An amide bridged silicone modified polymer, a preparation method thereof, a gel fracturing fluid, a preparation method and application thereof

Abstract

The application provides an amide bridged organosilicon modified polymer and a preparation method thereof, a gel fracturing fluid and a preparation method and application thereof, and belongs to the technical field of oil development. The preparation method of the amide bridged organosilicon modified polymer comprises the following steps: acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid and 5-methyl-3-vinyl oxazolidine-2-ketone are added into water, the pH value of the system is adjusted to 5.5-7.5, nitrogen is blown to remove oxygen, then heating is performed to a reaction temperature, 3-acrylamide propyl trimethoxysilane is added, and a premixing solution is obtained; an initiator is added into the premixing solution to perform reaction; after the reaction is completed, washing, drying and grinding are performed, and the amide bridged organosilicon modified polymer is obtained. The amide bridged organosilicon modified polymer is used for preparing a gel fracturing fluid, the gel fracturing fluid has excellent temperature resistance and shear resistance, can be applied to a 220 DEG C reservoir environment, has easy gel breaking in the reservoir, has low residue content, has low reservoir damage, and has great oilfield field application potential.

Description

Technical Field

[0001] This invention relates to an amide-bridged organosilicon modified polymer and its preparation method, a gel fracturing fluid and its preparation method and application, belonging to the field of petroleum development technology. Background Technology

[0002] Deep and ultra-deep oil and gas reservoirs are generally characterized by large burial depths, high formation temperatures, high in-situ stress, complex pore structures, low permeability, and strong heterogeneity. These reservoirs have limited natural fracture development, high fluid flow resistance, and low natural oil and gas production. Therefore, reservoir stimulation technologies such as hydraulic fracturing are typically used to establish a network of highly conductive artificial fractures to improve oil and gas flow channels and enhance reservoir utilization. Fracturing fluid, as the lifeblood of fracturing, determines the success or failure of fracturing operations. Therefore, efficient development of deep and ultra-deep oil and gas reservoirs places higher demands on the temperature resistance, rheological stability, and proppant carrying capacity of fracturing fluids.

[0003] Currently, commonly used fracturing fluid systems mainly include slickwater fracturing fluid, viscoelastic surfactant-cleaned fracturing fluid, CO2 foam fracturing fluid, and polymer gel fracturing fluid. Slickwater fracturing fluid is mostly suitable for medium- and low-temperature reservoirs, typically maintaining good drag reduction performance at 80-120℃, but it is prone to molecular chain thermal degradation under high-temperature and high-salinity conditions. Viscoelastic surfactant-cleaned fracturing fluid mainly relies on the self-assembly of surfactant molecules to form a worm-like micelle network to achieve viscosity enhancement and viscoelastic construction, but the temperature resistance of conventional systems is mostly between 90-120℃, and its micelle structure is quite sensitive to temperature, salinity, and oil-water environment. CO2 foam fracturing fluid forms a foam structure through gas-liquid two-phase dispersion, relying on foam film strength, bubble accumulation, and interfacial viscoelasticity to control proppant carrying and filtration loss. Existing experimental studies on high-temperature resistant CO2 foam systems are mostly concentrated at 90-150℃, and the foam is prone to aggregation, separation, and decreased stability under high temperature and pressure. In contrast, polymer gel fracturing fluids mainly rely on the entanglement of thickener molecular chains and the cross-linking between cross-linking agents and polymer functional groups to form a three-dimensional network structure. They have high viscoelasticity, strong sand-carrying capacity and good high-temperature adaptability, and can achieve good fracturing operation results in deep and ultra-deep high-temperature (>180℃) environments.

[0004] The temperature resistance of polymers directly determines the performance of polymeric gel fracturing fluids, which are mainly divided into two categories: natural polymers and synthetic polymers. Natural polymers are primarily guar gum, with a pyrolysis temperature of 177℃ for the glycosidic bonds in the polymer molecular chain, making them unsuitable for reservoirs with temperatures exceeding 180℃. Synthetic polymers are mainly modified polyacrylamide, achieved through copolymerization of acrylamide (AM) with monomers such as N-vinylpyrrolidone (NVP), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), methacryloyloxyethyltrimethylammonium chloride (DMC), and hydrophobic long-chain acrylamides. Electrostatic interactions, supramolecular interactions, and hydrophobic association enhance their temperature resistance. For example, Chinese patent document CN121495568A discloses a method for preparing synthetic polymers using AM, AA, AMPS, pAMPS, octadecyl methacrylate, and 4-vinylpyridinylpropyl sulfobetaine (synthesized) as raw materials via polymerization; however, this preparation method is overly complex. Chinese patent document CN121591950A discloses a high-temperature resistant polymer copolymerized from quaternary monomers AM, AA, AMPS and N-vinylcaprolactam, but the high content of the heat-resistant monomers leads to a significant increase in application costs.

[0005] Therefore, there is an urgent need to synthesize a high-temperature resistant polymer to prepare a high-temperature resistant polymer gel fracturing fluid, so as to achieve efficient development of deep and ultra-deep oil and gas. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an amide-bridged organosilicon-modified polymer and its preparation method, as well as a gel fracturing fluid and its preparation method and application. The amide-bridged organosilicon-modified polymer prepared by this invention exhibits excellent high-temperature resistance, the polymer preparation method is simple, and the prepared multi-network reinforced gel fracturing fluid demonstrates excellent high-temperature resistance, high viscosity retention, excellent proppant carrying capacity, easy gel breaking, low residue content, and low application cost.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing an amide-bridged organosilicon-modified polymer includes the following steps: Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and 5-methyl-3-vinyloxazolidine-2-one were added to water, and the pH of the system was adjusted to 5.5-7.5. After purging with nitrogen to remove oxygen, the mixture was heated to the reaction temperature, and then 3-acrylamidopropyltrimethoxysilane was added to obtain a premix. An initiator was added to the premix to carry out the reaction. After the reaction was completed, the mixture was washed, dried, and ground to obtain an amide-bridged organosilicon modified polymer.

[0008] According to a preferred embodiment of the present invention, based on the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane as 100%, the mass percentage of 2-acrylamido-2-methylpropanesulfonic acid is 10-18%, the mass percentage of acrylic acid is 1-7%, the mass percentage of 5-methyl-3-vinyloxazolidine-2-one is 1-4%, the mass percentage of 3-acrylamidopropyltrimethoxysilane is 1-4%, and the balance is acrylamide. Further preferably, based on the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane as 100%, the mass percentage of 2-acrylamido-2-methylpropanesulfonic acid is 12-16%, the mass percentage of acrylic acid is 4-6%, the mass percentage of 5-methyl-3-vinyloxazolidine-2-one is 2-3%, the mass percentage of 3-acrylamidopropyltrimethoxysilane is 1-2%, and the balance is acrylamide.

[0009] According to a preferred embodiment of the present invention, sodium hydroxide is used to adjust the pH of the system to 5.5-7.5, and more preferably, sodium hydroxide is used to adjust the pH of the system to 6.0-6.5.

[0010] According to a preferred embodiment of the present invention, the nitrogen deoxygenation time is 20-40 minutes.

[0011] According to a preferred embodiment of the present invention, the total mass concentration of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one and 3-acrylamidopropyltrimethoxysilane in the premix is ​​20-40 wt%, more preferably 25-35 wt%.

[0012] According to a preferred embodiment of the present invention, the initiator is 2,2'-azabis(2-imidazoline) dihydrochloride, 2,2'-azobisisobutylamidine dihydrochloride, or 4,4'-azobis(4-cyanopentanoic acid); the mass of the initiator is 0.02-0.06% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidin-2-one, and 3-acrylamidopropyltrimethoxysilane, more preferably 0.03-0.05%.

[0013] According to a preferred embodiment of the present invention, the reaction temperature is 35-60°C, more preferably 45-55°C; the reaction time is 2-7 hours, more preferably 4-6 hours; and the reaction is carried out under nitrogen protection.

[0014] According to a preferred embodiment of the present invention, the washing is performed using ethanol; the drying is performed by vacuum drying at 55-65°C for 24-48 hours.

[0015] This invention provides an amide-bridged organosilicon-modified polymer, which is prepared using the above-described preparation method.

[0016] The present invention also provides a gel fracturing fluid comprising the following raw materials in weight percentage: 0.02-0.07% modified inorganic nanomaterials, 0.5-0.9% of the above-mentioned amide-bridged organosilicon modified polymer, 0.3-1.2% organozirconium crosslinking agent, and the balance being water; and the mass ratio of organozirconium crosslinking agent to amide-bridged organosilicon modified polymer is 0.5-2:1.

[0017] According to a preferred embodiment of the present invention, the gel fracturing fluid comprises the following raw materials in the following mass percentages: 0.04-0.06% modified inorganic nanomaterials, 0.6-0.8% of the above-mentioned amide-bridged organosilicon modified polymer, 0.6-1.2% organozirconium crosslinking agent, and the balance being water; and the mass ratio of organozirconium crosslinking agent to amide-bridged organosilicon modified polymer is 1-1.5:1.

[0018] According to a preferred embodiment of the present invention, the modified inorganic nanomaterial is obtained by modifying inorganic nanomaterials with a silane coupling agent; the inorganic nanomaterial is one or more of nano-SiO2, sepiolite nanofibers, and attapulgite; the silane coupling agent is γ-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), or γ-methacryloyloxypropyltrimethoxysilane (KH570), and the mass ratio of the silane coupling agent to the inorganic nanomaterial is 0.01-0.2:1; the particle size of the nano-SiO2 is 40-60 nm; the diameter of the sepiolite nanofibers is 10-100 nm, and the aspect ratio is 10-300; the diameter of the attapulgite is 10-80 nm, and the length is 0.5-5 μm.

[0019] According to the present invention, the modified inorganic nanomaterial can be obtained commercially or prepared according to existing technology; more preferably, the modified inorganic nanomaterial is prepared according to the following method: (1) Add inorganic nanomaterials to anhydrous ethanol and disperse them evenly by ultrasonication to obtain a suspension; (2) Adjust the pH of the ethanol aqueous solution to 4-5, add silane coupling agent to hydrolyze, and obtain hydrolysate; (3) Under stirring conditions, the hydrolysate obtained in step (2) is added to the suspension obtained in step (1) to carry out the reaction; after the reaction is completed, the modified inorganic nanomaterial is obtained by centrifugation, washing, drying and grinding.

[0020] According to a preferred embodiment of the present invention, the mass ratio of the inorganic nanomaterial to the volume of anhydrous ethanol in step (1) is 1g:20-40mL.

[0021] According to a preferred embodiment of the present invention, in step (2), the volume ratio of ethanol to water in the aqueous ethanol solution is 1-3:1; the pH value of the aqueous ethanol solution is adjusted to 4-5 using acetic acid; the mass ratio of the silane coupling agent to the volume of the aqueous ethanol solution is 1g:3-6mL; the hydrolysis time is 4-6h, and the hydrolysis temperature is room temperature.

[0022] According to a preferred embodiment of the present invention, the drop rate of the hydrolysate in step (3) is 1-2 drops / s; the reaction temperature is 70-80°C; the reaction time is 5-7 hours; the washing is centrifugation with anhydrous ethanol 3-5 times; and the drying is vacuum drying at 60-70°C for 6-10 hours.

[0023] According to a preferred embodiment of the present invention, the organozirconium crosslinking agent is prepared by an organic ligand and an aqueous solution of zirconium oxychloride; the organic ligand is one or more of lactic acid, citric acid, triethanolamine, diethanolamine, glycerol, mannitol, and sorbitol; the mass ratio of zirconium oxychloride to water in the aqueous solution of zirconium oxychloride is 1-3:10; and the mass ratio of the organic ligand to the aqueous solution of zirconium oxychloride is 3-5:1.

[0024] According to the present invention, the organozirconium crosslinking agent is commercially available or prepared according to existing technology; preferably, the organozirconium crosslinking agent is prepared according to the following method: After preheating the zirconium oxychloride aqueous solution, an organic ligand is added to it; then, the pH of the system is adjusted to 7 using NaOH, and the reaction is carried out. After cooling, an organozirconium crosslinking agent is obtained; the preheating is carried out at 70-80℃ for 5-10 min, and the reaction is carried out at 70-80℃ for 3-5 h.

[0025] According to the present invention, the preparation method of the above-mentioned gel fracturing fluid includes the following steps:

[0026] The modified inorganic nanomaterials were dispersed in water to obtain a dispersion; the above-mentioned amide-bridged organosilicon modified polymer was added to the dispersion to obtain a mixture; the resulting mixture was mixed evenly with an organozirconium crosslinking agent to obtain a gel fracturing fluid.

[0027] According to the present invention, the above-mentioned gel fracturing fluid is used in reservoir stimulation, manufacturing artificial fracture networks, reservoir proppant carrying, creating oil flow channels, or enhancing oil recovery.

[0028] This invention prepares a high-temperature resistant polymer based on amide-bridged organosilicon modification, and through a four-fold reinforcement mechanism—"the high-temperature resistant polymer crosslinks with organozirconium to form a three-dimensional coordination crosslinking network, the hydrolysis and condensation of siloxane monomers in the polymer molecule to form a siloxane-reinforced network, the uniform dispersion of modified inorganic nanomaterials to form a nano-filled reinforced structure, and the hydrolysis and condensation of modified inorganic nanomaterials with siloxane monomers to form a reinforced network"—a multi-network reinforced gel fracturing fluid is prepared. The gel fracturing fluid of this invention does not crosslink at room temperature, possesses good fluidity, exhibits low friction in the wellbore during oilfield operations, gels underground after injection into the formation, and the resulting gel has high strength, withstands temperatures up to 220℃, has excellent proppant carrying capacity, is easily broken, and has low residue content, demonstrating good application performance in high-temperature reservoirs.

[0029] The technical features and beneficial effects of this invention are as follows:

[0030] 1. This invention uses acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one and 3-acrylamidopropyltrimethoxysilane as raw materials to prepare amide-bridged organosilicon modified polymers. Based on this, organozirconium crosslinking agents and modified inorganic nanomaterials are preferred to prepare multi-network reinforced gel fracturing fluids. All raw materials are widely available, easy to obtain, and have low application costs.

[0031] 2. This invention uses 5-methyl-3-vinyloxazolidine-2-one and 3-acrylamidopropyltrimethoxysilane as amide-bridged organosilicon-modified high-temperature resistant monomers. 5-methyl-3-vinyloxazolidine-2-one restricts the high-temperature movement of polymer chain segments through high-temperature resistant heterocyclic monomers. The Si-O bond has good high-temperature resistance, thus achieving good temperature resistance of polymer molecules under high-temperature conditions, and also has good shear resistance.

[0032] 3. This invention prepares amide-bridged organosilicon modified polymers by optimizing factors such as the mass fraction of synthesized monomers, the amount of different monomers added, the synthesis temperature, the reaction time, the reaction pH value, and the amount of initiator added through free radical polymerization. The preparation method is simple and conducive to industrial-scale production.

[0033] 4. This invention utilizes the hydrolysis properties of 3-acrylamidopropyltrimethoxysilane and modified nanomaterials to prepare a four-fold network reinforced gel fracturing fluid: a three-dimensional coordination crosslinking network formed by crosslinking high-temperature resistant polymers and organic zirconium; a siloxane-reinforced network formed by the hydrolysis and condensation of siloxane monomers in the polymer molecules; a nano-filled reinforced structure formed by the uniform dispersion of modified inorganic nanomaterials; and a reinforced network formed by the hydrolysis and condensation of modified inorganic nanomaterials and siloxane monomers. The resulting gel fracturing fluid exhibits significant high-temperature resistance and stable rheological properties.

[0034] 5. The amide-bridged organosilicon modified polymer prepared in this invention is crosslinked with an organozirconium crosslinking agent to form a multi-network reinforced gel fracturing fluid. It does not crosslink at room temperature, achieving low friction in the wellbore during fracturing operations. It crosslinks at high temperatures, achieving strong sand carrying capacity in high-temperature reservoir environments. The reservoir is easy to break, with low residue content and low reservoir damage, showing great potential for field application in oil fields. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 The infrared spectrum of the amide-bridged organosilicon-modified polymer prepared in Example 1.

[0037] Figure 2 The viscosity of the gel fracturing fluid prepared in Example 11 varies with temperature.

[0038] Figure 3 The viscosity and residue content of the breaker solution under different amounts of breaker in Experiment Example 1.

[0039] Figure 4 This is a static sand-carrying diagram of the gel fracturing fluid in Experiment Example 1. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The modified nano-SiO2 used in the examples and comparative examples was prepared according to the following method: (1) Add nano-SiO2 (particle size of 40-60nm) to anhydrous ethanol and disperse it evenly by ultrasonication to obtain a suspension; the mass ratio of nano-SiO2 to the volume of anhydrous ethanol is 1g:30mL. (2) Anhydrous ethanol and deionized water were mixed in a volume ratio of 2:1 to obtain an ethanol aqueous solution; the pH of the above ethanol aqueous solution was adjusted to 4.5 using acetic acid, and silane coupling agent KH550 was added. The solution was stirred at 300 rpm for 5 h at room temperature to obtain a hydrolysate; the mass ratio of silane coupling agent KH550 to the volume of ethanol aqueous solution was 1 g: 4.5 mL, and the mass ratio of silane coupling agent KH550 to nano SiO2 was 0.1:1. (3) Under stirring at 300 rpm, the hydrolysate obtained in step (2) was added dropwise to the suspension obtained in step (1) at a dropping rate of 2 drops / s. After the addition was completed, the mixture was reacted at 75°C for 6 hours. After the reaction was completed, the reaction solution was transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed 4 times with anhydrous ethanol by centrifugation. The washed precipitate was then vacuum dried at 70°C for 6 hours. After drying, the sample was taken out and ground with a mortar and pestle to obtain modified nano-SiO2. Meanwhile, the modified sepiolite nanofibers or modified attapulgite were prepared according to the preparation method of modified nano-SiO2, except that: sepiolite nanofibers (diameter of 50-80nm, aspect ratio of 150-200) or attapulgite (diameter of 40-60nm, length of 1-3μm) were used instead of nano-SiO2.

[0042] The organozirconium crosslinking agents used in the examples and comparative examples were prepared according to the following method: 2g of zirconium oxychloride was added to 10g of water and stirred at 200rpm for 10min to obtain an aqueous solution of zirconium oxychloride. The resulting aqueous solution of zirconium oxychloride was then placed in a round-bottom flask and preheated at 70℃ for 5min. 2g of lactic acid, 2g of glycerol and 4g of triethanolamine were added sequentially, with a time interval of 30min between each ligand addition. After the addition was complete, the pH of the system was adjusted to 7 with NaOH, and the reaction was carried out at 70℃ for 4h. After the reaction was completed, the mixture was naturally cooled to room temperature to obtain the organozirconium crosslinking agent.

[0043] Example 1 A method for preparing an amide-bridged organosilicon-modified polymer includes the following steps: Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and 5-methyl-3-vinyloxazolidine-2-one (CAS No.: 3395-98-0) were added to water. The pH of the system was adjusted to 6.5 using sodium hydroxide. Nitrogen gas was then purged for 30 min to remove oxygen. The mixture was heated to 50 °C, and then 3-acrylamidopropyltrimethoxysilane was added to the system to obtain a premix. Initiator 2,2'-azabis(2-imidazoline) dihydrochloride was added to the premix, and the mixture was reacted at 50 °C for 4 h under nitrogen protection. After the reaction was completed, the product was washed with ethanol and then vacuum dried at 55 °C for 24 h. After grinding, the amide-bridged organosilicon modified polymer was obtained. The total mass concentration of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane in the premix is ​​30 wt%. Based on a total mass of 100% for acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane, the mass percentages of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane are: 14%, 5%, 2%, and 1%, with the remainder being acrylamide. The initiator is 0.04% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane.

[0044] The infrared spectrum of the amide-bridged organosilicon-modified polymer prepared in this embodiment is as follows: Figure 1 As shown, 3435cm -1 The characteristic peak of NH / OH is at 1738 cm⁻¹. -1 The peak at 1654 cm⁻¹ is a characteristic peak for the C=O phase of 5-methyl-3-vinyloxazolidine-2-one. -1 The peak at 1552 cm⁻¹ is a characteristic peak for C=O in amides. -1 The amide group NH bending / CN stretching vibration and COO - The characteristic peak of asymmetric stretching vibration, 1182 cm⁻¹ -1 The peak at 1038 cm⁻¹ is a characteristic peak for S=O in 2-acrylamido-2-methylpropanesulfonic acid. -1 The peak at 950 cm⁻¹ is a characteristic Si-O-Si peak from the partial hydrolysis of 3-acrylamidopropyltrimethoxysilane. -1 The peak at this location is a characteristic Si-OH peak from the partial hydrolysis of 3-acrylamidopropyltrimethoxysilane, indicating that the above monomers have been successfully polymerized.

[0045] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 The viscosity of the resulting aqueous solution of the polymer was 79.23 mPa·s.

[0046] Example 2 Effect of 2-acrylamide-2-methylpropanesulfonic acid content on the viscosity of the synthesized polymer aqueous solution A method for preparing an amide-bridged organosilicon modified polymer is described in Example 1, except that the mass percentages of 2-acrylamide-2-methylpropanesulfonic acid in the monomers are 10%, 12%, 14%, 16%, and 18%, respectively.

[0047] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 When the mass percentages of 2-acrylamide-2-methylpropanesulfonic acid were 10%, 12%, 14%, 16%, and 18%, the viscosities of the aqueous solutions of the resulting polymers were 63.41 mPa·s, 69.34 mPa·s, 79.23 mPa·s, 74.82 mPa·s, and 64.78 mPa·s, respectively.

[0048] Example 3 Effect of acrylic acid content on the viscosity of synthetic polymer aqueous solution A method for preparing an amide-bridged organosilicon modified polymer is described in Example 1, except that the mass percentage of acrylic acid in the monomers is 1%, 2%, 3%, 4%, 5%, 6%, and 7%, respectively.

[0049] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 When the mass percentage of acrylic acid is 1%, 2%, 3%, 4%, 5%, 6%, and 7%, the viscosities of the resulting polymer aqueous solutions are 58.14 mPa·s, 63.82 mPa·s, 68.45 mPa·s, 76.89 mPa·s, 79.23 mPa·s, 74.11 mPa·s, and 68.94 mPa·s, respectively.

[0050] Example 4 Effect of 5-methyl-3-vinyloxazolidine-2-one content on the viscosity of the synthesized polymer aqueous solution A method for preparing an amide-bridged organosilicon modified polymer is described in Example 1, except that the mass percentages of 5-methyl-3-vinyloxazolidine-2-one in the monomers are 1%, 2%, 3%, and 4%, respectively.

[0051] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 When the mass percentages of 5-methyl-3-vinyloxazolidine-2-one were 1%, 2%, 3%, and 4%, the viscosities of the aqueous solutions of the resulting polymers were 72.71 mPa·s, 79.23 mPa·s, 78.05 mPa·s, and 73.88 mPa·s, respectively.

[0052] Example 5 Effect of 3-acrylamidopropyltrimethoxysilane content on the viscosity of the synthesized polymer aqueous solution A method for preparing an amide-bridged organosilicon modified polymer is described in Example 1, except that the mass percentages of 3-acrylamidopropyltrimethoxysilane in the monomers are 1%, 2%, 3%, and 4%, respectively.

[0053] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 When the mass percentages of 3-acrylamidopropyltrimethoxysilane were 1%, 2%, 3%, and 4%, the viscosities of the aqueous solutions of the resulting polymers were 79.23 mPa·s, 76.08 mPa·s, 70.42 mPa·s, and 67.14 mPa·s, respectively.

[0054] Example 6 Effect of monomer concentration on the viscosity of synthetic polymer aqueous solution A method for preparing an amide-bridged organosilicon modified polymer is described in Example 1, except that the total mass concentration (i.e., monomer concentration) of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane in the premix is ​​20wt%, 25wt%, 30wt%, 35wt%, and 40wt%, respectively.

[0055] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1When the monomer concentrations were 20wt%, 25wt%, 30wt%, 35wt%, and 40wt%, the viscosities of the resulting polymer aqueous solutions were 46.14 mPa·s, 67.45 mPa·s, 79.23 mPa·s, 77.61 mPa·s, and 57.69 mPa·s, respectively.

[0056] Example 7 Effect of initiator dosage on the viscosity of synthetic polymer aqueous solution A method for preparing an amide-bridged organosilicon modified polymer is described in Example 1, except that the initiator is in the following proportions: 0.02%, 0.03%, 0.04%, 0.05%, and 0.06% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane, respectively.

[0057] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 When the initiators were 0.02%, 0.03%, 0.04%, 0.05%, and 0.06% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane, respectively, the viscosities of the aqueous solutions of the resulting polymers were 51.22 mPa·s, 66.32 mPa·s, 79.23 mPa·s, 75.54 mPa·s, and 62.42 mPa·s, respectively.

[0058] Example 8 Effect of reaction pH on the viscosity of the synthesized polymer aqueous solution A method for preparing an amide-bridged organosilicon modified polymer is described in Example 1, except that the pH values ​​of the system are adjusted to 5.5, 6.0, 6.5, 7.0, and 7.5, respectively.

[0059] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 When the reaction pH values ​​were 5.5, 6.0, 6.5, 7.0, and 7.5, the viscosities of the resulting polymer aqueous solutions were 53.74 mPa·s, 72.46 mPa·s, 79.23 mPa·s, 65.19 mPa·s, and 61.36 mPa·s, respectively.

[0060] Example 9 Effect of reaction temperature on the viscosity of the synthesized polymer aqueous solution A method for preparing an amide-bridged organosilicon modified polymer is described in Example 1, except that the reaction temperatures are 35°C, 40°C, 45°C, 50°C, 55°C, and 60°C.

[0061] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 When the reaction temperatures were 35℃, 40℃, 45℃, 50℃, 55℃, and 60℃, the viscosities of the resulting polymer aqueous solutions were 44.42 mPa·s, 51.41 mPa·s, 66.24 mPa·s, 79.23 mPa·s, 76.98 mPa·s, and 60.18 mPa·s, respectively.

[0062] Example 10 Effect of reaction time on the viscosity of the synthesized polymer aqueous solution A method for preparing an amide-bridged organosilicon modified polymer is described in Example 1, except that the reaction times are 2h, 3h, 4h, 5h, 6h, and 7h.

[0063] The viscosity of a 0.6% (w / w) aqueous solution of the above-mentioned amide-bridged organosilicon modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 When the reaction temperatures were 2h, 3h, 4h, 5h, 6h, and 7h, the viscosities of the resulting polymer aqueous solutions were 63.78mPa·s, 72.58mPa·s, 79.23mPa·s, 79.21mPa·s, 79.04mPa·s, and 78.41mPa·s, respectively.

[0064] Example 11 A gel fracturing fluid comprises the following raw materials in weight percentages: 0.04% modified nano-SiO2, 0.6% amide-bridged organosilicon modified polymer prepared in Example 1, 0.6% organozirconium crosslinking agent, and the balance being water; that is, the mass ratio of amide-bridged organosilicon modified polymer to organozirconium crosslinking agent is 1:1.

[0065] The preparation method of the above-mentioned gel fracturing fluid includes the following steps: Modified nano-SiO2 was dispersed in water to obtain a dispersion; the amide-bridged organosilicon modified polymer prepared in Example 1 was added to the dispersion to obtain a mixture; the resulting mixture was mixed evenly with an organozirconium crosslinking agent to obtain a gel fracturing fluid.

[0066] The above-mentioned gel fracturing fluid was loaded into the rotating drum of a temperature and pressure resistant MARS 60 rheometer, and nitrogen was introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program was set as follows: constant temperature rise from 25 to 220℃ at a rate of 3℃ / min, constant temperature at 220℃ for 7200 s, and shear rate of 100 s. -1 The retention viscosity of the obtained gel fracturing fluid was measured to be 92.46 mPa·s.

[0067] Figure 2 The figure shows the viscosity of the gel fracturing fluid prepared in this embodiment as a function of temperature. It can be seen that the viscosity of the gel fracturing fluid generally shows a trend of first increasing and then decreasing. In the initial heating stage, the viscosity of the gel fracturing fluid is low, and then gradually increases, exhibiting a delayed cross-linking phenomenon. As the temperature continues to rise, the gel network structure is destroyed under high temperature and shear stress, and the viscosity gradually decreases. Under the quadruple network reinforcement effect of "high-temperature resistant polymer-organic zirconium cross-linking, hydrolysis of siloxane monomers in polymer molecules, uniform dispersion and filling of nano-silica, and hydrolysis of nano-silica-siloxane monomers," the gel retains a high viscosity. Overall, the gel exhibits excellent high-temperature resistance and shear resistance.

[0068] Example 12 Effect of crosslinking ratio on the temperature and shear resistance of gel fracturing fluid A gel fracturing fluid as described in Example 11, except that the mass percentage of the organozirconium crosslinking agent is 0.3%, 0.45%, 0.6%, 0.75%, 0.9%, 1.05%, and 1.2%, respectively, that is, the mass ratio (crosslinking ratio) of the amide-bridged organosilicon modified polymer to the organozirconium crosslinking agent is controlled to be 1:0.5, 1:0.75, 1:1, 1:1.25, 1:1.5, 1:1.75, and 1:2, respectively.

[0069] The above-mentioned gel fracturing fluid was loaded into the rotating drum of a temperature and pressure resistant MARS 60 rheometer, and nitrogen was introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program was set as follows: constant temperature rise from 25 to 220℃ at a rate of 3℃ / min, constant temperature at 220℃ for 7200 s, and shear rate of 100 s. -1 The retention viscosities of the gel fracturing fluids obtained with crosslinking ratios of 1:0.5, 1:0.75, 1:1, 1:1.25, 1:1.5, 1:1.75, and 1:2 were 53.14 mPa·s, 67.46 mPa·s, 92.46 mPa·s, 90.34 mPa·s, 85.69 mPa·s, 74.36 mPa·s, and 65.71 mPa·s, respectively.

[0070] The retention viscosity of the above-mentioned gel fracturing fluids all meet the industry standard requirements (retention viscosity > 50 mPa·s).

[0071] Example 13 Effect of amide-bridged organosilicon modified polymer concentration on the temperature and shear resistance of gel fracturing fluid A gel fracturing fluid as described in Example 11, except that the mass percentages of the amide-bridged organosilicon modified polymer are 0.5%, 0.6%, 0.7%, 0.8%, and 0.9%, respectively, and the corresponding mass percentages of the organozirconium crosslinker are 0.5%, 0.6%, 0.7%, 0.8%, and 0.9%, respectively, thus ensuring that the mass ratio of the amide-bridged organosilicon modified polymer to the organozirconium crosslinker in the gel fracturing fluid is 1:1.

[0072] The above-mentioned gel fracturing fluid was loaded into the rotating drum of a temperature and pressure resistant MARS 60 rheometer, and nitrogen was introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program was set as follows: constant temperature rise from 25 to 220℃ at a rate of 3℃ / min, constant temperature at 220℃ for 7200 s, and shear rate of 100 s. -1 The retention viscosities of the gel fracturing fluids obtained when the mass percentages of the amide-bridged organosilicon modified polymer were 0.5%, 0.6%, 0.7%, 0.8%, and 0.9% were 58.10 mPa·s, 92.46 mPa·s, 104.74 mPa·s, 118.92 mPa·s, and 127.96 mPa·s, respectively.

[0073] The retention viscosity of the above-mentioned gel fracturing fluids all meet the industry standard requirements (retention viscosity > 50 mPa·s).

[0074] Example 14 Effect of modified nano-SiO2 concentration on the temperature and shear resistance of gel fracturing fluid A gel fracturing fluid as described in Example 11, except that the mass percentage of modified nano-SiO2 is 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, and 0.07%, respectively.

[0075] The above-mentioned gel fracturing fluid was loaded into the rotating drum of a temperature and pressure resistant MARS 60 rheometer, and nitrogen was introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program was set as follows: constant temperature rise from 25 to 220℃ at a rate of 3℃ / min, constant temperature at 220℃ for 7200 s, and shear rate of 100 s. -1 The retained viscosities of the gel fracturing fluids obtained when the mass percentage of modified nano-SiO2 was 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, and 0.07% were 53.87 mPa·s, 69.42 mPa·s, 92.46 mPa·s, 88.04 mPa·s, 82.37 mPa·s, and 74.83 mPa·s, respectively.

[0076] The retention viscosity of the above-mentioned gel fracturing fluids all meet the industry standard requirements (retention viscosity > 50 mPa·s).

[0077] This invention enhances the high-temperature resistance of polymers by using amide-bridged organosilicon-modified high-temperature resistant monomers, achieving excellent shear resistance under high-temperature conditions. The high-temperature resistant polymer is obtained through free radical copolymerization with acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and 5-methyl-3-vinyloxazolidine-2-one. The preparation method is simple, and the product exhibits stable performance. Based on the four-fold network reinforcement concept of "high-temperature resistant polymer crosslinking with organozirconium to form a three-dimensional coordination crosslinking network, hydrolysis and condensation of siloxane monomers in the polymer molecule to form a siloxane-reinforced network, uniform dispersion of modified inorganic nanomaterials to form a nano-filled reinforced structure, and hydrolysis and condensation of modified inorganic nanomaterials with siloxane monomers to form a reinforced network," a high-temperature resistant gel fracturing fluid is prepared. This gel fracturing fluid exhibits strong proppant carrying capacity in high-temperature reservoir environments, easy reservoir breakage, low residue content, and minimal reservoir damage, demonstrating significant potential for field application in oilfields.

[0078] Example 15 The Influence of Modified Nanomaterials on the Temperature and Shear Resistance of Gel Fracturing Fluids A gel fracturing fluid as described in Example 11, except that modified SiO2 is replaced with modified sepiolite nanofibers or modified attapulgite.

[0079] The above-mentioned gel fracturing fluid was loaded into the rotating drum of a temperature and pressure resistant MARS 60 rheometer, and nitrogen was introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program was set as follows: constant temperature rise from 25 to 220℃ at a rate of 3℃ / min, constant temperature at 220℃ for 7200 s, and shear rate of 100 s. -1 The residual viscosities of the gel fracturing fluids obtained when the modified nanomaterials were modified sepiolite nanofibers and modified attapulgite were measured to be 90.19 mPa·s and 88.67 mPa·s, respectively.

[0080] Comparative Example 1 The effect of 3-acrylamidopropyltrimethoxysilane monomer on the properties of polymers and gel fracturing fluids A method for preparing a modified polymer is described in Example 1, except that the monomer does not contain 3-acrylamidopropyltrimethoxysilane, and the mass percentage of acrylamide is 81%. The viscosity of a 0.6% (w / w) aqueous solution of the modified polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s. -1 The viscosity is 62.17 mPa·s.

[0081] A gel fracturing fluid is described in Example 11, except that the amide-bridged organosilicon modified polymer prepared in Example 1 is replaced with the modified polymer prepared in this comparative example. The above gel fracturing fluid is loaded into the rotating drum of a temperature- and pressure-resistant MARS 60 rheometer, and nitrogen is introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program is set as follows: constant temperature rise from 25 to 220°C at a rate of 3°C / min, constant temperature at 220°C for 7200 s, and shear rate of 100 s. -1 The retention viscosity of the gel fracturing fluid was measured to be only 31.60 mPa·s.

[0082] Therefore, the addition of trace amounts of 3-acrylamidopropyltrimethoxysilane has a significant impact on the performance of both the polymer and the gel fracturing fluid. For polymer aqueous solutions, partial hydrolysis of 3-acrylamidopropyltrimethoxysilane can form a three-dimensional network structure, increasing the stability of the polymer aqueous solution. For gel fracturing fluids, modified polymers without 3-acrylamidopropyltrimethoxysilane monomers crosslink with organozirconium crosslinking agents only form a "polymer-organozirconium crosslinking" network structure, while the uniformly dispersed modified nano-SiO2 fills the crosslinking network. However, polymers containing 3-acrylamidopropyltrimethoxysilane monomers, along with organozirconium crosslinking agents and modified nano-SiO2, can form a quadruple network reinforcement effect: "high-temperature resistant polymer-organozirconium crosslinking, hydrolysis of siloxane monomers in the polymer molecule, uniform dispersion and filling of nano-SiO2, and nano-SiO2-siloxane monomer hydrolysis," further improving the high-temperature resistance and shear resistance of the gel fracturing fluid.

[0083] Comparative Example 2 Effects of 3-acrylamidopropyltrimethoxysilane and modified nano-SiO2 on the properties of gel fracturing fluid A gel fracturing fluid as described in Example 11, except that the modified nano-SiO2 content is 0 wt%, and the amide-bridged organosilicon modified polymer prepared in Example 1 is replaced with the modified thermopolymer prepared in Comparative Example 1. The above gel fracturing fluid is loaded into the rotating drum of a temperature- and pressure-resistant MARS 60 rheometer, and nitrogen is introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program is set as follows: constant temperature rise from 25 to 220°C at a rate of 3°C / min, constant temperature at 220°C for 7200 s, and shear rate of 100 s. -1 The retention viscosity of the gel fracturing fluid was measured to be only 25.13 mPa·s.

[0084] As shown in Comparative Examples 1, 2, and 11, the addition of modified nano-SiO2 has little effect on improving the performance of gel fracturing fluid in the absence of 3-acrylamidopropyltrimethoxysilane monomer. The polymer and organozirconium crosslinking agent can form a crosslinked network structure, while nano-silica only acts as a physical filler. Under high-temperature conditions, the viscosity of the gel fracturing fluid decreases sharply, resulting in poor high-temperature resistance and shear resistance.

[0085] Comparative Example 3 Effect of modified nano-SiO2 on the properties of gel fracturing fluid A gel fracturing fluid as described in Example 11, except that modified nano-SiO2 is not added; the above gel fracturing fluid is loaded into the rotating drum of a temperature and pressure resistant MARS 60 rheometer, and nitrogen is introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program is set as follows: constant temperature rise from 25 to 220°C at a rate of 3°C / min, constant temperature at 220°C for 7200 s, and shear rate of 100 s. -1 The viscosity of the gel fracturing fluid was measured to be 52.89 mPa·s.

[0086] As shown in Comparative Example 3 and Example 11, the modified nano-SiO2 significantly improves the performance of the gel fracturing fluid when containing 3-acrylamidopropyltrimethoxysilane monomer. The amide-bridged organosilicon-modified polymer and organozirconium crosslinker only form a dual-reinforced network structure of "high-temperature resistant polymer-organozirconium crosslinker crosslinking and hydrolysis of siloxane monomers in the polymer molecule." Under high-temperature conditions, the gel fracturing fluid only meets industry standards and is insufficient to cope with even higher temperatures (above 220°C).

[0087] Comparative Example 4 The effect of organozirconium crosslinking agents on the properties of gel fracturing fluids A gel fracturing fluid as described in Example 11, except that no organozirconium crosslinking agent is added; the fracturing fluid is loaded into the rotating drum of a temperature and pressure resistant MARS 60 rheometer, and nitrogen is introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program is set as follows: constant temperature rise from 25 to 220°C at a rate of 3°C / min, constant temperature at 220°C for 7200 s, and shear rate of 100 s. -1 The retention viscosity of the fracturing fluid was measured to be only 22.19 mPa·s.

[0088] As can be seen from Comparative Example 4 and Example 11, the organozirconium crosslinking agent has a significant impact on the performance of the gel fracturing fluid. Although the viscosity of the polymer solution can reach 79.23 mPa·s at room temperature, the viscosity drops sharply at high temperature. Without the organozirconium crosslinking agent, the crosslinking network structure formed solely by the interaction between polymer molecules, the hydrolysis of siloxane monomers, and the hydrolysis of siloxane monomers and nano-silica cannot adapt to the high-temperature reservoir environment.

[0089] Comparative Example 5 A polymer, an acrylamide polymer (nonionic polyacrylamide polymer, molecular weight 7 million), was used. The viscosity of a 0.6% (w / w) aqueous solution of the above polymer was measured using a MARS 60 rheometer at a test temperature of 25°C and a shear rate of 170 s⁻¹. -1 At that time, the viscosity was 54.77 mPa·s.

[0090] A gel fracturing fluid is described in Example 11, except that the amide-bridged organosilicon modified polymer prepared in Example 1 is replaced with the acrylamide polymer of this comparative example; the fracturing fluid is loaded into the drum of a temperature- and pressure-resistant MARS 60 rheometer, and nitrogen is introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program is set as follows: constant temperature rise from 25 to 220°C at a rate of 3°C / min, constant temperature at 220°C for 7200 s, and shear rate of 100 s. -1 The measured residual viscosity of the fracturing fluid was only 40.18 mPa·s.

[0091] As can be seen from Comparative Example 5 and Example 11, the amide-bridged organosilicon modified polymer and the gel fracturing fluid of the present invention have better performance. The commercial polymer and organozirconium crosslinking agent only form a "polymer-organozirconium crosslinking" network structure. At the same time, the uniform dispersion of nano-silica plays a role in filling the crosslinking network of the gel fracturing fluid, resulting in poor high-temperature resistance and shear resistance.

[0092] Comparative Example 6 A method for preparing a modified polymer is described in Example 1, except that 3-acrylamidopropyltrimethoxysilane is replaced with 3-acrylamidopropyltriethoxysilane and vinyltriacetoxysilane, respectively.

[0093] A gel fracturing fluid was described in Example 11, except that the amide-bridged organosilicon modified polymer prepared in Example 1 was replaced with the modified polymer of this comparative example. The fracturing fluid was loaded into the drum of a temperature- and pressure-resistant MARS 60 rheometer, and nitrogen was introduced to maintain a pressure of 2.75 MPa. The MARS 60 rheometer program was set as follows: constant temperature increase from 25 to 220°C at a rate of 3°C / min, constant temperature at 220°C for 7200 s, and shear rate of 100 s. -1 The measured retention viscosities of the fracturing fluid were 43.27 mPa·s and 37.64 mPa·s, respectively.

[0094] This shows that the type of siloxane monomer affects the strength of the gel. Replacing 3-acrylamidopropyltriethoxysilane with other siloxane monomers results in fracturing fluids with poor temperature and shear resistance.

[0095] Experimental Example 1 The following tests were performed on the gel fracturing fluid prepared in Example 11:

[0096] Test 1: Study on the gel breaking performance of gel fracturing fluid Ammonium persulfate was selected as the breaker. The effect of ammonium persulfate dosage (0.05%, 0.1%, 0.2%, 0.3%, and 0.4% of the mass of the gel fracturing fluid) on the degree of gel breaking and the viscosity of the breaker fluid was studied by adjusting the dosage of ammonium persulfate (0.05%, 0.1%, 0.2%, 0.3%, and 0.4% of the mass of the gel fracturing fluid, respectively). The operation procedure was in accordance with the industry standard SY / T 7627-2021.

[0097] like Figure 3 As shown, without the addition of a breaker, the viscosity of the breaker fluid was 12.44 mPa·s, and the residue content was 371.21 mg / L, both of which did not meet the industry standard (viscosity ≤ 5 mPa·s, residue content ≤ 200 mg / L). After adding 0.05% ammonium persulfate, the viscosity of the breaker fluid was 4.31 mPa·s, and the residue content was 124.84 mg / L, meeting the industry standard requirements. Furthermore, with the increase of the breaker content, both the viscosity and residue content of the breaker fluid showed a gradual decreasing trend. Therefore, it can be seen that introducing 3-acrylamidopropyltrimethoxysilane and 5-methyl-3-vinyloxazolidine-2-one into the polymer, and introducing trace amounts of modified nano-SiO2 into the gel fracturing fluid, does not affect the breaker performance of the gel fracturing fluid, but significantly improves its temperature and shear resistance, bringing beneficial effects.

[0098] Test 2: Study on the proppant carrying capacity of gel fracturing fluid The static proppant carrying capacity was used to characterize the suspension stability of the gel fracturing fluid on the proppant under static or low flow rate conditions. The gel fracturing fluid and proppant were mixed evenly at room temperature and then placed in a 100 mL graduated cylinder. Figure 4 The images show the initial phase (0h) of the gelled fracturing fluid after gel formation and the static proppant transport phase after 2 hours in a 95℃ constant temperature chamber (industry standard requirement: 220℃ reservoir temperature, placed in a 95℃ constant temperature chamber for 2 hours). Ceramsite proppant was selected, with a mesh size of 30-50 and a sand ratio of 20%. It is evident that the gelled fracturing fluid system effectively inhibits proppant sedimentation under static conditions, facilitating stable proppant transport and thus improving proppant transport and production enhancement in the field.

[0099] Test 3: Reservoir Damage Performance of Gel Fracturing Fluid Following the experimental method of industry standard SY / T5107-2016, the effect of gel fracturing fluid breaking on reservoir permeability was tested. Cores with initial permeability of 0.61 mD, 1.24 mD, and 5.32 mD were selected. After injecting gel-breaking fluid (obtained by mixing gel fracturing fluid and ammonium persulfate at 95℃ for 2 hours, with the mass of ammonium persulfate being 0.1% of the mass of gel fracturing fluid) into the cores, the core permeability was measured again to be 0.52 mD, 1.12 mD, and 5.04 mD, with core damage rates of 14.75%, 9.68%, and 5.26%, respectively, all meeting the industry standard reservoir damage rate <30%.

[0100] Therefore, it can be seen that the gel fracturing fluid of the present invention has a low reservoir damage rate and does not damage the oil and gas flow channels.

[0101] In summary, this invention preferably uses industrially produced acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane as raw materials to prepare amide-bridged organosilicon modified polymers. Based on this, an organozirconium crosslinking agent and modified inorganic nanomaterials are preferred to prepare a four-fold network reinforced gel fracturing fluid: a three-dimensional coordination crosslinking network formed by the crosslinking of high-temperature resistant polymers and organozirconium; a siloxane-reinforced network formed by the hydrolysis and condensation of siloxane monomers in the polymer molecule; a nano-filled reinforced structure formed by the uniform dispersion of modified inorganic nanomaterials; and a reinforced network formed by the hydrolysis and condensation of modified inorganic nanomaterials and siloxane monomers. This results in a gel fracturing fluid with excellent temperature and shear resistance, strong proppant carrying capacity in high-temperature reservoir environments, easy gel breaking in the reservoir, low residue content, and low reservoir damage. It has great potential for field application in oilfields and can be widely used in high-temperature reservoir environments (220℃), showing significant potential for application in deep and ultra-deep oil and gas fracturing operations.

[0102] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an amide-bridged organosilicon-modified polymer, characterized in that, The steps include the following: Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and 5-methyl-3-vinyloxazolidine-2-one were added to water, and the pH of the system was adjusted to 5.5-7.

5. After purging with nitrogen to remove oxygen, the mixture was heated to the reaction temperature, and then 3-acrylamidopropyltrimethoxysilane was added to obtain a premix. An initiator was added to the premix to carry out the reaction. After the reaction was completed, the mixture was washed, dried, and ground to obtain an amide-bridged organosilicon modified polymer. Based on the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane as 100%, the mass percentage of 2-acrylamido-2-methylpropanesulfonic acid is 10-18%, the mass percentage of acrylic acid is 1-7%, the mass percentage of 5-methyl-3-vinyloxazolidine-2-one is 1-4%, the mass percentage of 3-acrylamidopropyltrimethoxysilane is 1-4%, and the balance is acrylamide; the premixed solution contains acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl- The total mass concentration of 3-vinyloxazolidine-2-one and 3-acrylamidopropyltrimethoxysilane is 20-40 wt%; the initiator is 2,2'-azabis(2-imidazoline) dihydrochloride, 2,2'-azobisisobutylamidine dihydrochloride, or 4,4'-azobis(4-cyanopentanoic acid), and the mass of the initiator is 0.02-0.06% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane; the reaction temperature is 35-60℃, and the reaction time is 2-7 h.

2. The method for preparing the amide-bridged organosilicon-modified polymer according to claim 1, characterized in that, Based on the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane as 100%, the mass percentage of 2-acrylamido-2-methylpropanesulfonic acid is 12-16%, the mass percentage of acrylic acid is 4-6%, the mass percentage of 5-methyl-3-vinyloxazolidine-2-one is 2-3%, the mass percentage of 3-acrylamidopropyltrimethoxysilane is 1-2%, and the balance is acrylamide.

3. The method for preparing the amide-bridged organosilicon-modified polymer according to claim 1, characterized in that, The pH of the system was adjusted to 5.5-7.5 using sodium hydroxide; nitrogen was purged for 20-40 minutes to remove oxygen. The total mass concentration of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane in the premix is ​​25-35 wt%; the mass of the initiator is 0.03-0.05% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, 5-methyl-3-vinyloxazolidine-2-one, and 3-acrylamidopropyltrimethoxysilane. The reaction temperature is 45-55℃; the reaction time is 4-6h; the reaction is carried out under nitrogen protection; the washing is performed using ethanol; and the drying is performed under vacuum at 55-65℃ for 24-48h.

4. An amide-bridged organosilicon-modified polymer, characterized in that, It is prepared by the preparation method described in any one of claims 1-3.

5. A gel fracturing fluid, characterized in that, The raw materials comprise the following percentages by mass: 0.02-0.07% modified inorganic nanomaterials, 0.5-0.9% of the amide-bridged organosilicon modified polymer as described in claim 4, 0.3-1.2% organozirconium crosslinking agent, and the balance being water; wherein the mass ratio of organozirconium crosslinking agent to amide-bridged organosilicon modified polymer is 0.5-2:1; the modified inorganic nanomaterials are obtained by modifying inorganic nanomaterials with a silane coupling agent.

6. The gel fracturing fluid according to claim 5, characterized in that, The gel fracturing fluid comprises the following raw materials in the following mass percentages: 0.04-0.06% modified inorganic nanomaterials, 0.6-0.8% amide-bridged organosilicon modified polymer as described in claim 4, 0.6-1.2% organozirconium crosslinking agent, and the balance being water; and the mass ratio of organozirconium crosslinking agent to amide-bridged organosilicon modified polymer is 1-1.5:

1.

7. The gel fracturing fluid according to claim 5, characterized in that, The inorganic nanomaterial is one or more of nano-SiO2, sepiolite nanofibers, and attapulgite; the silane coupling agent is γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane, and the mass ratio of the silane coupling agent to the inorganic nanomaterial is 0.01-0.2:1; the particle size of the nano-SiO2 is 40-60 nm; the diameter of the sepiolite nanofibers is 10-100 nm, and the aspect ratio is 10-300; the diameter of the attapulgite is 10-80 nm, and the length is 0.5-5 μm. The modified inorganic nanomaterials were prepared according to the following method: (1) Add inorganic nanomaterials to anhydrous ethanol and disperse them evenly by ultrasonication to obtain a suspension; the mass ratio of the inorganic nanomaterials to the volume of anhydrous ethanol is 1g:20-40mL. (2) Adjust the pH of the ethanol aqueous solution to 4-5, add silane coupling agent for hydrolysis to obtain hydrolysate; the volume ratio of ethanol to water in the ethanol aqueous solution is 1-3:1; adjust the pH of the ethanol aqueous solution to 4-5 using acetic acid; the mass ratio of the silane coupling agent to the volume of the ethanol aqueous solution is 1g:3-6mL; the hydrolysis time is 4-6h, and the hydrolysis temperature is room temperature; (3) Under stirring conditions, the hydrolysate obtained in step (2) is added dropwise to the suspension obtained in step (1) to carry out the reaction; after the reaction is completed, the modified inorganic nanomaterial is obtained by centrifugation, washing, drying and grinding; the drop acceleration rate of the hydrolysate is 1-2 drops / s; the reaction temperature is 70-80℃ and the reaction time is 5-7h; the washing is centrifugation washing with anhydrous ethanol 3-5 times; the drying is vacuum drying at 60-70℃ for 6-10 hours.

8. The gel fracturing fluid according to claim 5 or 6, characterized in that, The organozirconium crosslinking agent is prepared by reacting an organic ligand with an aqueous solution of zirconium oxychloride; the organic ligand is one or more of lactic acid, citric acid, triethanolamine, diethanolamine, glycerol, mannitol, and sorbitol; the mass ratio of zirconium oxychloride to water in the aqueous solution of zirconium oxychloride is 1-3:10; the mass ratio of the organic ligand to the aqueous solution of zirconium oxychloride is 3-5:

1. The organozirconium crosslinking agent was prepared according to the following method: After preheating the zirconium oxychloride aqueous solution, an organic ligand is added to it; then, the pH of the system is adjusted to 7 using NaOH, and the reaction is carried out. After cooling, an organozirconium crosslinking agent is obtained; the preheating is carried out at 70-80℃ for 5-10 min, and the reaction is carried out at 70-80℃ for 3-5 h.

9. A method for preparing the gel fracturing fluid according to any one of claims 5-8, characterized in that, The steps include the following: The modified inorganic nanomaterials are dispersed in water to obtain a dispersion; the amide-bridged organosilicon modified polymer of claim 4 is added to the dispersion to obtain a mixture; the resulting mixture is mixed evenly with an organozirconium crosslinking agent to obtain a gel fracturing fluid.

10. The application of the gel fracturing fluid according to any one of claims 5-8 in reservoir stimulation, fabrication of artificial fracture networks, reservoir proppant carrying, creation of oil flow channels, or enhancement of oil recovery.

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