A temperature-resistant thickener for fracturing

Abstract

This invention belongs to the field of fracturing technology, specifically relating to a temperature-resistant thickener for fracturing. The preparation method of the temperature-resistant thickener is as follows: First, an aromatic ring is modified onto the surface of bentonite using an aromatic cyclosilane coupling agent, and then reacted with chlorosulfonic acid to form a sulfonic acid group. Finally, under the action of a chlorinating agent and a catalyst, a sulfonyl chloride group is modified onto the bentonite. Second, guar gum is modified with an amino group using an aminosilane coupling agent. Then, under the catalysis of triethylamine, the amino-modified guar gum and the sulfonyl chloride group on the modified bentonite undergo a nucleophilic substitution reaction to generate a sulfonamide group, thus obtaining a modified guar gum / bentonite composite, i.e., a temperature-resistant thickener, which has better temperature resistance, salt resistance, and shear resistance, and can be applied to more fracturing construction sites.

Description

Technical Field

[0001] This invention relates to the field of fracturing technology, specifically to a temperature-resistant thickener for fracturing. Background Technology

[0002] Fracturing technology is one of the key technologies in the field of oil and gas extraction. It has become a core means to improve the production and recovery rate of oil and gas wells. The performance of fracturing fluid directly affects the conductivity of oilfield fractures and the degree of reservoir damage.

[0003] Thickeners are an important component of fracturing fluids. Their function is to increase the fluid viscosity, carry the proppant into the fracture, and form a gel with a certain strength to support the fracture after the pump stops. Commonly used thickeners include natural and synthetic thickeners. Among natural thickeners, guar gum and its derivatives are the most widely used, but their temperature and salt resistance is poor, especially in deep, high-temperature environments or environments with high mineralization, where the thickening effect is significantly reduced. Common synthetic thickeners include polyacrylamide, but it has poor adaptability to high-temperature and high-salt environments, is prone to precipitation, has insufficient shear resistance, is difficult to degrade, and has high environmental treatment costs.

[0004] In order to improve the current application status of polyacrylamide thickeners, the patent "CN202310875301.8" entitled "A composite thickener for fracturing and its preparation method" provides a composite thickener for fracturing, which combines plant gum with polyacrylamide to improve its temperature resistance. However, when applied to some complex high-mineralization formations, the viscosity decreases and the sand-carrying capacity is weakened.

[0005] Based on this, a more widely applicable temperature-resistant thickener for fracturing is proposed. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention proposes a temperature-resistant thickener for fracturing, which not only meets the temperature resistance requirements of the thickener but also satisfies additional requirements such as salt resistance and shear resistance, thereby improving construction efficiency.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A temperature-resistant thickener for fracturing, wherein the preparation method of the temperature-resistant thickener is as follows:

[0009] S1. Add bentonite to anhydrous toluene and ultrasonically disperse for 5-10 min. Add phenyltrimethoxysilane and react at 70-80℃ for 8-10 h to modify aromatic ring groups on the surface of bentonite. After the reaction is complete, centrifuge and filter, wash with anhydrous toluene and ethanol in sequence, and dry to obtain silane-modified bentonite.

[0010] S2. Add silane-modified bentonite to dichloromethane and ultrasonically disperse for 3-5 min to obtain a suspension. Under ice bath conditions, add chlorosulfonic acid to the suspension, purge with nitrogen for protection, and stir at room temperature for 4-5 h to allow the aromatic ring groups on the surface of the silane-modified bentonite to react with chlorosulfonic acid to generate sulfonic acid groups. Add chlorinating agent thionyl chloride and catalyst N,N-dimethylformamide, raise the temperature to 30-38℃ and continue the reaction for 5-7 h. After the reaction is completed, quench the mixture in an ice bath, purge with nitrogen for 10-20 min to remove byproducts, centrifuge and filter, wash with dichloromethane and then dry with anhydrous sodium sulfate to obtain modified bentonite containing sulfonyl chloride groups. Store in a dry and sealed environment.

[0011] S3. Place guar gum in deionized water and stir for 20-30 min. Adjust the pH to 5-6 with 2-4% hydrochloric acid solution. Add N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane and heat to 60-70℃. Keep the temperature and stir for 3-4 h. After the reaction is complete, cool to room temperature to obtain a mixed solution. Add modified bentonite containing sulfonyl chloride group and triethylamine to tetrahydrofuran and stir for 15-30 min to disperse evenly to obtain a dispersion. Add the dispersion to the mixed solution and heat to 40-50℃ to react for 6-8 h. After the reaction is complete, centrifuge and filter. Wash the product 2-3 times with anhydrous ethanol and vacuum dry to obtain the modified guar gum / bentonite composite, i.e., the heat-resistant thickener.

[0012] Preferably, the amount of phenyltrimethoxysilane added in S1 is 5-7% of the mass of bentonite.

[0013] Preferably, the ratio of bentonite to anhydrous toluene in S1 is 1g:7-10ml, and the ultrasonic frequency is 40-70kHz.

[0014] Preferably, the drying temperature in S1 is 60-70°C and the drying time is 7-8 hours.

[0015] Preferably, the ratio of silane-modified bentonite to dichloromethane in S2 is 1g:7-10ml, and the ultrasonic frequency is 40-70kHz.

[0016] Preferably, the ice bath in S2 is 0-5°C; the molar ratio of silane-modified bentonite, chlorosulfonic acid and thionyl chloride is 1:2-3:3-4, and the addition rate of chlorosulfonic acid is 5-12 ml / min.

[0017] Preferably, the amount of catalyst N,N-dimethylformamide added in S2 is 2 to 4% of the mass of silane-modified bentonite.

[0018] Preferably, the amount of N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane added in S3 is 3-5% of the mass of guar gum; the mass ratio of guar gum to deionized water is 1:20-30.

[0019] Preferably, the mass ratio of modified bentonite containing sulfonyl chloride groups to guar gum in S3 is 7-9:12-14.

[0020] Preferably, the amount of triethylamine added in S3 is 1.2 to 1.5 times the molar amount of sulfonyl chloride groups in the modified bentonite containing sulfonyl chloride groups.

[0021] Preferably, the ratio of modified bentonite containing sulfonyl chloride groups to tetrahydrofuran in S3 is 1g:12-14ml.

[0022] Preferably, the addition rate of the dispersion to the mixture in step S3 is 30-40 ml / min.

[0023] Preferably, the vacuum drying temperature in step S3 is 60–70°C, and the time is 6–8 hours.

[0024] Bentonite possesses excellent thixotropic and sand-carrying properties. Upon contact with water, it absorbs water and swells, exhibiting a high viscosity that aids in suspension support. Combining bentonite with guar gum, due to the large number of hydrophilic groups in guar gum, allows it to form a network structure through hydrogen bonds between molecular chains upon contact with water. This, combined with the supportive properties of bentonite, can further enhance its thickening and sand-carrying effect. However, in actual construction, the following drawbacks exist: bentonite exhibits poor dispersion, is prone to agglomeration, easily clogs pores, and tends to leave residues during backfilling; bentonite fracturing mixtures prepared with seawater are prone to stratification, and pre-preparation with fresh water is costly and difficult to transport; and it has poor salt and temperature resistance, making it only suitable for low-salt formations around 100℃.

[0025] The main design concept of this invention is as follows: First, aromatic rings are modified onto the surface of bentonite using an aromatic cyclosilane coupling agent, then reacted with chlorosulfonic acid to form sulfonic acid groups. Finally, sulfonyl chloride groups are modified onto the bentonite under the action of a chlorinating agent and a catalyst. Second, guar gum is modified with an amino group using an amino silane coupling agent. Then, under the catalysis of triethylamine, the amino-modified guar gum and the sulfonyl chloride groups on the modified bentonite containing sulfonyl chloride groups undergo a nucleophilic substitution reaction to generate sulfonamide groups, resulting in a modified guar gum / bentonite composite, i.e., a temperature-resistant thickener. The sulfonamide groups have strong polarity, allowing this thickener to disperse rapidly in water. It also exhibits better compatibility with other fracturing fluid additives such as crosslinking agents and breaker agents. When formulated with seawater, it is less prone to stratification and precipitation, reducing water resource costs. Furthermore, the sulfonamide groups in the modified guar gum / bentonite composite are more stable and possess strong electron-withdrawing properties, thus further improving the temperature and salt resistance of the thickener system. Meanwhile, the -NH- bonds in the sulfonamide groups of the modified guar gum / bentonite composite can form hydrogen bonds with the hydroxyl groups in guar gum and water molecules adsorbed in bentonite, enhancing the hydrogen bond network and improving viscoelasticity. The sulfonamide groups are electronegative, forming electrostatic forces with bentonite, causing the system's network structure to recombine under high shear conditions due to the influence of hydrogen bonds and electrostatic forces, thereby improving shear resistance. Furthermore, when fracturing fluid is formulated using seawater, the sulfonamide groups in the modified guar gum / bentonite composite have the ability to coordinate with metal ions, resulting in better thickening effects.

[0026] By adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0027] 1. The thickener prepared by this invention has the functions of temperature resistance, salt resistance, and shear resistance, and can be applied to more fracturing construction sites.

[0028] 2. The thickener prepared by this invention can be quickly dispersed in water and has good fluidity. After being made into fracturing fluid, it is not easy for it to separate or precipitate, thus reducing on-site construction time and transportation costs.

[0029] 3. The thickener prepared by this invention has high viscosity, requires less dosage, and breaks down quickly, which greatly reduces the risk of formation pores being blocked by residue after fracturing fluid flowback. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0031] Example 1: A temperature-resistant thickener for fracturing, wherein the preparation method of the temperature-resistant thickener is as follows:

[0032] S1. Add bentonite to anhydrous toluene and ultrasonically disperse for 7 min. Add phenyltrimethoxysilane and react at 75 °C for 9 h to modify aromatic ring groups on the surface of bentonite. After the reaction is complete, centrifuge and filter, wash with anhydrous toluene and ethanol in sequence, and dry to obtain silane-modified bentonite.

[0033] S2. Silane-modified bentonite was added to dichloromethane and ultrasonically dispersed for 4 min to obtain a suspension. Chlorosulfonic acid was added to the suspension under ice bath conditions, and nitrogen gas was introduced for protection. The mixture was stirred at room temperature for 4.5 h to allow the aromatic ring groups on the surface of the silane-modified bentonite to react with chlorosulfonic acid to generate sulfonic acid groups. Chlorinating agent thionyl chloride and catalyst N,N-dimethylformamide were added, and the temperature was raised to 35°C to continue the reaction for 6 h. After the reaction was completed, the mixture was quenched in an ice bath, and nitrogen gas was introduced for 20 min to remove byproducts. The mixture was centrifuged and filtered, washed with dichloromethane, and then dried with anhydrous sodium sulfate to obtain modified bentonite containing sulfonyl chloride groups. The bentonite was then stored in a dry and sealed environment.

[0034] S3. Place guar gum in deionized water and stir for 25 min. Adjust the pH to 5.5 with 3% hydrochloric acid solution. Add N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, heat to 65℃, and stir for 3.5 h. After the reaction, cool to room temperature to obtain a mixed solution. Add modified bentonite containing sulfonyl chloride group and triethylamine to tetrahydrofuran and stir for 20 min to disperse evenly to obtain a dispersion. Add the dispersion to the mixed solution, heat to 45℃ and react for 7 h. After the reaction, centrifuge and filter. Wash the product three times with anhydrous ethanol and vacuum dry to obtain the modified guar gum / bentonite composite, i.e., the heat-resistant thickener.

[0035] The amount of phenyltrimethoxysilane added in S1 is 6% of the mass of bentonite.

[0036] The ratio of bentonite to anhydrous toluene in S1 is 1g:8ml, and the ultrasonic frequency is 50kHz.

[0037] The bentonite in S1 has a particle size of 500 mesh; the drying temperature is 65℃ and the drying time is 7.5h.

[0038] The ratio of silane-modified bentonite to dichloromethane in S2 is 1g:8ml, and the ultrasonic frequency is 50kHz.

[0039] The ice bath in S2 is at 2°C; the molar ratio of the silane-modified bentonite, chlorosulfonic acid, and thionyl chloride is 1:2.5:3.5, and the addition rate of chlorosulfonic acid is 8 ml / min.

[0040] The amount of catalyst N,N-dimethylformamide added in S2 is 3% of the mass of silane-modified bentonite.

[0041] The amount of N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane added in S3 is 4% of the mass of guar gum; the mass ratio of guar gum to deionized water is 1:25.

[0042] The mass ratio of modified bentonite containing sulfonyl chloride groups to guar gum in S3 is 8:13.

[0043] The amount of triethylamine added in S3 is 1.4 times the molar amount of sulfonyl chloride groups in the modified bentonite containing sulfonyl chloride groups.

[0044] The ratio of modified bentonite containing sulfonyl chloride groups and tetrahydrofuran in S3 is 1g:13ml.

[0045] The addition rate of the dispersion to the mixture in S3 is 35 ml / min.

[0046] The vacuum drying process in step S3 is carried out at a temperature of 65°C for 7 hours.

[0047] Example 2: A temperature-resistant thickener for fracturing, wherein the preparation method of the temperature-resistant thickener is as follows:

[0048] S1. Add bentonite to anhydrous toluene and ultrasonically disperse for 5 min. Add phenyltrimethoxysilane and react at 70 °C for 8 h to modify aromatic ring groups on the surface of bentonite. After the reaction is completed, centrifuge and filter, wash with anhydrous toluene and ethanol in sequence, and dry to obtain silane-modified bentonite.

[0049] S2. Silane-modified bentonite was ultrasonically dispersed in dichloromethane for 3 min to obtain a suspension. Chlorosulfonic acid was added to the suspension under ice bath conditions, and nitrogen gas was introduced for protection. The mixture was stirred at room temperature for 4 h to allow the aromatic ring groups on the surface of the silane-modified bentonite to react with chlorosulfonic acid to generate sulfonic acid groups. Chlorinating agent thionyl chloride and catalyst N,N-dimethylformamide were added, and the temperature was raised to 38℃ to continue the reaction for 5 h. After the reaction was completed, the mixture was quenched in an ice bath, and nitrogen gas was introduced for 10 min to remove byproducts. The mixture was centrifuged and filtered, washed with dichloromethane, and then dried with anhydrous sodium sulfate to obtain modified bentonite containing sulfonyl chloride groups. The bentonite was then stored in a dry and sealed environment.

[0050] S3. Place guar gum in deionized water and stir for 20 min. Adjust the pH to 5 with 2% hydrochloric acid solution. Add N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, heat to 60℃, and stir for 3 h. After the reaction, cool to room temperature to obtain a mixed solution. Add modified bentonite containing sulfonyl chloride group and triethylamine to tetrahydrofuran and stir for 15 min to disperse evenly to obtain a dispersion. Add the dispersion to the mixed solution, heat to 40℃ and react for 6 h. After the reaction, centrifuge and filter. Wash the product twice with anhydrous ethanol and vacuum dry to obtain the modified guar gum / bentonite composite, i.e., the heat-resistant thickener.

[0051] The amount of phenyltrimethoxysilane added in S1 is 5% of the mass of bentonite.

[0052] The ratio of bentonite to anhydrous toluene in S1 is 1g:7ml, and the ultrasonic frequency is 70kHz.

[0053] The bentonite in S1 has a particle size of 500 mesh; the drying temperature is 60℃ and the drying time is 8 hours.

[0054] The ratio of silane-modified bentonite to dichloromethane in S2 is 1g:7ml, and the ultrasonic frequency is 70kHz.

[0055] The ice bath in S2 is at 0°C; the molar ratio of the silane-modified bentonite, chlorosulfonic acid, and thionyl chloride is 1:2:3, and the addition rate of chlorosulfonic acid is 5 ml / min.

[0056] The amount of catalyst N,N-dimethylformamide added in S2 is 2% of the mass of silane-modified bentonite.

[0057] The amount of N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane added in S3 is 3% of the mass of guar gum; the mass ratio of guar gum to deionized water is 1:20.

[0058] The mass ratio of modified bentonite containing sulfonyl chloride groups to guar gum in S3 is 7:12.

[0059] The amount of triethylamine added in S3 is 1.2 times the molar amount of sulfonyl chloride groups in the modified bentonite containing sulfonyl chloride groups.

[0060] The ratio of modified bentonite containing sulfonyl chloride groups to tetrahydrofuran in S3 is 1g:12ml.

[0061] The addition rate of the dispersion to the mixture in S3 is 30 ml / min.

[0062] The vacuum drying process in S3 is carried out at a temperature of 60°C for 8 hours.

[0063] Example 3: A temperature-resistant thickener for fracturing, wherein the preparation method of the temperature-resistant thickener is as follows:

[0064] S1. Add bentonite to anhydrous toluene and ultrasonically disperse for 10 min. Add phenyltrimethoxysilane and react at 80 °C for 10 h to modify aromatic ring groups on the surface of bentonite. After the reaction is completed, centrifuge and filter, wash with anhydrous toluene and ethanol in sequence, and dry to obtain silane-modified bentonite.

[0065] S2. Silane-modified bentonite was added to dichloromethane and ultrasonically dispersed for 5 min to obtain a suspension. Chlorosulfonic acid was added to the suspension under ice bath conditions, and nitrogen gas was introduced for protection. The mixture was stirred at room temperature for 4.5 h to allow the aromatic ring groups on the surface of the silane-modified bentonite to react with chlorosulfonic acid to generate sulfonic acid groups. Chlorinating agent thionyl chloride and catalyst N,N-dimethylformamide were added, and the temperature was raised to 30℃ to continue the reaction for 7 h. After the reaction was completed, the mixture was quenched in an ice bath, and nitrogen gas was introduced for 15 min to remove byproducts. The mixture was centrifuged and filtered, washed with dichloromethane, and then dried with anhydrous sodium sulfate to obtain modified bentonite containing sulfonyl chloride groups. The bentonite was then stored in a dry and sealed environment.

[0066] S3. Place guar gum in deionized water and stir for 30 min. Adjust the pH to 6 with 4% hydrochloric acid solution. Add N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, heat to 70℃, and stir for 4 h. After the reaction is complete, cool to room temperature to obtain a mixed solution. Add modified bentonite containing sulfonyl chloride group and triethylamine to tetrahydrofuran and stir for 30 min to disperse evenly to obtain a dispersion. Add the dispersion to the mixed solution, heat to 50℃ and react for 8 h. After the reaction is complete, centrifuge and filter. Wash the product three times with anhydrous ethanol and vacuum dry to obtain the modified guar gum / bentonite composite, i.e., the heat-resistant thickener.

[0067] The amount of phenyltrimethoxysilane added in S1 is 7% of the mass of bentonite.

[0068] The ratio of bentonite to anhydrous toluene in S1 is 1g:10ml, and the ultrasonic frequency is 40kHz.

[0069] The bentonite in S1 has a particle size of 500 mesh; the drying temperature is 70℃ and the drying time is 8 hours.

[0070] The ratio of silane-modified bentonite to dichloromethane in S2 is 1g:10ml, and the ultrasonic frequency is 40kHz.

[0071] The ice bath in S2 is at 0°C; the molar ratio of the silane-modified bentonite, chlorosulfonic acid, and thionyl chloride is 1:3:4, and the addition rate of chlorosulfonic acid is 12 ml / min.

[0072] The amount of catalyst N,N-dimethylformamide added in S2 is 4% of the mass of silane-modified bentonite.

[0073] The amount of N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane added in S3 is 5% of the mass of guar gum; the mass ratio of guar gum to deionized water is 1:30.

[0074] The mass ratio of modified bentonite containing sulfonyl chloride groups to guar gum in S3 is 9:14.

[0075] The amount of triethylamine added in S3 is 1.5 times the molar amount of sulfonyl chloride groups in the modified bentonite containing sulfonyl chloride groups.

[0076] The ratio of modified bentonite containing sulfonyl chloride groups and tetrahydrofuran in S3 is 1g:14ml.

[0077] The addition rate of the dispersion to the mixture in S3 is 40 ml / min.

[0078] The vacuum drying process in S3 is carried out at a temperature of 70°C for 6 hours.

[0079] Example 4: A temperature-resistant thickener for fracturing, wherein the preparation method of the temperature-resistant thickener is as follows:

[0080] S1. Add bentonite to anhydrous toluene and ultrasonically disperse for 6 min. Add phenyltrimethoxysilane and react at 75 °C for 10 h to modify aromatic ring groups on the surface of bentonite. After the reaction is completed, centrifuge and filter, wash with anhydrous toluene and ethanol in sequence, and dry to obtain silane-modified bentonite.

[0081] S2. Silane-modified bentonite was added to dichloromethane and ultrasonically dispersed for 5 min to obtain a suspension. Chlorosulfonic acid was added to the suspension under ice bath conditions, and nitrogen gas was introduced for protection. The mixture was stirred at room temperature for 4.5 h to allow the aromatic ring groups on the surface of the silane-modified bentonite to react with chlorosulfonic acid to generate sulfonic acid groups. Chlorinating agent thionyl chloride and catalyst N,N-dimethylformamide were added, and the temperature was raised to 35°C to continue the reaction for 6 h. After the reaction was completed, the mixture was quenched in an ice bath, and nitrogen gas was introduced for 15 min to remove byproducts. The mixture was centrifuged and filtered, washed with dichloromethane, and then dried with anhydrous sodium sulfate to obtain modified bentonite containing sulfonyl chloride groups. The bentonite was then stored in a dry and sealed environment.

[0082] S3. Place guar gum in deionized water and stir for 30 min. Adjust the pH to 6 with 3% hydrochloric acid solution. Add N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, heat to 70℃, and stir for 3.5 h. After the reaction, cool to room temperature to obtain a mixed solution. Add modified bentonite containing sulfonyl chloride group and triethylamine to tetrahydrofuran and stir for 30 min to disperse evenly to obtain a dispersion. Add the dispersion to the mixed solution, heat to 50℃ and react for 8 h. After the reaction, centrifuge and filter. Wash the product three times with anhydrous ethanol and vacuum dry to obtain the modified guar gum / bentonite composite, i.e., the heat-resistant thickener.

[0083] The amount of phenyltrimethoxysilane added in S1 is 6% of the mass of bentonite.

[0084] The ratio of bentonite to anhydrous toluene in S1 is 1g:8ml, and the ultrasonic frequency is 50kHz.

[0085] The bentonite in S1 has a particle size of 500 mesh; the drying temperature is 65℃ and the drying time is 7.5h.

[0086] The ratio of silane-modified bentonite to dichloromethane in S2 is 1g:8ml, and the ultrasonic frequency is 50kHz.

[0087] The ice bath in S2 is at 2°C; the molar ratio of the silane-modified bentonite, chlorosulfonic acid, and thionyl chloride is 1:2.5:4, and the addition rate of chlorosulfonic acid is 8 ml / min.

[0088] The amount of catalyst N,N-dimethylformamide added in S2 is 3% of the mass of silane-modified bentonite.

[0089] The amount of N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane added in S3 is 3.5% of the mass of guar gum; the mass ratio of guar gum to deionized water is 1:25.

[0090] The mass ratio of modified bentonite containing sulfonyl chloride groups to guar gum in S3 is 8:13.

[0091] The amount of triethylamine added in S3 is 1.4 times the molar amount of sulfonyl chloride groups in the modified bentonite containing sulfonyl chloride groups.

[0092] The ratio of modified bentonite containing sulfonyl chloride groups and tetrahydrofuran in S3 is 1g:13ml.

[0093] The addition rate of the dispersion to the mixture in S3 is 35 ml / min.

[0094] The vacuum drying process in step S3 is carried out at a temperature of 65°C for 7 hours.

[0095] Comparative Example 1: A representative example 1 was selected, with N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane removed from S3, and amino-modified guar gum not used. All other aspects were the same as in Example 1, and this was used as Comparative Example 1.

[0096] Comparative Example 2: Guar gum was placed in deionized water and stirred for 25 min. The pH was adjusted to 5.5 with 3% hydrochloric acid solution. Then, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane was added. The temperature was raised to 65°C and stirred for 3.5 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a mixed solution. Bentonite was added to the mixed solution and stirred for 60 min. After filtration, the mixture was vacuum dried to obtain the guar gum / bentonite composite, i.e., the thickener.

[0097] 1g of the thickeners prepared in Examples 1-3 and Comparative Examples 1-2 were weighed and added to 300ml of seawater. The seawater had a pH of 7.2, a calcium ion content of 456.7mg / L, a magnesium ion content of 1178.4mg / L, an iron ion content of 8.4mg / L, and a strontium ion content of 22.6mg / L. The viscosity (mPa·s) was tested at 25℃ and a rotation speed of 300r / min for different times. The test results are shown in Table 1.

[0098] Table 1

[0099]

[0100] The thickeners prepared in Examples 1-3 and Comparative Examples 1-2 were formulated into fracturing fluid systems. By weight percentage, the fracturing fluid system contained 0.2% thickener, 0.35% organoboron crosslinking agent, 0.5% Lanxin LX-2009 drainage aid, 0.02% bactericide, 0.8% anti-swelling agent, 0.2% clay stabilizer, and the remainder was seawater.

[0101] The seawater had a pH of 7.2, a calcium ion content of 456.7 mg / L, a magnesium ion content of 1178.4 mg / L, an iron ion content of 8.4 mg / L, and a strontium ion content of 22.6 mg / L.

[0102] The fracturing fluid system is prepared as follows: the thickener, organoboron crosslinking agent, Lanxin LX-2009 drainage aid, bactericide, anti-swelling agent, clay stabilizer and seawater are mixed evenly and left to stand in a 30°C constant temperature water bath until the mixture can be lifted with a glass rod, thus obtaining the fracturing fluid system.

[0103] The performance of the fracturing fluid system was tested according to SY / T6376-2008. Then, 0.04% of the fracturing fluid breaker was added to the fracturing fluid system and the system was broken up at 120℃ for 1 hour. The specific results are shown in Table 2.

[0104] Table 2

[0105]

[0106] As can be seen from Tables 1 and 2, the temperature-resistant thickeners prepared using Examples 1-3 have a fast tack-up speed, high viscosity, and excellent salt resistance, temperature resistance, and shear resistance.

[0107] Comparative Example 1, which does not use amino-modified guar gum, has modified bentonite with sulfonyl chloride groups that can react with some of the hydroxyl groups in guar gum to generate sulfonate groups. This can also improve the dispersibility of bentonite in seawater fracturing fluid and the salt resistance of the thickener. Therefore, the fracturing fluid system prepared in Comparative Example 1 is less prone to stratification. However, the sulfonate groups cannot coordinate with ions in seawater, so the viscosity is lower than that of Example 1. Furthermore, the stability of the sulfonate groups is worse than that of the sulfonamide groups, so the temperature and shear resistance is worse than that of Example 1.

[0108] Comparative Example 2, without modifying the bentonite, was physically mixed with amino-modified guar gum. The viscosity in seawater was significantly lower than that in Example 1. The salt resistance, temperature resistance, and shear resistance were significantly insufficient. Furthermore, due to the influence of ions in seawater, the fracturing fluid prepared in this example showed stratification after standing for 30 minutes.

[0109] Unless otherwise specified, all proportions and percentages mentioned in this invention are mass proportions and mass percentages; all raw materials are commercially available.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A temperature-resistant thickener for fracturing, characterized in that, The preparation method of the temperature-resistant thickener is as follows: S1. Add bentonite to anhydrous toluene and ultrasonically disperse for 5-10 min. Add phenyltrimethoxysilane and react at 70-80℃ for 8-10 h. After the reaction is complete, centrifuge and filter, wash with anhydrous toluene and ethanol in sequence, and dry to obtain silane-modified bentonite. S2. Add silane-modified bentonite to dichloromethane and ultrasonically disperse for 3-5 min to obtain a suspension. Under ice bath conditions, add chlorosulfonic acid to the suspension, purge with nitrogen for protection, and stir at room temperature for 4-5 h. Then add chlorinating agent thionyl chloride and catalyst N,N-dimethylformamide, raise the temperature to 30-38℃ and continue the reaction for 5-7 h. After the reaction is completed, quench in an ice bath, purge with nitrogen for 10-20 min to remove byproducts, centrifuge and filter, wash with dichloromethane and dry with anhydrous sodium sulfate to obtain modified bentonite containing sulfonyl chloride groups. Store in a dry and sealed environment. S3. Place guar gum in deionized water and stir for 20-30 min. Adjust the pH to 5-6 with 2-4% hydrochloric acid solution. Add N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane and heat to 60-70℃. Keep the temperature and stir for 3-4 h. After the reaction is complete, cool to room temperature to obtain a mixed solution. Add modified bentonite containing sulfonyl chloride group and triethylamine to tetrahydrofuran and stir for 15-30 min to disperse evenly to obtain a dispersion. Add the dispersion to the mixed solution and heat to 40-50℃ to react for 6-8 h. After the reaction is complete, centrifuge and filter. Wash the product 2-3 times with anhydrous ethanol and vacuum dry to obtain the modified guar gum / bentonite composite, i.e., the heat-resistant thickener. The amount of phenyltrimethoxysilane added in S1 is 5-7% of the mass of bentonite; The molar ratio of silane-modified bentonite, chlorosulfonic acid and thionyl chloride in S2 is 1:2-3:3-4; The amount of N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane added in S3 is 3-5% of the mass of guar gum; The mass ratio of the modified bentonite containing sulfonyl chloride groups to guar gum in S3 is 7-9:12-14; The amount of triethylamine added in S3 is 1.2 to 1.5 times the molar amount of sulfonyl chloride groups in the modified bentonite containing sulfonyl chloride groups.

2. The temperature-resistant thickener for fracturing according to claim 1, characterized in that, The ratio of bentonite to anhydrous toluene in S1 is 1g:7-10ml, and the ultrasonic frequency is 40-70kHz.

3. The temperature-resistant thickener for fracturing according to claim 1, characterized in that, The drying temperature in S1 is 60-70℃, and the drying time is 7-8 hours.

4. The temperature-resistant thickener for fracturing according to claim 1, characterized in that, The ratio of silane-modified bentonite to dichloromethane in S2 is 1:7g~10ml, and the ultrasonic frequency is 40~70kHz.

5. The temperature-resistant thickener for fracturing according to claim 1, characterized in that, The ice bath in S2 is at 0–5°C; the chlorosulfonic acid is added at a rate of 5–12 ml / min.

6. The temperature-resistant thickener for fracturing according to claim 1, characterized in that, The amount of catalyst N,N-dimethylformamide added in S2 is 2 to 4% of the mass of silane-modified bentonite.

7. The temperature-resistant thickener for fracturing according to claim 1, characterized in that, The mass ratio of guar gum to deionized water in S3 is 1:20-30.

8. The temperature-resistant thickener for fracturing according to claim 1, characterized in that, The ratio of modified bentonite containing sulfonyl chloride groups and tetrahydrofuran in S3 is 1g:12-14ml.

9. The temperature-resistant thickener for fracturing according to claim 1, characterized in that, The addition rate of the dispersion to the mixture in S3 is 30-40 ml / min.

10. The temperature-resistant thickener for fracturing according to claim 1, characterized in that, The vacuum drying in S3 is performed at a temperature of 60–70°C for 6–8 hours.

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