Continuous and coordinated propelling method for common well of front furnace and rear furnace in underground coal gasification mining

Abstract

The invention discloses a coal underground gasification mining front and rear furnace common well continuous coordination propulsion method which comprises the following steps: S1, constructing a gas inlet well and a gas outlet well of a first furnace, and performing gas injection fracturing on a gasification to-be-mined area of the first furnace by using the gas outlet well; s2, coal seam combustion gasification operation is conducted on the gasification to-be-mined area of the first furnace, and synthesis gas is collected through a gas outlet well of the first furnace; meanwhile, a gas outlet well of the second furnace is used for conducting gas injection fracturing on the gasification to-be-mined area of the second furnace; s3, the combustion space area of the first furnace is made to be idle for cooling, meanwhile, the second furnace conducts combustion gasification operation, and the third furnace conducts gas injection fracturing operation; each furnace is subjected to a flow process of gas injection fracturing, combustion gasification, idle cooling and CO2 storage well closing treatment; and S4, completing each flow process in sequence. The upper furnace and the lower furnace carry out difference node follow-up according to the flow process by one flow node, the upper furnace and the lower furnace carry out well sharing, the number of drilled wells is reduced, geological damage is relieved, and the mining efficiency is improved.

Description

Technical Field

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

[0002] Underground coal gasification is the process of directly converting underground coal resources into coal gas. Underground coal gasification can efficiently convert underground coal resources into usable energy, improve coal mining efficiency, and reduce coal mining costs. Before the development of deep underground coal gasification, a lot of geological surveys and surveys are required 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, which all need to be further resolved. Since underground coal is located underground and distributed in a plane layer, it is easy to collapse if combustion gasification is carried out layer by layer. It is best to pre-fracture the coal layer to reduce the probability of major combustion gasification accidents. Underground coal gasification often uses the method of drilling out of the mine and fracturing and destroying from the side of the mine. The area of ​​fracturing and destruction is limited, which requires intensive drilling. Intensive drilling will increase the workload and affect the geological environment, and increase the difficulty of post-mining disposal of the combustion zone and the mine. Underground coal gasification not only involves combustion gasification (combustion gasification generally requires two mines, one mine inputs gasification agent, and the other mine outputs synthesis gas containing combustible gas), but also involves cooling the combustion cavity area and post-mining protection measures. Its process is a close sequence of operations. The current technology is to complete the underground gasification operation at a combustion gasification point (including two mines) and then conduct underground gasification operations at nearby combustion gasification points; in order to increase the output of combustible gas, it is necessary to set up multiple combustion gasification points for synchronous gasification operations, which will greatly increase the number of mines, not only with greater construction difficulty and post-mining disposal difficulty (also causing waste of manpower, material resources and time), but also causing greater damage to the geological environment (because of multiple drillings in the rock formation, which affects the sealing and stability of the combustion cavity), thereby increasing the risk of underground coal gasification operations. Therefore, there are still many technical problems in underground coal gasification, which is also a technical direction that urgently needs to be studied 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 outlet well of the upper furnace after gas injection fracturing is used 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 wells of the upper and lower furnaces, reduce the number of drilling wells and the drilling workload, and also 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 of a front and rear furnace of underground coal gasification mining, the method comprising:

[0006] S1. Construct the gas inlet well and gas outlet well of No. 1 furnace. The bottom of the gas outlet well is horizontally extended to the bottom of the gas inlet well and is not connected. The gasification waiting area of ​​No. 1 furnace is subjected to gas injection fracturing by 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;

[0007] S2, introducing a proportioned gasifying agent into the bottom of the gas inlet well of the No. 1 furnace, carrying out coal seam combustion gasification operation on the gasification mining area of ​​the No. 1 furnace from the bottom of the gas inlet well toward the bottom of the gas outlet well, and collecting synthetic gas through the gas outlet well of the No. 1 furnace; at the same time, constructing the gas outlet well of the No. 2 furnace, the bottom of the gas outlet well of the No. 2 furnace horizontally extends to the bottom of the gas outlet well of the No. 1 furnace and is not connected, and the gas outlet well of the No. 2 furnace is used to perform gas injection fracturing on the gasification mining area of ​​the No. 2 furnace;

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

[0009] S3, leaving the combustion and emptying area of ​​furnace No. 1 idle to cool down; using the outlet well of furnace No. 1 as the inlet well of furnace No. 2, introducing the proportioned gasifying agent into the bottom of the inlet well of furnace No. 2, carrying out coal seam combustion gasification operation on the gasification and mining area of ​​furnace No. 2 from the bottom of the inlet well of furnace No. 2 toward the bottom of the outlet well of furnace No. 2, and collecting the synthetic gas through the outlet well of furnace No. 2; constructing the outlet well of furnace No. 3 at the same time, the bottom of the outlet well of furnace No. 3 horizontally extends to the bottom of the outlet well of furnace No. 2 and is not connected, and the outlet well of furnace No. 3 is used to carry out gas injection fracturing on the gasification and mining area of ​​furnace No. 3;

[0010] After the combustion gasification and synthesis gas collection of the gasification mining area of ​​the No. 2 furnace are completed, the gasification mining area of ​​the No. 2 furnace becomes a combustion-empty 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 blocked, high-pressure 0O2 is sealed and the well is closed. The No. 1 furnace undergoes the process of gas injection fracturing, combustion gasification, idle cooling, CO2 sealing and well closure 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 the combustion gasification of the gasification area to be mined of the No. 3 furnace is followed up; the combustion and empty area of ​​the No. 2 furnace is idle for cooling and CO2 sealing and well closure treatment.

[0013] Preferably, the air inlet wells and / or air outlet wells of all furnaces are constructed with drilling tools, and the bottom of the air outlet wells of all furnaces are horizontally extended with 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 air outlet well of the furnace needs to be sealed with a packer during the gas injection fracturing stage, and the 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 to form 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 fracturing network of the gasification area to be mined and the gas inlet well, the fracturing network of the coal seam inside the gasification area to be mined is good and the gas injection and fracturing is completed.

[0015] Preferably, the present invention also includes a coordinated advancement combined 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 respectively connected to the water vapor generator and the oxygen generator 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 unit connected to the CO2 gas storage tank. The high-pressure carbon dioxide control and compressor unit 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 of a 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 guide 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 guide system includes a drill bit guide 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 equipped 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 closed 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 fuel-gap zone of the furnace is as follows: a temperature sensor for monitoring the temperature of the fuel-gap zone is provided in the air inlet shaft of the furnace, and when the temperature sensor drops to the ambient temperature, the idle cooling of the fuel-gap zone of the furnace 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 exploitation is carried out in accordance with the process-based technology of gas injection 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 technology with a difference of one process node; the outlet well of the upper furnace after gas injection fracturing is used 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 also 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 are continuously coordinated and advanced, 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 line 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, fast mining and production, and increases the total mining output, thereby greatly improving the mining efficiency.

[0025] (3) During 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 the safety of combustion and gasification and the vaporization efficiency. The high-pressure injection of CO2 can also effectively displace the 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 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 and exploitation. 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 during the exploitation of the 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 area to be mined for combustion and gasification operations.

[0027] (5) The idle cooling and CO2 storage and well closure treatments of the present invention are the post-processing procedures for furnace mining, and 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. For example, when gas injection and fracturing are completed, gas outlet monitoring of the fracture network is performed through a gas sensor. When CO2 storage and well closure treatment is completed, leakage monitoring and alarming are performed through a leakage detection device installed at the wellhead, both of which ensure the efficiency and safety performance of 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 of 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 of the No. 1 furnace 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 of the furnace combustion cavity in the embodiment;

[0032] Figure 5 It 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] The present invention is further described in detail below in conjunction with embodiments:

[0036] Example

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

[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 fracturing stage, the horizontal well extending horizontally from the bottom of the gas outlet well is not connected to the gas inlet well. Figure 3 The connected positions in the figure are indicated by dotted lines as not connected), and the gasification waiting area of ​​the No. 1 furnace is subjected to gas injection fracturing by 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 the subsequent furnaces only need to construct an air outlet well, and use the air outlet well of the previous furnace 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 from a technical perspective and protects the underground rock structure of the coal).

[0040] Since furnace No. 1 is the first furnace, the gas injection fracturing technology method 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 the No. 1 furnace and extended horizontally to form a horizontal well. At this time, the end of the extended horizontal well should not be connected to the bottom of the intake well, so that the outlet well of the No. 1 furnace as a whole forms an L-shaped mine, and the L-shaped mine is not connected to the intake well of the No. 1 furnace at this time, and the L-shaped mine is a separate mine). The outlet well of the No. 1 furnace is used to perform gas injection and fracturing on the gasification area to be mined of the No. 1 furnace (since the L-shaped mine is a separate mine, the gasification area to be mined of the No. 1 furnace can be treated with gas injection and fracturing. The gasification area to be mined of the No. 1 furnace is Figure 1 The right side area of ​​the middle gas outlet well), after the gas injection and 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 (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 up 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), and furnace No. 2 has 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 up the underground gasification operation of furnace No. 2, and furnace No. 3 also adopts the above-mentioned gas injection fracturing method, and so on. The next furnace follows up 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 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 area to be mined, the fracturing network of the coal seam inside the gasification area to be mined is good, and the gas injection fracturing is completed.

[0044] S2. A proportioned gasifying agent is introduced into the bottom of the inlet well of the No. 1 furnace, and the coal seam combustion gasification operation is carried out on the gasification mining area of ​​the No. 1 furnace from the bottom of the inlet well to the bottom of the outlet well, and the synthetic 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, and the bottom of the outlet well of the No. 2 furnace horizontally extends 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 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 fracturing of the No. 2 furnace can be carried out at the same time. The combustion gasification of the No. 1 furnace uses the inlet well and outlet well of the No. 1 furnace, and the gas injection 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; when the No. 2 furnace is monitoring the gas injection fracturing (gas injection fracturing monitoring is the preferred step method) or the combustion gasification is connected.

[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 inlet well of furnace No. 1 (at this time, the outlet well of furnace No. 1 is connected to the bottom of the inlet well), and the coal seam combustion gasification operation is carried out in the gasification area of ​​furnace No. 1 from the bottom of the inlet well to the bottom of the outlet well, and the synthesis gas is collected through the outlet well of furnace No. 1. The synthesis gas contains useful combustible gas and other substances that need to be removed and separated (such as water vapor, carbon dioxide, etc.), which are subsequently 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.

[0047] The above is an introduction to the combustion gasification method using furnace No. 1 as an example. In the technology of the present invention, furnace No. 2 follows the underground gasification operation of furnace No. 1, and furnace No. 3 follows the underground gasification operation of furnace No. 2. When furnace No. 1 is in combustion gasification, furnace No. 2 performs gas injection fracturing. The bottom of the gas outlet well of furnace No. 2 extends horizontally to the bottom of the gas outlet well of furnace No. 1 (the gas outlet well of furnace No. 1 is regarded as the gas inlet well of furnace No. 2 as a backup) and is not connected. The gas outlet well of furnace No. 2 is used to perform gas injection fracturing on the gasification waiting area of ​​furnace No. 2. The gas injection fracturing operation of furnace No. 2 is performed according to 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. And so on. The next furnace follows the previous one and performs combustion and gasification operations of the corresponding gasification area to be mined according to the above-mentioned combustion and gasification method.

[0049] When the combustion gasification and synthesis gas collection of the gasification mining area of ​​furnace No. 1 are completed, the bottom of the gas outlet well of furnace No. 2 is horizontally extended to the bottom of the gas inlet well and connected to each other, and the gasification mining area of ​​furnace No. 1 becomes a combustion-free zone. "When the combustion gasification and synthesis gas collection of the gasification mining area of ​​furnace No. 1 are completed, the bottom of the gas outlet well of furnace No. 2 is horizontally extended to the bottom of the gas 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 gas outlet well of furnace No. 2 is horizontally extended to the bottom of the gas inlet well of furnace No. 2 (at this time, the gas inlet well of furnace No. 2 and the gas outlet well of furnace No. 1 are the same well, called the gas inlet and outlet directional well) and connected to each other.

[0050] S3. Let the combustion and empty area of ​​furnace No. 1 sit idle to cool down. Use the gas outlet well of furnace No. 1 as the gas inlet well of furnace No. 2, introduce the proportioned gasifying agent into the bottom of the gas inlet well of furnace No. 2, carry out coal seam combustion and gasification operation on the gasification and mining area of ​​furnace No. 2 from the bottom of the gas inlet well of furnace No. 2 toward the bottom of the gas outlet well of furnace No. 2, and collect the synthesis gas through the gas outlet well of furnace No. 2. At the same time, construct the gas outlet well of furnace No. 3, the bottom of the gas outlet well of furnace No. 3 extends horizontally to the bottom of the gas outlet well of furnace No. 2 and is not connected, and use the gas outlet well of furnace No. 3 to carry out gas injection and fracturing on the gasification and mining area of ​​furnace No. 3. When the combustion and gasification of furnace No. 1 is completed or it is idle to cool down in the combustion and empty area, let the gas outlet well of furnace No. 1 be used as the gas inlet well of furnace No. 2, and furnace No. 2 is burned and gasified according to the above-mentioned combustion and gasification method. At the same time, follow up the construction of the gas outlet well of furnace No. 3 and carry out gas injection and fracturing operation on furnace No. 3.

[0051] The above takes the idle cooling treatment of No. 1 furnace entering the combustion zone as an example. The No. 2 furnace in the technology of the present invention follows the underground gasification operation of No. 1 furnace, and the No. 3 furnace follows the underground gasification operation of No. 2 furnace; when the No. 1 furnace is idle and cooled, the No. 2 furnace carries out combustion gasification, the No. 3 furnace carries out 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 is to let 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 then 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 fuel-air 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 boiler No. 1 is completed, boiler 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 boiler No. 2 is completed, boiler 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 boiler follows the previous one and carries out CO2 storage and well closure treatment for 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 follow-up process for 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 the combustion gasification and synthesis gas collection of the gasification mining area of ​​the No. 2 furnace are completed, the gasification mining area of ​​the No. 2 furnace becomes a combustion empty 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 plugged, the high-pressure CO2 is sealed and the well is closed. The No. 1 furnace undergoes the process of gas injection fracturing, combustion gasification, idle cooling, CO2 sealing and well closure in steps S1 to S3. Similarly, furnace No. 2, furnace No. 3, etc. all follow the process-based technology of gas injection fracturing, combustion gasification, idle cooling, and CO2 storage and well closure treatment. The above process-based technology includes four process nodes: gas injection fracturing, combustion gasification, idle cooling, and CO2 storage and well closure treatment. The front and rear furnaces are one process node apart (that is, the front and rear furnaces are one process node apart) for follow-up operations. If the four process nodes are respectively arranged as the first, second, third, and fourth process nodes, then if the rear furnace is at the second process node, the front 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 fracturing, combustion gasification, idle cooling, and CO2 storage and well closure treatment.

[0058] S4. Construct the gas outlet wells of No. 4 furnace and subsequent furnaces according to the method of constructing the gas outlet well of No. 2 furnace in step S2, and complete the process technology of No. 2 furnace 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: During the construction of the gas outlet well of furnace No. 4, gas injection and fracturing are carried out in the gasification waiting area, and combustion gasification is followed up in the gasification waiting area of ​​furnace No. 3. The combustion and empty area of ​​furnace No. 2 is idle for cooling and CO2 sealing and well closure treatment. The idle cooling and CO2 sealing and well closure treatment of furnace No. 2 are not necessarily carried out strictly in the order of furnaces (but the furnace must be idle for cooling first, and then CO2 sealing and well closure treatment).

[0060] In some embodiments, the gas inlet wells and / or gas outlet wells of all furnaces are constructed by drilling tools, and the bottom of the gas outlet wells of all furnaces are horizontally extended by drilling tools equipped with a drill bit guide 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 by a packer in the gas injection fracturing stage. The gas injection fracturing injects high-pressure CO2 into the coal seam inside the gasification mining area through a plurality of diversion nozzles distributed at the bottom of the gasification mining area of ​​the furnace, and forms a fracture network 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 and a bent screw power drill 13 installed at the rear end of the drill bit 11 to drive the drill bit 11, a horizontal well downhole tractor 14 to provide traction power for the horizontal extension construction of the drill bit 11, and a drill bit guide system includes a drill bit guide tool 12 installed on the drill bit 11 to turn or guide the drill bit. The drilling tool is also combined with a gas injection fracturing pipe 9, on which a number of diversion nozzles 16 facing the corresponding furnace gasification to-be-mined area are opened, and each diversion nozzle 16 is installed with a gas injection control valve 15; a packer 17 is installed on the gas injection fracturing pipe; and the gas inlet wells and / or gas outlet wells of all furnaces are reinforced and protected by casing 10 during the working stage.

[0062] In order to better realize the supply of carbon dioxide for gas injection fracturing, the proportion 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 arranged on the ground of 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 promotion joint processing system includes a synthesis gas separation system 7, a high-pressure carbon dioxide supply system and a gasification agent supply system. 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. The water vapor generator 2 is used to produce water vapor, and the oxygen generator 3 is used to produce oxygen. The gasification agent control station 1 is connected to the water vapor generator 2 and the oxygen generator 3 respectively and mixes water vapor and oxygen into a gasification agent mainly for transportation to the gas injection high-pressure pump group 4. The gas injection high-pressure pump group 4 is used to generate a 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 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 gas separation system 7 is used to collect the mixed gas generated by coal seam combustion gasification and separate it to obtain combustible gas.

[0063] In some embodiments, Figure 2 As shown, the gas separation system 7 is also connected to the 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 connected to the CO2 gas storage tank 5 and the gasification agent control station 1 respectively, and the CO2 gas separated by the gas separation system 7 is transported to the CO2 gas storage tank 5 and the gasification agent control station 1 respectively. 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 samples the gasification area of ​​the furnace to be mined. The gasification agent corresponding to the proportion of water vapor and oxygen as the main components is used for research. Some coal strata also need to be proportioned with an appropriate amount of CO2 gas in the gasification agent. Therefore, the gas separation system 7 can supply a part of the CO2 gas to the gasification agent control station 1. Preferably, it is connected first. If the gasification agent control station 1 needs CO2 gas in the proportion, a part of the 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, so as to replenish the carbon dioxide gas in the CO2 gas storage tank 5, and the carbon dioxide gas generated in the combustion zone is circulated and replenished to the CO2 gas storage tank 5, and used for gas injection fracturing (gas injection fracturing uses high-pressure CO2 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 the temperature is lowered, one end of the gas outlet channel between the gas inlet well and the gas outlet well of the furnace is blocked by a cement stone blocking block 21 (a grouting pipe 20 is provided in this embodiment to construct the cement stone blocking block 21). Then, high-pressure CO2 gas is injected into the gas outlet channel and the combustion cavity of the furnace for sealing. Then, a cement plug 24 is closed at the other end of the gas outlet channel (a grouting pipe 20 is provided in this embodiment to construct the cement plug 24). Finally, a leakage detection device 25 is installed at the wellhead of the gas inlet well and / or the gas outlet well for leakage monitoring and alarm.

[0066] In some embodiments, the idle cooling detection method of the fuel-gap zone of the furnace is as follows: a temperature sensor 23 for monitoring the temperature of the fuel-gap zone is provided in the air inlet shaft of the furnace. When the temperature sensor 23 drops to the ambient temperature, the idle cooling of the fuel-gap zone of the furnace 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 protection scope 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 in that: The methods include: S1. Construct the gas inlet well and gas outlet well of No. 1 furnace. The bottom of the gas outlet well is horizontally extended to the bottom of the gas inlet well and is not connected. The gasification waiting area of ​​No. 1 furnace is subjected to gas injection fracturing by 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; S2, introducing a proportioned gasifying agent into the bottom of the gas inlet well of the No. 1 furnace, carrying out coal seam combustion gasification operation on the gasification mining area of ​​the No. 1 furnace from the bottom of the gas inlet well toward the bottom of the gas outlet well, and collecting synthetic gas through the gas outlet well of the No. 1 furnace; at the same time, constructing the gas outlet well of the No. 2 furnace, the bottom of the gas outlet well of the No. 2 furnace horizontally extends to the bottom of the gas outlet well of the No. 1 furnace and is not connected, and the gas outlet well of the No. 2 furnace is used to perform gas injection fracturing on the gasification mining area of ​​the No. 2 furnace; When the combustion gasification and synthesis gas collection of the gasification waiting area of ​​the No. 1 furnace are completed, the bottom of the gas outlet well of the No. 2 furnace is horizontally extended to the bottom of the gas inlet well and connected to each other, and the gasification waiting area of ​​the No. 1 furnace becomes a combustion air area; S3, leaving the combustion and emptying area of ​​furnace No. 1 idle to cool down; using the outlet well of furnace No. 1 as the inlet well of furnace No. 2, introducing the proportioned gasifying agent into the bottom of the inlet well of furnace No. 2, carrying out coal seam combustion gasification operation on the gasification and mining area of ​​furnace No. 2 from the bottom of the inlet well of furnace No. 2 toward the bottom of the outlet well of furnace No. 2, and collecting the synthetic gas through the outlet well of furnace No. 2; constructing the outlet well of furnace No. 3 at the same time, the bottom of the outlet well of furnace No. 3 horizontally extends to the bottom of the outlet well of furnace No. 2 and is not connected, and the outlet well of furnace No. 3 is used to carry out gas injection fracturing on the gasification and mining area of ​​furnace No. 3; After the combustion gasification and synthesis gas collection of the gasification mining area of ​​the No. 2 furnace are completed, the gasification mining area of ​​the No. 2 furnace becomes a combustion-empty 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 blocked, high-pressure CO2 is sealed and the well is closed. The No. 1 furnace undergoes the process of gas injection fracturing, combustion gasification, idle cooling, CO2 sealing and well closure treatment in steps S1 to S3; 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.

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 outlet well of the No. 4 furnace is under construction and gas injection and fracturing are being carried out in the gasification area to be mined, while the combustion gasification of the gasification area to be mined of the No. 3 furnace is followed up; the idle cooling and C02 storage and well closure treatment are carried out in the combustion and empty area of ​​the No. 2 furnace.

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 1 is characterized by: The air inlet wells and / or air outlet wells of all furnaces are constructed with drilling tools, and the bottom of the air outlet wells of all furnaces are horizontally extended with drilling tools equipped with a drill bit guidance system; before gas injection and fracturing in the gasification waiting area of ​​all furnaces, the bottom of the air outlet well of the furnace needs to be sealed with a packer during the gas injection and fracturing stage. Gas injection and fracturing injects high-pressure C02 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.

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 3 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 is 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.

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 1 is characterized by: The invention also includes a coordinated advancement combined processing system, the coordinated advancement combined processing system including a synthesis gas separation system (7), a high-pressure carbon dioxide supply system and a gasification agent supply system, the gasification agent supply system including a water vapor generator (2), an oxygen generator (3), a gasification agent control station (1) and a gas injection high-pressure pump group (4), the water vapor generator (2) is used to produce water vapor, the oxygen generator (3) is used to produce oxygen, 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 to generate oxygen. The main mixed gasification agent is transported to the gas injection high-pressure pump group (4), which 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 (5) and a high-pressure carbon dioxide control and compressor group (6) connected to the CO2 gas storage tank (5), and 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 gas separation system (7) is used to collect the mixed gas generated by coal seam combustion gasification and separate it to obtain combustible gas.

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

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 5 or 6, 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 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 provide 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.

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 7 is characterized by: The drilling tool is also combined with a gas injection fracturing pipe (9), on which a plurality of diversion nozzles (16) facing the corresponding furnace gasification mining area are opened, and each diversion nozzle (16) is installed with a gas injection control valve (15); a packer (17) is installed on the gas injection fracturing pipe; and the gas inlet wells and / or gas outlet wells of all furnaces are reinforced and protected by casing (10) during the working stage.

9. 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 plugging, high-pressure CO2 storage and well closure treatment methods are as follows: After the temperature is lowered, one end of the gas outlet passage 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 passage and the combustion cavity of the furnace for sealing; then, a cement plug (24) is sealed at the other end of the gas outlet passage; 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.

10. 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 combustion zone of the furnace is as follows: a temperature sensor (23) for monitoring the temperature of the combustion zone is arranged in the air intake shaft of the furnace; when the temperature sensor (23) is lowered to the ambient temperature, the idle cooling of the combustion zone of the furnace is completed.

Images