethanol, diethyl ether, cyclohexane, triethylamine, and N,N-dimethylformamide.

[0020] According to a specific embodiment of the present invention, preferably, the preparation method of the above-mentioned double-tailed hydrophobic monomer includes the following steps:

[0021] (1) Take 50-100 parts by weight of organic solvent and 40-80 parts by weight of 3,3-iminobis(N,N-dimethylpropylamine), and heat under reflux at 40-80℃; take 12-24 parts by weight of acryloyl chloride and 20-30 parts by weight of organic solvent to obtain acryloyl chloride solution, and add the acryloyl chloride solution dropwise to the reaction solution under reflux for reaction; after reacting for 4-8 hours, evaporate the solvent to concentrate, wash the concentrate with a mixed aqueous solution of saturated NaHCO3 and Na2CO3, then extract the washing solution with dichloromethane, evaporate the dichloromethane again, and purify the product by column chromatography to obtain a yellow oily substance, which is the ditertiary amine monomer containing acrylamide;

[0022] (2) Weigh 20-40 parts of the acrylamide-containing ditertiary amine monomer obtained in step (1) and 15-50 parts of haloalkane R1-X, add 50-200 parts of organic solvent, reflux at 50-90℃ for 6-12h, remove solvent by vacuum distillation, and obtain the double-tailed hydrophobic monomer.

[0023] The present invention also provides a polysaccharide-modified polyacrylamide emulsion, wherein, by mass percentage, its raw materials include: 5-20% acrylamide, 1-10% anionic salt-tolerant monomer, 0.01-0.5% bi-tailed hydrophobic monomer, 0.1-5% N,N'-methylenebisacrylamide, 2-10% polysaccharide, 1-4% dispersant, 10-30% inorganic salt, 0.01-0.2% initiator, and the balance being a dispersion medium; wherein the bi-tailed hydrophobic monomer is the above-mentioned bi-tailed hydrophobic monomer or obtained by the above-mentioned bi-tailed hydrophobic monomer preparation method.

[0024] In the polysaccharide-modified polyacrylamide emulsion of the present invention, the role of the double-tailed hydrophobic monomer is to enhance the hydrophobic association of the drag-reducing agent in water, enhance the network structure to achieve a good thickening effect, and at the same time, the quaternary ammonium salt group in the double-tailed hydrophobic monomer also has certain anti-swelling and bactericidal effects.

[0025] This invention modifies polyacrylamide with polysaccharides to prepare low-cost, biodegradable, and environmentally friendly polysaccharide-modified polyacrylamide water-in-water emulsion drag reducers. Therefore, there is a great demand for this product in fracturing stimulation. It can not only meet the performance requirements of fracturing fluid in fracturing stimulation, but also reduce the damage of fracturing fluid to unconventional oil and gas reservoirs, thereby achieving the goal of increasing and stabilizing the production of unconventional oil and gas reservoirs.

[0026] In the polysaccharide-modified polyacrylamide emulsion of the present invention, the polysaccharide-modified polyacrylamide has a structure as shown in formula (II): wherein the lower long chain structure is a repeating unit of the polysaccharide graft polymer.

[0027]

[0028] In formula (II), R2 is selected from starch, chitin, cellulose, agar, rhamnose, sodium alginate, hyaluronic acid or chitosan.

[0029] In the above-mentioned polysaccharide-modified polyacrylamide emulsion, preferably, the anionic salt-resistant monomer includes one or more of the following: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), propylene sulfonic acid, acrylamide tert-butyl sulfonate, sodium 3-acrylamido-3-methylbutyrate, 2-acrylamido-2-phenylethanesulfonic acid, and disodium ethylenediaminetetraacetate.

[0030] In the above-mentioned polysaccharide-modified polyacrylamide emulsion, preferably, the polysaccharide includes one or more of starch, chitin, cellulose, agar, rhamnose, sodium alginate, hyaluronic acid, and chitosan.

[0031] Preferably, the polysaccharide-modified polyacrylamide emulsion described above satisfies one or more of the following conditions:

[0032] The dispersant includes one or more of polymethyldiallylammonium chloride, polyacryloyloxyethyl dimethylbenzylammonium chloride, polymethacryloyloxyethyl trimethylammonium chloride, polyvinylpyrrolidone, and polyvinyl methyl ether.

[0033] The inorganic salt includes one or more of ammonium sulfate, sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

[0034] The initiator includes one or more of the following: potassium persulfate-sodium thiosulfate, potassium persulfate-potassium bisulfite, ammonium persulfate-sodium bisulfite, hydrogen peroxide-ferrous sulfate, azobisisobutyrazoline hydrochloride, and azobisisobutyramidine hydrochloride.

[0035] The dispersion medium includes one or a combination of two or more of methanol, ethanol, tert-butanol, polyethylene glycol, and water.

[0036] This invention also provides a method for preparing the above-mentioned polysaccharide-modified polyacrylamide emulsion, comprising:

[0037] Acrylamide, anionic salt-tolerant monomer, bi-tailed hydrophobic monomer, N,N'-methylenebisacrylamide, polysaccharide, dispersant, inorganic salt, and dispersion medium are mixed evenly. An initiator is added under nitrogen protection to carry out a polymerization reaction, thereby obtaining the polysaccharide-modified polyacrylamide emulsion.

[0038] In the above method for preparing polysaccharide-modified polyacrylamide emulsion, preferably, the polymerization reaction temperature is 30-60℃ and the time is 4-8h.

[0039] Emulsion drag reducers prepared by dispersion polymerization are beneficial for improving the dissolution rate of polymers in water, meeting the requirements of large-volume on-site construction. These drag reducers not only exhibit good solubility and dispersion in clean water and low-concentration brine, but also dissolve rapidly in high-mineralized produced water systems, while demonstrating excellent drag reduction performance. Compared to other polymerization methods, dispersion polymerization combines the advantages of simple and convenient aqueous solution polymerization with the characteristics of fast reaction rate and high relative molecular mass of products from reverse emulsion polymerization. The resulting polymer emulsion has good fluidity, is free of lumpy or particulate insoluble matter, and dissolves quickly. It does not require large dissolving equipment and can be directly injected into pipelines, facilitating automated operation and accurate metering, saving resources and manpower. It produces no harmful organic solvents, eliminating secondary environmental pollution. This technology significantly overcomes many problems associated with traditional products and processes, contributing to environmental protection and energy conservation, and effectively addressing heat dissipation issues. It is applicable to various monomers and can prepare monodisperse polymer particles of different particle sizes.

[0040] According to a specific embodiment of the present invention, preferably, the preparation method of the above-mentioned polysaccharide-modified polyacrylamide emulsion specifically includes the following steps:

[0041] Weigh acrylamide, anionic salt-resistant monomer, bi-tailed hydrophobic monomer, N,N'-methylenebisacrylamide, polysaccharide, dispersant, inorganic salt and dispersion medium according to the mass ratio, stir at room temperature to dissolve and mix the materials evenly; purge with nitrogen for 30-60 min, then heat to the reaction temperature of 30-60℃, add initiator, and react at a constant temperature for 4-8 h to prepare a polysaccharide-modified polyacrylamide water-in-water dispersion emulsion.

[0042] The present invention also provides a fracturing fluid comprising the above-mentioned polysaccharide-modified polyacrylamide emulsion.

[0043] According to a specific embodiment of the present invention, preferably, the raw materials of the fracturing fluid, by mass parts, include: 100 parts water, 0.02-2 parts of the polysaccharide-modified polyacrylamide emulsion, 0.01-0.5 parts of drainage aid, 0.01-0.2 parts of bactericide, and 0.01-0.5 parts of clay stabilizer.

[0044] Preferably, in the fracturing fluid described above, the drainage aid includes one or more of the following: sodium perfluorononenoxybenzenesulfonate (OBS), dodecyl dimethyl betaine, dodecyl hydroxysulfobetaine, cocamidopropyl hydroxysulfobetaine, alkanolamide (FFA), coconut oil fatty acid diethanolamide, and dodecyl trimethylammonium chloride.

[0045] Preferably, in the fracturing fluid described above, the clay stabilizer comprises one or more of the following: dodecyltrimethylammonium chloride, potassium chloride, sodium chloride, ammonium chloride, ethylenediamine dichloride, chitosan quaternary ammonium salt, polyamide, polyether ammonium, and polydimethyldiallylammonium chloride.

[0046] Preferably, in the fracturing fluid described above, the bactericide includes one or a combination of two or more of glutaraldehyde, formaldehyde, acrolein, hexadecyl dimethyl tertiary amine, dodecyl dimethyl benzyl ammonium chloride, and isothiazolinone.

[0047] According to a specific embodiment of the present invention, preferably, the preparation method of the above-mentioned fracturing fluid includes:

[0048] Weigh out the polysaccharide-modified polyacrylamide emulsion according to the specified ratio, dissolve it in water, and after it is fully dissolved, add the drainage aid, clay stabilizer, and bactericide, and mix thoroughly to obtain the fracturing fluid.

[0049] The technical solution provided by this invention has the following beneficial effects:

[0050] This invention employs dispersion polymerization to copolymerize a bi-tailed hydrophobic monomer with a water-soluble monomer and the functional monomer N,N'-methylenebisacrylamide. Through the association between hydrophobic groups, a reversible physical "crosslinking" is formed, creating a large molecular spatial network structure. This results in a polymer solution exhibiting high viscosity, good temperature and salt resistance, and shear resistance even at lower concentrations. The bi-tailed hydrophobic monomer has two hydrophobic chains, leading to stronger hydrophobic association in aqueous solutions after copolymerization, enhancing thickening and drag reduction / sand-carrying effects. The N,N'-methylenebisacrylamide functional monomer links the two long polymer chains, strengthening the spatial network structure and improving thickening. The bisquaternary ammonium salt groups of the bi-tailed hydrophobic monomer and the propanesulfonate groups (salt-resistant groups) of sodium 2-acrylamido-2-methylpropanesulfonate give the polyacrylamide emulsion good salt resistance, as well as some anti-swelling and bactericidal effects. Polysaccharides are used to modify the polyacrylamide copolymer, giving it good shear resistance, temperature resistance, biodegradability, and low toxicity. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the synthetic route for the double-tailed hydrophobic monomer of the present invention;

[0052] Figure 2 The 1H NMR spectrum of the double-tailed hydrophobic monomer 1 in Example 1;

[0053] Figure 3 The 1H NMR spectrum of the double-tailed hydrophobic monomer 2 in Example 2;

[0054] Figure 4 The infrared spectrum of the polysaccharide-modified polymer 1 in Example 5 is shown.

[0055] Figure 5 The infrared spectrum of polymer 2 modified with polysaccharides in Example 6 is shown.

[0056] Figure 6 The viscosity and drag reduction of the fracturing fluid in Example 9 at room temperature under different polymer (polysaccharide-modified polyacrylamide emulsion 1) dosages;

[0057] Figure 7 The surface tension of the fracturing fluid breaker in Example 9 at room temperature under different polymer (polysaccharide-modified polyacrylamide emulsion 1) dosages;

[0058] Figure 8 The linear expansion rate of the fracturing fluid breaker in Example 9 at room temperature with an addition of 0.4% polymer (polysaccharide-modified polyacrylamide emulsion 1);

[0059] Figure 9The fracturing fluid in Example 9 was subjected to an addition of 0.4% polymer (polysaccharide-modified polyacrylamide emulsion 1) at 120°C for 170 seconds. -1 Rheological curves after shearing for 60 minutes. Detailed Implementation

[0060] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0061] Example 1

[0062] This embodiment provides a dual-tailed hydrophobic monomer 1, the preparation method of which is as follows:

[0063] Add 50 g of dichloromethane and 40 g of 3,3-iminobis(N,N-dimethylpropylamine) to a 250 mL three-necked flask and heat to reflux at 50 °C. Then, add 15 g of acryloyl chloride to a feeding funnel containing 20 g of dichloromethane, and add the solution dropwise to the reaction flask. After reacting for 6 hours, evaporate the solvent to concentrate the product, and wash the concentrate with 20 g of a mixed aqueous solution of saturated NaHCO3 and Na2CO3. Introduce the aqueous solution into a separating funnel and extract three times with dichloromethane. Evaporate the solvent and purify the product using column chromatography. Evaporate the total eluent to obtain a yellow oily substance.

[0064] In a round-bottom flask, 20 g of a ditertiary amine monomer containing acrylamide and 15 g of chlorododecane were added, followed by 50 g of dichloromethane. The mixture was refluxed at 50 °C for 12 hours. The solvent was removed by vacuum distillation to obtain the double-tailed hydrophobic monomer 1, whose 1H NMR spectrum is shown below. Figure 2 As shown, the chemical structure of the double-tailed hydrophobic monomer 1 can be determined as shown in formula (III):

[0065]

[0066] Example 2

[0067] This embodiment provides a dual-tailed hydrophobic monomer 2, the preparation method of which is as follows:

[0068] 100 g of isopropanol and 80 g of 3,3-iminobis(N,N-dimethylpropylamine) were added to a 250 mL three-necked flask and heated to reflux at 80 °C. Then, 24 g of acryloyl chloride was added to a feeding funnel containing 30 g of isopropanol, and the solution was added dropwise to the reaction flask. After reacting for 4 hours, the solvent was evaporated and the mixture was concentrated. The concentrate was washed with 50 g of a mixed aqueous solution of saturated NaHCO3 and Na2CO3. The aqueous solution was introduced into a separating funnel and extracted 6 times with dichloromethane. The solvent was evaporated, and the product was purified by column chromatography. The total eluent was evaporated to obtain a yellow oily substance.

[0069] In a round-bottom flask, 40 g of a ditertiary amine monomer containing acrylamide and 50 g of sodium bromoethylbenzenesulfonate were added, followed by 100 g of triethylamine. The mixture was refluxed at 80 °C for 6 hours. The solvent was removed by vacuum distillation to obtain the double-tailed hydrophobic monomer 2, whose 1H NMR spectrum is shown below. Figure 3 As shown, the chemical structure of the double-tailed hydrophobic monomer 2 can be determined as shown in formula (Ⅳ):

[0070]

[0071] Example 3

[0072] This embodiment provides a dual-tailed hydrophobic monomer 3, the preparation method of which is as follows:

[0073] 75 g of 70% ethanol and 60 g of 3,3-iminobis(N,N-dimethylpropylamine) were added to a 250 mL three-necked flask and heated to reflux at 60 °C. Then, 16 g of acryloyl chloride was added to a feeding funnel containing 25 g of 70% ethanol, and the solution was added dropwise to the reaction flask. After reacting for 6 hours, the solvent was evaporated for concentration, and the concentrate was washed with 35 g of a mixed aqueous solution of saturated NaHCO3 and Na2CO3. The aqueous solution was introduced into a separating funnel and extracted five times with dichloromethane. The solvent was evaporated, and the product was purified by column chromatography. The total eluent was evaporated to obtain a yellow oily substance.

[0074] Add 30g of acrylamide ditertiary amine monomer and 35g of bromododecyl alcohol to a round-bottom flask, and add 100g of N,N-dimethylformamide. Reflux at 70°C for 8 hours. Remove the solvent by vacuum distillation to obtain the double-tailed hydrophobic monomer 3.

[0075] Example 4

[0076] This embodiment provides a dual-tailed hydrophobic monomer 4, the preparation method of which is as follows:

[0077] Add 80 g of diethyl ether and 70 g of 3,3-iminobis(N,N-dimethylpropylamine) to a 250 mL three-necked flask, heat to reflux at 70 °C, then add 12 g of acryloyl chloride to a feeding funnel containing 25 g of diethyl ether, and add the solution dropwise to the reaction flask; after reacting for 7 hours, evaporate the solvent to concentrate the product, and wash the concentrate with 40 g of a saturated aqueous solution of NaHCO3 and Na2CO3; introduce the aqueous solution into a separating funnel and extract four times with dichloromethane; evaporate the solvent and purify the product by column chromatography; evaporate the total eluent to obtain a yellow oily substance;

[0078] Add 35g of acrylamide ditertiary amine monomer and 40g of bromododecanoic acid to a round-bottom flask, and add 85g of tetrahydrofuran. Reflux at 65°C for 7 hours; remove solvent by vacuum distillation to obtain the double-tailed hydrophobic monomer 4.

[0079] Example 5

[0080] This embodiment provides a polysaccharide-modified polyacrylamide emulsion 1, the preparation method of which is as follows:

[0081] In a four-necked flask equipped with a condenser, thermometer, nitrogen inlet tube, and stirrer, add 20g acrylamide, 5g 2-acrylamido-2-methylpropanesulfonic acid, 0.1g of bi-tailed hydrophobic monomer 1, 2g N,N'-methylenebisacrylamide, 10g starch, 2g polymethyldiallyl ammonium chloride, 25g ammonium sulfate, and the balance 39.5g of 20% polyethylene glycol aqueous solution. Stir at room temperature to dissolve and mix the materials evenly. Purge with nitrogen for 60 minutes, then raise the temperature to the reaction temperature of 60°C, add 0.1g of ammonium persulfate-sodium bisulfite initiator system, and react at a constant temperature for 6 hours to prepare polysaccharide-modified polyacrylamide emulsion 1. Its polymer structure is shown in Formula V, and its infrared spectrum is shown in [reference needed]. Figure 4 3456cm -1 The peak at 3398 cm⁻¹ is the absorption peak of the stretching vibration of NH₂ in amide; -1 The characteristic absorption peak of OH is at 3190 cm⁻¹. -1 The characteristic absorption peak of NH is at 2932 cm⁻¹. -1 The peaks at 1680 cm⁻¹ represent the absorption peaks of both asymmetric and symmetric vibrations of CH₂. -1 1550cm -1 The absorption peak at 1406 cm⁻¹ is a characteristic peak of the amide bond; -1 Characteristic peak of quaternary ammonium salt; 1315 cm⁻¹ -1 The CN absorption peak for secondary amides is at 1042 cm⁻¹. -1 641cm -1 The peak at this location is a characteristic absorption peak for SO3.

[0082]

[0083] Example 6

[0084] This embodiment provides a polysaccharide-modified polyacrylamide emulsion 2, the preparation method of which is as follows:

[0085] In a four-necked flask equipped with a condenser, thermometer, nitrogen inlet tube, and stirrer, add 10g acrylamide, 2g acrylamide tert-butyl sulfonate, 0.2g bi-tailed hydrophobic monomer 2, 0.2g N,N'-methylenebisacrylamide, 4g chitin, 1g polymethacryloyloxyethyltrimethylammonium chloride, 12g potassium sulfate, and the balance 70.6g of 15% tert-butanol aqueous solution. Stir at room temperature to dissolve and mix the materials evenly. Purge with nitrogen for 45 minutes, then raise the temperature to the reaction temperature of 40°C, add 0.05g of azodiisobutylamidine hydrochloride initiator, and react at a constant temperature for 8 hours to prepare polysaccharide-modified polyacrylamide emulsion 2. Its polymer structure is shown in Formula VI, and its infrared spectrum is shown in [reference needed]. Figure 5 3516cm -1 The peak at 3365 cm⁻¹ is the absorption peak of the stretching vibration of NH₂ in amide; -1 The characteristic absorption peak of OH is at 3190 cm⁻¹. -1 The characteristic absorption peak of NH is at 2938 cm⁻¹. -1 The peak at 1676 cm⁻¹ represents the absorption peaks of both asymmetric and symmetric vibrations of CH₂. -1 1550cm -1 The absorption peak at 1418 cm⁻¹ is a characteristic peak of the amide bond; -1 Characteristic peaks for benzene rings and quaternary ammonium salts; 1321 cm⁻¹ -1 The CN absorption peak is located at 1038 cm⁻¹. -1 664cm -1 The peak at this location is a characteristic absorption peak for SO3.

[0086]

[0087] Example 7

[0088] This embodiment provides a polysaccharide-modified polyacrylamide emulsion 3, the preparation method of which is as follows:

[0089] In a four-necked flask equipped with a condenser, thermometer, nitrogen inlet tube, and stirrer, add 5g acrylamide, 8g acrylic acid, 0.3g of bi-tailed hydrophobic monomer 2, 5g N,N'-methylenebisacrylamide, 6g cellulose, 4g polyvinylpyrrolidone, 25g sodium chloride, and the remainder 46.7g of 10% methanol aqueous solution. Stir at room temperature to dissolve and mix the materials evenly. Purge with nitrogen for 30 minutes, then heat to the reaction temperature of 30°C, add 0.2g of hydrogen peroxide-ferrous sulfate initiator, and react at a constant temperature for 5 hours to prepare polysaccharide-modified polyacrylamide emulsion 3.

[0090] Example 8

[0091] This embodiment provides a polysaccharide-modified polyacrylamide emulsion 4, which is prepared by the following method:

[0092] In a four-necked flask equipped with a condenser, thermometer, nitrogen inlet tube, and stirrer, add 20g acrylamide, 10g 2-acrylamido-2-phenylethanesulfonic acid, 0.5g of 2-dihydroxy-2-tailed hydrophobic monomer, 4g N,N'-methylenebisacrylamide, 10g chitosan, 4g disodium ethylenediaminetetraacetate, 30g sodium sulfate, and the remainder is 21.5g of 40% aqueous ethanol solution. Stir at room temperature to dissolve and mix the materials evenly. Purge with nitrogen for 60 minutes, then raise the temperature to the reaction temperature of 50°C, add 0.15g of azobisisobutyrazoline hydrochloride initiator, and react at a constant temperature for 6 hours to prepare polysaccharide-modified polyacrylamide emulsion 4.

[0093] Example 9

[0094] This embodiment provides a fracturing fluid, the preparation method of which is as follows:

[0095] Weigh 1g of polysaccharide-modified polyacrylamide emulsion 1 and dissolve it in 1000g of water under mechanical stirring at 600rad / min at room temperature. After dissolving for 30s, add 1g of sodium perfluorononenoxybenzenesulfonate, then add 2g of polydimethyldiallylammonium chloride and 1g of glutaraldehyde. Stir thoroughly for 30s to mix evenly, and the fracturing fluid is obtained.

[0096] The following investigation examines the effect of feedstock dosage (based on water mass as 100%) on fracturing fluid performance:

[0097] The dosage of polysaccharide-modified polyacrylamide emulsion 1 was changed, and the fracturing fluid formulation in Example 7 was used. The test results of its viscosity and drag reduction rate, surface tension, linear expansion rate, residue content and core damage rate are as follows: Figures 6-9 As shown.

[0098] The results showed that when the dosage of polysaccharide-modified polyacrylamide emulsion 1 was 0.05-0.6%, the fracturing fluid viscosity was between 9-102 mPa·s, and adjusting the polymer dosage could achieve increased fracturing fluid viscosity. When the dosage of drag reducer 1 was 0.1% (denoted as 0.1% polymer-doped fracturing fluid, the same below), the drag reduction rate of the fracturing fluid was 76.1%; the drag reduction rate of fracturing fluids with 0.05-0.6% polymer dosage was all >70%, demonstrating good drag reduction effect.

[0099] The fracturing fluid breaker obtained by adding 0.02% ammonium persulfate breaker to fracturing fluid and heating it at 70°C for 2 hours is the fracturing fluid breaker. At this point, the viscosity of the solution is close to that of water, between 1-2 mPa·s. The surface tension of the 0.05-0.6% polymer fracturing fluid breaker is less than 28 mN / m, meeting the requirement for low surface tension in fracturing fluids. The linear expansion rate of the 0.4% fracturing fluid breaker on tight sandstone is 0.97%, while that of water is 7.08%. This concentration of fracturing fluid breaker has an anti-swelling rate of 86.3% and exhibits weak water-sensitive damage.

[0100] Example 10

[0101] This embodiment provides a fracturing fluid, the preparation method of which is as follows:

[0102] Weigh 5g of polysaccharide-modified polyacrylamide emulsion 1 and dissolve it in 1000g of water under mechanical stirring at 800rad / min at room temperature. After dissolving for 45s, add 2g of cocamidopropyl hydroxysulfonate betaine, then add 4g of dodecyltrimethylammonium chloride and 2g of dodecyldimethylbenzylammonium chloride and stir thoroughly for 30s to mix evenly to obtain fracturing fluid.

[0103] Example 11

[0104] This embodiment provides a fracturing fluid, the preparation method of which is as follows:

[0105] Weigh 0.5g of polysaccharide-modified polyacrylamide emulsion 2 and dissolve it in 1000g of water under mechanical stirring at 500rad / min at room temperature. After dissolving for 30s, add 0.5g of dodecyl dimethyl betaine, then add 1g of chitosan quaternary ammonium salt and 0.5g of acrolein. Stir thoroughly for 30s to mix evenly to obtain the fracturing fluid.

[0106] Example 12

[0107] This embodiment provides a fracturing fluid, the preparation method of which is as follows:

[0108] Weigh 10g of polysaccharide-modified polyacrylamide emulsion 2 and dissolve it in 1000g of water under mechanical stirring at 1000rad / min at room temperature. After dissolving for 60s, add 4g of alkanolamide, then add 0.5g of polyether ammonium and 0.2g of formaldehyde and stir thoroughly for 30s to obtain the fracturing fluid.

[0109] Example 13

[0110] This embodiment provides a fracturing fluid, the preparation method of which is as follows:

[0111] Weigh 4g of polysaccharide-modified polyacrylamide emulsion 3 and dissolve it in 1000g of water under mechanical stirring at 800 rad / min at room temperature. After dissolving for 40s, add 2g of dodecyl hydroxysulfonate betaine, then add 2g of dodecyl trimethylammonium chloride and 1g of isothiazolinone and stir thoroughly for 15s to mix evenly to obtain fracturing fluid.

[0112] Example 14

[0113] This embodiment provides a fracturing fluid, the preparation method of which is as follows:

[0114] Weigh 6g of polysaccharide-modified polyacrylamide emulsion 4 and dissolve it in 1000g of water under mechanical stirring at 1000rad / min at room temperature. After dissolving for 45s, add 3g of coconut oil fatty acid diethanolamide, then add 2g of ethylenediamine dichloride and 0.5g of hexadecyl dimethyl tertiary amine and stir thoroughly to obtain fracturing fluid.

[0115] Comparative Example 1

[0116] This comparative example provides a fracturing fluid, the preparation method of which is as follows:

[0117] Weigh 1g of polyacrylamide powder drag reducer and dissolve it in 1000g of water under mechanical stirring at 600rad / min at room temperature. After dissolving for 30s, add 1g of sodium perfluorononenoxybenzenesulfonate, then add 2g of polydimethyldiallylammonium chloride and 1g of glutaraldehyde. Stir thoroughly for 30s to mix evenly to obtain the fracturing fluid.

[0118] Comparative Example 2

[0119] This paper provides a fracturing fluid in a comparative example, and its preparation method is as follows:

[0120] Weigh 1g of polyacrylamide suspension emulsion drag reducer and dissolve it in 1000g of water under mechanical stirring at 600rad / min at room temperature. After dissolving for 30s, add 1g of sodium perfluorononenoxybenzenesulfonate, then add 2g of polydimethyldiallylammonium chloride and 1g of glutaraldehyde. Stir thoroughly for 30s to mix evenly to obtain the fracturing fluid.

[0121] Comparative Example 3

[0122] This paper provides a fracturing fluid in a comparative example, and its preparation method is as follows:

[0123] Weigh 1g of polyacrylamide reverse emulsion drag reducer and dissolve it in 1000g of water under mechanical stirring at 600rad / min at room temperature. After dissolving for 30s, add 1g of sodium perfluorononenoxybenzenesulfonate, then add 2g of polydimethyldiallylammonium chloride and 1g of glutaraldehyde. Stir thoroughly for 30s to mix evenly to obtain the fracturing fluid.

[0124] Comparative Example 4

[0125] This comparative example provides a polyacrylamide emulsion and a fracturing fluid prepared therefrom; wherein, the preparation method of the polyacrylamide emulsion is the same as that of Example 5, except that no double-tailed hydrophobic monomer is added;

[0126] The fracturing fluid was prepared in the same way as in Example 9, except that the polyacrylamide emulsion prepared in this comparative example was used instead of the polysaccharide-modified polyacrylamide emulsion 1.

[0127] The core damage rate, residue content, linear expansion rate, drag reduction rate, biodegradability, and compatibility with formation water of the fracturing fluids of Examples 9-14 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0128] Table 1 Performance test results of fracturing fluid

[0129]

[0130]

[0131] The results showed that the residual content of the fracturing fluids in Examples 9-14 was all <100 mg / L, the core damage rate to tight sandstone was <10%, the surface tension was <28 mN / m, the swelling prevention rate was greater than 80%, and no precipitation occurred with formation water, demonstrating low damage characteristics to tight sandstone reservoirs. The viscosity retention rate at 30000 mg / L NaCl + 3000 mg / L CaCl2 was >50%, and the viscosity retention rate was 170 s. -1 The viscosity retention rate at 120℃ for 1 hour was >50%, demonstrating good salt resistance, temperature resistance, and shear resistance. After adding 0.1g of α-starch ether and allowing it to stand at 60℃ for 5 minutes, the viscosity retention rate of Examples 9-14 was all below 40%. In contrast, the viscosity retention rate of Comparative Examples 1-3 was all greater than 98%, indicating that the polysaccharide-modified polyacrylamide drag reducer has better biodegradability than the unmodified polyacrylamide drag reducer, and can reduce the amount of breaker used during on-site injection. The residue content and damage to tight sandstone in Comparative Examples 1-3 were greater than those in Examples 9-14, indicating that the polysaccharide-modified polyacrylamide drag reducer and fracturing fluid are low-damage fracturing fluids. The surface tension and core damage rate of Comparative Example 4 were higher than those in Examples 9-14, indicating that the introduction of the dual-tailed hydrophobic monomer significantly reduced the core damage rate.

[0132] The fracturing fluids in Examples 9-14 exhibit superior temperature, salt, and shear resistance compared to Comparative Examples 1-4. They also effectively address the difficulty of adding large-volume powder drag-reducing agents during on-site preparation, as seen in Comparative Example 1. Furthermore, they eliminate the need for bulky dissolving equipment, thus saving costs. Compared to Comparative Examples 2 and 3, the fracturing fluids of this invention do not contain suspending agents or oil phases, further reducing costs. Compared to Comparative Example 4, the introduction of dual-tailed hydrophobic monomers significantly reduces reservoir damage.

Claims

1. A double-tailed hydrophobic monomer having the structure shown in formula (Ⅰ): in, R1 is selected from C6-C18 saturated alkyl, C6-C18 aryl, C6-C18 alkylaryl, C6-C18 alkyl acid, C6-C18 alkyl alcohol, C6-C18 alkyl ester or C6-C18 alkylbenzene sulfonic acid; X is selected from chlorine, bromine or iodine.

2. The dual-tailed hydrophobic monomer according to claim 1, wherein, R1 can be any of the following: alkyl, nonyl, dodecyl, hexadecyl, phenyl, ethylphenyl, dodecylphenyl, dodecyl acid, hexadecyl acid, dodecyl alcohol, hexadecyl alcohol, ethyl hexadecyl acid, methyl hexadecyl acid, or ethylbenzenesulfonic acid.

3. A method for preparing the double-tailed hydrophobic monomer according to claim 1 or 2, comprising: An amidation reaction was carried out between 3,3-iminobis(N,N-dimethylpropylamine) and acryloyl chloride to obtain a ditertiary amine monomer containing acrylamide; The acrylamide-containing ditertiary amine monomer is subjected to a quaternization reaction with a haloalkane R1-X to obtain the double-tailed hydrophobic monomer.

4. The method for preparing the dual-tailed hydrophobic monomer according to claim 3, wherein, The mass ratio of 3,3-iminobis(N,N-dimethylpropylamine) to acryloyl chloride is 40-80:12-24.

5. The method for preparing the double-tailed hydrophobic monomer according to claim 3, wherein, The amidation reaction is carried out at a temperature of 40-80℃ for 4-8 hours. And / or, the amidation reaction is carried out in a first solvent, the first solvent being selected from one or more combinations of dichloromethane, acetone, isopropanol, 70% ethanol, diethyl ether, and ethyl acetate.

6. The method for preparing the dual-tailed hydrophobic monomer according to claim 3, wherein, The mass ratio of the acrylamide-containing ditertiary amine monomer to the haloalkane R1-X is 20-40:15-50.

7. The method for preparing the dual-tailed hydrophobic monomer according to claim 3, wherein, The quaternization reaction is carried out at a temperature of 50-90℃ for 6-10 hours. And / or, the quaternization reaction is carried out in a second solvent, the second solvent being selected from one or more combinations of acetone, tetrahydrofuran, isopropanol, methanol, 70% ethanol, diethyl ether, cyclohexane, triethylamine, and N,N-dimethylformamide.

8. A polysaccharide-modified polyacrylamide emulsion, comprising, by weight percentage: Acrylamide 5-20%, anionic salt-tolerant monomer 1-10%, bi-tailed hydrophobic monomer 0.01-0.5%, N,N'-methylenebisacrylamide 0.1-5%, polysaccharide 2-10%, dispersant 1-4%, inorganic salt 10-30%, initiator 0.01-0.2%, with the balance being dispersion medium; the bi-tailed hydrophobic monomer is the bi-tailed hydrophobic monomer described in claim 1 or 2 or obtained by the preparation method of the bi-tailed hydrophobic monomer described in any one of claims 3-7.

9. The polysaccharide-modified polyacrylamide emulsion according to claim 8, wherein, The anionic salt-tolerant monomer includes one or more of the following: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, propylene sulfonic acid, acrylamide tert-butyl sulfonate, sodium 3-acrylamido-3-methylbutyrate, 2-acrylamido-2-phenylethanesulfonic acid, and disodium ethylenediaminetetraacetate.

10. The polysaccharide-modified polyacrylamide emulsion according to claim 8, wherein, The polysaccharide includes one or more of starch, chitin, cellulose, agar, rhamnose, sodium alginate, hyaluronic acid, and chitosan.

11. The polysaccharide-modified polyacrylamide emulsion according to claim 8, wherein, The dispersant includes one or more of polymethyldiallylammonium chloride, polyacryloyloxyethyl dimethylbenzylammonium chloride, polymethacryloyloxyethyl trimethylammonium chloride, polyvinylpyrrolidone, and polyvinyl methyl ether. And / or, the inorganic salt includes one or more of ammonium sulfate, sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate; And / or, the initiator includes one or more of the following: potassium persulfate-sodium thiosulfate, potassium persulfate-potassium bisulfite, ammonium persulfate-sodium bisulfite, hydrogen peroxide-ferrous sulfate, azobisisobutyrazoline hydrochloride, and azobisisobutyramidine hydrochloride. And / or, the dispersion medium includes one or more of methanol, ethanol, tert-butanol, polyethylene glycol, and water.

12. A method for preparing a polysaccharide-modified polyacrylamide emulsion according to any one of claims 8-11, comprising: Acrylamide, anionic salt-tolerant monomer, bi-tailed hydrophobic monomer, N,N'-methylenebisacrylamide, polysaccharide, dispersant, inorganic salt, and dispersion medium are mixed evenly. An initiator is added under nitrogen protection to carry out a polymerization reaction, thereby obtaining the polysaccharide-modified polyacrylamide emulsion.

13. The method for preparing the polysaccharide-modified polyacrylamide emulsion according to claim 12, wherein, The polymerization reaction is carried out at a temperature of 30-60℃ for 4-8 hours.

14. A fracturing fluid comprising the polysaccharide-modified polyacrylamide emulsion according to any one of claims 8-11.

15. The fracturing fluid according to claim 14, wherein, The raw materials of the fracturing fluid, by weight, include: 100 parts water, 0.02-2 parts polysaccharide-modified polyacrylamide emulsion, 0.01-0.5 parts drainage aid, 0.01-0.2 parts bactericide, and 0.01-0.5 parts clay stabilizer.

16. The fracturing fluid according to claim 15, wherein, The drainage aid includes one or more of the following: sodium perfluorononenoxybenzenesulfonate, dodecyl dimethyl betaine, dodecyl hydroxysulfonate, cocamidopropyl hydroxysulfonate, alkanolamide, coconut oil fatty acid diethanolamide, and dodecyl trimethylammonium chloride. And / or, the clay stabilizer comprises one or more of the following: dodecyltrimethylammonium chloride, potassium chloride, sodium chloride, ammonium chloride, ethylenediamine dichloride, chitosan quaternary ammonium salt, polyamide, polyether ammonium, and polydimethyldiallylammonium chloride; And / or, the bactericide includes one or more of glutaraldehyde, formaldehyde, acrolein, hexadecyl dimethyl tertiary amine, dodecyl dimethyl benzyl ammonium chloride, and isothiazolinone.

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