Continuous coordinated advancement method of common wells before and after underground coal gasification mining

Abstract

The present invention discloses a method for continuous coordinated advancement of the common wells of the front and rear furnaces of underground coal gasification mining, the method comprising: S1, constructing the gas inlet and outlet wells of furnace No. 1, and using the outlet well to perform gas injection and fracturing on the gasification mining area of ​​furnace No. 1; S2, performing coal seam combustion and gasification operations on the gasification mining area of ​​furnace No. 1 and collecting synthesis gas through the outlet well of furnace No. 1; and simultaneously using the outlet well of furnace No. 2 to perform gas injection and fracturing on the gasification mining area of ​​furnace No. 2; S3, allowing the combustion and gasification area of ​​furnace No. 1 to be idle and cooled, while furnace No. 2 performs combustion and gasification operations and furnace No. 3 performs gas injection and fracturing operations; each furnace undergoes a process-based process of gas injection and fracturing, combustion and gasification, idle cooling, and CO2 storage and well closure; and S4, completing each process-based process in sequence. The present invention performs differential node follow-up according to the process-based process, with a difference of one process node between the upper and lower furnaces, and the upper and lower furnaces perform common wells, thereby reducing the number of drilling wells, alleviating geological damage, and improving mining efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of underground coal gasification, and in particular to a method for continuously coordinating the advancement of a common well of a front and rear furnace of underground coal gasification mining. Background Art

[0002] Underground coal gasification (UCG) is the process of directly converting underground coal resources into coal gas. It efficiently converts underground coal resources into usable energy, improving coal mining efficiency and reducing mining costs. Deep UCG development requires extensive geological surveys and exploration to ensure the stability of boreholes within the rock formations. UCG also faces numerous challenges, including the complexity of geological conditions, combustion control during the gasification process, environmental pollution, and technical difficulties, all of which require further resolution. Because underground coal is located underground and distributed in flat, stratified layers, layer-by-layer combustion gasification is prone to collapse. Preemptive fracturing of the coal seams is ideal to reduce the probability of major combustion gasification accidents. UCG often involves drilling a well and fracturing the coal seams from the side. This limited area of ​​fracturing requires intensive drilling, which increases the workload, impacts the geological environment, and complicates post-mining disposal of the burnout zone and the mine. Underground coal gasification not only involves combustion gasification (which typically requires two mines: one to input the gasifying agent and the other to output syngas containing combustible gases), but also involves cooling the combustion void and post-mining protection measures. The process is tightly coupled. Current technology involves completing underground gasification at one combustion gasification site (including two mines) before conducting subsequent underground gasification at a nearby site. To increase combustible gas production, multiple combustion gasification sites must be established for simultaneous gasification. This significantly increases the number of mines, making construction and post-mining disposal more difficult (and resulting in wasted manpower, material resources, and time), and also causes greater damage to the geological environment (due to multiple drilling holes in the rock formation, which compromises the containment and stability of the combustion void cavity). This, in turn, increases the risks of underground coal gasification operations. Therefore, many technical challenges remain in underground coal gasification, representing areas that urgently require research for the application and promotion of underground coal gasification technology. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for continuous coordinated advancement of the common wells of the front and rear furnaces of underground coal gasification mining. The underground gasification mining of each furnace is carried out process-by-process according to the process-based technology of gas injection fracturing, combustion gasification, idle cooling, and CO2 storage and well closure treatment. The upper and lower furnaces are followed up at the difference node according to the process-based technology with a difference of one process node; the gas outlet well of the upper furnace after gas injection fracturing is used as the gas inlet well of the next furnace, thus forming a shared gas inlet and outlet directional well. Therefore, the continuous coordinated advancement method of the present invention can realize the common wells of the upper and lower furnaces, reduce the number of drilling wells and drilling workload, and at the same time reduce the degree of geological damage to the coal strata and reduce the difficulty of sealing the wells and the combustion void area.

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

[0005] A method for continuous coordinated advancement of a common well for front and rear furnaces of underground coal gasification mining, the method comprising:

[0006] S1. Construct the inlet and outlet wells of Furnace No. 1. The bottom of the outlet well is horizontally extended to the bottom of the inlet well without being connected. The outlet well is used to perform gas injection fracturing on the gasification area to be mined of Furnace No. 1. After the gas injection fracturing is completed, the bottom of the outlet well is horizontally extended to the bottom of the inlet well and connected to each other.

[0007] S2. A proportioned gasifying agent is introduced into the bottom of the inlet well of the No. 1 furnace, and coal seam combustion and gasification operations are carried out in the gasification area to be mined in the No. 1 furnace from the bottom of the inlet well toward the bottom of the outlet well. Synthesis gas is collected through the outlet well of the No. 1 furnace. Simultaneously, the outlet well of the No. 2 furnace is constructed. The bottom of the outlet well of the No. 2 furnace extends horizontally to the bottom of the outlet well of the No. 1 furnace without being connected. Gas injection and fracturing are carried out in the gasification area to be mined in the No. 2 furnace using the outlet well of the No. 2 furnace.

[0008] When the combustion and gasification of the gasification mining area of ​​the No. 1 furnace and the collection of synthesis gas are completed, the bottom of the outlet well of the No. 2 furnace is horizontally extended to the bottom of the inlet well and connected to each other, and the gasification mining area of ​​the No. 1 furnace becomes a combustion air zone;

[0009] S3. Allow the combustion zone of the No. 1 furnace to be idle and cooled; use the outlet well of the No. 1 furnace as the inlet well of the No. 2 furnace, introduce a proportioned gasifying agent into the bottom of the inlet well of the No. 2 furnace, and perform coal seam combustion gasification operations on the gasification and mining area of ​​the No. 2 furnace from the bottom of the inlet well of the No. 2 furnace toward the bottom of the outlet well of the No. 2 furnace, and collect synthesis gas through the outlet well of the No. 2 furnace; at the same time, construct the outlet well of the No. 3 furnace, and the bottom of the outlet well of the No. 3 furnace extends horizontally to the bottom of the outlet well of the No. 2 furnace without being connected, and use the outlet well of the No. 3 furnace to perform gas injection and fracturing on the gasification and mining area of ​​the No. 3 furnace;

[0010] After the combustion and gasification of the gasification mining area of ​​the No. 2 furnace and the collection of synthesis gas are completed, the gasification mining area of ​​the No. 2 furnace becomes a combustion-free area, and the bottom of the outlet well of the No. 3 furnace is horizontally extended to the bottom of the inlet well and connected to each other; the No. 1 furnace after cooling is sealed, high-pressure 0O2 is sealed and the well is closed. The No. 1 furnace undergoes the process of gas injection fracturing, combustion and gasification, idle cooling, CO2 sealing and well closing treatment in steps S1 to S3;

[0011] S4. Construct the gas outlet wells of the No. 4 furnace and subsequent furnaces according to the method of constructing the gas outlet well of the No. 2 furnace in step S2, and complete the process technology of the No. 2 furnace and subsequent furnaces in sequence according to steps S1 to S3.

[0012] In order to better realize the present invention, the gas outlet well of the No. 4 furnace is constructed and gas injection and fracturing are carried out in the gasification area to be mined, while combustion and gasification of the gasification area to be mined of the No. 3 furnace are followed up; the combustion and empty area of ​​the No. 2 furnace is idle for cooling and CO2 is sealed and closed.

[0013] Preferably, the gas inlet wells and / or gas outlet wells of all furnaces are constructed using drilling tools, and the horizontal extension of the bottom of the gas outlet wells of all furnaces is constructed using drilling tools equipped with a drill bit guidance system; before gas injection fracturing in the gasification mining area of ​​all furnaces, the bottom of the gas outlet well of the furnace needs to be sealed with a packer during the gas injection fracturing stage. Gas injection fracturing injects high-pressure CO2 into the coal seam inside the gasification mining area through several diversion nozzles distributed at the bottom of the gasification mining area of ​​the furnace, and forms a fracture network in the coal seam.

[0014] Preferably, during the gas injection and fracturing stage of the furnace, a gas sensor is installed at the wellhead of the corresponding gas inlet well of the furnace. When the gas sensor detects that CO2 is stably discharged through the fracture network and the gas inlet well of the gasification mining area, the fracture network of the coal seam inside the gasification mining area is good and the gas injection and fracturing is completed.

[0015] Preferably, the present invention also includes a coordinated advancement joint processing system, which includes a synthesis gas separation system, a high-pressure carbon dioxide supply system and a gasification agent supply system. The gasification agent supply system includes a water vapor generator, an oxygen generator, a gasification agent control station and a gas injection high-pressure pump group. The water vapor generator is used to produce water vapor, and the oxygen generator is used to produce oxygen. The gasification agent control station is connected to the water vapor generator and the oxygen generator respectively and mainly mixes water vapor and oxygen into a gasification agent and transports it to the gas injection high-pressure pump group. The gas injection high-pressure pump group is used to generate high-pressure gasification agent and input it into the gasification area to be mined for coal seam combustion gasification; the high-pressure carbon dioxide supply system includes a CO2 gas storage tank and a high-pressure carbon dioxide control and compressor group connected to the CO2 gas storage tank. The high-pressure carbon dioxide control and compressor group generates high-pressure CO2 and is used as fracturing gas for gas injection fracturing; the gas separation system is used to collect the mixed gas generated by coal seam combustion gasification and separate it to obtain combustible gas.

[0016] Preferably, the gas separation system is also connected to a use and storage end, and the combustible gas separated by the gas separation system is transported to the use and storage end; the gas separation system is respectively connected to a CO2 gas storage tank and a gasification agent control station, and the CO2 gas separated by the gas separation system is respectively transported to a CO2 gas storage tank and a gasification agent control station, and the gasification agent control station also adds CO2 gas as a new gasification agent in a corresponding ratio to the gasification agent mainly composed of water vapor and oxygen.

[0017] Preferably, the bottom of the gas outlet well of all furnaces is horizontally extended using a drilling tool equipped with a drill bit guidance system to carry out horizontal extension construction and form a horizontal well. The drilling tool includes a drill bit and a bent screw power drill installed at the rear end of the drill bit to drive the drill bit, and a horizontal well downhole tractor to serve as traction power for the horizontal extension construction of the drill bit. The drill bit guidance system includes a drill bit guidance tool installed on the drill bit to steer or guide the drill bit.

[0018] Preferably, the drilling tool is also combined with a gas injection fracturing pipe, on which a number of diversion nozzles are opened toward the corresponding furnace gasification area to be mined, and each diversion nozzle is installed with a gas injection control valve; a packer is installed on the gas injection fracturing pipe; the gas inlet wells and / or gas outlet wells of all furnaces are reinforced and protected by casing during the working stage.

[0019] Preferably, the plugging, high-pressure CO2 storage and well closure treatment methods are as follows:

[0020] After the cooling is completed, one end of the gas outlet channel between the gas inlet well and the gas outlet well of the furnace is sealed with a cement stone sealing block; then high-pressure CO2 gas is injected into the gas outlet channel and the combustion cavity of the furnace for sealing; then the cement plug is sealed at the other end of the gas outlet channel; finally, a leakage detection device is installed at the wellhead of the gas inlet well and / or the gas outlet well for leakage monitoring and alarm.

[0021] Preferably, the idle cooling detection method of the furnace's combustion zone is as follows: a temperature sensor for monitoring the combustion zone temperature is provided in the furnace's air inlet shaft; when the temperature sensor drops to ambient temperature, the idle cooling of the furnace's combustion zone is completed.

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

[0023] (1) In the present invention, each furnace for underground gasification mining is carried out in accordance with the process-based process of gas injection and fracturing, combustion gasification, idle cooling, and CO2 storage and well closure treatment, and the upper and lower furnaces are followed up at different nodes according to the process-based process with a difference of one process node; the outlet well of the upper furnace after gas injection and fracturing serves as the inlet well of the next furnace, thus forming a shared inlet and outlet directional well. Therefore, the continuous coordinated advancement method of the present invention can realize the common use of the upper and lower furnace wells, reduce the number of drilling wells and drilling workload, and at the same time reduce the degree of geological damage to the coal strata, and reduce the difficulty of sealing the wells and the combustion void area.

[0024] (2) In the present invention, when furnace No. 1 is idle and cooled, furnace No. 2 is followed by combustion and gasification, and furnace No. 3 is followed by gas injection and fracturing. At this time, furnace No. 4 can be followed up, thereby forming differential node follow-up and the front and rear furnaces share the same wells and continuously coordinate the advancement, reducing the construction of some wells, so that the mining efficiency is effectively improved; continuous follow-up mining can be carried out in a straight line, circle or S shape in the coal mining area. Taking straight line mining as an example, multiple continuous mining straight advancement paths can be designed and planned, and multiple differential node follow-up mining methods are carried out simultaneously, which enhances the gasification efficiency and ensures the orderly succession of multiple process nodes, resulting in fast mining and production, and increased total mining output, greatly improving mining efficiency.

[0025] (3) During the gas injection and fracturing, the bottom of the gas outlet well of the furnace is horizontally extended to form a horizontal well. In this way, the gas outlet well has a horizontal well portion, which is not connected to the gas inlet well during the gas injection and fracturing stage. High-pressure CO2 is injected into the horizontal well portion of the gas outlet well through distributed diversion nozzles to perform gas injection and fracturing on the gasification area to be mined corresponding to the furnace above, so that a fracture network is formed in the coal seam, which releases coal stress in advance and improves combustion gasification safety and vaporization efficiency. The high-pressure injection of CO2 can also effectively displace coalbed methane. Since there is a horizontal well portion 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 greater distance, so that the horizontal well portion of the gas outlet well can bear the distributed high-pressure CO2 gas injection and fracturing of the gasification area to be mined. The greater distance between the wells proves that the present invention can reduce drilling costs and promote safe and efficient mining.

[0026] (4) The coordinated advancement of the combined processing system of the present invention can move along the path of underground gasification mining. The coordinated advancement of the combined processing system includes a synthesis gas separation system, a high-pressure carbon dioxide supply system and a gasification agent supply system. The synthesis gas separation system realizes the separation and treatment of combustible gas, CO2 and water vapor collected from the mining of synthesis gas, wherein CO2 and water vapor can be recycled. The high-pressure carbon dioxide supply system supplies the carbon dioxide required for the gas injection and fracturing stage and the CO2 storage and well closure treatment stage of the present invention. The gasification agent supply system can set the required ratio of gasification agent (mainly oxygen and water vapor, with a small amount of CO2 and other substances added) according to the sampled rock formation and supply it to the gasification mining area for combustion and gasification operations.

[0027] (5) The idle cooling and CO2 storage and well closure treatment of the present invention are the subsequent disposal processes of furnace mining, which may not be followed up in the order of the furnaces; the present invention has clear requirements or monitoring when each process node is completed and handed over, such as monitoring the gas outlet of the fracture network through a gas sensor when the gas injection fracturing is completed, and leak monitoring and alarming through a leak detection device installed at the wellhead when the CO2 storage and well closure treatment is completed, both of which ensure the efficiency and safety performance of the mining follow-up work. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the gas injection fracturing principle of an example furnace in the embodiment;

[0029] Figure 2 This is a schematic diagram showing the principle of using a No. 1 furnace for combustion gasification and a No. 2 furnace for gas injection fracturing to share a directional well with the No. 1 furnace as an example in the embodiment;

[0030] Figure 3 This is a structural principle diagram of furnace gas injection fracturing as an example in the embodiments;

[0031] Figure 4 This is a schematic diagram of the CO2 storage and well closure treatment in the furnace combustion cavity, taking the examples in the embodiments as an example;

[0032] Figure 5 This is a simplified schematic diagram of the process of front and rear furnace follow-up in the embodiment.

[0033] The names corresponding to the reference numerals in the accompanying drawings are:

[0034] 1-Gasification agent control station, 2-Water vapor generator, 3-Oxygen generator, 4-Gas injection high-pressure pump group, 5-CO2 gas storage tank, 6-High-pressure carbon dioxide control and compressor group, 7-Synthesis gas separation system, 8-Use and storage end, 9-Gas injection fracturing pipe, 10-Casing, 11-Drill bit, 12-Drill bit guide tool, 13-Bent screw power drilling tool, 14-Horizontal well downhole tractor, 15-Gas injection control valve, 16-Diverter nozzle, 17-Packer, 18-Gas sensor, 19-Fracturing network, 20-Grouting pipeline, 21-Cement stone sealing block, 22-Combustion cavity, 23-Temperature sensor, 24-Cement plug, 25-Leakage detection device. DETAILED DESCRIPTION

[0035] Below in conjunction with embodiment, the present invention is described in further detail:

[0036] Example

[0037] like Figure 1 As shown, a method for continuous coordinated advancement of a common well for front and rear furnaces of underground coal gasification mining comprises:

[0038] S1. Construct the inlet and outlet wells of No. 1 furnace. The bottom of the outlet well extends horizontally to the bottom of the inlet well and is not connected (see Figure 2 、 Figure 3 During the gas injection and fracturing stage, the horizontal well extending horizontally from the bottom of the outlet well is not connected to the inlet well. Figure 3 The connected position in the figure is indicated by a dotted line as not connected), and the gasification waiting area of ​​the No. 1 furnace is subjected to gas injection fracturing using the gas outlet well. After the gas injection fracturing is completed, the bottom of the gas outlet well is horizontally extended to the bottom of the gas inlet well and connected to each other.

[0039] This embodiment takes furnace No. 1 as the initial furnace (the first furnace) as an example. Furnace No. 1 needs to construct an air inlet well and an air outlet well, and subsequent furnaces only need to construct an air outlet well, and the air outlet well of the previous furnace can be used as the air inlet well of the next furnace (the upper and lower furnaces share a directional well, which can be called an air inlet and outlet directional well, which fundamentally reduces the number of drilling wells technically and protects the underground rock structure of the coal).

[0040] Since furnace No. 1 is the first furnace, the gas injection fracturing technology is introduced using furnace No. 1 as an example.

[0041] Gas injection fracturing method: The bottom of the outlet well of No. 1 furnace extends horizontally to the bottom of the inlet well of No. 1 furnace and is not connected (see Figure 1 , horizontal drilling construction is carried out from the bottom of the outlet well of No. 1 furnace and horizontally extended to form a horizontal well. At this time, the end of the extended horizontal well should not be connected to the bottom of the inlet well, so that the outlet well of No. 1 furnace as a whole forms an L-shaped mine, and the L-shaped mine is not connected with the inlet well of No. 1 furnace at this time, and the L-shaped mine is a separate mine). The outlet well of No. 1 furnace is used to perform gas injection and fracturing on the gasification area to be mined of No. 1 furnace (since the L-shaped mine is a separate mine, the gasification area to be mined of No. 1 furnace can be treated with gas injection and fracturing. The gasification area to be mined of No. 1 furnace is Figure 1 The right side of the outlet well), after the gas injection and fracturing is completed, the bottom of the outlet well is horizontally extended to the bottom of the inlet well and connected to each other (they are not connected during the gas injection and fracturing process, and are connected only after the gas injection and fracturing is completed).

[0042] The above is an introduction to the gas injection fracturing method using furnace No. 1 as an example. Furnace No. 2 in the technology of the present invention follows the underground gasification operation of furnace No. 1. After the gas injection fracturing of furnace No. 1 is completed, the outlet well of furnace No. 1 serves as the inlet well of furnace No. 2 (the upper and lower furnaces share a directional well, which can be called an inlet and outlet directional well). Furnace No. 2 then has both an inlet well and an outlet well. Furnace No. 2 also performs gas injection fracturing in the gasification area to be mined of furnace No. 2 according to the above-mentioned gas injection fracturing method. Furnace No. 3 follows the underground gasification operation of furnace No. 2, and furnace No. 3 also adopts the above-mentioned gas injection fracturing method. By analogy, the next furnace follows the previous furnace, and the next furnace performs gas injection fracturing in the corresponding gasification area to be mined according to the above-mentioned gas injection fracturing method.

[0043] In some embodiments, during the gas injection and fracturing stage of the furnace, a gas sensor 18 is installed at the wellhead of the corresponding gas inlet well of the furnace (for example, taking furnace No. 1 as an example, a gas sensor 18 is installed at the wellhead of the gas inlet well of furnace No. 1 to monitor the gas outlet of the fracturing network). When the gas sensor 18 detects that CO2 is stably discharged through the fracturing network and the gas inlet well of the gasification mining area, the fracturing network of the coal seam inside the gasification mining area is good, and the gas injection and fracturing is completed.

[0044] S2. A proportioned gasifying agent is introduced into the bottom of the inlet well of the No. 1 furnace, and coal seam combustion gasification operations are carried out on the gasification mining area of ​​the No. 1 furnace from the bottom of the inlet well toward the bottom of the outlet well, and synthesis gas is collected through the outlet well of the No. 1 furnace. At the same time, the outlet well of the No. 2 furnace is constructed. The bottom of the outlet well of the No. 2 furnace extends horizontally to the bottom of the outlet well of the No. 1 furnace and is not connected. The outlet well of the No. 2 furnace is used to perform gas injection and fracturing on the gasification mining area of ​​the No. 2 furnace. In order to save mining time, the combustion gasification of the No. 1 furnace and the gas injection and fracturing of the No. 2 furnace can be carried out simultaneously. The combustion gasification of the No. 1 furnace uses the inlet and outlet wells of the No. 1 furnace, and the gas injection and fracturing of the No. 2 furnace will use the outlet well of the No. 2 furnace. At this time, the outlet well of the No. 2 furnace is not connected to the outlet well of the No. 1 furnace, and the two do not affect each other. The connection will only be made when the No. 2 furnace is undergoing gas injection and fracturing monitoring (gas injection and fracturing monitoring is the preferred step method) or the combustion and gasification.

[0045] Gas injection fracturing is followed by combustion gasification. Since furnace No. 1 is the first furnace (subsequent furnaces will follow in sequence), the combustion gasification technology method will be introduced using furnace No. 1 as an example.

[0046] Combustion gasification method: A proportioned gasifying agent is introduced into the bottom of the No. 1 furnace's inlet well (at this point, the outlet well and the inlet well are interconnected). Coal seam combustion gasification is then carried out in the gasification area of ​​No. 1 furnace, moving from the bottom of the inlet well toward the bottom of the outlet well. Synthesis gas is then collected through the outlet well. Synthesis gas contains useful combustible gases as well as other substances that require removal (such as water vapor and carbon dioxide). This syngas is subsequently separated by a syngas separation system 7 to obtain combustible gas (generally, the combustible gas is further separated to meet different uses). This gas is then transported to a consumption and storage terminal 8.

[0047] The above description of the combustion gasification method uses Furnace 1 as an example. In the present invention, Furnace 2 follows Furnace 1's underground gasification operations, and Furnace 3 follows Furnace 2's underground gasification operations. While Furnace 1 is performing combustion gasification, Furnace 2 undergoes gas injection fracturing. The bottom of Furnace 2's gas well extends horizontally to the bottom of Furnace 1's gas well (which serves as a backup gas well for Furnace 2), but is not connected. Furnace 2's gas well is used to perform gas injection fracturing in Furnace 2's gasification recovery area. The gas injection fracturing operation in Furnace 2 follows the aforementioned gas injection fracturing method.

[0048] After the combustion and gasification of furnace No. 1 is completed, furnace No. 2 performs combustion and gasification operations according to the above-mentioned combustion and gasification method. After the combustion and gasification of furnace No. 2 is completed, furnace No. 3 then performs combustion and gasification operations according to the above-mentioned combustion and gasification method. Similarly, 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.

[0049] When combustion, gasification, and synthesis gas collection are completed in the gasification mining area of ​​Furnace No. 1, the bottom of the outlet well of Furnace No. 2 is horizontally extended to the bottom of the inlet well and connected to each other, turning the gasification mining area of ​​Furnace No. 1 into a combustion-free zone. "When combustion, gasification, and synthesis gas collection are completed in the gasification mining area of ​​Furnace No. 1, the bottom of the outlet well of Furnace No. 2 is horizontally extended to the bottom of the inlet well and connected to each other" is the condition for Furnace No. 2 to follow Furnace No. 1. That is, when or after the synthesis gas collection operation of Furnace No. 1 is completed, the bottom of the outlet well of Furnace No. 2 is horizontally extended to the bottom of the inlet well of Furnace No. 2 (at this time, the inlet well of Furnace No. 2 and the outlet well of Furnace No. 1 are the same well, called the inlet and outlet directional well) and connected to each other.

[0050] S3. Allow the combustion zone of Furnace No. 1 to cool down. Use the outlet well of Furnace No. 1 as the inlet well for Furnace No. 2. Introduce a proportioned gasifying agent into the bottom of the inlet well of Furnace No. 2. Conduct coal seam combustion and gasification operations on the gasification and mining area of ​​Furnace No. 2 from the bottom of the inlet well toward the bottom of the outlet well of Furnace No. 2, and collect synthesis gas through the outlet well of Furnace No. 2. Simultaneously, construct the outlet well of Furnace No. 3. The bottom of the outlet well of Furnace No. 3 extends horizontally to the bottom of the outlet well of Furnace No. 2 without being connected. Use the outlet well of Furnace No. 3 to perform gas injection and fracturing on the gasification and mining area of ​​Furnace No. 3. When Furnace No. 1 is completed from combustion and gasification or is idle and cooling in the combustion zone, use the outlet well of Furnace No. 1 as the inlet well for Furnace No. 2. Furnace No. 2 is subjected to combustion and gasification according to the above-described combustion and gasification method. Simultaneously, construct the outlet well of Furnace No. 3 and perform gas injection and fracturing on Furnace No. 3.

[0051] The above is based on the example of the idle cooling treatment of the No. 1 furnace entering the combustion and air gap area. The No. 2 furnace in the technology of the present invention follows the underground gasification operation of the No. 1 furnace, and the No. 3 furnace follows the underground gasification operation of the No. 2 furnace. When the No. 1 furnace is idle and cooled, the No. 2 furnace performs combustion gasification, the No. 3 furnace performs gas injection fracturing, and the No. 4 furnace starts construction. After the combustion and gasification of the No. 2 furnace is completed, it follows and enters idle cooling.

[0052] Idle cooling method: After the furnace completes combustion and gasification, the next step is idle cooling, which means letting the furnace idle and cool down naturally. Cooling measures can also be used for rapid cooling.

[0053] After the idle cooling of furnace No. 1 is completed, furnace No. 2 is idle cooled according to the above idle cooling method. After the idle cooling of furnace No. 2 is completed, furnace No. 3 is idle cooled according to the above idle cooling method. And so on. The next furnace follows the previous one and performs the idle cooling operation of the corresponding combustion-storage zone according to the above idle cooling method.

[0054] CO2 sealing and well closure treatment (detailed as sealing, high-pressure CO2 sealing and well closure treatment) method: After the furnace is cooled down, the ventilation channel of the furnace is sealed, high-pressure CO2 is injected into the ventilation channel, the combustion air zone is sealed, and the furnace is closed.

[0055] After the CO2 storage and well closure treatment of furnace No. 1 is completed, furnace No. 2 will carry out CO2 storage and well closure treatment in accordance with the above-mentioned CO2 storage and well closure treatment method. After the CO2 storage and well closure treatment of furnace No. 2 is completed, furnace No. 3 will then carry out CO2 storage and well closure treatment in accordance with the above-mentioned CO2 storage and well closure treatment method. And so on. The next furnace follows the previous one and carries out CO2 sealing and well closure treatment in the corresponding combustion zone in accordance with the above-mentioned CO2 storage and well closure treatment method.

[0056] It should be noted that idle cooling and CO2 storage and well closure treatment are the processes after the furnace has completed gas injection fracturing and combustion gasification operations. Since there is no close operation follow-up process between the front and rear furnaces like gas injection fracturing and combustion gasification, they can be processed in sequence according to the order of the furnaces.

[0057] After combustion and gasification, and syngas collection, are complete in the No. 2 furnace's gasification recovery area, the area becomes a burnout zone. The bottom of the No. 3 furnace's outlet well is horizontally extended to the bottom of the inlet well, connecting them. After cooling, the No. 1 furnace is plugged, high-pressure CO2 is stored, and the well is shut down. The No. 1 furnace undergoes a streamlined process consisting of gas injection fracturing, combustion and gasification, idle cooling, and CO2 storage and well closure. Similarly, furnace No. 2, furnace No. 3, etc. all follow the process-based technology of gas injection and fracturing, combustion and gasification, idle cooling, and CO2 storage and well closure treatment. The above process-based technology includes four process nodes: gas injection and fracturing, combustion and gasification, idle cooling, and CO2 storage and well closure treatment. The two furnaces in front and behind are one process node apart (that is, the two furnaces in front and behind are one process node apart) for follow-up operations. If the four process nodes are sorted as the first, second, third, and fourth process nodes respectively, then if the latter furnace is at the second process node, the former furnace is at the first process node, and so on. The four process node operations of all furnaces are followed up in sequence. Each furnace follows the process-based technology of gas injection and fracturing, combustion and gasification, idle cooling, and CO2 storage and well closure treatment.

[0058] S4. Construct the gas outlet wells of furnace No. 4 and subsequent furnaces according to the method of constructing the gas outlet well of furnace No. 2 in step S2, and complete the process technology of furnace No. 2 and subsequent furnaces in sequence according to steps S1 to S3 (according to the process technology of gas injection fracturing, combustion gasification, idle cooling, CO2 storage and well closure treatment).

[0059] Further explanation: Construction is underway on the outlet well of Furnace No. 4, with gas injection and fracturing in the gasification waiting area. Simultaneously, combustion and gasification are underway in the gasification waiting area of ​​Furnace No. 3. The combustion-free area of ​​Furnace No. 2 is undergoing idle cooling and CO2 storage and well closure. These processes are not necessarily performed in the exact order in which the furnaces are installed (although idle cooling must occur first, followed by CO2 storage and well closure).

[0060] In some embodiments, the inlet and / or outlet wells of all furnaces are constructed using drilling tools, and the bottom of the outlet wells of all furnaces are horizontally extended using drilling tools equipped with a drill bit guidance system. Before gas injection fracturing in the gasification recovery area of ​​all furnaces, the bottom of the outlet wells of the furnaces must be sealed with a packer for the gas injection fracturing stage. Gas injection fracturing involves injecting high-pressure CO2 into the coal seam within the gasification recovery area through multiple diverter nozzles distributed at the bottom of the gasification recovery area, forming a network of fractures in the coal seam.

[0061] In some embodiments, the bottom of the gas outlet wells of all furnaces are horizontally extended using a drilling tool equipped with a drill bit guidance system to form a horizontal well. Figure 3 As shown, the drilling tool includes a drill bit 11, a bent screw power drill 13 mounted at the rear end of the drill bit 11 to power the drill bit 11, and a horizontal well downhole tractor 14 to provide traction for horizontal extension of the drill bit 11. The drill bit guidance system includes a drill bit guidance tool 12 mounted on the drill bit 11 to steer or guide the drill bit. The drilling tool is also connected to a gas injection fracturing pipe 9, which has several diverter nozzles 16 facing the corresponding furnace gasification production area. Each diverter nozzle 16 is equipped with a gas injection control valve 15. A packer 17 is installed on the gas injection fracturing pipe. All furnace inlet and / or outlet wells are reinforced and protected with casing 10 during operation.

[0062] In order to better realize the supply of carbon dioxide for gas injection fracturing, the supply of gasifying agent for combustion gasification, and the collection and separation of combustion gasification synthesis gas, the present invention also includes a coordinated advancement joint processing system (the coordinated advancement joint processing system is set on the ground in the underground coal gasification mining area, and preferably, a movable system is constructed to move with the advancement of mining), such as Figure 2As shown, the coordinated and advanced combined processing system includes a syngas separation system 7, a high-pressure carbon dioxide supply system, and a gasifying agent supply system. The gasifying agent supply system includes a steam generator 2, an oxygen generator 3, a gasifying agent control station 1, and a high-pressure gas injection pump unit 4. The steam generator 2 is used to produce steam, and the oxygen generator 3 is used to produce oxygen. The gasifying agent control station 1 is connected to the steam generator 2 and the oxygen generator 3, respectively, and mixes water vapor and oxygen into a gasifying agent, which is then transported to the high-pressure gas injection pump unit 4. The high-pressure gasification agent is generated and supplied to the gasification area for coal seam combustion and gasification. The high-pressure carbon dioxide supply system includes a CO2 storage tank 5 and a high-pressure carbon dioxide control and compressor unit 6 connected to the CO2 storage tank 5. The high-pressure carbon dioxide control and compressor unit 6 generates high-pressure CO2, which is used as fracturing gas for gas injection fracturing. The gas separation system 7 collects the mixed gas produced by coal seam combustion and gasification and separates it into combustible gas.

[0063] In some embodiments, as Figure 2 As shown, the gas separation system 7 is also connected to a use and storage end 8, and the combustible gas separated by the gas separation system 7 is transported to the use and storage end 8. The gas separation system 7 is respectively connected to the CO2 gas storage tank 5 and the gasification agent control station 1, and the CO2 gas separated by the gas separation system 7 is respectively transported to the CO2 gas storage tank 5 and the gasification agent control station 1. The gasification agent control station 1 also adds CO2 gas as a new gasification agent in the corresponding proportion of the gasification agent mainly composed of water vapor and oxygen, and conducts sampling research on the gasification area to be mined in the furnace. The gasification agent corresponding to the proportion of water vapor and oxygen as the main components is used. Some coal strata also require an appropriate amount of CO2 gas in the gasification agent. Therefore, the gas separation system 7 can supply a portion of CO2 gas to the gasification agent control station 1. Preferably, it is connected first. If the gasification agent control station 1 requires CO2 gas, a portion of CO2 gas is metered and input. The CO2 gas separated by the gas separation system 7 is transported to the CO2 gas storage tank 5 respectively, which can replenish the carbon dioxide gas in the CO2 gas storage tank 5, and allow the carbon dioxide gas generated in the combustion zone to circulate and replenish the CO2 gas storage tank 5, and be used for gas injection fracturing (gas injection fracturing uses high-pressure CO2 gas injection for fracturing), CO2 storage and well closure treatment (CO2 storage and well closure treatment also uses high-pressure CO2 gas injection for sealing), etc.

[0064] In some embodiments, the plugging, high-pressure CO2 storage and well closure treatment methods are as follows:

[0065] After cooling, one end of the gas outlet channel between the inlet and outlet wells of the furnace is sealed with a cement block 21 (in this embodiment, a grouting pipe 20 is provided for the installation of the cement block 21). High-pressure CO2 gas is then injected into the furnace's outlet channel and combustion cavity to seal the gas. A cement plug 24 is then sealed at the other end of the gas outlet channel (in this embodiment, a grouting pipe 20 is provided for the installation of the cement plug 24). Finally, a leak detection device 25 is installed at the wellhead of the inlet and / or outlet wells for leak monitoring and alarm.

[0066] In some embodiments, the idle cooling detection method of the furnace's fuel-gap zone is as follows: a temperature sensor 23 for monitoring the fuel-gap zone temperature is provided in the furnace's air inlet shaft. When the temperature sensor 23 drops to the ambient temperature, the idle cooling of the furnace's fuel-gap zone is completed.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for continuous coordinated advancement of the common well of the front and rear furnaces of underground coal gasification mining, characterized by: The methods include: S1. Construct the inlet and outlet wells of Furnace No.

1. The bottom of the outlet well is horizontally extended to the bottom of the inlet well without being connected. The outlet well is used to perform gas injection fracturing on the gasification area to be mined of Furnace No.

1. After the gas injection fracturing is completed, the bottom of the outlet well is horizontally extended to the bottom of the inlet well and connected to each other. S2. A proportioned gasifying agent is introduced into the bottom of the inlet well of the No. 1 furnace, and coal seam combustion and gasification operations are carried out in the gasification area to be mined in the No. 1 furnace from the bottom of the inlet well toward the bottom of the outlet well. Synthesis gas is collected through the outlet well of the No. 1 furnace. Simultaneously, the outlet well of the No. 2 furnace is constructed. The bottom of the outlet well of the No. 2 furnace extends horizontally to the bottom of the outlet well of the No. 1 furnace without being connected. Gas injection and fracturing are carried out in the gasification area to be mined in the No. 2 furnace using the outlet well of the No. 2 furnace. When the combustion and gasification of the gasification mining area of ​​the No. 1 furnace and the collection of synthesis gas are completed, the bottom of the outlet well of the No. 2 furnace is horizontally extended to the bottom of the inlet well and connected to each other, and the gasification mining area of ​​the No. 1 furnace becomes a combustion air zone; S3. Allow the combustion zone of the No. 1 furnace to be idle and cooled; use the outlet well of the No. 1 furnace as the inlet well of the No. 2 furnace, introduce a proportioned gasifying agent into the bottom of the inlet well of the No. 2 furnace, and perform coal seam combustion gasification operations on the gasification and mining area of ​​the No. 2 furnace from the bottom of the inlet well of the No. 2 furnace toward the bottom of the outlet well of the No. 2 furnace, and collect synthesis gas through the outlet well of the No. 2 furnace; at the same time, construct the outlet well of the No. 3 furnace, and the bottom of the outlet well of the No. 3 furnace extends horizontally to the bottom of the outlet well of the No. 2 furnace without being connected, and use the outlet well of the No. 3 furnace to perform gas injection and fracturing on the gasification and mining area of ​​the No. 3 furnace; After the combustion and gasification of the gasification mining area of ​​the No. 2 furnace and the collection of synthesis gas are completed, the gasification mining area of ​​the No. 2 furnace becomes a combustion-free area, and the bottom of the outlet well of the No. 3 furnace is horizontally extended to the bottom of the inlet well and connected to each other; after the cooling is completed, the No. 1 furnace is sealed, the high-pressure CO2 is sealed and the well is closed. The No. 1 furnace undergoes the process of gas injection fracturing, combustion and gasification, idle cooling, CO2 sealing and well closure in steps S1 to S3; S4. According to the method of constructing the gas outlet well of furnace No. 2 in step S2, the gas outlet wells of furnace No. 4 and subsequent furnaces are constructed. When constructing the gas outlet well of furnace No. 4, gas injection and fracturing are carried out in the gasification waiting area, and combustion and gasification are followed up in the gasification waiting area of ​​furnace No. 3; the combustion and gasification area of ​​furnace No. 2 is idle for cooling and CO2 sealing and well closure treatment. The sealing, high-pressure CO2 sealing and well closure treatment methods are as follows: after the cooling is completed, one end of the gas outlet channel between the gas inlet well and the gas outlet well of the furnace is sealed with a cement stone sealing block (21); then high-pressure CO2 gas is injected into the gas outlet channel and the combustion and gas cavity of the furnace for sealing; then a cement plug (24) is sealed at the other end of the gas outlet channel; finally, a leakage detection device (25) is installed at the wellhead of the gas inlet well and / or the gas outlet well to monitor and alarm for leakage; and the process technology of furnace No. 2 and subsequent furnaces is completed in sequence according to steps S1 to S3.

2. The method for continuous coordinated advancement of the common well of the front and rear furnaces of underground coal gasification mining according to claim 1 is characterized by: The gas inlet wells and / or gas outlet wells of all furnaces are constructed with drilling tools, and the horizontal extension of the bottom of the gas outlet wells of all furnaces is carried out with drilling tools equipped with a drill bit guidance system; before gas injection fracturing in the gasification waiting area of ​​all furnaces, the bottom of the gas outlet well of the furnace needs to be sealed with a packer during the gas injection fracturing stage. Gas injection fracturing injects high-pressure CO2 into the coal seam inside the gasification waiting area through several diversion nozzles distributed at the bottom of the gasification waiting area of ​​the furnace, and forms a fracture network in the coal seam.

3. The method for continuous coordinated advancement of the common well of the front and rear furnaces of underground coal gasification mining according to claim 2 is characterized by: During the gas injection fracturing stage of the furnace, a gas sensor (18) is installed at the wellhead of the corresponding gas inlet well of the furnace. When the gas sensor (18) detects that CO2 has been stably discharged through the fracturing network of the gasification mining area and the gas inlet well, the fracturing network of the coal seam inside the gasification mining area is good, and the gas injection fracturing is completed.

4. The method for continuous coordinated advancement of the common well of the front and rear furnaces of underground coal gasification mining according to claim 1 is characterized by: The invention also includes a coordinated advancement combined processing system, wherein the coordinated advancement combined processing system includes a synthesis gas separation system (7), a high-pressure carbon dioxide supply system and a gasification agent supply system, wherein the gasification agent supply system includes a water vapor generator (2), an oxygen generator (3), a gasification agent control station (1) and a gas injection high-pressure pump group (4), wherein the water vapor generator (2) is used to produce water vapor, and the oxygen generator (3) is used to produce oxygen, and the gasification 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 gasification agent. The main mixture is proportioned to form a gasifying agent and is transported 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 to be mined for coal seam combustion gasification; the high-pressure carbon dioxide supply system includes a CO2 gas storage tank (5) and a high-pressure carbon dioxide control and compressor group (6) connected to the CO2 gas storage tank (5). The high-pressure carbon dioxide control and compressor group (6) generates high-pressure CO2 and is used as fracturing gas for gas injection fracturing; the synthesis gas separation system (7) is used to collect the mixed gas generated by coal seam combustion gasification and separate it to obtain combustible gas.

5. The method for continuous coordinated advancement of the common well of the front and rear furnaces of underground coal gasification mining according to claim 4 is characterized by: The synthesis gas separation system (7) is also connected to a use and storage end (8), and the combustible gas separated by the synthesis gas separation system (7) is transported to the use and 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). The gasification agent control station (1) also adds CO2 gas as a new gasification agent in a corresponding ratio to the gasification agent mainly composed of water vapor and oxygen.

6. The method for continuous coordinated advancement of the common shaft for front and rear furnaces of underground coal gasification mining according to claim 4 or 5, characterized in that: The bottom of the gas outlet well of all furnaces is horizontally extended by a drilling tool equipped with a drill bit guide system to perform horizontal extension construction and form a horizontal well. The drilling tool is also combined with a gas injection fracturing pipe (9), and the gas injection fracturing pipe is provided with a plurality of diversion nozzles (16) facing the corresponding furnace gasification mining area, and each diversion nozzle (16) is equipped with a gas injection control valve (15); the drilling tool includes a drill bit (11) and a bent screw power drill (13) installed at the rear end of the drill bit (11) to drive the drill bit (11) with power, and a horizontal well downhole tractor (14) to serve as traction power for the horizontal extension construction of the drill bit (11). The drill bit guide system includes a drill bit guide tool (12) installed on the drill bit (11) to steer or guide the drill bit.

7. The method for continuous coordinated advancement of the common well of the front and rear furnaces of underground coal gasification mining according to claim 6 is characterized by: A packer (17) is installed on the gas injection fracturing pipe; the gas inlet wells and / or gas outlet wells of all furnaces are reinforced and protected by casing (10) during the working phase.

8. The method for continuous coordinated advancement of the common well of the front and rear furnaces of underground coal gasification mining according to claim 1 is characterized by: The idle cooling detection method of the furnace's combustion zone is as follows: a temperature sensor (23) for monitoring the combustion zone temperature is provided in the furnace's air inlet well; when the temperature sensor (23) drops to ambient temperature, the idle cooling of the furnace's combustion zone is completed.

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