Underground coal combustion gasification and carbon dioxide sequestration mining and treatment method

Abstract

The present invention discloses a method for underground coal combustion gasification and carbon dioxide sequestration exploitation and treatment, and the method includes: S1. Injection pressure fracturing: Injecting fracturing gas through the gas outlet well to form a fracture network in the corresponding coal seam in the gasification area to be exploited; S2. Combustion gasification: Taking the bottom end of the intake well of the furnace to the bottom end of the mountain gas well as the exploitation direction and discharging the synthesis gas through the gas outlet well of the furnace; S3. Sealing and closing the well: Injecting carbon dioxide as the displacement gas into the space to be sealed through the intake well and collecting the mixed gas through the gas outlet well, and then injecting high-pressure CO2 gas into the space to be sealed for sequestration treatment. In the present invention, horizontal fracturing injection channels are used for injection pressure fracturing treatment of the gasification area to be exploited in the upper furnace in the injection pressure fracturing of a single furnace to form a fracture network. The present invention can realize the differential node follow-up of the upper and lower furnace wells together and according to the process flow with a difference of one process node, reduce the sealing difficulty of the well and the combustion void area, and improve the exploitation efficiency.

Description

Technical Field

[0001] The present invention relates to the field of underground coal gasification mining, and particularly to a method for underground coal combustion gasification and carbon dioxide sequestration mining treatment. Background Art

[0002] Underground coal gasification is a process of directly converting underground coal resources into coal gas. Underground coal gasification can efficiently convert underground coal resources into utilizable energy, improve coal mining efficiency, and reduce coal mining costs. Before the development of deep underground coal gasification, a large amount of geological exploration and survey work needs to be carried out to ensure the stability of the boreholes in the rock formation. Underground coal gasification also faces many challenges, such as the complexity of geological conditions, combustion control during the gasification process, environmental pollution problems, and technical difficulties, etc., which all need to be further solved. Currently, underground coal gasification mining often adopts the method of drilling a mine shaft from the ground, and then conducting combustion gasification at the bottom of the mine shaft to produce syngas. During combustion gasification, a gasifying agent is transported to the coal combustion gasification area, and at the same time, the syngas containing combustible gas needs to be collected. After mining, the gob area needs to be sealed and protected. The existing underground coal gasification mining technology still faces many problems that need to be overcome, resulting in difficulties in mining and low mining efficiency, etc. Therefore, the process operation of underground coal gasification is the research direction of the application of underground gasification technology. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for underground coal combustion gasification and carbon dioxide sequestration mining treatment for safe and efficient underground gasification mining, which adopts a process technology with three process nodes of injection pressure fracturing, combustion gasification, and sealing and closing the well in a single furnace. The injection pressure fracturing uses a horizontal fracturing injection gas channel to conduct injection pressure fracturing treatment on the gasification area to be mined above the furnace to form a fracture network. The horizontal fracturing injection gas channel plays the role of connecting two wells, which can make the two wells have a farther distance, reduce the number of wells and the influence of wells on the coal rock formation, and improve the mining safety.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A method for underground coal combustion gasification and carbon dioxide sequestration mining treatment, the method comprising:

[0006] S1. Injection pressure fracturing: Construct the intake well and the outlet well of the furnace. The bottom of the outlet well extends horizontally to the bottom of the intake well and is not connected. Inject fracturing gas through the outlet well to conduct injection pressure fracturing on the gasification area to be mined in the furnace and form a fracture network in the corresponding coal seam of the gasification area to be mined. After the injection pressure fracturing is completed, horizontally extend the bottom of the outlet well to form a part of the horizontal fracturing injection gas channel and connect it with the bottom of the intake well;

[0007] S2. Combustion gasification: Taking the bottom end of the intake well of the furnace to the bottom end of the outlet well as the mining direction, introduce the gasifying agent through the intake well to conduct coal seam combustion gasification operation on the gasification area to be mined in the furnace, and discharge and collect the synthesis gas through the outlet well of the furnace, and separate the combustible gas from the synthesis gas; after the combustion gasification of the gasification area to be mined in the furnace is completed, a burned-out area is formed, and the burned-out area of the furnace is cooled;

[0008] S3. Sealing and closing the well: After the burned-out area of the furnace is cooled, the outlet well, the burned-out area, and the intake well of the furnace form a space to be sealed. Inject carbon dioxide as the displacement gas into the space to be sealed through the intake well and collect the mixed gas through the outlet well, and separate the combustible gas from the mixed gas; detect the mixed gas at the outlet well, and stop the displacement operation when the proportion of the displacement gas detected in the mixed gas reaches P%; then block one end of the space to be sealed close to the outlet well, inject high-pressure CO2 gas into the space to be sealed through the intake well for sealing, and then seal the cement plug at one end of the space to be sealed close to the intake well and install a leakage detection device for leakage monitoring and alarm.

[0009] To better implement the present invention, the present invention includes a combined supply and treatment system. The combined supply and treatment system includes a synthesis gas separation system, a high-pressure carbon dioxide supply system, and a gasifying agent supply system. The high-pressure carbon dioxide supply system includes a CO2 gas storage tank and a high-pressure carbon dioxide control and compression unit connected to the CO2 gas storage tank. The high-pressure carbon dioxide control and compression unit generates high-pressure CO2 and is used as the fracturing gas for injection fracturing; the gasifying agent supply system includes a steam generation device, an oxygen generation device, a gasifying agent control station, and an injection high-pressure pump group. The steam generation device is used to produce steam, the oxygen generation device is used to produce oxygen, the gasifying agent control station is respectively connected to the steam generation device and the oxygen generation device and mixes and proportions steam and oxygen as the main components to form a gasifying agent and transports it to the injection high-pressure pump group. The injection high-pressure pump group is used to generate high-pressure gasifying agent and input it into the gasification area to be mined in the furnace for coal seam combustion gasification; the gas separation system is used to collect the synthesis gas generated by coal seam combustion gasification or / and the mixed gas discharged during the displacement operation and separate to obtain the combustible gas.

[0010] Preferably, an air injection pipe for the gasifying agent is connected and communicated at the outlet end of the injection high-pressure pump group, a gas collection pipe is connected and communicated at the intake end of the synthesis gas separation system, and a fracturing injection pipe is connected and communicated at the outlet end of the high-pressure carbon dioxide control and compression unit; during the injection fracturing stage of step S1, let the fracturing injection pipe be hermetically connected to the outlet well of the furnace or let the fracturing injection pipe extend into the horizontal fracturing injection channel part of the outlet well of the furnace and conduct injection fracturing operation on the upper gasification area to be mined. A gas sensor is set at the wellhead of the intake well of the furnace to detect whether there is fracturing gas outlet;

[0011] In the combustion gasification stage of step S2, remove the gas sensor from the intake well of the furnace, make the gasifier injection pipe communicate with the intake well of the furnace in a sealed manner, or extend the gasifier injection pipe deep into the horizontal fracturing injection gas channel part of the furnace and advance along the mining direction, make the gas extraction pipe communicate with the outlet well of the furnace in a sealed manner, and the syngas generated by combustion gasification in the gasification area to be mined in the furnace enters the syngas separation system through the gas extraction pipe and combustible gas is separated.

[0012] Preferably, the gas separation system is also connected to the user and the storage terminal, and the combustible gas separated by the gas separation system is transported to the user and the storage terminal; the gas separation system is respectively connected to the CO2 storage tank and the gasifier control station, and the CO2 gas separated by the gas separation system is respectively transported to the CO2 storage tank and the gasifier control station. The gasifier control station also adds CO2 gas as a new gasifier in the corresponding ratio of the gasifier mainly composed of water vapor and oxygen. During the gas displacement in the space to be sealed in step S3 of the well sealing stage, make the gasifier control station only mix CO2 gas and inject high-pressure CO2 gas through the gasifier injection pipe, make the gas extraction pipe communicate with the outlet well of the furnace in a sealed manner, and the mixed gas displaced from the space to be sealed in the furnace enters the syngas separation system through the gas extraction pipe and combustible gas is separated.

[0013] Preferably, before fracturing injection in the gasification area to be mined in the furnace, first conduct a sealing operation for the fracturing injection stage on the bottom of the outlet well of the furnace using a packer. The front section of the fracturing injection pipe is an injection distribution pipe, and the injection distribution pipe is placed in the water production fracturing injection gas channel part and is connected with a number of shunt nozzles. Each shunt nozzle is distributed at the bottom of the gasification area to be mined in the furnace, and high-pressure CO2 is injected into the coal seam inside the gasification area to be mined through each shunt nozzle of the injection distribution pipe to form a fracture network in the coal seam.

[0014] Preferably, the intake well or / and the outlet well of the furnace are constructed using a drilling tool, and the horizontal extension of the bottom of the outlet well of the furnace is constructed using a drilling tool equipped with a bit guidance system for horizontal extension; the intake well and the outlet well of the furnace are both reinforced and protected by casing during the working stage.

[0015] Preferably, the drilling tool equipped with a bit guidance system includes a bit, a bent screw power drill installed at the rear end of the bit to drive the bit, and a downhole tractor for horizontal fracturing injection gas channel to provide the traction power for the horizontal extension construction of the bit. The bit guidance system includes a bit guidance tool installed on the bit to steer or guide the bit.

[0016] Preferably, the temperature reduction in the combustion-empty area of the furnace also includes the following detection method: a temperature sensor for monitoring the temperature of the combustion-empty area is installed in the intake well of the furnace. When the temperature sensor drops to the ambient temperature, the idle temperature reduction of the combustion-empty area of the furnace is completed.

[0017] The present invention can realize continuous follow-up operation of all furnaces according to the process technology, and the specific method is as follows:

[0018] Select a coal mining area, plan the furnaces for continuous advancement of the coal mining area, and number them in order of furnace 1, furnace 2, furnace 3, ..., furnace N. Each furnace is processed according to the three process nodes of gas injection fracturing, combustion gasification, and sealing and closing the well;

[0019] When the gas injection and fracturing stage of furnace one is in progress or completed, the gas outlet well of furnace two is followed up; when furnace one is in the process of combustion and gasification, the gasification waiting area of ​​furnace two is subjected to gas injection and fracturing through the gas outlet well of furnace two; when the combustion and gasification of furnace one is completed, the gas outlet well of furnace one is used as the gas inlet well of furnace two, and the ignition and gasification of furnace two is followed up, and at the same time, the gas outlet well of furnace three is followed up; when furnace one is cooled down and enters the sealing and well closing stage, the gas outlet channel of furnace one near one end of the gas outlet well is blocked; when the combustion and gasification of furnace two is completed, the gas outlet well of furnace two is used as the gas inlet well of furnace three, and the gas injection and fracturing of furnace three is followed up, and at the same time, the gas outlet well of furnace four is followed up, and furnace two enters the sealing and well closing stage;

[0020] According to the above method, the process technology of the three process nodes of gas injection fracturing, combustion gasification and sealing and closing of the well in the subsequent furnace is realized in sequence.

[0021] Preferably, all furnaces complete the process technology in sequence with the outlet well of the previous furnace serving as the inlet well of the next furnace; all furnaces in the coal mining area follow up continuously in a straight line or in an S-shaped manner according to the furnace sequence.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) The present invention adopts a process-based technology with three process nodes, namely, gas injection fracturing, combustion gasification, and sealing and closing of the well, in a single furnace. The gas injection fracturing adopts a horizontal fracturing gas injection channel to perform gas injection fracturing treatment on the furnace gasification mining area located above to form a fracture network. The horizontal fracturing gas injection channel serves to connect the two wells, allowing the two wells to be farther apart, reducing the number of wells and the impact of the wells on the coal strata, and improving mining safety.

[0024] (2) When the furnace is used for injection pressure fracturing, a horizontal fracturing injection gas channel will be formed by the horizontal extension of the bottom of the gas outlet well of the furnace. In this way, the gas outlet well is equipped with a horizontal fracturing injection gas channel, which is not connected to the gas inlet well during the injection pressure fracturing stage. The high-pressure CO2 is injected into the corresponding gasification and mining area above through the distributed shunt nozzles in the horizontal fracturing injection gas channel of the gas outlet well for injection pressure fracturing to form a fracture network in the coal seam, releasing the coal stress in advance and improving the combustion gasification safety and gasification efficiency. The high-pressure injection of CO2 can also effectively displace the coalbed methane. Since there is a horizontal fracturing injection gas channel between the gas outlet well and the gas inlet well of the furnace, the gas outlet well and the gas inlet well can be arranged at a farther distance, and a part of the horizontal fracturing injection gas channel of the gas outlet well is used to undertake the distributed high-pressure CO2 injection pressure fracturing of the gasification and mining area of the furnace. The farther distance between the wells proves that the present invention can drill fewer wells and promote safer and more efficient mining.

[0025] (3) Each underground gasification mining of the furnace in the present invention is carried out according to the process of injection pressure fracturing, combustion gasification, and sealing and closing the well, and the upper and lower furnaces follow up with a difference in one process node according to the process. The gas outlet well after injection pressure fracturing of the next furnace is used as the gas inlet well of the next furnace. In this way, a shared inlet and outlet directional well is formed. By continuously following up with the process method of the present invention, the common use of the upper and lower furnace wells can be realized, reducing the number of wells drilled and the drilling workload. At the same time, the degree of geological damage to the coal rock layer is also reduced, and the difficulty of sealing the well and the combustion void area is lowered.

[0026] (4) When furnace one is in the cooling stage, furnace two follows up in the combustion gasification stage, and furnace three follows up in the injection pressure fracturing stage. At this time, construction of furnace four can start to follow up, thus forming a differential node follow-up with the front and rear furnaces sharing the same well and continuously coordinated advancement, reducing the construction of some wells. Therefore, the mining efficiency is effectively improved. It can be continuously mined in a straight line, circular, or S-shaped manner in the coal mining area. Taking straight-line mining as an example, multiple continuous mining straight-line advancement paths can be designed and planned, and multiple differential node follow-up mining methods can be carried out simultaneously, enhancing the gasification efficiency and ensuring the orderly succession of multiple process nodes. The mining is fast, the production is fast, the total mining output is increased, and the mining efficiency is greatly improved.

[0027] (5) In the present invention, there are clear requirements or monitoring at the end and handover of each process node. For example, when the injection pressure fracturing is completed, the gas outlet of the fracture network is monitored through a gas sensor. For example, when the CO2 sealing and closing the well treatment is completed, leakage monitoring and alarm are also carried out through a leakage detection device set at the wellhead, ensuring the working efficiency and safety performance of the mining follow-up work. Description of the Drawings

[0028] Figure 1 It is the layout structure and working principle diagram of the furnace in the injection pressure fracturing process stage in Embodiment 2;

[0029] Figure 2 is Figure 1 a schematic structural diagram of the combined supply processing system in

[0030] Figure 3 is the layout structure and working principle diagram of the furnace in the combustion gasification process stage in the second embodiment;

[0031] Figure 4 is the layout structure and working principle diagram of the furnace in the sealed well process stage in the second embodiment;

[0032] Figure 5 is the schematic principle diagram of the first furnace and the second furnace sharing the first furnace well in the second embodiment;

[0033] Figure 6 is Figure 1 a partial enlarged schematic diagram of

[0034] Among them, the names corresponding to the reference numerals in the drawings are as follows:

[0035] 1 - Gasifying agent control station, 2 - Steam generating device, 3 - Oxygen generating device, 4 - Injection high-pressure pump group, 41 - Gasifying agent injection pipe, 5 - CO2 gas storage tank, 6 - High-pressure carbon dioxide control and compression unit, 61 - Fracturing injection pipe, 7 - Syngas separation system, 71 - Gas extraction pipe, 8 - User and storage end, 9 - Injection distribution pipe, 10 - Casing, 11 - Drill bit, 12 - Drill bit guiding tool, 13 - Bent screw power drill, 14 - Downhole tractor for horizontal fracturing injection gas channel, 15 - Injection control valve, 16 - Diverging nozzle, 17 - Packer, 18 - Gas sensor, 19 - Fracture network, 20 - Grouting pipeline, 21 - Cement plugging block, 22 - Combustion cavity, 23 - Temperature sensor, 24 - Cement plug, 25 - Leak detection device. Specific embodiments

[0036] The present invention will be further described in detail below in conjunction with the embodiments:

[0037] Embodiment 1

[0038] As Figures 1 to 4 shown, a method for underground coal combustion gasification and carbon dioxide sequestration and exploitation treatment, the method includes:

[0039] S1. Injection and fracturing: Construct the intake well and the outlet well of the furnace, and the bottom of the outlet well extends horizontally to the bottom of the intake well and is not connected (see Figure 1 , during the injection and fracturing stage, the horizontally extending horizontal fracturing injection gas channel at the bottom of the outlet well is not connected to the bottom of the intake well, specifically see Figure 1(The unconnected positions in the middle are indicated by dashed lines), fracturing gas is introduced through the gas production well to inject pressure fracturing into the gasification area to be mined in the furnace and form a fracture network 19 in the coal seam corresponding to the gasification area to be mined (the fracture network 19 improves the subsequent combustion gasification efficiency); the horizontal fracturing injection gas channel extending horizontally at the bottom of the gas production well of the present invention can increase the distance between the gas injection well and the gas production well, and can complete the pressure fracturing operation within a large distance between the gas injection well and the gas production well, so that the number of construction wells in the entire coal mining area is greatly reduced, effectively reducing the impact on coal rock strata and improving the safety performance of underground combustion gasification; at the same time, using the horizontal fracturing injection gas channel to inject pressure fracturing treatment from the bottom towards the gasification area to be mined in the furnace can greatly improve the pressure fracturing efficiency, and then improve the subsequent combustion gasification efficiency. After the pressure fracturing injection is completed, the part of the horizontal fracturing injection gas channel extending horizontally at the bottom of the gas production well is connected to the bottom of the gas injection well (after the pressure fracturing injection is completed, the horizontal fracturing injection gas channel extending horizontally at the bottom of the gas production well is connected to the bottom of the gas injection well, see Figure 3 The connected positions in the middle are indicated by solid lines).

[0040] S2. Combustion gasification: Taking the bottom end of the gas injection well of the furnace to the bottom end of the gas production well as the mining direction (taking Figure 3 as an example, the mining direction is from right to left), gasifying agent is introduced through the gas injection well to carry out coal seam combustion gasification operation on the gasification area to be mined in the furnace and discharge and collect the syngas through the gas production well of the furnace (the coal seam combustion gasification operation generates syngas containing combustible gas, which is discharged through the gas production well and collected at the end of the gas production well, and then the syngas is separated and processed to finally obtain the required combustible gas), and the combustible gas is separated from the syngas. After the gasification area to be mined in the furnace is burned and gasified, a burned-out area is formed, and the burned-out area in the furnace is cooled.

[0041] S3. Sealing and closing the well: After the burned-out area in the furnace is cooled, the gas production well, the burned-out area, and the gas injection well in the furnace form a space to be sealed. Carbon dioxide is used as the displacement gas and injected into the space to be sealed through the gas injection well, and the mixed gas is collected through the gas production well, and the combustible gas is separated from the mixed gas. The mixed gas is detected at the gas production well. When the proportion of the displacement gas (carbon dioxide is used as the displacement gas) detected in the mixed gas reaches P%, the displacement operation is stopped. Then, the end of the space to be sealed close to the gas production well is blocked, and high-pressure CO2 gas is injected into the space to be sealed through the gas injection well for sealing (coal is burned and gasified into cinder, and the cinder remains in the burned-out area. In order to protect the burned-out area, high-pressure CO2 gas needs to be injected for sealing protection), and then a cement plug is installed at the end of the space to be sealed close to the gas injection well and a leakage detection device is installed for leakage monitoring and alarm (the leakage detection device monitors whether there is gas discharge in the mined underground. If there is gas discharge, it means that there is leakage in the sealing and further measures need to be taken).

[0042] According to the above method, the furnace gas injection fracturing (i.e. step S1), combustion gasification (i.e. step S2), and sealing and closing the well (i.e. step S3) are a process node process.

[0043] Furthermore, the present invention can realize continuous follow-up operation of all furnaces according to the process technology, and the specific method is as follows:

[0044] A coal mining area is selected, and the furnaces for continuous advancement of operations in the coal mining area are planned. The furnaces are numbered in sequence as Furnace 1, Furnace 2, Furnace 3, ..., Furnace N. Each furnace follows the standardized process of three process nodes: gas injection fracturing, combustion gasification, and sealing and well closure.

[0045] When the gas injection and fracturing stage of furnace one is in progress or completed, follow up with the construction of the gas outlet well of furnace two. During the combustion and gasification process of furnace one, gas injection and fracturing are carried out on the gasification and mining area of ​​furnace two through the gas outlet well of furnace two. When the combustion and gasification of furnace one is completed, the gas outlet well of furnace one is used as the gas inlet well of furnace two, and the ignition and gasification of furnace two are followed up, and the gas outlet well of furnace three is followed up. When furnace one is cooled down and enters the sealing and well closing stage, the gas outlet channel of furnace one close to one end of the gas outlet well is blocked (such as Figure 4 As shown, the gas outlet channel is the channel between the gas outlet well and the gas inlet well, and the channel includes a combustion and air space, see Figure 4 , block the bottom of the outlet well of furnace one close to the outlet channel. At this time, the outlet channel is blocked at one end close to the outlet well, but the outlet well can still be used as the inlet well of the next furnace). When the combustion and gasification of furnace two is completed, the outlet well of furnace two is used as the inlet well of furnace three, and the gas injection and fracturing of furnace three is followed up. At the same time, the outlet well of furnace four is followed up, and furnace two enters the sealing and well closure stage. And so on, follow up the construction of furnaces five, six, ..., N in sequence; during the follow-up operation, the outlet well of the front furnace is used as the inlet well of the rear furnace (no need to construct an inlet well later, which effectively reduces the number of wells and improves mining efficiency and safety).

[0046] According to the above method, the process technology of gas injection fracturing, combustion gasification and sealing and closing of a process node of the subsequent furnace is realized in sequence.

[0047] The following example illustrates the continuous follow-up operation of the furnace according to the process technology. Take furnace 1 as the first furnace (the first furnace needs to construct the inlet and outlet wells, and the subsequent furnaces only construct the outlet wells and use the outlet wells of the previous furnace as the inlet wells). Since furnace 1 is the first furnace, furnace 1 is used as an example to introduce the gas injection fracturing technology method.

[0048] Gas injection fracturing method: The bottom of the outlet well of furnace 1 extends horizontally to the bottom of the inlet well of furnace 1 and is not connected (see Figure 1, horizontal drilling construction is carried out from the bottom of the gas outlet well of Furnace 1 and horizontally extended to form a horizontal fracturing gas injection channel. At this time, the end of the extended horizontal fracturing gas injection channel should not be connected to the bottom of the gas inlet well, so that the whole gas outlet well of Furnace 1 forms an L-shaped mine, and the L-shaped mine is not connected to the gas inlet well of Furnace 1 at this time. The L-shaped mine is a separate mine), and the gas outlet well of Furnace 1 is used to inject gas and fracture the gasification area to be mined in Furnace 1 (since the L-shaped mine is a separate mine, so the gasification area to be mined in Furnace 1 can be injected with gas and fractured. The gasification area to be mined in Furnace 1 is Figure 1 the area on the right side of the gas outlet well in

[0049] The above is an introduction to the gas injection and fracturing method taking Furnace 1 as an example. In the technology of the present invention, Furnace 2 follows the underground gasification operation of Furnace 1. After Furnace 1 has completed gas injection and fracturing, the gas outlet well of Furnace 1 serves as the gas inlet well of Furnace 2 (the upper and lower furnaces share a directional well, which can be called the inlet and outlet directional well), and Furnace 2 has a gas inlet well and a gas outlet well. Furnace 2 also carries out gas injection and fracturing on the gasification area to be mined in Furnace 2 according to the above gas injection and fracturing method. Furnace 3 follows the underground gasification operation of Furnace 2, and Furnace 3 also adopts the above gas injection and fracturing method. By analogy, the next furnace follows the previous furnace, and the next furnace carries out gas injection and fracturing operations on the corresponding gasification area to be mined according to the above gas injection and fracturing method.

[0050] After gas injection and fracturing is combustion gasification. Since Furnace 1 is the first furnace (subsequent furnaces follow in sequence), the combustion gasification technical method is introduced taking Furnace 1 as an example.

[0051] Combustion gasification method: Inject the proportioned gasifying agent into the bottom of the gas inlet well of Furnace 1 (at this time, the gas outlet well and the bottom of the gas inlet well of Furnace 1 are connected to each other), and carry out coal seam combustion gasification operation on the gasification area to be mined in Furnace 1 from the bottom of the gas inlet well towards the bottom of the gas outlet well, and collect the synthesis gas through the gas outlet well of Furnace 1. The synthesis gas contains combustible gases and also includes other substances that need to be removed and separated (such as water vapor, carbon dioxide, etc.). Subsequently, it is separated by the synthesis gas separation system 7 and the combustible gas is obtained (generally, the combustible gas will be further separated to meet different uses) and transported to the use and storage end 8.

[0052] The above is an introduction to the combustion gasification method taking Furnace 1 as an example. In the technology of the present invention, Furnace 2 follows the underground gasification operation of Furnace 1, and Furnace 3 follows the underground gasification operation of Furnace 2; when Furnace 1 is undergoing combustion gasification, Furnace 2 is carrying out gas injection and fracturing. The bottom of the gas outlet well of Furnace 2 is horizontally extended to the bottom of the gas outlet well of Furnace 1 (the gas outlet well of Furnace 1 starts to be regarded as the standby gas inlet well of Furnace 2) and is not connected. The gas outlet well of Furnace 2 is used to inject gas and fracture the gasification area to be mined in Furnace 2, and the gas injection and fracturing operation of Furnace 2 is carried out according to the aforementioned gas injection and fracturing method.

[0053] After the combustion and gasification in furnace one is completed, furnace two performs combustion and gasification operations according to the above-mentioned combustion and gasification method. After the combustion and gasification in furnace two is completed, furnace three then performs combustion and gasification operations according to the above-mentioned combustion and gasification method, and so on. The next furnace follows the previous one and performs combustion and gasification operations in the corresponding gasification area to be mined according to the above-mentioned combustion and gasification method.

[0054] When the combustion gasification and synthesis gas collection of the gasification and mining area of ​​furnace one are completed, the bottom of the gas outlet well of furnace two is horizontally extended to the bottom of the gas inlet well and connected to each other, and the gasification and mining area of ​​furnace one becomes a combustion and empty area. "When the combustion gasification and synthesis gas collection of the gasification and mining area of ​​furnace one are completed, the bottom of the gas outlet well of furnace two is horizontally extended to the bottom of the gas inlet well and connected to each other" is the condition for furnace two to follow furnace one, that is, when or after the synthesis gas collection operation of furnace one is completed, the bottom of the gas outlet well of furnace two is horizontally extended to the bottom of the gas inlet well of furnace two (at this time, the gas inlet well of furnace two and the gas outlet well of furnace one are the same well, called the gas inlet and outlet directional well) and connected to each other.

[0055] The above takes the idle cooling treatment of furnace one in the combustion empty zone as an example. The furnace two in the technology of the present invention follows the underground gasification operation of furnace one, and furnace three follows the underground gasification operation of furnace two. When furnace one is idle and cooled, furnace two performs combustion gasification, furnace three performs gas injection fracturing, and furnace four starts construction. After the combustion and gasification of furnace two is completed, it follows up and enters the sealing and well closure.

[0056] Sealing and well closing method: After the furnace completes combustion and gasification, the next step is to wait for the combustion and gas zone of the furnace to cool down. The furnace's gas outlet well, gas outlet well, and gas inlet well form a space to be sealed. Carbon dioxide is injected into the space to be sealed through the gas inlet well as a displacement gas, and the mixed gas is collected through the gas outlet well to separate the combustible gas from the mixed gas. The mixed gas is tested at the gas outlet well, and when the proportion of the displacement gas in the mixed gas reaches P%, the displacement operation is stopped. Then, the end of the space to be sealed close to the gas outlet well is blocked, and high-pressure CO2 gas is injected into the space to be sealed through the gas inlet well to seal it. Then, a cement plug is closed at one end of the space to be sealed close to the gas inlet well, and a leakage detection device is installed to monitor and alarm for leakage. After the first furnace is sealed and the well closed, furnace two will be sealed and the well closed according to the above-mentioned sealing and well closing treatment method. After the second furnace is sealed and the well closed, furnace three will be sealed and the well closed according to the above-mentioned sealing and well closing treatment method. And so on. The next furnace follows the previous one and the next furnace will seal and close the corresponding combustion zone according to the above-mentioned sealing and well closing treatment method.

[0057] It should be noted that the process of sealing and closing the well is a process after the furnace has completed the operations of injection pressure fracturing and combustion gasification. Since there is no tight operation follow-up process like that of injection pressure fracturing and combustion gasification between the front and rear furnaces, it can be processed in sequence according to the furnace order. Among them, the process of sealing and closing the well includes the process of cooling the combustion-empty area of the furnace (which can be called idle cooling), the CO2 displacement operation (relying on CO2 gas as the displacement gas to displace the mixed gas containing combustible gas in the space to be sealed), and the CO2 sealing and closing of the well (injecting high-pressure CO2 gas for CO2 sealing. At the beginning of CO2 sealing, one end of the space to be sealed is blocked, and after the CO2 sealing operation is completed, the other end of the space to be sealed is blocked, thus realizing the well closing process). The cooling of the combustion-empty area, the CO2 displacement operation, and the CO2 sealing and closing in the process of sealing and closing the well are processed in sequence according to the front and rear furnaces. The specific processing duration is determined according to the actual situation. It is impossible to closely follow up between the front and rear furnaces. The cooling duration of the combustion-empty area of the front and rear furnaces may be different, and the CO2 displacement operation and the CO2 sealing and closing of the front and rear furnaces can also be processed together.

[0058] After the combustion gasification and synthesis gas collection in the gasification area to be mined of Furnace II are completed, the gasification area to be mined of Furnace II becomes a combustion-empty area. The bottom of the gas outlet well of Furnace III is horizontally extended to the bottom of the gas inlet well and connected to each other. The Furnace I after cooling is blocked, sealed with high-pressure CO2, and the well is closed. Furnace I undergoes the process of injection pressure fracturing, combustion gasification, and sealing and closing the well through steps S1 to S3. Similarly, Furnace II, Furnace III... all follow the process of injection pressure fracturing, combustion gasification, and sealing and closing the well. The above process includes one process node of injection pressure fracturing, combustion gasification, and sealing and closing the well. The front and rear furnaces are staggered by one process node (that is, the front and rear furnaces differ by one process node) for follow-up operations. If the three process nodes are respectively sorted as the first, second, and first process nodes, then if the latter furnace is in the second process node and the former furnace is in the first process node, and so on, following in sequence to realize the three process node operations of all furnaces. Each furnace follows the process of injection pressure fracturing, combustion gasification, and sealing and closing the well.

[0059] In some embodiments, all furnaces complete the process according to the gas outlet well of the previous furnace as the gas inlet well of the next furnace in sequence. All furnaces in the coal mining area follow in a straight line or in an S-shaped manner according to the furnace order. Taking straight-line mining as an example, multiple continuous mining straight-line advancement paths can be designed and planned, and multiple staggered node follow-up mining methods are carried out simultaneously, enhancing the gasification efficiency and ensuring the orderly succession of multiple process nodes. The mining is fast, the production is fast, the total mining output is increased, and the mining efficiency is greatly improved.

[0060] Embodiment 2

[0061] As Figures 1 to 5As shown, a method for underground coal combustion gasification and carbon dioxide sequestration mining treatment includes:

[0062] S1. Injection pressure fracturing: Construct the intake well and the outlet well of the furnace. The bottom of the outlet well extends horizontally to the bottom of the intake well and is not connected (see Figure 1 , during the injection pressure fracturing stage, the horizontally extended horizontal fracturing injection channel at the bottom of the outlet well is not connected to the bottom of the intake well. Specifically, see Figure 1 . The unconnected position at the connection is indicated by a dotted line in Figure 3 ). Inject fracturing gas through the outlet well to perform injection pressure fracturing on the gasification area to be mined in the furnace and form a fracture network 19 in the corresponding coal seam of the gasification area to be mined (the fracture network 19 improves the subsequent combustion gasification efficiency). The horizontally extended horizontal fracturing injection channel at the bottom of the outlet well of the present invention can increase the distance between the intake well and the outlet well, and can complete the injection pressure fracturing operation within a large distance between the intake well and the outlet well, greatly reducing the number of construction wells in the entire coal mining area, effectively reducing the impact on the coal rock formation, and improving the safety performance of underground combustion gasification. At the same time, using the horizontal fracturing injection channel to perform injection pressure fracturing treatment on the gasification area to be mined in the furnace from the bottom can greatly improve the injection pressure fracturing efficiency, and further improve the subsequent combustion gasification efficiency. After the injection pressure fracturing is completed, the part of the horizontally extended horizontal fracturing injection channel at the bottom of the outlet well is connected to the bottom of the intake well (after the injection pressure fracturing is completed, the horizontally extended horizontal fracturing injection channel at the bottom of the outlet well is connected to the bottom of the intake well. See

[0063] ). The connected position is indicated by a solid line in Figure 3 ).

[0064] S2. Combustion gasification: Take the bottom end of the intake well of the furnace to the bottom end of the outlet well as the mining direction (take Figure 3 as an example, the mining direction is from right to left). Pass the gasifying agent through the intake well to perform coal seam combustion gasification operation on the gasification area to be mined in the furnace and discharge and collect the syngas through the outlet well of the furnace (the coal seam combustion gasification operation generates syngas containing combustible gas, which is discharged through the outlet well and collected at the end of the outlet well, and then the syngas is separated and processed to finally obtain the required combustible gas). Separate the combustible gas from the syngas. After the gasification area to be mined in the furnace is burned and gasified, a burned-out area is formed, and the burned-out area in the furnace is cooled.

[0064] S3. Sealing the closed well: After the combustion-empty area of the furnace has cooled down (the cooling of the combustion-empty area of the furnace also includes the following detection method: A temperature sensor 23 for monitoring the temperature of the combustion-empty area is provided in the intake well of the furnace. When the temperature sensor 23 drops to the ambient temperature, the idle cooling of the combustion-empty area of the furnace is completed), the outlet well, the combustion-empty area, and the intake well of the furnace form a space to be sealed. Inject a mixed gas with carbon dioxide as the displacement gas into the space to be sealed through the intake well and collect the mixed gas through the outlet well, and separate the combustible gas from the mixed gas. Detect the mixed gas at the outlet well. When the proportion of the displacement gas (carbon dioxide as the displacement gas) detected in the mixed gas reaches P%, stop the displacement operation. Then block one end of the space to be sealed close to the outlet well, and inject high-pressure CO2 gas into the space to be sealed through the intake well (coal burns and gasifies into cinder, and the cinder remains in the combustion-empty area. In order to protect the combustion-empty area, high-pressure CO2 gas needs to be injected for sealing protection). Then seal the cement plug at one end of the space to be sealed close to the intake well and install a leakage detection device for leakage monitoring and alarm (the leakage detection device monitors whether there is gas discharge in the mined underground. If there is gas discharge, it means there is a leakage in the seal, and further measures need to be taken). The method of injecting high-pressure CO2 gas for sealing is as follows:

[0065] Seal one end of the outlet channel (including the combustion-empty area) between the intake well and the outlet well of the furnace with a cement stone plugging block 21 (in this embodiment, a grouting pipeline 20 is provided for the construction of the cement stone plugging block 21). Then inject high-pressure CO2 gas into the outlet channel and the combustion cavity of the furnace for sealing. Then seal the cement plug 24 at the other end of the outlet channel (in this embodiment, a grouting pipeline 20 is provided for the construction of the cement plug 24). Finally, install a leakage detection device 25 at the wellhead of the intake well or / and the outlet well for leakage monitoring and alarm.

[0066] In order to better achieve the supply of carbon dioxide for injection fracturing, the supply of gasifying agent ratio for combustion gasification, and the collection and separation of synthesis gas from combustion gasification, the present invention includes a combined supply and treatment system (the combined supply and treatment system is arranged on the ground in the underground gasification mining area of coal; preferably, a movable system can be constructed to move along with the mining progress). The combined supply and treatment system includes a synthesis gas separation system 7, a high-pressure carbon dioxide supply system, and a gasifying agent supply system. The high-pressure carbon dioxide supply system includes a CO2 gas storage tank 5 and a high-pressure carbon dioxide control and compression unit 6 connected to the CO2 gas storage tank 5. The high-pressure carbon dioxide control and compression unit 6 generates high-pressure CO2 and is used as the fracturing gas for injection fracturing. The gasifying agent supply system includes a steam generation device 2, an oxygen generation device 3, a gasifying agent control station 1, and an injection high-pressure pump group 4. The steam generation device 2 is used to produce steam, the oxygen generation device 3 is used to produce oxygen. The gasifying agent control station 1 is respectively connected to the steam generation device 2 and the oxygen generation device 3, and mixes and proportions steam and oxygen as the main components to form a gasifying agent and transports it to the injection high-pressure pump group 4. The injection high-pressure pump group 4 is used to generate high-pressure gasifying agent and input it into the gasification area to be mined in the furnace for coal seam combustion gasification. The gas separation system 7 is used to collect the synthesis gas generated by coal seam combustion gasification and / or the mixed gas discharged from the displacement operation and separate to obtain combustible gas. The combined supply and treatment system of the present invention can move along with the mining progress path of underground gasification in the furnace. The combined supply and treatment system includes a synthesis gas separation system, a high-pressure carbon dioxide supply system, and a gasifying agent supply system. The synthesis gas separation system realizes the separation and treatment of combustible gas, CO2, and steam in the synthesis gas collected during mining. Among them, CO2 and steam can be recycled. The high-pressure carbon dioxide supply system supplies the carbon dioxide required in the injection fracturing stage and the CO2 sequestration and well closure treatment stage of the present invention. The gasifying agent supply system can supply the gasifying agent with the required ratio (mainly oxygen and steam, with a small amount of substances such as CO2 added) according to the sampled rock formation to the gasification area to be mined for combustion gasification operations.

[0067] In some embodiments, a gasifying agent injection pipe 41 is connected and communicated at the outlet end of the injection high-pressure pump group 4, a gas collection pipe 71 is connected and communicated at the inlet end of the synthesis gas separation system 7, and a fracturing injection pipe 61 is connected and communicated at the outlet end of the high-pressure carbon dioxide control and compression unit 6. During the injection fracturing stage of step S1, the fracturing injection pipe 61 is hermetically connected to the outlet well of the furnace or the fracturing injection pipe 61 is extended into the horizontal fracturing injection gas channel part of the outlet well of the furnace to perform injection fracturing operations on the upper gasification area to be mined. A gas sensor 18 is arranged at the wellhead of the inlet well of the furnace to detect whether there is any outlet of fracturing gas.

[0068] In some embodiments, during the combustion gasification stage of step S2, the gas sensor 18 in the intake well of the furnace is removed, and the gasifier injection pipe 41 is hermetically connected to the intake well of the furnace or the gasifier injection pipe 41 extends into the horizontal fracturing injection gas channel part of the furnace and advances along the mining direction. The gas extraction pipe 71 is hermetically connected to the outlet well of the furnace. The synthesis gas generated by combustion gasification in the gasification area to be mined of the furnace enters the synthesis gas separation system 7 through the gas extraction pipe 71 and combustible gas is separated therefrom.

[0069] In some embodiments, the gas separation system 7 is further connected to a user and storage terminal 8, and the combustible gas separated by the gas separation system 7 is transported to the user and storage terminal 8. The gas separation system 7 is respectively connected to the CO2 storage tank 5 and the gasifier control station 1. The CO2 gas separated by the gas separation system 7 is respectively transported to the CO2 storage tank 5 and the gasifier control station 1. The gasifier control station 1 further adds the CO2 gas as a new gasifier in the corresponding ratio of the gasifier mainly composed of water vapor and oxygen. Sampling and research are carried out on the gasification area to be mined of the furnace. Some coal rock layers are proportioned with the corresponding gasifier with water vapor and oxygen as the main components, and some coal rock layers also need to proportion an appropriate amount of CO2 gas in the gasifier. Therefore, the gas separation system 7 can supply a part of CO2 gas to the gasifier control station 1. Specifically, if the gasifier control station 1 needs CO2 gas in the proportioning, a part of CO2 gas is metered and input. The CO2 gas separated by the gas separation system 7 is respectively transported to the CO2 storage tank 5, and the carbon dioxide gas in the CO2 storage tank 5 can be supplemented, so that the carbon dioxide gas generated in the combustion-empty area is circularly supplemented into the CO2 storage tank 5 and used for injection fracturing (injection fracturing uses high-pressure CO2 injection for fracturing), sealed well treatment (sealed well treatment also uses high-pressure CO2 injection and realizes displacement and sealing), etc. During the gas displacement of the space to be sealed in the sealed well stage of step S3, the fracturing injection pipe 61 is connected to the intake well of the furnace or the fracturing injection pipe 61 extends to the bottom of the intake well of the furnace (preferably, the gasifier control station 1 of the present invention can proportion a gas containing only CO2 gas and form high-pressure CO2 gas through pressurization by the injection high-pressure pump group 4, and then directly use the gasifier injection pipe 41 for gas displacement), the gas extraction pipe 71 is hermetically connected to the outlet well of the furnace, and the mixed gas displaced from the space to be sealed of the furnace enters the synthesis gas separation system 7 through the gas extraction pipe 71 and combustible gas is separated therefrom. The gasifier control station 1 of the present invention can proportion only CO2 gas and only output high-pressure CO2 gas through the injection high-pressure pump group 4 and the gasifier injection pipe 41. Therefore, during the gas displacement of the space to be sealed in the sealed well stage of step S3, the gasifier control station 1 proportions only CO2 gas and injects high-pressure CO2 gas through the gasifier injection pipe 41, the gas extraction pipe 71 is hermetically connected to the outlet well of the furnace, and the mixed gas displaced from the space to be sealed of the furnace enters the synthesis gas separation system 7 through the gas extraction pipe 71 and combustible gas is separated therefrom.

[0070] In some embodiments, before injecting gas and fracturing the gasification extraction area of the furnace, refer to Figure 1 , Figure 6 , first use a packer 17 to perform a sealing operation during the gas injection and fracturing stage at the bottom of the gas outlet well of the furnace. The front section of the gas injection and fracturing pipe 61 is a gas injection distribution pipe 9. The gas injection distribution pipe 9 is in the horizontal gas injection and fracturing channel part and is connected with a number of shunt nozzles 16 (gas injection control valves 15 are installed on each shunt nozzle 16). Each shunt nozzle 16 is arranged at the bottom of the gasification extraction area of the furnace. High-pressure CO2 is injected into the coal seam inside the gasification extraction area through each shunt nozzle 16 of the gas injection distribution pipe 9 to form a fracture network in the coal seam.

[0071] In some embodiments, the gas inlet well and / or the gas outlet well of the furnace are constructed by drilling tools. The bottom of the gas outlet well of the furnace is horizontally extended by using a drilling tool equipped with a bit guidance system for horizontal extension construction. The gas inlet well and the gas outlet well of the furnace are both reinforced and protected by a casing 10 during the working stage. Preferably, the drilling tool equipped with a bit guidance system in this embodiment includes a bit 11, a bent screw power drill 13 installed at the rear end of the bit 11 to drive the bit 11, and a downhole tractor 14 for the horizontal traction power of the horizontal gas injection and fracturing channel for the horizontal extension construction of the bit 11. The bit guidance system includes a bit guidance tool 12 installed in cooperation with the bit 11 for bit steering or guidance.

[0072] Furthermore, the present invention can realize continuous follow-up operations for all furnaces according to a process-based technology. The specific method is as follows:

[0073] Select a coal mining area, plan the furnaces for continuous advancement operations in the coal mining area and sequentially number them as furnace one, furnace two, furnace three,..., furnace N according to the order of the furnaces. Each furnace follows a process-based technology with three process nodes: gas injection and fracturing, combustion and gasification, and sealing and closing the well.

[0074] When in or after the gas injection and fracturing stage of furnace one, follow up and construct the gas outlet well of furnace two. When furnace one is in the combustion and gasification process, inject gas and fracture the gasification extraction area of furnace two through the gas outlet well of furnace two. When furnace one has completed combustion and gasification, use the gas outlet well of furnace one as the gas inlet well of furnace two, follow up and ignite and vaporize furnace two, and at the same time follow up and construct the gas outlet well of furnace three. When furnace one has cooled down and entered the sealing and closing well stage, block the gas outlet channel at one end of furnace one close to the gas outlet well. When furnace two has completed combustion and gasification, use the gas outlet well of furnace two as the gas inlet well of furnace three, follow up and perform gas injection and fracturing on furnace three, and at the same time follow up and construct the gas outlet well of furnace four. Furnace two transfers to the sealing and closing well stage. The process-based technology of the three process nodes of gas injection and fracturing, combustion and gasification, and sealing and closing the well for subsequent furnaces is realized in sequence according to the above method.

[0075] In some embodiments, all furnaces complete the flow process in sequence with the gas outlet well of the previous furnace serving as the gas inlet well of the next furnace. All furnaces in the coal mining area follow continuously in a straight line or in an S shape according to the furnace sequence; taking straight-line mining as an example, multiple continuous mining straight-line advancement paths can be designed and planned, and multiple offset node follow-up mining methods are carried out synchronously, enhancing the gasification efficiency and ensuring the orderly succession of multiple process nodes, with fast mining and quick commissioning, increasing the total mining output and greatly improving the mining efficiency.

[0076] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for underground coal combustion gasification and carbon dioxide storage mining and processing, characterized by: The methods include: S1. Gas injection fracturing: A combined supply and processing system is used, the combined supply and processing system includes a synthesis gas separation system (7), a high-pressure carbon dioxide supply system and a gasification agent supply system, the high-pressure carbon dioxide supply system includes a CO2 gas storage tank (5) and a high-pressure carbon dioxide control and compressor unit (6) connected to the CO2 gas storage tank (5), the high-pressure carbon dioxide control and compressor unit (6) generates high-pressure CO2 and is used as fracturing gas for gas injection fracturing; an inlet well and an outlet well of the construction furnace are constructed, the bottom of the outlet well horizontally extends to the bottom of the inlet well and is not connected, and fracturing gas is introduced through the outlet well to perform gas injection fracturing on the gasification mining area of ​​the furnace and form a fracturing network corresponding to the coal seam in the gasification mining area. After the gas injection fracturing is completed, the bottom of the outlet well is horizontally extended to form a horizontal fracturing gas injection channel part and is interconnected with the bottom of the inlet well; the outlet end of the high-pressure carbon dioxide control and compressor unit (6) is connected to a A fracturing gas injection pipe (61), before gas injection fracturing in the gasification mining area of ​​the furnace, a packer is first used to perform a gas injection fracturing operation on the bottom of the furnace's gas outlet well. The front section of the fracturing gas injection pipe (61) is a gas injection distribution pipe (9). The gas injection distribution pipe (9) is placed in a horizontal fracturing gas injection channel and connected to a plurality of diverter nozzles (16). Each diverter nozzle (16) is distributed at the bottom of the gasification mining area of ​​the furnace. Each diverter nozzle (16) of the gas injection distribution pipe (9) injects high-pressure CO2 into the coal seam inside the gasification mining area to form a fracturing network in the coal seam. During the gas injection fracturing stage, the fracturing gas injection pipe (61) is sealed and connected to the furnace's gas outlet well or the fracturing gas injection pipe (61) is extended to the horizontal fracturing gas injection channel of the furnace's gas outlet well and a gas injection fracturing operation is performed on the gasification mining area above. A gas sensor (18) is provided at the wellhead of the furnace's gas inlet well to detect whether there is gas outlet of fracturing gas. S2, combustion and gasification: with the bottom of the furnace's air inlet well to the bottom of the air outlet well as the mining direction, a gasifying agent is introduced through the air inlet well to perform coal seam combustion and gasification operations on the furnace's gasification mining area, and synthetic gas is discharged and collected through the furnace's air outlet well, and combustible gas is separated from the synthetic gas; after the combustion and gasification of the furnace's gasification mining area is completed, a combustion-free zone is formed, and the combustion-free zone of the furnace is cooled; during the combustion and gasification stage, the gas sensor (18) of the furnace's air inlet well is removed, and the gasifying agent injection pipe (41) is sealed and connected to the furnace's air inlet well, or the gasifying agent injection pipe (41) is extended to the furnace's horizontal fracturing injection channel to follow the mining direction; S3. Sealing and closing the well: After the combustion-free zone of the furnace has been cooled down, the gas outlet well, the combustion-free zone and the gas inlet well of the furnace form a space to be sealed. Carbon dioxide is injected into the space to be sealed through the gas inlet well as a displacement gas, and the mixed gas is collected through the gas outlet well to separate the combustible gas from the mixed gas. The mixed gas is tested at the gas outlet well, and when the proportion of the displacement gas in the mixed gas reaches P%, the displacement operation is stopped. Then, the end of the space to be sealed close to the gas outlet well is blocked, and high-pressure CO2 gas is injected into the space to be sealed through the gas inlet well to seal it. Then, a cement plug is closed at the end of the space to be sealed close to the gas inlet well, and a leakage detection device is installed to monitor and alarm for leakage.

2. The underground coal combustion gasification and carbon dioxide storage mining and processing method according to claim 1 is characterized by: The gasifying agent supply system comprises a water vapor generator (2), an oxygen generator (3), a gasifying agent control station (1) and a gas injection high-pressure pump group (4). The water vapor generator (2) is used to produce water vapor, and the oxygen generator (3) is used to produce oxygen. The gasifying agent control station (1) is connected to the water vapor generator (2) and the oxygen generator (3) respectively and uses water vapor and oxygen as the main materials to mix and proportion the gasifying agent and transport it to the gas injection high-pressure pump group (4). The gas injection high-pressure pump group (4) is used to generate high-pressure gasifying agent and input it into the gasification area of ​​the furnace for coal seam combustion gasification. The synthesis gas separation system (7) is used to collect the synthesis gas generated by coal seam combustion gasification and / or the mixed gas discharged by the displacement operation and separate them to obtain combustible gas.

3. The underground coal combustion gasification and carbon dioxide storage mining and processing method according to claim 2 is characterized by: The gas outlet end of the gas injection high-pressure pump group (4) is connected to a gasification agent gas injection pipe (41), and the gas inlet end of the synthesis gas separation system (7) is connected to a gas collection pipe (71); During the combustion and gasification stage of step S2, the gas production pipe (71) is connected to the gas outlet well of the furnace in a sealed manner, and the synthesis gas generated by combustion and gasification in the gasification waiting area of ​​the furnace enters the synthesis gas separation system (7) through the gas production pipe (71) and is separated to obtain combustible gas.

4. The underground coal combustion gasification and carbon dioxide storage mining and processing method according to claim 2 is characterized by: The synthesis gas separation system (7) is also connected to a user and a storage end (8), and the combustible gas separated by the synthesis gas separation system (7) is transported to the user and the storage end (8); the synthesis gas separation system (7) is respectively connected to a CO2 gas storage tank (5) and a gasification agent control station (1), and the CO2 gas separated by the synthesis gas separation system (7) is respectively transported to the CO2 gas storage tank (5) and the gasification agent control station (1), and the gasification agent control station (1) also adds CO2 gas as a new gasification agent in a corresponding proportion to a gasification agent mainly composed of water vapor and oxygen; During the gas displacement of the space to be sealed in the sealing and closing stage of step S3, the gasification agent control station (1) only mixes CO2 gas and injects high-pressure CO2 gas through the gasification agent injection pipe (41), and the gas production pipe (71) is tightly connected to the gas outlet well of the furnace. The mixed gas displaced from the space to be sealed in the furnace enters the synthesis gas separation system (7) through the gas production pipe (71) and is separated to obtain combustible gas.

5. The underground coal combustion gasification and carbon dioxide storage mining and processing method according to claim 1 is characterized by: The furnace's air inlet well and / or air outlet well are constructed using drilling tools, and the bottom of the furnace's air outlet well is horizontally extended using a drilling tool equipped with a drill bit guide system. The furnace's air inlet well and air outlet well are both reinforced and protected by casing (10) during the working stage.

6. The underground coal combustion gasification and carbon dioxide storage mining and processing method according to claim 5 is characterized by: The drilling tool equipped with a drill bit guide system comprises a drill bit (11), a bent screw power drill (13) installed at the rear end of the drill bit (11) and used to drive the drill bit (11) with power, and a horizontal fracturing gas injection channel downhole tractor (14) used to provide traction power for horizontal extension construction of the drill bit (11). The drill bit guide system comprises a drill bit guide tool (12) installed in cooperation with the drill bit (11) and used to steer or guide the drill bit.

7. The underground coal combustion gasification and carbon dioxide storage mining and processing method according to claim 1 is characterized by: The furnace combustion zone cooling also includes the following detection method: a temperature sensor (23) for monitoring the combustion zone temperature is arranged in the furnace air intake shaft; when the temperature sensor (23) is lowered to the ambient temperature, the furnace combustion zone idle cooling is completed.

8. The underground coal combustion gasification and carbon dioxide storage mining and processing method according to any one of claims 1 to 7, characterized in that: Also includes the following methods: Select a coal mining area, plan the furnaces for continuous advancement of the coal mining area, and number them in order of furnace 1, furnace 2, furnace 3, ..., furnace N. Each furnace is processed according to the three process nodes of gas injection fracturing, combustion gasification, and sealing and closing the well; When the gas injection and fracturing stage of furnace one is in progress or completed, the gas outlet well of furnace two is followed up; when furnace one is in the process of combustion and gasification, the gasification waiting area of ​​furnace two is subjected to gas injection and fracturing through the gas outlet well of furnace two; when the combustion and gasification of furnace one is completed, the gas outlet well of furnace one is used as the gas inlet well of furnace two, and the ignition and gasification of furnace two is followed up, and at the same time, the gas outlet well of furnace three is followed up; when furnace one is cooled down and enters the sealing and well closing stage, the gas outlet channel of furnace one near one end of the gas outlet well is blocked; when the combustion and gasification of furnace two is completed, the gas outlet well of furnace two is used as the gas inlet well of furnace three, and the gas injection and fracturing of furnace three is followed up, and at the same time, the gas outlet well of furnace four is followed up, and furnace two enters the sealing and well closing stage; According to the above method, the process technology of the three process nodes of gas injection fracturing, combustion gasification and sealing and closing of the well in the subsequent furnace is realized in sequence.

9. The underground coal combustion gasification and carbon dioxide storage mining and processing method according to claim 8, characterized in that: All furnaces complete the process technology in sequence with the outlet well of the previous furnace serving as the inlet well of the next furnace; all furnaces in the coal mining area follow up continuously in a straight line or in an S-shaped manner according to the furnace sequence.

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