METHOD FOR COAL SEAM GAS SEEPAGE DISPLACEMENT, SEEPAGE WATER LOCKING AND DUST REDUCTION

Abstract

The present invention provides a method for coal seam gas seepage displacement, seepage water locking and dust reduction. During the injection period, a pressure pump and pumping system are used to control the pressure and pumping flow rate, and a micro-nano bubble surface active liquid coupling medium is used for seepage displacement of coal seam gas, ensuring efficient discharge or extraction of coal seam gas. After the injection is completed, the micro-nano bubbles surface-active liquid coupling medium is stored in the coal seam, and the coal seam is subjected to seepage water locking and dust reduction. Through the seepage displacement, the seepage velocity of coal seam gas is increased. Through the seepage water locks, the desorption rate of coal seam gas is suppressed. Through the dust reduction, the wetting reversal of coal seams can be achieved, and the moisture content is increased, thereby reducing the generation of dust.

Claims

1. A method for coal seam gas seepage displacement, seepage water locking and dust reduction, comprising the following steps: S1. Coal seam occurrence analysis: conducting liquid injection boreholes and boundary control boreholes based on the occurrence of coal seams, and recording parameters; wherein the liquid injection boreholes are configured for injecting micro-nano bubble surface active liquid coupling medium, and the boundary control boreholes is used for controlling gas flow and discharge direction; S2. Preparation of liquid gas coupling medium: adding surfactants 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 the gas into micro-nano bubbles through a micro-nano bubble nozzle for mixing into the surfactant aqueous solution for coupling, thereby obtaining a micro-nano bubble surface active liquid coupling medium; S3. Seepage displacement: using a pressure pump and a pumping system, injecting the micro-nano bubble surface active liquid coupling medium in step S2 into the coal seam through the liquid injection boreholes to perform seepage displacement of coal seam gas, achieving coal seam gas discharge or extraction; S4. Seepage water locking: when the micro-nano bubble surface active liquid coupling medium described in step S3 is stored in the coal seam, performing seepage water locking to the coal seam to realize the desorption speed suppression and emission intensity reduction of the coal seam gas; S5. Dust reduction: when the micro-nano bubble surface active liquid coupling medium described in step S3 is stored in the coal seam, moistening the coal seam to achieve the reversal of coal seam wetting and increasing the water content.

2. The method according to claim 1, wherein the type of liquid injection boreholes and boundary control boreholes in step S1 is one of through-layer boreholes or bedding boreholes.

3. The method according to claim 1, wherein the surfactant in step S2 is one of hexadecyltrimethylammonium bromide, polyacrylamide, or polyethylene oxide.

4. The method according to claim 1, wherein the gas in step S2 is one of air, carbon dioxide, or nitrogen.

5. The method according to claim 1, wherein when the micro-nano bubble surface active liquid coupling medium in step S3 is injected into the coal seam, the pressure is set to low pressure, medium pressure, high pressure, and ultra-high pressure; the low pressure is 10 MPa, the medium pressure is 10-30 MPa, the high pressure is 30-50 MPa; and the ultra-high pressure is 50 MPa; the pumping flow rate is 10 m.sup.3/h, 15 m.sup.3/h, 20 m.sup.3/h, 30 m.sup.3/h, 40 m.sup.3/h, 50 m.sup.3/h, 60 m.sup.3/h or 70 m.sup.3/h.

6. The method according to claim 1, wherein an injection time for injecting the micro-nano bubble surface active liquid coupling medium in step S3 into the coal seam is based on water outflow from the coal wall, water outflow from the boundary boreholes, or a 30% decrease in water injection pressure.

7. The method according to claim 1, wherein during the seepage displacement in step S3, when coal seam gas is discharged, the boundary control borehole is in a natural discharge state; when the coal seam gas is extracted, the boundary control boreholes are merged into extraction pipeline network; during the seepage water locking in step S4, the boundary control borehole is in a natural discharge state.

8. The method according to claim 1, wherein during the seepage displacement in step S3, the effect and action period of the seepage displacement are determined by the concentration and flow rate of the boundary control boreholes.

9. The method according to claim 1, wherein during the seepage water locking in step S4, the effect and action period of the seepage water locking are determined by measuring the coal seam gas content at different distances from the liquid injection boreholes, the gas desorption index K1 value of the drilling cuttings, and the gas emission volume during excavation and mining.

10. The method according to claim 1, wherein during the dust reduction in step S5, the dust reduction effect and action period are determined by measuring the coal seam moisture content, wetting degree, dust generation volume during mining operations, dust particle size, and dust concentration at different distances from the injection boreholes.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0042] FIG. 1 is a schematic diagram of the synergistic effect enhancement of micro-nano bubbles and surfactants in the coal seam gas seepage displacement seepage water locking dust reduction method of the present invention;

[0043] FIG. 2 is a comparative analysis of the instantaneous flow rate of anthracite and long flame coal displacement by micro-nano bubble surface active liquid coupling medium;

[0044] FIG. 3 is a comparative analysis of the instantaneous flow rate of anthracite and long flame coal displacement by distilled water medium;

[0045] FIG. 4 is a comparative analysis of the gas permeability of anthracite and long flame coal displacement by micro-nano bubble surface active liquid coupling medium;

[0046] FIG. 5 shows a comparative analysis of the gas permeability of anthracite and long flame coal displacement by distilled water medium;

[0047] FIG. 6 shows the comparison between the desorption rate and cumulative desorption amount of 1-3 mm anthracite dry particle coal samples under adsorption equilibrium pressure of 0.50 MPa using micro-nano bubble surface active liquid coupling medium and distilled water medium;

[0048] FIG. 7 shows the comparison between the desorption rate and cumulative desorption amount of 1-3 mm anthracite dry particle coal samples under adsorption equilibrium pressure of 1.50 MPa using micro-nano bubble surface active liquid coupling medium and distilled water medium;

[0049] FIG. 8 shows the comparison between the desorption rate and cumulative desorption amount of 1-3 mm anthracite dry particle coal samples under adsorption equilibrium pressure of 2.50 MPa using micro-nano bubble surface active liquid coupling medium and distilled water medium;

[0050] FIG. 9 is a comparison chart of the dust reduction efficiency of micro-nano bubble surfactant liquid coupling medium and conventional water medium on total dust;

[0051] FIG. 10 is a comparison chart of the dust reduction efficiency of micro-nano bubble surfactant liquid coupling medium and conventional water medium for respiratory dust.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The specific technical solution of the present invention will be described below in conjunction with FIG. 1 and Embodiment 1.

[0053] As shown in FIG. 1, surfactant 1; preparation container 2; micro-nano bubble generator 3; micro-nano bubble surfactant mixing tank 4; pressure pump 5; micro-nano bubbles surface active liquid coupling medium injected into coal seams 6; coal seam gas 7; coal seam 8; pumping system 9; boundary control borehole 10; liquid injection borehole 11.

Embodiment 1

[0054] A method for coal seam gas seepage displacement, seepage water locking and dust reduction with synergistic effect of micro-nano bubbles and surfactants, comprising the following steps: [0055] S1. Coal seam occurrence analysis: constructing of liquid injection boreholes 11 and boundary control borehole 10 based on the occurrence of coal seams, and recording parameters; [0056] S2. Preparation of liquid gas coupling medium: adding hexadecyltrimethylammonium bromide 1 and water into a preparation container 2 to obtain a hexadecyltrimethylammonium bromide aqueous solution; cyclically extracting and discharging the hexadecyltrimethylammonium bromide aqueous solution through a ZJC-NM-200 L micro-nano bubble generator 3, and converting the gas into micro-nano bubbles through a micro-nano bubble nozzle for mixing it with the surfactant aqueous solution in a micro-nano bubble surfactant mixing tank 4 for coupling, thereby obtaining a micro-nano bubble surfactant coupling medium; [0057] S3. Seepage displacement: using a pressure pump 5 and a pumping system 9, injecting the micro-nano bubble surface active liquid coupling medium 6 in step S2 into the coal seam 8 through the liquid injection boreholes 11 to perform seepage displacement of coal seam gas 7, achieving coal seam gas discharge or extraction; [0058] S4. Seepage water locking: when the micro-nano bubble surface active liquid coupling medium 6 described in step S3 is stored in the coal seam 8, performing seepage water locking to realize the desorption speed suppression and emission intensity reduction of the coal seam gas; [0059] S5. Dust reduction: when the micro-nano bubble surface active liquid coupling medium 6 described in step S3 is stored in the coal seam 8, moistening the coal seam to achieve the reversal of coal seam wetting, and increases the water content.

[0060] The following tests are carried out on the seepage displacement in step S3, the seepage water locking in step S4, and the dust reduction in step S5, respectively:

a. Seepage Displacement

Test Samples: Anthracite, Long Flame Coal.

[0061] Test conditions: place standard anthracite coal sample with a diameter of 2550 mm and standard long flame coal sample with a diameter of 2550 mm in a saturation chamber, connect a vacuum pump to evacuate at a pumping rate of 4 L/s for 6 hours; then place the micro-nano bubble surface active liquid gas coupling medium or distilled water medium in a liquid supply tank, and pressurize it with a pressure pump to reach and stabilize at 1.50 MPa for saturation, thereby obtaining coal sample treated with the micro-nano bubble surface active liquid gas coupling medium and those treated with the distilled water medium.

[0062] Under axial pressure of 3 and 5 MPa, and confining pressure of 3 and 5 MPa, use the coal samples treated with the micro-nano bubble surface active liquid gas coupling medium or distilled water medium to conduct seepage displacement of methane (99.99% concentration), and measure the instantaneous flow rate and gas permeability in the stable state seepage conditions, respectively.

[0063] According to FIG. 2, under the axial pressures of 3 and 5 MPa, the confining pressures of 3 and 5 MPa, and an inlet pressure of 1 MPa, the instantaneous flow rates of anthracite coal displaced by the micro-nano bubble surface active liquid gas coupling medium are 3.13 and 3.05 mL.Math.min.sup.1, respectively; while for the long flame coal, the instantaneous flow rates are 3.36 and 3.28 mL.Math.min.sup.1, respectively.

[0064] According to FIG. 3, under the axial pressures of 3 and 5 MPa, the confining pressures of 3 and 5 MPa, and the inlet pressure of 1.25 MPa, the instantaneous flow rates of anthracite coal displaced by the micro-nano bubble surface active liquid gas coupling medium are 1.95 and 1.25 mL.Math.min.sup.1, respectively; while for the long flame coal, the instantaneous flow rates are 2.35 and 1.96 mL.Math.min.sup.1, respectively.

[0065] According to FIG. 4, under axial pressure of 3 and 5 MPa, confining pressure of 3 and 5 MPa, and inlet pressure of 1 MPa, when the anthracite coal is displaced by micro-nano bubble surface active liquid gas coupling medium, the gas measured permeability is 0.01041 and 0.01017 mD, respectively; while for the long flame coal they are 0.01124 and 0.01093 mD, respectively.

[0066] According to FIG. 5, under the axial pressure of 3 and 5 MPa, the confining pressure of 3 and 5 MPa, and the inlet pressure of 1.25 MPa, when anthracite coal is displaced by micro-nano bubble surface active liquid gas coupling medium, the gas permeability measured are 0.00648 and 0.00426 mD, respectively; while for the long flame coal, they are 0.00781 and 0.00652 mD, respectively.

[0067] Compared to the distilled water medium, the micro-nano bubble surface active liquid gas coupling medium increases the instantaneous flow rate and gas permeability of the anthracite coal by 1.61 times and 2.44 times, under the axial/confining pressures of 3 MPa and 5 MPa, respectively, and enhances the gas permeability by 1.61 times and 2.39 times, respectively. For long-flame coal, the micro-nano bubbles surface active liquid gas coupling medium increases the instantaneous flow rate by 1.43 times and 1.67 times under the axial/confining pressures of 3 MPa and 5 MPa, respectively, and improves the gas permeability by 1.44 times and 1.68 times, respectively.

[0068] In summary, during the liquid injection period, the present invention adopts the micro-nano bubble surface active liquid coupling medium to carry out the seepage displacement of the coal seam gas, which has good applicability to coal types. Under different axial and confining pressures, it can significantly improve the instantaneous flow rate and gas permeability of the coal seam, and has good stability and reliability, ensuring efficient discharge or extraction of coal seam gas.

b. Seepage Water Locking

[0069] Test sample: dry granular anthracite coal sample of 1-3 mm.

[0070] Test conditions: Uniformly wrap the dry granular anthracite coal sample (1-3 mm) with copper mesh and place it in the prepared water medium or micro-nano bubble surfactant liquid coupling medium for 30 minutes for spontaneous imbibition; filter the surface moisture of the coal sample and place it in a blast drying oven for 45 minutes until the surface of the coal sample is dry and free of water, while retaining the moisture inside the pores of the coal sample. Degas the sample to 4 Pa using a digital vacuum machine to discharge the dead space volume in the coal sample container, and then charge the container with 99.99% methane and place it in a constant temperature water bath at 30 C. Maintain equilibrium for over 3 hours at adsorption equilibrium pressures of 0.50, 1.50, and 2.50 MPa, respectively, and record the cumulative desorption amounts per unit mass at each pressure.

[0071] According to FIG. 6, when the adsorption equilibrium pressure is 0.50 MPa, the cumulative desorption amounts per unit mass at 30 minutes for the coal sample treated with the distilled water medium and the micro-nano bubble surface active liquid gas coupling medium are 0.9396 and 0.5408 mL, respectively. The micro-nano bubble surface active liquid gas coupling medium treated sample is reduced by 42.44% compared to the distilled water medium-treated coal sample.

[0072] According to FIG. 7, when the adsorption equilibrium pressure is 1.50 MPa, the cumulative desorption amounts per unit mass at 30 minutes for the coal sample treated with the distilled water medium and the coal sample in the micro-nano bubble surface active liquid gas coupling medium are 1.7912 and 1.0762 mL, respectively. The cumulative desorption per unit mass of the coal sample in the micro-nano bubble surface active liquid gas coupling medium is reduced by 39.92% compared to the distilled water medium-treated coal sample.

[0073] According to FIG. 8, when the adsorption equilibrium pressure is 2.50 MPa, the cumulative desorption amounts per unit mass at 30 minutes for the coal sample treated with the distilled water medium and the micro-nano bubble surface active liquid gas coupling medium coal sample are 2.3736 and 1.7770 mL, respectively. The cumulative desorption amount per unit mass of the micro-nano bubble surface active liquid gas coupling medium coal sample is reduced by 25.13% compared to the distilled water medium-treated coal sample.

[0074] In summary, after the injection is completed, the present invention uses the micro-nano bubble surface active liquid coupling medium to lock the seepage water of coalbed methane, which can significantly suppress the desorption speed of coalbed methane under different adsorption equilibrium pressures. The reduction of desorption speed and emission intensity of coalbed methane can effectively improve the safety of coalbed methane extraction and reduce the risk of gas accidents.

c. Dust Reduction

[0075] Testing equipment: purified water curtain device.

[0076] Test conditions: tap water or micro-nano bubble surfactant liquid coupling medium is used as the spray medium, the enclosed roadway space is subject to multiple dust suppression through the water curtain device, and the total dust suppression efficiency and respiratory dust suppression efficiency are recorded respectively.

[0077] According to FIG. 9, after four dust reduction tests, compared to conventional purification water curtain devices, the use of micro-nano bubble surfactant liquid coupling media can significantly improve the total dust suppression efficiency of enclosed tunnel spaces. Taking the first test as an example, the total dust suppression efficiency of the conventional purification water curtain was 44.14%, while the coupling medium of micro-nano bubbles surfactant liquid was 60.43%, which increased by 36.90% compared to the previous test.

[0078] From FIG. 10, it can be seen that after four dust reduction tests, compared with the conventional purification water curtain using tap water medium, the use of micro-nano bubble surfactant liquid coupling medium can significantly improve the respiratory dust reduction efficiency of enclosed tunnel space. Taking the first test as an example, the respiratory dust reduction efficiency of the conventional purification water curtain was 32.75%, while the coupling medium of micro-nano bubbles surfactant liquid was 44.84%, an increase of 36.91% compared to the previous test.

[0079] In summary, after the injection is completed, the present invention uses the micro-nano bubble surface active liquid coupling medium to reduce dust in coal seam gas. In multiple tests, it has been found to improve the dust reduction efficiency of total dust and respiratory dust in enclosed tunnel spaces, effectively reducing the dust concentration in the tunnel. This helps to improve the working environment for mining and enhance the safety and comfort of miners.

[0080] The above embodiments are only used to further illustrate the technical content of the present invention for the convenience of readers to understand more easily, but it does not mean that the embodiments of the present invention are limited to these. Any technical extension or recreation made in accordance with the present invention is protected by the present invention. The scope of protection of the present invention shall be subject to the claims.