Deep in-situ resource composite fluidization mining method

Abstract

The invention discloses a deep in-situ resource composite fluidization mining method. The method comprises deep in-situ resource liquefaction mining, deep in-situ resource gasification mining and deep in-situ resource reinforcement and degradation. Wherein deep in-situ resource liquefaction exploitation is realized through combination of well group hydraulic fracturing and organic solvent dissolution; in the deep in-situ resource gasification mining, the residual solid coal resources after liquefaction are gasified and combusted, and heat extraction is achieved through heat exchange; in the deep in-situ resource reinforcement and degradation process, during filling reinforcement, residual coal resources are continuously utilized through the degradation effect of microorganisms; integrated mining is formed through mutual cooperation of liquefaction, gasification and microbial degradation of deep in-situ resources, the utilization efficiency of deep in-situ resource conversion is greatly improved, the resource recovery rate is remarkably improved, underground residual chemical reagents are treated, the problem of environmental pollution is effectively relieved, and the method is suitable for industrial production. And a technical support is provided for the development of a deep in-situ resource fluidization mining theory.

Description

Technical Field

[0001] The invention relates to the field of underground resource exploitation, and in particular to a deep in-situ resource composite fluidized exploitation method. Background Art

[0002] Due to the abundance of coal resources, coal resources are still one of the main energy sources in my country at present and in the future, but nearly 70% are distributed at a depth of more than 2,000 meters. With the gradual depletion of shallow resources in traditional coal mining bases, a large number of mines are facing the risk of elimination and closure. It has become an inevitable trend to advance into the deep earth and mine deep resources. The increase in mining depth has brought about safety, environmental, and technical problems, prompting deep mining of coal resources to enter a stage of transformation and upgrading. In this regard, some industry experts have proposed a mining technology system that can convert deep coal resources into liquid, gaseous, or solid-liquid-gas mixtures in situ, and realize unmanned intelligent mining, selection, filling, and thermal and electrical conversion underground, which is called fluidized mining theory. The in-situ conversion of deep coal resources can be achieved through a series of chemical reactions, including liquefaction and dissolution of chemical reagents, high-temperature combustion and gasification, and microbial degradation.

[0003] Although the deep in-situ fluidized mining theory has changed the traditional practice of "converting energy from the well" of solid resources, and theoretically solved a series of problems such as ecological and environmental pollution in the mining industry, poor safety, and ground transportation losses, the actual application and utilization efficiency of in-situ conversion of coal resources still need to be improved. First, the liquefaction and dissolution of coal seams require organic solvents. When the contact area between the coal seams and the solvent is small, the liquefaction efficiency will be low, and the injection amount of organic solvents must be increased. Excessive injection of organic solvents not only increases the liquefaction cost, but also the excess organic solvents will remain in the coal seam fracture network. When the coal seam is liquefied, these residual organic solvents will flow along the fractures and cause pollution hazards to groundwater resources. Secondly, when underground coal gasification is used, due to the low oxygen content in the deep underground, chemical combustion aids need to be injected to ensure sufficient combustion in order to maintain a continuous combustion reaction underground. If these chemical combustion aids remain, they will also cause underground environmental pollution problems and increase mining costs. Finally, the mining methods currently in use cannot guarantee complete mining of resources within the coal mining area. After large-scale coal mining is completed, if the remaining small amount of coal is mined using the existing mining methods, it will be eliminated and become abandoned mines due to the difficulty and high mining cost, making it impossible to fully utilize the resources of each mined coal mine.

[0004] In summary, how to provide a method to achieve full utilization of coal resources at a lower mining cost and effectively reduce the impact on the environment is the technical problem required by the present invention. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a deep in-situ resource composite fluidized mining method, which can fully utilize coal resources at a lower mining cost and effectively reduce the impact on the environment.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a deep in-situ resource composite fluidized mining method, the specific steps are: Step 1: Deep in-situ resource liquefaction mining: first lay out the well group, then carry out hydraulic fracturing construction, and finally carry out in-situ coal liquefaction extraction to obtain a coal slurry solid-liquid mixture and form a methane-air mixture in the well group.

[0007] Step 2: Deep in-situ resource gasification and exploitation: first lay out the heat exchange pipes, then gasify and burn the methane-air mixture in-situ, and finally extract and utilize the combustion heat through the continuous flow of water in the heat exchange pipes.

[0008] Step 3: Deep in-situ resource reinforcement and degradation: First, fill and reinforce the deep coal seam, and use microorganisms to degrade the residual coal body and extract methane gas. After completion, repeat steps one to three according to the distribution of the remaining coal seams, and carry out composite fluidized mining on the next target coal seam.

[0009] Further, the step 1 is specifically as follows: 1.1. Layout of well groups: First, construct at least two vertical wells from the ground to the target coal seam, and the wellheads of each vertical well are on the same straight line on the ground; the deepest parts of adjacent vertical wells are connected by constructing horizontal wells to complete the layout of the well group.

[0010] 1.2. Hydraulic fracturing construction: Use a perforating gun to perforate the surrounding coal body at intervals in the horizontal well, and then inject fracturing fluid containing potassium permanganate from each vertical well into the horizontal well for hydraulic fracturing, so that a fracture network is formed in the surrounding coal body, achieving the initial fracturing of the coal seam, and then promoting the desorption of coal seam gas and escaping from the fractures into the horizontal well to form a methane-air mixture.

[0011] 1.3. In-situ liquefaction of coal: Inject organic solvents from each vertical well into the horizontal well. The organic solvents enter the fracture network formed in step 1.2 to impact the coal body, increasing the contact area between the organic solvent and the coal body. After the injection is completed, the organic solvent is allowed to stand for a period of time. With the help of the high temperature conditions underground, the organic solvent and the coal seam are thermally dissolved and liquefied to form a coal slurry solid-liquid mixture. Finally, the coal slurry solid-liquid mixture is pumped out using a surface pump. At this time, the fractures are further expanded to achieve secondary fracturing and accelerate the desorption of the remaining coal seam gas to the horizontal well.

[0012] Furthermore, the fracturing fluid containing potassium permanganate in step 1.2 is formed by mixing potassium permanganate particles with conventional fracturing fluid, and the concentration of potassium permanganate in the conventional fracturing fluid after mixing is 20%.

[0013] Furthermore, during the hydraulic fracturing construction in step 1.2, the injection volume of the fracturing fluid containing potassium permanganate is controlled at 1.0-5.0 m 3 / min, and is adjusted within this range according to the permeability and porosity of the coal seam to ensure the generation of the fracture network and the subsequent decomposition and release of sufficient oxygen; the injection pressure is controlled within the range of 10~60MPa, and is adjusted within this range according to the coal seam fracture pressure and the stable expansion pressure of the fracture to ensure that the fluid pressure around the horizontal well is higher than the fracture pressure of the coal seam and lower than the fracture pressure of the adjacent rock formation, so that the fracture network is only generated in the coal seam.

[0014] Furthermore, the organic solvent in step 1.3 is one of petroleum ether, methanol and carbon disulfide. These substances are used as organic solvents because they not only have the effect of liquefying coal, but also have the characteristics of being flammable and volatile, providing combustion support for subsequent gasification and combustion.

[0015] Further, the step 2 is specifically as follows: 2.1. Laying out hot water exchange pipes: Lay out hot water exchange pipes from each vertical well to the target coal seam, and the ends of each hot water exchange pipe in the target coal seam are interconnected through high temperature resistant pipes in the horizontal well.

[0016] 2.2. In-situ coal gasification and combustion: The methane-air mixture in the horizontal well and surrounding fractures is ignited by electric shock ignition. The high-temperature environment formed by the combustion of the mixture causes the potassium permanganate solution remaining in the horizontal well and fractures to decompose and release oxygen, continuously providing oxygen for coal seam combustion. At the same time, the residual organic solvent acts as a combustion aid to maintain the continuity of combustion. At the same time, the CO2 gas produced by combustion can promote the gas desorption rate in the coal seam due to the displacement effect.

[0017] 2.3. Thermal extraction: When combustion starts in step 2.2, water is injected into the arranged heat exchange water pipe from at least one of the vertical wells. When the water passes through the horizontal well, heat exchange is performed so that the water temperature continues to rise to form high-temperature water. Finally, the water is extracted from at least one other vertical well. This cycle is repeated to achieve thermal extraction of gasification combustion.

[0018] Furthermore, in step 2.1, the annulus between the hot water exchange pipe and the vertical well is sealed with an annular plug to prevent the gas in the horizontal well from escaping from the vertical wells.

[0019] Furthermore, in step 2.2, after gasification and combustion, a gas extraction pump is used to extract gas from at least one vertical well to collect CO2 gas after coal seam combustion to prevent it from directly escaping into the atmosphere and exacerbating the greenhouse effect.

[0020] Further, the step three is specifically as follows: 3.1. Microbial filling and reinforcement: After the coal seam is completely burned out, the hot water exchange pipe is recovered, and slurry containing microorganisms is injected into the horizontal well for filling and reinforcement, and each vertical well is closed; the slurry filling and reinforcement supports the goaf area, facilitating the safe and stable operation of the next round of deep in-situ resource composite fluidized mining.

[0021] 3.2. Microbial degradation: After injection, the microorganisms in the slurry utilize the fracture network to diffuse into the surrounding residual coal seams and continuously react with the remaining coal body. The microorganisms are a mixture of hydrolytic bacteria, fermentative acid-producing bacteria, hydrogen-producing and acetic acid-producing bacteria, and methanogenic bacteria. The combined degradation effect of each bacteria community is utilized to desorb the methane gas in the remaining coal body, which is finally extracted through vertical wells to complete deep in-situ resource exploitation. This method can maximize the utilization rate of deep in-situ resource exploitation.

[0022] Furthermore, in step 3.1, in order to ensure the activity of microorganisms and enhance their degradation effect, grouting and reinforcement are started after the underground environment is cooled to a temperature suitable for the survival of microorganisms.

[0023] Compared with the prior art, the present invention has the following advantages: 1. The present invention provides a flow channel for the in-situ liquefaction of coal resources by deploying well groups and hydraulic fracturing technology. The organic solvent flows in the cracks, increasing the contact area with the coal seam and improving the dissolution efficiency of the coal seam. After dissolution, the coal slurry solid-liquid mixture is extracted for subsequent utilization, thereby ensuring the utilization rate of coal liquefaction. At the same time, the fracture network formed during the liquefaction process can allow the gas desorbed in the coal seam to enter the horizontal well to form a methane-air mixture, and the fracturing fluid contains potassium permanganate and the organic solvent is a flammable and volatile solvent. These conditions provide the necessary guarantee for the in-situ gasification and combustion of deep resources in the next stage.

[0024] 2. When the present invention performs gasification combustion on the solid coal resources remaining after liquefaction, the methane-air mixture is ignited and potassium permanganate can continuously decompose oxygen when heated to provide continuous oxygen for combustion, thereby reducing the injection amount of oxygen-containing air. The organic solvent acts as a combustion aid and plays a significant combustion-aiding role in the coal combustion process, thereby maintaining combustion stability. The combustion also solves the problem of chemical reagents remaining underground, thereby effectively reducing pollution to the surrounding environment. The CO2 gas generated during the combustion process adsorbs more CO2 to the coal seam than to gas, so its contact with the surrounding coal body can drive and promote the rapid desorption of gas in the coal seam, thereby ensuring the sustainability of the combustion process.

[0025] 3. After completing the combined liquefaction and gasification mining, the present invention injects the slurry in which the microorganisms are cultivated into the well for filling and reinforcement. At the same time, the combined degradation action of multiple microorganisms is used to continue to desorb and extract methane gas from the residual coal resources, so as to maximize the mining and utilization rate of the coal resources.

[0026] 4. The present invention is based on the theory of fluidized mining of deep in-situ resources, and integrates liquefaction, gasification and microbial degradation of deep in-situ resources to form integrated mining. Different fluidized mining technologies are implemented in stages, and different stages of mining can provide assistance for the implementation of other stages. It not only greatly improves the utilization efficiency of deep in-situ resource conversion and significantly improves the resource recovery rate, but also processes the chemical reagents remaining underground, effectively alleviating environmental pollution problems, and providing technical support for the development of the theory of fluidized mining of deep in-situ resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of the fluidized mining stage of deep in-situ resources in the present invention; Figure 2 It is a schematic diagram of constructing a U-shaped well group and coal seam hydraulic fracturing in the present invention; Figure 3 It is a schematic diagram of deep in-situ coal resource liquefaction in the present invention; Figure 4 It is a schematic diagram of deep in-situ coal resource gasification in the present invention; Figure 5 It is a schematic diagram of the microbial slurry filling and consolidation of the coal seam in the present invention.

[0028] In the figure: 1. Coal seam, 2. Middle vertical well, 3. Vertical wells on both sides, 4. Horizontal well, 5. Fracture network, 6. Organic solvent, 7. Hot water exchange pipe, 8. Annular plug, 9. Water, 10. Water vapor, 11. Slurry containing microorganisms. DETAILED DESCRIPTION

[0029] The present invention will be further described below.

[0030] like Figure 1 As shown, the specific steps of the present invention are: Step 1: Deep in-situ resource liquefaction mining: first lay out the well group, then carry out hydraulic fracturing construction, and finally carry out in-situ coal liquefaction extraction to obtain a coal slurry solid-liquid mixture, and form a methane-air mixture in the well group, specifically: 1.1、Layout of U-shaped well group: Figure 2 As shown, three vertical wells are first constructed from the ground to the target coal seam 1, namely the middle vertical well 2 and the vertical wells 3 on both sides, and the wellheads of each vertical well are on the same straight line on the ground; the deepest parts of adjacent vertical wells are connected by constructing horizontal wells 4 to complete the U-shaped well group layout.

[0031] 1.2. Hydraulic fracturing construction: Figure 2As shown, a perforating gun is used to perforate the surrounding coal body in a horizontal well, and then a fracturing fluid containing potassium permanganate is injected from each vertical well into the horizontal well 4 for hydraulic fracturing, so that a fracture network 5 is formed in the surrounding coal body, and the initial fracturing of the coal seam 1 is achieved, thereby promoting the desorption of coal seam 1 gas and escaping from the fractures into the horizontal well 4 to form a methane-air mixture; the fracturing fluid containing potassium permanganate is formed by mixing potassium permanganate particles with conventional fracturing fluid, and the concentration of potassium permanganate in the conventional fracturing fluid after mixing is 20%. During the hydraulic fracturing construction, the injection amount of the fracturing fluid containing potassium permanganate is controlled at 1.0~5.0m 3 / min, and is adjusted within this range according to the permeability and porosity of the coal seam to ensure the generation of the fracture network 5 and the subsequent decomposition and release of sufficient oxygen; the injection pressure is controlled within the range of 10-60MPa, and is adjusted within this range according to the fracture pressure of the coal seam 1 and the stable expansion pressure of the fracture to ensure that the fluid pressure around the horizontal well is higher than the fracture pressure of the coal seam 1 and lower than the fracture pressure of the adjacent rock formations, so that the fracture network 5 is only generated in the coal seam 1.

[0032] 1.3. In-situ coal liquefaction: Figure 3 As shown, an organic solvent 6 is injected from each vertical well into the horizontal well, and the organic solvent 6 enters the fracture network 5 formed in step 1.2 to impact the coal body, thereby increasing the contact area between the organic solvent 6 and the coal body; after the injection is completed, the organic solvent is allowed to stand for a period of time, and with the help of the high temperature conditions underground, the organic solvent and the coal seam 1 are thermally dissolved, liquefied to form a coal slurry solid-liquid mixture, and finally the coal slurry solid-liquid mixture is pumped out using a surface pump, at which time the fracture further expands to achieve secondary fracturing and accelerate the desorption of the remaining coal seam gas to the horizontal well 4; the organic solvent 6 is one of petroleum ether, methanol, and carbon disulfide. These substances are used as organic solvents because they not only have the effect of liquefying coal, but also have the characteristics of being flammable and volatile, providing combustion support for subsequent gasification and combustion.

[0033] Step 2: Deep in-situ resource gasification mining: firstly, the heat exchange pipe 7 is laid, then the methane-air mixture is subjected to in-situ coal gasification combustion, and finally, the combustion heat is extracted and utilized by the continuous flow of water in the heat exchange pipe 7. Figure 4 As shown, specifically: 2.1. Laying out hot water exchange pipes: Laying out hot water exchange pipes 7 from each vertical well to the target coal seam 1 , and the ends of each hot water exchange pipe 7 in the target coal seam 1 are interconnected through a high temperature resistant pipe in the horizontal well 4 .

[0034] 2.2. In-situ coal gasification and combustion: The methane-air mixture in the horizontal well 4 and the surrounding fractures is ignited by electric shock ignition. The high-temperature environment formed by the combustion of the mixture causes the potassium permanganate solution remaining in the horizontal well 4 and the fractures to decompose and release oxygen, which continuously provides oxygen for the combustion of the coal seam. At the same time, the residual organic solvent acts as a combustion aid to maintain the continuity of combustion. At the same time, the CO2 gas produced by the combustion can promote the gas desorption rate in the coal seam due to the displacement effect.

[0035] 2.3. Thermal extraction: When combustion starts in step 2.2, water 9 is injected into the arranged heat exchange water pipes 7 from the vertical wells 3 on both sides. The water 9 undergoes heat exchange when passing through the horizontal well 4, causing the water temperature to continuously rise to form high-temperature water and water vapor 10, which is finally extracted from the middle vertical well 2. This cycle is repeated to achieve thermal extraction of gasification combustion.

[0036] Step 3: Deep in-situ resource reinforcement and degradation: First, fill and reinforce the deep coal seam 1, and use microorganisms to degrade the residual coal body and extract methane gas. After completion, repeat steps 1 to 3 according to the distribution of other coal seams, and carry out composite fluidized mining on the next target coal seam 1. Figure 5 As shown, specifically: 3.1. Microbial filling and reinforcement: After the coal seam 1 is completely burned, the hot water exchange pipe 7 is recovered. To ensure the activity of microorganisms and improve their degradation effect, after the underground environment is cooled to a temperature suitable for the survival of microorganisms, slurry containing microorganisms is injected into the horizontal well 4 for filling and reinforcement, and each vertical well is closed; the filling and reinforcement of the slurry supports the goaf area, facilitating the safe and stable operation of the next round of deep in-situ resource composite fluidized mining.

[0037] 3.2. Microbial degradation: After injection, the microorganisms in the slurry utilize the fracture network to diffuse into the surrounding residual coal seams and continuously react with the remaining coal body. The microorganisms are a mixture of hydrolytic bacteria, fermentative acid-producing bacteria, hydrogen-producing and acetic acid-producing bacteria, and methanogenic bacteria. The combined degradation effect of each bacteria community is utilized to desorb the methane gas in the remaining coal body, which is finally extracted through various vertical wells to complete deep in-situ resource exploitation. This method can maximize the utilization rate of deep in-situ resource exploitation.

[0038] As an improvement of the present invention, the annulus between the hot water exchange pipe 7 and the vertical well in step 2.1 is sealed with an annular plug 8 to prevent the gas in the horizontal well 4 from escaping from the vertical wells; and after gasification and combustion, an extraction pump is used to extract gas from the middle vertical well 2 to collect CO2 gas after coal seam combustion to prevent it from directly escaping into the atmosphere and aggravating the greenhouse effect.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A deep in-situ resource composite fluidized mining method, characterized in that: The specific steps are: Step 1: Deep in-situ resource liquefaction mining: firstly, the well group is laid out, then hydraulic fracturing is carried out, and finally, the coal is liquefied in-situ to obtain a coal slurry solid-liquid mixture, and a methane-air mixture is formed in the well group; Step 2: Deep in-situ resource gasification and mining: first, heat exchange pipes are laid, then the methane-air mixture is gasified and burned in-situ, and finally, the combustion heat is extracted and utilized through the continuous flow of water in the heat exchange pipes; Step 3: Deep in-situ resource reinforcement and degradation: First, fill and reinforce the deep coal seam, and use microorganisms to degrade the residual coal body and extract methane gas. After completion, repeat steps one to three according to the distribution of the remaining coal seams, and carry out composite fluidized mining on the next target coal seam.

2. The deep in-situ resource composite fluidized mining method according to claim 1 is characterized in that: The step 1 is specifically as follows: 1.

1. Layout of well group: First, construct at least two vertical wells from the ground to the target coal seam, and the wellheads of each vertical well are on the same straight line on the ground; the deepest parts of adjacent vertical wells are connected by constructing horizontal wells to complete the layout of the well group; 1.

2. Hydraulic fracturing construction: Use a perforating gun to perforate the surrounding coal body in the horizontal well, and then inject fracturing fluid containing potassium permanganate from each vertical well into the horizontal well for hydraulic fracturing, so that a fracture network is formed in the surrounding coal body, achieving the initial fracturing of the coal seam, and then promoting the desorption of coal seam gas and escaping from the fractures into the horizontal well to form a methane-air mixture; 1.

3. In-situ liquefaction of coal: Inject organic solvents from each vertical well into the horizontal well. The organic solvents enter the fracture network formed in step 1.2 to impact the coal body, increasing the contact area between the organic solvent and the coal body. After the injection is completed, the organic solvent is allowed to stand for a period of time. With the help of the high temperature conditions underground, the organic solvent and the coal seam are thermally dissolved and liquefied to form a coal slurry solid-liquid mixture. Finally, the coal slurry solid-liquid mixture is pumped out using a surface pump. At this time, the fractures are further expanded to achieve secondary fracturing and accelerate the desorption of the remaining coal seam gas to the horizontal well.

3. The deep in-situ resource composite fluidized mining method according to claim 2 is characterized in that: The fracturing fluid containing potassium permanganate in step 1.2 is formed by mixing potassium permanganate particles with fracturing fluid, and the concentration of potassium permanganate in the fracturing fluid after mixing is 20%.

4. The deep in-situ resource composite fluidized mining method according to claim 2 is characterized in that: During the hydraulic fracturing in step 1.2, the injection volume of the fracturing fluid containing potassium permanganate is controlled at 1.0-5.0 m 3 / min, and is adjusted within this range according to the permeability and porosity of the coal seam to ensure the generation of the fracture network and the subsequent decomposition and release of sufficient oxygen; the injection pressure is controlled within the range of 10~60MPa, and is adjusted within this range according to the coal seam fracture pressure and the stable expansion pressure of the fracture to ensure that the fluid pressure around the horizontal well is higher than the fracture pressure of the coal seam and lower than the fracture pressure of the adjacent rock formation, so that the fracture network is only generated in the coal seam.

5. The deep in-situ resource composite fluidized mining method according to claim 2 is characterized in that: The organic solvent in step 1.3 is one of petroleum ether, methanol and carbon disulfide.

6. The deep in-situ resource composite fluidized mining method according to claim 1 is characterized in that: The step 2 is specifically as follows: 2.

1. Laying out hot water exchange pipes: Laying out hot water exchange pipes from each vertical well to the target coal seam, and the ends of each hot water exchange pipe in the target coal seam are interconnected through high temperature resistant pipes in the horizontal well; 2.

2. In-situ coal gasification and combustion: The methane-air mixture in the horizontal well and the surrounding fractures is ignited by electric shock ignition. The high temperature environment formed by the combustion of the mixture causes the potassium permanganate solution remaining in the horizontal well and the fractures to decompose and release oxygen, which continuously provides oxygen for coal seam combustion. At the same time, the residual organic solvent acts as a combustion aid to maintain the continuity of combustion. At the same time, the CO2 gas produced by the combustion can promote the gas desorption rate in the coal seam due to the displacement effect. 2.

3. Thermal extraction: When combustion starts in step 2.2, water is injected into the arranged heat exchange water pipe from at least one of the vertical wells. When the water passes through the horizontal well, heat exchange is performed so that the water temperature continues to rise to form high-temperature water. Finally, the water is extracted from at least one other vertical well. This cycle is repeated to achieve thermal extraction of gasification combustion.

7. The deep in-situ resource composite fluidized mining method according to claim 6, characterized in that: In step 2.1, the annulus between the hot water exchange pipe and the vertical well is sealed with an annular plug to prevent the gas in the horizontal well from escaping from the vertical wells.

8. The deep in-situ resource composite fluidized mining method according to claim 6, characterized in that: In step 2.2, after gasification and combustion, a gas extraction pump is used to extract gas from at least one vertical well to collect CO2 gas after coal seam combustion.

9. The deep in-situ resource composite fluidized mining method according to claim 1, characterized in that: The step three is specifically as follows: 3.

1. Microbial filling and reinforcement: After the coal seam is completely burned, the heat exchange pipe is recovered, and slurry containing microorganisms is injected into the horizontal well for filling and reinforcement, and each vertical well is sealed; 3.

2. Microbial degradation: After injection, the microorganisms in the slurry utilize the fracture network to diffuse into the surrounding residual coal seams and continuously react with the remaining coal body. The microorganisms are a mixture of hydrolytic bacteria, fermentative acid-producing bacteria, hydrogen-producing and acetic acid-producing bacteria, and methanogenic bacteria. The combined degradation effect of each bacteria community is utilized to desorb the methane gas in the remaining coal body, which is finally extracted through vertical wells to complete deep in-situ resource mining.

10. The deep in-situ resource composite fluidized mining method according to claim 9, characterized in that: In step 3.1, in order to ensure the activity of microorganisms and enhance their degradation effect, grouting and reinforcement are started after the underground environment is cooled to a temperature suitable for the survival of microorganisms.

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