Rapid rock cross-cut coal uncovering method through cave forming and circulating heat injection

Abstract

The invention belongs to the technical field of coal mine safety, and particularly relates to a cave-making and circulating heat injection rapid cross-cut coal uncovering method, which comprises the following steps of: firstly, constructing a plurality of drill holes in front of a coal uncovering working surface, performing cave-making operation on coal sections of the drill holes by utilizing a cave-making drill bit, and putting extraction pipes into the whole hole sections in the drill holes; a movable coal seam heating and water injection system is connected with an extraction pipe to continuously inject high-temperature hot water into a drill hole, after heat exchange of coal and water in the drill hole for several hours, the movable coal seam heating and water injection system is disconnected, water in the drill hole is discharged, and the water in the drill hole is thoroughly discharged after repeated water injection and disconnection circulation. According to the method, multiple purposes are achieved through one hole, the drilled hole for construction is firstly used for hole forming, then is used for circulating heat injection and finally is used for gas extraction, hole forming and circulating heat injection are combined, the gas extraction effect can be greatly improved, the gas extraction efficiency is improved, and the method has the advantages that the construction cost is reduced, and the construction period is shortened. The purposes of enhancing extraction promotion, rapidly reducing the gas content in the coal uncovering area and eliminating outburst danger are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine safety, and in particular relates to a method for rapid stone gate coal uncovering by hole making and circulating heat injection. Background Art

[0002] When the coal seam is exposed by the stone gate, the danger of coal and gas outburst is most likely to occur. In order to control the potential danger of coal and gas outburst in the stone gate coal exposure, different scholars have conducted research from the aspects of increasing the strength of coal rock mass, releasing the concentrated stress in front of the working face in advance, and quickly pre-extracting coal seam gas. Measures and methods such as grouting reinforcement, laying metal skeletons, constructing large-diameter drilling holes to relieve pressure, and pre-extracting coal seam gas in the stone gate coal exposure area for a long time in advance have been proposed. However, there are problems such as the difficulty of grouting materials to diffuse in the coal body, limited reinforcement range, limited diameter of the measures in the protruding coal seam, poor pre-extraction effect in the low-permeability coal seam, and extremely long extraction time. Therefore, it is urgent to provide a rapid stone gate coal exposure method for coal seams that are prone to outburst, which can quickly and effectively eliminate the danger of coal and gas outburst in the stone gate coal exposure area, so as to achieve the goal of safe and rapid coal exposure.

[0003] At present, relevant research results show that the gas desorption rate of coal is positively correlated with the coal temperature. The higher the coal temperature, the faster its gas desorption capacity. Therefore, the coal can be heated to enhance coal gas desorption and improve the gas extraction effect. At the same time, taking permeability enhancement measures to artificially expand the coal fracture network can also increase the gas outflow channel in the coal seam and improve the gas extraction effect. Commonly used coal heating technologies mostly use non-contact heating methods such as infrared and microwaves, methods of injecting superheated water or water vapor into coal seams, and methods of injecting high-temperature inert gases. Commonly used permeability enhancement measures include hydraulic fracturing, hydraulic slitting, hydraulic cavitation, mechanical cavitation, explosive blasting, high-energy gas blasting (liquid carbon dioxide blasting, high-pressure air blasting), etc.

[0004] Heating cables, resistance wires, etc. are generally used to heat the coal medium underground. However, this method directly exposes the heating cables, resistance wires, etc. to the air or coal, which not only poses the risk of coal fire, but also poses the risk of inducing gas explosions and coal dust explosions, which can easily lead to serious accidents. Injecting high-temperature inert gas results in slow exchange of heat energy between gas and solid, and poor thermal efficiency. Hydraulic fracturing, hydraulic slitting, explosive blasting, and high-energy gas blasting are too drastic disturbances to the coal body, which can easily induce outbursts. Their application in stone gate coal mining is restricted by relevant regulations.

[0005] In the method of injecting superheated water or water vapor into the coal seam, the injection temperature is usually 60-100℃, which can avoid the danger of coal ignition and inducing gas explosion and coal dust explosion. Cave making (hydraulic cave making or mechanical cave making) can increase the deformation space of the coal body, artificially create a coal body fracture network, increase the free gas migration channel, improve the permeability of the coal seam, accelerate the conversion of adsorbed gas into free gas, and be extracted from the coal body. At the same time, the cave making parameters can be changed at any time according to the gas storage state, which can not only increase the coal body pressure relief space, but also disturb the coal body relatively gently.

[0006] Based on the above background, the hole making and cyclic heat injection technology can be applied to the coal mining operation in the stone gate underground coal mine. The hole making and cyclic heat injection can not only release the concentrated stress of the coal body and increase the coal body fracture network, but also accelerate the desorption of adsorbed gas in the coal body. In a relatively short time, the coal seam gas content and coal body stress in the coal mining area can be reduced to a safe range, eliminating the danger of coal outburst, thereby achieving rapid and safe coal mining. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a method for rapid stone gate coal uncovering by hole making and circulating heat injection, which solves the problems of limited application of hydraulic fracturing, hydraulic cutting, explosive blasting, and high-energy gas blasting, and the generation of new danger sources and low heating efficiency due to high-temperature heating of the heat injection medium, so as to increase the permeability of the coal seam, improve the degree of extraction promoted by heat injection in the coal body, significantly reduce the extraction time, improve the coal seam gas extraction effect, and achieve safe coal uncovering.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solution: a method for rapid stone gate coal uncovering by hole making and cyclic heat injection, comprising the following steps:

[0009] Step 1: Construct several boreholes in front of the coal mining face. The boreholes should penetrate the coal seam floor to reach the set depth of the coal seam roof. The boreholes should cover the outside of the coal mining area contour line to the set distance.

[0010] Step 2: Use the hole-making drill bit to make a hole in the coal section of the borehole. After the hole-making work is completed, withdraw the hole-making drill bit and the drill rod;

[0011] Step 3: Run the extraction pipe into the entire borehole, and seal the borehole using the "two plugging and one injection" process. The length of the sealing section should be no less than 8m.

[0012] Step 4: Use the mobile coal seam heating and water injection system to connect the extraction pipe to continuously inject high-temperature hot water into the borehole. When 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 completion, completely drain the water in the borehole, remove the mobile coal seam heating and water injection system, and install the extraction joint and extraction hose at the end of the extraction pipe;

[0015] Step 7: Gather the extraction hoses of all the boreholes in the coal mining operation face into an extraction connecting pipe, and then connect them to the extraction pipeline laid in the tunnel for extraction.

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

[0017] In step 2, the cavitation operation adopts a continuous whole-coal section cavitation or an interval cavitation process to form one or more cavitation holes in the coal section.

[0018] In step 2, the specific implementation method of the hole making operation is as follows: during the hole making operation, a high-pressure water pump is used to provide high-pressure water, which is transmitted to the hole making drill bit through a high-pressure hose and a 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 on the parameter display screen on the high-pressure water pump.

[0019] In step 3, the extraction pipe is provided with a sieve hole on the coal seam roof side, the length of the sieve hole is 4 to 6 m, and the extraction pipe in the sealing section has no sieve hole.

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

[0023] (1) Compared with the prior art, the present invention combines cavitation with cyclic heat injection. After cavitation, the stress of the coal body will be redistributed, which will increase the deformation space, reduce the stress of the coal body, increase the cracks in the coal body, and improve the permeability of the coal seam. At the same time, cyclic heat injection is carried out after cavitation, which can greatly increase the regional coal body temperature in a short period of time and greatly improve the gas desorption efficiency. The combination of the two can greatly improve the gas extraction effect, achieve the purpose of strengthening extraction promotion, quickly reducing the gas content in the coal uncovering area, and eliminating the danger of coal outburst.

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

[0025] (3) One hole can be used for multiple purposes. The drilled hole is first used for cave construction, then for circulating heat injection, and finally for gas extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the connection of the extraction system of a method for rapid rock-gate coal uncovering by cave-making and cyclic heat injection according to the present invention;

[0027] Figure 2 It is a schematic diagram of the connection between the hole making device and the drilling hole;

[0028] Figure 3 It is a schematic diagram of the connection between the heat injection device and the drill hole;

[0029] Figure numerals: 1. Coal seam to be uncovered; 2. Coal seam roof; 3. Coal seam floor; 4. Coal uncovering working face; 5. Drill hole; 6. Hole for making holes; 7. Sealing section; 8. Extraction hose; 9. Extraction connecting pipe; 10. Rock tunnel; 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. Hole-making drill bit; 19. Extraction pipe; 20. Pipe connector for circulating heat injection; 21. High-temperature and high-pressure hose resistant to high temperature; 22. Control valve; 23. Water injection device; 24. Pressure gauge. DETAILED DESCRIPTION

[0030] In order to better explain the present invention and facilitate understanding, the technical scheme and effects of the present invention are described in detail below through specific implementation methods in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0031] like Figures 1 to 3 As shown, a method for rapid stone gate coal uncovering by hole making and circulating heat injection comprises the following steps:

[0032] Step 1: When the normal distance between the coal-excavating working face 4 of the rock tunnel 10 and the coal seam 1 to be exposed reaches the requirements of the "Detailed Rules for Preventing and Controlling Coal and Gas Outbursts" and other relevant regulations, local anti-outburst measures are taken, and a number of boreholes 5 are constructed in front of the coal-excavating working face 4 using a drilling rig 12. The boreholes 5 should penetrate the coal seam floor 3 of the coal seam 1 to be exposed to reach the set depth of the coal seam roof 2, and the boreholes 5 need to cover the outside of the coal-excavating area contour line to the set distance; the diameter of the boreholes 5 is 94 mm or more. In this case, the diameter of the boreholes 5 is 120 mm. The coverage of the boreholes 5 needs to meet the requirements of the "Detailed Rules for Preventing and Controlling Coal and Gas Outbursts" and other relevant regulations. The spacing between the boreholes 5 can be arranged according to the effective radius of the hole-making drilling extraction actually investigated in the coal mine;

[0033] Step 2: Use the cavitation drill 18 to perform conventional cavitation operations on the coal section of the borehole 5. Continuous cavitation of the entire coal section or interval cavitation process can be used to form one or more cavitation holes 6 in the coal section; the cavitation type can be determined according to the actual situation of each application scenario. At present, the hydraulic cavitation and mechanical cavitation equipment and processes in the market are relatively mature. This case uses hydraulic cavitation. The specific working method is: during the cavitation operation, a high-pressure water pump 15 is used to provide high-pressure water, which is transmitted to the cavitation drill 18 through a high-pressure hose 14 and a drill rod 13. The high pressure water is then pumped to the cavitation drill 18, and the high pressure water is then pumped to the cavitation drill 18. Water cuts the coal body to form debris that flows out of the borehole 5 with the water flow. Generally, the hole making work is completed from the bottom of the hole to the hole mouth. The high-pressure water control valve 16 is used to control whether to supply high-pressure water. The high-pressure water pressure value is viewed through the parameter display screen 17 on the high-pressure water pump 15. The hole making parameters can be determined according to the actual situation of each application scenario, and there is no unified requirement. This case adopts interval hole making, and holes are made in the coal section from the bottom of the hole to the hole mouth. The high-pressure water pressure is 15-20MPa, the hole making section spacing is 4m, the hole making length is 1m, and the hole making coal output is 1m 3 After completing the single-hole cavitation operation according to the designed operation plan, withdraw the cavitation drill bit 18 and the drill rod 13. The specific cavitation operation plan must be approved by the technical person in charge before implementation;

[0034] Step 3: insert a common extraction pipe 19 into the entire borehole section of the borehole 5, and seal the borehole 5 with a "two blocking and one injection" process. The length of the sealing section 7 is not less than 8m. The extraction pipe 19 is located on the side of the coal seam roof 2 and is provided with a screen hole. The length of the screen hole is 4 to 6m. The extraction pipe 19 of the sealing section 7 has no screen hole. The purpose of using the extraction pipe 19 with a long-distance screen hole is to prevent the coal slag collapsed in the hole from blocking part of the screen holes of the extraction pipe 19 after the subsequent water injection of the borehole 5, thereby affecting the extraction effect.

[0035] Step 4: Use the mobile coal seam heating and water injection system to connect the extraction pipe 19 to continuously inject high-temperature hot water into the borehole 5. 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. The water injection device 23 is connected to the high-temperature and high-pressure hose 21 and the circulating heat injection pipe connector 20 in sequence. The circulating heat injection pipe connector 20 is installed on the end of the extraction pipe 19 exposed 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 hose 21 and the circulating heat injection pipe connector 20. The control valve 22 on the high-temperature and high-pressure hose 21 is used to control whether hot water is supplied. When the water injection pressure is stabilized at the set value through the pressure gauge 24 at the water outlet end of the water injection device 23, the heat injection operation is stopped, and the water injection device 23 of the mobile coal seam heating and water injection system is closed;

[0036] The water injection temperature can be determined by experiment. In this case, 80℃ is selected. The stable value of 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 the coal and water in the borehole 5, the hot water is retained in the borehole 5 for 8 hours or one work shift; disconnect the circulating heat injection pipe connector 20 of the mobile coal seam heating and water injection system to drain the water in the borehole 5. When draining the water in the borehole 5, if the borehole 5 is a downward hole, it is necessary to use a pumping device to pump out the accumulated water in the borehole 5, and then repeat step 4;

[0038] Step 6: Repeat step 5 for 2 to 3 cycles. The number of cycles is selected according to the temperature rise of the coal body. Generally, 2 to 3 cycles are sufficient. After the end, the water in the borehole 5 is completely drained, and the circulating heat injection pipe connector 20 of the mobile coal seam heating and water injection system at the end of the extraction pipe 19 is removed, and the extraction joint and the extraction hose 8 are installed;

[0039] Step 7: Collect the extraction hoses 8 of all the boreholes in the coal mining face 4 into an extraction connecting pipe 9, and then connect them to the extraction pipeline 11 laid in the rock tunnel 10 for extraction.

[0040] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which are all covered by the protection scope of the present invention.

Claims

1. A method for rapid coal mining by hole making and circulating heat injection, characterized in that: The following steps are involved: Step 1: Construct several boreholes in front of the coal mining face. The boreholes should penetrate the coal seam floor to reach the set depth of the coal seam roof. The boreholes should cover the outside of the coal mining area contour line to the set distance. Step 2: Use the hole-making drill bit to make a hole in the coal section of the borehole. After the hole-making work is completed, withdraw the hole-making drill bit and the drill rod; Step 3: Run the extraction pipe into the entire borehole, and seal the borehole using the "two plugging and one injection" process. The length of the sealing section should be no less than 8m. Step 4: Use the mobile coal seam heating and water injection system to connect the extraction pipe to continuously inject high-temperature hot water into the borehole. When 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 hole, disconnect the mobile coal seam heating and water injection system, drain the water in the hole, and then repeat step 4; Step 6: Repeat step 5 for 2 to 3 cycles. After the completion, completely drain the water in the borehole, remove the mobile coal seam heating and water injection system, and install the extraction joint and extraction hose at the end of the extraction pipe; Step 7: Gather the extraction hoses of all the boreholes in the coal mining operation face into an extraction connecting pipe, and then connect them to the extraction pipeline laid in the tunnel for extraction.

2. A method for rapid coal mining by hole making and cyclic heat injection according to claim 1, characterized in that: In step 1, the drilling diameter is 94 mm or more.

3. A method for rapid coal mining by hole making and cyclic heat injection according to claim 1, characterized in that: In step 2, the cavitation operation adopts a continuous whole-coal section cavitation or an interval cavitation process to form one or more cavitation holes in the coal section.

4. A method for rapid coal mining by hole making and cyclic heat injection according to claim 1, characterized in that: In step 2, the specific implementation method of the hole making operation is as follows: during the hole making operation, a high-pressure water pump is used to provide high-pressure water, which is transmitted to the hole making drill bit through a high-pressure hose and a 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 on the parameter display screen on the high-pressure water pump.

5. A method for rapid rock-cutting coal mining by hole-making and cyclic heat injection according to claim 1, characterized in that: In step 3, the extraction pipe is provided with a sieve hole on the coal seam roof side, the length of the sieve hole is 4 to 6 m, and the extraction pipe in the sealing section has no sieve hole.

6. A method for rapid coal mining by hole making and cyclic heat injection according to claim 1, characterized in that: In step 4, the mobile coal seam heating and water injection system includes a water injection device, which is connected to a high-temperature and high-pressure hose and a circulating heat injection pipe connector in sequence. The circulating heat injection pipe connector is installed on the end of the extraction pipe exposed in step 3. The water injection device continuously injects high-temperature hot water into the borehole through the high-temperature and high-pressure hose and the circulating heat injection pipe connector, and uses the control valve on the high-temperature and high-pressure hose to control whether hot water is supplied. The heat injection operation is stopped when the water injection pressure is stabilized at the set value as shown by the pressure gauge at the water outlet end of the water injection device.

7. A method for rapid coal mining by hole making and cyclic heat injection 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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