High-temperature-resistant fracturing fluid thickening agent, preparation method and application thereof

Abstract

This invention belongs to the field of petroleum extraction technology and discloses a high-temperature resistant fracturing fluid thickener, its preparation method, and its application. The raw materials for preparing the high-temperature resistant fracturing fluid thickener include acrylamide, acrylic acid, sodium p-styrene sulfonate, cationic monomer, initiator, chain transfer agent, oxidant, reducing agent, and deionized water. The high-temperature resistant fracturing fluid thickener provided by this invention, together with the covalent crosslinking agent, can be formulated to obtain a fracturing fluid that is temperature-resistant, salt-resistant, and shear-resistant. This can significantly improve the stability and proppant-carrying capacity of polymers under high temperature and high salinity conditions, which is beneficial for improving the fracturing stimulation effect of unconventional reservoirs with high temperature and high salinity.

Description

Technical Field

[0001] This invention relates to the field of petroleum extraction technology, specifically to a high-temperature resistant fracturing fluid thickener, its preparation method and application, and a fracturing fluid, its preparation method and application. Background Technology

[0002] In the contemporary energy sector, with the increasing depletion of shallow and easily exploitable oil and gas resources, global energy exploration has turned its attention to more complex and deep geological formations. High-temperature oil and gas reservoirs, with their unique characteristics and enormous potential, have become a new focus. The temperatures of these formations generally exceed 180°C, with some even reaching over 200°C. Such extremely high temperatures pose unprecedented challenges to existing extraction technologies and equipment. High-temperature oil and gas reservoirs are mainly distributed in deep crustal structures. Due to their special geological formation, they are typically accompanied by high-intensity pressure and complex lithological characteristics, such as crystalline matrix structures and organic-rich sediments. These reservoirs contain abundant hydrocarbons, but their extreme environments make extraction exceptionally difficult and risky. High temperatures not only lead to rapid wear and tear on drilling tools and equipment but also trigger a series of problems such as wellbore collapse, deterioration of drilling fluid performance, and abnormal expansion of formation fluids, increasing the uncertainty and cost of construction.

[0003] In many difficult-to-exploit oil and gas reservoirs, fracturing technology, as a revolutionary production enhancement measure, is increasingly widely used. Especially in oil and gas wells with low initial production, precise fracturing can significantly increase oil and gas production, thereby maximizing economic benefits. The implementation of this technology not only overcomes the challenges faced by traditional extraction methods but also creates new growth opportunities for the energy industry. As the core medium in hydraulic fracturing operations, the performance of fracturing fluid directly affects the success of the fracturing operation. High-quality fracturing fluid should not only effectively transmit pressure and achieve efficient formation fracturing but also possess good rheological properties, shear stability, and proppant carrying capacity to ensure smooth operation and stable recovery of reservoir production in the later stages.

[0004] Traditional fracturing fluid formulations struggle to maintain stable performance under such extreme conditions. Decreased rheological properties, shear stability, and proppant-carrying capacity limit the efficiency of deep oil and gas resource extraction. To address this technical hurdle, research teams and the energy industry are accelerating the innovation of new fracturing fluid systems, particularly focusing on developing fracturing fluid products with superior high-temperature stability and excellent shear tolerance. Through optimized formulation design, stability and proppant-carrying capacity under high-temperature environments are improved, while reservoir damage is reduced and formation compatibility is maintained, thereby enabling the effective development and efficient utilization of deep oil and gas resources.

[0005] However, the existing high-temperature polymer thickeners have complex preparation processes and high costs, and their performance is insufficient to meet the construction requirements in unconventional reservoirs with high temperature and salinity in deep wells. Therefore, for the development of unconventional reservoirs with high temperature and salinity in deep wells, innovative fracturing fluid thickener technology has become crucial to ensuring the effective development of this resource. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the preparation process of the high-temperature resistant polymer thickeners used in the prior art is complicated, the polymer thickening effect is not good in unconventional oil reservoirs with high temperature and high salinity in deep wells, and the energy consumption is high and the cost is high, making it unsuitable for large-scale industrial production. The present invention provides a high-temperature resistant fracturing fluid thickener, its preparation method and application, as well as a fracturing fluid, its preparation method and application, which is particularly suitable for polymer fracturing fluid technology in deep well high temperature and high salinity oil reservoir environments.

[0007] To address the aforementioned technical problems, the first aspect of this invention provides a high-temperature resistant fracturing fluid thickener. The raw materials for preparing the high-temperature resistant fracturing fluid thickener include acrylamide, acrylic acid, sodium p-styrene sulfonate, cationic monomer, initiator, chain transfer agent, oxidant, reducing agent, and deionized water. The weight proportions of each component in the raw materials for preparing the high-temperature resistant fracturing fluid thickener are as follows:

[0008]

[0009]

[0010] According to some embodiments of the present invention, the cationic monomer is selected from at least one of methacryloyloxyethyl dimethyl benzyl ammonium chloride (MBDAC), acryloyloxyethyl dimethyl benzyl ammonium chloride (AODBAC), and 2-acrylamido-2-methylpropyltrimethylammonium chloride (AMPTAC).

[0011] According to some embodiments of the present invention, the initiator is selected from azo initiators; preferably, the azo initiator is selected from azobisisobutyrazoline hydrochloride (VO44) and / or azobisisobutyramidine hydrochloride (V50).

[0012] According to some embodiments of the present invention, the chain transfer agent is selected from at least one of sodium hypophosphite, sodium formate (CH3COONa), and isopropanol.

[0013] According to some embodiments of the present invention, the oxidant is selected from at least one of ammonium persulfate, potassium peroxymonosulfate, and sodium persulfate;

[0014] And / or, the reducing agent is selected from sodium metabisulfite and / or ferrous ammonium sulfate.

[0015] A second aspect of the present invention provides a method for preparing the high-temperature resistant fracturing fluid thickener provided in the first aspect, comprising the following steps:

[0016] (1) Mix the acrylamide, acrylic acid, sodium p-styrene sulfonate, cationic monomer and deionized water in the specified weight parts to obtain a reaction solution;

[0017] (2) Under an inactive atmosphere, the initiator, chain transfer agent, oxidant and reducing agent in the specified weight parts are added to the reaction solution to obtain the high-temperature fracturing fluid thickener.

[0018] According to some embodiments of the present invention, in step (1), the pH of the reaction solution is adjusted to 5-7 using a pH adjuster; preferably, the pH adjuster is selected from a sodium hydroxide solution with a mass fraction of 20%-40% or a sodium bicarbonate solution with a mass fraction of 20%-40%.

[0019] And / or, in step (1), the temperature of the reaction solution is 0℃~5℃;

[0020] And / or, in step (2), the inactive atmosphere is selected from nitrogen and / or argon;

[0021] And / or, in step (2), the reaction conditions include: a time of 3 to 4 hours;

[0022] And / or, in step (2), the high-temperature fracturing fluid thickener further includes crushing, drying and pulverizing treatment; preferably, the drying conditions include: temperature of 70℃~100℃; time of 3 hours~5 hours; the particle size of the pulverized high-temperature fracturing fluid thickener is 80 mesh~120 mesh.

[0023] A third aspect of the present invention provides a fracturing fluid comprising the high-temperature resistant fracturing fluid thickener provided in the first aspect or the high-temperature resistant fracturing fluid thickener prepared by the preparation method provided in the second aspect.

[0024] A fourth aspect of the present invention provides a method for preparing the fracturing fluid provided in the third aspect above, comprising adding the covalent crosslinking agent to an aqueous solution of the high-temperature resistant fracturing fluid thickener provided in the first aspect above or the high-temperature resistant fracturing fluid thickener prepared by the preparation method provided in the second aspect above, to obtain the fracturing fluid;

[0025] Preferably, the covalent crosslinking agent has the structure of formula (I).

[0026]

[0027] In equation (I), R is C 10 -C 25 Straight-chain hydrocarbon group; n is an integer from 1 to 6;

[0028] Preferably, R is C 10 -C 25 straight-chain alkyl, C 17 H 33 -or C 21 H 41 -; n is an integer between 2 and 4; more preferably, R is CH3(CH2). 11 -, CH3(CH2)7-CH=CH-(CH2)7- or CH3(CH2)7-CH=CH-(CH2) 11 -; n is 2 or 3;

[0029] More preferably, in the aqueous solution of the high-temperature fracturing fluid thickener provided in the first aspect or the high-temperature fracturing fluid thickener prepared by the preparation method provided in the second aspect, the mass fraction of the aqueous solution of the high-temperature fracturing fluid thickener is 0.4% to 0.9%; and / or, the mass ratio of the high-temperature fracturing fluid thickener provided in the first aspect or the high-temperature fracturing fluid thickener prepared by the preparation method provided in the second aspect to the covalent crosslinking agent is (3 to 5): 1.

[0030] The covalent crosslinking agent and its preparation method described in this invention include:

[0031] (A) A functional primary amine (i) reacts with epichlorohydrin to give intermediate (ii);

[0032] (B) Intermediate (ii) reacts with a tertiary amine to obtain the covalent crosslinking agent (I).

[0033]

[0034] Where R is C 10 -C 25 Straight-chain hydrocarbon group; n is an integer from 1 to 6.

[0035] Preferably, R is C 10 -C 25 straight-chain alkyl, C 17 H 33 -or C 21 H 41 -; n is an integer between 2 and 4. More preferably, R is CH3(CH2). 11 -, CH3(CH2)7-CH=CH-(CH2)7- or CH3(CH2)7-CH=CH-(CH2) 11 -; n is 2 or 3.

[0036] In step (A), the functional primary amine (i) is a primary amine containing a sulfonic acid group. Preferably, the functional primary amine is selected from 2-aminoethanesulfonic acid and 3-aminopropanesulfonic acid, etc.

[0037] The molar ratio of the functional primary amine to epichlorohydrin is 1:2-3, preferably 1:2.5.

[0038] The reaction in step (A) can be carried out in the presence of a solvent, which can be an alcohol solvent, such as methanol, ethanol, propanol, butanol, etc.

[0039] The reaction of the functional primary amine (i) with epichlorohydrin can be carried out at room temperature (25°C). After the reaction is complete, the solvent is removed by evaporation to obtain intermediate (ii).

[0040] In step (B), the tertiary amine is selected from C. 10 -C 25 Linear hydrocarbon amide propyl dimethylamine; preferably, the tertiary amine is selected from erucic acid amide propyl dimethylamine, oleic acid amide propyl dimethylamine, dodecyl amide propyl dimethylamine, etc.

[0041] The molar ratio of intermediate (ii) to the tertiary amine is 1:1.5-2.5, preferably, the molar ratio of intermediate (ii) to the tertiary amine is 1:1.9.

[0042] Intermediate (ii) and a tertiary amine are heated under reflux in a low-molecular-weight alcohol solvent to obtain a crude covalent crosslinking agent. The alcohol solvent can be methanol, ethanol, propanol, butanol, etc.

[0043] The crude product obtained after the reaction was washed with a mixed solvent of dichloromethane and petroleum ether to obtain the covalent crosslinking agent (I) in high purity.

[0044] The fifth aspect of the present invention provides the application of the high-temperature resistant fracturing fluid thickener provided in the first aspect above, or the high-temperature resistant fracturing fluid thickener prepared by the preparation method provided in the second aspect above, or the fracturing fluid provided in the third aspect above, or the fracturing fluid prepared by the preparation method provided in the fourth aspect above, in oil extraction.

[0045] Beneficial effects:

[0046] The high-temperature resistant fracturing fluid thickener provided by this invention, together with the covalent crosslinking agent, can be formulated to obtain a fracturing fluid that is temperature-resistant, salt-resistant, and shear-resistant, which can significantly improve the stability and proppant carrying capacity of the polymer under high temperature and high salt conditions.

[0047] Compared with traditional high-temperature resistant polymer thickeners, this invention introduces sodium p-styrene sulfonate into the molecular chain of the high-temperature fracturing fluid thickener, which greatly improves the thickener's resistance to Ca. 2+ Mg 2+The high tolerance to divalent metal ions allows the high-temperature fracturing fluid thickener to maintain its thickening and rheological properties even in harsher reservoir environments. Simultaneously, this invention introduces highly charged cationic groups into the molecular chain of the high-temperature fracturing fluid thickener, which interact with anionic groups, significantly increasing the structural viscosity and elasticity of the thickener, thus greatly improving the proppant-carrying capacity of the fracturing fluid. Furthermore, the cationic groups in the high-temperature fracturing fluid thickener of this invention can form an associated network structure with the covalent crosslinking agent, achieving a "network crosslinking" thickening effect.

[0048] The fracturing fluid provided in this invention exhibits superior temperature and salt resistance as well as shear resistance, which gives it a significant advantage in fracturing processes in oil extraction.

[0049] Compared with existing technologies, the preparation method of the high-temperature fracturing fluid thickener described in this invention is simpler and easier to operate, reducing the complexity and uncertainty in the production process, making large-scale application possible, and further enhancing its application value in the petroleum industry.

[0050] In summary, the fracturing fluid provided by this invention exhibits significant advantages over existing technologies in terms of performance, cost, environmental impact, and application flexibility, providing strong technical support for the efficient and sustainable development of the petroleum industry. Attached Figure Description

[0051] Figure 1 The fracturing fluid gel prepared in Example 5 of this invention was subjected to a 170-second incubation period in clean water at 180°C. -1 Test diagram of temperature and shear resistance at the specified time;

[0052] Figure 2 The fracturing fluid gel prepared in Example 5 of this invention was subjected to a brine treatment at 180°C for 170 seconds. -1 Test diagram of temperature and shear resistance at the specified time;

[0053] Figure 3 The image shows the drag reduction performance test results of the high-temperature fracturing fluid thickener prepared in Example 5 of this invention.

[0054] Figure 4 The anti-swelling performance of the fracturing fluid gel prepared in Example 5 of this invention was tested. Detailed Implementation

[0055] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to these embodiments.

[0056] Unless otherwise specified, all raw materials and equipment used in the following embodiments and comparative examples of the present invention are commercially available.

[0057] In the examples and comparative examples:

[0058] Unless otherwise specified, thermos flasks, thermometers, nitrogen blowers, mixers, and high-speed grinders are all commercially available items.

[0059] Acrylamide was purchased from Maclean Company, A800656-500g;

[0060] Acrylic acid was purchased from McLean Company, A800293-500g;

[0061] Methacryloxyethyl dimethyl benzyl ammonium chloride was purchased from Maclean Company, B904489-500g;

[0062] Azobisisobutyrazoline hydrochloride was purchased from Maclean Company, A824730-25g;

[0063] Sodium hypophosphite was purchased from McLean Company, S909357-100g;

[0064] Ammonium persulfate was purchased from Maclean Company, A801035-500g;

[0065] Sodium metabisulfite was purchased from Maclean Company, S818094-100g;

[0066] Azobisisobutylamidine hydrochloride was purchased from Wuhan Rongcan Biotechnology Co., Ltd., 1 kg;

[0067] Sodium formate was purchased from Maclean Company, S817616-100g;

[0068] Potassium persulfate was purchased from Maclean Company, P821909-100g;

[0069] Ferrous ammonium sulfate was purchased from Maclean Company, A801066-500g;

[0070] Acryloyloxyethyl dimethyl benzyl ammonium chloride was purchased from Maclean Company, B904489-100g;

[0071] Isopropyl alcohol was purchased from Maclean's, 1811932-500ml;

[0072] Sodium persulfate was purchased from Maclean Company, S817729-500g;

[0073] Acrylamido-2-methylpropyltrimethylammonium chloride was purchased from Hubei Qifei Pharmaceutical Chemical Co., Ltd., 1 kg.

[0074] Example 1

[0075] This embodiment illustrates the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0076] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 20 parts acrylamide, 10 parts acrylic acid, 5 parts sodium p-styrene sulfonate, 1 part cationic monomer, 0.3 parts initiator azobisisobutyrazoline hydrochloride, 0.03 parts chain transfer agent sodium hypophosphite, 0.01 parts oxidant ammonium persulfate, 0.02 parts reducing agent sodium metabisulfite, and 56 parts deionized water.

[0077] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0078] (1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate, methacryloxyethyl dimethyl benzyl ammonium chloride (MBDAC) and deionized water in the specified weight parts until the solution is clear and transparent to obtain the reaction solution;

[0079] (2) After adjusting the pH of the reaction solution to 6.7 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0080] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant and reducing agent in the specified weight parts in sequence to initiate the polymerization reaction. After the reaction solution becomes viscous, remove nitrogen and seal. After 3 hours, the polymer colloid is obtained.

[0081] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 70°C for 5 hours, and then ground into powder by a high-speed grinder. The powder is then screened through a 120-mesh sieve to obtain the polymer powder, which is the high-temperature fracturing fluid thickener.

[0082] Example 2

[0083] This embodiment illustrates the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0084] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 22 parts acrylamide, 11 parts acrylic acid, 7 parts sodium p-styrene sulfonate, 1 part cationic monomer, 0.35 parts azobisisobutylamidine hydrochloride initiator, 0.04 parts sodium formate chain transfer agent, 0.01 parts potassium persulfate oxidant, 0.02 parts ferrous ammonium sulfate reducing agent, and 52 parts deionized water.

[0085] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0086] (1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate, methacryloxyethyl dimethyl benzyl ammonium chloride (MBDAC) and deionized water in the specified weight parts until the solution is clear and transparent to obtain the reaction solution;

[0087] (2) After adjusting the pH of the reaction solution to 7.0 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0088] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 4 hours, the polymer colloid is obtained.

[0089] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 90°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0090] Example 3

[0091] This embodiment illustrates the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0092] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 25 parts acrylamide, 15 parts acrylic acid, 9 parts sodium p-styrene sulfonate, 2 parts cationic monomer, 0.45 parts initiator azobisisobutyrazoline hydrochloride, 0.04 parts chain transfer agent isopropanol, 0.01 parts oxidant sodium persulfate, 0.02 parts reducing agent ferrous ammonium sulfate, and 43 parts deionized water.

[0093] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0094] (1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate, acryloyloxyethyl dimethyl benzyl ammonium chloride (AODBAC) and deionized water in the specified weight parts until the solution is clear and transparent to obtain the reaction solution;

[0095] (2) After adjusting the pH of the reaction solution to 6.5 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0096] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 3.5 hours, the polymer colloid is obtained.

[0097] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 100°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0098] Example 4

[0099] This embodiment illustrates the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0100] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 23 parts acrylamide, 12 parts acrylic acid, 8 parts sodium p-styrene sulfonate, 1 part cationic monomer, 0.4 parts azobisisobutylamidine hydrochloride initiator, 0.045 parts sodium hypophosphite chain transfer agent, 0.01 parts ammonium persulfate oxidant, 0.02 parts sodium metabisulfite reducing agent, and 44 parts deionized water.

[0101] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0102] (1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate, acryloyloxyethyl dimethyl benzyl ammonium chloride (AODBAC) and deionized water in the specified weight parts until the solution is clear and transparent to obtain the reaction solution;

[0103] (2) After adjusting the pH of the reaction solution to 6.9 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0104] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 3 hours, the polymer colloid is obtained.

[0105] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 100°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0106] Example 5

[0107] This embodiment illustrates the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0108] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 23 parts acrylamide, 10 parts acrylic acid, 7 parts sodium p-styrene sulfonate, 1.6 parts cationic monomer, 0.3 parts initiator azobisisobutyrazoline hydrochloride, 0.03 parts chain transfer agent sodium formate, 0.01 parts oxidant potassium persulfate, 0.02 parts reducing agent ferrous ammonium sulfate, and 49.8 parts deionized water.

[0109] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0110] (1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate, 2-acrylamido-2-methylpropyltrimethylammonium chloride (AMPTAC) and deionized water in the specified weight parts until the solution is clear and transparent to obtain the reaction solution;

[0111] (2) After adjusting the pH of the reaction solution to 6.8 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0112] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 3.5 hours, the polymer colloid is obtained.

[0113] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 100°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0114] Example 6

[0115] This embodiment illustrates the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0116] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 24 parts acrylamide, 13 parts acrylic acid, 6 parts sodium p-styrene sulfonate, 1 part cationic monomer (0.5 parts each of 2-acrylamido-2-methylpropyltrimethylammonium chloride (AMPTAC) and methacryloyloxyethyl dimethylbenzylammonium chloride (MBDAC)), 0.5 parts initiator azobisisobutyrazoline hydrochloride, 0.05 parts chain transfer agent sodium formate, 0.01 parts oxidant potassium persulfate, 0.02 parts reducing agent ferrous ammonium sulfate, and 52 parts deionized water.

[0117] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0118] (1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate, 2-acrylamido-2-methylpropyltrimethylammonium chloride (AMPTAC), methacryloyloxyethyl dimethylbenzylammonium chloride (MBDAC) and deionized water in the specified weight parts until the solution is clear and transparent to obtain the reaction solution;

[0119] (2) After adjusting the pH of the reaction solution to 6.8 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0120] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 3.5 hours, the polymer colloid is obtained.

[0121] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 100°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0122] Example 7

[0123] This embodiment illustrates the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0124] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 21 parts acrylamide, 14 parts acrylic acid, 6 parts sodium p-styrene sulfonate, 1 part cationic monomer, 0.5 parts initiator azobisisobutyrazoline hydrochloride, 0.05 parts chain transfer agent sodium formate, 0.01 parts oxidant potassium persulfate, 0.02 parts reducing agent ferrous ammonium sulfate, and 56 parts deionized water.

[0125] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0126] (1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate, 2-acrylamido-2-methylpropyltrimethylammonium chloride (AMPTAC) and deionized water in the specified weight parts until the solution is clear and transparent to obtain the reaction solution;

[0127] (2) After adjusting the pH of the reaction solution to 6.8 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0128] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 3.5 hours, the polymer colloid is obtained.

[0129] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 100°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0130] Comparative Example 1

[0131] This comparative example is used to illustrate the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0132] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 23 parts acrylamide, 10 parts acrylic acid, 7 parts sodium p-styrene sulfonate, 0.3 parts azobisisobutyrazoline hydrochloride initiator, 0.03 parts sodium formate chain transfer agent, 0.01 parts potassium persulfate oxidant, 0.02 parts ferrous ammonium sulfate reducing agent, and 49.8 parts deionized water.

[0133] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0134] 1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate and deionized water in the specified weight proportions until the solution is clear and transparent to obtain the reaction solution;

[0135] (2) After adjusting the pH of the reaction solution to 6.8 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0136] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 3.5 hours, the polymer colloid is obtained.

[0137] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 100°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0138] Comparative Example 2

[0139] This comparative example is used to illustrate the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0140] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 23 parts acrylamide, 10 parts acrylic acid, 1.6 parts cationic monomer, 0.3 parts initiator azobisisobutyrazoline hydrochloride, 0.03 parts chain transfer agent sodium formate, 0.01 parts oxidant potassium persulfate, 0.02 parts reducing agent ferrous ammonium sulfate, and 49.8 parts deionized water.

[0141] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0142] 1) Mix and stir the acrylamide, acrylic acid, 2-acrylamido-2-methylpropyltrimethylammonium chloride (AMPTAC) and deionized water in the specified weight proportions until the solution is clear and transparent to obtain the reaction solution;

[0143] (2) After adjusting the pH of the reaction solution to 6.8 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0144] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 3.5 hours, the polymer colloid is obtained.

[0145] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 100°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0146] Comparative Example 3

[0147] This comparative example is used to illustrate the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0148] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 23 parts acrylamide, 10 parts acrylic acid, 3 parts sodium p-styrene sulfonate, 1.6 parts cationic monomer, 0.3 parts initiator azobisisobutyrazoline hydrochloride, 0.03 parts chain transfer agent sodium formate, 0.01 parts oxidant potassium persulfate, 0.02 parts reducing agent ferrous ammonium sulfate, and 49.8 parts deionized water.

[0149] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0150] 1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate, 2-acrylamido-2-methylpropyltrimethylammonium chloride (AMPTAC) and deionized water in the specified weight proportions until the solution is clear and transparent to obtain the reaction solution;

[0151] (2) After adjusting the pH of the reaction solution to 6.8 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0152] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 3.5 hours, the polymer colloid is obtained.

[0153] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 100°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0154] Comparative Example 4

[0155] This comparative example is used to illustrate the high-temperature resistant fracturing fluid thickener and its preparation method described in this invention.

[0156] The raw materials for preparing the high-temperature fracturing fluid thickener include the following components: 23 parts acrylamide, 10 parts acrylic acid, 7 parts sodium p-styrene sulfonate, 0.5 parts cationic monomer, 0.3 parts initiator azobisisobutyrazoline hydrochloride, 0.03 parts chain transfer agent sodium formate, 0.01 parts oxidant potassium persulfate, 0.02 parts reducing agent ferrous ammonium sulfate, and 49.8 parts deionized water.

[0157] The preparation method of high-temperature resistant fracturing fluid thickener is as follows:

[0158] 1) Mix and stir the acrylamide, acrylic acid, sodium p-styrene sulfonate, 2-acrylamido-2-methylpropyltrimethylammonium chloride (AMPTAC) and deionized water in the specified weight proportions until the solution is clear and transparent to obtain the reaction solution;

[0159] (2) After adjusting the pH of the reaction solution to 6.8 with a 20% sodium hydroxide aqueous solution, the reaction solution was cooled to 5°C.

[0160] (3) Pour the cooled reaction solution from step (2) into a thermos, then insert a thermometer and a nitrogen blower. After blowing nitrogen to remove oxygen, add the initiator, chain transfer agent, oxidant, and reducing agent in the specified weight proportions in sequence. Initiate the polymerization reaction. After the reaction solution becomes viscous, remove the nitrogen and seal it. After 3.5 hours, the polymer colloid is obtained.

[0161] (4) The polymer colloid obtained in step (3) is crushed into colloidal particles by a mixer. The colloidal particles are dried at 100°C for 5 hours, and then ground into powder by a high-speed grinder and screened through a 120-mesh sieve. The resulting polymer powder is the high-temperature fracturing fluid thickener.

[0162] Application Examples 1-7

[0163] This application example illustrates the use of the high-temperature resistant fracturing fluid thickener described in this invention, specifically providing a high-temperature and shear-resistant fracturing fluid gel.

[0164] The preparation of the high-temperature and shear-resistant fracturing fluid gel includes: using 50% standard saline (the standard saline with a salinity of 80000 mg / L is diluted by half, i.e., the volume ratio of the standard saline is 50%, the same below) as a solvent, preparing the high-temperature fracturing fluid thickener prepared in Examples 1-7 of the present invention into a solution with a mass fraction of 0.6% and adding 0.3% of the covalent crosslinking agent to form the fracturing fluid gel.

[0165] The standard brine with a mineralization of 80,000 mg / L is prepared as follows: 5.5 wt% NaCl + 2.0 wt% KCl + 0.45 wt% MgCl2 + 0.55 wt% CaCl2.

[0166] Compare and contrast examples 1-4

[0167] This comparative application example illustrates the application of the high-temperature resistant fracturing fluid thickener described in this invention, specifically providing a high-temperature and shear-resistant fracturing fluid gel.

[0168] The preparation of the high-temperature and shear-resistant fracturing fluid gel includes: using 50% standard saline as a solvent, preparing the high-temperature fracturing fluid thickener prepared in Comparative Examples 1-4 of the present invention into a solution with a mass fraction of 0.6%, and adding 0.3% of the covalent crosslinking agent to form the fracturing fluid gel.

[0169] The standard brine with a mineralization of 80,000 mg / L is prepared as follows: 5.5 wt% NaCl + 2.0 wt% KCl + 0.45 wt% MgCl2 + 0.55 wt% CaCl2.

[0170] In the application examples and comparative application examples of this invention, the preparation method of the covalent crosslinking agent includes:

[0171] 6.8 g of 3-aminopropanesulfonic acid was dissolved in 50 mL of methanol and transferred to a single-necked flask. 11.57 g of epichlorohydrin was slowly added dropwise to the flask using a constant-pressure dropping funnel at 5 °C. After the addition was complete, the mixture was stirred at 25 °C for 14 h. After the reaction was complete, the solvent was removed using a rotary evaporator to obtain the intermediate.

[0172] 12.06 g of the above intermediate and 21.34 g of dodecylamidopropyl dimethylamine were dissolved in 100 mL of methanol and transferred to a 250 mL single-necked flask. The mixture was stirred and refluxed at 85 °C for 24 h. After the reaction was complete, the solvent was removed using a rotary evaporator. The crude product was washed three times with a mixture of dichloromethane and petroleum ether (v / v = 1:5), and the precipitate was collected. The remaining washing liquid was then removed using a rotary evaporator to obtain the high-purity covalent crosslinking agent.

[0173] Performance testing

[0174] (I) Based on the comprehensive mineralization test of formation water in oilfield development, the fracturing fluid gels prepared in Application Example 1-7 and Comparative Application Example 1-4 were tested using an electronic six-speed viscometer (Shandong Meike Instrument Co., Ltd. ZNN-D6B) for 5 minutes and 30 minutes of dissolution, respectively. The dissolution time was also recorded. The test results are shown in Table 1.

[0175] Table 1 Salt resistance test of fracturing fluid gel

[0176]

[0177] As shown in Table 1, the temperature- and shear-resistant fracturing fluid described in Application Example 5 has the fastest dissolution rate, the highest apparent viscosity of the gel after 30 minutes, and the best salt resistance. In contrast, the apparent viscosity value of the comparative application example is lower.

[0178] (ii) Conduct temperature and shear resistance tests according to the standard SY-T5107-2005 Water-based fracturing fluid performance evaluation method;

[0179] The temperature and shear resistance of the fracturing fluid gel formed by the high-temperature resistant fracturing fluid thickener prepared in Example 5 of this invention and the covalent crosslinking agent was tested using a HAAKE MARS 40 rheometer (Shanghai Hengze Technology Co., Ltd.).

[0180] The fracturing fluid gels formed by the covalent crosslinking agent with a mass fraction of 0.6% and 0.3% of the high-temperature resistant fracturing fluid thickener prepared in Example 5 of this invention, respectively, using water and 50% standard saline as solvents, were subjected to temperature and shear resistance tests.

[0181] In the 170s -1 The fracturing fluid gel was subjected to shearing at 180℃ for 120 minutes. The temperature-viscosity curve of the gel, using water as a solvent, is shown below. Figure 1 As shown, the apparent viscosity of the high-temperature fracturing fluid thickener prepared in Example 5 of this invention is maintained at around 113 mPa·s.

[0182] In the 170s -1 The fracturing fluid gel was subjected to shearing at 180℃ for 120 minutes. The temperature-viscosity curve of the gel, using 50% standard brine as a solvent, is shown below. Figure 2 As shown, the apparent viscosity of the high-temperature fracturing fluid thickener prepared in Example 5 of this invention is maintained at around 100 mPa·s.

[0183] This indicates that the high-temperature resistant fracturing fluid thickener prepared in Example 5 of the present invention and the fracturing fluid gel formed by the covalent crosslinking agent have excellent temperature and shear resistance properties, and are suitable for high-temperature deep well fracturing operations.

[0184] (III) Drag reduction performance testing shall be conducted in accordance with the standard SY-T5107-2005, Performance Evaluation Method for Water-Based Fracturing Fluids:

[0185] According to the experimental design, the high-temperature resistant fracturing fluid thickener prepared in Example 5 of this invention was mixed with brine of different concentrations, specifically pure water, 10% standard brine, 20% standard brine, and 30% standard brine, to prepare a series of slickwater fracturing fluids. The dosage (mass percentage) of the high-temperature resistant fracturing fluid thickener prepared in Example 5 of this invention was 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, and 0.30%, respectively. The drag reduction characteristics of the slickwater fracturing fluid were measured using a pipeline friction tester (Chengdu Yanxin Technology Co., Ltd.). See Table 2 for the statistical analysis. Figure 3 .

[0186] Table 2

[0187]

[0188] Refer to Table 2 and Figure 3 The data results show that even under various salinity environments and different addition amounts, the high-temperature fracturing fluid thickener prepared in Example 5 of this invention exhibits good drag reduction efficiency, with its drag reduction ratio consistently maintained above 65%. This means that it can ensure high operating efficiency and quality under both conventional and high salinity conditions, demonstrating its good adaptability and practicality, and laying a solid foundation for subsequent industrial applications.

[0189] (iv) Conduct interface and residue tests on the rupture fluid according to the standard SY-T5107-2005, the performance evaluation method for water-based fracturing fluid:

[0190] For the fracturing fluid gel prepared in Example 5 of this invention, ammonium persulfate was used to break the gel. The amount of ammonium persulfate added was 0.04 wt% of the fracturing fluid gel. The viscosity of the breaking fluid, the breaking time, the surface tension, interfacial tension and residue content of the breaking fluid were recorded at temperatures of 50℃, 60℃ and 70℃. The results are shown in Table 3.

[0191] Table 3. Tests of debonding liquid performance at different temperatures

[0192]

[0193] As can be seen from Table 3, the fracturing fluid gel prepared using the high-temperature resistant fracturing fluid thickener prepared in this invention has a short gel breaking time, and the viscosity of the gel breaking fluid is less than 5 mPa·s, the surface tension is less than 28 mN / m, the interfacial tension is less than 2 mN / m, and the residue content is less than 50 mg / L, which is conducive to the flowback of fracturing fluid.

[0194] (v) The anti-swelling performance of the breaker fluid was tested according to the standard SY-T5107-2005, the performance evaluation method for water-based fracturing fluids:

[0195] For the anti-swelling rate test, high-quality sodium-based bentonite (HY-39 from Haoyuan Bentonite Factory, Fangzi District, Weifang City) was used. Three 15ml centrifuge tubes were used, with 0.5g of bentonite added. 10ml of kerosene, 10ml of the gel breaking solution from test (IV) at 70℃, and 10ml of distilled water were added to each tube. The tubes were shaken thoroughly, allowed to stand for 2 hours, and then centrifuged. The swelling volume after centrifugation was recorded. Figure 4 ;

[0196] according to Figure 4 It can be seen that c) bentonite does not expand much in kerosene, b) the expansion volume of bentonite in distilled water is 20 times that of bentonite in kerosene, a) the expansion volume of bentonite in the breaker solution is about 8 times that of bentonite in kerosene. Therefore, the anti-swelling rate of the breaker solution is 72.2%, and the breaker solution has good anti-swelling performance.

[0197] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A high-temperature resistant fracturing fluid thickener, characterized in that, The raw materials for preparing the high-temperature resistant fracturing fluid thickener include acrylamide, acrylic acid, sodium p-styrene sulfonate, cationic monomer, initiator, chain transfer agent, oxidant, reducing agent, and deionized water; the weight parts of each component in the raw materials for preparing the high-temperature resistant fracturing fluid thickener are as follows:

2. The high-temperature resistant fracturing fluid thickener according to claim 1, characterized in that, The cationic monomer is selected from at least one of methacryloyloxyethyl dimethyl benzyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, and 2-acrylamido-2-methylpropyltrimethyl ammonium chloride.

3. The high-temperature resistant fracturing fluid thickener according to claim 1 or 2, characterized in that, The initiator is selected from azo initiators; preferably, the azo initiator is selected from azobisisobutyrazoline hydrochloride and / or azobisisobutyramidine hydrochloride.

4. The high-temperature fracturing fluid thickener according to any one of claims 1-3, characterized in that, The chain transfer agent is selected from at least one of sodium hypophosphite, sodium formate, and isopropanol.

5. The high-temperature fracturing fluid thickener according to any one of claims 1-4, characterized in that, The oxidant is selected from at least one of ammonium persulfate, potassium peroxymonosulfate, and sodium persulfate; And / or, the reducing agent is selected from sodium metabisulfite and / or ferrous ammonium sulfate.

6. A method for preparing a high-temperature resistant fracturing fluid thickener according to any one of claims 1-5, characterized in that, Includes the following steps, (1) Mix the acrylamide, acrylic acid, sodium p-styrene sulfonate, cationic monomer and deionized water in the specified weight parts to obtain a reaction solution; (2) Under an inactive atmosphere, the initiator, chain transfer agent, oxidant and reducing agent in the specified weight parts are added to the reaction solution to obtain the high-temperature fracturing fluid thickener.

7. The preparation method according to claim 6, characterized in that, In step (1), the pH of the reaction solution is adjusted to 5-7 using a pH adjuster; preferably, the pH adjuster is selected from a sodium hydroxide solution with a mass fraction of 20%-40% or a sodium bicarbonate solution with a mass fraction of 20%-40%. And / or, in step (1), the temperature of the reaction solution is 0℃~5℃; And / or, in step (2), the inactive atmosphere is selected from nitrogen and / or argon; And / or, in step (2), the reaction conditions include: a time of 3 to 4 hours; And / or, in step (2), the high-temperature fracturing fluid thickener further includes crushing, drying and pulverizing treatment; preferably, the drying conditions include: temperature of 70℃~100℃; time of 3 hours~5 hours; the particle size of the pulverized high-temperature fracturing fluid thickener is 80 mesh~120 mesh.

8. A fracturing fluid, characterized in that, The fracturing fluid includes any one of the high-temperature resistant fracturing fluid thickeners according to claims 1-5 or the high-temperature resistant fracturing fluid thickener prepared by the preparation method according to claim 6 or 7.

9. A method for preparing the fracturing fluid according to claim 8, characterized in that, The fracturing fluid is obtained by adding a covalent crosslinking agent to an aqueous solution of the high-temperature resistant fracturing fluid thickener prepared by any one of claims 1-5 or the preparation method described in claim 6 or 7; Preferably, the covalent crosslinking agent has the structure of formula (I). In equation (I), R is C 10 -C 25 Straight-chain hydrocarbon group; n is an integer from 1 to 6; More preferably, R is C 10 -C 25 straight-chain alkyl, C 17 H 33 -or C 21 H 41 -; n is an integer from 2 to 4; more preferably, R is CH3(CH2). 11 -, CH3(CH2)7-CH=CH-(CH2)7- or CH3(CH2)7-CH=CH-(CH2) 11 -; n is 2 or 3; More preferably, in the aqueous solution of the high-temperature fracturing fluid thickener according to any one of claims 1-5 or the high-temperature fracturing fluid thickener prepared by the preparation method according to claim 6 or 7, the mass fraction of the aqueous solution of the high-temperature fracturing fluid thickener according to any one of claims 1-5 or the high-temperature fracturing fluid thickener prepared by the preparation method according to claim 6 or 7 is 0.4% to 0.9%; and / or, the mass ratio of the high-temperature fracturing fluid thickener according to any one of claims 1-5 or the high-temperature fracturing fluid thickener prepared by the preparation method according to claim 6 or 7 to the covalent crosslinking agent is (3-5):

1.

10. The application of a high-temperature resistant fracturing fluid thickener according to any one of claims 1-5, or a high-temperature resistant fracturing fluid thickener prepared by the preparation method according to claim 6 or 7, or a fracturing fluid according to claim 8, or a fracturing fluid prepared by the preparation method according to claim 9, in oil extraction.

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