Coal seam in-situ plasma conversion methane production system

Abstract

In the coal seam in-situ plasma conversion methane production system, at least one directional drilling well vertically penetrates through a covering layer and the upper edge of a coal seam from the ground to form a vertical channel, and gradually deflects in the horizontal direction to form a non-vertical channel in the coal seam; the vertical well vertically penetrates through a covering layer and a coal seam from the ground by taking a coordinate at the tail end of the non-vertical channel as a target spot to be communicated with the non-vertical channel; the plasma generator is movably arranged in a coal seam channel; the plasma generator receives a working medium and a cooling medium from the working medium pipeline to ionize the working medium at high pressure to generate high-temperature high-activity water vapor particles and high-temperature high-activity hydrogen particles, and the high-temperature high-activity water vapor particles and a coal seam are subjected to a reduction reaction to be converted into hydrogen and carbon monoxide; the high-temperature high-activity hydrogen particles and the high-temperature high-activity hydrogen particles are subjected to methanation reaction in the reaction cavity in situ to generate methane, and the methane is output from the vertical well. The system is high in conversion efficiency and high and stable in production intensity.

Description

Technical Field

[0001] The utility model relates to the technical field of coal seam gasification, in particular to a coal seam in-situ plasma conversion methane production system. Background Art

[0002] In-situ coalbed gasification (ISG) technology converts underground coal into products such as methane, hydrogen, and carbon monoxide. However, the methane in ISG coal gas primarily originates from the pyrolysis reaction in the coal seam. Therefore, the methane content in the gas is generally around 10%, with the remaining 40-50% being hydrogen and carbon monoxide, along with the production of approximately 40% carbon dioxide. This leads to significant carbon emissions during the production of methane from coalbed methane. Furthermore, the remaining hydrogen and carbon monoxide must undergo surface purification, separation, conversion, and methanation to further synthesize natural gas. This long and complex process increases investment and production costs. Furthermore, traditional ISG methods involve a spontaneous reaction between dense underground coal seams and oxidants or gasifying agents, resulting in low conversion efficiency and production intensity. Due to the complex underground coal seam environment, interbedded coal gangue, groundwater inflow, and the expansion of the reaction chamber all severely impact the conversion reaction, making it difficult to ensure an efficient and stable supply of natural gas.

[0003] Therefore, the current coal seam in-situ gasification technology is expected to become an important supplement to my country's natural gas supply, but it has problems such as long process flow, large carbon emissions, high production costs, low conversion efficiency, and low production intensity. In order to ensure the efficient and stable supply of natural gas, a more optimized coal seam in-situ plasma conversion methane production system is urgently needed to efficiently and stably convert underground coal seams into natural gas products.

[0004] The above information disclosed in the background technology section is only for enhancing understanding of the background of the present invention and therefore may contain information that does not constitute the prior art known to ordinary technicians in this field. Utility Model Content

[0005] The purpose of this utility model is to provide a coal seam in-situ plasma conversion methane production system. In order to solve the current problems of long process flow, large carbon emissions, high production costs, low conversion efficiency, and low production intensity, a plasma generator that can simultaneously produce hydrogen and water vapor active particles is constructed in the coal seam. The high-temperature and highly active water vapor particles generated by the high-voltage ionization of the plasma generator undergo a reduction reaction with the coal seam to be converted into hydrogen and carbon monoxide. The high-temperature and highly active water vapor particles further undergo a methanation reaction in situ in the reaction chamber with the high-temperature and highly active hydrogen particles generated by the high-voltage ionization of the plasma generator. The produced methane gas is discharged to the ground through a vertical well and can be used as a natural gas product after purification and separation. The conversion and methanogenic stages of coal seam gasification on the ground are eliminated, the process flow is shortened, and the production cost is reduced; only a small amount of by-products such as carbon dioxide are produced, which is environmentally friendly; due to the action of the high-temperature and highly active particles, the underground in-situ conversion reaction is strengthened, the conversion effect is high, and the production intensity is high. In order to achieve the above-mentioned purpose, the utility model provides the following technical solutions:

[0006] The utility model discloses a coal seam in-situ plasma conversion methane production system comprising:

[0007] At least one directional drilled well, which vertically penetrates the overburden and the upper edge of the coal seam from the ground to form a vertical channel, and gradually deflects horizontally to form a non-vertical channel in the coal seam.

[0008] A vertical well, which takes the coordinates at the end of the non-vertical channel as the target point, vertically penetrates the overburden and coal seam from the ground and connects with the non-vertical channel. The non-vertical channel between the directional drilling well and the vertical well is the coal seam channel;

[0009] A gas injection assembly, one end of which is connected to a gas injection pipe moving device located on the ground, and the other end is connected to a plasma generator; the plasma generator can be movably arranged in the coal seam channel, and the plasma generator is used to receive the working medium from the working medium pipeline, and generate methane through a high-pressure ionization of the working medium and the coal seam to produce a reduction reaction, and the methane is output from the vertical well.

[0010] Optionally, there are two directional drilling wells, namely a first directional drilling well and a second directional drilling well, and the gas injection assembly includes a gas injection pipe and a second gas injection pipe;

[0011] The gas injection pipe is arranged in the directional drilling well, and the end of the gas injection pipe located in the coal seam is connected to the plasma generator, and the gas injection pipe is used to transport the first working medium to the plasma generator;

[0012] The second gas injection pipe is arranged in the second directional drilling well, and the end of the second gas injection pipe located in the coal seam is connected to the second plasma generator. The second gas injection pipe is used to transport a second working medium to the second plasma generator, so that the first working medium and the second working medium undergo a reduction reaction with the coal seam under the action of high-voltage ionization to produce methane; wherein, the first working medium is hydrogen and the second working medium is water vapor.

[0013] Optionally, the directional drilling is one, and the gas injection assembly includes a single gas injection pipe;

[0014] The gas injection pipe is arranged in the directional drilling well, and is used to simultaneously transport the first working medium and the second working medium to the plasma generator, so that the first working medium and the second working medium undergo a reduction reaction with the coal seam under high-pressure ionization to produce methane.

[0015] Optionally, a pipeline is arranged from the ground to the coal seam in the vertical well, and sieve holes are arranged in the pipeline located in the coal seam to filter the output methane.

[0016] Optionally, the plasma generator and the second plasma generator are provided on the same side of the vertical well and arranged opposite to each other.

[0017] Optionally, the plasma generator and the second plasma generator are provided on both sides of the vertical well and arranged opposite to each other.

[0018] Optionally, the gas injection pipe and the second gas injection pipe are both made of high temperature resistant, corrosion resistant and hydrogen embrittlement resistant steel pipe, alloy pipe, carbon fiber pipe or composite material pipe.

[0019] Optionally, the horizontal angle of the vertical channel is between 75° and 105°, and the horizontal angle of the non-vertical channel is between 0° and 20°.

[0020] Optionally, the length of the coal seam channel is 100m to 3000m.

[0021] Optionally, a test device for detecting the gas flow rate and components of the gas is arranged at the wellhead of the vertical well located on the ground.

[0022] In the above-mentioned technical solution, the utility model provides an in-situ coal seam plasma conversion methane production system with the following beneficial effects: by constructing a plasma generator capable of simultaneously generating hydrogen and water vapor active particles in the coal seam, the high-temperature, highly active water vapor particles generated by high-voltage ionization of the plasma generator undergo a reduction reaction with the coal seam to be converted into hydrogen and carbon monoxide. The water vapor particles then undergo an in-situ methanation reaction with the high-temperature, highly active hydrogen particles generated by high-voltage ionization of the plasma generator within the reaction chamber, producing methane gas that is discharged to the surface via a vertical well and, after purification and separation, can be used as a natural gas product. This utility model eliminates the surface conversion and methanation stages of coal seam gasification, shortening the process flow and reducing production costs. It produces only a small amount of byproducts such as carbon dioxide, making it environmentally friendly. Due to the action of the high-temperature, highly active particles, the underground reaction is enhanced, resulting in a high conversion efficiency and high production intensity. It can be used for the development and utilization of carbon-based energy sources such as coal, peat, oil sands, coal gangue, oil shale, and heavy oil formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. 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.

[0024] Figure 1 A schematic structural diagram of a coal seam in-situ plasma conversion methane production system provided in one embodiment of the present invention.

[0025] Figure 2 A schematic structural diagram of a coal seam in-situ plasma conversion methane production system provided in another embodiment of the present invention.

[0026] Figure 3 A schematic structural diagram of a coal seam in-situ plasma conversion methane production system provided in yet another embodiment of the present invention. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, 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 only 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 making creative efforts are within the scope of protection of the present invention.

[0028] 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 claimed invention, but rather merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] 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, it does not require further definition or explanation in subsequent drawings.

[0030] 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 to 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 device or element referred to 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.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0032] In this utility model, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; they can refer to direct connection or indirect connection through an intermediate medium; they can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0033] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0034] 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.

[0035] See also Figures 1 to 3 As shown, the utility model provides a coal seam in-situ plasma conversion methane production system: comprising at least two directional drilling wells 5 and one vertical well 8, wherein two gas injection pipes 6 are respectively lowered from the directional drilling wells 5, and the gas injection pipes 6 are respectively connected to a plasma generator 7, and the plasma generator 7 uses water vapor and hydrogen as working media respectively; alternatively, the coal seam in-situ plasma conversion methane production system constructs a group of production wells and production wells in the coal seam, comprising at least one directional drilling well 5 and one vertical well 8, wherein one gas injection pipe 6 is lowered from the directional drilling well 5, and the gas injection pipe 6 is connected to a plasma generator 7 that can simultaneously inject hydrogen and water as working media. The process of in-situ plasma conversion of methane production in coal seams is to construct a plasma generator 7 in the coal seam that can simultaneously generate hydrogen and water vapor active particles. The high-temperature and highly active water vapor particles generated by the high-voltage ionization of the plasma generator 7 undergo a reduction reaction with the coal seam to be converted into hydrogen and carbon monoxide. The water vapor particles then undergo a methanation reaction in situ with the high-temperature and highly active hydrogen particles generated by the high-voltage ionization of the plasma generator 7 in the reaction chamber 9, producing methane gas that is discharged to the ground 4 through a vertical well 8 and can be used as a natural gas product after purification and separation.

[0036] In a specific embodiment, Figure 1 As shown, a coal seam in-situ plasma conversion methane production system of the utility model includes:

[0037] A directional drill well 5 is drilled vertically from the ground 4 through the overburden 3 and the upper edge of the coal seam 1 to form a vertical channel, and gradually deflects horizontally to form a non-vertical channel in the coal seam.

[0038] The vertical well 8 is connected to the non-vertical channel by vertically passing through the overburden 3 and the coal seam 1 from the ground 4 with the coordinates at the end of the non-vertical channel as the target point. The non-vertical channel between the directional drilling well 5 and the vertical well 8 is the coal seam channel 2. The vertical well 8 arranges a pipeline from the ground to the coal seam, and a sieve hole is arranged in the pipeline located in the coal seam to filter the output methane.

[0039] The gas injection assembly includes a single gas injection pipe 6, one end of which is connected to a gas injection pipe moving device located on the ground 4 for moving the gas injection pipe 6, and the other end of the gas injection pipe 6 is connected to the plasma generator 7. The gas injection pipe 6 includes a power cable, a working medium pipeline and a cooling medium pipe, which are used to transport the working medium and cooling medium to the plasma generator 7, wherein the working medium includes hydrogen and water or reaction media such as carbon dioxide.

[0040] The plasma generator 7 is movably arranged in the coal seam channel 2. The plasma generator 7 receives the working medium and the cooling medium from the working medium pipeline and ionizes the working medium at high pressure to generate high-temperature and high-activity water vapor particles and high-temperature and high-activity hydrogen particles. The high-temperature and high-activity water vapor particles react with the coal seam to be converted into hydrogen and carbon monoxide, which react with the high-temperature and high-activity hydrogen particles in situ in the reaction chamber 9 to produce methane. The methane is output from the vertical well 8.

[0041] Specifically, the gas injection pipe 6 is connected to a plasma generator 7 that can simultaneously use hydrogen and water as working media. A series of conversion reactions occur within the coal seam, producing methane-rich gas. The coal seam in-situ plasma conversion methane production system comprises a coal seam channel 2, a directional drilling well 5, a gas injection pipe 6, a plasma generator 7, and a vertical well 8. After vertically penetrating the overburden 3 and the upper edge of the coal seam from the ground 4, it gradually deflects horizontally, forming a non-vertical channel within the coal seam. The non-vertical channel extends a certain distance within the coal seam, forming the directional drilling well 5. Using the coordinates of the end of the non-vertical channel as the target point, the directional drilling well 5 vertically penetrates the overburden 3 and the coal seam from the ground 4 to connect with the non-vertical channel. The non-vertical channel between the directional drilling well 5 and the vertical well 8 is the coal seam channel 2. At least one directional drilling well 5 and one vertical well 8 constitute a coal seam gasification unit. The horizontal angle of the non-vertical channel is between 0 and 20 degrees, and the horizontal angle of the vertical channel is between 75 and 105 degrees.

[0042] The directional drilling well 5 is provided with a gas injection pipe moving device, an injection device, and a control device on the ground 4. The gas injection pipe 6 has one end located on the ground 4 and the other end connected to a plasma generator. The gas injection pipe 6 is connected to the plasma generator and then lowered into the directional drilling well 5. The gas injection pipe 6 is controlled by the ground 4 and moved to the target area of ​​the coal seam channel 2.

[0043] The gas injection pipe 6 can be made of a steel, alloy, carbon fiber, or composite material tube that is resistant to high temperatures, corrosion, and hydrogen embrittlement. It can house the power cables, working medium pipelines, and cooling medium pipelines that accompany the plasma generator 7. These power cables, working medium pipelines, and cooling medium pipelines are connected to the injection device and control device on the surface 4 at one end and to the plasma generator 7 at the other. The plasma generator 7 is capable of operating simultaneously with either hydrogen and water or hydrogen and carbon dioxide as the media.

[0044] The coal seam channel 2 may have a length of 100 to 3000 m according to process design.

[0045] The bottom of vertical well 8 is located near the bottom of the coal seam. Screen holes are placed in the pipeline below the coal seam to facilitate the discharge of product gas. At the wellhead of vertical well 8, located on the surface 4, a device for measuring product gas flow rate, composition, and other parameters is installed to provide feedback on coal seam reactions and provide a basis for regulating in-situ methane production in the coal seam.

[0046] The utility model discloses the specific reaction process of the coal seam in-situ plasma conversion methane production system. The coal seam plasma generator 7 can excite and dissociate the working medium such as hydrogen and water into high-temperature and highly active particles such as hydrogen free radicals and hydroxyl free radicals through high-voltage ionization. The high-temperature and highly active particles react with the coal seam to produce efficient conversion reactions, including but not limited to:

[0047] H2 + e - → H * + H * + e - (1)

[0048] H2O + e - → OH * + H * + e - (2)

[0049] C + H * → CH * (3)

[0050] CH * + OH * → CO + H2 (4)

[0051] CH * + 3H * → CH4 (5)

[0052] H * + H * → H2 (6)

[0053] As can be seen from the above reactions, hydrogen and water, dissociated by plasma generator 7, form high-temperature, highly reactive particles such as hydrogen radicals and hydroxyl radicals, which react with the carbon in the coal seam in a series of reactions, transforming them into hydrogen, carbon monoxide, and methane. As the coal seam conversion reaction proceeds, several groups of reaction chambers 9 gradually form. The maximum height of a single reaction chamber 9 approaches the height of the coal seam, and the maximum width exceeds 34 meters.

[0054] The high-temperature, high-activity particles react with the carbon in the coal seam to convert hydrogen, carbon monoxide, and methane, etc., which flow within the reaction chamber 9 and the coal seam channel 2. During the flow, hydrogen, carbon monoxide, etc. are further converted by the active action of hydrogen-containing free radicals and the catalytic action of the silicon-aluminum-iron-calcium-magnesium ash in the reaction chamber 9, including but not limited to:

[0055] CO + OH * = CO2 + H2 (6)

[0056] CO + H2 + H * → CH4 + H2O (7)

[0057] CO2 + H2 + H * →CH4 + H2O (8)

[0058] From the above reaction, it can be seen that hydrogen, carbon monoxide, etc. continue to undergo conversion reactions in the coal seam channel 2 and the reaction chamber 9 under the active action of hydrogen-containing free radicals and the catalytic action of silicon, aluminum, iron, calcium and magnesium ash in the reaction chamber 9, and finally generate a gas mainly composed of methane.

[0059] The production process of the coal seam in-situ plasma conversion methane production system includes:

[0060] After vertically passing through the overburden 3 and the upper edge of the coal seam from the ground 4, it gradually deflects to the horizontal direction, forming a non-vertical channel in the coal seam. The non-vertical channel extends a certain distance in the coal seam to form a directional drilling well 5; with the coordinates of the end of the directional drilling well 5 at the non-vertical channel as the target point, the vertical well 8 vertically passes through the overburden 3 and the coal seam from the ground 4 and is connected to the non-vertical channel. The non-vertical channel between the directional drilling well 5 and the vertical well 8 is the coal seam channel 2, and the vertical well 8 is located in the pipeline of the coal seam and a sieve hole is arranged.

[0061] After the gas injection pipe 6 is connected to the plasma generator, it is lowered to the directional drilling well 5 and controlled by the ground 4 to move it to the target area of ​​the coal seam channel 2. On the ground 4, the plasma generator 7 is debugged and the inflow and outflow of the reaction medium and the inflow and outflow of the cooling medium are tested. The power is turned on to test the startup and the reaction medium flow and power adjustment to ensure that they are normal. The plasma generator 7 is moved to the target area of ​​the coal seam channel 2 and the horizontal distance between the plasma generator 7 and the vertical well 8 in the coal seam channel 2 is 10 to 100 meters.

[0062] The plasma generator 7 is injected with a working medium of water and hydrogen at a molar ratio of 0.5 and a cooling medium by an injection device, and the plasma generator 7 is started. The plasma generator 7 receives the working medium and cooling medium from the working medium pipeline and ionizes the working medium at high pressure to produce high-temperature, high-activity water vapor particles and high-temperature, high-activity hydrogen particles. The high-temperature, high-activity water vapor particles react with the coal seam to be converted into hydrogen and carbon monoxide, which react with the high-temperature, high-activity hydrogen particles in situ in the reaction chamber 9 to produce methane.

[0063] When the volume percentage of CH4 in the gas at the outlet of vertical well 8 is higher than 10%, it indicates that the coal seam has started to convert. The water and hydrogen flow and power of plasma generator 7 are gradually adjusted to maintain the production load between 10% and 50%, and the coal seam conversion methane production is started.

[0064] If the vertical well 8 feedback indicates that the volume ratio of carbon dioxide in the outlet gas exceeds 5%, the water injection rate is maintained unchanged, and the hydrogen injection rate of the plasma generator 7 is slowly increased until the volume ratio of carbon dioxide in the outlet gas is less than 5%. If the feedback indicates that the volume ratio of hydrogen in the outlet gas exceeds 5%, the water injection rate of the plasma generator 7 is slowly increased until the volume ratio of hydrogen in the outlet gas is close to 0 and the volume ratio of carbon dioxide is 5%. The injection device of the gas injection pipe 6 controls the water and hydrogen injection rates so that the molar ratio of water and hydrogen injected into the plasma generator 7 is between 0.5 and 0.6. When the outlet gas is normal, the water and hydrogen ratio injected into the plasma generator 7 is maintained unchanged, and the water and hydrogen injection rates and the power of the plasma generator 7 are slowly adjusted to stabilize the production load at 50%.

[0065] When the test device of vertical well 8 reports that the outlet gas flow rate continues to decrease, the water and hydrogen injection flow rates and power of plasma generator 7 are increased to increase the conversion reaction load to 60% to 100%. When the outlet gas flow rate of vertical well 8 reports a further decrease, it indicates that the conversion of the coal seam between plasma generator 7 and vertical well 8 is complete. The plasma generator 7 is kept in the started state, and the gas injection pipe moving device 4 on the ground is used to withdraw the plasma generator 7 10 to 100 meters to continue the coal seam conversion production. The production is adjusted in this cycle. When the movement distance of plasma generator 7 approaches the distance of the non-vertical section of the coal seam, the power supply of plasma generator 7 is turned off, the injection of reaction medium is stopped, the injection of cooling medium is maintained, and the gas injection pipe 6 and plasma generator 7 are respectively withdrawn to the ground 4.

[0066] Example 1

[0067] The coal seam gasification methane production system proposed in the embodiment of the utility model has a coal seam resource buried at a depth of about 1360m, an average thickness of 6m, anthracite coal, and a conversion unit is designed to cover a horizontal distance of 1000m in the coal seam.

[0068] After vertically penetrating the overburden 3 and the upper edge of the coal seam from the ground 4, it gradually deflects horizontally, forming a non-vertical channel within the coal seam. The non-vertical channel extends approximately 1000 meters into the coal seam, forming a directional well 5. Using the coordinates of the end of the non-vertical channel as the target point, the directional well 5 vertically penetrates the overburden 3 and the coal seam from the ground 4 to connect with the non-vertical channel. The horizontal angle of the non-vertical channel is 3°, while the horizontal angle of the vertical channel is 91°.

[0069] The directional drilling 5 is provided with a gas injection pipe moving device, an injection device and a control device on the ground 4. One end of the gas injection pipe 6 is located on the ground 4, and the other end is connected to the plasma generator. After the gas injection pipe 6 is connected to the plasma generator, it is lowered to the directional drilling 5 and is controlled by the ground 4 to move to the target area of ​​the coal seam channel 2. The gas injection pipe 6 can be a steel pipe, alloy pipe, carbon fiber pipe or composite material pipe with high temperature resistance, corrosion resistance and hydrogen embrittlement resistance. The inside can be covered with the power cable, working medium pipeline, cooling medium pipeline and the like that are matched with the plasma generator 7. The matched power cable, working medium pipeline and cooling medium pipeline are connected to the injection device and control device on the ground 4 at one end and to the plasma generator 7 at the other end. The plasma generator 7 has the function of working with hydrogen and water or hydrogen and carbon dioxide as media at the same time.

[0070] The bottom of the vertical well 8 is close to the bottom of the coal seam, wherein sieve holes are arranged in the pipeline located in the coal seam. Parameter test equipment such as product gas flow rate and composition is arranged at the wellhead position of the vertical well 8 located on the ground 4.

[0071] After the coalbed gasification unit was fabricated and all equipment installed according to the construction and installation methods, the plasma generator 7 was debugged on the surface 4 to test the flow of reaction medium and cooling medium. The power was turned on to test the startup and reaction medium flow and power adjustment to ensure normal operation. The surface control device 4 moved the plasma generator 7 to a distance of approximately 30 meters from the vertical well 8.

[0072] The injection device injects 100Nm into the plasma generator 7 3 / h of hydrogen, and the flow data of the vertical well 8 testing device is used to test whether the coal seam channel 2 and the vertical well 8 are unobstructed.

[0073] After confirming that the conversion channel and the recovery pipe are unobstructed, the injection device injects hydrogen into the plasma generator 7 at a flow rate of 200Nm 3 / h, injecting water at a rate of approximately 80kg / h and a cooling medium. Turn on the power start switch, adjust the power of plasma generator 7 to approximately 500kW, maintain the load of plasma generator 7 between 10% and 50%, and start plasma generator 7. Feedback from the testing device components at vertical well 8 indicates that when the volume percentage of CH4 in the gas at the outlet of vertical well 8 exceeds 10%, it indicates that the coal seam conversion reaction has begun. Gradually adjust the water and hydrogen flow rates and power of plasma generator 7 to maintain the production load between 10% and 50%, so that the molar ratio of water to hydrogen injected by plasma generator 7 and the second plasma generator 10 is between 0.5 and 0.6. At this point, the coal gas produced primarily consists of methane, water vapor, and a very small amount of carbon dioxide, and coal seam conversion methane production begins.

[0074] After three days of continuous normal production, the test device of vertical well 8 reported that the volume ratio of carbon dioxide in the outlet gas exceeded 5%, indicating that the coal seam contained too much water and the molar ratio of water to hydrogen was too high. The hydrogen injection flow rate of plasma generator 7 was slowly increased until the volume ratio of carbon dioxide in the outlet gas was lower than 5%.

[0075] After 7 days of continuous production, the test device of vertical well 8 reported that the outlet gas flow rate continued to decline, indicating that the conversion reaction intensity of the coal seam decreased with the increase of the reaction cavity. At this time, the hydrogen injection flow rate of plasma generator 7 was increased to 400Nm 3 / h, the water flow rate is increased to about 160kg / h, the plasma generator 7 reaches about 1000kW, the conversion reaction load is increased to 60% to 100%, and production continues.

[0076] Six days later, the test equipment at vertical well 8 reported a further decrease in the outlet gas flow rate, indicating that the coal seam between plasma generator 7 and vertical well 8 had been completely converted. With plasma generator 7 still active, the surface gas injection pipe moving device (4) was used to withdraw plasma generator 7 approximately 30 meters, and coal seam conversion production continued.

[0077] Production was adjusted in this cycle. Based on the distance traveled by the surface gas injection pipe moving device (4), plasma generation and retreat distance approached 970 meters, indicating that the overlying coal seam in this unit had been completely converted. The power to plasma generator 7 was turned off, and the injection of reaction medium ceased. While maintaining the injection of cooling medium, plasma generator 7 was withdrawn to the surface (4). The well was shut-in. Following the above method, construction, installation, and gasification production were carried out in another target coal seam block.

[0078] In another specific embodiment, Figure 2 and Figure 3As shown, in the coal seam in-situ plasma conversion methane production system, the end coordinates of the non-vertical channel of the directional drilling well 5 are the target point. It also passes vertically from the ground 4 through the overburden 3 and the upper edge of the coal seam 1, and gradually deflects from the coal seam toward the target point until it penetrates to form a second directional drilling well 11. The non-vertical channel connecting the directional drilling well 5 and the directional drill in the coal seam is the coal seam channel 2.

[0079] Between the directional well 5 and the second directional well 11, a vertical channel is formed from the ground 4 vertically through the overburden 3 and the coal seam, serving as a vertical well 8. The gas injection assembly includes a gas injection pipe 6 and a second gas injection pipe 12. The directional well 5 is provided with the gas injection pipe 6 and a plasma generator 7. The second directional well 11 is provided with the second gas injection pipe 12 and a second plasma generator 10 connected to the second gas injection pipe 12. The second plasma generator 10 receives working medium and cooling medium from the working medium pipeline and ionizes the working medium at high pressure to produce high-temperature, highly active water vapor particles and high-temperature, highly active hydrogen particles. The high-temperature, highly active water vapor particles undergo a reduction reaction with the coal seam to be converted into hydrogen and carbon monoxide. The high-temperature, highly active water vapor particles react with the high-temperature, highly active hydrogen particles in situ to produce methane through a methanation reaction within the reaction chamber 9. The gas injection pipe 6 delivers hydrogen to the plasma generator 7, and the second gas injection pipe 12 delivers water or carbon dioxide to the second plasma generator 10.

[0080] Example 2

[0081] like Figure 2 As shown, in the coal seam in-situ plasma conversion methane production system, the plasma generator 7 and the second plasma generator 10 are arranged on the same side of the vertical well 8 and are arranged opposite to each other.

[0082] like Figure 2 As shown, the coal seam in-situ plasma conversion methane production system includes at least two directional drilling wells 5 and one vertical well 8. Two gas injection pipes are respectively lowered into the directional drilling wells 5, and the gas injection pipes are respectively connected to plasma generators. The plasma generators use water and hydrogen as working media, respectively, to produce a series of conversion reactions in the coal seam to produce methane-rich gas.

[0083] The coal seam in-situ plasma conversion methane production system includes a coal seam channel 2, a directional drill 5, a gas injection pipe 6, a plasma generator 7, and a vertical well 8. After vertically penetrating the overburden 3 and the upper edge of the coal seam from the ground 4, it gradually deflects horizontally, forming a non-vertical channel within the coal seam. The non-vertical channel extends a certain distance into the coal seam, forming the directional drill 5. With the coordinates of the end of the non-vertical channel of the directional drill 5 as the target point, the directional drill 5 also vertically penetrates the overburden 3 and the upper edge of the coal seam from the ground 4, gradually deflecting from the coal seam toward the target point until it penetrates, forming a second directional drill 11. The non-vertical channel connecting the directional drill 5 and the second directional drill 11 in the coal seam is the coal seam channel 2. Between the directional drill 5 and the second directional drill 11, a vertical channel is formed vertically penetrating the overburden 3 and the coal seam from the ground 4, forming the vertical well 8. At least two directional drills and one vertical well 8 constitute a coal seam gasification unit. The horizontal angle of the non-vertical channel is between 0 and 20 degrees, and the horizontal angle of the vertical channel is between 75 and 105 degrees.

[0084] The directional drilling 5 is provided with a gas injection pipe moving device, an injection device and a control device on the ground 4. One end of the gas injection pipe 6 is located on the ground 4, and the other end is connected to the plasma generator. After the gas injection pipe 6 is connected to the plasma generator, it is lowered to the directional drilling 5 and controlled by the ground 4 to move to the target area of ​​the coal seam channel 2. The gas injection pipe 6 can be a steel pipe, alloy pipe, carbon fiber pipe or composite material pipe with high temperature resistance, corrosion resistance and hydrogen embrittlement resistance. The inside can be covered with the power cable, working medium pipeline, cooling medium pipeline and the like that are matched with the plasma generator 7. The matched power cable, working medium pipeline and cooling medium pipeline are connected to the injection device and control device on the ground 4 at one end and connected to the plasma generator 7 at the other end. The plasma generator 7 has the function of working with media such as hydrogen, water and carbon dioxide.

[0085] The second directional drilling well 11 is provided with a gas injection pipe moving device, an injection device and a control device on the ground 4. One end of the second gas injection pipe 12 is located on the ground 4, and the other end is connected to the second plasma generator 10. After the second gas injection pipe 12 is connected to the second plasma generator, it is lowered to the second directional drilling well 11 and is controlled by the ground 4 to move to the target area of ​​the coal seam channel 2. The second gas injection pipe 12 can be a steel pipe, alloy pipe, carbon fiber pipe or composite material pipe with high temperature resistance, corrosion resistance and hydrogen embrittlement resistance. The inside can be covered with the power cable, working medium pipeline, cooling medium pipeline, etc. that are matched with the second plasma generator 10. The matched power cable, working medium pipeline and cooling medium pipeline are connected to the injection device and control device on the ground 4 at one end and connected to the second plasma generator 10 at the other end. The second plasma generator 10 has the function of working with media such as hydrogen, water and carbon dioxide.

[0086] The coal seam channel 2 may have a length of 100 to 3000 m according to process design.

[0087] The bottom of vertical well 8 is located near the bottom of the coal seam, and screen holes are placed in the pipeline within the coal seam to facilitate the discharge of product gas. At the wellhead of vertical well 8, located on the surface 4, a device for measuring product gas flow rate, composition, and other parameters is installed to provide feedback on coal seam reactions and provide a basis for controlling the specific process of in-situ methane production in the coal seam.

[0088] Example 3

[0089] like Figure 3 As shown, in the coal seam in-situ plasma conversion methane production system, the plasma generator 7 and the second plasma generator 10 are provided on both sides of the vertical well 8 and arranged opposite to each other.

[0090] like Figure 3 As shown, after vertically penetrating the overburden 3 and the upper edge of the coal seam from the ground 4, it gradually deflects horizontally, forming a non-vertical channel within the coal seam. The non-vertical channel extends a certain distance into the coal seam, forming a directional well 5. With the coordinates of the end of the non-vertical channel of the directional well 5 as the target point, the directional well 5 also vertically penetrates the overburden 3 and the upper edge of the coal seam from the ground 4, gradually deflecting from the coal seam toward the target point until it penetrates, forming a second directional well 11. The non-vertical channel connecting the directional well 5 and the second directional well 11 in the coal seam is the coal seam channel 2, which is approximately 1200 meters long. Between the directional well 5 and the second directional well 11, a vertical channel is formed vertically penetrating the overburden 3 and the coal seam from the ground 4, namely the vertical well 8. The two directional wells and the one vertical well 8 constitute a coal seam gasification unit. The horizontal angle of the non-vertical channel is approximately 5°, and the horizontal angle of the vertical channel is approximately 85°.

[0091] The directional drilling 5 is equipped with a gas injection pipe moving device, an injection device, and a control device on the ground 4. One end of the gas injection pipe 6 is located on the ground 4, and the other end is connected to the plasma generator. After the gas injection pipe 6 is connected to the plasma generator, it is lowered to the directional drilling 5 and controlled by the ground 4 to move to the target area of ​​the coal seam channel 2. The gas injection pipe 6 is internally covered with a power cable, working medium pipeline, cooling medium pipeline, etc. that are matched with the plasma generator 7. The matched power cable, working medium pipeline, and cooling medium pipeline are connected to the injection device and control device on the ground 4 at one end and to the plasma generator 7 at the other end. The plasma generator 7 functions by using hydrogen as the medium.

[0092] The second directional wellbore 11 is equipped with a gas injection pipe moving device, injection device, and control device at the surface 4. One end of the second gas injection pipe 12 is located at the surface 4, and the other end is connected to a second plasma generator. After being connected to the second plasma generator, the second gas injection pipe 12 is lowered into the second directional wellbore 11 and controlled by the surface 4 to move to the target area of ​​the coal seam channel 2. The interior of the second gas injection pipe 12 can house the power cables, working medium pipelines, cooling medium pipelines, and other components of the second plasma generator 10. The power cables, working medium pipelines, and cooling medium pipelines are connected to the injection device and control device at the surface 4 at one end and to the second plasma generator 10 at the other end. The second plasma generator 10 is capable of operating with water as the medium. The vertical well 8 is located centrally between the directional well 5 and the second directional well 11. The vertical well 8 and the two directional wells 5 are both located approximately 500 meters apart. The bottom of the vertical well 8 is close to the bottom of the coal seam, and sieve holes are installed in the pipelines located in the coal seam. Equipment for testing parameters such as product gas flow rate and composition is located at the wellhead of the vertical well 8 at the surface 4.

[0093] After the coalbed gasification unit was completed and all equipment was installed according to the construction and installation methods, the plasma generator 7 and the second plasma generator 10 were debugged on the surface 4 to test the flow of reaction medium and the circulation of cooling medium. The power was turned on to test the startup and the reaction medium flow and power adjustment. The control device on the surface 4 moved the plasma generator 7 and the second plasma generator 10 respectively, so that the plasma generator 7 and the second plasma generator 10 were located on either side of the vertical well 8, with the plasma generator 7 approximately 825 meters from the vertical well and the second plasma generator 10 approximately 825 meters from the vertical well.

[0094] The injection device injects 100 Nm³ / h of hydrogen into plasma generator 7. The flow rate data from the vertical well 8 test device confirms the unobstructed coal seam channel 2 and vertical well 8. After confirming that the conversion channel and recovery pipe are unobstructed, the injection device injects approximately 300 Nm³ / h of hydrogen into plasma generator 7 and approximately 120 kg / h of water into the second plasma generator 10, along with a cooling medium. The power starter is turned on, and the power of both plasma generators 7 and 10 is adjusted to approximately 500 kW, maintaining the load of plasma generator 7 between 10% and 50%, before starting plasma generator 7. The composition feedback from the vertical well 8 test device indicates that the conversion reaction has begun in the coal seam when the volume percentage of CH₄ in the gas at the outlet of vertical well 8 exceeds 10%. Gradually adjust the water and hydrogen flow and power of the plasma generator 7 to maintain the production load between 10% and 50%, so that the molar ratio of water and hydrogen injected by the plasma generator 7 and the second plasma generator 10 is between 0.5 and 0.6. At this time, the coal gas components produced mainly include methane, water vapor and a very small amount of carbon dioxide, and coal seam conversion methane production begins.

[0095] After three days of continuous normal production, the test device of vertical well 8 reported that the volume ratio of hydrogen in the outlet gas exceeded 5%, indicating that the molar ratio of water to hydrogen was too low. The water injection flow rate of the second plasma generator 10 was slowly increased until the volume ratio of hydrogen in the outlet gas was close to 0 and the volume ratio of carbon dioxide was around 5%.

[0096] After 7 days of continued production, the test device of vertical well 8 reported that the outlet gas flow rate continued to decline, indicating that as the reaction cavity of the coal seam increased, the conversion reaction intensity decreased. At this time, the hydrogen injection flow rate of plasma generator 7 was increased to about 600Nm3 / h, and the water injection flow rate of the second plasma generator 10 was about 240kg / h. The power of plasma generator 7 and the second plasma generator 10 both reached about 1000kW, which increased the conversion reaction load to 60% to 100%, and production continued.

[0097] Five days later, the test equipment at vertical well 8 reported a further decrease in the outlet gas flow rate, indicating that the coal seam between plasma generator 7 and second plasma generator 10 had been completely converted. Plasma generator 7 remained activated, and the surface gas injection pipe moving device 4 moved plasma generator 7 and second plasma generator 10 approximately 25 meters back, allowing coal seam conversion production to continue.

[0098] Production was adjusted in this cycle. According to the distance statistics of the surface gas injection pipe moving device, when the plasma generator 7 retreated to approximately 575 meters, the coal seam covering this unit had been completely converted. The power to the plasma generator 7 was turned off, the injection of the reaction medium was stopped, the injection of the cooling medium was maintained, and the plasma generator 7 was withdrawn to the surface. The well was shut-in. Following the above method, construction, installation, and gasification production were carried out in another target coal seam block.

[0099] Finally, it should be noted that the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of this application.

[0100] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description 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 in-situ plasma conversion methane production system, characterized in that: These include, At least one directional drilled well, which vertically penetrates the overburden and the upper edge of the coal seam from the ground to form a vertical channel, and gradually deflects horizontally to form a non-vertical channel in the coal seam. A vertical well, which takes the coordinates at the end of the non-vertical channel as the target point, vertically penetrates the overburden and coal seam from the ground and connects with the non-vertical channel. The non-vertical channel between the directional drilling well and the vertical well is the coal seam channel; A gas injection assembly, one end of which is connected to a gas injection pipe moving device located on the ground, and the other end is connected to a plasma generator; the plasma generator can be movably arranged in the coal seam channel, and the plasma generator is used to receive the working medium from the working medium pipeline, and generate methane through a high-pressure ionization of the working medium and the coal seam to produce a reduction reaction, and the methane is output from the vertical well.

2. The coal seam in-situ plasma conversion methane production system according to claim 1, characterized in that: There are two directional drilling wells, namely a first directional drilling well and a second directional drilling well, and the gas injection assembly includes a gas injection pipe and a second gas injection pipe; The gas injection pipe is arranged in the directional drilling well, and the end of the gas injection pipe located in the coal seam is connected to the plasma generator, and the gas injection pipe is used to transport the first working medium to the plasma generator; The second gas injection pipe is arranged in the second directional drilling well, and the end of the second gas injection pipe located in the coal seam is connected to the second plasma generator. The second gas injection pipe is used to transport a second working medium to the second plasma generator, so that the first working medium and the second working medium undergo a reduction reaction with the coal seam under the action of high-voltage ionization to produce methane; wherein, the first working medium is hydrogen and the second working medium is water vapor.

3. The coal seam in-situ plasma conversion methane production system according to claim 1, characterized in that: There is one directional drilling well, and the gas injection assembly includes a single gas injection pipe; the gas injection pipe is arranged in the directional drilling well, and is used to simultaneously transport a first working medium and a second working medium to the plasma generator, so that the first working medium and the second working medium undergo a reduction reaction with the coal seam under the action of high-pressure ionization to produce methane.

4. The coal seam in-situ plasma conversion methane production system according to claim 1, characterized in that: The vertical well is provided with a pipeline from the ground to the coal seam, and sieve holes are arranged in the pipeline located in the coal seam for filtering the output methane.

5. The coal seam in-situ plasma conversion methane production system according to claim 2, characterized in that: The plasma generator and the second plasma generator are disposed on the same side of the vertical well and are arranged opposite to each other.

6. The coal seam in-situ plasma conversion methane production system according to claim 2, characterized in that: The plasma generator and the second plasma generator are provided on both sides of the vertical well and arranged opposite to each other.

7. The coal seam in-situ plasma conversion methane production system according to claim 2, characterized in that: The gas injection pipe and the second gas injection pipe are both made of high temperature resistant, corrosion resistant and hydrogen embrittlement resistant steel pipe, alloy pipe, carbon fiber pipe or composite material pipe.

8. The coal seam in-situ plasma conversion methane production system according to claim 1, characterized in that: The horizontal angle of the vertical channel is between 75° and 105°, and the horizontal angle of the non-vertical channel is between 0° and 20°.

9. The coal seam in-situ plasma conversion methane production system according to claim 1, characterized in that: The length of the coal seam passage is 100m to 3000m.

10. The coal seam in-situ plasma conversion methane production system according to claim 1, characterized in that: The vertical well is located at the wellhead position on the ground and is equipped with a testing device for detecting the gas flow rate and components.

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