A method for rapid stone door coal uncovering by cavity making and circulating hot injection

Abstract

This invention belongs to the field of coal mine safety technology, specifically relating to a method for rapid coal seam exposure through cavity creation and circulating heating. First, several boreholes are drilled ahead of the coal seam exposure face. A cavity-creating drill bit is used to create cavities in the coal section of the borehole. A extraction pipe is then inserted into the entire borehole. A mobile coal seam heating and water injection system is connected to the extraction pipe to continuously inject high-temperature hot water into the borehole. After several hours of heat exchange between the coal and water in the borehole, the mobile coal seam heating and water injection system is disconnected to drain the water. After multiple cycles of water injection and disconnection, the water in the borehole is completely drained. An extraction connector and extraction hose are then installed at the end of the extraction pipe for extraction. This invention allows for multiple uses from a single borehole: the drilled borehole is first used for cavity creation, then for circulating heating, and finally for gas extraction. By combining cavity creation and circulating heating, this invention can significantly improve the gas extraction effect, achieving enhanced extraction, rapid reduction of gas content in the coal seam exposure area, and elimination of outburst hazards.

Description

Technical Field

[0001] This invention belongs to the field of coal mine safety technology, specifically relating to a method for rapid coal uncovering in a rock face using cavity creation and circulating heating. Background Technology

[0002] Coal and gas outbursts are most likely to occur when a coal seam is exposed through a rock face. To mitigate this potential hazard, various scholars have conducted research focusing on increasing the strength of the coal and rock mass, releasing concentrated stress ahead of the working face in advance, and rapidly pre-draining coal seam gas. Measures and methods have been proposed, including grouting reinforcement, laying metal frameworks, constructing large-diameter boreholes for pressure relief, and pre-draining coal seam gas in the rock face exposure area over a long period. However, these methods face challenges such as difficulty in dispersing grouting materials within the coal seam, limited reinforcement range, restrictions on borehole diameter in outburst-prone coal seams, poor pre-drainage effect in low-permeability coal seams, and extremely long extraction times. Therefore, there is an urgent need for a rapid rock face exposure method for easily outburst-prone coal seams that can quickly and effectively eliminate the coal and gas outburst hazard in the rock face exposure area, thereby achieving the goal of safe and rapid coal face exposure.

[0003] Current research indicates a positive correlation between coal gas desorption rate and coal temperature. Higher coal temperatures result in faster gas desorption. Therefore, heating the coal seam can enhance gas desorption and improve gas extraction efficiency. Simultaneously, artificially expanding the coal seam fracture network through permeability enhancement measures can increase gas outburst channels and improve extraction efficiency. Commonly used coal heating technologies include non-contact heating methods such as infrared and microwave heating, injecting superheated water or steam into the coal seam, and injecting high-temperature inert gases. Common permeability enhancement measures include hydraulic fracturing, hydraulic slotting, hydraulic cavity creation, mechanical cavity creation, explosive blasting, and high-energy gas blasting (liquid carbon dioxide blasting, high-pressure air blasting).

[0004] Heating coal seams underground typically involves using heating cables or resistance wires. However, this method exposes these devices directly to the air or coal, posing a risk of coal ignition, gas explosions, and coal dust explosions, potentially leading to catastrophic accidents. High-temperature inert gases suffer from slow heat exchange between the gas and solid, resulting in poor thermal efficiency. Hydraulic fracturing, hydraulic cutting, explosive blasting, and high-energy gas blasting methods cause excessive disturbance to the coal seam, easily inducing outbursts; their application in coal seam exposure in rock face tunnels is restricted by relevant regulations.

[0005] Injecting superheated water or steam into the coal seam, typically at temperatures between 60 and 100°C, can prevent coal ignition and the risk of gas or coal dust explosions. Cavitation (hydraulic or mechanical) increases the deformation space of the coal seam, artificially creating a fracture network, increasing the migration channels for free gas, improving coal seam permeability, and accelerating the conversion of adsorbed gas into free gas, which is then extracted from the coal seam. Simultaneously, the cavitation parameters can be adjusted according to the gas occurrence state, increasing the pressure relief space of the coal seam while providing relatively gentle disturbance.

[0006] Based on the above background, the cavity-making and circulating heat injection technology can be applied to the coal seam exposure operation in underground coal mines. Cavities are made in the coal seam to be exposed, and then circulating heat is injected. This can release the concentrated stress in the coal body, increase the fracture network of the coal body, and accelerate the desorption of adsorbed gas in the coal body. In a short period of time, the gas content and stress of the coal seam in the coal exposure area can be reduced to a safe range, eliminating the risk of outburst, thereby achieving rapid and safe coal exposure. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for rapid coal seam exposure through cavity creation and circulating heating, which solves the problems of limited application of hydraulic fracturing, hydraulic slotting, explosive blasting, and high-energy gas blasting measures, as well as the generation of new hazards and low heating efficiency caused by high-temperature heating of the heating medium. The goal is to increase coal seam permeability, improve the degree of coal body heating and extraction, significantly reduce extraction time, improve coal seam gas extraction effect, and achieve safe coal seam exposure.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for rapid coal seam exposure through cavity creation and circulating heating, comprising the following steps:

[0009] Step 1: Drill several holes in front of the coal seam to be exposed. The holes should penetrate the bottom plate of the coal seam to be exposed and reach the set depth of the top plate of the coal seam. The holes should cover the outline of the coal exposure area to a set distance.

[0010] Step 2: Use the cavity-making drill bit to create cavities in the coal section of the borehole. After completing the cavity-making work, remove the cavity-making drill bit and drill rod.

[0011] Step 3: Run the extraction pipe into the entire borehole section. Seal the borehole opening using the "two plugs and one injection" process. The length of the sealed section should not be less than 8m.

[0012] Step 4: Continuously inject high-temperature hot water into the borehole using the mobile coal seam heating and water injection system connected to the extraction pipe. After the pressure gauge of the mobile coal seam heating and water injection system reaches the set value, stop injecting hot water and shut down the mobile coal seam heating and water injection system.

[0013] Step 5: After several hours of heat exchange between the coal and water in the borehole, disconnect the mobile coal seam heating and water injection system, drain the water in the borehole, and then repeat step 4.

[0014] Step 6: Repeat Step 5 for 2 to 3 cycles. After the cycle is complete, drain all the water from the borehole, remove the mobile coal seam heating and water injection system, and install the extraction connector and extraction hose at the end of the extraction pipe.

[0015] Step 7: Connect all the extraction hoses from the boreholes in the coal face to a single extraction connection pipe, and then connect it to the extraction pipeline laid in the roadway for extraction.

[0016] In step 1, the borehole diameter is 94 mm or more.

[0017] In step 2, the cavity-making operation adopts a continuous full-coal-section cavity-making or intermittent cavity-making process to form one or more cavity-making holes in the coal section.

[0018] In step 2, the specific implementation method of the cavity-making operation is as follows: During the cavity-making operation, a high-pressure water pump is used to provide high-pressure water, which is transmitted to the cavity-making drill bit through a high-pressure hose and drill rod. The high-pressure water cuts the coal body to form debris that flows out of the borehole with the water flow. A high-pressure water control valve is used to control whether to supply high-pressure water, and the high-pressure water pressure value is viewed through the parameter display screen on the high-pressure water pump.

[0019] In step 3, the extraction pipe is equipped with a screen on the side of the coal seam roof, and the length of the screen is 4 to 6 m. The extraction pipe in the sealed section has no screen.

[0020] In step 4, the mobile coal seam heating and water injection system includes a water injection device. The water injection device is connected in sequence to a high-temperature and high-pressure resistant hose and a circulating heat injection pipe connector. The circulating heat injection pipe connector is installed on the exposed extraction pipe end in step 3. The water injection device continuously injects high-temperature hot water into the borehole through the high-temperature and high-pressure resistant hose and the circulating heat injection pipe connector. The control valve on the high-temperature and high-pressure resistant hose is used to control whether hot water is supplied. The water injection operation stops when the water injection pressure stabilizes at the set value, as observed by the pressure gauge at the outlet of the water injection device.

[0021] In step 5, the hot water remains in the borehole for 8 hours or one work shift.

[0022] The beneficial effects of this invention are:

[0023] (1) Compared with the prior art, the present invention combines cavity creation and circulating heat injection. After cavity creation, the stress of the coal body will be redistributed, increasing the deformation space, reducing the stress of the coal body, increasing the coal body fractures, and improving the permeability of the coal seam. At the same time, circulating heat injection is carried out after cavity creation, which greatly increases the temperature of the regional coal body in a short period of time and greatly improves the gas desorption efficiency. The combination of the two can greatly improve the gas extraction effect, achieve the purpose of strengthening the extraction, rapidly reducing the gas content in the coal exposure area, and eliminating the risk of outburst.

[0024] (2) High-temperature water is used as the heating medium. The heat transfer efficiency of water to coal is higher than that of gas to coal, which improves the efficiency of heat exchange and solves the shortcomings of traditional heating measures such as infrared and microwave heating, such as fast heat decay and high energy consumption. At the same time, using water as the heating medium can prevent the coal in the borehole from igniting or exploding under the action of other high-temperature heat sources.

[0025] (3) One hole can be used for multiple purposes. The borehole is first used for creating a cavity, then for circulating heat injection, and finally for gas extraction. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the extraction system connection for a rapid coal seam uncovering method using cavity creation and circulating heating according to the present invention.

[0027] Figure 2 A schematic diagram showing the connection between the cavity-creating device and the borehole;

[0028] Figure 3 This is a schematic diagram showing the connection between the heating device and the borehole;

[0029] Attached reference numerals: 1. Coal seam to be exposed; 2. Coal seam roof; 3. Coal seam floor; 4. Coal exposure face; 5. Borehole; 6. Cavity; 7. Sealing section; 8. Extraction hose; 9. Extraction connection pipe; 10. Rock roadway; 11. Extraction pipeline; 12. Drilling rig; 13. Drill rod; 14. High-pressure hose; 15. High-pressure water pump; 16. High-pressure water control valve; 17. Parameter display screen; 18. Cavity drill bit; 19. Extraction pipe; 20. Circulating heat injection pipe connector; 21. High-temperature and high-pressure resistant hose; 22. Control valve; 23. Water injection device; 24. Pressure gauge. Detailed Implementation

[0030] To better explain and facilitate understanding of the present invention, the technical solutions and effects of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0031] like Figures 1-3 As shown, a method for rapid coal seam exposure via cavity creation and circulating heating includes the following steps:

[0032] Step 1: When the normal distance between the coal face 4 of the rock roadway 10 and the coal seam 1 to be exposed reaches the requirements of relevant regulations such as the "Detailed Rules for the Prevention and Control of Coal and Gas Outbursts", local anti-outburst measures shall be taken. Several boreholes 5 shall be drilled in front of the coal face 4 using drilling rig 12. The boreholes 5 shall penetrate the bottom plate 3 of the coal seam 1 to reach the set depth of the top plate 2 of the coal seam. The boreholes 5 shall cover the outer edge of the coal exposure area to the set distance. The diameter of the boreholes 5 shall be 94mm or more. In this case, the diameter of the boreholes 5 is 120mm. The coverage area of ​​the boreholes 5 shall meet the requirements of relevant regulations such as the "Detailed Rules for the Prevention and Control of Coal and Gas Outbursts". The spacing of the boreholes 5 can be arranged according to the effective radius of the cavitation borehole extraction as determined by the actual investigation of the coal mine.

[0033] Step 2: Using the cavity-making drill bit 18, perform conventional cavity-making operations on the coal section of borehole 5. Continuous full-coal-section cavity-making or intermittent cavity-making processes can be used to form one or more cavity-making holes 6 in the coal section. The cavity-making type can be determined based on the actual situation of each application scenario. Currently, hydraulic and mechanical cavity-making equipment and processes are relatively mature in the market. This case uses hydraulic cavity-making. The specific method is as follows: During cavity-making operations, a high-pressure water pump 15 provides high-pressure water, which is transmitted to the cavity-making drill bit 18 through the high-pressure hose 14 and drill rod 13. Water cuts the coal body, forming debris that flows out of borehole 5 with the water flow. Cavity creation is generally completed from the bottom to the opening of the borehole. A high-pressure water control valve 16 is used to control the supply of high-pressure water, and the high-pressure water pressure value is viewed on the parameter display screen 17 on the high-pressure water pump 15. Cavity creation parameters can be determined according to the actual situation of each application scenario and there are no uniform requirements. In this case, intermittent cavitation is used, creating cavities in the coal section from the bottom to the opening. The high-pressure water pressure is 15-20 MPa, the spacing between cavitation sections is 4 m, the cavitation length is 1 m, and the coal output from the cavitation is 1 m³. 3 After completing the single-hole cavity-making operation according to the designed operation plan, remove the cavity-making drill bit 18 and drill rod 13. The specific cavity-making operation plan must be approved by the technical supervisor before implementation.

[0034] Step 3: Insert a conventional extraction pipe 19 into the entire borehole section of borehole 5. The borehole opening of borehole 5 is sealed using a "two-plug-one-injection" process. The length of the sealed section 7 is not less than 8m. The extraction pipe 19 is equipped with screens on the side of the coal seam roof 2, with a screen length of 4-6m. The extraction pipe 19 in the sealed section 7 has no screens. The purpose of using extraction pipes 19 with long screens is to prevent the collapsed coal slag in the borehole from clogging part of the screens of the extraction pipe 19 after subsequent water injection in borehole 5, thus affecting the extraction effect.

[0035] Step 4: Using the mobile coal seam heating and water injection system, continuously inject high-temperature hot water into the borehole 5 through the extraction pipe 19. After the pressure gauge 24 of the mobile coal seam heating and water injection system reaches the set value, stop injecting hot water. The mobile coal seam heating and water injection system includes a water injection device 23, which is connected in sequence to a high-temperature and high-pressure resistant hose 21 and a circulating heat injection pipe connector 20. The circulating heat injection pipe connector 20 is installed on the exposed end of the extraction pipe 19 in Step 3. The water injection device 23 continuously injects high-temperature hot water into the borehole 5 through the high-temperature and high-pressure resistant hose 21 and the circulating heat injection pipe connector 20. The control valve 22 on the high-temperature and high-pressure resistant hose 21 is used to control whether hot water is supplied. When the water injection pressure stabilizes at the set value, stop the heat injection operation and shut off the water injection device 23 of the mobile coal seam heating and water injection system.

[0036] The water injection temperature can be determined by testing; in this case, 80℃ is selected. The stable value of the water injection pressure can be selected according to the actual situation; in this case, 10MPa is used.

[0037] Step 5: After several hours of heat exchange between coal and water in borehole 5, the hot water will remain in borehole 5 for 8 hours or one work shift; disconnect the circulating heating pipe connection 20 of the mobile coal seam heating and water injection system to drain the water in borehole 5. When draining the water in borehole 5, if borehole 5 is a downward hole, a pumping device is needed to pump out the water in borehole 5, and then repeat step 4.

[0038] Step 6: Repeat Step 5 for 2 to 3 cycles. The number of cycles should be selected according to the coal body temperature rise. Generally, 2 to 3 cycles are sufficient. After the end, drain the water in the borehole 5 completely, remove the circulating heating pipe connector 20 of the mobile coal seam heating and water injection system from the end of the extraction pipe 19, and install the extraction connector and extraction hose 8.

[0039] Step 7: Collect the extraction hoses 8 from all the boreholes in the coal face 4 into a single extraction connection pipe 9, and then connect it to the extraction pipeline 11 laid in the rock roadway 10 for extraction.

[0040] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, are covered within the scope of protection of the present invention.

Claims

1. A method for rapid coal seam exposure via cavity creation and circulating heating, characterized in that, Includes the following steps: Step 1: Drill several holes in front of the coal seam to be exposed. The holes should penetrate the bottom plate of the coal seam to be exposed and reach the set depth of the top plate of the coal seam. The holes should cover the outline of the coal exposure area to a set distance. Step 2: Use a cavity-making drill bit to create cavities in the coal section of the borehole. After completing the cavity-making work, remove the cavity-making drill bit and drill rod. Use intermittent cavity-making, creating cavities in the coal section from the bottom of the hole to the opening. The high-pressure water pressure is 15-20 MPa, the cavity-making interval is 4m, the cavity length is 1m, and the coal output from the cavity is 1m³. Step 3: Run the extraction pipe through the entire borehole. The borehole opening is sealed using the "two plugs and one injection" process. The length of the sealed section is not less than 8m. The extraction pipe is equipped with a screen on the side of the coal seam roof. The length of the screen is 4 to 6m. The extraction pipe in the sealed section has no screen. Step 4: Continuously inject high-temperature hot water into the borehole using the mobile coal seam heating and water injection system connected to the extraction pipe. After the pressure gauge of the mobile coal seam heating and water injection system reaches the set value, stop injecting hot water and shut down the mobile coal seam heating and water injection system. Step 5: After several hours of heat exchange between the coal and water in the borehole, disconnect the mobile coal seam heating and water injection system, drain the water in the borehole, and then repeat step 4. Step 6: Repeat Step 5 for 2-3 cycles. After the cycle is complete, drain all the water from the borehole, remove the mobile coal seam heating and water injection system, and install the extraction connector and extraction hose at the end of the extraction pipe. Step 7: Connect all the extraction hoses from the boreholes in the coal face to a single extraction connection pipe, and then connect it to the extraction pipeline laid in the roadway for extraction.

2. The method for rapid coal seam exposure via cavity creation and circulating heating according to claim 1, characterized in that, In step 1, the borehole diameter is 94 mm or more.

3. The method for rapid coal seam exposure via cavity creation and circulating heating according to claim 1, characterized in that, In step 2, the specific implementation method of the cavity-making operation is as follows: During the cavity-making operation, a high-pressure water pump is used to provide high-pressure water, which is transmitted to the cavity-making drill bit through a high-pressure hose and drill rod. The high-pressure water cuts the coal body to form debris that flows out of the borehole with the water flow. A high-pressure water control valve is used to control whether to supply high-pressure water, and the high-pressure water pressure value is viewed through the parameter display screen on the high-pressure water pump.

4. The method for rapid coal seam exposure via cavity creation and circulating heating according to claim 1, characterized in that, In step 4, the mobile coal seam heating and water injection system includes a water injection device. The water injection device is connected in sequence to a high-temperature and high-pressure resistant hose and a circulating heat injection pipe connector. The circulating heat injection pipe connector is installed on the exposed extraction pipe end in step 3. The water injection device continuously injects high-temperature hot water into the borehole through the high-temperature and high-pressure resistant hose and the circulating heat injection pipe connector. The control valve on the high-temperature and high-pressure resistant hose is used to control whether hot water is supplied. The water injection operation stops when the water injection pressure stabilizes at the set value, as observed by the pressure gauge at the outlet of the water injection device.

5. The method for rapid coal seam exposure via cavity creation and circulating heating according to claim 1, characterized in that, In step 5, the hot water remains in the borehole for 8 hours or one work shift.

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