Micro-nano bubble-surfactant synergistic coal seam gas seepage water locking-dust falling method

Abstract

The invention provides a micro-nano bubble-surfactant synergistic coal seam gas seepage water locking-dust falling method, which adopts a multi-stage gas and dust comprehensive prevention and control means, adopts a pressure pump and a pumping system during liquid injection, and controls the pressure and the pumping flow rate to realize the water locking-dust falling of the coal seam gas seepage. And a micro-nano bubble-surface active liquid coupling medium is adopted to inject coal seam gas. After liquid injection is finished, the micro-nano bubble-surface active liquid coupling medium is stored in the coal seam, and seepage water locking and dust falling are conducted on the coal seam. Through seepage water locking, the desorption speed of coal seam gas is inhibited, and the emission strength of the gas is reduced; through dust falling, wetting reversal of the coal seam is achieved, the water content is increased, and therefore dust is reduced, and the safety of coal mining is improved.

Description

Technical field

[0001] my country's coal resources are widely distributed, and most of them rely on underground mining. Especially in the context of kilometer-deep well mining gradually evolving into the new normal of mining, the associated disasters during coal mining have become more complex, and there are significant differences between the north and the south. Taking the long flame coal mining in the Yonglong mining area in Shaanxi and the anthracite mining in the Laochang mining area in Yunnan as examples, the gas emission from the mining face can reach 15 and 34 m respectively. 3 / min, a difference of 19m 3 / min; the maximum drilling cuttings gas desorption index K1 values ​​were 0.20 and 1.75 mL / (g·min 1 / 2 ), with a difference of 1.55 mL / (g·min 1 / 2 Therefore, achieving efficient extraction and safe mining of coal seam gas is an important support for the high-quality development of my country's coal mines and an important link in the liberation of high-quality productivity.

[0002] On the other hand, with the continuous improvement of the mechanization level of the fully mechanized excavation working face, the dust hazard in the underground working area seriously threatens the physical and mental health of miners. The dust concentration in the fully mechanized excavation working face without dust prevention measures is generally 2000-3000 mg / m 3 Even if measures are taken, the working environment of most fully mechanized excavation working faces is still quite harsh. The maximum dust concentration at the working place of the fully mechanized excavator driver can reach 400-900mg / m 3 The dust concentration has far exceeded the national regulatory limit. The dust has seriously endangered the health of underground workers and threatened coal mine safety production. [Summary of the invention] The present invention aims to provide a coal seam gas seepage water lock-dust reduction method with synergistic effect of micro-nano bubbles and surfactants, so as to solve the current problems of coal body gas desorption and gas outflow, as well as excessive dust concentration.

[0003] The present invention is achieved by the following technical solutions: A method for water locking and dust reduction in coal seam gas seepage with synergistic effect of micro-nano bubbles and surfactants, comprising the following steps: S1. Coal seam occurrence analysis: Carry out liquid injection drilling and boundary control drilling according to the coal seam occurrence, and record the parameters; The injection borehole is used to inject micro-nano bubble-surfactant liquid coupling medium, and the boundary control borehole is used to control gas flow and discharge direction; S2. Preparation of a liquid-gas coupling medium: Adding a surfactant and water into a preparation container to obtain a surfactant aqueous solution, cyclically extracting and discharging the surfactant aqueous solution through a micro-nano bubble generator, and converting gas into micro-nano bubbles through a micro-nano bubble nozzle, which are mixed into the surfactant aqueous solution for coupling, thereby obtaining a micro-nano bubble-surfactant liquid coupling medium; S3. Seepage water lock: Using a pressure pump and a pumping system, the micro-nano bubble-surfactant liquid coupling medium described in step S2 is injected into the coal seam through a liquid injection borehole and stored therein, thereby performing seepage water lock on the coal seam to suppress the desorption rate of coal seam gas and reduce the emission intensity; S4. Dust reduction: Using a pressure pump and a pumping system, the micro-nano bubble-surfactant liquid coupling medium described in step S2 is injected into the coal seam through the injection drilling hole and stored in the coal seam to wet the coal seam, thereby achieving wetting reversal of the coal seam and increasing the moisture content.

[0004] The present invention provides a method for water locking and dust reduction in coal seam gas seepage with synergistic micro-nano bubble-surfactant effect, which is applicable to coal seam gas pre-extraction and working face mining. First, a micro-nano bubble generator is used to cyclically extract and discharge the surfactant aqueous solution, and cooperate with a micro-nano bubble nozzle to efficiently convert the gas into smaller and more uniform micro-nano bubbles, which are mixed into the surfactant aqueous solution to achieve stable coupling between the micro-nano bubbles and the liquid, forming a micro-nano bubble-surfactant liquid coupling medium. Second, coal seams usually have low permeability, and the pore structure is complex and irregular, with many branches and dead ends. During the injection period, a pressure pump and a pumping system are used to effectively inject the micro-nano bubble-surfactant liquid coupling medium into the coal seam through the injection borehole by controlling the pressure and pumping flow, thereby overcoming the resistance of the coal seam to the liquid, ensuring the uniform distribution of the gas-liquid coupling medium in the coal seam, and being able to flow along a path that is conducive to gas extraction, thereby improving its effect on improving the permeability of the coal seam and enhancing the gas extraction efficiency. Third, after the injection is completed, when the gas-liquid coupling medium is stored in the coal seam, the coal seam can be subjected to seepage water lock or dust reduction in steps, or the coal seam can be subjected to seepage water lock and dust reduction at the same time. The effect and action cycle can be determined by measuring and observing relevant working parameters.

[0005] When using a micro-nano bubble-surfactant coupling medium for dust reduction, the surfactant chemically reacts with water molecules through the hydrophilic and lipophilic groups in its inherent structure, altering the interfacial properties and wetting characteristics of water. This in turn promotes water diffusion and penetration across the solid surface of the coal seam, improving the contact efficiency between water and other substances and enhancing wetting properties. Furthermore, when micro-nano bubbles form, rise, and burst in water, they generate transient high pressure and micro-flow effects. This process disrupts the association structure of large molecular groups in the water, breaking them into more flexible small molecular clusters. Furthermore, the micro-nano bubbles alter the arrangement of water molecules, optimizing the surfactant's adsorption mechanism on the aqueous solution surface, allowing the surfactant to be more evenly distributed throughout the solution, further enhancing the solution's dust reduction capabilities. The synergistic effect of the micro-nano bubbles and surfactant significantly reduces surface tension, enabling the spray medium to better wet and agglomerate dust particles, thereby improving dust reduction efficiency in the coal seam while reducing water waste and the risk of secondary pollution.

[0006] Preferably, the type of the liquid injection drilling and the boundary control drilling in step S1 is one of through-layer drilling and along-layer drilling.

[0007] The present invention selects the appropriate drilling type and determines the drilling parameters according to the situation, such as drilling inclination, drilling diameter, drilling length, and drilling spacing, so that the drilling can selectively extend in different directions in the coal seam, optimize the flow path in the coal seam, promote the flow and extraction of gas, increase the pore connectivity in the coal seam, improve the permeability of the coal seam, improve the efficiency and effect of gas extraction, and can adapt to different coal seam occurrences and geological conditions.

[0008] Preferably, the surfactant in step S2 is one of cetyltrimethylammonium bromide, polyacrylamide, and polyethylene oxide.

[0009] The present invention uses a surfactant with surface-expanding, low-viscosity drag-reducing, and charge-modifying properties to modify the rheological properties of the liquid, reducing its surface tension and viscosity, enhancing its fluidity and permeability within the coal seam, and increasing its wettability, making it easier for the liquid to penetrate the pores of the coal seam. Different surfactants have different wettability and interactions with the coal seam. Selecting the appropriate surfactant can optimize the interaction between the liquid and the coal seam, increasing the liquid's retention time and effectiveness within the coal seam.

[0010] The coal seam control range and water injection volume are determined based on drilling parameters such as borehole diameter, borehole length, and borehole spacing, and the surfactant mass fraction is determined based on the water injection volume to obtain a surfactant aqueous solution. Preferably, the surfactant mass fraction is 0.005-0.05%.

[0011] Specifically, cetyltrimethylammonium bromide (CTAB) is a cationic surfactant with excellent surface activity and wetting properties. It can reduce the surface tension of liquids, increase the wettability of liquids on coal seams, and facilitate the penetration of liquids into the pores of coal seams. Polyacrylamide (PAM) is a polymer with excellent drag reduction and flocculation properties. It can reduce the viscosity of liquids and increase their fluidity, thereby reducing the flow resistance of liquids in coal seams. Polyethylene oxide (PEO) is a non-ionic polymer with excellent drag reduction and dispersibility. It can reduce the viscosity of liquids and increase their fluidity, thereby reducing the flow resistance of liquids in coal seams.

[0012] Preferably, the gas in step S2 is one of air, carbon dioxide and nitrogen.

[0013] By selecting appropriate gases, the present invention can control the generation, size, stability, and surface properties of micro-nano bubbles. These bubbles possess large specific surface area, high mass transfer efficiency, inherent surface potential, self-dissolution and pressurization, and surface drag reduction. By interacting with surfactants, they can better regulate the surface tension of the liquid, optimize the interaction between the gas-liquid coupling medium and the coal seam, and increase the liquid's penetration rate and efficiency in the coal seam, thereby enhancing gas extraction effectiveness.

[0014] More preferably, the micro-nano bubbles account for 45%-90% of the micro-nano bubble-surfactant liquid coupling medium.

[0015] Preferably, when the micro-nano bubble-surfactant liquid coupling medium is injected into the coal seam in steps S3 and S4, the pressure is set to low pressure, medium pressure, high pressure and ultra-high pressure, the low pressure is ≤10MPa, the medium pressure is 10-30MPa, the high pressure is 30-50MPa, and the ultra-high pressure is 50MPa.

[0016] This invention improves operational flexibility and applicability by setting different injection pressure levels (low pressure ≤ 10 MPa, medium pressure 10-30 MPa, high pressure 30-50 MPa, and ultra-high pressure 50 MPa). The appropriate injection pressure is selected based on the geological conditions of the coal seam and gas extraction requirements. Different injection pressures have varying effects on gas extraction effectiveness. Low-pressure injection reduces disturbance to the coal seam and is suitable for coal seams with high permeability. Medium-pressure injection provides sufficient pressure to allow the coupling medium to effectively penetrate the pores of the coal seam and is suitable for coal seams with average permeability. High-pressure and ultra-high-pressure injection overcome the high permeability resistance of the coal seam, allowing the coupling medium to penetrate deeper into the coal seam and are suitable for coal seams with poor permeability.

[0017] Preferably, when the micro-nano bubble-surfactant liquid coupling medium is injected into the coal seam in steps S3 and S4, the pumping flow rate is 10m3 / h、15m 3 / h、20m 3 / h、30m 3 / h、40m 3 / h、50m 3 / h、60m 3 / h or 70m 3 / h.

[0018] This invention offers multiple pumping flow rate options (10m³ / h, 15m³ / h, 20m³ / h, 30m³ / h, 40m³ / h, 50m³ / h, 60m³ / h, or 70m³ / h), allowing users to select the appropriate pumping flow rate based on the geological conditions of the coal seam and gas extraction requirements, thereby improving operational flexibility and applicability. Different pumping flow rates have varying effects on gas extraction effectiveness. A lower pumping flow rate increases the coupling medium's retention time in the coal seam, allowing it to interact more effectively with the coal seam and is suitable for coal seams with high permeability. A higher pumping flow rate increases the coupling medium's penetration rate in the coal seam, allowing it to reach deeper into the coal seam more quickly and is suitable for coal seams with low permeability.

[0019] Preferably, the injection time of the micro-nano bubble-surfactant liquid coupling medium into the coal seam in steps S3 and S4 is based on water coming out of the coal wall, water coming out of the boundary drilling hole, or a 30% drop in the injection pressure.

[0020] This invention ensures the uniformity of the coupling medium's injection volume and distribution within the coal seam by setting a termination condition for the injection time. When water appears at the coal wall, at the boundary borehole, or when the injection pressure drops by 30%, it indicates that the coupling medium has been fully injected into the coal seam or that the coal seam has reached saturation. Stopping injection at this point can prevent over-injection or under-injection.

[0021] Preferably, during the infiltration water lock in step S3, the boundary control borehole is in a natural discharge state.

[0022] In the present invention, during the seepage water lock, the boundary control borehole is in a natural discharge state, ensuring that the water in the seepage water lock process can be discharged smoothly through the borehole, thereby reducing the accumulation of seepage water in the coal seam and reducing the impact of seepage water on the permeability of the coal seam.

[0023] Preferably, during the permeable water lock in step S3, the permeable water lock effect and action period are determined by measuring the gas content of coal seams at different distances from the injection borehole, the drill cuttings gas desorption index K1 value, and the gas emission during excavation and mining.

[0024] Preferably, during the dust reduction step S4, the dust reduction effect and action period are determined by measuring the moisture content, wettability, dust production during mining, dust particle size, and dust concentration of coal seams at different distances from the injection borehole.

[0025] The beneficial effects of the present invention are as follows: The present invention provides a method for coal seam gas seepage water lock and dust reduction with synergistic micro-nano bubble-surfactant effect, which adopts a multi-stage comprehensive gas and dust prevention and control method. During the injection period, a pressure pump and a pumping system are used to control the pressure and pumping flow rate, and a micro-nano bubble-surfactant liquid coupling medium is used to inject coal seam gas. After the injection is completed, the micro-nano bubble-surfactant liquid coupling medium is stored in the coal seam, and the coal seam is subjected to seepage water lock and dust reduction. The seepage water lock suppresses the desorption rate of coal seam gas, reduces the gas outburst intensity, and realizes the prevention and control of gas outburst at the working face and safe and efficient mining. The dust reduction realizes the wetting reversal of the coal seam, increases the water content, and thus reduces the generation of dust, realizes the efficient prevention and control of dust in the underground mining working space of the coal mine, and improves the safety of coal mine mining.

Brief Description of the Drawings

[0026] Example 1 A method for water locking and dust reduction in coal seam gas seepage with synergistic effect of micro-nano bubbles and surfactants, comprising the following steps: S1. Coal seam occurrence analysis: according to the coal seam occurrence, liquid injection drilling 11 and boundary control drilling 10 are constructed and the parameters are recorded; S2. Preparation of liquid-gas coupling medium: Cetyltrimethylammonium bromide 1 and water are added to a preparation container 2 to obtain a cetyltrimethylammonium bromide aqueous solution. The cetyltrimethylammonium bromide aqueous solution is cyclically extracted and discharged through a ZJC-NM-200L micro-nano bubble generator 3. Air is converted into micro-nano bubbles through a micro-nano bubble nozzle, and the air is mixed with the surfactant aqueous solution in a micro-nano bubble-surfactant mixing tank 4 for coupling, thereby obtaining a micro-nano bubble-surfactant liquid coupling medium; S3. Seepage water lock: Using a pressure pump and a pumping system, the micro-nano bubble-surfactant liquid coupling medium described in step S2 is injected into the coal seam through a liquid injection borehole and stored therein, thereby performing seepage water lock on the coal seam to suppress the desorption rate of coal seam gas and reduce the emission intensity; S4. Dust reduction: Using a pressure pump and a pumping system, the micro-nano bubble-surfactant liquid coupling medium described in step S2 is injected into the coal seam through the injection drilling hole and stored in the coal seam to wet the coal seam, thereby achieving wetting reversal of the coal seam and increasing the moisture content.

[0027] The following tests were performed on the seepage water lock in step S3 and the dust reduction in step S4: a. Seepage water lock Test sample: anthracite 1-3mm dry particle coal sample.

[0028] Test conditions: Use copper mesh to evenly wrap 1-3mm dry particle coal sample of anthracite, place it in the prepared distilled water medium or micro-nano bubble-surfactant liquid coupling medium for infiltration for 30 minutes, filter the moisture on the surface of the coal sample, and place it in a blast drying oven to dry for 45 minutes until the surface of the coal sample is dry and free of water, retaining the moisture inside the pores of the coal sample, degas to 4Pa with a digital vacuum machine, discharge the dead space volume in the coal sample tank, fill it with methane with a concentration of 99.99%, place it in a constant temperature water bath at 30℃, maintain the equilibrium time for more than 3 hours at adsorption equilibrium pressures of 0.50, 1.50, and 2.50MPa, respectively, and record the cumulative desorption amount per unit mass.

[0029] Depend on Figure 2 It can be seen that when the adsorption equilibrium pressure is 0.50 MPa, the cumulative desorption amounts per unit mass of the coal sample in the distilled water medium and the coal sample in the micro-nano bubble-surfactant liquid-gas coupling medium are 0.9396 and 0.5408 mL, respectively. The cumulative desorption amount per unit mass of the coal sample in the micro-nano bubble-surfactant liquid-gas coupling medium is reduced by 42.44% compared with that of the coal sample in the distilled water medium.

[0030] Depend on Figure 3 It can be seen that when the adsorption equilibrium pressure is 1.50 MPa, the cumulative desorption amounts per unit mass of the coal sample with distilled water medium and the coal sample with micro-nano bubble-surfactant liquid-gas coupling medium are 1.7912 and 1.0762 mL respectively in 30 minutes. The cumulative desorption amount per unit mass of the coal sample with micro-nano bubble-surfactant liquid-gas coupling medium is reduced by 39.92% compared with that of the coal sample with distilled water medium.

[0031] Depend on Figure 4 It can be seen that when the adsorption equilibrium pressure is 2.50 MPa, the cumulative desorption amount per unit mass of the coal sample in distilled water medium and micro-nano bubble-surfactant liquid-gas coupling medium is 2.3736 and 1.7770 mL respectively in 30 minutes. The cumulative desorption amount per unit mass of the coal sample in micro-nano bubble-surfactant liquid-gas coupling medium is reduced by 25.13% compared with that in distilled water medium.

[0032] In summary, after liquid injection, the present invention uses a micro-nano bubble-surfactant coupling medium to lock coalbed methane through seepage. This significantly suppresses the desorption rate of coalbed methane at different adsorption equilibrium pressures. This reduction in the desorption rate and outburst intensity of coalbed methane effectively improves the safety of coalbed methane extraction and reduces the risk of gas accidents.

[0033] b. Dust reduction Test equipment: purification water curtain device.

[0034] Test conditions: Use tap water or micro-nano bubble-surfactant liquid coupling medium as the spray medium, use a water curtain device to perform multiple dust reduction operations on the closed tunnel space, and record the total dust reduction efficiency and respirable dust reduction efficiency respectively.

[0035] Depend on Figure 5 The results of four dust reduction tests show that the micro-nano bubble-surfactant liquid coupling medium significantly improves the overall dust reduction efficiency in closed tunnel spaces compared to conventional water curtain systems. For example, in the first test, the conventional water curtain achieved a total dust reduction efficiency of 44.14%, while the micro-nano bubble-surfactant liquid coupling medium achieved a 60.43% efficiency, a 36.90% improvement.

[0036] Depend on Figure 6Four dust reduction tests revealed that the micro-nano bubble-surfactant liquid coupled medium significantly improved the efficiency of respirable dust reduction in closed tunnel spaces compared to conventional water purification curtains using tap water. Taking the first test as an example, the conventional water purification curtain achieved a respirable dust reduction efficiency of 32.75%, while the micro-nano bubble-surfactant liquid coupled medium achieved a 44.84% efficiency, a 36.91% improvement.

[0037] In summary, after liquid injection, the present invention uses a micro-nano bubble-surfactant coupling medium to suppress coal seam gas. In multiple tests, this method has consistently improved the efficiency of total dust reduction and respirable dust reduction in enclosed tunnel spaces, effectively reducing dust concentrations within the tunnels. This helps improve the extraction working environment and enhances the safety and comfort of miners.

[0038] The above examples are merely provided to further illustrate the technical content of the present invention for easier understanding by the reader, but do not limit the embodiments of the present invention to these examples. Any extension or re-creation of the technology based on the present invention is protected by the present invention. The scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for water locking and dust reduction in coalbed gas seepage with synergistic micro-nano bubbles and surfactants, characterized by: The following steps are involved: S1. Coal seam occurrence analysis: Carry out liquid injection drilling and boundary control drilling according to the coal seam occurrence, and record the parameters; The injection borehole is used to inject micro-nano bubble-surfactant liquid coupling medium, and the boundary control borehole is used to control gas flow and discharge direction; S2. Preparation of a liquid-gas coupling medium: Adding a surfactant and water into a preparation container to obtain a surfactant aqueous solution, cyclically extracting and discharging the surfactant aqueous solution through a micro-nano bubble generator, and converting gas into micro-nano bubbles through a micro-nano bubble nozzle, which are mixed into the surfactant aqueous solution for coupling, thereby obtaining a micro-nano bubble-surfactant liquid coupling medium; S3. Seepage water lock: Using a pressure pump and a pumping system, the micro-nano bubble-surfactant liquid coupling medium described in step S2 is injected into the coal seam through a liquid injection borehole and stored therein, thereby performing seepage water lock on the coal seam to suppress the desorption rate of coal seam gas and reduce the emission intensity; S4. Dust reduction: Using a pressure pump and a pumping system, the micro-nano bubble-surfactant liquid coupling medium described in step S2 is injected into the coal seam through the injection drilling hole and stored in the coal seam to wet the coal seam, thereby achieving wetting reversal of the coal seam and increasing the moisture content.

2. The method for water locking and dust suppression of coalbed gas seepage with synergistic micro-nano bubbles and surfactants according to claim 1 is characterized by: The type of the liquid injection drilling and the boundary control drilling in step S1 is one of through-layer drilling and along-layer drilling.

3. The method for coalbed gas seepage water lock and dust reduction with synergistic micro-nano bubble-surfactant enhancement according to claim 1, characterized in that: The surfactant in step S2 is one of cetyltrimethylammonium bromide, polyacrylamide, and polyethylene oxide.

4. The method for water locking and dust suppression of coalbed gas seepage with synergistic micro-nano bubbles and surfactants according to claim 1 is characterized by: The gas in step S2 is one of air, carbon dioxide and nitrogen.

5. The method for water locking and dust suppression of coalbed gas seepage with synergistic micro-nano bubbles and surfactants according to claim 1, characterized in that: When the micro-nano bubble-surfactant liquid coupling medium is injected into the coal seam in steps S3 and S4, the pressure is set to low pressure, medium pressure, high pressure and ultra-high pressure, the low pressure is ≤10MPa, the medium pressure is 10-30MPa, the high pressure is 30-50MPa, and the ultra-high pressure is 50MPa; the pumping flow rate is 10m 3 / h、15m 3 / h、20m 3 / h、30m 3 / h、40m 3 / h、50m 3 / h、60m 3 / h or 70m 3 / h.

6. The method for water locking and dust suppression of coalbed gas seepage with synergistic micro-nano bubbles and surfactants according to claim 1, characterized in that: The injection time of the micro-nano bubble-surfactant liquid coupling medium into the coal seam in steps S3 and S4 is based on water coming out of the coal wall, water coming out of the boundary drilling hole, or a 30% drop in the injection pressure.

7. The method for water locking and dust suppression of coalbed gas seepage with synergistic micro-nano bubbles and surfactants according to claim 1, characterized in that: During the infiltration water lock in step S3, the boundary control borehole is in a natural discharge state.

8. The method for water locking and dust suppression of coalbed gas seepage with synergistic micro-nano bubbles and surfactants according to claim 1, characterized in that: During the permeation water lock in step S3, the permeation water lock effect and action period are determined by measuring the gas content of coal seams at different distances from the injection borehole, the drill cuttings gas desorption index K1 value, and the gas emission during excavation and mining.

9. The method for water locking and dust suppression of coalbed gas seepage with synergistic micro-nano bubbles and surfactants according to claim 1, characterized in that: During the dust reduction step S4, the dust reduction effect and action period are determined by measuring the moisture content, wettability, dust generation during mining, dust particle size, and dust concentration of coal seams at different distances from the injection borehole.

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