Dry powder thickening agent for fracturing as well as preparation method and application of dry powder thickening agent

Abstract

The invention belongs to the technical field of oil exploitation, and particularly relates to a dry powder thickening agent for fracturing as well as a preparation method and application thereof. The thickening agent comprises the following components: (a) 1-vinyl-2-pyrrolidone; (b) a di [2-(methacryloyloxy) ethyl] phosphate ester; (c) 2-(perfluorohexyl) ethyl methacrylate; (d) 4, 4 '-diaminostilbene-2, 2'-disulfonic acid; (e) an initiator; based on 1 mole part of 1-vinyl-2-pyrrolidone, the dosages of the di [2-(methacryloyloxy) ethyl] phosphate ester, the 2-(perfluorohexyl) ethyl methacrylate and the 4, 4 '-diaminostilbene-2, 2'-disulfonic acid are 0.05 to 0.1 mole part, 0.1 to 1 mole part and 0.2 to 0.5 mole part respectively, and the dosages of the di [2-(methacryloyloxy) ethyl] phosphate ester, the 2-(perfluorohexyl) ethyl methacrylate and the 4, 4 '-diaminostilbene-2, 2'-disulfonic acid are respectively 0.05 to 0.1 mole part, 0.1 to 1 mole part and 0.2 to 0.5 mole part. The thickening agent has the advantages of high apparent viscosity, high shear resistance, temperature resistance and high resistance reduction rate, and the resistance reduction rate reaches 70% or above.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to a dry powder thickener for fracturing, its preparation method, and its application. Background Technology

[0002] Most oil and gas reservoirs (such as shale and tight sandstone) are too dense, with extremely low porosity and permeability, preventing oil and gas from flowing naturally and effectively into the wellbore. Fracturing technology artificially creates and expands numerous fractures by injecting high-pressure fluids into the formation, maximizing the reservoir's conductivity and thus increasing oil and gas production.

[0003] As the main component of water-based fracturing fluids, thickeners play a crucial role in efficiently carrying and spreading proppant. The viscoelastic fluid they form suspends and transports proppant over long distances, ensuring its uniform distribution within the fracture and creating stable, highly conductive channels. Simultaneously, they effectively create fractures and reduce filtration loss. The high-viscosity liquid efficiently expands fractures and forms a filter cake on the fracture wall, minimizing fluid loss and preserving fracture morphology. Furthermore, thickeners significantly reduce pipeline friction, enabling high-volume pumping and allowing for temporary plugging and redirection in complex formations, improving the targeted nature of fracturing. In conclusion, the comprehensive modification of fluid properties by thickeners is key to successful fracturing operations.

[0004] Currently, fracturing fluid thickeners are mainly natural polymers such as guar gum, hydroxypropyl guar gum, carboxymethyl guar gum, and coumarin. The properties and yield of these thickeners are greatly affected by the environment and place of origin. Another type of synthetic thickener is mainly polyacrylamide and its modified products, which have relatively stable performance, but have the disadvantage of poor shear resistance.

[0005] CN1073194A discloses a fracturing fluid thickener suitable for fracturing operations in low-permeability oil and gas reservoirs. It is prepared by chemically modifying the herbaceous plant *Gynostemma pentaphyllum* powder with ethanol, caustic soda, propylene oxide, and water. However, this fracturing fluid thickener has a high residue content and poor temperature resistance.

[0006] CN104073237A provides a high-temperature resistant ground crosslinking acid solution. By weight percentage, the acid solution comprises the following components: 15wt%-28wt% acid, 0.4wt%-1.0wt% polyacrylamide polymer, 0.1wt%-0.5wt% aldehyde crosslinking agent, 0.05wt%-0.25wt% phenolic crosslinking agent, 0.005wt%-0.02wt% crosslinking accelerator, 0.5wt%-2.0wt% corrosion inhibitor, 0.5wt%-2.0wt% iron ion stabilizer, 0.01wt%-0.1wt% ammonium persulfate, and the balance being water; wherein the acid is calculated as a pure substance. This invention uses low-toxicity, inexpensive industrial raw materials as crosslinking agents and crosslinking accelerators, which can reduce the toxicity of crosslinking agents, prepare a high-temperature resistant ground crosslinking acid solution, and has strong on-site operability. However, the technical solution in this patent document requires a large total amount of crosslinking agent and can only withstand high temperatures of 120°C, which does not meet the temperature resistance requirements of some deeper reservoirs. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by providing a dry powder thickener for fracturing, its preparation method, and its application. The thickener of this invention has advantages such as high apparent viscosity, strong shear resistance, temperature resistance, and high drag reduction rate, achieving a drag reduction rate of 70% or higher.

[0008] One objective of this invention is to disclose a dry powder thickener for fracturing, the thickener comprising: (a) 1-Vinyl-2-pyrrolidone; (b) Di[2-(methacryloyloxy)ethyl]phosphate; (c) 2-(perfluorohexyl)ethyl methacrylate; (d) 4,4'-Diaminostilbene-2,2'-disulfonic acid; (e) Initiator; Based on 1 mole of 1-vinyl-2-pyrrolidone, the amounts of di[2-(methacryloyloxy)ethyl]phosphate, 2-(perfluorohexyl)ethyl methacrylate, and 4,4'-diaminostilbene-2,2'-disulfonic acid are 0.05-0.1 moles, 0.1-1 moles, and 0.2-0.5 moles, respectively.

[0009] Preferably, the initiator is a mixed solution of persulfate and sodium bisulfite, wherein the concentration of persulfate is 8-10 wt% and the concentration of sodium bisulfite is 3-5 wt%.

[0010] More preferably, the persulfate is one of potassium persulfate, ammonium persulfate, and sodium persulfate.

[0011] Preferably, the weight ratio of the initiator to 1-vinyl-2-pyrrolidone is 0.4-0.6:1.

[0012] Another objective of this invention is to disclose a method for preparing the aforementioned dry powder thickener for fracturing, the specific steps of which are as follows: (1) Add 1-vinyl-2-pyrrolidone, di[2-(methacryloyloxy)ethyl] phosphate, 2-(perfluorohexyl)ethyl methacrylate, 4,4'-diaminostilbene-2,2'-disulfonic acid, TX-10 (nonylphenol polyoxyethylene ether), carboxymethyl cellulose, potassium dihydrogen phosphate, and water to the reactor in sequence. Purge with nitrogen for 5-10 minutes to remove air, and start stirring until all raw materials are completely formed into a homogeneous emulsion. Adjust the pH value to 7-8. (2) Add the initiator to the high-level dripping tank and slowly add it to the reactor. The viscosity of the liquid in the reactor gradually increases. Continue stirring for 20-30 minutes, heat to 70-80℃, keep the temperature for 40-60 minutes, adjust the pH value to 7-7.5, and cool down to below 40℃. (3) Add the above mixture to ethanol, precipitate solid, filter, dry and grind to obtain the dry powder thickener.

[0013] Preferably, in step (1), the weight ratio of TX-10, carboxymethyl cellulose, potassium dihydrogen phosphate, water and 1-vinyl-2-pyrrolidone is 0.05-0.2:0.05-0.2:0.05-0.1:6-10:1.

[0014] The third objective of this invention is to disclose the application of the above-mentioned thickener in oil and gas reservoir fracturing.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: The thickener of the present invention is a quaternary polymer with 1-vinyl-2-pyrrolidone, di[2-(methacryloyloxy)ethyl]phosphate, 2-(perfluorohexyl)ethyl methacrylate, and 4,4'-diaminostilbene-2,2'-disulfonic acid as monomers. 1-Vinyl-2-pyrrolidone is a rigid monomer with shear resistance, acid and alkali resistance, high temperature resistance, and chemical stability. Di[2-(methacryloyloxy)ethyl]phosphate contains two double bonds, which have cross-linking properties, converting the entire molecule into a network structure, increasing the molecular weight, increasing the apparent viscosity of the fracturing fluid, and thus improving the fracturing effect. 2-(perfluorohexyl)ethyl methacrylate has polyfluorinated lipophilic groups, which can significantly reduce frictional resistance, reduce the resistance of the fracturing fluid during migration, and reduce energy consumption. 4,4'-Diaminostilbene-2,2'-disulfonic acid is a polysulfonic acid surfactant that can significantly reduce the oil-water interfacial tension and frictional resistance, and improve oil displacement efficiency during fracturing.

[0016] The thickener of this invention has a high apparent viscosity; a 1500 mg / L solution can achieve an apparent viscosity of 285 mPa·s. The thickener also exhibits high shear resistance; a 1500 mg / L solution at 60°C can withstand shear stresses of up to 285 mPa·s in 100 seconds. -1 Under the condition of continuous shearing for 4 hours, the apparent viscosity can reach 255 mPa•s; the thickener of the present invention has high temperature resistance, and the apparent viscosity of a 1500 mg / L solution placed in an oven at 150°C for 24 hours can reach 277 mPa•s; the thickener of the present invention has a good drag reduction effect, and the drag reduction rate can reach 85%. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] Example 1: Dry powder thickener D1: (a) 0.5 mol of 1-vinyl-2-pyrrolidone; (b) 0.025 mol of bis[2-(methacryloyloxy)ethyl]phosphate; (c) 0.05 mol of 2-(perfluorohexyl)ethyl methacrylate; (d) 0.25 mol of 4,4'-diaminostilbene-2,2'-disulfonic acid; (e) Initiator 22.2g; Preparation of dry powder thickener D1: (1) Add 0.5 mol 1-vinyl-2-pyrrolidone, 0.025 mol di[2-(methacryloyloxy)ethyl] phosphate, 0.05 mol 2-(perfluorohexyl)ethyl methacrylate, 0.25 mol 4,4'-diaminostilbene-2,2'-disulfonic acid, 2.78 g TX-10, 7.84 g carboxymethyl cellulose, 2.78 g potassium dihydrogen phosphate, and 333 g water to the reactor in sequence. Purge with nitrogen for 5 min to remove air, and start stirring until all raw materials are completely homogeneous emulsions. Adjust the pH value to 7-8 with sodium hydroxide solution. (2) Add 22.2g of initiator to the high-level dripping tank. The initiator contains 9wt% potassium persulfate and 4wt% sodium bisulfite. Slowly add it to the reactor. The viscosity of the liquid in the reactor gradually increases. Continue stirring for 20min, heat to 80℃, keep the temperature for 40min, adjust the pH value to 7-7.5 with sodium hydroxide solution, and cool down to below 40℃. (3) Add the above mixture to ethanol, precipitate solid, filter, dry and grind to obtain product dry powder thickener D1.

[0019] Example 2 (a) 0.5 mol of 1-vinyl-2-pyrrolidone; (b) 0.03 mol of bis[2-(methacryloyloxy)ethyl]phosphate; (c) 0.1 mol of 2-(perfluorohexyl)ethyl methacrylate; (d) 0.22 mol of 4,4'-diaminostilbene-2,2'-disulfonic acid; (e) Initiator 26.4g; Preparation of dry powder thickener D2: (1) Add 0.5 mol 1-vinyl-2-pyrrolidone, 0.03 mol di[2-(methacryloyloxy)ethyl] phosphate, 0.1 mol 2-(perfluorohexyl)ethyl methacrylate, 0.22 mol 4,4'-diaminostilbene-2,2'-disulfonic acid, 4.16 g TX-10, 6.46 g carboxymethyl cellulose, 3.14 g potassium dihydrogen phosphate, and 389 g water to the reactor in sequence. Purge with nitrogen for 8 min to remove air, and start stirring until all raw materials are completely homogeneous emulsions. Adjust the pH value to 7-8 with sodium hydroxide solution. (2) Add 26.4g of initiator to the high-level dripping tank. The initiator contains 8wt% potassium persulfate and 3wt% sodium bisulfite. Slowly add it to the reactor. The viscosity of the liquid in the reactor gradually increases. Continue stirring for 30min. Heat to 70℃ and keep the reaction at this temperature for 60min. Adjust the pH value to 7-7.5 with sodium hydroxide solution and cool down to below 40℃. (3) Add the above mixture to ethanol, precipitate solid, filter, dry and grind to obtain product dry powder thickener D2.

[0020] Example 3: Dry powder thickener D3: (a) 0.5 mol of 1-vinyl-2-pyrrolidone; (b) 0.035 mol of bis[2-(methacryloyloxy)ethyl]phosphate; (c) 0.15 mol of 2-(perfluorohexyl)ethyl methacrylate; (d) 0.2 mol of 4,4'-diaminostilbene-2,2'-disulfonic acid; (e) Initiator 27.8g; Preparation of dry powder thickener D3: (1) Add 0.5 mol 1-vinyl-2-pyrrolidone, 0.035 mol di[2-(methacryloyloxy)ethyl] phosphate, 0.15 mol 2-(perfluorohexyl)ethyl methacrylate, 0.2 mol 4,4'-diaminostilbene-2,2'-disulfonic acid, 6.84 g TX-10, 4.17 g carboxymethyl cellulose, 3.66 g potassium dihydrogen phosphate, and 424 g water to the reactor in sequence. Purge with nitrogen for 5 min to remove air, and start stirring until all raw materials are completely homogeneous emulsions. Adjust the pH value to 7-8 with sodium hydroxide solution. (2) Add 27.8g of initiator to the high-level dripping tank. The initiator contains 10wt% potassium persulfate and 5wt% sodium bisulfite. Slowly add it to the reactor. The viscosity of the liquid in the reactor gradually increases. Continue stirring for 20min, heat to 78℃, keep the temperature for 45min, adjust the pH value to 7-7.5 with sodium hydroxide solution, and cool down to below 40℃. (3) Add the above mixture to ethanol, precipitate solid, filter, dry and grind to obtain the dry powder thickener D3.

[0021] Example 4: Dry powder thickener D4: (a) 0.5 mol of 1-vinyl-2-pyrrolidone; (b) 0.04 mol of bis[2-(methacryloyloxy)ethyl]phosphate; (c) 0.2 mol of 2-(perfluorohexyl)ethyl methacrylate; (d) 0.18 mol of 4,4'-diaminostilbene-2,2'-disulfonic acid; (e) Initiator 30.3g; Preparation of dry powder thickener D4: (1) Add 0.5 mol 1-vinyl-2-pyrrolidone, 0.04 mol di[2-(methacryloyloxy)ethyl] phosphate, 0.2 mol 2-(perfluorohexyl)ethyl methacrylate, 0.18 mol 4,4'-diaminostilbene-2,2'-disulfonic acid, 7.96 g TX-10, 2.78 g carboxymethyl cellulose, 3.98 g potassium dihydrogen phosphate, and 468 g water to the reactor in sequence. Purge with nitrogen for 5 min to remove air, and start stirring until all raw materials are completely homogeneous emulsions. Adjust the pH value to 7-8 with sodium hydroxide solution. (2) Add 30.3g of initiator to the high-level dripping tank. The initiator contains 9wt% ammonium persulfate and 4wt% sodium bisulfite. Slowly add it to the reactor. The viscosity of the liquid in the reactor gradually increases. Continue stirring for 25min, heat to 75℃, keep the temperature for 50min, adjust the pH value to 7-7.5 with sodium hydroxide solution, and cool down to below 40℃. (3) Add the above mixture to ethanol, precipitate solid, filter, dry and grind to obtain the dry powder thickener D4.

[0022] Example 5: Dry powder thickener D5: (a) 0.5 mol of 1-vinyl-2-pyrrolidone; (b) 0.045 mol of bis[2-(methacryloyloxy)ethyl]phosphate; (c) 0.3 mol of 2-(perfluorohexyl)ethyl methacrylate; (d) 0.15 mol of 4,4'-diaminostilbene-2,2'-disulfonic acid; (e) Initiator 31g; Preparation of dry powder thickener D5: (1) Add 0.5 mol 1-vinyl-2-pyrrolidone, 0.045 mol di[2-(methacryloyloxy)ethyl] phosphate, 0.3 mol 2-(perfluorohexyl)ethyl methacrylate, 0.15 mol 4,4'-diaminostilbene-2,2'-disulfonic acid, 9.14 g TX-10, 5.96 g carboxymethyl cellulose, 4.44 g potassium dihydrogen phosphate, and 500 g water to the reactor in sequence. Purge with nitrogen for 10 min to remove air, and start stirring until all raw materials are completely homogeneous emulsions. Adjust the pH value to 7-8 with sodium hydroxide solution. (2) Add 31g of initiator to the high-level dripping tank. The initiator contains 10wt% ammonium persulfate and 4wt% sodium bisulfite. Slowly add it to the reactor. The viscosity of the liquid in the reactor gradually increases. Continue stirring for 30min, heat to 80℃, keep the temperature for 40min, adjust the pH value to 7-7.5 with sodium hydroxide solution, and cool down to below 40℃. (3) Add the above mixture to ethanol, precipitate solid, filter, dry and grind to obtain the dry powder thickener D5.

[0023] Example 6: Dry powder thickener D6: (a) 0.5 mol of 1-vinyl-2-pyrrolidone; (b) 0.05 mol of bis[2-(methacryloyloxy)ethyl]phosphate; (c) 0.4 mol of 2-(perfluorohexyl)ethyl methacrylate; (d) 0.12 mol of 4,4'-diaminostilbene-2,2'-disulfonic acid; (e) Initiator 32.2g; Preparation of dry powder thickener D6: (1) Add 0.5 mol 1-vinyl-2-pyrrolidone, 0.05 mol di[2-(methacryloyloxy)ethyl] phosphate, 0.4 mol 2-(perfluorohexyl)ethyl methacrylate, 0.12 mol 4,4'-diaminostilbene-2,2'-disulfonic acid, 10.35 g TX-10, 9.34 g carboxymethyl cellulose, 4.96 g potassium dihydrogen phosphate, and 524 g water to the reactor in sequence. Purge with nitrogen for 8 min to remove air, and start stirring until all raw materials are completely homogeneous emulsions. Adjust the pH value to 7-8 with sodium hydroxide solution. (2) Add 32.2g of initiator to the high-level dripping tank. The initiator contains 10wt% sodium persulfate and 4wt% sodium bisulfite. Slowly add it to the reactor. The viscosity of the liquid in the reactor gradually increases. Continue stirring for 20min, heat to 80℃, keep the temperature for 50min, adjust the pH value to 7-7.5 with sodium hydroxide solution, and cool down to below 40℃. (3) Add the above mixture to ethanol, precipitate solid, filter, dry and grind to obtain the dry powder thickener D6.

[0024] Example 7 Dry Powder Thickener D7: (a) 0.5 mol of 1-vinyl-2-pyrrolidone; (b) 0.05 mol of bis[2-(methacryloyloxy)ethyl]phosphate; (c) 0.5 mol of 2-(perfluorohexyl)ethyl methacrylate; (d) 0.1 mol of 4,4'-diaminostilbene-2,2'-disulfonic acid; (e) Initiator 33.3g; Preparation of dry powder thickener D7: (1) Add 0.5 mol 1-vinyl-2-pyrrolidone, 0.05 mol di[2-(methacryloyloxy)ethyl] phosphate, 0.5 mol 2-(perfluorohexyl)ethyl methacrylate, 0.1 mol 4,4'-diaminostilbene-2,2'-disulfonic acid, 11.1 g TX-10, 11.1 g carboxymethyl cellulose, 5.55 g potassium dihydrogen phosphate, and 555 g water to the reactor in sequence. Purge with nitrogen for 10 min to remove air, and start stirring until all raw materials are completely homogeneous emulsions. Adjust the pH value to 7-8 with sodium hydroxide solution. (2) Add 33.3g of initiator to the high-level dropping tank. The initiator contains 10wt% sodium persulfate and 4wt% sodium bisulfite. Slowly add it to the reactor. The viscosity of the liquid in the reactor gradually increases. Continue stirring for 30min, heat to 70℃, keep the temperature for 60min, adjust the pH value to 7-7.5 with sodium hydroxide solution, and cool down to below 40℃. (3) Add the above mixture to ethanol, precipitate solid, filter, dry and grind to obtain the dry powder thickener D7.

[0025] Example 8: Test of apparent viscosity The thickener of this invention was diluted with water to a concentration of 1500 mg / L. The apparent viscosity μ0 was tested at 60°C in accordance with SY / T 6376-2008 "General Technical Conditions for Fracturing Fluids". A comparative experiment was conducted using PAM from Shengli Petrochemical Co., Ltd. The test results are shown in Table 1.

[0026] As can be seen from Table 1, when the thickener of the present invention (Examples 1-7) is used at a concentration of 1500 mg / L, the apparent viscosity at 60°C is greater than or equal to 240 mPa•s, and the highest reaches 285 mPa•s (Example 1). The apparent viscosity of the comparative example is 58 mPa•s.

[0027] Example 9 Shear resistance test The sample from Example 8 was heated at 60°C for 100 seconds. -1 Under the condition of continuous shearing for 4 hours, the apparent viscosity μ1 was tested. A comparative experiment was conducted using PAM from Shengli Petrochemical Co., Ltd. The test results are shown in Table 1.

[0028] As can be seen from Table 1, the thickener of the present invention (Examples 1-7) at 60°C for 100 seconds... -1 Under the conditions of continuous shearing for 4 hours, the apparent viscosity was greater than 220 mPa•s, reaching a maximum of 255 mPa•s (Example 1), while the apparent viscosity of the comparative example was 43 mPa•s. The thickener of the present invention has high shear resistance.

[0029] Example 10 Temperature Resistance Test The sample from Example 8 was placed in a high-pressure sealed container and placed in an oven at 150°C. After 24 hours, it was taken out, cooled to 60°C, and the apparent viscosity μ2 was tested. A comparative experiment was conducted using PAM from Shengli Petrochemical Co., Ltd. The test results are shown in Table 1.

[0030] As can be seen from Table 1, the thickeners of the present invention (Examples 1-7) were placed in an oven at 150°C for 24 hours and then cooled to 60°C. Their apparent viscosities were all greater than 230 mPa•s, with the highest reaching 277 mPa•s (Example 1). The apparent viscosity of the comparative example was 52 mPa•s. The thickeners of the present invention have high temperature resistance.

[0031] Example 11: Resistivity Test The drag reduction rate of the thickener of this invention was tested according to the method in SY / T 6376-2008 "General Technical Conditions for Fracturing Fluids". PAM from Shengli Petrochemical Co., Ltd. was used for comparative experiments. The test results are shown in Table 1.

[0032] Table 1. Test results of apparent viscosity, shear resistance, temperature resistance, and drag reduction.

[0033] As can be seen from Table 1, the drag reduction rate of the thickener of the present invention (Examples 1-7) all reached 70% or above, with the highest reaching 85% (Example 7), while the drag reduction rate of the comparative example was 56%. The thickener of the present invention has a better drag reduction effect.

[0034] In summary, the thickener of this invention has the characteristic of high apparent viscosity; the apparent viscosity of a 1500 mg / L solution can reach 285 mPa•s. The thickener of this invention also has high shear resistance; a 1500 mg / L solution at 60°C can withstand shear stresses of up to 285 mPa•s in 100 seconds. -1 Under the condition of continuous shearing for 4 hours, the apparent viscosity can reach 255 mPa•s; the thickener of the present invention has high temperature resistance, and the apparent viscosity of a 1500 mg / L solution placed in an oven at 150°C for 24 hours can reach 277 mPa•s; the thickener of the present invention has a good drag reduction effect, and the drag reduction rate can reach 85%.

[0035] Therefore, this invention can be widely applied to hydraulic fracturing of oil and gas reservoirs.

[0036] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A dry powder thickener for fracturing, characterized in that, The thickener comprises: (a) 1-Vinyl-2-pyrrolidone; (b) Di[2-(methacryloyloxy)ethyl]phosphate; (c) 2-(perfluorohexyl)ethyl methacrylate; (d) 4,4'-Diaminostilbene-2,2'-disulfonic acid; (e) Initiator; Based on 1 mole of 1-vinyl-2-pyrrolidone, the amounts of di[2-(methacryloyloxy)ethyl]phosphate, 2-(perfluorohexyl)ethyl methacrylate, and 4,4'-diaminostilbene-2,2'-disulfonic acid are 0.05-0.1 moles, 0.1-1 moles, and 0.2-0.5 moles, respectively.

2. The dry powder thickener for fracturing according to claim 1, characterized in that, The initiator is a mixed solution of persulfate and sodium bisulfite, wherein the concentration of persulfate is 8-10 wt% and the concentration of sodium bisulfite is 3-5 wt%.

3. The dry powder thickener for fracturing according to claim 1, characterized in that, The weight ratio of the initiator to 1-vinyl-2-pyrrolidone is 0.4-0.6:

1.

4. The dry powder thickener for fracturing according to claim 2, characterized in that, The persulfate mentioned is one of potassium persulfate, ammonium persulfate, and sodium persulfate.

5. A method for preparing a dry powder thickener for fracturing as described in any one of claims 1-4, characterized in that, The specific steps of the preparation method are as follows: Add 1-vinyl-2-pyrrolidone, di[2-(methacryloyloxy)ethyl] phosphate, 2-(perfluorohexyl)ethyl methacrylate, 4,4'-diaminostilbene-2,2'-disulfonic acid, TX-10 (nonylphenol polyoxyethylene ether), carboxymethyl cellulose, potassium dihydrogen phosphate, and water to the reactor in sequence. Purge with nitrogen for 5-10 minutes to remove air, and start stirring until all raw materials are completely formed into a homogeneous emulsion. Adjust the pH value to 7-8. Add the initiator to the high-level dropping tank and slowly add it to the reactor. The viscosity of the liquid in the reactor gradually increases. Continue stirring for 20-30 minutes, heat to 70-80℃, keep the temperature for 40-60 minutes, adjust the pH value to 7-7.5, and cool down to below 40℃. (3) Add the above mixture to ethanol, precipitate solid, filter, dry and grind to obtain the dry powder thickener.

6. The preparation method according to claim 5, characterized in that, In step (1), the weight ratio of TX-10, carboxymethyl cellulose, potassium dihydrogen phosphate, water and 1-vinyl-2-pyrrolidone is 0.05-0.2:0.05-0.2:0.05-0.1:6-10:

1.

7. The thickener prepared by the preparation method according to any one of claims 5 or 6.

8. The application of the thickener according to any one of claims 7 in hydraulic fracturing of oil and gas reservoirs.

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