A drag reducer for fracturing and preparation method thereof

Abstract

The present invention belongs to the field of oil extraction technology, and specifically relates to a fracturing drag reducer and a preparation method thereof. The preparation method is as follows: perfluorooctylethyl acrylate, (3-acryloxypropyl) tris(trimethylsiloxy) silane, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium] propane-1-sulfonic acid inner salt, butenedioic acid, TX-10, MS-1, carboxymethyl cellulose, buffer salt, and distilled water are sequentially added to a reactor to adjust the pH to 7-8; the reactor and pipeline are purged with nitrogen, an initiator is added dropwise to the reactor, the addition is completed, heating, insulation reaction, continued reaction, then heating, insulation reaction, cooling to below 40°C, adjusting the pH to 7-8, and obtaining a product fracturing drag reducer. The present invention has the advantages of a wide source of raw materials, a simple synthesis process, and no by-products; at the same time, the present invention has the characteristics of high apparent viscosity and high drag reduction rate.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and particularly relates to a drag reducer for fracturing and a preparation method thereof. Background Art

[0002] With the progress of society and the rapid development of the economy, oil and gas projects have become a significant part of modern industry and life. Unconventional oil and gas resources have attracted great attention both domestically and internationally. The extraction of shale gas and tight oil has become a top priority in oil and gas field development. Fracturing has gradually become the mainstream transformation technology for unconventional oil and gas reservoirs and a key technology for the economic development of low- and ultra-low-permeability oil and gas reservoirs. Currently widely used in various oil fields, it utilizes surface high-pressure pumps to pump fracturing fluid into the formation at a rate far exceeding the formation's absorption capacity. This creates fractures in the formation and extends the fractures, thereby adjusting the water absorption profile of the well and improving the recovery rate.

[0003] After the fracturing fluid is pressurized by a high-pressure pump injection device, it is pumped into the formation at high speed through the tubing string. Under these high-pressure and high-speed conditions, the fluid flows through the pipe at high turbulence. This creates significant frictional resistance between the fracturing fluid and the pipe wall, which restricts its flow through the pipe, resulting in reduced throughput and increased energy loss. Therefore, it is necessary to add a drag reducer to the fluid to reduce the impact of frictional resistance and improve construction efficiency.

[0004] Drag reducers are small amounts of high molecular weight polymers or surfactants added to liquids. These agents significantly reduce frictional resistance by affecting the turbulent structure during turbulent flow, thereby significantly reducing energy consumption and equipment requirements during the fracturing process.

[0005] CN103694984A discloses a shale gas acidizing fracturing drag reducer and a preparation method thereof. The drag reducer is prepared by an inverse emulsion method. The inverse emulsion contains a large amount of organic solvent. After the fracturing fluid drag reducer is injected into the formation, it will cause groundwater pollution and environmental damage, and fail to meet environmental protection requirements.

[0006] CN103013488A discloses a drag reducer for use in slickwater fracturing fluids and its preparation method. An organic salt is added to an aqueous solution of acrylamide and functional monomers to prepare an aqueous phase. This aqueous phase is then added to an oil phase system consisting of a surfactant and base oil under high-speed stirring to form a stable W / O microemulsion system. Nitrogen is then introduced to displace oxygen, and an initiator is added for polymerization, forming an unbranched long-chain structure. This polymer microemulsion is a transparent or translucent, thermodynamically stable system that rapidly swells in water and can be used directly. Adding a small amount of this drag reducer during fluid transport can significantly increase flow rate and reduce energy consumption. Compared to clean water, the drag reduction effect can reach 30% to 65%. This drag reducer exhibits excellent stability, rapid dissolution, good solubility, ease of use, and significant drag reduction. It is suitable for slickwater fracturing technology and has been used in field fracturing operations, achieving good production increases. However, the drag reduction rate of this drag reducer is only 30-60%, which does not meet construction requirements. Summary of the Invention

[0007] The present invention addresses the deficiencies of the prior art and provides a fracturing drag reducer and its preparation method. The present invention has the advantages of a wide range of raw material sources, a simple synthesis process, and no by-products; and also has the characteristics of high apparent viscosity and high drag reduction rate.

[0008] In order to achieve the above objectives, one of the objectives of the present invention is to disclose a drag reducer for fracturing, the molecular structure of the drag reducer for fracturing is as follows:

[0009]

[0010] in:

[0011] a=5000-50000;

[0012] b = 500-10000;

[0013] c = 250-5000;

[0014] d=125-2500.

[0015] Preferably, the viscosity average molecular weight of the drag reducer for fracturing is 10,000,000-20,000,000.

[0016] Another object of the present invention is to disclose a method for preparing the above-mentioned drag reducer for fracturing, and the specific steps of the preparation method are as follows:

[0017] (1) Add perfluorooctyl ethyl acrylate, (3-acryloxypropyl) tris(trimethylsiloxy) silane, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, butenedioic acid, TX-10 (nonylphenol polyoxyethylene ether), MS-1 (alkylphenol ether sulfosuccinate sodium salt), carboxymethyl cellulose, buffer salt, and distilled water to the reactor in sequence, and add sodium hydroxide solution while stirring to adjust the pH to 7-8;

[0018] (2) Purge the reactor and pipelines with nitrogen for 3-5 minutes, and maintain a nitrogen atmosphere throughout the synthesis. Add the initiator dropwise to the reactor. After the addition is complete, heat to 50-55°C and keep the temperature to react until the solution begins to become viscous. Continue the reaction for 20-30 minutes, then raise the temperature to 80-85°C and keep the temperature to react for 30-50 minutes. Cool the temperature to below 40°C and adjust the pH to 7-8 with sodium hydroxide solution to obtain the product fracturing drag reducer.

[0019] Preferably, the molar ratio of (3-acryloxypropyl)tris(trimethylsiloxy)silane, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, butenedioic acid and perfluorooctyl ethyl acrylate is 0.2-0.4:0.1-0.2:0.05-0.1:1.

[0020] Preferably, the weight ratio of TX-10, MS-1, carboxymethyl cellulose, buffer salt, distilled water and perfluorooctyl ethyl acrylate in step (1) is 0.2-0.4:0.1-0.2:0.2-0.4:0.1-0.2:6-8:1.

[0021] Preferably, the buffer salt in step (1) is one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0022] More preferably, the buffer salt is one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and sodium dihydrogen phosphate.

[0023] Preferably, the initiator in step (2) is a mixed solution of persulfate and sodium bisulfite, and the weight ratio of the initiator to perfluorooctyl ethyl acrylate is 0.2-0.5:1.

[0024] More preferably, the concentration of the persulfate is 8-10 wt %, and the concentration of the sodium bisulfite is 4-5 wt %.

[0025] More preferably, the persulfate is one of potassium persulfate, ammonium persulfate and sodium persulfate.

[0026] The reaction equation for the synthesis of the drag reducer for fracturing of the present invention is as follows:

[0027]

[0028] The fracturing drag reducer of the present invention is a quaternary high molecular polymer with perfluorooctyl ethyl acrylate, (3-acryloxypropyl) tris(trimethylsiloxy) silane, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt and butenedioic acid as monomers. Perfluorooctyl ethyl acrylate and (3-acryloxypropyl) tris(trimethylsiloxy) silane are special surfactant monomers with low surface tension and interfacial tension that ordinary surfactants cannot match, and can significantly reduce the friction resistance during the migration of fracturing fluids; 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt is an amphoteric surfactant monomer, and butenedioic acid can provide two carboxyl groups and is an anionic surfactant monomer, which can also significantly reduce surface tension and interfacial tension, thereby reducing the friction resistance during the migration of fracturing fluids; TX-10 and MS-1 are nonionic and anionic emulsifiers, and carboxymethyl cellulose is an emulsifying dispersant, which can improve the polymerization quality of the product, increase the molecular weight and uniformity, thereby increasing the viscosity of the product, and at the same time further enhance the drag reduction effect.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] (1) The fracturing drag reducer of the present invention is synthesized in a one-pot process, the raw materials are readily available, there are no by-products, and it is safe and environmentally friendly;

[0031] (2) The fracturing drag reducer of the present invention has a high apparent viscosity, and the apparent viscosity at a concentration of 0.4 wt% reaches above 100 mPa.s;

[0032] (3) The drag reducer for fracturing of the present invention has a good drag reduction effect, and the drag reduction rate at a concentration of 0.6 wt% reaches 75% or above. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below with reference to specific embodiments:

[0034] Example 1

[0035] (1) 0.05 mol perfluorooctylethyl acrylate, 0.01 mol (3-acryloxypropyl) tris(trimethylsilyloxy) silane, 0.01 mol 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 0.005 mol butenedioic acid, 5.18 g TX-10, 4.66 g MS-1, 5.18 g carboxymethyl cellulose, 4.16 g potassium dihydrogen phosphate, and 155.4 g distilled water were added to the reactor in sequence, and sodium hydroxide solution was added while stirring to adjust the pH to 7-8;

[0036] (2) The reactor and pipelines were purged with nitrogen for 3 minutes, and a nitrogen atmosphere was maintained throughout the synthesis. 5.18 g of an initiator containing 10 wt% potassium persulfate and 4 wt% sodium bisulfite was added dropwise to the reactor. After the addition was complete, the reactor was heated to 50°C and kept warm until the solution began to become viscous. The reaction was continued for 20 minutes, then the temperature was raised to 80°C and kept warm for 30 minutes. The temperature was then lowered to below 40°C, and the pH was adjusted to 7-8 with sodium hydroxide solution to obtain a product fracturing drag reducer.

[0037] Example 2

[0038] (1) 0.05 mol perfluorooctylethyl acrylate, 0.012 mol (3-acryloxypropyl) tris(trimethylsilyloxy) silane, 0.009 mol 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 0.005 mol butenedioic acid, 6.47 g TX-10, 2.59 g MS-1, 6.47 g carboxymethyl cellulose, 4.23 g potassium dihydrogen phosphate, and 169 g distilled water were added to the reactor in sequence, and sodium hydroxide solution was added while stirring to adjust the pH to 7-8;

[0039] (2) The reactor and pipelines were purged with nitrogen for 3 minutes, and a nitrogen atmosphere was maintained throughout the synthesis. 6.27 g of an initiator containing 8 wt% potassium persulfate and 5 wt% sodium bisulfite was added dropwise to the reactor. After the addition was complete, the reactor was heated to 55°C and kept warm until the solution began to become viscous. The reaction was continued for 30 minutes, then the temperature was raised to 85°C and kept warm for 50 minutes. The temperature was then lowered to below 40°C, and the pH was adjusted to 7-8 with sodium hydroxide solution to obtain a product fracturing drag reducer.

[0040] Example 3

[0041] (1) 0.05 mol perfluorooctylethyl acrylate, 0.014 mol (3-acryloxypropyl) tris(trimethylsilyloxy) silane, 0.008 mol 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 0.0045 mol butenedioic acid, 7.68 g TX-10, 3.77 g MS-1, 9.86 g carboxymethyl cellulose, 5.18 g dipotassium hydrogen phosphate, and 182 g distilled water were added to the reactor in sequence, and sodium hydroxide solution was added while stirring to adjust the pH to 7-8;

[0042] (2) The reactor and pipelines were purged with nitrogen for 5 minutes, and a nitrogen atmosphere was maintained throughout the synthesis. 7.86 g of an initiator containing 10 wt% potassium persulfate and 5 wt% sodium bisulfite was added dropwise to the reactor. After the addition was complete, the reactor was heated to 50°C and kept warm until the solution began to become viscous. The reaction was continued for 25 minutes, then the temperature was raised to 80°C and kept warm for 40 minutes. The temperature was then lowered to below 40°C, and the pH was adjusted to 7-8 with sodium hydroxide solution to obtain a product fracturing drag reducer.

[0043] Example 4

[0044] (1) 0.05 mol perfluorooctylethyl acrylate, 0.016 mol (3-acryloxypropyl) tris(trimethylsilyloxy) silane, 0.007 mol 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 0.0045 mol butenedioic acid, 8.19 g TX-10, 4.58 g MS-1, 7.14 g carboxymethyl cellulose, 3.66 g potassium dihydrogen phosphate, and 176 g distilled water were added to the reactor in sequence, and sodium hydroxide solution was added while stirring to adjust the pH to 7-8;

[0045] (2) The reactor and pipelines were purged with nitrogen for 5 minutes, and a nitrogen atmosphere was maintained throughout the synthesis. 9.27 g of an initiator containing 9 wt% sodium persulfate and 4 wt% sodium bisulfite was added dropwise to the reactor. After the addition was complete, the reactor was heated to 55°C and kept warm until the solution began to become viscous. The reaction was continued for 25 minutes, then the temperature was raised to 85°C and kept warm for 35 minutes. The temperature was then lowered to below 40°C, and the pH was adjusted to 7-8 with sodium hydroxide solution to obtain a product fracturing drag reducer.

[0046] Example 5

[0047] (1) 0.05 mol perfluorooctylethyl acrylate, 0.016 mol (3-acryloxypropyl) tris(trimethylsiloxy) silane, 0.006 mol 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 0.0045 mol butenedioic acid, 8.32 g TX-10, 5.18 g MS-1, 8.2 g carboxymethyl cellulose, 2.59 g sodium dihydrogen phosphate, and 174 g distilled water were added to the reactor in sequence, and sodium hydroxide solution was added while stirring to adjust the pH to 7-8;

[0048] (2) The reactor and pipelines were purged with nitrogen for 4 minutes, and a nitrogen atmosphere was maintained throughout the synthesis. 8.14 g of an initiator containing 10 wt% sodium persulfate and 4 wt% sodium bisulfite was added dropwise to the reactor. After the addition was complete, the reactor was heated to 52°C and kept warm until the solution began to become viscous. The reaction was continued for 22 minutes, then the temperature was raised to 82°C and kept warm for 45 minutes. The temperature was then lowered to below 40°C, and the pH was adjusted to 7-8 with sodium hydroxide solution to obtain a product fracturing drag reducer.

[0049] Example 6

[0050] (1) 0.05 mol perfluorooctylethyl acrylate, 0.018 mol (3-acryloxypropyl) tris(trimethylsilyloxy) silane, 0.006 mol 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 0.0035 mol butenedioic acid, 9.58 g TX-10, 4.62 g MS-1, 10.1 g carboxymethyl cellulose, 3.44 g disodium hydrogen phosphate, and 200 g distilled water were added to the reactor in sequence, and sodium hydroxide solution was added while stirring to adjust the pH to 7-8;

[0051] (2) The reactor and pipelines were purged with nitrogen for 4 minutes, and the nitrogen atmosphere was maintained throughout the synthesis. 12.95 g of an initiator containing 8 wt% sodium persulfate and 4 wt% sodium bisulfite was added dropwise to the reactor. After the addition was complete, the reactor was heated to 53°C and kept warm until the solution began to become viscous. The reaction was continued for 26 minutes, then the temperature was raised to 81°C and kept warm for 32 minutes. The temperature was then lowered to below 40°C, and the pH was adjusted to 7-8 with sodium hydroxide solution to obtain a product fracturing drag reducer.

[0052] Example 7

[0053] (1) 0.05 mol of perfluorooctylethyl acrylate, 0.018 mol of (3-acryloxypropyl)tris(trimethylsilyloxy)silane, 0.005 mol of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 0.0035 mol of butenedioic acid, 10.36 g of TX-10, 5.18 g of MS-1, 10.36 g of carboxymethyl cellulose, 4.2 g of ammonium dihydrogen phosphate, and 207.2 g of distilled water were added to the reactor in sequence, and sodium hydroxide solution was added while stirring to adjust the pH to 7-8;

[0054] (2) The reactor and pipelines were purged with nitrogen for 3 minutes, and a nitrogen atmosphere was maintained throughout the synthesis. 11.44 g of an initiator containing 10 wt% ammonium persulfate and 5 wt% sodium bisulfite was added dropwise to the reactor. After the addition was complete, the reactor was heated to 51°C and kept warm until the solution began to become viscous. The reaction was continued for 28 minutes, then the temperature was raised to 82°C and kept warm for 40 minutes. The temperature was then lowered to below 40°C, and the pH was adjusted to 7-8 with sodium hydroxide solution to obtain a product fracturing drag reducer.

[0055] Example 8

[0056] (1) 0.05 mol of perfluorooctylethyl acrylate, 0.02 mol of (3-acryloxypropyl)tris(trimethylsiloxy)silane, 0.005 mol of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 0.003 mol of butenedioic acid, 9.42 g of TX-10, 4.9 g of MS-1, 9.27 g of carboxymethyl cellulose, 4.98 g of diammonium hydrogen phosphate, and 198 g of distilled water were added to the reactor in sequence, and sodium hydroxide solution was added while stirring to adjust the pH to 7-8;

[0057] (2) The reactor and pipelines were purged with nitrogen for 5 minutes, and a nitrogen atmosphere was maintained throughout the synthesis. 10.28 g of an initiator containing 8 wt% ammonium persulfate and 5 wt% sodium bisulfite was added dropwise to the reactor. After the addition was complete, the reactor was heated to 54°C and kept warm until the solution began to become viscous. The reaction was continued for 20 minutes, then the temperature was raised to 83°C and kept warm for 36 minutes. The temperature was then lowered to below 40°C, and the pH was adjusted to 7-8 with sodium hydroxide solution to obtain a product fracturing drag reducer.

[0058] Example 9

[0059] (1) 0.05 mol perfluorooctylethyl acrylate, 0.02 mol (3-acryloxypropyl) tris(trimethylsilyloxy) silane, 0.006 mol 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 0.0025 mol butenedioic acid, 8.55 g TX-10, 4.77 g MS-1, 8.49 g carboxymethyl cellulose, 4.18 g sodium dihydrogen phosphate, and 184 g distilled water were added to the reactor in sequence, and sodium hydroxide solution was added while stirring to adjust the pH to 7-8;

[0060] (2) The reactor and pipelines were purged with nitrogen for 4 minutes, and a nitrogen atmosphere was maintained throughout the synthesis. 9.86 g of an initiator containing 8 wt% ammonium persulfate and 5 wt% sodium bisulfite was added dropwise to the reactor. After the addition was complete, the reactor was heated to 52°C and kept warm until the solution began to become viscous. The reaction was continued for 30 minutes, then the temperature was raised to 84°C and kept warm for 43 minutes. The temperature was then lowered to below 40°C, and the pH was adjusted to 7-8 with sodium hydroxide solution to obtain a product, a drag reducer for fracturing.

[0061] Example 10 Apparent viscosity test

[0062] The apparent viscosity of the drag reducer for fracturing of the present invention (Examples 1-9) was tested at a test concentration of 0.4 wt %. The test method was based on SY / T 6376-2008 "General Technical Requirements for Fracturing Fluids".

[0063] The apparent viscosity was compared using the emulsion drag reducer produced by Puyang Haizhiyuan Chemical Industry Co., Ltd. The test results are shown in Table 1.

[0064] As can be seen from Table 1, the apparent viscosity of the drag reducers for fracturing of the present invention (Examples 1-9) at a test concentration of 0.4 wt% is greater than 100 mPa.s, with the highest reaching 128 mPa.s. In the comparative experiment, the apparent viscosity of the emulsion drag reducer of Puyang Haizhiyuan Chemical Industry Co., Ltd. is 53 mPa.s, which is significantly lower than that of the present invention.

[0065] Example 11 Drag Reduction Rate Test

[0066] The drag reduction rate of the present invention was tested at concentrations of 0.2 wt%, 0.4 wt%, and 0.6 wt%. The test method was based on SY / T6376-2008 "General Technical Requirements for Fracturing Fluids".

[0067] The drag reduction rate was compared using the emulsion drag reducer produced by Puyang Haizhiyuan Chemical Industry Co., Ltd. The test results are shown in Table 1.

[0068] Table 1 Apparent viscosity and drag reduction test results

[0069]

[0070]

[0071] From Table 1 we can see that:

[0072] (1) The drag reduction rate of the fracturing drag reducer of the present invention (Examples 1-9) at a test concentration of 0.2 wt% is greater than or equal to 65%, with the highest reaching 70%. In the comparative experiment, the drag reduction rate of the emulsion drag reducer of Puyang Haizhiyuan Chemical Industry Co., Ltd. is 55%, which is significantly lower than that of the present invention;

[0073] (2) The drag reduction rate of the fracturing drag reducer of the present invention (Examples 1-9) at a test concentration of 0.4 wt% was greater than 70%, with the highest reaching 75%. In the comparative experiment, the drag reduction rate of the emulsion drag reducer of Puyang Haizhiyuan Chemical Industry Co., Ltd. was 59%, which was significantly lower than that of the present invention.

[0074] (3) The drag reduction rate of the fracturing drag reducer of the present invention (Examples 1-9) at a test concentration of 0.6wt% is greater than 75%, with the highest reaching 80%. In the comparative experiment, the drag reduction rate of the emulsion drag reducer of Puyang Haizhiyuan Chemical Industry Co., Ltd. is 62%, which is significantly lower than that of the present invention.

[0075] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a drag reducer for fracturing, characterized in that: The specific steps of the preparation method are as follows: (1) Add perfluorooctyl ethyl acrylate, (3-acryloxypropyl) tris(trimethylsiloxy) silane, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, butenedioic acid, nonylphenol polyoxyethylene ether TX-10, alkylphenol ether sulfosuccinate sodium salt MS-1, carboxymethyl cellulose, buffer salt, and distilled water to the reactor in sequence, and add sodium hydroxide solution while stirring to adjust the pH to 7-8; (2) Purge the reactor and pipelines with nitrogen for 3-5 minutes, and maintain a nitrogen atmosphere throughout the synthesis; add the initiator dropwise to the reactor, heat to 50-55°C, and keep the temperature to react until the solution begins to become viscous, continue the reaction for 20-30 minutes, then raise the temperature to 80-85°C, keep the temperature to react for 30-50 minutes, cool to below 40°C, and adjust the pH to 7-8 with sodium hydroxide solution to obtain the product fracturing drag reducer; The molar ratio of the (3-acryloxypropyl)tris(trimethylsiloxy)silane, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, butenedioic acid and perfluorooctyl ethyl acrylate is 0.2-0.4:0.1-0.2:0.05-0.1:

1.

2. The method for preparing a drag reducer for fracturing according to claim 1, characterized in that: The buffer salt in step (1) is one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

3. The method for preparing a drag reducer for fracturing according to claim 2, characterized in that: The buffer salt is one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and sodium dihydrogen phosphate.

4. The method for preparing a drag reducer for fracturing according to claim 1, characterized in that: The initiator in step (2) is a mixed solution of persulfate and sodium bisulfite, and the weight ratio of the initiator to perfluorooctyl ethyl acrylate is 0.2-0.5:

1.

5. The method for preparing a drag reducer for fracturing according to claim 4, characterized in that: The concentration of the persulfate is 8-10 wt %, and the concentration of the sodium bisulfite is 4-5 wt %.

6. The method for preparing a drag reducer for fracturing according to claim 4, characterized in that: The persulfate is one of potassium persulfate, ammonium persulfate and sodium persulfate.

7. A drag reducer for fracturing, characterized in that: The molecular structural formula of the fracturing drag reducer is as follows: in: a=5000-50000； b=500-10000； c=250-5000； d=125-2500。 8. The drag reducer for fracturing according to claim 7, characterized in that: The viscosity average molecular weight of the drag reducer for fracturing is 10,000,000-20,000,000.

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