In-situ pyrolysis system and method for compositely heating deep oil-rich coal seam

Abstract

The invention discloses an in-situ pyrolysis system and method for compositely heating a deep oil-rich coal seam. According to the in-situ pyrolysis system, a microwave phased array is arranged in a heating well, and a long-distance microwave heating system is arranged in a production well; boiler flue gas is subjected to permeation increasing and preheating treatment on a deep coal seam after being subjected to catalyst adding and high-frequency pulse injection, then high-power microwaves are used for achieving high-temperature pyrolysis of the coal seam, meanwhile, low-power microwaves are used for forming a heat preservation field for a production well, and through a convection preheating-microwave pyrolysis / heat preservation composite heating mode, the high-temperature pyrolysis of the coal seam is achieved. Efficient gradient utilization of low-grade industrial waste gas and high-grade electric energy is achieved, and condensation loss of tar in the lifting process is effectively reduced; accurate heating of the deep coal seam is achieved through the phased array microwave technology, and an effective way is provided for solving the technical problems that the deep oil-rich coal seam is low in heating efficiency, large in energy loss and difficult in product recovery; the pyrolysis efficiency and the economic benefit of the deep oil-rich coal seam are remarkably improved while resource utilization of the industrial waste gas is realized.

Description

Technical Field

[0001] This invention belongs to the field of energy technology and relates to a pyrolysis system and method for oil-rich coal, particularly to an in-situ pyrolysis system and method for deep oil-rich coal seams with composite heating. Background Technology

[0002] In-situ pyrolysis of oil-rich coal, a revolutionary technology proposed in recent years, ultimately aims to address the challenges of mining deep, difficult-to-mine coal seams. However, in-situ pyrolysis of deep coal seams faces unique technical challenges, and existing technologies have significant shortcomings in mining deep, oil-rich coal seams. Conventional conductive heating, while achieving rapid temperature rise, suffers from severe heat loss in deep formations, resulting in low energy utilization efficiency and difficulty in achieving uniform heating. Single convection heating is limited by the low permeability of deep coal seams, making it difficult to form effective thermal fluid circulation. While microwave heating has the advantage of strong penetration, energy attenuation and moisture interference in deep formations severely restrict its application effectiveness.

[0003] By employing a composite heating method of "convection preheating-microwave pyrolysis / insulation," industrial waste gas is first used for preheating to enhance permeability and remove formation moisture. Then, phased array microwave technology is used to achieve precise heating, which can significantly improve the pyrolysis efficiency of deep coal seams and reduce energy consumption costs. In addition, by establishing a microwave insulation field in the production well and combining it with real-time temperature monitoring and control, the condensation loss of tar during its migration to the surface is effectively avoided. Therefore, developing a composite heating in-situ pyrolysis system and method for deep oil-rich coal seams has significant practical implications. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an in-situ pyrolysis system and method for deep oil-rich coal seams with composite heating, which can significantly improve the pyrolysis efficiency and economic benefits of deep oil-rich coal seams while realizing the resource utilization of industrial waste gas.

[0005] This invention is achieved through the following technical solution: An in-situ pyrolysis system for deep oil-rich coal seams with composite heating. An in-situ pyrolysis system for heating deep oil-rich coal seams includes four heating wells and one production well, excavated vertically downwards from the ground into the deep oil-rich coal seam. The four heating wells are arranged in a quadrilateral shape, and the production well is located at the center of the quadrilateral. Temperature monitoring wells are excavated vertically downwards at the center of the lines connecting the wellheads of the four heating wells and the wellhead of the production well. Horizontal wells are excavated inside the deep oil-rich coal seam to connect the four heating wells and the production well. A phased array is arranged in the target deep oil-rich coal seam section within the heating wells. The phased array is connected to a high-power microwave generator on the ground via a waveguide. Several temperature monitoring points are installed around the production well. An insulation sleeve is laid around the production well. A long-distance microwave heating system is arranged along the entire production well and is connected to a low-power microwave generator on the ground via a waveguide. A gas-liquid separation device is installed at the wellhead of the production well, and a catalyst addition device, a high-frequency pulse injection system, and a flue gas pretreatment system are installed at the wellhead of the heating well. After pretreatment of low-grade industrial waste gas, a catalyst is added, and then the gas is injected into the deep oil-rich coal seam through a high-frequency pulse injection system along the heating well. The deep oil-rich coal seam is simultaneously subjected to permeation enhancement and preheating treatment. When the set preheating range is reached, the injection of high-temperature fluid is stopped, and the high-power microwave generator and low-power microwave generator on the ground are turned on. Under the action of phased array microwave heating, the deep oil-rich coal seam undergoes a high-temperature pyrolysis reaction. Under the action of long-distance microwave heating, a microwave insulation field is formed around the production well. The pyrolysis products flow out along the production well and enter the gas-liquid separation device to separate the tar and pyrolysis gas.

[0006] Preferably, the phased array consists of multiple independent radiating units, which efficiently receive microwave energy from a high-power microwave generator on the ground through waveguides, and the long-distance microwave heating system receives microwave energy from a low-power microwave generator on the ground and uniformly transmits it into the production well to form a heat preservation field.

[0007] Preferably, the outer insulation sleeve of the production well is a vacuum oil-barrier heat pipe.

[0008] Preferably, the target deep oil-rich coal seam is buried at a depth greater than 1000 m.

[0009] Preferably, the low-grade industrial waste gas is boiler flue gas, which is used to heat the deep oil-rich coal seam by convection to remove water, a naturally occurring strong microwave absorber in the strata.

[0010] Preferably, the catalyst is an organic iron salt / organic molybdenum salt.

[0011] The in-situ pyrolysis method for deep oil-rich coal seams using composite heating includes the following steps: 1) After pretreatment, the low-grade industrial waste gas enters the catalyst addition device to add catalyst. It is then injected into the deep oil-rich coal seam through the high-frequency pulse injection system along the heating well. The deep oil-rich coal seam is simultaneously permeable and preheated. After flowing inside the deep oil-rich coal seam, the flue gas flows out along the production well. 2) Once the set preheating range is reached, stop injecting high-temperature fluid and turn on the high-power microwave generator and low-power microwave generator on the ground. At this time, the deep oil-rich coal seam is transformed from convection heating to microwave heating. The deep oil-rich coal seam undergoes a high-temperature pyrolysis reaction. At the same time, a microwave insulation field is formed around the production well. The intensity of long-distance microwave heating is adjusted in real time through the feedback from the production well temperature monitoring well. 3) After the pyrolysis products flow out along the production well, they enter the gas-liquid separation device. The separated tar is collected in the oil storage tank, and the remaining pyrolysis gas enters the gas storage device.

[0012] Preferably, the preheating temperature set in step 2) is 200~300 ℃.

[0013] Preferably, in step 2), the product temperature is monitored in real time through temperature monitoring points so that the temperature near the production well is in the range of 350~400 ℃.

[0014] This invention deploys a microwave phased array within a heating well and sets up a long-distance microwave heating system in the production well. Boiler flue gas, after being treated with catalyst and injected with high-frequency pulses, is used to enhance the permeability and preheat the deep coal seam. High-power microwaves are then used to achieve high-temperature pyrolysis of the coal seam, while low-power microwaves are used to create a heat-preserving field in the production well. Through a composite heating method of "convection preheating - microwave pyrolysis / heat preservation," low-grade waste gas is first used for preheating, followed by high-grade electrical energy for high-temperature pyrolysis and heat preservation. This achieves efficient cascade utilization of low-grade industrial waste gas and high-grade electrical energy, effectively reducing tar condensation losses during the lifting process. The phased array microwave technology enables precise heating of deep coal seams, providing an effective solution to the technical challenges of low heating efficiency, high energy loss, and difficult product recovery in deep oil-rich coal seams.

[0015] The present invention has at least the following beneficial technical effects: (1) Phased array technology can accurately focus microwave energy on the target area. The waveguide efficiently receives microwave energy from the high-power microwave generator on the ground and focuses it accurately and intensely on the target coal seam area, reducing the large amount of energy dissipation when mining deep oil-rich coal seams and avoiding the problem of excessive heat loss in deep strata. This enables rapid and uniform heating and pyrolysis of coal seams buried at depths of more than 1,000 meters, effectively solving the thermal efficiency problem of mining deep oil-rich coal resources.

[0016] (2) When the pyrolysis products flow from the deep strata to the surface, the microwave insulation field arranged around the wellbore ensures that the product temperature is higher than its freezing point. The long-distance microwave heating system receives microwave energy from the low-power microwave generator on the ground and evenly transports it into the production well to form an insulation field, which greatly reduces flow resistance and product loss, ensures the continuity of production, and effectively solves the problem of product collection in the mining of deep oil-rich coal resources, thereby ensuring the continuity of production and tar recovery rate.

[0017] (3) Low-grade industrial waste heat is used for coal seam preheating and dehydration, and high-grade electrical energy is used for precise and efficient high-temperature pyrolysis, which greatly optimizes the energy structure and reduces operating costs.

[0018] (4) Using boiler flue gas as a preheating medium, industrial waste gas that requires additional energy consumption to be treated is converted into a heat carrier. This not only reduces the cost of waste gas treatment, but also realizes the resource utilization of industrial waste gas, which has significant economic benefits.

[0019] (5) The periphery of the production well is insulated with vacuum oil-sealed heat pipes with extremely low thermal conductivity, which can effectively reduce the loss of heat to the surrounding rock layers and further enhance the reliability of the system.

[0020] (6) High-frequency pulsed flue gas carrying catalyst is injected to enhance the permeability of deep, dense, oil-rich coal seams. The periodic pressure fluctuations generated can not only create cracks and form a more interconnected pore network, but also continuously disturb the catalyst particles in the near-well zone. Boiler exhaust gas carrying catalyst is used to convectively heat the deep oil-rich coal seams. The residence of the catalyst can promote the improvement of the yield and quality of in-situ pyrolysis tar, effectively prevent its aggregation and sedimentation, and ensure the smooth flow of the seepage channel.

[0021] (7) By preheating the waste gas, the strong microwave absorber-water in the formation is removed in advance, which optimizes the properties of the formation medium and can effectively save the electrical energy required for subsequent microwave heating. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the in-situ pyrolysis system for deep oil-rich coal seams with composite heating according to the present invention; Explanation of reference numerals in the attached diagram: 1 is a deep oil-rich coal seam, 2 is the surrounding rock strata, 3 is a heating well, 4 is a production well, 5 is a temperature monitoring point, 6 is a horizontal well, 7 is a phased array, 8 is an insulation jacket, 9 is a temperature monitoring point, 10 is a long-distance microwave heating system, 11 is a waveguide, 12 is a low-power microwave generator, 13 is a high-power microwave generator, 14 is a boiler, 15 is a pretreatment system, 16 is a catalyst addition device, 17 is a high-frequency pulse injection system, 18 is boiler flue gas carrying catalyst particles, 19 is a gas-liquid separation device, 20 is an oil storage tank, and 21 is a gas storage device. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0024] See Figure 1 As shown, the in-situ pyrolysis system for deep oil-rich coal seams of the present invention comprises a deep oil-rich coal seam 1 and surrounding rock strata 2. Four heating wells 3 and one production well 4 are vertically excavated downwards from the ground into the deep oil-rich coal seam 1. The four heating wells 3 are arranged in a quadrilateral shape, and the production well 4 is located at the center of the quadrilateral. A temperature monitoring well 5 is vertically excavated downwards at the center of the line connecting the wellheads of the heating wells 3 and the production well 4. A horizontal well 6 is excavated inside the deep oil-rich coal seam 1 to connect the heating wells 3 and the production well 4. A phased array 7 is arranged in the target deep oil-rich coal seam 1 section within the heating wells 3. The phased array 7 is connected to a high-power microwave generator 13 on the ground via a waveguide 11. Several temperature monitoring points 9 are installed around the production well 4. An insulation sleeve 8 is laid around the production well 4. A long-distance microwave heating system 10 is arranged along the entire production well 4, with waveguides 11 connected to a low-power microwave generator on the ground. The production well 4 is insulated using vacuum oil-separated heat pipes.

[0025] The target deep oil-rich coal seam 1 is buried at a depth greater than 1000 m.

[0026] The phased array 7 consists of multiple independent radiating units. It efficiently receives microwave energy from the high-power microwave generator 13 on the ground through the waveguide 11 and focuses it precisely and intensely on the target coal seam area, reducing the large amount of energy dissipation when mining the deep oil-rich coal seam 1. The long-distance microwave heating system 10 receives microwave energy from the low-power microwave generator 12 on the ground and evenly transmits it into the production well 4 to form a heat preservation field, thereby ensuring production continuity and tar recovery rate.

[0027] The waste gas from boiler 14 is used to heat the deep oil-rich coal seam 1 via convection, thereby removing the naturally occurring strong microwave absorber, water, from the stratum and reducing the energy consumption for subsequent microwave heating.

[0028] Low-grade industrial waste gas—boiler flue gas 14—undergoes a series of pretreatments before entering the catalyst addition device 16. It is then injected into the deep oil-rich coal seam 1 via the high-frequency pulse injection system 17 through the heating well 3, simultaneously enhancing permeability and preheating the deep oil-rich coal seam 1. After flowing within the deep oil-rich coal seam 1, the flue gas flows out through the production well 4. When the temperature monitoring well 5 reports that the temperature has reached the set preheating range, the injection of high-temperature fluid is stopped, and the high-power microwave generator 13 and the low-power microwave generator 12 on the ground are activated. At this point, the deep oil-rich coal seam 1 is transformed from convective heating to... Microwave heating is used to conduct high-temperature pyrolysis reactions in the deep oil-rich coal seam 1 under the microwave heating action of phased array 7. Under the long-distance microwave heating action, a microwave insulation field is formed around the production well 4. The intensity of long-distance microwave heating is adjusted in real time through the feedback of temperature monitoring points 9 around the production well 4 to minimize the tar condensation loss during the process of pyrolysis products moving from deep strata to the surface. After the pyrolysis products flow out along the production well 4, they enter the gas-liquid separation device 19. The separated tar is collected in the oil storage tank 20, and the remaining pyrolysis gas enters the gas storage device 21.

[0029] High-frequency pulse injection of boiler exhaust gas into the deep, dense, oil-rich coal seam 1 enhances its permeability, forming a more interconnected pore network. The deep oil-rich coal seam 1 is then convectively heated using boiler exhaust gas carrying a catalyst. The catalyst's residence promotes improved yield and quality of in-situ pyrolysis tar. The catalyst is an organic iron salt / organomolybdenum salt.

[0030] A composite heating method of "convection preheating - microwave pyrolysis / insulation" is adopted. Low-grade waste gas is first used for preheating, followed by high-grade electrical energy for high-temperature pyrolysis and insulation, thus achieving tiered energy utilization. The set preheating temperature range is 200~300 ℃. Real-time monitoring of the product temperature at temperature monitoring point 9 and microwave control maintain the temperature near production well 4 within the range of 350~400 ℃.

[0031] The present invention provides an in-situ pyrolysis method for deep oil-rich coal seams using composite heating, comprising the following steps: 1) After a series of pretreatments, the flue gas from boiler 14 enters the catalyst addition device 16 and is injected into the deep oil-rich coal seam 1 through the high-frequency pulse injection system 17 along the heating well 3. The deep oil-rich coal seam 1 is simultaneously subjected to permeation enhancement and preheating treatment. The boiler flue gas 18 carrying catalyst particles flows inside the deep oil-rich coal seam 1 and then flows out along the production well 4. 2) When the set preheating range is reached, stop injecting high-temperature fluid, turn on the high-power microwave generator 13 and the low-power microwave generator 12 on the ground. At this time, the deep oil-rich coal seam 1 is converted from convection heating to microwave heating. The deep oil-rich coal seam 1 undergoes a high-temperature pyrolysis reaction. At the same time, a microwave insulation field is formed around the production well 4. The intensity of long-distance microwave heating is adjusted in real time through the feedback from the temperature monitoring well 5 around the production well 4. 3) After the pyrolysis products flow out along the production well 4, they enter the gas-liquid separation device 19. The separated tar is collected in the oil storage tank 20, and the remaining pyrolysis gas enters the gas storage device 21.

Claims

1. An in-situ pyrolysis system for composite heating of deep oil-rich coal seams, characterized in that: This includes four heating wells (3) and one production well (4) excavated vertically downwards from the ground into the deep oil-rich coal seam (1). The four heating wells (3) are arranged in a quadrilateral shape, and the production well (4) is located at the center of the quadrilateral. Temperature monitoring wells (5) are excavated vertically downwards at the center of the lines connecting the wellheads of the four heating wells (3) and the wellhead of the production well (4). Horizontal wells (6) are excavated inside the deep oil-rich coal seam (1) to connect the four heating wells (3) and the production well (4). A phased array (7) is arranged in the target deep oil-rich coal seam (1) section within the heating wells (3). (7) Connected to a high-power microwave generator (13) on the ground via a waveguide (11), several temperature monitoring points (9) are installed around the production well (4), and an insulation sleeve (8) is laid around the production well (4). A long-distance microwave heating system (10) is arranged along the entire production well (4), and the long-distance microwave heating system (10) is connected to a low-power microwave generator (12) on the ground via a waveguide (11). A gas-liquid separation device (19) is installed at the wellhead of the production well (4), and a catalyst addition device, a high-frequency pulse injection system and a flue gas pretreatment system are installed at the wellhead of the heating well (3). After the low-grade industrial waste gas is pretreated, a catalyst is added, and then it is injected into the deep oil-rich coal seam (1) through the heating well (3) via the high-frequency pulse injection system (17). The deep oil-rich coal seam (1) is simultaneously subjected to permeation and preheating treatment. When the set preheating range is reached, the injection of high-temperature fluid is stopped, and the high-power microwave generator (13) and low-power microwave generator (12) on the ground are turned on. Under the microwave heating action of the phased array (7), the deep oil-rich coal seam (1) undergoes a high-temperature pyrolysis reaction. Under the long-distance microwave heating action, a microwave insulation field is formed around the production well (4). The pyrolysis products flow out along the production well (4) and enter the gas-liquid separation device (19) to separate the obtained tar and pyrolysis gas.

2. The in-situ pyrolysis system for composite heating of deep oil-rich coal seams as described in claim 1, characterized in that: The phased array (7) consists of multiple independent radiation units. It efficiently receives microwave energy from the ground high-power microwave generator (13) through the waveguide (11). The long-distance microwave heating system (10) receives microwave energy from the ground low-power microwave generator (12) and uniformly transmits it into the production well (4) to form a heat preservation field.

3. The in-situ pyrolysis system for composite heating of deep oil-rich coal seams as described in claim 2, characterized in that: The outer insulation sleeve (8) of the production well (4) adopts a vacuum oil-insulated heat pipe.

4. The in-situ pyrolysis system for composite heating of deep oil-rich coal seams as described in claim 3, characterized in that: The target deep oil-rich coal seam (1) is buried at a depth greater than 1000 m.

5. The in-situ pyrolysis system for composite heating of deep oil-rich coal seams as described in any one of claims 1-4, characterized in that: The low-grade industrial waste gas is boiler (14) flue gas. The boiler (14) flue gas is used to convect and heat the deep oil-rich coal seam (1) to remove the strong microwave absorber-water that is naturally present in the stratum.

6. The in-situ pyrolysis system for composite heating of deep oil-rich coal seams as described in any one of claims 1-4, characterized in that: The catalyst is an organic iron salt / organic molybdenum salt.

7. The in-situ pyrolysis method for deep oil-rich coal seams based on the pyrolysis system of claim 6, characterized in that... Includes the following steps: 1) After the low-grade industrial waste gas is pretreated, it enters the catalyst addition device (16) to add catalyst. The catalyst is injected into the deep oil-rich coal seam (1) through the high-frequency pulse injection system (17) along the heating well (3). The deep oil-rich coal seam (1) is simultaneously subjected to permeation enhancement and preheating treatment. The flue gas (18) flows inside the deep oil-rich coal seam (1) and then flows out along the production well (4). 2) When the set preheating range is reached, stop injecting high-temperature fluid and turn on the high-power microwave generator (13) and low-power microwave generator (12) on the ground. At this time, the deep oil-rich coal seam (1) is transformed from convection heating to microwave heating. The deep oil-rich coal seam (1) undergoes a high-temperature pyrolysis reaction. At the same time, a microwave insulation field is formed around the production well (4). The long-distance microwave heating intensity is adjusted in real time through the feedback from the temperature monitoring well (5) of the production well (4). 3) After the pyrolysis products flow out along the production well (4), they enter the gas-liquid separation device (19). The separated tar is collected in the oil storage tank (20), and the remaining pyrolysis gas enters the gas storage device (21).

8. The in-situ pyrolysis method for deep oil-rich coal seams with composite heating as described in claim 7, characterized in that: The preheating temperature set in step 2) is 200~300 ℃.

9. The in-situ pyrolysis method for deep oil-rich coal seams with composite heating as described in claim 7, characterized in that: In step 2), the product temperature is monitored in real time through temperature monitoring point (9), so that the temperature near the production well (4) is in the range of 350~400 ℃.

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