Coal seam transferred arc plasma in-situ conversion enhancement system and method

Abstract

A coal seam transferred arc plasma in-situ conversion enhancement system and method, in which a coal seam directional drilling well is vertically drilled from the ground to the underground to form a vertical channel from the ground surface to the center line of the coal seam, and then gradually deflected to the horizontal direction to form a non-vertical channel inside the coal seam; two non-coal seam directional drilling wells are vertically drilled from the ground to the underground to form a vertical channel from the ground surface to a certain distance from the coal seam, and then gradually deflected to the horizontal direction to form a non-vertical channel close to the top plate or bottom plate of the coal seam; a reaction medium injection pipe is arranged in the coal seam directional drilling well to inject the reaction medium, the cathode assembly can be movably arranged in one non-coal seam directional drilling well, and the anode assembly can be movably arranged in another non-coal seam directional drilling well and face the cathode assembly, and the cathode assembly and the anode assembly are energized to generate high-voltage ionization to heat and activate the reaction medium from the reaction medium injection pipe between the cathode assembly and the anode assembly. The system improves the radial momentum transfer speed of active particles in the coal seam.

Description

Technical Field

[0001] The invention relates to the technical field of coal seam gasification, and in particular to a coal seam transferred arc plasma in-situ conversion enhancement system and method. Background Art

[0002] Underground coal gasification technology integrates well construction, coal mining and conversion, and can convert coal seam resources into oil and gas resources in situ. It is a new type of coal mining technology. However, underground coal gasification technology relies on the semi-natural force control of oxygen injection autothermal reaction, gasification agent diffusion and thermal spalling of coal seams, which leads to a very limited radial gasification range of coal seams and waste of radial coal in thick coal seams. Recently, an invention has proposed the use of plasma conversion technology with high energy density and high activity particles to provide gasification heat source and high activity particles for coal seam conversion reaction at the same time, and efficiently convert highly active water vapor, carbon dioxide and other substances into high-quality resources of hydrogen and carbon monoxide by reacting with coal seams. Since the coal seam conversion reaction relies on plasma heat radiation and high activity particle reduction reaction control, the reaction is simplified and easy to start and stop; the plasma generator is electrically controlled. Overall, the degree of control of the gasification surface is greatly improved, making the coal seam conversion process more precise and controllable. However, in the case of thick and extra-thick coal seams, as the reaction cavity expands, the unconstrained free high-temperature and highly active particles slowly diffuse in a large space, which will still cool down and become inactive, making it difficult for the thick coal seams at the far end of the radial range to be reacted. After the conversion is completed, a large amount of residual coal seams will still remain on both sides of the gasification channel, resulting in a waste of thick coal seam resources. Therefore, it is necessary to find a way to increase the radial momentum transfer speed of active particles and strengthen the radial conversion of coal seams, so as to increase the radial coal seam influence range and thus improve the utilization rate of energy resources.

[0003] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0004] The purpose of the present invention is to provide a coal seam transferred arc plasma in-situ conversion enhancement system and method. In view of the problem that the radial conversion range of coal seams is limited in the current coal seam conversion technology, resulting in too low resource utilization rate of thick coal seams, the radial momentum transfer speed of high-temperature and high-activity particles in the coal seams is increased, the radial conversion of coal seams is enhanced, so as to increase the radial influence range of coal seams, thereby improving the utilization rate of energy resources such as coal.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A coal seam transferred arc plasma in-situ conversion enhancement system of the present invention comprises:

[0007] Coal seam directional drilling, which drills vertically from the ground to the underground to form a vertical channel from the surface to the center line of the coal seam, and then gradually deflects to the horizontal direction to form a non-vertical channel inside the coal seam;

[0008] Two non-coal seam directional drillings, which drill vertically from the ground to the underground to form a vertical channel from the surface to a certain distance from the coal seam, and then gradually deflect to the horizontal direction to form a non-vertical channel close to the roof or floor of the coal seam;

[0009] A vertical well, which is drilled vertically from the ground to the underground until it passes through the coal seam and is connected with the directional drilling well of the coal seam to serve as a channel for discharging the coal seam gasification reaction products to the ground;

[0010] A reaction medium injection pipe is provided in a directional wellbore of a coal seam to inject the reaction medium.

[0011] A transferred arc plasma generator comprising,

[0012] A cathode assembly, which is movably arranged in a non-coal seam directional drilling well,

[0013] The anode assembly is movably arranged in another non-coal seam directional drilling well and faces the cathode assembly. After the cathode assembly and the anode assembly are energized, high-voltage ionization is generated to heat and activate the reaction medium from the reaction medium injection pipe between the cathode assembly and the anode assembly.

[0014] In the coal seam transferred arc plasma in-situ conversion enhancement system, the reaction medium injection pipe is connected to the flexible coiled pipe and moves in the coal seam as the flexible coiled pipe expands and contracts.

[0015] In the coal seam transferred arc plasma in-situ conversion and enhancement system, the reaction medium is carbon dioxide, water, nitrogen, hydrogen, air or enriched oxygen.

[0016] In the coal seam transferred arc plasma in-situ conversion and strengthening system, the cathode assembly or the anode assembly is composed of electrodes and cables, and the electrodes are graphite, copper or copper-based alloy conductive materials.

[0017] In the coal seam transferred arc plasma in-situ conversion and strengthening system, the length of the electrode is 5-500m, one end of the cable is connected to the electrode, and the other end is located on the ground.

[0018] In the coal seam transferred arc plasma in-situ conversion and strengthening system, the cables of the cathode assembly and the anode assembly are coated with high-strength materials on the outside, and the cables are dragged from the ground to move the positions of the cathode and anode assemblies in the directional drilling well.

[0019] In the coal seam transferred arc plasma in-situ conversion and strengthening system, the cathode assembly and the anode assembly can be interchanged, and the cathode assembly and the anode assembly can be completely opposite to each other or staggered by a certain distance in the horizontal direction.

[0020] A method for strengthening a coal seam transferred arc plasma in-situ conversion strengthening system comprises:

[0021] Vertical drilling from the ground to the underground forms a vertical channel from the ground surface to the center line of the coal seam, and then gradually deflects to the horizontal direction to form a non-vertical channel inside the coal seam, thereby obtaining a coal seam directional drilling well. Vertical drilling from the ground to the underground forms a vertical channel from the ground surface to a certain distance from the coal seam, and then gradually deflects to the horizontal direction to form a non-vertical channel close to the top plate or bottom plate of the coal seam, thereby obtaining two non-coal seam directional drilling wells. Vertical drilling from the ground to the underground until the coal seam is passed through and connected with the coal seam directional drilling well to obtain a vertical well.

[0022] The reaction medium injection pipe is located in the coal seam directional drilling well. One end of the reaction medium injection pipe is lowered to the designated area in the coal seam, and the other end is located on the ground. The injection flow and composition are controlled by the ground. The reaction medium injection pipe is debugged on the ground, and the reaction medium in and out circulation is tested. The power is turned on, and the startup and power adjustment of the transferred arc plasma generator are tested to be normal. A certain flow of reaction medium is injected into the reaction medium injection pipe from the ground. The flow data of the vertical well outlet is tested to determine whether the conversion channel and the vertical well are unobstructed. After confirming that the conversion channel and the vertical well are unobstructed, the reaction medium is injected into the reaction medium injection pipe from the ground, and the power start switch of the cathode assembly and the anode assembly is turned on to start the transferred arc plasma generator.

[0023] Test the outlet gas composition, flow rate and temperature data from the vertical well outlet. When the outlet gas composition, flow rate and temperature of the vertical well meet the standards, it indicates that the coal seam has started the conversion reaction. Gradually adjust the reaction medium flow rate injected by the reaction medium injection pipe and the power of the transferred arc plasma generator to keep the production load between 50% and 60% and start the coal seam conversion production. After a period of normal production, when the vertical well feedback outlet gas flow rate continues to decline, it indicates that the coal seam conversion reaction intensity decreases with the increase of the reaction cavity. At this time, increase the reaction medium flow rate injected by the reaction medium injection pipe and the power of the transferred arc plasma generator to increase the conversion reaction load to 80% to 100% and continue production. After a period of time, the vertical well test device feedback outlet gas flow rate further decreases, indicating that the coal seam covered between the reaction medium injection pipe and the vertical well has been converted. The cathode assembly, anode assembly and reaction medium injection pipe are all withdrawn 10 to 100 meters under ground control to continue the coal seam conversion production.

[0024] The production is adjusted in this way according to the statistics of the movement distance of the reaction medium injection pipe. If the difference between the non-vertical channel distance of the coal seam directional drilling and the movement distance of the reaction medium injection pipe is close to the retreat distance of the reaction medium injection pipe each time, it indicates that the coal seam covered by the unit has been converted. The power supply of the cathode assembly and the anode assembly is turned off, the injection of the reaction medium is stopped, and the cathode assembly, anode assembly and reaction medium injection pipe are withdrawn to the ground respectively, and the well is shut in. Construction, installation and conversion production are carried out in another target coal seam block. The cycle is repeated until the end.

[0025] In the above technical scheme, a coal seam transferred arc plasma in-situ conversion enhancement system and method provided by the present invention has the following beneficial effects: using transferred arc plasma to guide active particles to flow radially in the coal seam to increase the radial enhanced conversion range of the coal seam, which can be applied to thick coal seam conversion mining, and can also be used for the development and utilization of carbon-based energy such as coal, peat, oil sands, coal gangue, oil shale, and heavy oil layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0027] Figure 1 A schematic structural diagram of a coal seam transferred arc plasma in-situ conversion enhancement system provided by an embodiment of the present invention.

[0028] Description of reference numerals:

[0029] 1. Coal seam; 2. Coal seam directional drilling; 5. Vertical well; 6. Reaction medium; 7. Cable; 8. Anode assembly; 9. Cathode assembly. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0035] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0037] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] See also Figure 1 As shown, in one embodiment, a coal seam transferred arc plasma in-situ conversion enhancement system of the present invention comprises:

[0039] Coal seam directional drilling 2, which drills vertically from the ground to the underground to form a vertical channel from the surface to the center line of the coal seam 1, and then gradually deflects to the horizontal direction to form a non-vertical channel inside the coal seam 1;

[0040] Two non-coal seam directional drillings, which drill vertically from the ground to the underground to form a vertical channel from the surface to a certain distance from the coal seam, and then gradually deflect to the horizontal direction to form a non-vertical channel close to the roof or floor of the coal seam;

[0041] A vertical well 5, which is drilled vertically from the ground to the underground until it passes through the coal seam 1 and is connected with the coal seam directional drilling well 2 to serve as a channel for discharging the coal seam gasification reaction product to the ground;

[0042] A reaction medium injection pipe is provided in the coal seam directional drilling well 2 to inject the reaction medium 6,

[0043] A transferred arc plasma generator comprising,

[0044] The cathode assembly 9 is movably arranged in a non-coal seam directional drilling well,

[0045] The anode assembly 8 is movably arranged in another non-coal seam directional drilling and facing the cathode assembly 9. After the cathode assembly 9 and the anode assembly 8 are energized, high-voltage ionization is generated to heat and activate the reaction medium 6 from the reaction medium injection pipe between the cathode assembly 9 and the anode assembly 8.

[0046] In a preferred embodiment of the coal seam transferred arc plasma in-situ conversion enhancement system, the reaction medium injection pipe is connected to the flexible coiled tube and moves in the coal seam as the flexible coiled tube expands and contracts.

[0047] In a preferred embodiment of the coal seam transferred arc plasma in-situ conversion enhancement system, the reaction medium 6 is carbon dioxide, water, nitrogen, hydrogen, air or enriched oxygen.

[0048] In a preferred embodiment of the coal seam transferred arc plasma in-situ conversion enhancement system, the cathode assembly 9 or the anode assembly 8 is composed of an electrode and a cable 7, and the electrode is a conductive material of graphite, copper or copper-based alloy.

[0049] In a preferred embodiment of the coal seam transferred arc plasma in-situ conversion and enhancement system, the electrode length is 5-500 m, one end of the cable 7 is connected to the electrode, and the other end is located on the ground.

[0050] In a preferred embodiment of the coal seam transferred arc plasma in-situ conversion enhancement system, the cables of the cathode assembly 9 and the anode assembly 8 are coated with high-strength material on the outside, and the cables 7 are dragged from the ground to move the positions of the cathode and anode assemblies 8 in the directional drilling well.

[0051] In a preferred embodiment of the coal seam transferred arc plasma in-situ conversion enhancement system, the cathode assembly 9 and the anode assembly 8 can be interchanged, and the cathode assembly 9 and the anode assembly 8 can be completely opposite or staggered by a certain distance in the horizontal direction.

[0052] A method for strengthening a coal seam transferred arc plasma in-situ conversion strengthening system comprises:

[0053] Vertical drilling from the ground to the underground forms a vertical channel from the ground surface to the center line of the coal seam, and then gradually deflects to the horizontal direction to form a non-vertical channel inside the coal seam, to obtain a coal seam directional drilling well 2, vertical drilling from the ground to the underground forms a vertical channel from the ground surface to a certain distance from the coal seam, and then gradually deflects to the horizontal direction to form a non-vertical channel close to the top plate or bottom plate of the coal seam, to obtain two non-coal seam directional drilling wells, vertical drilling from the ground to the underground until the coal seam is passed through and connected with the coal seam directional drilling well 2 to obtain a vertical well 5;

[0054] The reaction medium injection pipe is located in the coal seam directional drilling well 2. One end of the reaction medium injection pipe is lowered to the designated area in the coal seam, and the other end is located on the ground. The injection flow and composition are controlled by the ground. The reaction medium injection pipe is debugged on the ground, and the reaction medium in and out circulation is tested. The power is turned on, and the startup and power adjustment of the transferred arc plasma generator are tested to be normal. A certain flow of reaction medium is injected into the reaction medium injection pipe from the ground. The flow data at the outlet of the vertical well 5 is tested to determine whether the conversion channel and the vertical well 5 are unobstructed. After confirming that the conversion channel and the vertical well 5 are unobstructed, the reaction medium is injected into the reaction medium injection pipe from the ground, and the power start switches of the cathode assembly 9 and the anode assembly 8 are turned on to start the transferred arc plasma generator.

[0055] The outlet gas composition, flow rate and temperature data of the vertical well 5 outlet are tested. When the outlet gas composition, flow rate and temperature of the vertical well 5 outlet meet the standards, it indicates that the coal seam has started the conversion reaction. The reaction medium flow rate injected into the reaction medium injection pipe and the power of the transferred arc plasma generator are gradually adjusted to keep the production load between 50% and 60%, and the coal seam conversion production is started. After a period of normal production, when the outlet gas flow rate of the vertical well 5 feedback continues to decrease, it indicates that the coal seam conversion reaction intensity decreases with the increase of the reaction cavity. At this time, the reaction medium flow rate injected into the reaction medium injection pipe and the power of the transferred arc plasma generator are increased to increase the conversion reaction load to 80% to 100%, and production is continued. After a period of time, the outlet gas flow rate of the vertical well 5 test device feedback further decreases, indicating that the coal seam covered between the reaction medium injection pipe and the vertical well 5 has been converted. The cathode assembly 9, the anode assembly 8 and the reaction medium injection pipe are all withdrawn 10 to 100 meters by ground control to continue the coal seam conversion production.

[0056] The production is adjusted in this way in a cycle. According to the statistics of the moving distance of the reaction medium injection pipe, when the difference between the non-vertical channel distance of the coal seam directional drilling 2 and the moving distance of the reaction medium injection pipe is close to the retreat distance of the reaction medium injection pipe each time, it indicates that the coal seam covered by the unit has been converted. The power supply of the cathode assembly 9 and the anode assembly 8 is turned off, the injection of the reaction medium is stopped, and the cathode assembly 9, the anode assembly 8 and the reaction medium injection pipe are withdrawn to the ground respectively, and the well is closed. Construction, installation and conversion production are carried out in another target coal seam block. This cycle is repeated until the end.

[0057] In one embodiment, Figure 1 As shown, in the transfer arc plasma radially enhanced coal seam conversion, two directional drillings are constructed on the coal seam roof and coal seam floor, and the transferred arc plasma cathode and anode are placed respectively, and at least one directional drilling and one vertical well 5 are constructed in the coal seam. The coal seam directional drilling 2 is used as an injection pipe for injecting reaction medium, and the vertical well 5 is used as a discharge channel for coal seam conversion products, forming a transferred arc plasma coal seam conversion system. Transferred arc plasma can heat and activate the medium between the cathode and the anode through high-voltage ionization. This scheme uses transferred arc plasma to heat and activate the coal seam and the reaction medium between the cathode and the anode, prompting the coal seam to undergo conversion reaction in the radial direction, and the conversion products are discharged from the vertical well 5, so as to achieve the purpose of gasifying thick coal seams. The transferred arc plasma radially enhanced coal seam conversion system includes a coal seam roof directional drilling, a coal seam floor directional drilling, a coal seam directional drilling 2, a vertical well 5, a transferred arc plasma generator, and a reaction medium injection pipe.

[0058] The directional drilling is vertically drilled from the ground to the underground, and after a certain vertical distance, a vertical channel is formed, and then gradually deflected to the horizontal direction until it moves approximately horizontally, passes through a certain horizontal distance, and forms a non-vertical channel. Among them, the vertical channel of the directional drilling located at the top or bottom of the coal seam is from the ground surface to a certain distance from the coal seam, and the non-vertical channel is close to the top or bottom of the coal seam; the vertical channel of the directional drilling located in the coal seam is from the ground surface to the top of the coal seam, and the non-vertical channel is preferably in the middle of the coal seam, and can also be at the bottom or top of the coal seam and other positions. The directional drilling of the coal seam roof and the coal seam bottom are respectively used as the cathode and anode of the transferred arc plasma, and the coal seam directional drilling 2 is used as the injection pipe for injecting the reaction medium. The distance of the non-vertical channel of the directional drilling is determined according to the process.

[0059] The vertical well 5 is drilled vertically from the ground to the underground until it passes through the coal seam and is connected with the coal seam directional drilling well 2. The vertical well 5 serves as a channel for the coal seam conversion reaction products to be discharged to the ground.

[0060] The transferred arc plasma generator includes a cathode assembly 9 and an anode assembly 8. The cathode assembly 9 is composed of an electrode and a cable. The electrode can be a conductive material such as graphite, copper or copper-based alloy. The length of the electrode is 5 to 500 m. One end of the cable is connected to the electrode and the other end is located on the ground. After the cathode assembly 9 is installed on the ground, it is gradually lowered to the coal seam roof area by directional drilling of the coal seam roof. The anode assembly 8 is composed of an electrode and a cable. The electrode can be a conductive material such as graphite, copper, etc. The length of the electrode is 5 to 500 m. One end of the cable is connected to the electrode and the other end is located on the ground. After the anode assembly 8 is installed on the ground, it is gradually lowered to the coal seam floor area by directional drilling of the coal seam floor. The cathode assembly 9 and the anode assembly 8 cables can be coated with high-strength materials on the outside, which have tensile and wear-resistant functions. The cables can be dragged from the ground to move the positions of the cathode and anode assemblies 8 in the directional drilling. The cathode assembly 9 and the anode assembly 8 can be interchanged, that is, the cathode assembly 9 can be on the bottom plate of the coal seam, and the anode assembly can be on the top plate of the coal seam. The cathode assembly 9 and the anode assembly 8 can be completely opposite or staggered by a certain distance in the horizontal direction. After the cathode assembly 9 and the anode assembly 8 are energized, a high-voltage ionization effect is generated, which can heat and activate the medium between the cathode and the anode. By moving the distance between the cathode assembly 9 and the anode assembly 8 in the directional drilling, the high-voltage ionization effect is controlled in different horizontal directions of the coal seam.

[0061] The reaction medium injection pipe is located in the coal seam directional drilling 2, one end of the reaction medium injection pipe is lowered to the designated area in the coal seam, and the other end is located on the ground. The reaction medium injection pipe can be controlled by the ground to move freely in the coal seam. Preferably, the reaction medium injection pipe is located at the intersection of the horizontal center line of the coal seam and the line connecting the midpoints of the cathode assembly 9 and the anode assembly 8. At least one fluid channel is arranged in the reaction medium injection pipe, into which fluids such as carbon dioxide, water, nitrogen, hydrogen, air or oxygen-enriched fluids can be input, and the injection flow rate and composition are controlled by the ground, and the reaction medium flow rate and composition are determined according to different coal seam conversion processes. Through the high-voltage discharge between the cathode assembly 9 and the anode assembly 8, the coal seam and the reaction medium between the cathode assembly 9 and the anode assembly 8 are heated and activated, so as to promote the enhanced conversion reaction between the coal seam and the reaction medium.

[0062] The transferred arc plasma radially enhanced coal seam conversion method includes:

[0063] 1) Installation

[0064] The directional drilling is vertically drilled from the ground to the underground, and after a certain vertical distance, a vertical channel is formed, and then gradually deflected to the horizontal direction until it moves approximately horizontally, passes through a certain horizontal distance, and forms a non-vertical channel. Among them, the vertical channel of the directional drilling located at the top or bottom of the coal seam is from the ground surface to a certain distance from the coal seam, and the non-vertical channel is close to the top or bottom of the coal seam; the vertical channel of the directional drilling located in the coal seam is from the ground surface to the top of the coal seam, and the non-vertical channel is preferably in the middle of the coal seam, and can also be at the bottom or top of the coal seam and other positions as a conversion channel. The directional drilling of the coal seam roof and the coal seam bottom are respectively used as the cathode and anode of the transferred arc plasma, and the coal seam directional drilling 2 is used as the injection pipe for injecting the reaction medium. The distance of the non-vertical channel of the directional drilling is determined according to the process.

[0065] The vertical well 5 is drilled vertically from the ground to the underground until it passes through the coal seam and is connected with the coal seam directional drilling well 2. The vertical well 5 serves as a channel for the coal seam conversion reaction products to be discharged to the ground.

[0066] The transferred arc plasma generator includes a cathode assembly 9 and an anode assembly 8. The cathode assembly 9 is composed of an electrode and a cable. The electrode can be a conductive material such as graphite, copper or copper-based alloy. The length of the electrode is 5 to 500 m. One end of the cable is connected to the electrode and the other end is located on the ground. After the cathode assembly 9 is installed on the ground, it is gradually lowered to the coal seam roof area by directional drilling of the coal seam roof. The anode assembly 8 is composed of an electrode and a cable. The electrode can be a conductive material such as graphite, copper, etc. The length of the electrode is 5 to 500 m. One end of the cable is connected to the electrode and the other end is located on the ground. After the anode assembly 8 is installed on the ground, it is gradually lowered to the coal seam floor area by directional drilling of the coal seam floor. The cathode assembly 9 and the anode assembly 8 cables can be coated with high-strength materials on the outside, which have tensile and wear-resistant functions. The cables can be dragged from the ground to move the positions of the cathode and anode assemblies 8 in the directional drilling. The cathode assembly 9 and the anode assembly 8 can be interchanged, that is, the cathode assembly 9 can be on the coal seam floor, and the anode can be on the coal seam roof. The cathode assembly 9 and the anode assembly 8 can be completely opposite or staggered by a certain distance in the horizontal direction. After the cathode assembly 9 and the anode assembly 8 are energized, high-voltage ionization is generated, which can heat and activate the medium between the cathode and the anode.

[0067] The reaction medium injection pipe is located in the coal seam directional drilling well 2, one end of the reaction medium injection pipe is lowered to a designated area in the coal seam, and the other end is located on the ground. The reaction medium injection pipe can be controlled by the ground to move freely in the coal seam, and the reaction medium injection pipe is preferably located at the intersection of the horizontal center line of the coal seam and the line connecting the midpoints of the cathode assembly 9 and the anode assembly 8. At least one fluid channel is arranged in the reaction medium injection pipe, into which fluids such as carbon dioxide, water, nitrogen, hydrogen, air or oxygen-enriched fluids can be input, and the injection flow rate and composition are controlled by the ground, and the reaction medium flow rate and composition are determined according to different coal seam conversion processes.

[0068] According to the construction and installation method, after the construction of each directional drilling well and the vertical well 5 is completed and the installation of each device is completed. On the ground, the reaction medium injection pipe reaction medium inlet and outlet circulation is tested, the power is turned on, and the transfer arc plasma generator startup and power adjustment are tested to be normal. The cathode assembly 9, the anode assembly 8 and the reaction medium injection pipe are moved to the target area in each directional drilling well by the ground control device, so that the horizontal distance between the reaction medium injection pipe and the vertical well 5 is 10-100m.

[0069] 2) Initiation of conversion reaction

[0070] A certain flow rate of reaction medium is injected into the reaction medium injection pipe from the ground, and the flow rate data at the outlet of the vertical well 5 is tested to determine whether the conversion channel and the vertical well 5 are unobstructed. After confirming that the conversion channel and the vertical well 5 are unobstructed, the reaction medium is injected into the reaction medium injection pipe from the ground, and the power start switches of the cathode assembly 9 and the anode assembly 8 are turned on to start the transferred arc plasma generator.

[0071] The outlet gas composition, flow rate, temperature and other data are tested at the outlet of vertical well 5. When the outlet gas composition, flow rate and temperature of vertical well 5 meet the standards, it indicates that the coal seam has started to convert. The reaction medium flow rate injected into the reaction medium injection pipe and the power of the transferred arc plasma generator are gradually adjusted to keep the production load between 50% and 60%, and the coal seam conversion production is started.

[0072] 3) Main operations of production control

[0073] For example, after a period of normal production, when the outlet gas flow rate of vertical well 5 continues to decrease, it indicates that the conversion reaction intensity of the coal seam decreases as the reaction cavity increases. At this time, it is necessary to increase the reaction medium flow rate injected into the reaction medium injection pipe and the power of the transferred arc plasma generator to increase the conversion reaction load to 80%~100% and continue production.

[0074] After a period of time, the outlet gas flow rate of the vertical well 5 test device further decreased, indicating that the conversion of the coal seam between the reaction medium injection pipe and the vertical well 5 was completed. The cathode assembly 9, the anode assembly 8 and the reaction medium injection pipe were all withdrawn 10-100m by ground control to continue the coal seam conversion production.

[0075] 4) Production end operation

[0076] In this way, production is adjusted in a cycle. According to the statistics of the moving distance of the reaction medium injection pipe, if the difference between the non-vertical channel distance of the coal seam directional drilling 2 and the moving distance of the reaction medium injection pipe is close to the distance of each withdrawal of the reaction medium injection pipe, it indicates that the coal seam covered by the unit has been converted. Turn off the power supply of the cathode assembly 9 and the anode assembly 8, stop the injection of the reaction medium, and withdraw the cathode assembly 9, the anode assembly 8 and the reaction medium injection pipe to the ground respectively. Perform the well closure operation. According to the above method, construction, installation and conversion production are carried out in another target coal seam block.

[0077] Example 2, in the transferred arc plasma enhanced thick coal seam in-situ pyrolysis method:

[0078] The embodiment of the present invention proposes a method for producing oil and gas products by in-situ pyrolysis reaction of thick coal seams enhanced by transferred arc plasma. The coal seam is a long flame coal resource with a buried depth of about 1020m and an average thickness of 21m. A conversion unit is designed to cover a horizontal distance of 1000m in the coal seam. A cathode assembly 9 is placed at the top plate of the coal seam, an anode assembly 8 is placed at the bottom plate of the coal seam, and a reaction medium injection pipe is placed in the middle of the coal seam.

[0079] After the directional drilling of the coal seam roof is vertically drilled from the ground to the underground for a distance of about 1000m, a vertical channel is formed, and then it gradually deflects in the horizontal direction of the coal seam roof until it approaches the coal seam roof and passes through a horizontal distance of about 1000m to form a non-vertical channel. After the directional drilling of the coal seam floor is vertically drilled from the ground to the underground for a distance of about 1020m, a vertical channel is formed, and then it gradually deflects in the horizontal direction of the coal seam floor until it approaches the coal seam floor and passes through a horizontal distance of about 1000m to form a non-vertical channel. After the directional drilling 2 of the coal seam is vertically drilled from the ground to the underground for a distance of about 1010m, a vertical channel is formed, and then it gradually deflects in the horizontal direction of the middle of the coal seam until it approaches the middle of the coal seam and passes through a horizontal distance of about 1000m to form a non-vertical channel. The vertical well 5 is vertically drilled from the ground to the underground for about 1041m, until it passes through the coal seam and is connected with the directional drilling 2 of the coal seam.

[0080] The cathode assembly 9 is lowered from the ground to the top of the coal seam by directional drilling, and moves in a non-vertical channel until the end of the cathode approaches the vertical well 5. The anode assembly 8 is lowered from the ground to the bottom of the coal seam by directional drilling, and moves in a non-vertical channel until the end of the anode approaches the vertical well 5. The length of the cathode and anode is 50m. The reaction medium injection pipe is gradually lowered into the coal seam through the coal seam directional drilling 2 until the horizontal distance from the vertical well 5 is about 50m, and nitrogen is used as the reaction medium.

[0081] According to the construction and installation method, after the construction of each directional drilling well and vertical well 5 is completed and the installation of each device is completed, the ground debugging is carried out to test the reaction medium injection pipe reaction medium inlet and outlet circulation, turn on the power, and test the transfer arc plasma generator startup and power adjustment to be normal.

[0082] 100 Nm is injected into the reaction medium injection pipe from the ground 3 / h nitrogen, and the flow rate data at the outlet of vertical well 5 is used to determine whether the conversion channel and vertical well 5 are unobstructed. After confirming that the conversion channel and vertical well 5 are unobstructed, 100 Nm 3 / h nitrogen and cooling medium, turn on the power start switches of the cathode assembly 9 and the anode assembly 8, and start the transferred arc plasma generator.

[0083] The gas composition data at the outlet of vertical well 5 was tested. When the volume percentage of CH4 in the gas at the outlet of vertical well 5 was higher than 5% in addition to the injected N2, it indicated that the long flame coal seam had started the conversion reaction. Gradually adjust the nitrogen flow rate to 500 Nm 3 / h, adjust the cathode and anode power to about 1000 kW, keep the production load between 50% and 60%, and start coal seam pyrolysis production. During the production process, the outlet gas of vertical well 5 was tested for CH4+H2+CO>50%, indicating that the pyrolysis production was normal.

[0084] After 13 days of normal production, the volume ratio of CH4+H2+CO in the outlet gas of vertical well 5 was about 56%, but the outlet gas flow rate continued to decline, indicating that the conversion reaction intensity of the long flame coal seam decreased with the increase of the reaction cavity. At this time, the nitrogen flow rate needs to be increased to 900 Nm 3 / h, the cathode and anode power reached about 1800 kW, the conversion reaction load increased to about 90%, and production continued.

[0085] After 7 days of continuous production, the outlet gas flow and CH4+H2+CO volume ratio reported by the test device of vertical well 5 began to decrease, indicating that the conversion of the coal seam between the reaction medium injection pipe and vertical well 5 was complete. The reaction medium injection pipe, cathode assembly 9 and anode assembly 8 were all withdrawn 50m by ground control to continue coal seam pyrolysis production.

[0086] After adjusting the production cycle in this way, the reaction medium injection pipe device moves a distance of nearly 950m, indicating that the coal seam covering the unit has been completely converted. Turn off the power supply of the cathode assembly 9 and the anode assembly 8, stop the injection of the reaction medium, and withdraw the reaction medium injection pipe and the cathode assembly 9 and the anode assembly 8 to the ground respectively. Perform the production end operation.

[0087] Finally, it should be noted that the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present application.

[0088] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A coal seam transferred arc plasma in-situ conversion and strengthening system, characterized in that: These include, Coal seam directional drilling, which drills vertically from the ground to the underground to form a vertical channel from the surface to the center line of the coal seam, and then gradually deflects to the horizontal direction to form a non-vertical channel inside the coal seam; Two non-coal seam directional drillings, which drill vertically from the ground to the underground to form a vertical channel from the surface to a certain distance from the coal seam, and then gradually deflect to the horizontal direction to form a non-vertical channel close to the roof or floor of the coal seam; A vertical well, which is drilled vertically from the ground to the underground until it passes through the coal seam and is connected with the directional drilling well of the coal seam to serve as a channel for discharging the coal seam gasification reaction products to the ground; A reaction medium injection pipe is provided in a directional wellbore of a coal seam to inject the reaction medium. A transferred arc plasma generator comprising, A cathode assembly, which is movably arranged in a non-coal seam directional drilling well, The anode assembly is movably arranged in another non-coal seam directional drilling well and faces the cathode assembly. After the cathode assembly and the anode assembly are energized, high-voltage ionization is generated to heat and activate the reaction medium from the reaction medium injection pipe between the cathode assembly and the anode assembly.

2. A coal seam transferred arc plasma in-situ conversion enhancement system according to claim 1, characterized in that: The reaction medium injection pipe is connected to the flexible coiled pipe and moves in the coal seam as the flexible coiled pipe expands and contracts.

3. The coal seam transferred arc plasma in-situ conversion enhancement system according to claim 1, characterized in that: The reaction medium is carbon dioxide, water, nitrogen, hydrogen, air or enriched oxygen.

4. The coal seam transferred arc plasma in-situ conversion enhancement system according to claim 1, characterized in that: The cathode assembly or the anode assembly is composed of electrodes and cables, and the electrodes are graphite, copper or copper-based alloy conductive materials.

5. A coal seam transferred arc plasma in-situ conversion enhancement system according to claim 4, characterized in that: The length of the electrode is 5~500m, one end of the cable is connected to the electrode and the other end is on the ground.

6. A coal seam transferred arc plasma in-situ conversion enhancement system according to claim 4, characterized in that: The cables of the cathode assembly and the anode assembly are coated with high-strength materials, and the cables are dragged from the ground to move the positions of the cathode and anode assemblies in the directional drilling well.

7. The coal seam transferred arc plasma in-situ conversion enhancement system according to claim 1, characterized in that: The cathode assembly and the anode assembly can be interchanged, and the cathode assembly and the anode assembly can be completely opposite or staggered by a certain distance in the horizontal direction.

8. A strengthening method using a coal seam transferred arc plasma in-situ conversion strengthening system according to any one of claims 1 to 7, characterized in that: These include, Vertical drilling from the ground to the underground forms a vertical channel from the ground surface to the center line of the coal seam, and then gradually deflects to the horizontal direction to form a non-vertical channel inside the coal seam, thereby obtaining a coal seam directional drilling well. Vertical drilling from the ground to the underground forms a vertical channel from the ground surface to a certain distance from the coal seam, and then gradually deflects to the horizontal direction to form a non-vertical channel close to the top plate or bottom plate of the coal seam, thereby obtaining two non-coal seam directional drilling wells. Vertical drilling from the ground to the underground until the coal seam is passed through and connected with the coal seam directional drilling well to obtain a vertical well. The reaction medium injection pipe is located in the coal seam directional drilling well. One end of the reaction medium injection pipe is lowered to the designated area in the coal seam, and the other end is located on the ground. The injection flow and composition are controlled by the ground. The reaction medium injection pipe is debugged on the ground, and the reaction medium in and out circulation is tested. The power is turned on, and the startup and power adjustment of the transferred arc plasma generator are tested to be normal. A certain flow of reaction medium is injected into the reaction medium injection pipe from the ground. The flow data of the vertical well outlet test is used to determine whether the conversion channel and the vertical well are unobstructed. After confirming that the conversion channel and the vertical well are unobstructed, the reaction medium is injected into the reaction medium injection pipe from the ground, and the power start switch of the cathode assembly and the anode assembly is turned on to start the transferred arc plasma generator. Test the outlet gas composition, flow rate and temperature data from the vertical well outlet. When the outlet gas composition, flow rate and temperature of the vertical well meet the standards, it indicates that the coal seam has started the conversion reaction. Gradually adjust the reaction medium flow rate injected into the reaction medium injection pipe and the power of the transferred arc plasma generator to keep the production load between 50% and 60% and start the coal seam conversion production. After a period of normal production, when the vertical well feedback outlet gas flow rate continues to decline, it indicates that the coal seam conversion reaction intensity decreases with the increase of the reaction cavity. At this time, increase the reaction medium flow rate injected into the reaction medium injection pipe and the power of the transferred arc plasma generator to increase the conversion reaction load to 80% to 100% and continue production. After a period of time, the vertical well test device feedback outlet gas flow rate further declines, indicating that the coal seam covered between the reaction medium injection pipe and the vertical well has been converted. The cathode assembly, anode assembly and reaction medium injection pipe are all withdrawn 10 to 100 meters under ground control to continue the coal seam conversion production. The production is adjusted in this way according to the statistics of the movement distance of the reaction medium injection pipe. If the difference between the non-vertical channel distance of the coal seam directional drilling and the movement distance of the reaction medium injection pipe is close to the retreat distance of the reaction medium injection pipe each time, it indicates that the coal seam covered by the unit has been converted. The power supply of the cathode assembly and the anode assembly is turned off, the injection of the reaction medium is stopped, and the cathode assembly, anode assembly and reaction medium injection pipe are withdrawn to the ground respectively, and the well is shut in. Construction, installation and conversion production are carried out in another target coal seam block. The cycle is repeated until the end.

Images