Preparation method and application of ultra-low surface tension drainage agent

Abstract

The present invention relates to the field of petrochemical technology, specifically a preparation method and application of an ultra-low surface tension drainage aid, including 35-45 parts by weight of n-butanol, 80-200 parts by weight of triazine-based amphoteric polyoxyethylene ether surfactants, 100-150 parts by weight of nonionic surfactants, 20-30 parts by weight of kerosene, and 80-110 parts by weight of deionized water; the present invention is compounded with triazine-based amphoteric polyoxyethylene ether surfactants and nonionic surfactants, as the main agent of a microemulsion drainage aid, the two form a good homogeneous microemulsion system, the drainage aid emulsion has low surface tension, and good temperature resistance, when the mass fraction of the triazine-based amphoteric polyoxyethylene ether surfactant in the drainage aid is 0.8%, the drainage aid rate is as high as 88.12%. It has broad application prospects in acid fracturing fluid drainage.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical industry, and in particular to a preparation method and application of an ultra-low surface tension drainage agent. Background Art

[0002] In the process of oilfield exploitation, acid fracturing technology is an important method to increase the production of oil and gas wells. In the process of acid fracturing, the flowback fluid in the oil and gas wells needs to be discharged to the ground through the pressure of the formation itself. When the formation pressure gradually decreases, it will affect the flowback speed of the flowback fluid in the well, resulting in a large amount of acid fracturing fluid being unable to be discharged due to capillary resistance, which has a great impact on the fracturing operation process and the efficiency of oil and gas well exploitation. Therefore, it is of great significance to develop high-performance drainage aids.

[0003] Surfactants mainly include nonionic surfactants, cationic surfactants, zwitterionic surfactants, etc. They are widely used in petrochemical fields such as fracturing fluids, thickeners, and drainage agents. Traditional drainage agents are mainly fluorocarbon surfactants, but fluorocarbon surfactants have disadvantages such as large pollution and difficulty in degradation. Microemulsions are composed of water phase, oil phase, surfactants, etc. as main components, and can form a transparent and stable dispersion system with the characteristics of small particle size and low surface tension. In recent years, the development of microemulsion drainage agents has become a research trend. The present invention aims to compound a new zwitterionic surfactant with a traditional nonionic surfactant to obtain a microemulsion drainage agent with ultra-low surface tension, good temperature resistance and high drainage effect. Summary of the invention

[0004] The invention solves the problems of the existing drainage aids such as large surface tension, poor temperature resistance and poor drainage effect.

[0005] The technical scheme provided by the present invention is: a method for preparing an ultra-low surface tension drainage aid: 35-45 parts by weight of n-butanol, 80-200 parts by weight of triazine-based amphoteric polyoxyethylene ether surfactant, 100-150 parts by weight of non-ionic surfactant, 20-30 parts by weight of kerosene, and 80-110 parts by weight of deionized water are added into a test tube, the mixture is shaken and mixed, allowed to stand for stratification, a homogeneous emulsion is collected, and deionized water is added for dilution to obtain an ultra-low surface tension drainage aid.

[0006] Furthermore, the nonionic surfactants include AEO-9, OP-10, and isomeric tridecyl alcohol polyoxyethylene ether E1306.

[0007] Furthermore, the mass fraction of the amphoteric polyoxyethylene ether surfactant in the ultra-low surface tension drainage agent is 0.2-1.2%.

[0008] Further, triazine-based amphoteric polyoxyethylene ether surfactant:

[0009] Step (1), add 1 mol: (4.4-6) mol: (8-12) mol of p-phenylenedioxy (dichloro-s-triazine), N-methyl-2-hydroxyethylamine, N,N-diisopropylethylamine, and tetrahydrofuran into a flask equipped with a condenser reflux tube, place it in a water bath, stir the reaction and then distill under reduced pressure, wash the product with petroleum ether, and then recrystallize it with dichloromethane to obtain p-phenylenedioxy (N-methylhydroxyethylamino-s-triazine). The reaction formula is:

[0010]

[0011] Step (2), add phenylenedioxy (N-methylhydroxyethylamino-s-triazine) and potassium hydroxide into a reaction kettle, evacuate the air, heat to 100-110°C, introduce ethylene oxide, heat to 130-140°C, and adjust the pressure in the reaction kettle to 0.3-0.35MPa. After 3-4h of reaction, cool the material, add deionized water and phosphoric acid to neutralize, add activated carbon to remove impurities by adsorption, filter and dry the filtrate to obtain triazine polyoxyethylene ether. The reaction formula is:

[0012]

[0013] Step (3), adding triazine polyoxyethylene ether, sodium 3-chloro-2-hydroxypropanesulfonate, and N,N-dimethylformamide in a ratio of 1g:(0.45-0.72)g to a reaction kettle, heating to the reaction temperature, cooling the material after the reaction, distilling under reduced pressure, washing the product with a saturated sodium chloride solution, and drying to obtain a triazine-based amphoteric polyoxyethylene ether surfactant. The reaction formula is:

[0014]

[0015] Furthermore, in step (1), the temperature of the water bath is 70-80° C., and the reaction time is 12-18 h.

[0016] Furthermore, in step (2), the ratio of 1-phenylenedioxy(N-methylhydroxyethylamino-s-triazine), potassium hydroxide, and ethylene oxide is 1 mol:(0.05-0.08) mol:(21-36) mol.

[0017] Furthermore, in step (3), the reaction temperature is 100-120° C. and the reaction time is 48-72 h.

[0018] The technical effect of the present invention is as follows: the present invention uses a triazine-based amphoteric polyoxyethylene ether surfactant and a nonionic surfactant to compound as the main agent of a microemulsion drainage agent, wherein the triazine-based amphoteric polyoxyethylene ether surfactant contains multiple polyoxyethylene ether side chains and multiple betaine zwitterionic groups, so that it has a strong surface activity. As a zwitterionic surfactant, after compounding with nonionic surfactants such as AEO-9, a good homogeneous microemulsion system is formed, and the surface tension of the drainage agent emulsion is only 22.51-30.12 mN / m. In addition, the triazine-based amphoteric polyoxyethylene ether surfactant contains a phenyl triazine structure and a sulfonic acid betaine zwitterionic group, has higher heat resistance, can improve the temperature resistance of the surfactant, and after being subjected to a high-temperature heat treatment at 80°C, the drainage agent still has a lower surface tension. The drainage agent can meet the practical application of oil field fracturing technology and backflow under high temperature environment.

[0019] The triazine-based amphoteric polyoxyethylene ether surfactant and the nonionic surfactant of the present invention form a microemulsion system. The microemulsion has a smaller droplet size and can effectively enter the pores of the rock. After fully contacting the rock surface, the surface and interfacial tension are significantly reduced, the surface wettability of the rock is changed, and it is beneficial to reduce the capillary resistance and the pressure of the residual liquid after fracturing, thereby improving the drainage effect. When the mass fraction of the triazine-based amphoteric polyoxyethylene ether surfactant in the drainage aid is 0.8%, the drainage rate is as high as 88.12%. It has broad application prospects in the drainage of acid fracturing fluid. DETAILED DESCRIPTION

[0020] In order to better understand the technical solution of the present invention, the above content of the present invention is further described in detail below through specific implementation methods in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples. All technologies realized based on the above content of the present invention belong to the scope of the present invention.

[0021] The structural formula of terephthalene dioxy (dichloro-s-triazine) is: The preparation was carried out according to the method of the literature "4,6-Bis-and2,4,6-tris-(N,Ndiallylamino)-s-triazine: synthesized, NMR spectra and restrifactions" (DOI No. 10.1039 / P29950000785): 40 mL of methanol, 22 mmol of cyanuric chloride, 10 mmol of hydroquinone and 40 mL of 8% sodium hydroxide solution were added into a flask, and the reaction was carried out at room temperature for 3 h. The precipitate was collected by filtration, washed with methanol and dried to obtain phenylenedioxy (dichloro-s-triazine).

[0022] Example 1

[0023] 4 mmol of phenylenedioxy (dichloro-s-triazine), 17.6 mmol of N-methyl-2-hydroxyethylamine, 48 mmol of N,N-diisopropylethylamine, and 30 mL of tetrahydrofuran were added to a flask equipped with a condenser reflux tube, placed in a water bath, the water bath temperature was controlled to 80°C, stirred for 12 hours, and distilled under reduced pressure. The product was washed with petroleum ether and then recrystallized with dichloromethane to obtain phenylenedioxy (N-methylhydroxyethylamino-s-triazine).

[0024] Example 2

[0025] 4 mmol of phenylenedioxy (dichloro-s-triazine), 24 mmol of N-methyl-2-hydroxyethylamine, 32 mmol of N,N-diisopropylethylamine, and 40 mL of tetrahydrofuran were added to a flask equipped with a condenser reflux tube, placed in a water bath, the water bath temperature was controlled to 70°C, stirred for 18 hours, and distilled under reduced pressure. The product was washed with petroleum ether and then recrystallized with dichloromethane to obtain phenylenedioxy (N-methylhydroxyethylamino-s-triazine).

[0026] Example 3

[0027] 5 mmol of p-phenylenedioxy (N-methylhydroxyethylamino-s-triazine) (prepared according to the method of Example 1) and 0.4 mmol of potassium hydroxide were added to a reactor to evacuate the air, the temperature was raised to 100° C., 180 mmol of ethylene oxide was introduced, the temperature was raised to 130° C., and the pressure in the reactor was regulated to 0.35 MPa. After 4 hours of reaction, the material was cooled and neutralized by adding deionized water and phosphoric acid, and then activated carbon was added to remove impurities by adsorption. After filtering, the filtrate was dried to obtain triazine polyoxyethylene ether.

[0028] 10 g of triazine polyoxyethylene ether, 4.5 g of sodium 3-chloro-2-hydroxypropanesulfonate, and 80 mL of N,N-dimethylformamide were added to a reactor, the temperature was raised to 100°C, the reaction was continued for 72 hours, the material was cooled and discharged, and the product was distilled under reduced pressure. The product was washed with a saturated sodium chloride solution and dried to obtain a triazine-based amphoteric polyoxyethylene ether surfactant.

[0029] Add 35 g of n-butanol, 80 g of triazine-based amphoteric polyoxyethylene ether surfactant, 120 g of non-ionic surfactant AEO-9, 25 g of kerosene, and 110 g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of the amphoteric polyoxyethylene ether surfactant in the emulsion to 0.2%, and obtain an ultra-low surface tension drainage aid.

[0030] Example 4

[0031] 5 mmol of p-phenylenedioxy (N-methylhydroxyethylamino-s-triazine) (prepared according to the method of Example 1) and 0.25 mmol of potassium hydroxide were added to a reactor to evacuate the air, the temperature was raised to 100° C., 105 mmol of ethylene oxide was introduced, the temperature was raised to 135° C., and the pressure in the reactor was regulated to be 0.35 MPa. After 3 hours of reaction, the material was cooled and neutralized by adding deionized water and phosphoric acid, and then activated carbon was added to remove impurities by adsorption. After filtering, the filtrate was dried to obtain triazine polyoxyethylene ether.

[0032] 10 g of triazine polyoxyethylene ether, 7.2 g of sodium 3-chloro-2-hydroxypropanesulfonate, and 120 mL of N,N-dimethylformamide were added to a reactor, the temperature was raised to 110°C, the reaction was continued for 72 hours, the material was cooled and discharged, and the product was distilled under reduced pressure. The product was washed with a saturated sodium chloride solution and dried to obtain a triazine-based amphoteric polyoxyethylene ether surfactant.

[0033] Add 45g of n-butanol, 120g of triazine-based amphoteric polyoxyethylene ether surfactant, 100g of nonionic surfactant OP-10, 30g of kerosene, and 100g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of the amphoteric polyoxyethylene ether surfactant in the emulsion to 0.2%, and obtain an ultra-low surface tension drainage aid.

[0034] Example 5

[0035] 5 mmol of p-phenylenedioxy (N-methylhydroxyethylamino-s-triazine) (prepared according to the method of Example 1) and 0.36 mmol of potassium hydroxide were added to a reactor, and the air was evacuated and the temperature was raised to 110° C., 150 mmol of ethylene oxide was introduced, the temperature was raised to 130° C., and the pressure in the reactor was regulated to 0.3 MPa. After 4 hours of reaction, the material was cooled and neutralized by adding deionized water and phosphoric acid, and then activated carbon was added to remove impurities by adsorption. After filtering, the filtrate was dried to obtain triazine polyoxyethylene ether.

[0036] 10 g of triazine polyoxyethylene ether, 5.4 g of sodium 3-chloro-2-hydroxypropanesulfonate, and 100 mL of N,N-dimethylformamide were added to a reactor, the temperature was raised to 110°C, the reaction was continued for 48 hours, the material was cooled and discharged, and the product was distilled under reduced pressure. The product was washed with a saturated sodium chloride solution and dried to obtain a triazine-based amphoteric polyoxyethylene ether surfactant.

[0037] Add 45 g of n-butanol, 200 g of triazine-based amphoteric polyoxyethylene ether surfactant, 100 g of non-ionic surfactant AEO-9, 20 g of kerosene, and 80 g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of the amphoteric polyoxyethylene ether surfactant in the emulsion to 0.2%, and obtain an ultra-low surface tension drainage aid.

[0038] Example 6

[0039] 5 mmol of p-phenylenedioxy (N-methylhydroxyethylamino-s-triazine) (prepared according to the method of Example 1) and 0.31 mmol of potassium hydroxide were added to a reactor to evacuate the air, the temperature was raised to 100° C., 135 mmol of ethylene oxide was introduced, the temperature was raised to 140° C., and the pressure in the reactor was regulated to be 0.3 MPa. After 3 hours of reaction, the material was cooled and neutralized by adding deionized water and phosphoric acid, and then activated carbon was added to remove impurities by adsorption. After filtering, the filtrate was dried to obtain triazine polyoxyethylene ether.

[0040] 10 g of triazine polyoxyethylene ether, 6.6 g of sodium 3-chloro-2-hydroxypropanesulfonate, and 100 mL of N,N-dimethylformamide were added to a reactor, the temperature was raised to 120°C, the reaction was continued for 48 hours, the material was cooled and discharged, and the product was distilled under reduced pressure. The product was washed with a saturated sodium chloride solution and dried to obtain a triazine-based amphoteric polyoxyethylene ether surfactant.

[0041] Add 38g of n-butanol, 160g of triazine-based amphoteric polyoxyethylene ether surfactant, 150g of nonionic surfactant isotridecyl polyoxyethylene ether E1306, 30g of kerosene, and 110g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of the amphoteric polyoxyethylene ether surfactant in the emulsion to 0.2%, and obtain an ultra-low surface tension drainage aid.

[0042] Comparative Example 1

[0043] Add 35 g of n-butanol, 120 g of nonionic surfactant AEO-9, 25 g of kerosene, and 110 g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water for dilution (the dilution amount of deionized water is the same as that in Example 3), and obtain a drainage agent.

[0044] Comparative Example 2

[0045] Add 35 g of n-butanol, 80 g of a triazine-based amphoteric polyoxyethylene ether surfactant (prepared according to the method of Example 3), 25 g of kerosene, and 110 g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of triazine polyoxyethylene ether in the emulsion to 0.2%, and obtain a drainage agent.

[0046] Comparative Example 3

[0047] Add 35 g of n-butanol, 80 g of triazine polyoxyethylene ether (prepared according to the method of Example 3), 120 g of non-ionic surfactant AEO-9, 25 g of kerosene, and 110 g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of triazine polyoxyethylene ether in the emulsion to 0.2%, and obtain a drainage agent.

[0048] The surface tension of the drainage agent was measured using a surface tension meter at a test temperature of 25°C.

[0049] The drainage agent was placed at 80°C for 72 hours, cooled to 25°C, and deionized water was added to equal the volume of the original drainage agent, and then the surface tension after heat treatment was tested. The test results are shown in Table 1.

[0050] Table 1 Surface tension test of drainage agent

[0051]

[0052] According to the method of SY / T5755-2016, the drainage rate of the drainage aid was tested. The test results are shown in Table 2.

[0053] Table 2 Drainage aid test of drainage aid

[0054]

[0055]

[0056] After testing, in Examples 3-6, triazine-based amphoteric polyoxyethylene ether surfactants and nonionic surfactants such as AEO-9 are compounded, wherein the triazine-based amphoteric polyoxyethylene ether surfactant contains multiple polyoxyethylene ether side chains and multiple betaine zwitterionic groups, which makes it have a strong surface activity. After compounding with nonionic surfactants such as AEO-9, a good homogeneous microemulsion system is formed, and the surface tension is only 22.51-30.12 mN / m. And the triazine-based amphoteric polyoxyethylene ether surfactant contains a phenyl triazine structure The zwitterionic groups of sulfobetaine have higher heat resistance and can improve the temperature resistance of surfactants. After high-temperature heat treatment (80°C), the drainage agent still has a low surface tension. The drainage agent can meet the practical application of oil field fracturing technology and backflow under high temperature environment. And the drainage rate reaches 68.47-76.51%. This is because the triazine-based amphoteric polyoxyethylene ether surfactant and non-ionic surfactant form a microemulsion system. The microemulsion has a smaller droplet size and can effectively enter the pores of the rock. After fully contacting the rock surface, it significantly reduces the surface and interfacial tension, changes the surface wettability of the rock, and is conducive to reducing capillary resistance and the pressure of residual liquid after fracturing, thereby improving the drainage effect.

[0057] Comparative Example 1 did not add triazine-based amphoteric polyoxyethylene ether surfactant, and only used conventional nonionic surfactant AEO-9 as the main agent of the drainage aid; Comparative Example 2 used triazine-based amphoteric polyoxyethylene ether surfactant as the main agent of the drainage aid, and did not add nonionic surfactant AEO-9; both had large surface tensions and low drainage rates. It may be that in the drainage aid system, no nonionic surfactant-zwitterionic surfactant homogeneous microemulsion system was formed, resulting in a large surface tension of the drainage aid emulsion and a low drainage rate.

[0058] In Comparative Example 3, triazine polyoxyethylene ether and nonionic surfactant AEO-9 are used as the main agents of the drainage aid. Triazine polyoxyethylene ether does not contain amphoteric betaine ion groups, and its surface activity is low. The surface tension of the drainage aid emulsion is large, and the drainage rate is low.

[0059] Example 7

[0060] Add 45 g of n-butanol, 200 g of triazine-based amphoteric polyoxyethylene ether surfactant (prepared according to the method of Example 5), 100 g of non-ionic surfactant AEO-9, 20 g of kerosene, and 80 g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of the amphoteric polyoxyethylene ether surfactant in the emulsion to 0.5%, and obtain an ultra-low surface tension drainage aid.

[0061] Example 8

[0062] Add 45 g of n-butanol, 200 g of triazine-based amphoteric polyoxyethylene ether surfactant (prepared according to the method of Example 5), 100 g of non-ionic surfactant AEO-9, 20 g of kerosene, and 80 g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of the amphoteric polyoxyethylene ether surfactant in the emulsion to 0.8%, and obtain an ultra-low surface tension drainage agent.

[0063] Example 9

[0064] Add 45 g of n-butanol, 200 g of triazine-based amphoteric polyoxyethylene ether surfactant (prepared according to the method of Example 5), 100 g of non-ionic surfactant AEO-9, 20 g of kerosene, and 80 g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of the amphoteric polyoxyethylene ether surfactant in the emulsion to 1%, and obtain an ultra-low surface tension drainage aid.

[0065] Example 10

[0066] Add 45 g of n-butanol, 200 g of triazine-based amphoteric polyoxyethylene ether surfactant (prepared according to the method of Example 5), 100 g of non-ionic surfactant AEO-9, 20 g of kerosene, and 80 g of deionized water into a test tube, shake and mix, let stand to separate, collect the homogeneous emulsion, add deionized water to dilute, control the mass fraction of the amphoteric polyoxyethylene ether surfactant in the emulsion to 1.2%, and obtain an ultra-low surface tension drainage aid.

[0067] The test results of the surface tension and drainage rate of the drainage aid are shown in the following table.

[0068] Table 3 Surface tension and drainage rate test of drainage aid

[0069] Surface tension (mN / m) Aid drainage rate (%) Example 5 22.04 76.51 Example 7 18.14 85.04 Example 8 13.09 88.12 Example 9 7.96 86.29 Example 10 7.23 81.61

[0070] After testing, in Example 8, when the mass fraction of the triazine-based amphoteric polyoxyethylene ether surfactant in the drainage aid is 0.8%, the drainage rate is as high as 88.12%.

[0071] Although the above describes the specific implementation methods of the present invention, it does not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A method for preparing an ultra-low surface tension drainage agent, characterized in that: The preparation method comprises the following steps: adding 35-45 parts by weight of n-butanol, 80-200 parts by weight of triazine-based amphoteric polyoxyethylene ether surfactant, 100-150 parts by weight of nonionic surfactant, 20-30 parts by weight of kerosene, and 80-110 parts by weight of deionized water into a test tube, shaking and mixing, standing and stratifying, collecting a homogeneous emulsion, and adding deionized water for dilution to obtain an ultra-low surface tension drainage agent; The preparation method of the triazine-based amphoteric polyoxyethylene ether surfactant is as follows: Step (1), adding p-phenylenedioxy (dichloro-s-triazine), N-methyl-2-hydroxyethylamine, N,N-diisopropylethylamine, and tetrahydrofuran into a flask equipped with a condenser reflux tube, placing the flask in a water bath, stirring for reaction, and then distilling under reduced pressure, washing, and recrystallizing to obtain p-phenylenedioxy (N-methylhydroxyethylamino-s-triazine); Step (2), adding phenylenedioxy (N-methylhydroxyethylamino-s-triazine) and potassium hydroxide into a reaction kettle, evacuating the air, heating to a pre-reaction temperature, introducing ethylene oxide, heating to a reaction temperature, and regulating the pressure in the reaction kettle, cooling the material after the reaction, neutralizing, removing impurities by adsorption, filtering, and drying the filtrate to obtain triazine polyoxyethylene ether; Step (3), adding triazine polyoxyethylene ether, sodium 3-chloro-2-hydroxypropanesulfonate, and N,N-dimethylformamide into a reaction kettle, heating to the reaction temperature, cooling the material after the reaction, distilling under reduced pressure, washing the product, and drying to obtain a triazine-based amphoteric polyoxyethylene ether surfactant; In the step (1), the ratio of 1-dichloro-2-phenylenedioxy (dichloro-s-triazine), N-methyl-2-hydroxyethylamine, and N,N-diisopropylethylamine is 1 mol: (4.4-6) mol: (8-12) mol; In the step (2), the ratio of phenylenedioxy(N-methylhydroxyethylamino-s-triazine), potassium hydroxide, and ethylene oxide is 1 mol: (0.05-0.08) mol: (21-36) mol; In the step (3), the ratio of triazine polyoxyethylene ether to sodium 3-chloro-2-hydroxypropane sulfonate is 1 g:(0.45-0.72) g.

2. The method for preparing the ultra-low surface tension drainage agent according to claim 1, characterized in that: The nonionic surfactants include AEO-9, OP-10, and isomeric tridecanol polyoxyethylene ether E1306.

3. The method for preparing the ultra-low surface tension drainage agent according to claim 1, characterized in that: The mass fraction of the amphoteric polyoxyethylene ether surfactant in the ultra-low surface tension drainage agent is 0.2-1.2%.

4. The method for preparing the ultra-low surface tension drainage agent according to claim 1, characterized in that: In the step (1), the temperature of the water bath is 70-80° C., and the reaction time is 12-18 hours.

5. The method for preparing the ultra-low surface tension drainage agent according to claim 1, characterized in that: In the step (2), the temperature is raised to a pre-reaction temperature of 100-110° C., the reaction temperature is 130-140° C., and the pressure in the reactor is 0.3-0.35 MPa.

6. The method for preparing the ultra-low surface tension drainage agent according to claim 1, characterized in that: In the step (3), the reaction temperature is 100-120° C. and the reaction time is 48-72 h.

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