High-temperature heat pipe-based oil-rich coal in-situ underground combustion and pyrolysis oil and gas recovery cooperative system and process

Abstract

The invention relates to an oil-rich coal in-situ underground combustion and pyrolysis oil and gas recovery cooperative system based on high-temperature heat pipes. The system comprises a vertical shaft, a horizontal drill hole and a high-temperature heat pipe set. A high-temperature heat pipe set is arranged on the coal seam of the vertical shaft. A plurality of vertical wells are arranged with the vertical well as the center. Each vertical well is communicated with two parallel horizontal drill holes with different depths in the coal seam, the horizontal drill holes communicated with the adjacent vertical wells are not at the same depth of the coal seam, and four horizontal drill hole groups with different depths are arranged in the coal seam. Oxygen and carbon dioxide are mixed into oxygen-enriched gas, and combustion of coal in a certain horizontal drill hole is achieved. Flue gas generated by coal combustion is subjected to heat exchange through the high-temperature heat pipe set, and water vapor or carbon dioxide is heated. The high-temperature water vapor or carbon dioxide and the high-temperature flue gas after heat exchange enter the other two horizontal drill holes in the coal seam respectively, coal is pyrolyzed, and pyrolysis gas and tar are generated. According to the system, high-quality tar and high-calorific-value pyrolysis gas can be obtained, and only a small amount of energy needs to be provided from the outside.

Description

Technical Field

[0001] This invention relates to a system and process for the coordinated production of oil and gas from in-situ underground combustion and pyrolysis of oil-rich coal based on high-temperature heat pipes, belonging to the field of in-situ pyrolysis technology for oil-rich coal. Background Technology

[0002] Oil-rich coal refers to coal with a tar yield greater than 7% obtained from low-temperature carbonization. Through scientific and rational pyrolysis, oil-rich coal resources can be converted into abundant coal tar, coal pyrolysis gas, and clean, smokeless semi-coke. Academician Wang Shuangming of the Chinese Academy of Engineering pointed out: "Oil-rich coal is not only coal, but also a coal-based oil and gas resource." By extracting scarce oil and gas resources through the pyrolysis of oil-rich coal, the low-carbon utilization of high-carbon coal-based resources can be achieved.

[0003] In-situ pyrolysis of oil-rich coal involves connecting multiple wells through artificial fractures in the coal seam, based on engineering drilling. The coal seam is then heated using technologies such as electric heating or gas-based heat carriers, causing the oil-rich coal to pyrolyze and generate oil and gas resources, which are then extracted in pumping wells. However, invention patent application CN202211336439.2, "An In-situ Pyrolysis System and Method for Oil-Rich Coal," proposes using nitrogen as the heat carrier gas. However, nitrogen is difficult to separate from the pyrolysis gas after mixing, leading to a decrease in the quality of the pyrolysis gas and affecting subsequent utilization. Furthermore, using nitrogen as the heat carrier gas requires high-quality energy sources for heating, such as natural gas or electricity, increasing energy consumption and costs. The high-temperature, high-pressure heat carrier gas also requires long-distance transmission, resulting in significant heat loss and poor safety.

[0004] Therefore, this patent proposes a system and process for the coordinated in-situ underground combustion and pyrolysis of oil-rich coal based on a high-temperature heat pipe. This system utilizes oxygen and carbon dioxide as combustion aids to achieve the combustion and pyrolysis of underground coal. Combined with the isothermal and efficient heat transfer characteristics of the high-temperature heat pipe, it enables the efficient pyrolysis of underground coal seams. This technology not only yields high-quality tar and high-calorific-value pyrolysis gas but also requires only a small amount of external energy. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a system and process for the coordinated production of oil and gas from in-situ underground combustion and pyrolysis of oil-rich coal based on high-temperature heat pipes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A high-temperature heat pipe-based in-situ underground combustion and pyrolysis oil and gas production synergistic system for oil-rich coal includes a vertical shaft (12) drilled in the oil-rich coal seam to be pyrolyzed. The vertical shaft (12) has a first well (12-1) drilled in the surface layer and a first well casing (12-2) installed. The outer wall of the first well casing (12-2) and the inner wall of the first well (12-1) are filled with cement for sealing and reinforcement. A second well (12-3) is drilled inside the first well. The second drilling (12-3) extends to the bottom of the coal seam. A second drilling casing (12-4) is installed inside the second drilling (12-3) from top to bottom, extending to the bottom of the coal seam. The outer wall of the second drilling casing (12-4) and the interior of the second drilling (12-3) are filled with refractory cement for sealing and reinforcement. A high-temperature heat pipe assembly is installed inside the casing of the second drilling in the coal seam. Multiple vertical wells are arranged around a circle centered on the vertical shaft (12). The vertical wells are evenly distributed on the circumference, with adjacent vertical wells... The included angle between vertical wells is 15° to 45°; two parallel horizontal wells of different depths are drilled from each vertical well into the casing of the second drilling of the vertical well (12). The horizontal wells are all in the coal seam, which is divided into four layers according to thickness: the bottom layer is the first layer, and the layers above are the second, third and fourth layers; the two horizontal wells of each vertical well are located on different coal seams: the horizontal well (L1-1) of the vertical well (V1) is in the first layer of the coal seam, the horizontal well (L1-4) is in the fourth layer of the coal seam, and the vertical well ( The horizontal well (L2-2) of V2 is in the second layer of the coal seam, the horizontal well (L2-3) is in the third layer of the coal seam, and the horizontal well (L3-1) of the vertical well (V3) is in the first layer of the coal seam, and the horizontal well (L3-4) is in the fourth layer of the coal seam. The arrangement of the horizontal wells continues in this pattern. The state of each vertical well is different in different sections. Some are used as combustion aid injection wells with their inlets connected to the combustion aid supply system, some are used as production wells with their outlets connected to the oil and gas processing and collection system, and the remaining vertical wells are in a closed state.

[0007] Furthermore, the oil and gas treatment and collection system includes a gas-solid separation device (1), a coal ash storage tank (2), a heat exchanger (3), a gas-liquid separation device (4), a desulfurization and decarbonization device (5), an oil-water separation device (6), an oil storage tank (7), and a water treatment device (8); the inlet of the gas-solid separation device (1) is connected to the outlet of the production well, and the gas outlet of the gas-solid separation device (1) is connected to the shell-side inlet of the heat exchanger (3); the shell-side outlet of the heat exchanger (3) is connected to the inlet of the gas-liquid separation device (4), and the liquid phase outlet of the gas-liquid separation device (4) is connected to the inlet of the oil-water separation device (6); the oil phase outlet of the oil-water separation device (6) is connected to the inlet of the oil storage tank (7).

[0008] Furthermore, the solid phase outlet of the gas-solid separation device (1) is connected to the inlet of the coal ash storage tank (2), and the separated coal ash can be used for drilling backfill; the gas phase outlet of the gas-liquid separation device (4) is connected to the inlet of the desulfurization and decarbonization device (5), and part of the CO2 from the desulfurization and decarbonization device (5) enters the pressurization device (9), and the other part is injected into the combustion air zone for sealing or for use in the petroleum industry; the syngas from the flue gas and pyrolysis gas after passing through the desulfurization and decarbonization device (5) can be used as a chemical synthesis raw material, for extracting pure hydrogen, synthesizing natural gas, and synthesizing ammonia, etc.

[0009] Furthermore, the water phase outlet of the oil-water separation device (6) is connected to the inlet of the water treatment device (8); the water treated by the water treatment device (8) and the makeup water (used during start-up) enter the tube side of the heat exchanger (3), and the tube side outlet of the heat exchanger (3) is connected to the high-pressure water injection pipe (13) of the vertical shaft (12).

[0010] Furthermore, the combustion aid supply system includes a pressurizing device (9), a mixer (10), and an air separation unit (11); the CO2 from the desulfurization and decarbonization unit (5) is pressurized by the pressurizing device (9) and then enters the mixer (10); the O2 outlet of the air separation unit (11) is connected to the inlet of the mixer (10), and the N2 produced by the air separation unit (11) can be sold as liquid nitrogen or used as raw material gas for ammonia synthesis; the outlet of the mixer (10) is connected to the inlet of the injection well.

[0011] Furthermore, the high-temperature heat pipe assembly (16) is equipped with multiple high-temperature heat pipes arranged according to the heat load. The upper section of the high-temperature heat pipe assembly (16) is a condensation section (16-1), the lower section is an evaporation section (16-2), and an annular sealing plug (15) is provided in the middle to prevent the flue gas in the lower section from entering the evaporation section. The top of the high-temperature heat pipe assembly (16) is equipped with a sealing plug (14). The high-pressure water injection pipe (13) is arranged at the bottom of the condensation section in the high-temperature heat pipe assembly (16). The top of the high-temperature heat pipe assembly (16) is equipped with a temperature measuring hole (16-3), and the bottom of the condensation section is equipped with a water vapor outlet (16-5). The bottom of the high-temperature heat pipe assembly (16) is equipped with a dust settling chamber, and a high-temperature heat pipe assembly support component (17) is provided in the dust settling chamber.

[0012] Furthermore, the horizontal well is equipped with an ignition device (19), which is a gas injection point controllable retraction type.

[0013] Furthermore, the manufacturing process of this system is as follows:

[0014] a. A vertical shaft (12) is developed using vertical drilling. A high-temperature heat pipe assembly (16) is arranged in the coal seam of the shaft (12). The bottom is supported by a support (17). The high-temperature heat pipe assembly (16) is divided into a lower evaporation section (16-2) and an upper condensation section (16-1) by an annular sealing plug (15). A sealing plug (14) is arranged at the top of the high-temperature heat pipe assembly (16) to prevent the steam of the condensation section (16-1) of the high-temperature heat pipe assembly from entering the upper second-stage drilling casing (12-4).

[0015] b. With the vertical shaft (12) as the center, multiple vertical shafts are arranged around it (the depth of the vertical shaft depends on the position of the horizontal shaft to be arranged), and the included angle between adjacent vertical shafts is 15° to 45°.

[0016] c. Drill two parallel horizontal wells of different depths into the casing of the second drilling section of each vertical well (12) using vertical directional drilling. The horizontal wells are all in the coal seam, which is divided into four layers according to thickness: the bottom layer is the first layer, and the layers above are the second, third and fourth layers. The two horizontal wells of each vertical well are located on different coal seams: the horizontal well (L1-1) of the vertical well (V1) is in the first layer of the coal seam, and the horizontal well (L1-4) is in the fourth layer of the coal seam; the horizontal well (L2-2) of the vertical well (V2) is in the second layer of the coal seam, and the horizontal well (L2-3) is in the third layer of the coal seam; the horizontal well (L3-1) of the vertical well (V3) is in the first layer of the coal seam, and the horizontal well (L3-4) is in the fourth layer of the coal seam. The arrangement of the horizontal wells continues in this pattern.

[0017] d. Except for horizontal wells (L1-1), horizontal wells (L2-2), and horizontal wells (L2-3), all other horizontal wells are sealed with plugs.

[0018] e. The O2 prepared by the air separation unit (11) and the purchased CO2 (start-up section) are mixed by the mixer (10) to form an oxygen-enriched combustion aid. The oxygen-enriched combustion aid is transported through the vertical well (V1) to the ignition device of the horizontal well (L1-1) to ignite the coal seam. The high-temperature flue gas (mainly CO2) generated by combustion enters the evaporation section (16-2) of the high-temperature heat pipe group. When the temperature reaches the start-up conditions of the high-temperature heat pipe, the high-temperature heat pipe quickly transfers the heat of the high-temperature flue gas to the condensation section (16-1) of the high-temperature heat pipe group, so that the water is heated into high-pressure superheated steam.

[0019] f. The high-temperature flue gas after heat exchange enters the horizontal well (L2-2), where the heat of the high-temperature flue gas (700℃) is used to pyrolyze the coal seam in the horizontal well (L2-2), producing pyrolysis gas and tar. High-pressure superheated steam heated by the high-temperature heat pipe group is transported to the horizontal well (L2-3) to pyrolyze the coal seam, producing pyrolysis gas and tar. The flue gas, steam, pyrolysis gas and tar from the horizontal wells (L2-2) and (L2-3) are transported to the oil and gas processing and collection system through the vertical well (V2). After purification, coal ash (used for drilling backfill), pyrolysis gas (mainly composed of H2, CO, CH4, with high calorific value), tar, condensate (part of the condensate is treated and heat exchanged before being transported to the condensation section of the high-temperature heat pipe group for heat exchange and then pyrolyzing the coal in the next horizontal well; the remaining condensate can be used as garden or industrial water), and CO2 (part of which is used as a combustion aid and part of which is injected into the combustion zone / pyrolysis zone for storage).

[0020] g. After the coal seams in horizontal wells (L2-2) and (L2-3) have been pyrolyzed, all horizontal wells except for those in horizontal wells (L1-4), (L2-2), and (L3-1) should be sealed with plugs.

[0021] h. Using the vertical well (V2) as the combustion aid injection well, the oxygen-enriched combustion aid is delivered to the ignition device of the horizontal well (L2-2) to ignite the coal seam. The high-temperature flue gas (mainly CO2) generated by combustion enters the evaporation section (16-2) of the high-temperature heat pipe group. When the temperature reaches the start-up conditions of the high-temperature heat pipe, the high-temperature heat pipe quickly transfers the heat of the high-temperature flue gas to the condensation section (16-1) of the high-temperature heat pipe group, so that the water is heated into high-pressure superheated steam.

[0022] i. After heat exchange, the high-temperature flue gas enters the horizontal well (L3-1). The heat of the high-temperature flue gas (700℃) is used to pyrolyze the coal seam in the horizontal well (L3-1). The resulting pyrolysis gas and tar are transported to the oil and gas processing and collection system through the vertical well (V3) along with the flue gas. High-pressure superheated steam heated by the high-temperature heat pipe group is transported to the horizontal well (L1-4) to pyrolyze the coal seam. The resulting pyrolysis gas and tar are transported to the oil and gas processing and collection system through the vertical well (V1).

[0023] j. Following the operating procedures and technical principles described in d to i above, continue to use high-temperature flue gas and high-pressure superheated steam to pyrolyze the coal seams in the remaining horizontal wells.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention utilizes oxygen and carbon dioxide as combustion aids to achieve the combustion and pyrolysis process of underground coal. Combined with the constant-temperature, high-efficiency heat transfer characteristics of high-temperature heat pipes, it enables efficient pyrolysis of underground coal seams. This technology not only yields high-quality tar and high-calorific-value pyrolysis gas but also requires only a small amount of external energy.

[0026] 2. In this invention, the high-temperature flue gas after combustion exchanges heat with the high-temperature heat pipe assembly before pyrolyzing the coal seam, which improves the utilization efficiency of the high-temperature flue gas and reduces energy loss. At the same time, the pyrolysis gas and tar products generated are mixed with the products of water vapor pyrolysis and output from a vertical well. This increases the total gas transmission volume and heat concentration, ensuring that tar and water vapor are discharged from the production well in gaseous form. This not only guarantees the tar yield but also significantly reduces pollution to the underground environment.

[0027] 3. This invention mixes a portion of the CO2 produced by the desulfurization and decarbonization device with O2 to serve as a combustion aid for coal seam combustion, while the remainder is transported to the combustion air zone / pyrolysis zone to achieve CO2 sequestration, effectively reducing carbon dioxide emissions.

[0028] 4. The solid residue separated by the gas-solid separation device of the present invention can be used for drilling backfilling, effectively reducing the discharge of solid waste.

[0029] 5. The present invention has a dust settling chamber at the bottom of the high-temperature heat pipe assembly to prevent dust carried by the high-temperature flue gas from clogging the unreacted horizontal well. Attached Figure Description

[0030] Figure 1 This invention presents a schematic diagram of a high-temperature heat pipe-based in-situ underground combustion and pyrolysis oil and gas production system and process for oil-rich coal, with a vertical well (V1) as the gas injection well.

[0031] Figure 2 This invention presents a schematic diagram of a high-temperature heat pipe-based in-situ underground combustion and pyrolysis oil and gas production system and process for oil-rich coal, with a vertical well (V2) as the gas injection well.

[0032] Figure 3 This is a schematic diagram of the high-temperature heat pipe assembly of the present invention;

[0033] Figure 4 This is a three-dimensional drilling layout diagram of a high-temperature heat pipe-based in-situ underground combustion and pyrolysis oil and gas production system and process for oil-rich coal.

[0034] Figure 5 This is a schematic diagram of the drilling layout of multiple pyrolysis units in a high-temperature heat pipe-based in-situ underground combustion and pyrolysis oil and gas production system and process for oil-rich coal.

[0035] Figure 6This is a schematic flowchart of a system and process for in-situ underground combustion and pyrolysis oil and gas production of oil-rich coal based on high-temperature heat pipes (the heat carrier gas is water vapor).

[0036] Figure 7 This is a schematic flowchart of a system and process for in-situ underground combustion and pyrolysis oil and gas production of oil-rich coal based on high-temperature heat pipes (the heat carrier gas is CO2). In the diagram: 1-Gas-solid separation unit; 2-Coal ash storage tank; 3-Heat exchanger; 4-Gas-liquid separation unit; 5-Desulfurization and decarbonization unit; 6-Oil-water separation unit; 7-Oil storage tank; 8-Water treatment unit; 9-Pressure unit; 10-Mixer; 11-Air separation unit; 12-Shaft; 12-1-First-stage drilling; 12-2-First-stage drilling casing; 12-3-Second-stage drilling; 12-4-Second-stage drilling casing; 13-High pressure 14-Water injection pipe; 15-Sealing plug; 16-Annular sealing plug; 16-High temperature heat pipe assembly; 16-1-High temperature heat pipe assembly condensation section; 16-2-High temperature heat pipe assembly evaporation section; 16-3-High temperature heat pipe assembly temperature measuring hole; 16-4-High temperature heat pipe; 16-5-High temperature heat pipe assembly steam outlet; 17-Support component; 18-Sealing plug; 19-Ignition device; V1~V16-Vertical well; L1-1~L16-3-Horizontal well. Detailed Implementation

[0037] To better understand the technical essence and beneficial effects of the present invention, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] Combination Figure 1 , Figure 2 , Figure 3The present invention discloses a high-temperature heat pipe-based in-situ underground combustion and pyrolysis oil and gas production system for oil-rich coal, comprising a vertical shaft (12) drilled in the oil-rich coal seam to be pyrolyzed. The vertical shaft (12) has a first-stage well (12-1) drilled at the surface and a first-stage well casing (12-2) installed. Cement is filled between the outer wall of the first-stage well casing (12-2) and the inner wall of the first-stage well (12-1) for sealing and reinforcement. A second-stage well (12-3) is drilled within the first-stage well, and the second-stage well (12-3) continues until… At the bottom of the coal seam, a casing (12-4) is installed from top to bottom within the second-stage drilling well (12-3) until the bottom of the coal seam. The outer wall of the casing (12-4) and the interior of the second-stage drilling well (12-3) are sealed and reinforced with refractory cement. A high-temperature heat pipe assembly is installed inside the casing of the second-stage drilling well within the coal seam. Multiple vertical wells are arranged around a circle centered on the vertical shaft (12). The vertical wells are evenly distributed on the circumference, with the included angle between adjacent vertical wells being [missing information]. 15°~45°; Two parallel horizontal wells of different depths are drilled from each vertical well into the casing of the second drilling of the vertical well (12). The horizontal wells are all in the coal seam, which is divided into four layers according to thickness: the bottom layer is the first layer, and the layers above are the second, third and fourth layers; The two horizontal wells of each vertical well are located on different coal seams: the horizontal well (L1-1) of the vertical well (V1) is in the first layer of the coal seam, the horizontal well (L1-4) is in the fourth layer of the coal seam, and the horizontal well (L1-4) of the vertical well (V2) is in the fourth layer of the coal seam. The horizontal well (L2-2) is in the second layer of the coal seam, the horizontal well (L2-3) is in the third layer of the coal seam, and the horizontal well (L3-1) of the vertical well (V3) is in the first layer of the coal seam, and the horizontal well (L3-4) is in the fourth layer of the coal seam. The arrangement of the horizontal wells continues in this pattern. The state of each vertical well is different in different sections. Some are used as combustion-supporting agent injection wells with their inlets connected to the combustion-supporting agent supply system, some are used as production wells with their outlets connected to the oil and gas processing and collection system, and the remaining vertical wells are in a closed state.

[0039] The oil and gas treatment and collection system includes a gas-solid separation device (1), a coal ash storage tank (2), a heat exchanger (3), a gas-liquid separation device (4), a desulfurization and decarbonization device (5), an oil-water separation device (6), an oil storage tank (7), and a water treatment device (8). The inlet of the gas-solid separation device (1) is connected to the outlet of the production well, and the gas outlet of the gas-solid separation device (1) is connected to the shell-side inlet of the heat exchanger (3). The shell-side outlet of the heat exchanger (3) is connected to the inlet of the gas-liquid separation device (4), and the liquid phase outlet of the gas-liquid separation device (4) is connected to the inlet of the oil-water separation device (6). The oil phase outlet of the oil-water separation device (6) is connected to the inlet of the oil storage tank (7).

[0040] The solid phase outlet of the gas-solid separation device (1) is connected to the inlet of the coal ash storage tank (2), and the separated coal ash can be used for drilling backfilling; the gas phase outlet of the gas-liquid separation device (4) is connected to the inlet of the desulfurization and decarbonization device (5), and part of the CO2 from the desulfurization and decarbonization device (5) enters the pressurization device (9), and the other part is injected into the combustion air zone / pyrolysis zone for sealing or for use in the petroleum industry; the syngas from the flue gas and pyrolysis gas after passing through the desulfurization and decarbonization device (5) can be used as a chemical synthesis raw material, for extracting pure hydrogen, synthesizing natural gas, and synthesizing ammonia, etc.

[0041] The water phase outlet of the oil-water separator (6) is connected to the inlet of the water treatment device (8); the water treated by the water treatment device (8) and the makeup water (used during start-up) enter the tube side of the heat exchanger (3), and the tube side outlet of the heat exchanger (3) is connected to the high-pressure water injection pipe (13) of the vertical shaft (12).

[0042] The combustion aid supply system includes a pressurizing device (9), a mixer (10), and an air separation unit (11); the CO2 from the desulfurization and decarbonization unit (5) is pressurized by the pressurizing device (9) and then enters the mixer (10); the O2 outlet of the air separation unit (11) is connected to the inlet of the mixer (10), and the N2 produced by the air separation unit (11) can be sold as liquid nitrogen or used as raw material gas for ammonia synthesis; the outlet of the mixer (10) is connected to the inlet of the injection well.

[0043] The high-temperature heat pipe assembly (16) has multiple high-temperature heat pipes arranged according to the heat load. The upper section of the high-temperature heat pipe assembly (16) is the condensation section (16-1), the lower section is the evaporation section (16-2), and an annular sealing plug (15) is provided in the middle to prevent the flue gas in the lower section from entering the evaporation section. The top of the high-temperature heat pipe assembly (16) is provided with a sealing plug (14). The high-pressure water injection pipe (13) is arranged at the bottom of the condensation section in the high-temperature heat pipe assembly (16). The top of the high-temperature heat pipe assembly (16) is provided with a temperature measuring hole (16-3), and the bottom of the condensation section is provided with a water vapor outlet (16-5). The bottom of the high-temperature heat pipe assembly (16) is provided with a dust settling chamber, and a high-temperature heat pipe assembly support (17) is provided in the dust settling chamber.

[0044] The horizontal drilling well is equipped with an ignition device (19), which is a gas injection point controllable retraction type.

[0045] Based on the structure of the above-mentioned oil-rich coal in-situ underground combustion and pyrolysis oil recovery synergistic system, the production process steps of this system are as follows:

[0046] a. A vertical shaft (12) is developed using vertical drilling. A high-temperature heat pipe assembly (16) is arranged in the coal seam of the shaft (12). The bottom is supported by a support (17). The high-temperature heat pipe assembly (16) is divided into a lower evaporation section (16-2) and an upper condensation section (16-1) by an annular sealing plug (15). A sealing plug (14) is arranged at the top of the high-temperature heat pipe assembly (16) to prevent the steam of the condensation section (16-1) of the high-temperature heat pipe assembly from entering the upper second-stage drilling casing (12-4).

[0047] b. With the vertical shaft (12) as the center, multiple vertical shafts are arranged around it (the depth of the vertical shaft depends on the position of the horizontal shaft to be arranged), and the included angle between adjacent vertical shafts is 15° to 45°.

[0048] c. Drill two parallel horizontal wells of different depths into the casing of the second drilling section of each vertical well (12) using vertical directional drilling. The horizontal wells are all in the coal seam, which is divided into four layers according to thickness: the bottom layer is the first layer, and the layers above are the second, third and fourth layers. The two horizontal wells of each vertical well are located on different coal seams: the horizontal well (L1-1) of the vertical well (V1) is in the first layer of the coal seam, and the horizontal well (L1-4) is in the fourth layer of the coal seam; the horizontal well (L2-2) of the vertical well (V2) is in the second layer of the coal seam, and the horizontal well (L2-3) is in the third layer of the coal seam; the horizontal well (L3-1) of the vertical well (V3) is in the first layer of the coal seam, and the horizontal well (L3-4) is in the fourth layer of the coal seam. The arrangement of the horizontal wells continues in this pattern.

[0049] d. Except for horizontal wells (L1-1), horizontal wells (L2-2), and horizontal wells (L2-3), all other horizontal wells are sealed with plugs.

[0050] e. The O2 prepared by the air separation unit (11) and the purchased CO2 (start-up section) are mixed by the mixer (10) to form an oxygen-enriched combustion aid. The oxygen-enriched combustion aid is transported through the vertical well (V1) to the ignition device of the horizontal well (L1-1) to ignite the coal seam. The high-temperature flue gas (mainly CO2) generated by combustion enters the evaporation section (16-2) of the high-temperature heat pipe group. When the temperature reaches the start-up conditions of the high-temperature heat pipe, the high-temperature heat pipe quickly transfers the heat of the high-temperature flue gas to the condensation section (16-1) of the high-temperature heat pipe group, so that the water is heated into high-pressure superheated steam.

[0051] f. The high-temperature flue gas after heat exchange enters the horizontal well (L2-2), where the heat of the high-temperature flue gas (700℃) is used to pyrolyze the coal seam in the horizontal well (L2-2), producing pyrolysis gas and tar. High-pressure superheated steam heated by the high-temperature heat pipe group is transported to the horizontal well (L2-3) to pyrolyze the coal seam, producing pyrolysis gas and tar. The flue gas, steam, pyrolysis gas and tar from the horizontal wells (L2-2) and (L2-3) are transported to the oil and gas processing and collection system through the vertical well (V2). After purification, coal ash (used for drilling backfill), pyrolysis gas (mainly composed of H2, CO, CH4, with high calorific value), tar, condensate (part of the condensate is treated and heat exchanged before being transported to the condensation section of the high-temperature heat pipe group for heat exchange and then pyrolyzing the coal in the next horizontal well; the remaining condensate can be used as garden or industrial water), and CO2 (part of which is used as a combustion aid and part of which is injected into the combustion zone / pyrolysis zone for storage).

[0052] g. After the coal seams in horizontal wells (L2-2) and (L2-3) have been pyrolyzed, all horizontal wells except for those in horizontal wells (L1-4), (L2-2), and (L3-1) should be sealed with plugs.

[0053] h. Using the vertical well (V2) as the combustion aid injection well, the oxygen-enriched combustion aid is delivered to the ignition device of the horizontal well (L2-2) to ignite the coal seam. The high-temperature flue gas (mainly CO2) generated by combustion enters the evaporation section (16-2) of the high-temperature heat pipe group. When the temperature reaches the start-up conditions of the high-temperature heat pipe, the high-temperature heat pipe quickly transfers the heat of the high-temperature flue gas to the condensation section (16-1) of the high-temperature heat pipe group, so that the water is heated into high-pressure superheated steam.

[0054] i. After heat exchange, the high-temperature flue gas enters the horizontal well (L3-1). The heat of the high-temperature flue gas (700℃) is used to pyrolyze the coal seam in the horizontal well (L3-1). The resulting pyrolysis gas and tar are transported to the oil and gas processing and collection system through the vertical well (V3) along with the flue gas. High-pressure superheated steam heated by the high-temperature heat pipe group is transported to the horizontal well (L1-4) to pyrolyze the coal seam. The resulting pyrolysis gas and tar are transported to the oil and gas processing and collection system through the vertical well (V1).

[0055] j. Following the operating procedures and technical principles described in d to i above, continue to use high-temperature flue gas and high-pressure superheated steam to pyrolyze the coal seams in the remaining horizontal wells.

[0056] Figure 4 This is a three-dimensional drilling layout diagram of a high-temperature heat pipe-based in-situ underground combustion and pyrolysis oil and gas production synergistic system and process for oil-rich coal, with an included angle of 22.5° between adjacent vertical wells. Figure 5This is a schematic diagram of the drilling layout of multiple pyrolysis units for a high-temperature heat pipe-based in-situ underground combustion and pyrolysis oil and gas production system and process for oil-rich coal. The layout of vertical wells is optimized, and some vertical wells can be used as gasification feed or production wells for multiple horizontal wells, which reduces the drilling cost of vertical wells, makes more rational and full use of coal resources, and reduces resource waste.

[0057] Example 1

[0058] This embodiment combines Figure 6 A more specific example of a system and process for in-situ underground combustion and pyrolysis-based oil and gas recovery of oil-rich coal based on high-temperature heat pipes is provided. In this embodiment, the combustion aid is oxygen-enriched coal with a volume ratio of 40% O2 (CO2 volume ratio of 60%). The heat transfer medium heated by the high-temperature heat pipe assembly is water vapor, as detailed below:

[0059] Oxygen produced by the air separation unit (1120 Nm) 3 / h) and part of the CO2 (1680Nm³) generated by the desulfurization and decarbonization unit 3 After mixing, the coal is fed from the vertical shaft (V1) to the horizontal shaft (L1-4) for in-situ combustion. The coal consumption is 700 kg / h, and the high-temperature flue gas produced by combustion is 2.0 MPa, 1000℃, and 3050 Nm³. 3 The water (2.0 MPa, 80°C, 500 kg / h) is transported to the evaporation section of a high-temperature heat pipe unit (500 kW power). The high-temperature heat pipe unit rapidly transfers the heat of the high-temperature flue gas to the condensation section, heating the water (2.0 MPa, 80°C, 500 kg / h) into high-pressure superheated steam (700°C). The flue gas after heat exchange (2.0 MPa, 750°C, 3050 Nm³ / h) is then condensed into high-pressure superheated steam (700°C). 3 High-pressure superheated steam (2.0 MPa, 700°C, 500 kg / h) heated by high-temperature heat pipes is transported to horizontal well (I2-3) to pyrolyze the coal seam. The pyrolysis rate is 2000 kg / h, and the temperature of the mixture of flue gas and pyrolysis gas after pyrolysis is 400°C. High-pressure superheated steam (2.0 MPa, 700°C, 500 kg / h) heated by high-temperature heat pipes is transported to horizontal well (I2-3) to pyrolyze the coal seam. The pyrolysis rate is 270 kg / h, producing pyrolysis gas and tar.

[0060] The pyrolysis gas and tar from horizontal wells (L2-2) and (L2-3) are mixed in vertical well (V2) and discharged from the wellhead of vertical well (V2). The temperature of the mixed gas (containing dust) at the wellhead is higher than 160°C and enters the cyclone separator. Dust and coal ash are discharged from the bottom of the cyclone separator, and the mixed gas comes out from the top of the cyclone separator and enters the first heat exchanger to exchange heat with the water coming out of the second heat exchanger. After heat exchange, part of the water (2.0 MPa, 80°C, 500 kg / h) enters the high-temperature heat pipe group from vertical well (12). The mixed gas after heat exchange is transported to the gas-liquid separator, and the oil-water mixture is discharged from the bottom and enters the oil-water separator, which can produce 170 kg / h of tar and 800 kg / h of condensate. The condensate is treated by the water treatment device and then transported to the circulating water pool. The circulating water in the pool, pressurized by a high-pressure pump, is used as a coolant in the heat exchangers of the surface unit. Most of the high-temperature water (80℃) after heat exchange returns to the circulating water pool, while the 500kg / h high-temperature water is further pressurized to 2.0MPa and injected into the condensation section of the high-temperature heat pipe assembly in the vertical shaft. After heat exchange, it generates high-temperature, high-pressure superheated steam, which serves as the heat transfer medium for coal pyrolysis in the horizontal shaft. The mixed gas from the gas-liquid separator enters the second heat exchanger to exchange heat with water before being transported to the desulfurization and decarbonization unit, where 2600Nm³ of carbon dioxide is separated. 3 / h, pyrolysis gas (mainly CO, H2, CH4) 360Nm 3 The separated hydrogen sulfide is produced at a rate of / h, and continues to synthesize sulfur or sulfuric acid. The yield of hydrogen sulfide is related to the sulfur content of the raw coal; the higher the sulfur content, the more hydrogen sulfide is produced. A portion of the separated CO2 (1680 Nm³) is also produced. 3 / h) and pure oxygen (1120Nm) from the air separation unit 3 The CO2 is mixed with oxygen-rich gas (approximately 100 Nm³ / h) and used as a combustion aid for in-situ coal combustion. The remaining CO2 is injected into the air-fuel pyrolysis zone for carbon sequestration, reducing carbon emissions by 920 Nm³. 3 The system produces CO2 per hour. This CO2 can also be supplied to the oilfield industry as a secondary recovery displacement agent. Pyrolysis gas (mainly composed of CO, H2, and CH4) can be used for methanol synthesis, natural gas synthesis, IGCC power generation, and ammonia synthesis. The N2 produced by the air separation unit can be used for ammonia synthesis.

[0061] Table 1. Process parameters for in-situ underground combustion and pyrolysis oil and gas recovery of oil-rich coal based on high-temperature heat pipes (the heat transfer gas for the high-temperature heat pipe group is steam).

[0062]

[0063] Example 2

[0064] This embodiment combines Figure 7A more specific system and process for in-situ underground combustion and pyrolysis oil and gas recovery of oil-rich coal based on high-temperature heat pipes is provided. In this embodiment, the combustion aid is oxygen-enriched (60% CO2 by volume) with 40% O2 by volume. The heat transfer medium heated by the high-temperature heat pipe assembly is CO2, as detailed below:

[0065] Oxygen produced by the air separation unit (1120 Nm) 3 / h) and part of the CO2 (1680Nm³) generated by the desulfurization and decarbonization unit 3 After mixing, the coal is fed from the vertical shaft (V1) to the horizontal shaft (L1-4) for in-situ combustion. The coal consumption is 700 kg / h, and the high-temperature flue gas produced by combustion is 2.0 MPa, 1000℃, and 3050 Nm³. 3 The gas is transported at a rate of / h to the evaporation section of a high-temperature heat pipe assembly (power of 500kW). The high-temperature heat pipe quickly transfers the heat from the high-temperature flue gas to the condensation section of the high-temperature heat pipe assembly, converting CO2 (2.0Mpa, 80℃, 1350Nm³) into heat. 3 The flue gas is heated to 700℃ ( / h). After heat exchange, the flue gas (2.0MPa, 750℃, 3050Nm³) 3 The coal is fed into the horizontal well (L2-2) at a rate of 2000 kg / h, utilizing the heat of the high-temperature flue gas (750℃) to pyrolyze the coal seam within the well. The temperature of the flue gas and the pyrolyzed mixture after pyrolysis is 400℃. CO2 (2.0 MPa, 700℃, 1350 Nm³) is heated by the high-temperature heat pipe assembly. 3 The coal is transported to the horizontal well (L2-3) at a rate of 780 kg / h to pyrolyze the coal seam, producing pyrolysis gas and tar.

[0066] The pyrolysis gas and tar from horizontal wells (L2-2 and L2-3) are mixed in vertical well (V2) and discharged from the wellhead. The temperature of the mixed gas (containing dust) at the wellhead is higher than 160℃ and enters the cyclone separator. The dust and coal ash are discharged from the bottom of the cyclone separator, and the mixed gas exits from the top of the cyclone separator and enters the first heat exchanger to exchange heat with some of the CO2 after desulfurization and decarbonization. After heat exchange, the CO2 (2.0 MPa, 80℃, 1350 Nm³) is obtained. 3 The gas enters the condensing section of the high-temperature heat pipe group from the vertical shaft (12) and generates high-temperature and high-pressure CO2 after heat exchange, which serves as the heat transfer medium for coal pyrolysis in the horizontal well. The mixed gas after heat exchange is transported to the gas-liquid separator. The oil-water mixture is discharged from the bottom and enters the oil-water separator, which can produce 210 kg / h of tar and 350 kg / h of condensate. The condensate is neutralized and treated by the water treatment device and then transported to the circulating water pool. The water in the circulating water pool is pressurized by the high-pressure water pump and then used as a coolant for the heat exchangers in the surface equipment. The mixed gas from the gas-liquid separator enters the second heat exchanger and exchanges heat with water before being transported to the desulfurization and decarbonization device to separate 4000 Nm of carbon dioxide.3 / h, pyrolysis gas (mainly CO, H2, CH4) 440Nm 3 / h, the separated hydrogen sulfide continues to synthesize sulfur or sulfuric acid. The yield of hydrogen sulfide is related to the sulfur content in the raw coal; the higher the sulfur content, the more hydrogen sulfide is produced. The separated CO2 is divided into three parts, one part (1680 Nm³) 3 / h) and pure oxygen (1120Nm) from the air separation unit 3 / h) are mixed to form an oxygen-rich gas, which is used as a combustion aid for in-situ coal combustion, a portion of which (1350Nm 3 / h) The heat transfer medium of the high-temperature heat pipe assembly is used, and the remaining portion is injected into the combustion / pyrolysis zone for carbon sequestration, which can reduce carbon emissions (970Nm). 3 The system produces CO2 (per hour), which can also be supplied to the oilfield industry as a secondary recovery displacement agent. Pyrolysis gas (mainly composed of CO, H2, and CH4) can be used to synthesize methanol, synthetic natural gas, IGCC power generation, and ammonia. N2 produced by the air separation unit can be used for ammonia synthesis.

[0067] Table 2. Process parameters for in-situ underground combustion and pyrolysis oil and gas recovery of oil-rich coal based on high-temperature heat pipes (the heat transfer gas for the high-temperature heat pipe group is CO2).

[0068]

Claims

1. A system and process for synergistic oil and gas recovery from in-situ underground combustion and pyrolysis of oil-rich coal based on high-temperature heat pipes, characterized in that, This includes a vertical shaft (12) drilled in a coal seam rich in oil to be pyrolyzed. The vertical shaft (12) has a first-stage well (12-1) drilled at the surface and a first-stage well casing (12-2) installed. Cement is filled between the outer wall of the first-stage well casing (12-2) and the inner wall of the first-stage well (12-1) for sealing and reinforcement. A second-stage well (12-3) is drilled within the first-stage well, extending to the bottom of the coal seam. Within the second-stage well (12-3), a structure is installed from top to bottom. The casing (12-4) of the second-stage drilling extends to the bottom of the coal seam. The outer wall of the casing (12-4) and the interior of the second-stage drilling (12-3) are sealed and reinforced with refractory cement. A high-temperature heat pipe assembly is installed inside the casing of the second-stage drilling in the coal seam. Multiple vertical wells are arranged around a central shaft (12). These vertical wells are evenly distributed on the circumference, with an angle of 15° to 45° between adjacent vertical wells. The casing is then drilled from each vertical well. Two parallel horizontal wells of different depths are drilled into the casing of the second drilling section of the vertical shaft (12). The horizontal wells are both in the coal seam, which is divided into four layers according to thickness: the bottom layer is the first layer, and the layers above are the second, third and fourth layers. The two horizontal wells of each vertical shaft are located on different coal seams: the horizontal well (L1-1) of the vertical shaft (V1) is in the first layer of the coal seam, and the horizontal well (L1-4) is in the fourth layer of the coal seam; the horizontal well (L2-2) of the vertical shaft (V2) is in the second layer of the coal seam, and the horizontal well (L2-3) is in the third layer of the coal seam; the horizontal well (L3-1) of the vertical shaft (V3) is in the first layer of the coal seam, and the horizontal well (L3-4) is in the fourth layer of the coal seam. The arrangement of the horizontal wells continues in this pattern. The state of each vertical well is different in different sections. One is used as a combustion aid injection well with its inlet connected to the combustion aid supply system, and another is used as a production well with its outlet connected to the oil and gas processing and collection system. The remaining vertical wells are in a closed state.

2. The system and process for in-situ underground combustion and pyrolysis oil and gas recovery based on high-temperature heat pipes according to claim 1, characterized in that, The oil and gas treatment and collection system includes a gas-solid separation device (1), a coal ash storage tank (2), a heat exchanger (3), a gas-liquid separation device (4), a desulfurization and decarbonization device (5), an oil-water separation device (6), an oil storage tank (7), and a water treatment device (8). The inlet of the gas-solid separation device (1) is connected to the outlet of the production well, and the gas outlet of the gas-solid separation device (1) is connected to the shell-side inlet of the heat exchanger (3). The shell-side outlet of the heat exchanger (3) is connected to the inlet of the gas-liquid separation device (4), and the liquid phase outlet of the gas-liquid separation device (4) is connected to the inlet of the oil-water separation device (6). The oil phase outlet of the oil-water separation device (6) is connected to the inlet of the oil storage tank (7).

3. The system and process for in-situ underground combustion and pyrolysis oil and gas recovery based on high-temperature heat pipes according to claim 2, characterized in that, The solid phase outlet of the gas-solid separation device (1) is connected to the inlet of the coal ash storage tank (2), and the separated coal ash can be used for drilling backfill; the gas phase outlet of the gas-liquid separation device (4) is connected to the inlet of the desulfurization and decarbonization device (5), and part of the CO2 from the desulfurization and decarbonization device (5) enters the pressurization device (9), and the other part is injected into the combustion air area for sealing or for use in the petroleum industry; the syngas from the flue gas and pyrolysis gas after passing through the desulfurization and decarbonization device (5) can be used as a chemical synthesis raw material, for extracting pure hydrogen, synthesizing natural gas, and synthesizing ammonia, etc.

4. The system and process for in-situ underground combustion and pyrolysis oil and gas recovery based on high-temperature heat pipes according to claim 2, characterized in that, The water phase outlet of the oil-water separator (6) is connected to the inlet of the water treatment device (8); the water treated by the water treatment device (8) and the makeup water (used during start-up) enter the tube side of the heat exchanger (3), and the tube side outlet of the heat exchanger (3) is connected to the high-pressure water injection pipe (13) of the vertical shaft (12).

5. The system and process for in-situ underground combustion and pyrolysis oil and gas recovery based on high-temperature heat pipes according to claim 1, characterized in that, The combustion aid supply system includes a pressurizing device (9), a mixer (10), and an air separation unit (11); the CO2 from the desulfurization and decarbonization unit (5) is pressurized by the pressurizing device (9) and then enters the mixer (10); the O2 outlet of the air separation unit (11) is connected to the inlet of the mixer (10), and the N2 produced by the air separation unit (11) can be sold as liquid nitrogen or used as raw material gas for ammonia synthesis; the outlet of the mixer (10) is connected to the inlet of the injection well.

6. The system and process for synergistic oil and gas recovery from in-situ combustion and pyrolysis of oil-rich coal based on high-temperature heat pipes according to claim 1, characterized in that, The high-temperature heat pipe assembly (16) has multiple high-temperature heat pipes (16-4) arranged according to the heat load. The upper section of the high-temperature heat pipe assembly (16) is the condensation section (16-1), the lower section is the evaporation section (16-2), and an annular sealing plug (15) is provided in the middle to prevent the flue gas in the lower section from entering the evaporation section. The top of the high-temperature heat pipe assembly (16) is provided with a sealing plug (14). The high-pressure water injection pipe (13) is arranged at the bottom of the condensation section in the high-temperature heat pipe assembly (16). The top of the high-temperature heat pipe assembly (16) is provided with a temperature measuring hole (16-3), and the bottom of the condensation section is provided with a water vapor outlet (16-5). The bottom of the high-temperature heat pipe assembly (16) is provided with a dust settling chamber, and a high-temperature heat pipe assembly support component (17) is provided in the dust settling chamber.

7. The system and process for in-situ underground combustion and pyrolysis oil and gas recovery based on high-temperature heat pipes according to claim 1, characterized in that, The horizontal drilling well is equipped with an ignition device (19), which is a gas injection point controllable retraction type.

8. A system and process for synergistic oil and gas recovery from in-situ combustion and pyrolysis of oil-rich coal based on a high-temperature heat pipe, as described in claim 1, is characterized in that... The production process steps are as follows: a. A vertical shaft (12) is developed using vertical drilling. A high-temperature heat pipe assembly (16) is arranged in the coal seam of the shaft (12). The bottom is supported by a support (17). The high-temperature heat pipe assembly (16) is divided into a lower evaporation section (16-2) and an upper condensation section (16-1) by an annular sealing plug (15). A sealing plug (14) is arranged at the top of the high-temperature heat pipe assembly (16) to prevent the steam of the condensation section (16-1) of the high-temperature heat pipe assembly from entering the upper second-stage drilling casing (12-4). b. With the vertical shaft (12) as the center, multiple vertical shafts are arranged around it (the depth of the vertical shaft depends on the position of the horizontal shaft to be arranged), and the included angle between adjacent vertical shafts is 15° to 45°. c. Drill two parallel horizontal wells of different depths into the casing of the second drilling section of each vertical well (12) using vertical directional drilling. The horizontal wells are all in the coal seam, which is divided into four layers according to thickness: the bottom layer is the first layer, and the layers above are the second, third and fourth layers. The two horizontal wells of each vertical well are located on different coal seams: the horizontal well (L1-1) of the vertical well (V1) is in the first layer of the coal seam, and the horizontal well (L1-4) is in the fourth layer of the coal seam; the horizontal well (L2-2) of the vertical well (V2) is in the second layer of the coal seam, and the horizontal well (L2-3) is in the third layer of the coal seam; the horizontal well (L3-1) of the vertical well (V3) is in the first layer of the coal seam, and the horizontal well (L3-4) is in the fourth layer of the coal seam. The arrangement of the horizontal wells continues in this pattern. d. Except for horizontal wells (L1-1), horizontal wells (I2-2), and horizontal wells (L2-3), all other horizontal wells are sealed with plugs. e. The O2 prepared by the air separation unit (11) and the purchased CO2 (start-up section) are mixed by the mixer (10) to form an oxygen-enriched combustion aid. The oxygen-enriched combustion aid is transported through the vertical well (V1) to the ignition device of the horizontal well (L1-1) to ignite the coal seam. The high-temperature flue gas (mainly CO2) generated by combustion enters the evaporation section (16-2) of the high-temperature heat pipe group. When the temperature reaches the start-up conditions of the high-temperature heat pipe, the high-temperature heat pipe quickly transfers the heat of the high-temperature flue gas to the condensation section (16-1) of the high-temperature heat pipe group, so that the water is heated into high-pressure superheated steam. f. The high-temperature flue gas after heat exchange enters the horizontal well (L2-2), where the coal is pyrolyzed using the high-temperature flue gas (700℃), producing pyrolysis gas and tar. High-pressure superheated steam heated by the high-temperature heat pipe group is transported to the horizontal well (L2-3) to pyrolyze the coal, producing pyrolysis gas and tar. The flue gas, steam, pyrolysis gas, and tar from the horizontal wells (L2-2 and L2-3) are transported to the oil and gas processing and collection system through the vertical well (V2). After purification, coal ash (used for drilling backfill), pyrolysis gas (mainly composed of H2, CO, and CH4, with high calorific value), tar, condensate (part of the condensate is treated and heat exchanged before being transported to the condensation section of the high-temperature heat pipe group for heat exchange and then pyrolyzing the coal in the next horizontal well; the remaining condensate can be used as garden or industrial water), and CO2 (part of which is used as a combustion aid and part is injected into the combustion zone / pyrolysis zone for storage). g. After the coal seams in horizontal wells (L2-2) and (L2-3) have been pyrolyzed, all horizontal wells except for those in horizontal wells (L1-4), (L2-2), and (L3-1) should be sealed with plugs. h. Using the vertical well (V2) as the combustion aid injection well, the oxygen-enriched combustion aid is delivered to the ignition device of the horizontal well (L2-2) to ignite the coal seam. The high-temperature flue gas (mainly CO2) generated by combustion enters the evaporation section (16-2) of the high-temperature heat pipe group. When the temperature reaches the start-up conditions of the high-temperature heat pipe, the high-temperature heat pipe quickly transfers the heat of the high-temperature flue gas to the condensation section (16-1) of the high-temperature heat pipe group, so that the water is heated into high-pressure superheated steam. i. After heat exchange, the high-temperature flue gas enters the horizontal well (L3-1). The heat of the high-temperature flue gas (700℃) is used to pyrolyze the coal seam in the horizontal well (L3-1). The pyrolysis gas and tar produced are transported to the oil and gas processing and collection system through the vertical well (V3) along with the flue gas. The high-pressure superheated steam heated by the high-temperature heat pipe group is transported to the horizontal well (L1-4) to pyrolyze the coal seam. The pyrolysis gas and tar produced are transported to the oil and gas processing and collection system through the vertical well (V1). j. Following the operating procedures and technical principles described in d to i above, continue to use high-temperature flue gas and high-pressure superheated steam to pyrolyze the coal seams in the remaining horizontal wells.

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