Gas extraction system and effect evaluation and drilling fault analysis method thereof

Abstract

The application discloses a gas extraction system and a method for effect evaluation and drilling fault analysis, and belongs to the technical field of coal mine gas extraction. The system comprises a target underground coal seam, a plurality of gas extraction collection pipes, a gas extraction main pipe, a DCS and a gas extraction pump house. One end of the gas extraction main pipe is connected with the gas extraction pump house, the other end is sealed and extends into the mining area return airway of the target underground coal seam. The plurality of gas extraction collection pipes are connected with the gas extraction main pipe through gas extraction branch pipes respectively, and detection components are arranged at the connection positions of the gas extraction collection pipes and the gas extraction branch pipes. The detection components are electrically connected with the DCS through mine signal cables. A plurality of gas extraction drilling groups and the plurality of gas extraction collection pipes are in one-to-one correspondence and are communicated in the target underground coal seam. The system can realize real-time monitoring of the target underground coal seam in all time periods and all regions, evaluate the gas extraction effect and locate the fault gas extraction drilling.

Description

Technical Field

[0001] This invention relates to a gas extraction system and its effect evaluation and borehole failure analysis method, belonging to the field of coal mine gas extraction technology. Background Technology

[0002] Coalbed methane is a clean energy source with a calorific value comparable to natural gas, and due to its abundant reserves, it has considerable application prospects. Therefore, extracting and utilizing coalbed methane can not only eliminate coalbed methane disasters but also alleviate the current energy shortage situation.

[0003] Currently, my country primarily uses pipelines laid in return airways for gas extraction. However, the poor maintenance capabilities of return airways and the complex underground conditions easily lead to pipeline damage and gas leaks. These leaks introduce oxygen into the pipelines, reducing gas purity and creating safety hazards. Furthermore, during borehole extraction, issues such as drilling failures, blockages, or collapses can occur, causing borehole failures. This prevents complete gas extraction, leaving gas residue in the coal seam and posing safety risks for subsequent mining operations. Borehole failures also result in resource waste.

[0004] Chinese patent document CN105257335A discloses a method for evaluating and controlling the gas extraction effect of surface drilling in depressurized coal seams and goaf areas. Step one: The control terminal directly obtains the drill diameter, thickness of each depressurized coal seam, and its height from the bottom of the drill hole based on drilling geological data, and acquires monitoring data through flow sensors, gas concentration sensors, and pressure sensors. A calculation model for the gas quality of surface drilling in depressurized coal seams and goaf areas is established in the control terminal, which can solve for the gas extraction concentration and flow rate in the goaf area, as well as the gas extraction flow rate of the first to i depressurized coal seams, thereby obtaining the corresponding gas extraction rate. Step two: When the gas extraction concentration in the goaf area is below 15%, the control terminal gradually adjusts the valve opening and the pump speed. This method can effectively improve the gas extraction efficiency of surface wells, while ensuring the safety of gas extraction in goaf areas, and can significantly shorten the time to achieve gas extraction standards, possessing significant application value and promising prospects for promotion.

[0005] However, this method cannot evaluate the gas extraction effect of the current coal seam in real time by region, nor can it locate the extraction borehole that has malfunctioned. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a gas extraction system and a method for evaluating its effectiveness and analyzing borehole failures.

[0007] This invention is achieved through the following technical solution:

[0008] A gas extraction system includes a target underground coal seam, multiple gas extraction and collection pipelines, a main gas extraction pipeline, a DCS (Distributed Control System), and a gas extraction pumping station. The DCS and the gas extraction pumping station are both located on the surface. One end of the main gas extraction pipeline is connected to the gas extraction pumping station, and the other end is sealed and extends into the return airway of the target underground coal seam. Multiple gas extraction and collection pipelines are located in the return airway and are connected to the main gas extraction pipeline via branch gas extraction pipelines. Each connection point between a gas extraction and collection pipeline and a branch gas extraction pipeline is equipped with a detection component. The detection component is electrically connected to the DCS via a mine signal cable. Multiple sets of gas extraction boreholes are located within the target underground coal seam and are connected to the multiple gas extraction and collection pipelines in a one-to-one correspondence.

[0009] The gas extraction combined pipeline is connected to the gas extraction branch pipeline via flanges.

[0010] The detection assembly includes a flexible flange gasket, an explosion-proof sphere, and a pre-installed cable. The explosion-proof sphere houses a methane sensor, a flow sensor, a gas pressure sensor, a carbon monoxide sensor, and a temperature sensor. The explosion-proof sphere is located at the center of the flexible flange gasket and is connected to the flexible flange gasket via a pre-installed cable and two steel wires. The pre-installed cable and the two steel wires are evenly distributed and arranged radially along the flexible flange gasket. One end of the pre-installed cable is electrically connected to all the sensors inside the explosion-proof sphere, and the other end extends to the outside of the flexible flange gasket.

[0011] The detection component is connected to the mine signal cable via a wiring mechanism; the wiring mechanism includes a main wiring component and three sub-wiring components, all of which are detachably connected to the main wiring component.

[0012] The busbar assembly includes a T-shaped body made of conductive material, with threaded holes at all three ends of the T-shaped body, and an insulating layer covering the outer surface of the T-shaped body.

[0013] The sub-wiring assembly includes a conductive section, an elastic insulator section, and a conductive connector. The conductive section has an external thread. One end of the elastic insulator section is fixedly connected to one end of the conductive section. A wire-passing hole is coaxially opened inside the elastic insulator section, and a hose clamp is fitted over the elastic insulator section. A conductive sleeve is provided inside the wire-passing hole, and one end of the conductive sleeve is fixedly connected to one end of the conductive section. A locking tooth A is provided inside the conductive sleeve, and a locking tooth B is provided on the outside of the conductive connector at a position corresponding to the locking tooth A. The conductive connector can be snapped into the conductive sleeve.

[0014] The system also includes a signal base station located in the return airway of the mining area. A wireless transceiver module A is installed at the connection between the gas extraction combined pipeline and the gas extraction branch pipeline, and the wireless transceiver module A is electrically connected to the detection component located at the connection. A wireless transceiver module B is installed on the ground and is electrically connected to the DCS.

[0015] A method for evaluating the effectiveness of a gas extraction system and analyzing borehole failures includes the following steps:

[0016] Step 1: Analyze the geological conditions of the target underground coal seam, determine the physical property parameters of the target underground coal seam and the construction parameters of the extraction borehole, establish a gas extraction numerical model using DCS multiphysics simulation software, and correct the numerical model by the gas extraction volume of the target underground coal seam.

[0017] Step 2: Treat each detection component as a monitoring point, and then start gas extraction. Each detection component will transmit the detected real-time data to the DCS.

[0018] Step 3: The DCS performs data comparison and analysis to determine the gas extraction effect and the operation status of the gas extraction boreholes at the monitoring points.

[0019] The method for judging the gas extraction effect in step three is as follows: The DCS uses multiphysics simulation software to calculate the gas desorption amount in different areas of the target underground coal seam, and then obtains the gas extraction amount in a certain area through all detection components deployed in that area. Then, the gas extraction amount in that area is compared with the gas desorption amount to judge the gas extraction effect in that area. The DCS compares the gas extraction amount and gas desorption amount in different areas in real time to monitor the gas extraction effect in the entire area of ​​the target underground coal seam.

[0020] The method for determining the operational status of the gas drainage borehole at the monitoring point in step three includes:

[0021] Compare the gas concentration-time change curve of a certain monitoring point with the correction curve. If the gas concentration decreases significantly and is accompanied by an increase in oxygen content, it indicates that there is a gas leak in the gas extraction borehole or pipeline at that monitoring point.

[0022] Compare the gas drainage flow rate-time variation curve at a certain monitoring point with the correction curve. If the gas drainage flow rate decreases significantly, it indicates that the gas drainage borehole at that monitoring point is blocked or collapsed.

[0023] The DCS classifies the gas extraction level into three levels: green, yellow, and red, based on real-time data collected from each monitoring point, as detailed below:

[0024] A. The standard for classifying green gas extraction levels is: when the gas concentration detected at the monitoring point is above 30%, the gas can be directly burned as fuel.

[0025] B. The standard for classifying yellow gas extraction levels is: the gas concentration detected at the monitoring point is between 25% and 30%, at which point the gas cannot be directly burned as fuel.

[0026] C. The standard for classifying red gas extraction levels is: when the gas concentration detected at the monitoring point is below 25%, the DCS will issue an alarm.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. It can achieve real-time monitoring of the target underground coal seam at all times and in all areas, and can evaluate the gas extraction effect and compliance status by area.

[0029] 2. It can monitor the operation of gas drainage pipelines in sections, determine whether there is a gas leak in the gas drainage borehole or pipeline, and locate the leak. It can also analyze and locate the cause of the fault in the gas drainage borehole, so that the staff can deal with it in time, improve the gas drainage effect, eliminate the hidden danger of coal seam gas, and avoid waste of resources.

[0030] 3. It can classify and extract gas according to its concentration, reduce the cost of subsequent gas treatment, and issue an alarm when the gas concentration is too low, thus realizing safe supervision of gas extraction and significantly reducing the safety risks of gas extraction. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the present invention;

[0032] Figure 2 This is a schematic diagram of the front view structure of the detection component of the present invention;

[0033] Figure 3 This is a perspective view of the detection component of the present invention;

[0034] Figure 4 This is a schematic diagram of the wiring mechanism of the present invention;

[0035] Figure 5 This is a schematic diagram of the sub-wiring assembly of the present invention;

[0036] Figure 6 This is an exploded view of the conductive sleeve and conductive connector of the present invention.

[0037] In the diagram: 1-Target underground coal seam, 2-Gas drainage borehole, 3-Gas drainage and collection pipeline, 4-Gas drainage branch pipeline, 5-Gas drainage main pipeline, 6-Signal base station, 7-Mine signal cable, 8-DCS, 9-Gas drainage pump room, 10-Flexible flange gasket, 11-Reserved cable, 12-Explosion-proof sphere, 13-Steel wire, 14-Connection mechanism, 15-Main wiring assembly, 16-Sub-wiring assembly, 17-Conductive section, 18-Elastic insulation section, 19-Conductive sleeve, 190-Clamping tooth A, 20-Conductive joint, 200-Clamping tooth B, 21-Hose clamp. Detailed Implementation

[0038] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0039] like Figures 1 to 6 As shown, the gas extraction system of the present invention includes a target underground coal seam 1, multiple gas extraction combined pipelines 3, a gas extraction main pipeline 5, a DCS8, and a gas extraction pumping station 9. The DCS8 and the gas extraction pumping station 9 are both installed on the ground. One end of the gas extraction main pipeline 5 is connected to the gas extraction pumping station 9, and the other end is sealed and extends into the return airway of the mining area of ​​the target underground coal seam 1. Multiple gas extraction combined pipelines 3 are installed in the return airway of the mining area and are respectively connected to the gas extraction main pipeline 5 through gas extraction branch pipelines 4. Detection components are installed at the connection points of each gas extraction combined pipeline 3 and gas extraction branch pipeline 4. The detection components are electrically connected to the DCS8 through a mining signal cable 7. Multiple sets of gas extraction boreholes 2 are drilled in the target underground coal seam 1 and are connected to the multiple gas extraction combined pipelines 3 in a one-to-one correspondence. During operation, a gas extraction pump is installed in the gas extraction pump room 9, and the air inlet of the gas extraction pump is connected to one end of the main gas extraction pipeline 5. After the gas extraction pump is started, the gas desorbed from the target underground coal seam 1 flows into the gas extraction pump in sequence through the gas extraction borehole 2, the gas extraction and collection pipeline 3, the gas extraction branch pipeline 4, and the main gas extraction pipeline 5, thus realizing gas extraction. During this process, the detection component transmits the real-time detected parameters such as gas concentration and gas flow rate to the DCS8 through the mine signal cable 7. The DCS8 processes, analyzes, and compares the data to evaluate the gas extraction effect, determine whether the gas extraction borehole 2 is blocked or collapsed, and locate the faulty gas extraction borehole 2.

[0040] The gas extraction combined pipeline 3 is connected to the gas extraction branch pipeline 4 by a flange.

[0041] The detection assembly includes a flexible flange gasket 10, an explosion-proof sphere 12, and a pre-installed cable 11. The explosion-proof sphere 12 houses a methane sensor, a flow sensor, a gas pressure sensor, a carbon monoxide sensor, and a temperature sensor. The explosion-proof sphere 12 is located at the center of the flexible flange gasket 10 and is connected to the flexible flange gasket 10 via a pre-installed cable 11 and two steel wires 13. The pre-installed cable 11 and the two steel wires 13 are evenly distributed and arranged radially along the flexible flange gasket 10. One end of the pre-installed cable 11 is electrically connected to all the sensors inside the explosion-proof sphere 12, and the other end extends outside the flexible flange gasket 10. During use, the explosion-proof sphere 12 is machined with multiple vent holes. The explosion-proof sphere 12 is reliably fixed at the center of the flexible flange gasket 10 by the pre-installed cable 11 and the two steel wires 13 to prevent it from swaying laterally during gas extraction when the gas flow rate or extraction negative pressure is too high.

[0042] The detection components are connected to the mining signal cable 7 via a wiring mechanism 14. The wiring mechanism 14 includes a female wiring assembly 15 and three female wiring assemblies 16, all of which are detachably connected to the female wiring assembly 15. In use, the wiring mechanism 14 meets the explosion-proof requirements for mining components. The reserved cables 11 in each detection component are conveniently and quickly connected to the mining signal cable 7 via the wiring mechanism 14, thereby achieving explosion-proof and sealed connection of the cable.

[0043] The bus terminal assembly 15 includes a T-shaped body made of conductive material, with threaded holes machined at all three ends of the T-shaped body, and the outer surface of the T-shaped body is covered with an insulating layer.

[0044] The sub-connection assembly 16 includes a conductive section 17, an elastic insulator section 18, and a conductive connector 20. The conductive section 17 has external threads. One end of the elastic insulator section 18 is fixedly connected to one end of the conductive section 17. A wire-passing hole is coaxially formed inside the elastic insulator section 18, and a hose clamp 21 is fitted over the elastic insulator section 18. A conductive sleeve 19 is installed inside the wire-passing hole, and one end of the conductive sleeve 19 is fixedly connected to one end of the conductive section 17. A locking tooth A190 is machined inside the conductive sleeve 19. A locking tooth B200 is machined on the outside of the conductive connector 20 at a position corresponding to the locking tooth A190, and the conductive connector 20 can be snapped into the conductive sleeve 19. The cable is conveniently and quickly connected to the conductive sleeve 19 via the conductive connector 20. After the conductive connector 20 and the conductive sleeve 19 are connected in place, the hose clamp 21 compresses the elastic insulator section 18 to tighten the cable, preventing loosening and poor contact after connection, thus improving the reliability of the cable connection with the connection mechanism 14.

[0045] The system also includes a signal base station 6 located in the return airway of the mining area. A wireless transceiver module A is installed at the connection between the gas extraction and collection pipeline 3 and the gas extraction branch pipeline 4, and the wireless transceiver module A is electrically connected to the detection component located at the connection. A wireless transceiver module B is installed on the ground and is electrically connected to the DCS8. After the detection component collects data, it transmits it to the DCS8 in real time via a mine signal cable 7, and simultaneously transmits it wirelessly to the DCS8 in real time via wireless transceiver module A, signal base station 6, and wireless transceiver module B, thus improving the reliability of data transmission.

[0046] A method for evaluating the effectiveness of a gas extraction system and analyzing borehole failures includes the following steps:

[0047] Step 1: Analyze the geological conditions of the target underground coal seam 1, determine its physical properties and drilling parameters, and establish a gas drainage numerical model using DCS8 multiphysics simulation software. This model is then corrected using the actual gas drainage volume of the target underground coal seam 1. The multiphysics simulation software used is COMSOL, and the established gas drainage numerical model is a coupled thermo-fluid-solid multiphysics model, which reflects the gas drainage situation under the combined effects of temperature, seepage, and stress fields during the gas drainage process.

[0048] Step 2: Treat each detection component as a monitoring point, and then start gas extraction. Each detection component will transmit the detected real-time data to DCS8.

[0049] Step 3: DCS8 performs data comparison and analysis to determine the gas extraction effect and the operation status of the gas extraction borehole 2 at the monitoring point.

[0050] The method for judging the gas extraction effect in step three is as follows: DCS8 uses multiphysics simulation software to calculate the gas desorption amount in different areas of the target underground coal seam 1, and then obtains the gas extraction amount in a certain area through all detection components deployed in that area. The gas extraction amount and the gas desorption amount in that area are then compared to determine the gas extraction effect in that area. DCS8 compares the gas extraction amount and the gas desorption amount in different areas in real time to monitor the gas extraction effect across the entire area of ​​the target underground coal seam 1. Therefore, this system can achieve real-time monitoring of the target underground coal seam 1 throughout all time periods and areas, and can evaluate the gas extraction effect and compliance status by area.

[0051] The method for determining the operational status of gas extraction borehole 2 at the monitoring point in step three includes:

[0052] Compare the gas concentration-time change curve of a certain monitoring point with the correction curve. If the gas concentration decreases significantly and is accompanied by an increase in oxygen content, it indicates that there is a gas leak in the gas extraction borehole 2 or pipeline at the monitoring point.

[0053] By comparing the gas drainage flow rate-time variation curve at a certain monitoring point with the correction curve, a significant decrease in gas drainage flow rate indicates that the gas drainage borehole 2 at that monitoring point is blocked or collapsed. Therefore, this system can monitor the operation of gas drainage pipelines in sections, determine whether gas drainage borehole 2 or the pipeline is leaking, and locate the leak. It can also analyze and locate the cause of faults in gas drainage borehole 2, facilitating timely handling by staff, improving gas drainage efficiency, eliminating coal seam gas hazards, and avoiding resource waste.

[0054] The DCS8 classifies the gas extraction level into three levels: green, yellow, and red, based on real-time data collected from each monitoring point, as detailed below:

[0055] A. The standard for classifying green gas extraction levels is: when the gas concentration detected at the monitoring point is above 30%, the gas can be directly burned as fuel.

[0056] B. The standard for classifying yellow gas extraction levels is as follows: the gas concentration detected at the monitoring point is between 25% and 30%, at which point the gas cannot be directly burned as fuel. In this case, the extracted gas meets the requirements of the "Coal Mine Safety Regulations".

[0057] C. The standard for classifying red-level gas extraction is: when the gas concentration detected at the monitoring point is below 25%, DCS8 issues an alarm. Therefore, this system can classify and extract gas based on its concentration, reducing subsequent gas treatment costs, and issuing alarms when the gas concentration is too low, thus achieving safe supervision of gas extraction and significantly reducing the safety risks associated with gas extraction.

Claims

1. A gas extraction system, characterized in that: The system includes the target underground coal seam (1), multiple gas extraction and collection pipelines (3), a main gas extraction pipeline (5), a DCS (8), and a gas extraction pumping station (9). The DCS (8) and the gas extraction pumping station (9) are both located on the ground. One end of the main gas extraction pipeline (5) is connected to the gas extraction pumping station (9), and the other end is sealed and extends into the return airway of the target underground coal seam (1). The multiple gas extraction and collection pipelines (3) The gas extraction pipeline is located in the return airway of the mining area and is connected to the main gas extraction pipeline (5) through the gas extraction branch pipeline (4). Each gas extraction pipeline (3) and the gas extraction branch pipeline (4) are equipped with a detection component. The detection component is electrically connected to the DCS (8) through the mine signal cable (7). The target underground coal seam (1) is equipped with multiple sets of gas extraction boreholes (2) and multiple gas extraction pipelines (3) connected one-to-one. The detection assembly includes a flexible flange gasket (10), an explosion-proof sphere (12), and a reserved cable (11). The explosion-proof sphere (12) is equipped with a methane sensor, a flow sensor, a gas pressure sensor, a carbon monoxide sensor, and a temperature sensor. The explosion-proof sphere (12) is located at the center of the flexible flange gasket (10) and is connected to the flexible flange gasket (10) through a reserved cable (11) and two steel wires (13). The reserved cable (11) and the two steel wires (13) are evenly distributed and arranged radially along the flexible flange gasket (10). One end of the reserved cable (11) is electrically connected to all the sensors inside the explosion-proof sphere (12), and the other end extends to the outside of the flexible flange gasket (10). The system also includes a signal base station (6) located in the return airway of the mining area. A wireless transceiver module A is provided at the connection between the gas extraction combined pipeline (3) and the gas extraction branch pipeline (4), and the wireless transceiver module A is electrically connected to the detection component located at the connection. A wireless transceiver module B is provided on the ground, and the wireless transceiver module B is electrically connected to the DCS (8).

2. The gas extraction system as described in claim 1, characterized in that: The gas extraction combined pipeline (3) is flange-connected to the gas extraction branch pipeline (4).

3. The gas extraction system as described in claim 1, characterized in that: The detection component is connected to the mine signal cable (7) via a wiring mechanism (14); the wiring mechanism (14) includes a main wiring assembly (15) and three sub-wiring assemblies (16), all of which are detachably connected to the main wiring assembly (15).

4. The gas extraction system as described in claim 3, characterized in that: The bus terminal assembly (15) includes a T-shaped body made of conductive material, with threaded holes at all three ends of the T-shaped body, and an insulating layer covering the outer surface of the T-shaped body. The sub-wiring assembly (16) includes a conductive section (17), an elastic insulator section (18), and a conductive connector (20). The conductive section (17) is provided with an external thread. One end of the elastic insulator section (18) is fixedly connected to one end of the conductive section (17). A wire hole is coaxially opened inside the elastic insulator section (18), and a hose clamp (21) is provided on the outer sleeve of the elastic insulator section (18). A conductive sleeve (19) is provided inside the wire hole, and one end of the conductive sleeve (19) is fixedly connected to one end of the conductive section (17). A locking tooth A (190) is provided inside the conductive sleeve (19), and a locking tooth B (200) is provided on the outer side of the conductive connector (20) at a position corresponding to the locking tooth A (190). The conductive connector (20) can be snapped into the conductive sleeve (19).

5. A method for evaluating the effectiveness of a gas extraction system and analyzing borehole failures as described in any one of claims 1 to 4, characterized in that: Includes the following steps: Step 1: Analyze the geological conditions of the target underground coal seam (1), determine the physical property parameters of the target underground coal seam (1) and the construction parameters of the extraction borehole, establish a gas extraction numerical model using DCS (8) multiphysics simulation software, and correct the numerical model by the gas extraction purity of the target underground coal seam (1). Step 2: Treat each detection component as a monitoring point, and then start gas extraction. Each detection component will transmit the detected real-time data to the DCS (8). Step 3: The DCS (8) performs data comparison and analysis to determine the gas extraction effect and the operation status of the gas extraction borehole (2) at the monitoring point; The method for determining the operating status of the gas extraction borehole (2) at the monitoring point in step three includes: Compare the gas concentration-time change curve of a certain monitoring point with the correction curve. If the gas concentration decreases significantly and the oxygen content increases, it indicates that there is a gas leak in the gas extraction borehole (2) or pipeline at the monitoring point. Compare the gas extraction flow rate-time variation curve of a certain monitoring point with the correction curve. If the gas extraction flow rate decreases significantly, it indicates that the gas extraction borehole (2) at the monitoring point is blocked or collapsed. The DCS (8) classifies the gas extraction level into three levels: green, yellow, and red, based on the real-time data collected from each monitoring point, as follows: A. The standard for classifying green gas extraction levels is: when the gas concentration detected at the monitoring point is above 30%, the gas can be directly burned as fuel. B. The standard for classifying yellow gas extraction levels is: the gas concentration detected at the monitoring point is between 25% and 30%, at which point the gas cannot be directly burned as fuel. C. The standard for classifying red gas extraction levels is: when the gas concentration detected at the monitoring point is below 25%, the DCS (8) issues an alarm.

6. The method for evaluating the effectiveness of a gas extraction system and analyzing borehole failures as described in claim 5, characterized in that: The method for judging the gas extraction effect in step three is as follows: DCS (8) uses multiphysics simulation software to calculate the gas desorption amount in different areas of the target underground coal seam (1), and then obtains the gas extraction amount in a certain area by all detection components arranged in a certain area. Then, the gas extraction amount in that area is compared with the gas desorption amount to judge the gas extraction effect in that area. DCS (8) compares the gas extraction amount and gas desorption amount in different areas in real time to monitor the gas extraction effect in the entire area of ​​the target underground coal seam (1).

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