Hole sealing system and method for high-concentration gas extraction caused by mixed gas injection

Abstract

The invention discloses a mixed gas injection induced gas high-concentration extraction hole sealing system and method, and belongs to the technical field of underground coal mine gas extraction, and the system comprises a drilling module used for drilling through layer holes, penetrating coal seams and forming extraction drill holes; the plugging module is used for plugging the drill hole through expanding agents at the two ends; the vacuumizing module is used for vacuumizing the environment between the expanding agents at the two ends; the gas mixing module is used for mixing the mixed gas and injecting the mixed gas into the coal seam; and the monitoring and extraction module is used for observing the gas extraction concentration and extracting internal gas. According to the hole sealing system and method for high-concentration gas extraction caused by mixed gas injection, gas dissipation can be prevented, the construction method is simple, the mixed gas is safe and free of danger, CO2 outburst cannot be caused, current mine production is not affected, and the system and method are safe, economical and efficient; the brand-new method solves the problem that the gas extraction concentration of the low-permeability coal seam of the deep mine is low, and the pre-extraction and extraction efficiency of the crossing drill hole is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas drainage in underground coal mines, and in particular to a gas high-concentration drainage sealing hole system and method by injecting a mixed gas. Background Art

[0002] As the main energy source in China, coal has undergone decades of large-scale mining, and the number of deep mines across the country has accounted for a considerable proportion. At present, most coal seams in China are low-permeability coal seams. Due to the long coal-forming era, high degree of coal body metamorphism, and the characteristics of soft and brittle coal seams, it is difficult, time-consuming, and costly to control gas. Once an accident occurs, the scale and harm are often more severe than those in shallow mining.

[0003] This has led to a gas control cycle of 6 months to 2 years in most mines, and even up to 10 years in some cases. This long-cycle gas control severely restricts the safe and efficient mining of coal.

[0004] To meet the requirements of high-efficiency gas drainage with pressure relief and permeability enhancement in soft and low-permeability coal seams, and to break through the technical bottleneck of "having gas but being unable to extract it" in deep coal mines, it is necessary to study the competitive penetration law of mixed gas in coal seams under low negative pressure (0.6 bar), atmospheric pressure (1 bar), and slightly high pressure (2 bar) states, develop gas high-concentration drainage sealing hole technology and equipment, save gas control costs, shorten the control cycle, improve utilization efficiency, and liberate the productivity of deep coal mines. The existing gas high-concentration drainage sealing and control technologies include cross-measure boreholes, hydraulic permeability enhancement technology, and supercritical CO2 permeability enhancement technology. However, the above technologies all have technical disadvantages.

[0005] Disadvantages of cross-measure borehole gas control: 1. Long control cycle, affecting mine succession; 2. Fast concentration attenuation, poor control effect; 3. Limited coverage of drilling control, risk of local gas accumulation and outburst; 4. High cost per ton of coal for control.

[0006] Disadvantages of hydraulic permeability enhancement technology: Prone to disordered collapse of the pressure relief space and fast attenuation of gas drainage volume;

[0007] Disadvantages of supercritical CO2 permeability enhancement technology: Injection of high-pressure and large amounts of CO2 is prone to outburst and outburst risks, high economic cost, and limited industrial-scale control. Summary of the Invention

[0008] The purpose of the present invention is to provide a gas high-concentration drainage sealing hole system and method by injecting a mixed gas, which can prevent gas leakage, reduce gas in the return air flow, eliminate the problem of gas control in the upper corner, have a simple construction method, the mixed gas is safe and hazard-free, will not cause CO2 outburst, does not affect the current mine production, is safe, economical, and efficient, and a new method solves the problem of low gas drainage concentration in low-permeability coal seams of deep mines, and increases the pre-drainage and drainage efficiency of cross-measure boreholes.

[0009] To achieve the above object, the present invention provides a gas-sealing system for high-concentration gas extraction by injecting a mixed gas, including the following modules:

[0010] Drilling module: used to drill a cross-layer borehole through the coal seam to form a gas extraction borehole;

[0011] Sealing module: used to seal the borehole with expanders at both ends;

[0012] Vacuum pumping module: used to evacuate the environment between the expanders at both ends to keep the environment in a low-vacuum state;

[0013] Gas mixing module: used to mix the mixed gas and inject it into the coal seam;

[0014] Monitoring and extraction module: used to observe the gas extraction concentration and extract the internal gas.

[0015] Preferably, the system further includes the following modules:

[0016] Anti-blocking module: used to increase the area of gas contact with the coal seam and prevent coal powder from blocking the gas injection port.

[0017] Preferably, the drilling module is connected to the sealing module, the gas mixing module, the vacuum pumping module, and the monitoring and extraction module, the sealing module is connected to the vacuum pumping module, and the monitoring and extraction module is connected to the anti-blocking module.

[0018] The present invention also provides a method for gas-sealing of high-concentration gas extraction by injecting a mixed gas, using the above-mentioned gas-sealing system for high-concentration gas extraction by injecting a mixed gas, including the following steps:

[0019] Step 1: Drill a cross-layer borehole through the coal seam to form a gas extraction borehole;

[0020] Step 2: Fill the borehole with expanders, and the expanders at both ends seal the borehole;

[0021] Step 3: Connect the gas extraction pipe to the mine gas negative pressure drainage network. When negative pressure extraction is carried out, the environment between the expanders at both ends is in a low-vacuum state;

[0022] Step 4: Lower the casing, customize the gas stone, and place the gas stone into the coal seam through the casing;

[0023] Step 5: When the gas extraction concentration decays, inject the mixed gas into the coal seam through the mixed gas injection port of the casing;

[0024] Step 6: Install a one-way valve and a gas flow concentration monitoring device at the end of the casing, observe and record the gas extraction concentration and flow rate, and repeat injecting the mixed gas according to the concentration monitoring data for continuous and efficient extraction.

[0025] Preferably, in step five, the mixed gas is a constant gas composed of N2 and CO2.

[0026] Therefore, by using the above-mentioned mixed gas injection-induced high-concentration gas drainage sealing hole system and method, the present invention has the following beneficial effects:

[0027] (1) It can prevent gas leakage, reduce the gas in the return air flow, solve the problem of gas control in the upper corner, the construction method is simple, the mixed gas is safe and non-dangerous, will not cause CO2 outburst, does not affect the current mine production, is safe, economical and efficient, and the new method solves the problem of low gas drainage concentration in deep mines with low-permeability coal seams, and increases the pre-drainage and drainage efficiency of cross-cut boreholes;

[0028] (2) Solve the practical problems of fast attenuation of borehole gas drainage concentration and high treatment cost. Under the micro-high-pressure environment, the adsorption effect of CO2 is significantly affected by the N2 component. During the period of CO2 competitive escape, CH4 no longer adsorbs during the migration process in the coal body. When the gas drainage concentration decreases, the method of injecting low-flow N2 and CO2 component gases is adopted to reconstruct the ternary gas competitive penetration mode, use N2 to promote CO2 adsorption, displace CH4 in the pores of the coal body to break through the concentration bottleneck, and then apply low pressure for slow extraction to reduce the CO2 desorption speed, so that CH4 only exists in the flow channel, changes from the adsorbed state to the free state, and realizes the improvement of gas drainage concentration.

[0029] The technical solutions of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0030] Figure 1 is a schematic structural diagram of an embodiment of a mixed gas injection-induced high-concentration gas drainage sealing hole system and method of the present invention;

[0031] Figure 2 is a schematic principle diagram of an embodiment of a mixed gas injection-induced high-concentration gas drainage sealing hole system and method of the present invention;

[0032] Figure 3 is a mixed gas penetration curve diagram of a mixed gas injection-induced high-concentration gas drainage sealing hole system and method of the present invention applied to low-permeability coking coal.

[0033] Reference Signs

[0034] 1. Borehole module; 2. Sealing module; 3. Vacuum pumping module; 4. Gas mixing module;

[0035] 5. Anti-blocking module; 6. Monitoring and drainage module. Detailed Embodiments

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning as understood by those of ordinary skill in the field to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or items appearing before this term cover the elements or items listed after this term and their equivalents, without excluding other elements or items. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0038] Embodiment 1

[0039] As Figure 1 shown, the present invention provides a gas injection-induced high-concentration gas drainage sealing hole system, including the following modules:

[0040] Drilling module 1: used to drill through-layer holes, penetrate the coal seam, and form drainage holes;

[0041] Sealing module 2: used to seal the holes through the expander at both ends;

[0042] Vacuum pumping module 3: used to evacuate the environment between the expanders at both ends to keep the environment in a low-vacuum state, change the original grouting process to a negative-pressure process, and make the original grouting position in a negative-pressure state, aiming to prevent gas from escaping, with better effects and saving grouting costs;

[0043] Gas mixing module 4: used to mix the mixed gas and inject it into the coal seam;

[0044] Monitoring and drainage module 6: used to observe the gas drainage concentration and drain the internal gas. Its tail is connected with a drainage pipeline, and the drainage pipeline can be an existing drainage system or a separately manufactured high-purity gas drainage pipeline;

[0045] Anti-blocking module 5: uses a cylindrical customized gas stone to increase the gas contact area with the coal seam and prevent coal powder from blocking the gas injection port.

[0046] The drilling module 1 is connected to the sealing module 2, the gas mixing module 4, the vacuum pumping module 3 and the monitoring and drainage module 6. The sealing module 2 is connected to the vacuum pumping module 3. The monitoring and drainage module 6 is connected to the anti-blocking module 5.

[0047] On this basis, a compatibility and adaptation module is added, which can be standardly connected to the existing gas drainage pipelines, negative pressure systems, monitoring equipment, etc. in coal mines, without the need to transform the original mine gas negative pressure drainage pipe network.

[0048] The present invention also provides a method for injecting a mixed gas to seal holes for high-concentration gas extraction. Using the above-mentioned mixed gas injection system for high-concentration gas extraction hole sealing, it includes the following steps:

[0049] Step 1: Drill a cross-cutting hole through the coal seam to form a gas extraction hole;

[0050] Step 2: Fill the inside of the hole with an expander, and the expanders at both ends seal the hole;

[0051] Step 3: Connect the gas extraction pipe to the mine gas negative pressure drainage pipe network. This step makes full use of the existing infrastructure in the mine to achieve zero-transformation connection.

[0052] Step 4: Lower the casing, customize the gas stone, and place the gas stone into the coal seam through the casing;

[0053] Step 5: When the gas extraction concentration decays, inject the mixed gas into the coal seam through the mixed gas injection port of the casing; when negative pressure extraction is carried out, the environment between the two ends of the expander is a low-vacuum environment. Among them, the mixed gas is a constant gas, composed of N2 and CO2. The role of N2 is: to promote the adsorption of CO2 and displace the CH4 adsorbed in the pores of the coal body. The role of CO2 is: to competitively adsorb CH4 and convert it from the adsorbed state to the free state.

[0054] Step 6: Install a one-way valve and a gas flow and concentration monitoring device at the end of the casing. The one-way valve is used to make the gas flow actively and unidirectionally and be discharged. The discharged gas is a mixture of high-purity gas under competitive action and a small amount of desorbed gas. The gas flow and concentration monitoring device is set up using the existing structure to observe and record the gas extraction concentration and flow rate, and repeat injecting the mixed gas according to the concentration monitoring data for continuous and efficient extraction.

[0055] When the concentration decays, inject the mixed gas again at the mixed gas injection port, and repeat the process continuously to promote extraction. With the addition of mine disturbances, it provides the driving force for the dynamic migration of gas. The instantaneous large accumulation and then ejection or outburst of gas are the sources of gas disasters in deep mines. For competitive adsorption hole sealing as shown in the figure, due to the strong adsorption of CO2 and the softening effect of N2, the gas migration only occurs at the gas flow channel level and does not involve adsorption, greatly reducing the danger. The principle is as Figure 2 shown.

[0056] Apply the above system and method to the mixed gas penetration experiment of low-permeability coking coal. Figure 3The breakthrough curves of the mixed gas depicted for a high-precision mass spectrometer, with blue for CO2, grey for CH4, and yellow for N2, and the sample being low-permeability coking coal. After the sample was penetrated by the mixed gas, a single-component CH4 with a flow rate of 7.5 mL / min was then passed through the sample. The competitive breakthrough curve showed that CO2 continuously desorbed slowly, CH4 continuously penetrated, and started competing with N2 at 90 min. As the proportion of CO2 decreased to a certain range, CH4 showed a strong competitive trend against N2.

[0057] When the coal body was affected by the competitive adsorption of the ternary mixed gas, within the range of 0 - 90 min of the continuous penetration of CH4, during the period when the flow channels formed by the mixed gas were maintained, N2 and CO2 continuously participated in competing with CH4. At this time, N2 did not lose, CO2 continuously desorbed, and CH4 stably penetrated within the flow channels created by the experiment. After 90 min, with the continuous desorption of CO2, the flow channels formed by the mixed gas were damaged, and the high-flow-rate CH4 began to compete with N2.

[0058] Therefore, the modification of the flow channels of the mixed gas can meet the penetration of high-flow-rate CH4. However, when it lasts for a certain period, with the loss of CO2, the molar fraction ratio of CH4 rises rapidly and competes strongly with N2, and then its activity decreases.

[0059] Therefore, by adopting the above-mentioned mixed gas injection-induced high-concentration gas drainage sealing hole system and method, the present invention can prevent gas from escaping, reduce the gas in the return air current, eliminate the problem of gas control in the upper corner, has a simple construction method, the mixed gas is safe and hazard-free, will not cause CO2 outburst, does not affect the current mine production, is safe, economical and efficient, and the brand-new method solves the problem of low gas drainage concentration in the deep mine low-permeability coal seams, and increases the pre-drainage and drainage efficiency of cross-cut boreholes.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A gas drainage hole sealing system for high-concentration gas extraction by injecting a mixed gas, characterized in that: It includes the following modules: Drilling module: used to drill through-layer holes, penetrate the coal seam, and form gas drainage holes; Sealing module: used to seal the holes with expanders at both ends; Vacuum pumping module: used to pump the environment between the expanders at both ends to a low-vacuum environment; Gas mixing module: used to mix the mixed gas and inject it into the coal seam; Monitoring and drainage module: used to observe the gas drainage concentration and drain the internal gas.

2. The gas drainage hole sealing system for high-concentration gas extraction by injecting a mixed gas according to claim 1, wherein: The system also includes the following module: Anti-blocking module: used to increase the area of gas contacting the coal seam and prevent coal powder from blocking the gas injection port.

3. A gas drainage hole sealing system for high-concentration gas extraction by injecting a mixed gas according to claim 1, characterized in that: The drilling module is connected to the sealing module, the gas mixing module, the vacuum pumping module, and the monitoring and drainage module. The sealing module is connected to the vacuum pumping module, and the monitoring and drainage module is connected to the anti-blocking module.

4. A method for sealing holes in high-concentration gas drainage by injecting a mixed gas, characterized in that: Adopting the gas injection and high-concentration gas drainage hole sealing system with mixed gas described in any one of claims 1-3, it includes the following steps: Step 1: Drill a through-layer hole to penetrate the coal seam and form a gas drainage hole; Step 2: Fill the hole with expanders inside the hole, and the expanders at both ends seal the hole; Step 3: Connect the gas drainage pipe to the mine gas negative pressure drainage network. When negative pressure drainage is carried out, the environment between the expanders at both ends is a low-vacuum environment; Step 4: Lower the casing, customize the gas stone, and place the gas stone into the coal seam through the casing; Step 5: When the gas drainage concentration decays, inject the mixed gas into the coal seam through the mixed gas injection port of the casing; Step 6: Install a one-way valve and a gas flow concentration monitoring device at the end of the casing, observe and record the gas drainage concentration and flow rate, and repeat injecting the mixed gas according to the concentration monitoring data for continuous and efficient drainage.

5. A method for sealing boreholes for high-concentration gas extraction by injecting a mixed gas according to claim 4, characterized in that: In Step 5, the mixed gas is a constant gas composed of N2 and CO2.

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