CN110743208A - Nano defoaming agent and preparation method and application thereof - Google Patents

Abstract

The invention relates to a nano defoaming agent, which is prepared by carrying out solvothermal reaction on aluminum oxide gel, polysiloxane and mixed alcohol in a solvent. The invention provides the nano defoaming agent with remarkable effect for oil and gas field exploitation, is environment-friendly, has simple preparation process, can solve the problem of excessive oil foam in the oil field exploitation process, and improves the oil production quality.

Description

Nano defoaming agent and preparation method and application thereof

Technical Field

The invention belongs to the field of defoaming agents, and particularly relates to a nano defoaming agent, and a preparation method and application thereof.

Background

Along with the increasingly deep exploration and development of oil and gas fields, the quality of well cementation influences the whole production process of the oil and gas fields, and is one of the most important links in the drilling engineering of the oil and gas wells. One of the initiating factors of this process is the large area use of water-based drilling fluids. In the drilling process, a foaming agent needs to be added into the drilling fluid to achieve the purpose of foam flooding, and the foam flooding can effectively improve the recovery ratio by about 10-25% under the general condition. However, the existence of a large amount of bubbles also causes the density reduction of the drilling fluid, the lubrication performance is poor, the efficiency of cooling the drill bit is all the time, the working efficiency of the mud pump is seriously affected, and certain difficulty is brought to the circulation of the drilling fluid. Especially, a large amount of air bubbles are mixed in the viscous petroleum, and the quality of the petroleum is seriously influenced.

Therefore, there is a need for effective methods to eliminate the foam present in large quantities in the displaced drilling fluid. In the process of oil and gas field exploitation, a common method is to add a defoaming agent to defoam the drilling fluid. The currently used antifoaming agents mainly include alcohol antifoaming agents, fatty acids and derivatives thereof, amides, phosphates, silicones, various halogen compounds, and the like. The silicone defoaming agent is also called organosilicon defoaming agent, is prepared by mechanically emulsifying silicone grease, emulsifier, waterproofing agent, thickening agent and the like by adding a proper amount of water, and is the most widely used defoaming agent at present. Its advantages are low surface tension, high surface activity, high defoaming power, low consumption, low cost, no mutual mixing with water and most organic substances, defoaming to most bubble medium, high thermal and chemical stability and physiological inertia. In foreign countries, the types of drilling fluid antifoaming agents are more, and the drilling fluid antifoaming agents include metal soaps, fatty acids, fatty acid esters, amides, alcohols, phosphate esters, solid inert materials such as perlite, rubber, leather powder and carbon black, and part of industrial leftovers, silicone oil, mineral oil and fluorocarbon. At present, most of defoaming agents adopted in oil and gas fields in China are prepared by compounding stearic acid and compounds thereof, polyether, octanol, fatty acid ester and other substances. Whatever the defoamer, it is necessary to compromise between the right water dispersibility and the right surface tension, which are important for defoamer performance and storage stability. However, the currently used antifoaming agents do not foam significantly during the production of oil and gas fields. Firstly, the time for eliminating the foam by the esters and the acids is longer; secondly, the current antifoaming agents reduce the foam removal effect in oil-water mixtures due to their poor hydrophobicity. Therefore, there is a need to develop a highly effective hydrophobic defoaming agent with general applicability to the application where rapid elimination of foam is required.

Disclosure of Invention

In order to solve the problems in the prior art, the inventor creatively mixes and disperses the nano aluminum oxide gel and the polysiloxane in the mixed alcohol continuous phase, and prepares the solid-liquid suspension type nano defoaming agent by adopting a solvent heat treatment method, so that the problem of excessive petroleum foam in the oil extraction process of an oil field can be solved, and the oil production quality is improved.

Specifically, the invention provides the following technical scheme:

a nano defoaming agent is prepared by carrying out solvothermal reaction on aluminum oxide gel, polysiloxane and mixed alcohol in a solvent.

Preferably, in the nano defoaming agent, the weight ratio of the aluminum oxide gel to the polysiloxane to the mixed alcohol is (12-26) to (3-10) to (5-14), preferably (15-24) to (4-7) to (7.5-11.7).

Preferably, in the nano defoaming agent, the solvent is an alcohol solvent, preferably ethanol and/or methanol.

Preferably, in the nano defoaming agent, the microstructure of the nano defoaming agent is a nanosheet layer.

Preferably, in the nano defoaming agent, the aluminum oxide gel is obtained by dissolving aluminum salt and urea in deionized water, hydrolyzing to form sol, standing to form gel, and finally removing the solvent, and more preferably, the aluminum salt is one or more selected from aluminum nitrate, aluminum sulfate, aluminum chloride and aluminum isopropoxide.

Preferably, in the nano defoaming agent, the polysiloxane is selected from polydimethylsiloxane, fluoroalkyl polysiloxane or phenyl polysiloxane.

Preferably, in the nano defoaming agent, the mixed alcohol contains a hydroxyl-terminated compound of formula (I), wherein n is ≧ 2,

more preferably, the mixed alcohol is obtained by heating a thermoplastic polyester, which is PET, with a diol selected from one or more of ethylene glycol, propylene glycol, butylene glycol, pentaerythritol, sorbitol, glycerol, neopentyl glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and tetraethylene glycol in the presence of a catalyst, most preferably zinc acetate, tetrabutyl titanate, isopropyl titanate or dibutyltin dilaurate.

Preferably, in the nano antifoaming agent, the temperature of the solvothermal reaction is 180-220 ℃ and the time is 18-30 h.

The invention also provides a preparation method of the nano defoaming agent, which comprises the following steps:

(1) in the presence of zinc acetate, mixing PET and neopentyl glycol together, and heating for reaction to obtain mixed alcohol;

(2) dissolving the mixed alcohol prepared in the step (1) and polydimethylsiloxane into an alcohol solvent to obtain a mixed solution for later use;

(3) dissolving aluminum salt and urea in deionized water, hydrolyzing to form sol, standing to form gel, and finally removing the solvent to obtain aluminum oxide gel;

(4) mixing the mixed solution prepared in the step (2) with the aluminum oxide gel prepared in the step (3), and carrying out a solvothermal reaction to obtain the nano defoaming agent;

more preferably, the method comprises the following steps:

(1) mixing 5-7 parts by weight of PET and 2-4 parts by weight of neopentyl glycol together in the presence of 0.5-0.7 part by weight of zinc acetate, and heating for reaction to obtain mixed alcohol;

(2) dissolving 7.5-11.7 parts by weight of the mixed alcohol prepared in the step (1) and 4-7 parts by weight of polydimethylsiloxane in 10-15 parts by weight of an alcohol solvent to obtain a mixed solution for later use;

(3) dissolving 5-8 parts by weight of aluminum salt and 7-13 parts by weight of urea in deionized water, hydrolyzing to form sol, standing to form gel, and finally removing the solvent to obtain aluminum oxide gel;

(4) and (3) mixing the mixed solution prepared in the step (2) with 15-24 parts by weight of the aluminum oxide gel prepared in the step (3), and carrying out solvothermal reaction at 180-220 ℃ for 18-30h to obtain the nano defoaming agent.

The invention also provides the application of the nano defoaming agent or the nano defoaming agent prepared by the preparation method in water-based drilling fluid.

The invention has the beneficial effects that:

the invention provides the nano defoaming agent with remarkable effect for oil and gas field exploitation, is environment-friendly, has simple preparation process, can solve the problem of excessive oil foam in the oil field exploitation process, and improves the oil production quality.

Drawings

FIG. 1 scanning electron micrograph of the nano-antifoam agent prepared in example 1.

FIG. 2 scanning electron micrograph of the nano-antifoam agent prepared in example 2.

FIG. 3 scanning electron micrograph of the nano-antifoam agent prepared in example 3.

FIG. 4 scanning electron micrograph of the nano-antifoam agent prepared in example 4.

FIG. 5 scanning electron micrograph of the nano-antifoam agent prepared in example 5.

FIG. 6 is a scanning electron micrograph of the nano-antifoam agent prepared in comparative example 1.

FIG. 7 is a scanning electron micrograph of the nano-antifoam agent prepared in comparative example 2.

FIG. 8 thermogravimetric analysis of the nano antifoam prepared in example 1.

Detailed Description

The nano defoaming agent, the preparation method and the application thereof are further illustrated by the following specific examples.

In the following examples, information on each reagent and apparatus used is shown in Table 1.

TABLE 1 information Table of reagents used in examples

Example 1

1. Cutting 10g of waste PET sheets into 5mm multiplied by 5mm sheets, placing the sheets in a beaker, pouring 20g of deionized water into the beaker, stirring the mixture by using a glass rod, and placing the beaker in an ultrasonic cleaning machine for cleaning for 20 minutes; the waste sheet PET in the beaker was then decanted, filtered through a 80 mesh screen, and dried to remove water.

2. Placing the flaky waste PET in 6g of sodium hydroxide solution, and repeating the step 1;

3. placing the flaky waste PET in 8g of dilute hydrochloric acid solution, and repeating the step 1;

4. placing the flaky waste PET in 20g of absolute ethyl alcohol, and repeating the step 1;

5. washing the flaky waste PET with 20g of deionized water, and repeating the step 1; finally, the waste PET sheets are placed in a 80-mesh screen for drying, naturally dried in the air for 3 hours, and then placed in a vacuum drying oven with the vacuum degree of 0.05MPa and the temperature of 60 ℃ for drying for 5 hours;

6. putting 10g of PET sheet obtained in the step 5 and 4g of neopentyl glycol into a three-neck flask connected with a stirring device, carrying out stirring and mixing in an oil bath kettle at 180 ℃ with a condensing reflux device at the rotating speed of 250rpm for 30 minutes, adjusting the oil bath temperature to 200 ℃, dropwise adding 0.5g of zinc acetate into a mixed system, and reacting for 1 hour under stirring;

7. dropwise adding the remaining 0.5g of zinc acetate into the system, regulating the rotating speed to 400rpm, continuously reacting in an oil bath kettle for 1 hour, taking the three-neck flask out of the oil bath kettle, continuously stirring the reaction system for 5 hours at room temperature, and stopping the reaction to obtain viscous liquid mixed alcohol;

8. mixing and dispersing 15g of the mixed alcohol obtained in the step 7 and 8g of polydimethylsiloxane in 20g of absolute ethyl alcohol solvent, and uniformly mixing for later use under the stirring of 400 rpm;

9. 10g of aluminum nitrate and 14g of urea are uniformly mixed and stirred in a single-neck flask, dissolved in 30g of deionized water, placed in a flat-bottom single-neck flask, placed on a magnetic stirrer, taken with a condensation reflux device, stirred and heated for 3 hours at 75 ℃, and the stirring speed is 150 r/min. The urea is hydrolyzed and reacts with aluminum ions in the solution to generate sol;

10. pouring the sol obtained in the step 9 into a polytetrafluoroethylene mold, then placing the polytetrafluoroethylene mold in a drying oven at 100 ℃ for heating and drying for 1 hour, and heating and dehydrating to prepare the aluminum oxide gel. And then mixing 30g of aluminum oxide gel with the product obtained in the step 8, placing the mixture in a PPL hydrothermal reaction kettle, screwing the reaction kettle, placing the reaction kettle in a drying box at 200 ℃ for reaction for 24 hours, and then gradually cooling the reaction kettle to room temperature along with the furnace to obtain the nano defoaming agent.

Example 2

1. Cutting 14g of waste PET sheets into 5mm multiplied by 5mm sheets, placing the sheets in a beaker, pouring 30g of deionized water into the beaker, stirring the mixture by using a glass rod, and placing the beaker in an ultrasonic cleaning machine for cleaning for 20 minutes; the waste sheet PET in the beaker was then decanted, filtered through a 80 mesh screen, and dried to remove water.

2. Placing the flaky waste PET in 12g of sodium hydroxide solution, and repeating the step 1;

3. placing the flaky waste PET in 16g of dilute hydrochloric acid solution, and repeating the step 1;

4. placing the flaky waste PET in 30g of absolute ethyl alcohol, and repeating the step 1;

5. placing the flaky waste PET into a container, washing the PET with 40g of deionized water, and repeating the step 1; finally, the waste PET sheets are placed in a 80-mesh screen for drying, naturally dried in the air for 3 hours, and then placed in a vacuum drying oven with the vacuum degree of 0.05MPa and the temperature of 60 ℃ for drying for 5 hours;

6. putting 14g of PET sheet obtained in the step 5 and 8g of neopentyl glycol into a three-neck flask connected with a stirring device, carrying out stirring and mixing in an oil bath kettle at 180 ℃ with a condensing reflux device at the rotating speed of 250rpm for 30 minutes, adjusting the oil bath temperature to 200 ℃, dropwise adding 0.8g of zinc acetate into a mixed system, and reacting for 1 hour under stirring;

7. dropwise adding the remaining 0.6g of zinc acetate into the system, regulating the rotating speed to 400rpm, continuously reacting in an oil bath kettle for 1 hour, taking the three-neck flask out of the oil bath kettle, continuously stirring the reaction system for 5 hours at room temperature, and stopping the reaction to obtain viscous liquid mixed alcohol;

8. mixing and dispersing 23.4g of the mixed alcohol obtained in the step 7 and 14g of polydimethylsiloxane in 30g of absolute ethyl alcohol solvent, and uniformly mixing for later use under the stirring of 400 rpm;

9. 16g of aluminum nitrate and 26g of urea are uniformly mixed and stirred in a single-neck flask, dissolved in 40g of deionized water, placed in a flat-bottom single-neck flask, placed on a magnetic stirrer, taken with a condensation reflux device, stirred and heated for 3 hours at 75 ℃, and the stirring speed is 150 r/min. The urea is hydrolyzed and reacts with aluminum ions in the solution to generate sol;

10. pouring the sol obtained in the step 9 into a polytetrafluoroethylene mold, then placing the polytetrafluoroethylene mold in a drying oven at 100 ℃ for heating and drying for 1 hour, and heating and dehydrating to prepare the aluminum oxide gel. And then mixing 48g of aluminum oxide gel with the product obtained in the step 8, placing the mixture in a PPL hydrothermal reaction kettle, screwing the reaction kettle, placing the reaction kettle in a drying box at 200 ℃ for reaction for 24 hours, and then gradually cooling the reaction kettle to room temperature along with the furnace to obtain the nano defoaming agent.

Example 3

1. Cutting 12g of waste PET sheets into 5mm multiplied by 5mm sheets, placing the sheets in a beaker, pouring 30g of deionized water into the beaker, stirring the mixture by using a glass rod, and placing the beaker in an ultrasonic cleaning machine for cleaning for 20 minutes; the waste sheet PET in the beaker was then decanted, filtered through a 80 mesh screen, and dried to remove water.

2. Placing the flaky waste PET in 10g of sodium hydroxide solution, and repeating the step 1;

3. placing the flaky waste PET in 12g of dilute hydrochloric acid solution, and repeating the step 1;

4. placing the flaky waste PET in 24g of absolute ethyl alcohol, and repeating the step 1;

5. placing the flaky waste PET into a container, washing the PET with 30g of deionized water, and repeating the step 1; finally, the waste PET sheets are placed in a 80-mesh screen for drying, naturally dried in the air for 3 hours, and then placed in a vacuum drying oven with the vacuum degree of 0.05MPa and the temperature of 60 ℃ for drying for 5 hours;

6. putting 12g of PET sheet obtained in the step 5 and 6g of neopentyl glycol into a three-neck flask connected with a stirring device, carrying out stirring and mixing in an oil bath kettle at 180 ℃ with a condensing reflux device at the rotating speed of 250rpm for 30 minutes, adjusting the oil bath temperature to 200 ℃, dropwise adding 0.6g of zinc acetate into a mixed system, and reacting for 1 hour under stirring;

7. dropwise adding the remaining 0.6g of zinc acetate into the system, regulating the rotating speed to 400rpm, continuously reacting in an oil bath kettle for 1 hour, taking the three-neck flask out of the oil bath kettle, continuously stirring the reaction system for 5 hours at room temperature, and stopping the reaction to obtain viscous liquid mixed polyol;

8. mixing and dispersing 19.2g of the mixed polyol obtained in the step 7 and 12g of polydimethylsiloxane in 26g of absolute ethyl alcohol solvent, and uniformly mixing for later use under the stirring of 400 rpm;

9. 14g of aluminum nitrate and 18g of urea are uniformly mixed and stirred in a single-neck flask, dissolved in 30g of deionized water, placed in a flat-bottom single-neck flask, placed on a magnetic stirrer, taken with a condensation reflux device, stirred and heated for 3 hours at 75 ℃, and the stirring speed is 150 r/min. The urea is hydrolyzed and reacts with aluminum ions in the solution to generate sol;

10. pouring the sol obtained in the step 9 into a polytetrafluoroethylene mold, then placing the polytetrafluoroethylene mold in a drying oven at 100 ℃ for heating and drying for 1 hour, and heating and dehydrating to prepare the aluminum oxide gel. And then mixing 36g of aluminum oxide gel with the product obtained in the step 8, placing the mixture in a PPL hydrothermal reaction kettle, screwing the reaction kettle, placing the reaction kettle in a drying box at 200 ℃ for reaction for 24 hours, and then gradually cooling the reaction kettle to room temperature along with the furnace to obtain the nano defoaming agent.

Example 4

Example 4 the starting materials and preparation method were the same as those of example 1 of the present invention except that example 4 was a defoaming agent prepared by solvothermal reaction of 52g of aluminum oxide gel, 20g of polysiloxane and 10g of mixed alcohol in 70g of ethanol.

Example 5

Example 5 and example 1 of the present invention were identical in starting material and preparation method, except that example 4 was a defoaming agent prepared by solvothermal reaction of 24g of aluminum oxide gel, 6g of polysiloxane and 28g of mixed alcohol in 50g of ethanol.

Comparative example 1

Comparative example 1 the raw materials and preparation method of the mixed alcohol and aluminum oxide gel were the same as example 1 except that in comparative example 1, 30g of aluminum oxide gel was mixed with 20g of anhydrous ethanol, placed in a PPL hydrothermal reaction vessel, the reaction vessel was tightened, placed in a 200 ℃ dry box to react for 24 hours, and then gradually cooled to room temperature with the furnace, and the aluminum oxide obtained by the solvothermal reaction was uniformly mixed with 15g of mixed alcohol and 8g of polydimethylsiloxane to obtain the defoaming agent of this comparative example.

Comparative example 2

Comparative example 2 the raw materials and preparation methods of example 1 of the present invention were the same except that comparative example 2 was a defoaming agent prepared by solvothermal reaction of 20g of aluminum oxide gel, 30g of polysiloxane and 8g of mixed alcohol in 64g of ethanol.

The nano-aluminum oxide spherical particles prepared in the above examples and comparative examples were subjected to the following characterization:

1. analysis by scanning electron microscope

The defoaming agents prepared in examples and comparative examples were subjected to scanning electron microscope SEM examination, and the results are shown in fig. 1 to 7. The microstructure of the nano defoaming agent prepared in the embodiments 1 to 3 is of a nano-sheet stacking structure and is compact, bubbles generated in the oil extraction process can be effectively eliminated through the contact of the nano-sheet structure with a large specific surface area, and the microstructure of the nano defoaming agent prepared in the embodiments 4 and 5 is of a nano-sheet layer, but the structure is loose. The micro-structures of the defoaming agents prepared in comparative examples 1 and 2 are irregular block-shaped bodies, the size difference is large, the specific surface area is small when the defoaming agents are in contact with bubbles, and the defoaming effect is weak.

2. pH detection

The nano defoaming agent prepared in the example 1 is tested by using a pH meter, and the result shows that the nano defoaming agent has a pH value of 7.2, is neutral and is more beneficial to eliminating bubbles in petroleum.

3. Thermogravimetric analysis

Thermogravimetric analysis was performed on the nano antifoaming agent prepared in example 1 by using TG-DTA, and it can be seen from fig. 8 that the nano antifoaming agent prepared in example 1 has an initial decomposition temperature of about 252 ℃ under heating, has good heat resistance, and is suitable for oil extraction operation in oil field.

4. Viscosity detection

The viscosity detection of the nano defoaming agent prepared in the embodiment 1-3 by using a Brookfield DV-II type viscometer shows that the viscosity range of the defoaming agent prepared in the embodiment 1 is 180-203 mPa.s, the viscosity range of the defoaming agent prepared in the embodiment 2 is 124-209 mPa.s, and the viscosity range of the defoaming agent prepared in the embodiment 3 is 210-263 mPa.s, which indicates that the nano defoaming agent has lower viscosity and can meet the requirements of mixing and dispersing other liquid substances.

5. Defoaming Properties

According to the specification of HG/T4783-. The defoaming agents prepared in comparative examples 1 and 2 have a poor defoaming effect when contacting with bubbles because the shapes of the defoaming agents are not regular nanosheets.

In conclusion, the invention provides the nano defoaming agent which is environment-friendly and simple in preparation process, and when the nano defoaming agent is used in the drilling fluid, the problem of excessive petroleum foam in the oil extraction process of an oil field can be solved, and the oil production quality is improved.

Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims (10)

1. The nano defoaming agent is characterized by being prepared by carrying out solvothermal reaction on aluminum oxide gel, polysiloxane and mixed alcohol in a solvent.

2. The nano antifoaming agent of claim 1, wherein the weight ratio of the aluminum oxide gel, polysiloxane, and mixed alcohol is (12-26): (3-10): (5-14), preferably (15-24): (4-7): (7.5-11.7).

3. The nano antifoaming agent according to claim 1 or 2, wherein the solvent is an alcoholic solvent, preferably ethanol and/or methanol.

4. The nano antifoaming agent of any of claims 1-3, wherein the microstructure of the nano antifoaming agent is a nano-platelet layer.

5. The nano antifoaming agent according to any of claims 1 to 4, wherein the aluminum oxide gel is obtained by dissolving aluminum salt and urea in deionized water, hydrolyzing to form sol, standing to form gel, and finally removing solvent, preferably, the aluminum salt is selected from one or more of aluminum nitrate, aluminum sulfate, aluminum chloride and aluminum isopropoxide.

6. The nano antifoaming agent of any of claims 1-5, wherein the polysiloxane is selected from the group consisting of polydimethylsiloxane, fluoroalkyl polysiloxane, and phenyl polysiloxane.

7. The nano antifoaming agent of any of claims 1-6, wherein the mixed alcohol comprises a hydroxyl terminated compound of formula (I), wherein n ≧ 2,

preferably, the mixed alcohol is obtained by heating a thermoplastic polyester, which is PET, with a diol selected from one or more of ethylene glycol, propylene glycol, butylene glycol, pentaerythritol, sorbitol, glycerol, neopentyl glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and tetraethylene glycol in the presence of a catalyst, more preferably, zinc acetate, tetrabutyl titanate, isopropyl titanate or dibutyltin dilaurate.

8. The nano antifoaming agent of any of claims 1-7, wherein the temperature of the solvothermal reaction is 180-220 ℃ and the time is 18-30 h.

9. The method for preparing a nano antifoaming agent according to any one of claims 1 to 8, characterized by comprising the steps of:

(1) in the presence of zinc acetate, mixing PET and neopentyl glycol together, and heating for reaction to obtain mixed alcohol;

(2) dissolving the mixed alcohol prepared in the step (1) and polydimethylsiloxane into an alcohol solvent to obtain a mixed solution for later use;

(3) dissolving aluminum salt and urea in deionized water, hydrolyzing to form sol, standing to form gel, and finally removing the solvent to obtain aluminum oxide gel;

(4) mixing the mixed solution prepared in the step (2) with the aluminum oxide gel prepared in the step (3), and carrying out a solvothermal reaction to obtain the nano defoaming agent;

preferably, the method comprises the following steps:

(1) mixing 5-7 parts by weight of PET and 2-4 parts by weight of neopentyl glycol together in the presence of 0.5-0.7 part by weight of zinc acetate, and heating for reaction to obtain mixed alcohol;

(2) dissolving 7.5-11.7 parts by weight of the mixed alcohol prepared in the step (1) and 4-7 parts by weight of polydimethylsiloxane in 10-15 parts by weight of an alcohol solvent to obtain a mixed solution for later use;

(3) dissolving 5-8 parts by weight of aluminum salt and 7-13 parts by weight of urea in deionized water, hydrolyzing to form sol, standing to form gel, and finally removing the solvent to obtain aluminum oxide gel;

(4) and (3) mixing the mixed solution prepared in the step (2) with 15-24 parts by weight of the aluminum oxide gel prepared in the step (3), and carrying out solvothermal reaction at 180-220 ℃ for 18-30h to obtain the nano defoaming agent.

10. Use of the nano-antifoaming agent of any of claims 1 to 8 or the nano-antifoaming agent prepared by the preparation method of claim 9 in water-based drilling fluids.

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