CN117402600A

CN117402600A - Nanoemulsion treating agent for realizing surface wetting reversal of coal seam

Info

Publication number: CN117402600A
Application number: CN202311336958.3A
Authority: CN
Inventors: 吴洋; 昝杨; 鲁红升; 黄志宇; 王金玉; 戴姗姗; 王宝刚
Original assignee: Southwest Petroleum University
Current assignee: Southwest Petroleum University
Priority date: 2023-10-13
Filing date: 2023-10-13
Publication date: 2024-01-16

Abstract

The invention discloses a nanoemulsion treating agent for realizing surface wetting reversal of coal bed gas, and belongs to the technical field of coal bed gas exploitation. The nanoemulsion treating agent has the characteristics of small dosage of surfactant and small adsorption loss of surfactant, and can realize the change of the wettability of the coal bed surface and improve the yield of a coal bed gas well. The nano emulsion treating agent is prepared by a micro emulsion dilution method, and the principle is as follows: the microemulsion has excellent stability and is easy to store. When in use, a certain amount of microemulsion is added into well fluid according to mass fraction. Meanwhile, when the microemulsion is prepared by the microemulsion dilution method, the addition amount is 0.2-1%, and the surfactant content in the formed nanoemulsion is 0.04-0.2%, so that the use of the surfactant can be reduced.

Description

Nanoemulsion treating agent for realizing surface wetting reversal of coal seam

Technical Field

The invention belongs to the technical field of coal bed methane exploitation, and particularly relates to a nanoemulsion treating agent for realizing surface wetting reversal of coal bed methane.

Background

With the increasing exhaustion of traditional energy sources such as petroleum, natural gas and the like, new energy sources such as coal bed gas, shale gas and the like are more and more paid attention to, and fracturing, such as hydraulic fracturing, is adopted to develop a ground energy reservoir. The method supports the gas production firstly and then coal mining, and improves the gas production efficiency. However, since the permeability of coal is extremely low, the gas permeability is poor, resulting in extremely low gas recovery rate. In order to increase the air permeability of coal and the yield of a coal bed gas well, hydraulic fracturing measures are often carried out, but most of coal beds are hydrophilic, so that water pressed into the coal beds in the hydraulic fracturing process cannot be completely reversely discharged due to the fact that most of coal beds are wet, so that a phenomenon of 'water lock' is formed, namely, water blocks the flow of gas, and the subsequent production, drainage and extraction of gas are blocked. The wetting reversal method can change the wettability of the coal bed near the bottom of the well, change the wettability of the coal bed from hydrophilic to hydrophilic, change capillary pressure from resistance to power, reduce or remove the phenomenon of 'water lock', increase the flowback of water, reduce the damage to the coal bed, and further improve the yield of the coal bed gas well.

The prior art provides a method for realizing the gas wetting reversal of the core surface by using a cationic fluorocarbon surfactant. The method uses a wet-reversal treatment agent comprising a cationic fluorocarbon surfactant FC911, a quaternary ammonium salt surfactant, and a polar fluid. Preferably, the wet reversal agent is formed by mixing FC911, cetyltrimethylammonium bromide and water. This method can transform the gas reservoir rock surface into a state with strong gas wettability and good stability. Coalbed methane is different from conventional natural gas reservoirs in the aspects of reservoir characteristics, seepage characteristics, development mechanisms, exploitation modes and the like.

The prior art provides a method for realizing gas wetting reversal of a coal rock surface by using a cationic fluorocarbon surfactant. The used wetting reversal treatment agent contains cationic fluorocarbon surfactant perfluoro octyl sulfonamide propyl amine oxide, nonionic surfactant fatty alcohol polyoxyethylene ether and polar fluid; the preferred wet-reversal agent used is formulated from perfluorooctyl sulfonamide propyl amine oxide, fatty alcohol polyoxyethylene ether, and water. The invention can transform the surface of the gas reservoir rock into gas wettability and has good stability. But the usage amount of the surfactant is higher, and the economic cost is higher. Meanwhile, the adsorption quantity of the surfactant on the surface of the coal seam is large, and a large amount of adsorption can occur after the surfactant enters the coal seam, so that the effective invasion depth of the surfactant in the coal seam is shallower. On the other hand, the permeability of the primary pores is very low, coal dust and rich clay minerals in the coal bed are easy to hydrate when meeting water, and meanwhile, after a large amount of surfactant is adsorbed, the coal bed matrix is easy to expand to cause blockage and damage to the coal bed pores.

Disclosure of Invention

Aiming at the technical defects of large adsorption loss amount, shallow effective invasion depth and large usage amount of the surface active agent on the surface of the coal bed of the conventional surface active agent type wetting reversal treating agent, the invention aims to provide the nano emulsion treating agent for realizing the surface wetting reversal of the coal bed gas.

The invention is realized by the following technical scheme:

the nanoemulsion treating agent for realizing the surface wetting reversal of the coal seam is obtained by adding microemulsion into water containing an additive for dilution; the nano emulsion treating agent is an oil-in-water emulsion preparation;

the mass fraction of the microemulsion is 0.2-1 wt%.

Preferably, the surfactant content in the nanoemulsion treatment agent is 0.04wt% to 0.2wt%.

Preferably, the microemulsion is mainly prepared from the following raw materials in parts by mass:

6-12 wt% of nonionic surfactant, 6-12 wt% of anionic surfactant, 7-15 wt% of cosurfactant, 8-15 wt% of oil phase and the balance of water;

the additives include pH regulator, antibacterial agent, antiseptic, antiscaling agent and penetrating agent.

The additives mainly comprise: and the pH regulator is used for regulating the acid-base property of the fracturing fluid so as to meet specific geological conditions and rock characteristics. Antibacterial agent: preventing the fracturing fluid from being polluted by microorganisms in the using process. Corrosion inhibitor: preventing the fracturing fluid from corroding the well bore and equipment. Antiscaling agent: for preventing the formation of scale on the well wall and equipment. Penetrant: for increasing the permeability of fluids in the formation and improving the effect of wet-reversal. The above additives also pertain to the constituents that are contained in conventional well fluids.

Emulsions are generally divided into aqueous phase, oil phase and emulsifier. The surfactant and cosurfactant in the raw materials are emulsifying agents, water is water phase, and n-heptane is oil phase. At the same time, there is a synergistic interaction between the surfactant and the cosurfactant. Cosurfactants may improve the compatibility of the surfactant between the oil and water phases. They can reduce the hydrophilicity or hydrophobicity of the surfactant, allowing the surfactant to be better dispersed in the continuous phase. This helps to avoid phase separation and precipitation and improves the stability of the microemulsion. Meanwhile, the microemulsion is easy to generate phase separation and micelle aggregation in the preparation process, and the cosurfactant can form an amorphous colloidal layer at the interface of the microemulsion to prevent the phase separation and micelle aggregation of the microemulsion.

Preferably, the preparation method of the microemulsion comprises the following steps: and selecting a nonionic surfactant, an anionic surfactant, a cosurfactant and an oil phase according to the corresponding parts by weight, sequentially adding the nonionic surfactant, the anionic surfactant, the cosurfactant and the oil phase into water, mixing and stirring to form the microemulsion.

The nano emulsion is prepared by a micro emulsion dilution method, and the principle is as follows: the microemulsion has excellent stability and is easy to store. When in use, a certain amount of microemulsion is added into well fluid according to mass fraction. Meanwhile, when the microemulsion is prepared by the microemulsion dilution method, the addition amount is 0.2-1%, and the surfactant content in the formed nanoemulsion is 0.04-0.2%, so that the use of the surfactant can be reduced. When the addition amount of the nano emulsion is too low, the nano emulsion is unstable, and when the addition amount is too high, the performance of the nano emulsion is improved to a limited extent.

The well fluid is mainly composed of water, and the balance of water and water is additive. The additives mainly comprise: and the pH regulator is used for regulating the acid-base property of the fracturing fluid so as to meet specific geological conditions and rock characteristics. Antibacterial agent: preventing the fracturing fluid from being polluted by microorganisms in the using process. Corrosion inhibitor: preventing the fracturing fluid from corroding the well bore and equipment. Antiscaling agent: for preventing the formation of scale on the well wall and equipment. Penetrant: for increasing the permeability of fluids in the formation and improving the effect of wet-reversal.

The positive effects of the technical means and the value range in the technical scheme are explained as follows:

nonionic surfactants act as emulsifiers and wet reversal treatments. The reason for controlling the mass fraction of the nonionic surfactant to be 6.00% -12.00% is that: enough surfactant can prepare the microemulsion with good and stable performance, and the content of the surfactant can be adjusted according to actual conditions so as to achieve different wetting inversion effects. The nonionic surfactant has good emulsifying property and dispersing property. They are capable of forming a molecular layer of surfactant between the aqueous phase and the oil phase and promoting dispersion and stabilization of the oil phase particles by lowering interfacial tension. This helps to uniformly disperse the oil phase in the water phase, forming a stable micelle or microemulsion structure. The adverse effect of the excessive mass fraction is that the consumption of the surfactant is large, the economic cost is high, the adverse effect of the excessive mass fraction is that the microemulsion has poor performance and the wetting inversion effect is low;

the anionic surfactant acts as an emulsifier. The reason for controlling the mass fraction of the anionic surfactant to be 6.00% -12.00%: anionic surfactants are effective in reducing the surface tension of the liquid interface. The anionic surfactant can reduce interfacial tension between the oil phase particles (or micelles) and the aqueous phase, so that the oil phase particles are easier to disperse in the aqueous phase and form a stable micelle structure. This helps to reduce the energy consumption of the microemulsion and improves the stability of the system. Meanwhile, anionic surfactants typically have a negative charge in microemulsions. These negative charges may form charge attractive forces with positive ions or other ions in the aqueous phase, thereby preventing micelle aggregation and phase separation of the microemulsion from occurring. The existence of the anionic surfactant can form an electric double-layer structure, and repulsive force between charges plays an important role in the stability of the microemulsion.

The cosurfactant acts as an auxiliary agent. The reason for controlling the mass fraction of the cosurfactant to be 7.00% -15.00% is that: the proper amount of cosurfactant can increase the number and size of micelles in the emulsion and enhance the emulsification effect. The presence of the cosurfactant may help the primary surfactant better encapsulate and disperse the oily water phase to form a uniformly dispersed emulsion. An adverse effect of this mass fraction value being too large is that excessive amounts of cosurfactants may cause invert emulsification or emulsion instability. Too high a cosurfactant concentration may disrupt the micelle structure, leading to phase separation and precipitation. An adverse effect of too small is that the effect of enhancing emulsification is poor.

The nonpolar solvent is the oil phase of the emulsion. Nonpolar solvents play an important role in forming microemulsions. They are generally used as the basis for an oil phase, combined with an aqueous phase and a surfactant, to form a stable emulsion structure. The nonpolar solvent has lower polarity and smaller interaction force between polar molecules, has better compatibility with polar components in the water phase, and is favorable for forming micelle and stable micelle structure. The reason for controlling the mass fraction of the oil phase to be 7.00% -15.00% is as follows: the amount of oil added in the emulsion has an effect on the formation and stability of the emulsion. Generally, an oil phase with a shorter carbon chain is selected. Shorter carbon chain lengths facilitate diffusion and interaction of molecules, enabling better compatibility of the oil phase with the aqueous phase and formation of the microemulsion structure. The number of carbons is a common range between 6 and 12 because shorter carbon chain lengths facilitate diffusion and interaction of molecules, enabling the oil phase to be better compatible with the water phase and form an emulsion structure. At the same time, too short a carbon chain may result in low oil phase solubility, while too long a carbon chain may limit molecular movement and diffusion, affecting microemulsion formation and stability. Meanwhile, the addition amount of the oil phase may affect the emulsification efficiency. Too low an oil addition may result in incomplete emulsification and formation of unstable microemulsions. Too high an oil addition may lead to difficult emulsification or reduced stability of the emulsion.

Preferably, the nonionic surfactant includes any one of dodecylphenol polyoxyethylene ether, tween-80 and fluorocarbon surfactant.

Preferably, the fluorocarbon surfactant is fluorocarbon surfactant JH-501.

Preferably, the anionic surfactant comprises sodium fatty alcohol polyoxyethylene ether sulfate and/or sodium dodecyl sulfate.

Preferably, the cosurfactant comprises any one of n-propanol, n-butanol and isobutanol.

Preferably, the oil phase includes any one of n-heptane, n-hexane and cyclohexane.

Compared with the prior art, the invention has at least the following technical effects:

the invention provides a nanoemulsion treating agent for realizing surface wetting reversal of a coal bed gas, which has the characteristics of small surfactant consumption and small surfactant adsorption loss, and can realize the change of the surface wetting of the coal bed and improve the yield of the coal bed gas well.

The nano emulsion treating agent is prepared by emulsifying a surfactant into nano emulsion, and the principle is as follows: 1. the nano emulsion is an oil-in-water emulsion, has a spherical structure, is provided with a surfactant serving as an emulsifier and is distributed on an oil-water interface of the emulsion, the surfactant in the state has good stability, and compared with a surfactant solution, emulsion droplets can reduce the adsorption of the surfactant on the surface of coal rock, reduce the adsorption loss and improve the effective invasion depth of the surfactant. 2. Nanoemulsions have lower surface tension than surfactants. The lower the surface tension, the lower its capillary force, as defined in the capillary, under the same wetting conditions and pore diameter. The nanoemulsion is more likely to enter deep into the pores of the coal seam than the surfactant solution at the same pressure. 3. At the same time, the magnitude of the surface tension directly influences the spreading of the droplet on the solid surface. When the surface tension is large, the internal cohesive force to which the droplet is subjected is large, and it is difficult to overcome the resistance of the surface tension, so that the droplet is not easily spread. In contrast, when the surface tension is small, the liquid droplets are subjected to a small internal cohesive force, the resistance of the surface tension of the object is easily overcome, and the spreading on the solid surface can be better performed. Because the nanoemulsion has lower surface tension than the surfactant, the spreading coefficient is larger, the resistance of the surface tension of the coal bed is easily overcome, and the nanoemulsion can be spread on the surface of the coal bed better.

(III) preparing nano emulsion by a micro emulsion dilution method, wherein the principle is as follows: the microemulsion has excellent stability and is easy to store. When in use, a certain amount of microemulsion is added into well fluid according to mass fraction. Meanwhile, when the microemulsion is prepared by the microemulsion dilution method, the addition amount is 0.2-1%, and the surfactant content in the formed nanoemulsion is 0.04-0.2%, so that the use of the surfactant can be reduced. When the addition amount of the nano emulsion is too low, the nano emulsion is unstable, and when the addition amount is too high, the performance of the nano emulsion is improved to a limited extent.

Drawings

FIG. 1 is a schematic view of the contact angle of a water/air/coal sample system of process 1;

FIG. 2 is a schematic view of the contact angle of the water/air/coal sample system of process 2;

FIG. 3 is a schematic view of the contact angle of the water/air/coal sample system of process 3;

FIG. 4 is a schematic view of the contact angle of the water/air/coal sample system of process 4;

FIG. 5 is a schematic view of the contact angle of the water/air/coal sample system of process 5;

FIG. 6 is a schematic view of the contact angle of the water/air/coal sample system of process 6;

FIG. 7 is a schematic view of the contact angle of the water/air/coal sample system of process 7;

FIG. 8 is a schematic view of the contact angle of the water/air/coal sample system of process 8;

FIG. 9 is a schematic illustration of the surface tension of a TW-80 solution according to example 9, validated 0.5% in test one;

FIG. 10 is a schematic representation of the surface tension of a 0.5% solution of fluorocarbon surfactant JH-501 in test one, example 9;

FIG. 11 is a schematic illustration of the surface tension of a 0.5% AES solution, as demonstrated in test one, example 9;

FIG. 12 is a schematic representation of the surface tension of 0.5% fluorocarbon-AES nanoemulsion identified in test one, example 9;

FIG. 13 is a schematic drawing showing the unit adsorption amount of 0.5% AES nanoemulsion on pulverized coal in adsorption amount experimental verification.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the following examples, which are to be construed as merely illustrative and not limitative of the scope of the invention, but are not intended to limit the scope of the invention to the specific conditions set forth in the examples, either as conventional or manufacturer-suggested, nor are reagents or apparatus employed to identify manufacturers as conventional products available for commercial purchase.

The process of injecting fluids into a coal seam can be briefly described as two phases: a seepage stage and a imbibition stage. During the seepage phase, fluid injected into the coal seam may flow along the seam fracture under the influence of external pressure. Subsequently, under the action of capillary force, water flow spontaneously seeps in the micropores and enters deeper into the pores. Lower surface tension may increase the imbibition effect of the fluid in the pores.

Example 1:

10.00% of dodecylphenol polyoxyethylene ether (OP-10), 10.00% of Sodium Dodecyl Sulfate (SDS), 20% of n-butanol and 10% of n-heptane are added into water in sequence to be mixed and stirred, and then the OP10-SDS compound microemulsion is formed.

1g of OP10-SDS microemulsion is taken and added into 199g of water, and then stirred, so that 0.5% OP10-SDS nanoemulsion is formed, and the nanoemulsion is fluid with wetting inversion property.

Example 2:

10.00% of fluorocarbon surfactant JH-501, 10.00% of fatty alcohol polyoxyethylene ether sodium sulfate (AES), 20% of n-butanol and 10% of n-heptane are added into water in sequence for mixing and stirring, and then the fluorocarbon surfactant JH-501-AES compound microemulsion is formed.

1g of fluorocarbon surfactant JH-501-AES microemulsion is taken and added into 199g of water, and then stirred, so that 0.5% OP10-AES nanoemulsion is formed, and the nanoemulsion is fluid with wetting inversion characteristic.

The experiment verification was performed by selecting the above example 2 as an experimental example.

Test one: verification of the Effect of the sample of example 2 above on the coal rock contact angle

Contact angle to demonstrate the effect of wetting reversal. As shown in the contact angle graph, the liquid drop can generate a left contact angle and a right contact angle with the coal surface. CA stands for their average value. Generally, contact angles are described in terms of CA.

The experimental method for the surface wetting reversal of the coal bed comprises the following steps: firstly polishing the surface of a coal sample to be smooth, then cleaning the coal sample with ethanol and water, and then drying the coal sample. And immersing the dried coal sample in the wetting reversal treating agent, treating for 3 hours at the temperature of 25 ℃, and then drying at room temperature.

Treatment 1: the contact angle of the sample of the embodiment 2 after the coal rock is treated is selected, and the contact angle of the water/air/coal sample system is as follows: CA:104.174. a specific illustration is shown in fig. 1.

Treatment 2: the contact angle of the sample of the embodiment 2 after the coal rock is treated is not selected, and the contact angle of the water/air/coal sample system is as follows: CA:48.188. a specific illustration is shown in fig. 2.

Example 3:

10.00% of fluorocarbon surfactant JH-501 (wetting reversal agent), 10.00% of fatty alcohol polyoxyethylene ether sodium sulfate (AES) (surfactant), 20% of n-butanol (cosurfactant) and 10% of n-hexane (oil phase) are sequentially added into water to be mixed and stirred, and then the fluorocarbon surfactant JH-501AES compound microemulsion is formed.

The experiment verification was performed by selecting the above example 3 as an experimental example.

The experimental method for the surface wetting reversal of the coal seam is the same as in example 2.

Treatment 3: the contact angle of the sample of the embodiment 3 after the coal rock is treated is selected, and the contact angle of the water/air/coal sample system is as follows: CA:102.482 deg.. A specific illustration is shown in fig. 3.

Example 4:

the differences are: the wetting reversal agent was Tween-80 (TW-80), the surfactant was SDS, and the same procedure as in example 3 was repeated.

Treatment 4: the contact angle of the sample of the embodiment 4 after the coal rock is treated is selected, and the contact angle of the water/air/coal sample system is as follows: CA:101.924 deg.. A specific illustration is shown in fig. 4.

Example 5:

the differences are: the wetting reversal agent was tween-80, the surfactant was sodium fatty alcohol polyoxyethylene ether sulfate (AES), and the other was the same as in example 3.

Treatment 5: the contact angle of the sample of the embodiment 5 after the coal rock is treated is selected, and the contact angle of the water/air/coal sample system is as follows: CA:96.225 deg.. A specific illustration is shown in fig. 5.

Example 6:

the differences are: the wetting reversal agent was fluorocarbon surfactant JH-501, and the surfactant was sodium fatty alcohol polyoxyethylene ether sulfate (AES), otherwise the same as in example 4.

Treatment 6: the contact angle of the sample of the embodiment 6 after the coal rock is treated is selected, and the contact angle of the water/air/coal sample system is as follows: CA:104.174 deg.. A specific illustration is shown in fig. 6.

In examples 3 to 6, the amount of the surfactant added was constant in each example, because the total amount of the surfactant added was 20% when the microemulsion was prepared even though the types of the surfactants were different. Therefore, when the nano emulsion is diluted into 0.5 percent and 1 percent, the addition amount of the surfactant is 0.1 to 0.2 percent.

Example 7:

the differences are: the amount of the nanoemulsion type wetting reversal agent was 1%, and the same as in example 3 was repeated.

Treatment 7: the contact angle of the sample of the embodiment 7 after the coal rock is treated is selected, and the contact angle of the water/air/coal sample system is as follows: CA:107.981 deg.. A specific illustration is shown in fig. 7.

Example 8:

the differences are: 0.5% fluorocarbon surfactant JH-501 and 1% surfactant are sodium fatty alcohol polyoxyethylene ether sulfate (AES), and the other steps are the same as those in example 4.

Treatment 8: the contact angle of the sample of the embodiment 8 after the coal rock is treated is selected, and the contact angle of the water/air/coal sample system is as follows: CA:78.558 deg.. A specific illustration is shown in fig. 8.

Example 9:

preparing a TW-80 solution with the concentration of 0.5%, an AES solution with the concentration of 0.5%, a fluorocarbon surfactant JH-501 solution with the concentration of 0.5%, and a fluorocarbon-AES nanoemulsion with the concentration of 0.5%, and measuring the surface tension of the nanoemulsion respectively.

Example 9 demonstrates that nanoemulsions use less surfactant when the same surface tension is reached.

Purpose of testing tension: to compare the data on the surface tension of the surfactant solution and the nanoemulsion, it is demonstrated that nanoemulsions can achieve lower surface tension with less surfactant content.

The surface tension of the TW-80 solution with 0.5 percent, the AES solution with 0.5 percent and the fluorocarbon surfactant JH-501 solution with 0.5 percent are respectively as follows: 38.729, 35.621, 36.788. Specific illustrations are shown in fig. 9, 11 and 10.

The 0.5% fluorocarbon-AES nanoemulsion had a surface tension of: 28.430. a specific illustration is shown in fig. 12.

The conclusion proves that the nanoemulsion has lower surface tension than the surfactant, so that the spreading coefficient is larger, the resistance of the surface tension of the coal bed is easily overcome, and the nanoemulsion can be spread on the surface of the coal bed better.

And (3) adsorption quantity experiment verification:

and carrying out dynamic adsorption experiments through the displacement device.

140g of coal powder passing through a 60 mesh sieve was packed in a sand-packed tube. The nanoemulsion was used as a displacement fluid, the displacement flow rate was fixed at 0.1mL/min, and the pressure change at the injection end during displacement was recorded by a pressure gauge. And collecting the effluent at the outflow end of the sand filling pipe at regular intervals, and measuring the concentration of the surfactant in the effluent by an ultraviolet-visible diffuse reflection spectrophotometer. And calculates the unit adsorption amount on the pulverized coal.

Taking 0.1% AES surfactant solution (containing 0.1% AES surfactant) and 0.5% AES nanoemulsion (diluted with 20% AES, 20% n-butanol and 10% n-hexane) as examples.

The 0.5% AES nanoemulsion was prepared from a microemulsion containing 20% AES surfactant, so the 0.1% surfactant AES solution and the 0.5% AES nanoemulsion contained the same surfactant.

Results: as shown in fig. 13, the abscissa represents the body volume (45 mL: 1 PV), and the ordinate represents the unit adsorption amount on the pulverized coal.

The unit adsorption amount of the 0.5% AES nanoemulsion on the coal dust is smaller, and the loss of the surfactant in the fluid is smaller.

Finally, it should be noted that: the foregoing description is only of the preferred embodiments of the invention and is not intended to limit the scope of the invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The nanoemulsion treating agent for realizing the surface wetting reversal of the coal seam is characterized by being obtained by diluting a microemulsion in water containing an additive; the nano emulsion treating agent is an oil-in-water emulsion preparation;

the mass fraction of the microemulsion is 0.2-1 wt%.

2. A nanoemulsion treatment agent for achieving surface wet reversal of coal seam gas according to claim 1, wherein the surfactant content in the nanoemulsion treatment agent is 0.04% -0.2% by weight.

3. The nanoemulsion treatment agent for realizing the surface wetting reversal of coal seam gas according to claim 1, wherein the microemulsion is mainly prepared from the following raw materials in parts by mass:

4. A nanoemulsion treatment agent for realizing the surface wetting reversal of coal seam gas according to claim 3, wherein the preparation method of the microemulsion is as follows: and selecting a nonionic surfactant, an anionic surfactant, a cosurfactant and an oil phase according to the corresponding parts by weight, sequentially adding the nonionic surfactant, the anionic surfactant, the cosurfactant and the oil phase into water, mixing and stirring to form the microemulsion.

5. The nanoemulsion treatment agent for achieving surface wet reversal of coal seam gas according to claim 4, wherein the nonionic surfactant comprises any one of dodecylphenol polyoxyethylene ether, tween-80 and fluorocarbon surfactant.

6. The nanoemulsion treatment agent for achieving surface wet reversal of coal seam gas according to claim 5, wherein the fluorocarbon surfactant is fluorocarbon surfactant JH-501.

7. A nanoemulsion treatment agent for achieving surface wet reversal of coal seam gas according to claim 4, wherein the anionic surfactant comprises sodium fatty alcohol polyoxyethylene ether sulfate and/or sodium dodecyl sulfate.

8. A nanoemulsion treatment agent for achieving reversal of surface wetting of coal seam gas as defined in claim 4 wherein the co-surfactant comprises any one of n-propanol, n-butanol and isobutanol.

9. A nanoemulsion treatment agent for achieving surface wet reversal of coal seam gas according to claim 4, wherein the oil phase comprises any one of n-heptane, n-hexane and cyclohexane.