A hydrophobic drag reducing agent and a method for preparing the same
By preparing hydrophobic drag-reducing agents to alter the wettability of rock surfaces, the problem of hydration and swelling in mudstone and shale was solved, enabling reservoir protection and efficient fracturing fluid flowback.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CNPC BOHAI DRILLING ENG
- Filing Date
- 2024-12-03
- Publication Date
- 2026-06-05
AI Technical Summary
Existing drag-reducing agents cannot effectively inhibit the hydration and swelling of mudstone and shale, leading to reservoir damage, and existing shale inhibitors are not effective in inhibiting permeability hydration and swelling.
Hydrophobic drag-reducing agents are used to modify the wettability of rock surfaces by polymerizing modified nano-silica with specific monomers, thereby reducing the possibility of water entering rock fractures and improving the flowback rate of fracturing fluid.
It effectively reduced the degree of hydration expansion in shale reservoirs, improved the flowback rate of fracturing fluid, and maintained good drag reduction performance and proppant carrying capacity.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of downhole working fluid technology, and relates to a drag-reducing agent, specifically a hydrophobic drag-reducing agent and its preparation method. Background Technology
[0002] With the increasing demand for oil and gas resources, oil and gas exploration and development are shifting towards unconventional and complex oil and gas exploration and development, such as tight oil and gas and shale oil and gas. This places increasingly higher demands on fracturing fluids in terms of reservoir protection, cost, and environmental protection. Currently, drag-reducing water is commonly used for fracturing and production enhancement operations in shale oil and gas. Drag-reducing water fracturing technology involves adding small amounts of drag-reducing agents, flow aids, and bactericides to water as fracturing fluid. The most critical component is the drag-reducing agent. Existing drag-reducing agents can only reduce the drag of the fracturing fluid and do not provide wetting reversal or reservoir protection effects. During fracturing, they can cause hydration and expansion of shale, leading to reservoir damage.
[0003] Currently, the solution to this problem is to add shale inhibitors. However, shale inhibitors mainly work by reducing permeability and hydration, and are not very effective at inhibiting the hydration and swelling of mudstone and shale. Therefore, a more effective method to inhibit the hydration and swelling of mudstone and shale needs to be found. Summary of the Invention
[0004] The purpose of this invention is to provide a hydrophobic drag-reducing agent and its preparation method to solve the problem of hydration swelling of mudstone and shale.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A hydrophobic drag reducer, the raw materials for its active ingredient, by weight, include: 15-20 parts acrylamide, 10-15 parts acrylic acid, 2-3 parts 2-acrylamido-2-methylpropanesulfonic acid, 1-2 parts modified nano silica, 0.1-0.5 parts initiator A, 0.5-1 part chelating agent, 30-40 parts white oil, 4-6 parts sorbitan oleate, 1-2 parts polyoxyethylene sorbitan oleate, and 1-2 parts initiator B.
[0007] As a limitation, the modified nano-silica is prepared by the following method: 2-4 parts by weight of nano-silica are dispersed in ethanol, 1-2 parts by weight of modifier are added, ultrasonic hydrolysis is performed, the pH value is adjusted to 3-4, 2-4 parts by weight of perfluorooctyltriethoxysilane is added to react, and the modified nano-silica is obtained after drying.
[0008] The modifier is 3-methacryloyloxypropyltrimethoxysilane or vinyltriethoxysilane.
[0009] The chemical formula for the modified nano-silica reaction is:
[0010]
[0011] As a further limitation, the ultrasonic hydrolysis is performed for 10 minutes; the reaction is carried out at a temperature of 70–80°C for 4–6 hours.
[0012] As another limitation, the initiator A includes at least one of azobisisobutyrazoline hydrochloride, azobisisobutyramidine hydrochloride, azobisisobutyramic acid, and azobisisopropylimidazoline.
[0013] As a third limitation, chelating agents include ethylenediaminetetraacetic acid or diethylenetriaminepentaacetic acid.
[0014] As a fourth limitation, initiator B includes azobisisobutyronitrile or dimethyl azobisisobutyrate.
[0015] This invention also provides a method for preparing the above-mentioned hydrophobic drag-reducing agent, comprising the following steps:
[0016] S1. Mix acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, modified nano silica, initiator A and chelating agent, and adjust the pH value to 8-9 to obtain solution A;
[0017] S2. Mix white oil, sorbitan oleate, polyoxyethylene dehydrated sorbitan oleate and initiator B to obtain solution B;
[0018] S3. Mix solutions A and B thoroughly and allow them to polymerize under an inert atmosphere to obtain a hydrophobic drag reducer.
[0019] As a limitation, the polymerization reaction is carried out at a temperature of 40–60°C for a time of 4–6 hours.
[0020] As another limitation, the inert atmosphere includes nitrogen.
[0021] By adopting the above technical solution, the technical progress achieved by this invention compared with the prior art is as follows:
[0022] ①The present invention provides a hydrophobic drag-reducing agent that can reverse the wettability of rock surface to hydrophobicity. Under the action of capillary force, water is difficult to enter the rock fracture reservoir, reducing the degree of hydration expansion of shale reservoir, and at the same time increasing the flowback rate of fracturing fluid.
[0023] ② The present invention provides a method for preparing a hydrophobic drag-reducing agent, which involves preparing an aqueous phase mixture solution and an oil phase mixture solution separately, and then mixing the two solutions for an oil-water interface polymerization reaction. The steps are simple and suitable for industrial production. Detailed Implementation
[0024] The present invention will be further described in detail below through specific embodiments. It should be understood that the described embodiments are only for explaining the present invention and do not limit the present invention.
[0025] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art.
[0026] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.
[0027] Example 1
[0028] This embodiment prepares a hydrophobic drag-reducing agent, specifically including the following steps:
[0029] S0. Preparation of modified nano-silica
[0030] 2 kg of nano-silica was dissolved in 80 kg of ethanol solution and stirred for 4 h until the solution was uniformly dispersed. 1 kg of 3-methacryloxypropyltrimethoxysilane was added and ultrasonically hydrolyzed for 10 min. 70 kg of anhydrous ethanol was added and the pH was adjusted to 3.0 with citric acid while stirring. 2 kg of perfluorooctyltriethoxysilane was added and ultrasonicated. The mixture was placed in an oil bath at 70 °C and stirred for 4 h. After drying, a white powdery solid was obtained, namely modified nano-silica α1.
[0031] Take a 250mL Erlenmeyer flask with a stopper, add a 1cm thick layer of modified nano-silica α1 inside the flask, then add 100mL of distilled water, stopper the flask and shake it. The nano-silica with hydrophobic surface treatment floats on the water surface, which proves that the nano-silica has been successfully modified (ordinary nano-silica will mix with water to form a transparent or translucent liquid).
[0032] S1. Mix 15 kg of acrylamide, 10 kg of acrylic acid, 2 kg of 2-acrylamido-2-methylpropanesulfonic acid, 1 kg of modified nano-silica α1, 0.1 kg of azobisisobutyrazoline hydrochloride and 0.5 kg of ethylenediaminetetraacetic acid, and adjust the pH to 8.5 with sodium hydroxide to obtain solution A.
[0033] S2. Mix 30 kg of white oil, 4 kg of sorbitan oleate, 1 kg of polyoxyethylene dehydrated sorbitan oleate and 1 kg of azobisisobutyronitrile to obtain solution B;
[0034] S3. Mix solutions A and B thoroughly, and under nitrogen protection, heat to 40°C for 4 hours to polymerize, thus obtaining the hydrophobic drag reducer β1.
[0035] Example 2
[0036] This embodiment prepares a hydrophobic drag-reducing agent, specifically including the following steps:
[0037] S0. Preparation of modified nano-silica
[0038] 4 kg of nano-silica was dissolved in 90 kg of ethanol solution and stirred for 6 h until the solution was uniformly dispersed. 2 kg of vinyltriethoxysilane was added and ultrasonically hydrolyzed for 10 min. 80 kg of anhydrous ethanol was added and the pH was adjusted to 4.0 with citric acid while stirring. 4 kg of perfluorooctyltriethoxysilane was added and ultrasonicated. The mixture was placed in an oil bath at 80 °C and stirred for 6 h. After drying, a white powdery solid was obtained, which is modified nano-silica α2.
[0039] Take a 250mL stoppered Erlenmeyer flask, add a 1cm thick layer of modified nano-silica α2 inside the flask, then add 100mL of distilled water, stopper the flask and shake it. The nano-silica with hydrophobic surface treatment floats on the water surface, proving that the nano-silica modification was successful.
[0040] S1. Mix 20 kg of acrylamide, 15 kg of acrylic acid, 3 kg of 2-acrylamido-2-methylpropanesulfonic acid, 2 kg of modified nano-silica α2, 0.5 kg of azobisisopropylimidazoline and 1 kg of diethylenetriaminepentaacetic acid, and adjust the pH to 9.0 with sodium hydroxide to obtain solution A.
[0041] S2. Mix 40 kg of white oil, 6 kg of sorbitan oleate, 2 kg of polyoxyethylene dehydrated sorbitan oleate and 2 kg of dimethyl azobisisobutyrate to obtain solution B;
[0042] S3. Mix solutions A and B thoroughly, and under nitrogen protection, heat to 60°C for 6 hours to polymerize, thus obtaining the hydrophobic drag reducer β2.
[0043] Example 3
[0044] This embodiment prepares a hydrophobic drag-reducing agent, specifically including the following steps:
[0045] S0. Preparation of modified nano-silica
[0046] 3 kg of nano-silica was dissolved in 85 kg of ethanol solution and stirred for 5 h until the solution was uniformly dispersed. 2 kg of 3-methacryloyloxypropyltrimethoxysilane was added and ultrasonically hydrolyzed for 10 min. 75 kg of anhydrous ethanol was added and the pH was adjusted to 4.0 with citric acid while stirring. 3 kg of perfluorooctyltriethoxysilane was added and ultrasonicated. The mixture was placed in an oil bath at 80 °C and stirred for 5 h. After drying, a white powdery solid was obtained, which is modified nano-silica α3.
[0047] Take a 250mL stoppered Erlenmeyer flask, add a 1cm thick layer of modified nano-silica α3 inside the flask, then add 100mL of distilled water, stopper the flask and shake it. The nano-silica with hydrophobic surface treatment floats on the water surface, proving that the nano-silica modification was successful.
[0048] S1. Mix 18 kg of acrylamide, 12 kg of acrylic acid, 3 kg of 2-acrylamido-2-methylpropanesulfonic acid, 1 kg of modified nano-silica α3, 0.2 kg of azobisisobutylamidine hydrochloride and 0.8 kg of ethylenediaminetetraacetic acid, and adjust the pH to 8.0 with sodium hydroxide to obtain solution A;
[0049] S2. Mix 40 kg of white oil, 5 kg of sorbitan oleate, 2 kg of polyoxyethylene dehydrated sorbitan oleate and 1 kg of azobisisobutyronitrile to obtain solution B;
[0050] S3. Mix solutions A and B thoroughly, and under nitrogen protection, heat to 50°C for 5 hours to polymerize, thus obtaining the hydrophobic drag reducer β3.
[0051] Example 4
[0052] This embodiment prepares a hydrophobic drag-reducing agent, specifically including the following steps:
[0053] S0. Preparation of modified nano-silica
[0054] 4 kg of nano-silica was dissolved in 90 kg of ethanol solution and stirred for 6 h until the solution was uniformly dispersed. 1.5 kg of vinyltriethoxysilane was added and ultrasonically hydrolyzed for 10 min. 80 kg of anhydrous ethanol was added and the pH was adjusted to 3.5 with citric acid while stirring. 2 kg of perfluorooctyltriethoxysilane was added and ultrasonicated. The mixture was placed in an oil bath at 80 °C and stirred for 5 h. After drying, a white powdery solid was obtained, namely modified nano-silica α4.
[0055] Take a 250mL stoppered Erlenmeyer flask, add a 1cm thick layer of modified nano-silica α4 inside the flask, then add 100mL of distilled water, stopper the flask and shake it. The nano-silica with hydrophobic surface treatment floats on the water surface, proving that the nano-silica modification was successful.
[0056] S1. Mix 16 kg of acrylamide, 12 kg of acrylic acid, 2.5 kg of 2-acrylamido-2-methylpropanesulfonic acid, 1.5 kg of modified nano-silica α4, 0.3 kg of azodicyanovalerate and 0.8 kg of diethylenetriaminepentaacetic acid, and adjust the pH to 8.0 with sodium hydroxide to obtain solution A.
[0057] S2. Mix 35 kg of white oil, 4 kg of sorbitan oleate, 1.5 kg of polyoxyethylene sorbitan oleate and 1.5 kg of dimethyl azobisisobutyrate to obtain solution B;
[0058] S3. Mix solutions A and B thoroughly, and under nitrogen protection, heat to 60°C for 6 hours to polymerize, thus obtaining the hydrophobic drag reducer β4.
[0059] Example 5
[0060] This embodiment prepares a hydrophobic drag-reducing agent, specifically including the following steps:
[0061] S0. Preparation of modified nano-silica
[0062] 4 kg of nano-silica was dissolved in 80 kg of ethanol solution and stirred for 6 h until the solution was uniformly dispersed. 2 kg of vinyltriethoxysilane was added and ultrasonically hydrolyzed for 10 min. 80 kg of anhydrous ethanol was added, and the pH was adjusted to 4.0 with citric acid while stirring. 4 kg of perfluorooctyltriethoxysilane was added and ultrasonicated. The mixture was placed in an oil bath at 80 °C and stirred for 6 h. After drying, a white powdery solid was obtained, namely modified nano-silica α5.
[0063] Take a 250mL stoppered Erlenmeyer flask, add a 1cm thick layer of modified nano-silica α5 inside the flask, then add 100mL of distilled water, stopper the flask and shake it. The nano-silica with hydrophobic surface treatment floats on the water surface, proving that the nano-silica modification was successful.
[0064] S1. Mix 20 kg of acrylamide, 15 kg of acrylic acid, 3 kg of 2-acrylamido-2-methylpropanesulfonic acid, 1 kg of modified nano silica α5, 0.5 kg of azobisisobutylamidine hydrochloride and 1 kg of diethylenetriaminepentaacetic acid, and adjust the pH to 9.0 with sodium hydroxide to obtain solution A.
[0065] S2. Mix 40 kg of white oil, 6 kg of sorbitan oleate, 2 kg of polyoxyethylene dehydrated sorbitan oleate and 1 kg of azobisisobutyronitrile to obtain solution B;
[0066] S3. Mix solutions A and B thoroughly, and under nitrogen protection, heat to 50°C for 5 hours to polymerize, thus obtaining the hydrophobic drag reducer β5.
[0067] Example 6
[0068] This embodiment prepares a hydrophobic drag-reducing agent, specifically including the following steps:
[0069] S0. Preparation of modified nano-silica
[0070] 4 kg of nano-silica was dissolved in 90 kg of ethanol solution and stirred for 4 h until the solution was uniformly dispersed. 2 kg of vinyltriethoxysilane was added and ultrasonically hydrolyzed for 10 min. 70 kg of anhydrous ethanol was added and the pH was adjusted to 3.0 with citric acid while stirring. 3 kg of perfluorooctyltriethoxysilane was added and ultrasonicated. The mixture was placed in an oil bath at 75 °C and stirred for 5 h. After drying, a white powdery solid was obtained, namely modified nano-silica α6.
[0071] Take a 250mL stoppered Erlenmeyer flask, add a 1cm thick layer of modified nano-silica α6 inside the flask, then add 100mL of distilled water, stopper the flask and shake it. The nano-silica with hydrophobic surface treatment floats on the water surface, proving that the nano-silica modification was successful.
[0072] S1. Mix 20 kg of acrylamide, 10 kg of acrylic acid, 2 kg of 2-acrylamido-2-methylpropanesulfonic acid, 2 kg of modified nano-silica α6, 0.3 kg of azodicyanovalerate, 0.1 kg of azodiisopropylimidazoline, and 0.8 kg of diethylenetriaminepentaacetic acid, and adjust the pH to 8.0 with sodium hydroxide to obtain solution A;
[0073] S2. Mix 35 kg of white oil, 5 kg of sorbitan oleate, 2 kg of polyoxyethylene sorbitan oleate and 1 kg of dimethyl azobisisobutyrate to obtain solution B;
[0074] S3. Mix solutions A and B thoroughly, and under nitrogen protection, heat to 60°C for 6 hours to polymerize, thus obtaining the hydrophobic drag reducer β6.
[0075] Example 7
[0076] This embodiment provides performance testing of hydrophobic drag-reducing agents β1 to β6, and provides comparative examples to verify the effect, specifically including the following steps:
[0077] I. Sample Preparation
[0078] Samples 1-6 are hydrophobic drag-reducing agents β1-β6 prepared in Examples 1-6;
[0079] Comparative Sample 1: The preparation method of Comparative Sample 1 is basically the same as the steps S1 to S3 in Example 1 for preparing hydrophobic drag reducer β1. The only difference is that Comparative Sample 1 does not add modified nano silica, but adds tetradecyl dimethyl allyl ammonium chloride as a substitute. The other components, dosages and control parameters are exactly the same.
[0080] Comparative Sample 2: The preparation method of Comparative Sample 2 is basically the same as the steps S1 to S3 in Example 2 for preparing hydrophobic drag reducer β2. The only difference is that Comparative Sample 2 does not add modified nano silica, but adds tetradecyl dimethyl allyl ammonium chloride as a substitute. The other components, dosages and control parameters are exactly the same.
[0081] Comparative Sample 3: The preparation method of Comparative Sample 3 is basically the same as the steps S1 to S3 in Example 3 for preparing hydrophobic drag reducer β3. The only difference is that Comparative Sample 3 does not add modified nano silica, but adds tetradecyl dimethyl allyl ammonium chloride as a substitute. The other components, dosages and control parameters are exactly the same.
[0082] II. Evaluation of drag reduction performance
[0083] According to the test method in section 7.12 of the "Evaluation Method for Performance of Water-Based Fracturing Fluids" (SY / T 5107-2016), the drag reduction performance of samples 1-6 and control samples 1-3 was tested using a closed-loop friction tester. Using clean water as a control, 0.1% and 0.15% of the weight of clean water were added to samples 1-6 and control samples 1-3, respectively. The drag reduction performance was measured at a shear rate of 4000 s⁻¹. -1 The drag reduction rate under the given conditions is calculated using the following formula:
[0084]
[0085] In the formula: η is the drag reduction rate, %; △P0 is the friction value of clean water, MPa; △P is the friction value of the drag-reducing agent, MPa;
[0086] Equipment parameters: test pipe diameter 10mm, test length 5m, flow velocity 9m / s, test temperature 25℃. Results are shown in Table 1.
[0087] Table 1. Results of resistance reduction test
[0088]
[0089] As shown in Table 1, samples 1-6 all exhibited good drag reduction rates. With a dosage of 0.1 wt%, the drag reduction rates ranged from 74.8% to 75.3%, compared to samples 1-3 without modified nano-silica, whose drag reduction rates ranged from 72.8% to 73.5%. With a dosage of 0.15 wt%, the drag reduction rates of samples 1-6 ranged from 75.3% to 77.5%, compared to samples 1-3, whose drag reduction rates ranged from 74.1% to 74.3%. This indicates that samples 1-6, like conventional drag reducers, exhibited high drag reduction rates and their drag reduction performance was not reduced by the introduction of hydrophobic modified nano-silica; in fact, their effects were slightly better than those of conventional drag reducers.
[0090] III. Viscosity Performance Evaluation
[0091] 0.2g of samples 1-6 and control samples 1-3 were respectively added to 100g of water and mixed. The apparent viscosity of the drag-reducing agent was tested using an ST-1536A fully automatic apparent viscosity meter. The results are shown in Table 2.
[0092] Table 2. Apparent viscosity test results
[0093] Sample number Apparent viscosity / mPa·s Sample 1 33.2 Sample 2 33.5 Sample 3 32.6 Sample 4 32.9 Sample 5 33.1 Sample 6 32.8 Comparison Sample 1 31.5 Comparison Sample 2 31.9 Comparison Sample 3 31.7
[0094] As shown in Table 2, at a dosage of 0.2 wt%, the apparent viscosity of samples 1–6 can reach 32.6–33.5 mPa·s, compared to the apparent viscosity range of 31.5–31.9 mPa·s for samples 1–3. The higher the apparent viscosity, the stronger the sand-carrying capacity. It can be seen that samples 1–6, like conventional drag reducers, have the effect of increasing the apparent viscosity of the liquid, and will not reduce the apparent viscosity of the fracturing fluid due to the introduction of hydrophobic modified nano-silica. Moreover, the effect is slightly better than that of conventional drag reducers.
[0095] IV. Evaluation of Surface Wetting Performance
[0096] Take 0.5g of samples 1-6 and control samples 1-3 respectively, add 100g of water and mix well. Soak the core samples in the mixture for 60min, then remove them and dry them at 40℃ for 1h. Afterwards, use a contact angle meter to measure the aqueous wetting angle of the core surface at a dosage of 0.5wt%. The results are shown in Table 3.
[0097] Table 3 Results of wetting angle test
[0098] Sample number Wetting angle / ° Untreated core 21.8 Sample 1 97.5 Sample 2 99.3 Sample 3 98.2 Sample 4 98.7 Sample 5 99.1 Sample 6 98.9 Comparison Sample 1 28.3 Comparison Sample 2 29.4 Comparison Sample 3 27.5
[0099] As shown in Table 3, the wetting angles of the core surfaces treated with samples 1 to 6 were between 97.5° and 99.3°, indicating hydrophobicity (hydrophobicity refers to a water phase contact angle on the rock surface greater than 90°). In contrast, the wetting angles of the core surfaces of samples 1 to 3 were between 27.5° and 29.4°, indicating hydrophilicity (hydrophilicity refers to a water phase contact angle on the rock surface less than 90°). This means that the hydrophobic drag reducers β1 to β6 can effectively change the wettability of the core surface, causing the wetting angle of the core surface to change from hydrophilic to hydrophobic.
Claims
1. A hydrophobic drag-reducing agent, characterized in that, The raw materials for its active ingredient, by weight, include: 15-20 parts acrylamide, 10-15 parts acrylic acid, 2-3 parts 2-acrylamido-2-methylpropanesulfonic acid, 1-2 parts modified nano silica, 0.1-0.5 parts initiator A, 0.5-1 part chelating agent, 30-40 parts white oil, 4-6 parts sorbitan oleate, 1-2 parts polyoxyethylene sorbitan oleate, and 1-2 parts initiator B.
2. The hydrophobic drag-reducing agent according to claim 1, characterized in that, The modified nano silica is prepared by the following method: 2-4 parts by weight of nano silica are dispersed in ethanol, 1-2 parts by weight of modifier are added, ultrasonic hydrolysis is performed, the pH value is adjusted to 3-4, 2-4 parts by weight of perfluorooctyltriethoxysilane is added to react, and the modified nano silica is obtained after drying. The modifier is 3-methacryloyloxypropyltrimethoxysilane or vinyltriethoxysilane.
3. The hydrophobic drag-reducing agent according to claim 2, characterized in that, The ultrasonic hydrolysis is carried out for 10 minutes; the reaction is carried out at a temperature of 70-80°C for 4-6 hours.
4. A hydrophobic drag-reducing agent according to any one of claims 1 to 3, characterized in that, The initiator A includes at least one of azobisisobutyrazoline hydrochloride, azobisisobutyramidine hydrochloride, azobisisobutyramic acid, and azobisisopropylimidazoline.
5. A hydrophobic drag-reducing agent according to any one of claims 1 to 3, characterized in that, Chelating agents include ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DITA).
6. A hydrophobic drag-reducing agent according to any one of claims 1 to 3, characterized in that, Initiator B includes azobisisobutyronitrile or dimethyl azobisisobutyrate.
7. A method for preparing a hydrophobic drag-reducing agent according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Mix acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, modified nano silica, initiator A and chelating agent, and adjust the pH value to 8-9 to obtain solution A; S2. Mix white oil, sorbitan oleate, polyoxyethylene dehydrated sorbitan oleate and initiator B to obtain solution B; S3. Mix solutions A and B thoroughly and allow them to polymerize under an inert atmosphere to obtain a hydrophobic drag reducer.
8. The preparation method according to claim 7, characterized in that, The polymerization reaction is carried out at a temperature of 40~60℃ for 4~6 hours.
9. The preparation method according to claim 7 or 8, characterized in that, The inert atmosphere includes nitrogen.