An amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer and its preparation method and application

Abstract

The present invention belongs to the technical field of heavy oil emulsification viscosity reduction, and specifically discloses an amphiphilic Janus carbon nanotube heavy oil emulsification viscosity reducer and its preparation method and application, including the following steps: First, multi-walled carbon nanotubes are added to a strong acid solution; secondly, after adding to the first solvent, molten paraffin is added to obtain paraffin microspheres wrapped with activated carbon nanotubes; thirdly, adding to the second solvent to obtain carbon nanotube paraffin microspheres asymmetrically modified with vinyltrimethylsilane; finally, adding to the third solvent to react with the first modifier, and then adding to the fourth solvent to react with the second modifier to obtain viscosity-reducing Janus carbon nanotubes. By adopting the above-mentioned amphiphilic Janus carbon nanotube heavy oil emulsification viscosity reducer and its preparation method and application, the viscosity reduction rate reaches 99.47%, has excellent wetting reversal and interfacial tension reduction ability, and the oil recovery rate is increased by more than 25%, and the effect of increasing the oil recovery rate is remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy oil emulsification and viscosity reduction, and in particular to an amphiphilic Janus carbon nanotube heavy oil emulsification viscosity reducer and its preparation method and application. Background Art

[0002] Crude oil with high viscosity and specific gravity is called heavy oil. It is statistically shown that heavy oil reservoirs account for 35% of the world's total oil reservoir content. Due to the increasing world energy demand, a large number of conventional oil reservoirs have entered the depletion stage. Although heavy oil reservoirs still have great exploitation potential due to their difficult exploitation and high exploitation cost, how to exploit heavy oil at low cost and efficiently is a problem that needs to be solved.

[0003] Due to the high viscosity of heavy oil itself, and the natural surfactant components such as resins and asphaltenes contained in it will cause self-emulsification between heavy oil and water, forming an emulsion, which further increases the viscosity of heavy oil, resulting in extremely low fluidity of heavy oil, and even no fluidity.

[0004] Enhanced oil recovery techniques for heavy oil reservoirs usually include heavy oil thermal recovery, heavy oil chemical flooding, in-situ catalytic upgrading of heavy oil, and gas injection for production. Heavy oil chemical flooding has advantages compared with other production methods. Compared with thermal recovery, it has low energy consumption, less damage to the formation, and a wide application range; compared with in-situ catalytic upgrading, it has low cost, simple process, and low risk; compared with gas injection for production, it has high oil displacement efficiency, strong adaptability, and little environmental impact.

[0005] In the prior art, the invention patent with the publication number CN115806812A discloses a preparation method and application of a heavy oil emulsification viscosity reducer. By adjusting the hydrophilic-lipophilic balance, a surfactant is prepared, which can form an oil-in-water emulsion with heavy oil to reduce the viscosity of heavy oil. The heavy oil emulsification viscosity reducer contains an anionic sulfonate surfactant, a non-ionic surfactant and water. The anionic sulfonate surfactant is an anionic sulfonate surfactant with a multi-branched structure of the hydrophobic tail chain based on polyolefins, and the emulsification viscosity reduction rate exceeds 90%. Therefore, reducing the viscosity of heavy oil is of great significance for improving oil recovery, but its oil recovery still needs to be improved, and how to further exploit heavy oil at low cost and efficiently still needs to be solved. Summary of the Invention

[0006] The purpose of the present invention is to provide an amphiphilic Janus carbon nanotube heavy oil emulsification viscosity reducer and its preparation method and application, with a viscosity reduction rate of 99.47%, excellent wetting reversal and interfacial tension reduction capabilities, and the oil recovery is increased by more than 25%, and the effect of improving oil recovery is remarkable.

[0007] To achieve the above purpose, the present invention provides a preparation method of an amphiphilic Janus carbon nanotube heavy oil emulsification viscosity reducer, which includes the following steps:

[0008] S1. Add multi-walled carbon nanotubes to a strong acid solution in proportion, heat and stir, and then filter, wash and dry to obtain activated carbon nanotubes with surface-modified hydroxyl groups.

[0009] S2. Add the activated carbon nanotubes obtained in S1 to a first solvent, then add molten paraffin, heat and stir, and then filter, wash and dry to obtain paraffin microspheres wrapped with activated carbon nanotubes.

[0010] S3. Add the paraffin microspheres obtained in S2 to a second solvent, heat and stir under the action of a first catalyst, and then filter and wash to obtain carbon nanotube paraffin microspheres asymmetrically modified with vinyltrimethylsilane.

[0011] S4. Add the carbon nanotube paraffin microspheres obtained in S3 to a third solvent, heat and stir under reflux with a first modifier under the action of a second catalyst and N 2 React, dissolve, wash and filter, then add to a fourth solvent, react with a second modifier under the action of a third catalyst, heat and stir, wash and filter to obtain viscosity-reducing Janus carbon nanotubes.

[0012] Preferably, in S1, the mass ratio of the multi-walled carbon nanotubes to the strong acid solution is 1 g: 60 - 80 ml; the strong acid solution is a mixed solution of 98% sulfuric acid and 65% nitric acid, and the volume ratio of the sulfuric acid to the nitric acid is 3:1.

[0013] Preferably, S1 is specifically:

[0014] Add multi-walled carbon nanotubes to a strong acid solution, stir at 85 - 100 °C at 12000 - 13000 rpm / min for 4 - 5 h, then wash with ethanol until the solution pH is neutral, filter and dry to obtain activated carbon nanotubes with surface-modified hydroxyl groups.

[0015] Preferably, in S2, the mass ratio of the activated carbon nanotubes, the first solvent and the paraffin is 1 - 2 g: 100 ml: 6 - 10 g;

[0016] The first solvent is a mixed solution of 0.02% cetyltrimethylammonium bromide, 6.7% ethanol and water.

[0017] Preferably, S2 is specifically:

[0018] Add the activated carbon nanotubes obtained in S1 to a first solvent, then add molten paraffin, stir at 75 - 80 °C at 12000 - 13000 rpm / min for 30 - 35 min, then wash with ethanol, filter and dry to obtain paraffin microspheres wrapped with activated carbon nanotubes.

[0019] Preferably, in S3, the mass ratio of the paraffin microspheres, the second solvent, and the first catalyst is 1-2 g: 100 ml: 0.6-1.0 ml;

[0020] The second solvent is a mixed solution of vinyltrimethoxysilane, ethanol, and water, and the mass ratio of vinyltrimethoxysilane, ethanol, and water is 6-8: 96: 4;

[0021] The first catalyst is glacial acetic acid.

[0022] Preferably, in S4, the addition amount of the carbon nanotube paraffin microspheres is 1.8%-2% of the addition amount of the third solvent;

[0023] The third solvent is deionized water;

[0024] The second catalyst is one or both of ammonium persulfate or NaOH, and the addition amount of the second catalyst is 0.01%-0.03% of the third solvent;

[0025] The first modifier is a mixture of maleic acid and sodium vinylsulfonate, the mass ratio of maleic acid to sodium vinylsulfonate is 1-1.5, and the addition amount of the first modifier is 1.8%-2% of the addition amount of the third solvent;

[0026] The fourth solvent is one of toluene, petroleum ether, or n-octane;

[0027] The third catalyst is NaOH, and the addition amount of the third catalyst is 0.01%-0.02% of the fourth solvent;

[0028] The second modifier is 1-bromooctadecane, and the addition amount of the second modifier is 2%-3% of the fourth solvent.

[0029] Preferably, S4 is specifically:

[0030] Add the carbon nanotube paraffin microspheres obtained in S3 into the third solvent, then add the second catalyst, and then introduce N for 25-30 min 2 , stir and reflux at 45-50 °C for 4-5 h to react with the first modifier, add one of n-heptane, petroleum ether, or acetone for dissolution treatment, then wash with absolute ethanol, filter and add into the fourth solvent, and react with the second modifier at 60-65 °C and 400-600 r / min under the action of the third catalyst for 8-10 h, wash and filter to obtain the viscosity-reducing Janus carbon nanotubes.

[0031] To achieve the above object, the present invention also provides an amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer, which is prepared by uniformly mixing sodium lauryl polyoxyethylene ether sulfate, cocoamidopropyl betaine, water and the viscosity-reducing Janus carbon nanotubes to obtain the amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer.

[0032] To achieve the above object, the present invention also provides an application of an amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer in heavy oil emulsifying viscosity reduction and enhanced oil recovery.

[0033] Therefore, the present invention adopts the above-mentioned amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer, its preparation method and application, and the beneficial effects are as follows:

[0034] (1) Compared with the prior art, the preparation method of the present invention uses multi-walled carbon nanotubes as the base material, increases the coating rate of paraffin microspheres by adding cetyltrimethylammonium bromide and optimizes the modification sequence and conditions. The carbon nanotubes introduce hydrophilic long chains through emulsion polymerization reaction and Williamson reaction. The carbon nanotubes have more prominent Janus asymmetry, amphiphilicity and interfacial activity, and form nanofluids through compounding to reduce the oil-water interfacial tension, that is, reduce the heavy oil reservoir and stabilize the emulsion, and improve the heavy oil recovery rate.

[0035] (2) Compared with the prior art where the viscosity reduction rate is mostly 90%, the viscosity reduction rate of the emulsifying viscosity reducer of the present invention reaches 99.47%, exceeding most emulsifying viscosity reducers. Configured into nanofluids, it can not only reduce the oil-water interfacial tension, but also improve the recovery rate by more than 25%, and the effect of improving the recovery rate is remarkable;

[0036] (3) Compared with conventional viscosity reducers, the present invention has the characteristics of low cost and high efficiency, can reduce the dosage of surfactants, and can be widely applied in the field.

[0037] The technical solutions of the present invention will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a synthesis schematic diagram of an embodiment of an amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer, its preparation method and application of the present invention;

[0039] Figure 2 is an FT-IR characteristic curve diagram of an embodiment of an amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer, its preparation method and application of the present invention;

[0040] Figure 3 is a flow chart of an enhanced oil recovery experiment of an embodiment of an amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer, its preparation method and application of the present invention;

[0041] Figure 4 It is a graph showing the experimental results of enhanced oil recovery in an example of an amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer, its preparation method and application of the present invention. Specific embodiments

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs.

[0044] Example 1

[0045] As Figure 1 shown, a viscosity-reducing (amphiphilic) Janus carbon nanotube has the following structural formula for its hydrophilic group:

[0046] .

[0047] Its preparation method is as follows:

[0048] (1) Prepare 80 ml of a strong acid solution by mixing concentrated sulfuric acid with a concentration of 98% and concentrated nitric acid with a concentration of 65% at a volume ratio of 3:1. Take 1 g of multi-walled carbon nanotubes and add them to the strong acid solution. Heat and stir for 4 h, wash until the carbon nanotube solution is neutral, and filter and dry to obtain activated carbon nanotubes with surface-modified hydroxyl groups.

[0049] (2) Take 1 g of activated carbon nanotubes and add them to 100 ml of an ethanol solution with a mass concentration of 6.7%. After ultrasonic dispersion for 30 min, add 0.02 g of cetyltrimethylammonium bromide and 6 g of molten paraffin. Stir at a rate of 12,000 rpm for 30 min at 75 °C to obtain a paraffin microsphere solution encapsulated by activated carbon nanotubes.

[0050] (3) Filter and wash to obtain paraffin microspheres encapsulated by activated carbon nanotubes.

[0051] (4) Place the paraffin microspheres in a beaker, add 96 mL of ethanol and 4 mL of deionized water in sequence, stir evenly, and then perform ultrasonic dispersion for 30 min to obtain a paraffin microsphere dispersion.

[0052] (5) Add a vinyltrimethoxysilane solution with a mass concentration of 6% to a round-bottom flask, then add glacial acetic acid to adjust the pH value to weakly acidic. After adding the paraffin microsphere dispersion and mixing evenly, heat and stir under reflux at 75 °C for 4 h.

[0053] (6) Filter and wash to obtain carbon nanotube paraffin microspheres asymmetrically modified with vinyltrimethylsilane.

[0054] (7) Prepare a 100 ml paraffin microsphere dispersion with a mass concentration of 2%. Add 2 g of maleic acid and sodium vinyl sulfonate in a mass ratio of 1:1, adjust the pH value to (weakly alkaline) 7 - 8, ultrasonically disperse for 30 min, then add it to a three-necked flask, and introduce N for 30 min 2 Then add 0.03 g of ammonium persulfate, and heat and stir under reflux at 50 °C for 4 h.

[0055] (8) After filtration, wash the paraffin microspheres repeatedly with n-heptane, and filter, wash, and dry to obtain activated carbon nanotubes modified with asymmetric hydrophilic long chains.

[0056] (9) Take 1 g of the activated carbon nanotubes obtained in step (8) above, add it to 50 ml of petroleum ether, ultrasonically disperse for 30 min, then add 1 g of 1-bromooctadecane, and add a small amount of NaOH and react at 60 °C and 400 rpm for 8 h.

[0057] (10) Filter, wash, and dry to obtain amphiphilic Janus carbon nanotubes.

[0058] Experimental tests

[0059] (1) FT-IR test

[0060] Use FT-IR to analyze the functional group composition of multi-walled carbon nanotubes and the amphiphilic Janus carbon nanotubes prepared in Example 1. The results are as Figure 2 shown.

[0061] It can be seen from Figure 2 that the peaks at 3418 cm -1 and 1704 cm -1 are respectively the stretching vibration characteristic peaks of hydroxyl and carbonyl groups; the peaks at 2920 cm -1 and 2850 cm -1 , 1400 cm -1 are respectively the asymmetric stretching vibration characteristic peak, symmetric stretching vibration characteristic peak, and in-plane bending vibration characteristic peak of C-H in methylene; 1120 cm -1 is the stretching vibration characteristic peak of S-O; 1032 cm -1 is the stretching vibration characteristic peak of Si-O; 749 cm -1 is the stretching vibration characteristic peak of C-S. The peak at 1032 cm -1 represents the successful grafting of vinyltrimethoxysilane on the surface of carbon nanotubes; the peaks at 3418 cm -1 and 1704 cm -1 represent the successful grafting of maleic acid. At the same time, it can be found that compared with before modification, the amphiphilic modified Janus carbon nanotubes have an additional stretching vibration peak of carbonyl group, further verifying the successful grafting of maleic acid; 1120 cm -1and 749 cm -1 The two peaks represent sulfonic acid groups, indicating that sodium vinyl sulfonate has been successfully introduced onto the surface of carbon nanotubes; by comparing before and after modification, it can be found that there are three additional peaks in the amphiphilic Janus carbon nanotubes at 2920 cm -1 and 2850 cm -1 、1400 cm -1 , which can prove that the alkyl long chain has been successfully introduced onto the surface of carbon nanotubes. In summary, the synthesis of amphiphilic Janus carbon nanotubes is successful.

[0062] (2)Enhanced oil recovery test

[0063] Select sodium lauryl polyoxyethylene ether sulfate with a mass concentration of 0.08%, cocoamidopropyl betaine with a mass concentration of 0.02%, and the amphiphilic Janus carbon nanotubes prepared in Example 1 with a mass concentration of 0.02%, and the balance is water, and formulate it into an amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer.

[0064] Measure the enhanced oil recovery ability of the amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer through a core flooding experiment. Select a core with a water permeability of 1500 mD for the core flooding experiment. The experimental process is as Figure 3 shown. The specific steps are as follows: First, evacuate the core and saturate it with simulated formation water. At 65 °C, saturate the water-saturated core with crude oil at a rate of 0.1 ml / min until no water comes out at the end of the core holder. Close the front and rear valves of the core holder and age it in an oven at 65 °C for 24 h. According to Figure 3 Connect the pipeline, and then inject simulated formation water at a rate of 0.5 ml / min until the water cut reaches 98% and stop injecting water. Then inject 0.3 PV of the amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer (nano-fluid) at a rate of 0.5 ml / min. Then inject water at a flow rate of 0.5 ml / min until the water cut at the outlet end of the core holder reaches 98% and stop injecting.

[0065] Measure the oil displacement effect of the amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer. During the whole process, record the injection end pressure, water cut, cumulative oil recovery every 0.05 PV injection volume and plot the water cut, oil recovery and injection end pressure curves. The water cut calculation formula is shown in Equation (1), and the oil recovery calculation formula is shown in Equation (2).

[0066] (1)

[0067] In the formula, is the water cut; is the water content in the produced fluid, ml; is the total volume of the produced fluid, ml.

[0068] (2)

[0069] wherein E is the recovery factor; is the cumulative volume of produced oil, ml; is the volume of oil in the rock pores, ml.

[0070] The experimental results of enhanced oil recovery are as Figure 4 shown. When the primary water flooding starts, due to the two-phase flow of oil and water, the water saturation in the core is relatively low at this time, the relative permeability of the water phase is relatively low, and the displacement resistance is relatively large, manifested as a sharp increase in pressure. However, as the formation of the water flooding dominant channel, the pressure gradually decreases and tends to be stable. In this stage, the water cut and the recovery factor increase sharply until reaching the high water cut stage, and the recovery factor basically no longer changes. After the primary water flooding ends, with the injection of the amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer, the recovery degree has a small increase. This may be because the contact between the amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer and the rock causes the rock to undergo wettability reversal, stripping the oil film on the rock surface. At the same time, under the action of shear force, an oil-in-water emulsion is formed with the residual oil and carried out. When the secondary water flooding starts, the oil production degree gradually increases and tends to be stable. At this time, the water cut curve presents a "funnel" shape, and the pressure shows obvious fluctuations. This may be because the injection of the amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer leads to the subsequent water flooding expanding the swept volume, and due to the excellent interfacial tension reduction performance and emulsifying viscosity reduction performance of the amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer, an emulsion is formed with the residual oil. When the emulsion passes through the small pores, the water flooding pressure increases due to the Jamin effect. However, with the continuous action of shear force, the emulsion particle size gradually decreases and passes through the small pores, resulting in a continuous decrease in the injection pressure and a continuous increase in the recovery factor. The enhanced oil recovery amplitude reaches 26.16%, and the amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer has excellent enhanced oil recovery ability.

[0071] Therefore, the present invention adopts the above-mentioned amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducer and its preparation method and application. The viscosity reduction rate reaches 99.47%, has excellent wettability reversal and interfacial tension reduction ability, and the enhanced oil recovery exceeds 25%, with a remarkable enhanced oil recovery effect.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an amphiphilic Janus carbon nanotube heavy oil emulsifying and viscosity reducing agent, characterized in that: The following steps are involved: S1, adding multi-walled carbon nanotubes to a strong acid solution according to a certain proportion, heating and stirring, and then filtering, washing and drying to obtain activated carbon nanotubes with surface modified with hydroxyl groups; S2, adding the activated carbon nanotubes obtained in S1 to the first solvent and then adding molten paraffin, heating and stirring, and then filtering, washing and drying to obtain paraffin microspheres wrapped by the activated carbon nanotubes; S3, adding the paraffin microspheres obtained in S2 to the second solvent, heating and stirring under the action of the first catalyst, and then filtering and washing to obtain carbon nanotube paraffin microspheres asymmetrically modified with vinyltrimethylsilane; S4, adding the carbon nanotube paraffin microspheres obtained in S3 to the third solvent, heating, stirring, refluxing and reacting with the first modifier under the action of the second catalyst and N2, dissolving, washing, filtering and then adding to the fourth solvent, reacting with the second modifier under the action of the third catalyst, heating, stirring, washing, filtering, and obtaining reduced viscosity Janus carbon nanotubes; Evenly mixing fatty alcohol polyoxyethylene ether sodium sulfate, cocamidopropyl betaine, water and the viscosity reducing Janus carbon nanotubes to obtain an amphiphilic Janus carbon nanotube heavy oil emulsifying viscosity reducing agent; In S2, the activated carbon nanotubes, the first solvent and the paraffin are used in a ratio of 1-2 g:100 ml:6-10 g; The first solvent is a mixed solution of 0.02% hexadecyltrimethylammonium bromide, 6.7% ethanol and water; In S3, the amount ratio of the paraffin microspheres, the second solvent and the first catalyst is 1-2 g: 100 ml: 0.6-1.0 ml; The second solvent is a mixed solution of vinyltrimethoxysilane, ethanol and water, and the mass ratio of the vinyltrimethoxysilane, the ethanol and the water is 6-8:96:4; The first catalyst is glacial acetic acid; In S4, the amount of the carbon nanotube paraffin microspheres added is 1.8% to 2% of the amount of the third solvent added; The third solvent is deionized water; The second catalyst is ammonium persulfate, and the amount of the second catalyst added is 0.01% to 0.03% of the third solvent; The first modifier is a mixture of maleic acid and sodium vinyl sulfonate, the mass ratio of maleic acid to sodium vinyl sulfonate is 1-1.5, and the amount of the first modifier added is 1.8%-2% of the amount of the third solvent added; The fourth solvent is one of toluene, petroleum ether or n-octane; The third catalyst is NaOH, and the addition amount of the third catalyst is 0.01% to 0.02% of the fourth solvent; The second modifier is 1-bromooctadecane, and the added amount of the second modifier is 2% to 3% of the fourth solvent.

2. The method for preparing an amphiphilic Janus carbon nanotube heavy oil emulsifying and viscosity reducing agent according to claim 1, characterized in that: In S1, the ratio of the multi-walled carbon nanotubes to the strong acid solution is 1g:60-80ml; the strong acid solution is a mixed solution of 98% sulfuric acid and 65% nitric acid, and the volume ratio of sulfuric acid to nitric acid is 3:

1.

3. The method for preparing an amphiphilic Janus carbon nanotube heavy oil emulsifying and viscosity reducing agent according to claim 1, characterized in that: S1 is specifically: The multi-walled carbon nanotubes are added to a strong acid solution, stirred at 85-100°C and 12000-13000 rpm / min for 3-4 hours, then washed with ethanol until the pH of the solution is neutral, filtered and dried to obtain activated carbon nanotubes with surface modified hydroxyl groups.

4. The method for preparing an amphiphilic Janus carbon nanotube heavy oil emulsifying and viscosity reducing agent according to claim 1, characterized in that: S2 is specifically: The activated carbon nanotubes obtained in S1 are added to the first solvent and then molten paraffin, stirred at 75-80°C and 12000-13000 rpm / min for 30-35 min, then washed with ethanol, filtered and dried to obtain paraffin microspheres wrapped with activated carbon nanotubes.

5. The method for preparing an amphiphilic Janus carbon nanotube heavy oil emulsifying and viscosity reducing agent according to claim 1, characterized in that: S4 is specifically: The carbon nanotube paraffin microspheres obtained in S3 are added to the third solvent, and then the second catalyst is added, and N2 is introduced for 25 to 30 minutes, and stirred and refluxed at 45 to 50°C to react with the first modifier for 4 to 5 hours, and one of n-heptane, petroleum ether or acetone is added for dissolution treatment, and then washed with anhydrous ethanol, filtered and added to the fourth solvent, and reacted with the second modifier for 8 to 10 hours at 60 to 65°C and 400 to 600 r / min under the action of the third catalyst, washed and filtered to obtain reduced viscosity Janus carbon nanotubes.

6. An amphiphilic Janus carbon nanotube heavy oil emulsifying and viscosity reducing agent prepared by the preparation method of the amphiphilic Janus carbon nanotube heavy oil emulsifying and viscosity reducing agent according to any one of claims 1 to 5.

7. Use of the amphiphilic Janus carbon nanotube heavy oil emulsification and viscosity reduction agent as claimed in claim 6 in heavy oil emulsification and viscosity reduction to enhance oil recovery.

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