High-efficiency low-rank coal bed methane mining device and method

Abstract

The application discloses a high-efficiency low-rank coal seam gas mining device and relates to the technical field of coal seam gas mining.The device comprises an outer horizontal pipe, which is arranged at a horizontal section of an L-shaped horizontal well and is fixedly connected with an outer vertical pipe; an inner horizontal pipe, which is coaxially arranged inside the outer horizontal pipe; an inner vertical pipe, which is arranged inside the outer vertical pipe and is fixedly connected with the inner horizontal pipe; a plurality of fracturing and extraction devices, which are horizontally distributed and connected with each other; and end portions of the fracturing and extraction devices adjacent to the outer horizontal pipe are fixedly connected with the outer horizontal pipe and the inner horizontal pipe; a sealing device, which is arranged at the left end of the fracturing and extraction device and corresponds to the fracturing and extraction device; and a coal powder precipitation device, which is arranged at the connection between the inner horizontal pipe and the inner vertical pipe.The device realizes the integration of fracturing and extraction, has no step limit and can realize long-term anti-blocking and high-efficiency mining of low-rank coal seam gas.

Description

Technical Field

[0001] This invention relates to the field of coalbed methane extraction technology, and more specifically, to a high-efficiency low-rank coalbed methane extraction device and method. Background Technology

[0002] Low-rank coalbed methane resources are abundant and widespread, but their reservoirs are characterized by soft coal bodies, low permeability, low gas content, and a tendency to produce pulverized coal, leading to inefficient conventional extraction methods. In existing technologies, vertical well extraction results in small controlled reserves per well, while horizontal wells, although increasing the venting area, require complex fracturing tools, are prone to bridge plug clogging, and often require additional procedures to keep the injection holes open after fracturing, increasing operation time and costs. More importantly, during drainage, pulverized coal enters the central pipe with the gas flow, clogging pump valves, wearing down screw pumps, and blocking formation fractures, causing rapid production decline, short pump inspection cycles, and frequent well workover operations, severely restricting the economical and efficient development of low-rank coalbed methane. Although some pulverized coal prevention measures exist, such as downhole screens and surface subsidence, they are either structurally simple with limited effectiveness or require frequent cleaning and maintenance, failing to fundamentally solve the pulverized coal clogging problem. Furthermore, in existing systems, fracturing and extraction often require the separate insertion of different tubing strings, resulting in cumbersome procedures. The number of fracturing stages is also limited by available tools, making it difficult to meet the demands of precise modification of long horizontal sections. Therefore, it is necessary to provide a high-efficiency low-rank coalbed methane extraction device and method to address the problems mentioned in the background section. Summary of the Invention

[0003] To achieve the above objectives, the present invention provides the following technical solution: a high-efficiency low-rank coalbed methane extraction device and method, comprising:

[0004] The outer horizontal pipe is installed in the horizontal section of the L-shaped horizontal well and is fixedly connected to the outer vertical pipe;

[0005] The inner horizontal tube is coaxially arranged inside the outer horizontal tube;

[0006] The inner vertical pipe is installed inside the outer vertical pipe and is fixedly connected to the inner horizontal pipe;

[0007] Multiple fracturing and extraction devices are arranged horizontally, with adjacent fracturing and extraction devices connected to each other, and the end of the fracturing and extraction device near the outer horizontal pipe is fixedly connected to the outer horizontal pipe and the inner horizontal pipe.

[0008] The packing device is installed corresponding to the fracturing and extraction device, and is located at the left end of the fracturing and extraction device;

[0009] The pulverized coal sedimentation device is located at the connection between the inner horizontal pipe and the inner vertical pipe.

[0010] Furthermore, as a preferred embodiment, the lower part of the outer vertical pipe is provided with a sedimentation chamber, the upper part of the sedimentation chamber is provided with a sealing ring surface, the inner ring of the sealing ring surface is in contact with the inner vertical pipe, and is located below the connection between the outer horizontal pipe and the outer vertical pipe.

[0011] Furthermore, preferably, the fracturing extraction device includes:

[0012] The outer pipe body is installed in the horizontal section of the L-shaped horizontal well, and its end is fixedly connected to the outer horizontal pipe.

[0013] The central tube is coaxially arranged with the outer tube body, and its end is fixedly connected to the inner horizontal tube;

[0014] Two sealing rings are symmetrically distributed and fixed at the ends between the outer tube and the central tube, respectively;

[0015] The regulating pipe is movably mounted on the central pipe, with its left end fixedly connected to the sealing device.

[0016] The positioning and sealing component is set between the regulating pipe and the outer pipe body, and its right end is fixedly connected to the sealing ring body.

[0017] Furthermore, as a preferred embodiment, the outer tube body is provided with injection holes corresponding to the positioning and sealing components and connecting square holes corresponding to the sealing devices, and multiple injection holes and connecting square holes are arranged in a ring; the central tube is provided with multiple through holes arranged in a ring, and the adjusting tube is provided with long channels corresponding to the through holes.

[0018] Furthermore, preferably, the positioning and closing component includes:

[0019] The limiting tube body is fixedly connected to the sealing ring body at its right end and slidably connected to the outer wall of the regulating tube at its left end. The limiting tube body is provided with a ring-shaped distribution of through slots.

[0020] The tension spring body is positioned between the limiting tube body and the outer tube body, and is fixedly connected to the sealing ring body;

[0021] A closed tube is slidably disposed between a limiting tube body and an outer tube body, and its right end is fixedly connected to a tension spring body. The inner side of the closed tube is provided with a closed slot corresponding to the through slot.

[0022] The locking block is spring-loaded and positioned in the through-hole on the limiting tube, with its outer side corresponding to the closing hole on the sealing tube. The locking block is composed of a cylinder and a hemisphere, with the hemisphere facing the center.

[0023] Furthermore, preferably, the sealing device includes:

[0024] The compression spring assembly is located on the outer wall of the central tube and is fixedly connected to the left end sealing ring.

[0025] The sealing assembly is configured to correspond to the connecting square hole on the outer tube body;

[0026] Adjust the polyhedron and move it onto the central tube. The outer bevel corresponds to the sealing assembly, and the left end is fixedly connected to the compression spring assembly.

[0027] Drive the toroidal surface to connect the adjusting polyhedron and the adjusting tube.

[0028] Furthermore, preferably, the sealing assembly includes:

[0029] The closed columns are arranged in a ring, and are movably disposed within the connecting square holes. An elastic reset member is connected between the closed columns and the connecting square holes. A limiting channel is provided on the outer side of the closed columns.

[0030] Fixed arc surfaces are arranged in multiple groups in a ring, with two fixed arc surfaces symmetrically distributed in each group. Each group of fixed arc surfaces is fixed on the outer tube between two adjacent closed columns and is slidably connected to the closed columns. The two fixed arc surfaces in the same group are located on both sides of the restricted channel.

[0031] The movable arc surface is moved between the fixed arc surfaces in the same group, and its two ends are connected to the limiting channels in the adjacent closed columns. The four corners where the movable arc surface connects to the limiting channels are made of soft material.

[0032] Furthermore, preferably, the pulverized coal sedimentation device includes:

[0033] The collection mesh is set at an angle at the connection between the inner horizontal pipe and the inner vertical pipe;

[0034] The flexible movable column is movably installed on the inner wall of the inner vertical tube, and its top is fixedly connected to the edge of the collecting net surface;

[0035] The horizontal bar is fixed to the bottom of the inner vertical tube;

[0036] The circular surface is flipped, and the central axis is rotatably connected to the fixed crossbar via a torsion spring.

[0037] A method for using a high-efficiency, low-rank coalbed methane extraction device includes the following steps:

[0038] Step 1: Connect multiple fracturing and extraction devices to each other, install them in the horizontal section, and connect the ends to the inner and outer horizontal pipes, and then connect the outer vertical pipe and the inner vertical pipe in sequence.

[0039] Step 2: Next, high-pressure fracturing fluid is pumped in through the inner vertical pipe. During the fracturing fluid delivery process, the collecting mesh is pushed down, the channel is opened and the fluid flows into the inner horizontal pipe, and the elastic moving column is pushed to fix the flipping circular surface, so that the high-pressure fracturing fluid enters the central pipe.

[0040] Step 3: Then, the high-pressure fracturing fluid enters the space between the outer tube and the regulating tube through the through hole on the central tube. Under the action of the fracturing fluid pressure, it pushes the annular surface to move the regulating polyhedron, compresses the compression spring assembly, and causes the sealing assembly to expand outward, thus sealing the horizontal section in segments. At this time, the regulating tube disengages from the position of the locking block in the restricting tube, and then the locking block moves towards the center, releasing the sealing tube and opening the injection hole.

[0041] Step 4: The high-pressure fracturing fluid then impacts the coal seam through the injection holes, fracturing the horizontal section of the coal seam in stages. After fracturing is completed, the high-pressure fracturing fluid is depressurized and discharged back, thereby resetting the isolation component, which in turn drives the regulating pipe to reset. The sealing pipe remains in the same position, keeping the injection holes open at all times. As the fracturing fluid is discharged, the collection screen is reset.

[0042] Step 5: Finally, coalbed methane is extracted through the central pipe. The coalbed methane enters the central pipe through the injection holes and through holes, then enters the inner vertical pipe through the inner horizontal pipe, and impacts the collection screen from below, intercepting coal dust and causing it to settle onto the rotating circular surface. When the coal dust reaches a certain amount, the rotating circular surface rotates on the fixed crossbar, transporting the coal dust to the sedimentation chamber, and the collection screen is vibrated and dusted regularly.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] In this invention, by cooperating with the locking block of the positioning and sealing component in the fracturing and extraction device, the injection hole is automatically opened during fracturing and remains permanently open after fracturing, achieving the effect of long-term unobstructed extraction channel without additional operation, thus improving extraction continuity.

[0045] By adjusting the linkage between the polyhedron and the inclined plane of the packer in the packer device, the fracturing fluid pressure drives the packer to expand radially, achieving reliable segmented packing, automatic retraction after depressurization, and synchronous action with the opening of the injection hole, thus simplifying the segmented fracturing process.

[0046] By combining the inclined collection screen and the rotating circular surface in the pulverized coal sedimentation device, the pulverized coal is automatically intercepted during extraction and discharged into the sedimentation chamber by gravity at regular intervals, preventing pulverized coal from entering the upper part of the vertical pipe equipment, thus solving the problem of pulverized coal blockage from the source.

[0047] By sealing the sedimentation chamber at the bottom of the external vertical pipe with the sealing ring surface, the coal powder settles at the lowest point of the device and cannot return upwards. Regular centralized cleaning can maintain long-term stable discharge, which greatly extends the pump inspection cycle.

[0048] By connecting multiple fracturing and extraction devices in series, and with the sealing components of each device synchronously expanding radially under the pressure of fracturing fluid to seal their respective sections, and the positioning and sealing components of each device synchronously triggering to lock the injection holes to permanently open, the system achieves the effect of completing segmented sealing and fracturing in one go across the entire horizontal section, eliminating the need for segmented operations, and allowing fracturing and extraction to share the same tubing string, thus significantly improving the overall extraction efficiency of low-rank coalbed methane. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the overall structure of a high-efficiency, low-rank coalbed methane extraction device.

[0050] Figure 2 This is a schematic cross-sectional view of the external vertical pipe and the pulverized coal sedimentation device.

[0051] Figure 3 This is a schematic diagram of a fracturing and extraction device.

[0052] Figure 4 This is a schematic diagram of the cross-sectional structure of a fracturing and extraction device;

[0053] Figure 5 This is a schematic diagram of the sealing device structure;

[0054] Figure 6 This is a schematic diagram of the enclosure component structure;

[0055] Figure 7 This is a schematic diagram of the packer in its packed state.

[0056] Figure 8 This is a schematic diagram of the cross-sectional structure of a fracturing extraction device in a sealed state;

[0057] Figure 9 This is a schematic diagram of the fracturing and extraction device in the extraction state.

[0058] Figure 10 This is a schematic diagram of a pulverized coal sedimentation device.

[0059] In the diagram: 1. Outer horizontal pipe; 2. Outer vertical pipe; 3. Inner horizontal pipe; 4. Inner vertical pipe; 5. Fracturing extraction device; 6. Separator; 7. Pulverized coal sedimentation device; 21. Separator annular surface; 22. Sedimentation chamber; 51. Outer pipe body; 52. Central pipe; 53. Separating annular body; 54. Adjusting pipe; 55. Positioning and sealing assembly; 61. Compression spring assembly; 62. Separator assembly; 63. Adjusting polyhedron; 64. Pushing annular surface; 71. Collection mesh surface; 72. Elastic moving column; 73. Fixed crossbar; 74. Flipping circular surface; 511. Injection hole; 512. Connecting square hole; 521. Through hole; 541. Long channel; 551. Restricting pipe body; 552. Tension spring body; 553. Sealing pipe; 554. Locking block; 621. Sealing column; 622. Fixed arc surface; 623. Moving arc surface. Detailed Implementation

[0060] Please see Figures 1-10 In this embodiment of the invention, a high-efficiency low-rank coalbed methane extraction device and method includes:

[0061] The outer horizontal pipe 1 is installed in the horizontal section of the L-shaped horizontal well and is fixedly connected to the outer vertical pipe 2;

[0062] The inner horizontal tube 3 is coaxially arranged inside the outer horizontal tube 1;

[0063] The inner vertical pipe 4 is installed inside the outer vertical pipe 2 and is fixedly connected to the inner horizontal pipe 3;

[0064] Multiple fracturing and extraction devices 5 are arranged horizontally. Two adjacent fracturing and extraction devices 5 are connected to each other, and the end of the fracturing and extraction device 5 adjacent to the outer horizontal pipe 1 is fixedly connected to the outer horizontal pipe 1 and the inner horizontal pipe 3.

[0065] The packing device 6 is set corresponding to the fracturing and extraction device 5 and is located at the left end of the fracturing and extraction device 5.

[0066] The pulverized coal sedimentation device 7 is located at the connection between the inner horizontal pipe 3 and the inner vertical pipe 4.

[0067] In this embodiment, the lower part of the outer vertical pipe 2 is provided with a sedimentation chamber 22, and the upper part of the sedimentation chamber 22 is provided with a sealing ring surface 21. The inner ring of the sealing ring surface 21 is in contact with the inner vertical pipe 4 and is located below the connection between the outer horizontal pipe 1 and the outer vertical pipe 2.

[0068] In other words, an annulus is formed between the outer horizontal pipe 1 and the well wall. The inner horizontal pipe 3 serves as the main channel for fracturing fluid and coalbed methane. Multiple fracturing extraction devices 5 are arranged in series in the horizontal section, with each device corresponding to a fracturing section. The sealing device 6 is located at the left end of each fracturing extraction device 5 and is used to seal the annulus between adjacent sections during fracturing. The coal powder sedimentation device 7 is located at the corner connection between the vertical section and the horizontal section and is specifically used to intercept coal powder during the extraction stage. A sedimentation chamber 22 is provided at the lower part of the outer vertical pipe 2. The sedimentation chamber 22 is located at the lowest point of the entire device. The sealing annulus 21 seals the annulus between the inner vertical pipe 4 and the outer vertical pipe 2, so that the coal powder returning from the horizontal section cannot enter the upper part of the outer vertical pipe 2 and can only settle at the bottom of the sedimentation chamber 22.

[0069] In this embodiment, the fracturing and extraction device 5 includes:

[0070] The outer pipe body 51 is installed in the horizontal section of the L-shaped horizontal well, and its end is fixedly connected to the outer horizontal pipe 1.

[0071] The central tube 52 is coaxially arranged with the outer tube body 51, and its end is fixedly connected to the inner horizontal tube 3;

[0072] Two sealing rings 53 are symmetrically distributed and fixed at the ends between the outer tube 51 and the central tube 52, respectively.

[0073] The regulating pipe 54 is movably mounted on the central pipe 52, and its left end is fixedly connected to the sealing device 6.

[0074] The positioning and sealing component 55 is set between the regulating pipe 54 and the outer pipe body 51, and its right end is fixedly connected to the sealing ring body 53.

[0075] In this embodiment, the outer tube 51 is provided with a spray hole 511 corresponding to the positioning and sealing component 55 and a connecting square hole 512 corresponding to the sealing device 6. The spray hole 511 and the connecting square hole 512 are arranged in a ring. The central tube 52 is provided with a ring of through holes 521 and the regulating tube 54 is provided with a long channel 541 corresponding to the through holes 521.

[0076] In other words, an annular space is formed between the outer tube 51 and the central tube 52. The sealing ring 53 closes both ends, and the regulating tube 54 can slide along the axial direction of the central tube 52. Its left end drives the sealing device 6, and the positioning and sealing component 55 is responsible for locking the opening and closing state of the injection hole 511 after fracturing, realizing the function of "opening during fracturing and permanently keeping it open after fracturing". This avoids the need for additional operations during the extraction stage. In the initial state, the long channel 541 of the regulating tube 54 is connected to the through hole 521 of the central tube 52, allowing the fluid flow to enter the regulating tube 54 through the central tube 52. Between the outer pipe bodies 51, as the fracturing fluid is transported and the pressure increases, the sealing device 6 is moved to separate the fracturing sections. At the same time, the regulating pipe 54 is moved. After the regulating pipe 54 moves, the long channel 541 is always connected to the through hole 521. The fracturing fluid continuously enters the space between the outer pipe body 51 and the regulating pipe 54 from the central pipe 52 through the through hole 521 and the long channel 541. At the same time, the regulating pipe 54 releases the positioning and sealing component 55, opening the injection hole 511. Then, the fracturing fluid is sprayed out through the injection hole 511 to perform fracturing work on the coal seam in each fracturing section.

[0077] In a preferred embodiment, the multiple injection holes 511 distributed in an annular pattern ensure that the fracturing fluid is injected uniformly in the circumferential direction to form symmetrical fractures; the position design of the long channel 541 and the through hole 521 enables the fracturing fluid channel to be normally open, maintaining the continuous delivery of fracturing fluid; the connecting square hole 512 is square to prevent the packer device 6 from rotating and to ensure the stability of the packer action.

[0078] In this embodiment, the positioning and sealing component 55 includes:

[0079] The limiting tube 551 is fixedly connected to the sealing ring 53 at its right end and slidably connected to the outer wall of the adjusting tube 54 at its left end. The limiting tube 551 is provided with a ring-shaped distribution of through slots.

[0080] The tension spring body 552 is disposed between the limiting tube body 551 and the outer tube body 51, and is fixedly connected to the sealing ring body 53;

[0081] The closed tube 553 is slidably disposed between the limiting tube body 551 and the outer tube body 51, and its right end is fixedly connected to the tension spring body 552. The inner side of the closed tube 553 is provided with a closed slot corresponding to the through slot.

[0082] The locking block 554 is spring-moving and set in the through slot on the limiting tube 551, with its outer side corresponding to the closing slot on the sealing tube 553. The locking block 554 is composed of a cylinder and a hemisphere, with the hemisphere facing the center.

[0083] In other words, before fracturing, the outer wall of the right end of the regulating pipe 54 presses against the hemisphere of the locking block 554, causing the locking block 554 to move outward. The cylindrical part of the locking block 554 engages with the sealing slot of the sealing pipe 553, thus fixing the sealing pipe 553 in the left-side position. At this time, the sealing pipe 553 covers the injection hole 511. During fracturing, the packer device 6 drives the regulating pipe 54 to move to the left, and its right end leaves the hemisphere of the locking block 554. Under the action of the internal spring, the locking block 554 retracts towards the center and exits from the sealing pipe 553. The sealing tube 553 disengages from the locking slot and moves to the right under the tension of the tension spring 552, exposing the injection hole 511, allowing fracturing fluid to be ejected. The left end of the sealing tube 553 moves to the right side of the locking block 554. After fracturing, the regulating tube 54 resets to the right, but at this time the sealing tube 553 has already moved to the right. The locking block 554 is pushed outward by the regulating tube 54, causing the regulating tube 54 to reset, but this does not affect the sealing tube 553. The sealing tube 553 remains in the rightward position, and the injection hole 511 is permanently opened for subsequent extraction.

[0084] As a preferred embodiment, the positioning and sealing component 55 adopts a purely mechanical triggering mechanism of "block + spring + tension spring", which does not require electromagnetic or hydraulic control. The state locking can be completed in one action. The hemispherical design of the block 554 makes the resistance small when the regulating tube 54 is pushed. After retraction, it is pushed back by the regulating tube 54. After the reset, the position of the sealing tube 553 is restricted, realizing the function of "irreversible after fracturing is opened", ensuring that the injection hole 511 is always unobstructed during the extraction stage.

[0085] In this embodiment, the sealing device 6 includes:

[0086] Compression spring assembly 61 is disposed on the outer wall of central tube 52 and is fixedly connected to left end sealing ring 53;

[0087] The sealing component 62 is configured to correspond to the connecting square hole 512 on the outer tube 51;

[0088] Adjust the polyhedron 63 and move it on the central tube 52. The outer inclined surface corresponds to the sealing component 62, and the left end is fixedly connected to the compression spring assembly 61.

[0089] Drive the toroidal surface 64 to connect the adjusting polyhedron 63 and the adjusting tube 54.

[0090] In other words, in the initial state, the compression spring assembly 61 is at its free length, the adjusting polyhedron 63 is located on the far right, its inclined surface does not compress the packer assembly 62, and the packer assembly 62 retracts into the outer tube 51 and does not contact the well wall; during fracturing, high-pressure fracturing fluid enters the annular space through the through hole 521. Under pressure, it pushes the annular surface 64 to move to the left, causing the adjusting polyhedron 63 to compress the compression spring assembly 61. The inclined surface of the adjusting polyhedron 63 pushes the packer assembly 62 to expand radially outward, tightly pressing against the well wall to achieve annular sealing; when the pressure is released after fracturing, the compression spring assembly 61 pushes the adjusting polyhedron 63 to reset to the right, and the packer assembly 62 retracts back to its original position.

[0091] In a preferred embodiment, the inclined surface of the adjusting polyhedron 63 cooperates with the sealing assembly 62 to efficiently convert axial movement into radial expansion, resulting in a large force ratio and high sealing pressure; the compression spring assembly 61 provides reliable reset force to avoid jamming; the pushing annular surface 64 links the adjusting tube 54 with the adjusting polyhedron 63, so that the expansion of the sealing assembly 62 and the opening of the injection hole 511 are synchronized.

[0092] In this embodiment, the sealing component 62 includes:

[0093] The sealing post 621 is provided in a ring, and is movably disposed within the connecting square hole 512. An elastic reset member is connected between the sealing post 621 and the connecting square hole 512. A limiting channel is provided on the outer side of the sealing post 621.

[0094] Fixed arc surfaces 622 are arranged in multiple groups in a ring, with two symmetrically distributed in each group. Each group of fixed arc surfaces 622 is fixed on the outer tube 51 between two adjacent closed columns 621 and is slidably connected to the closed columns 621. The two fixed arc surfaces 622 in the same group are located on both sides of the restricted channel.

[0095] The movable arc surface 623 is movably positioned between the fixed arc surfaces 622 in the same group, and its two ends are connected to the limiting channels in the adjacent closed columns 621. The four corners of the movable arc surface 623 connected to the limiting channels are made of soft material.

[0096] In other words, when the inclined surface of the adjusting polyhedron 63 pushes the sealing column 621 to move radially outward, the fixed arc surface 622 remains fixed on the outer tube 51, and its position does not change. Consequently, the distance between adjacent sealing columns 621 increases, and the moving arc surface 623 moves outward with the sealing column 621. Under the guidance of the limiting channel, the moving arc surface 623 also slides outward. However, because its four corners are made of soft material, it can adapt to deformation and always maintains a continuous annular sealing surface with the fixed arc surface 622, which fits tightly against the well wall, ensuring sealing and avoiding hard interference. The cooperation between the fixed arc surface 622 and the moving arc surface 623 achieves circumferential full coverage without leakage gaps. Conversely, when the adjusting polyhedron 63 is reset under the push of the compression spring group 61, the sealing column 621 moves towards the center to reset due to the action of the elastic reset member between the sealing column 621 and the connecting square hole 512. This causes the moving arc surface 623 to move towards the center to reset, and the moving arc surface 623 retracts into the limiting channel and the fixed arc surface 622.

[0097] In this embodiment, the pulverized coal sedimentation device 7 includes:

[0098] The collecting mesh 71 is inclinedly set at the connection between the inner horizontal pipe 3 and the inner vertical pipe 4;

[0099] The elastic movable column 72 is movably set on the inner wall of the inner vertical tube 4, and its top is fixedly connected to the edge of the collecting net surface 71;

[0100] The fixed crossbar 73 is fixed to the bottom of the inner vertical tube 4;

[0101] The circular surface 74 is flipped, and the central axis is rotatably connected to the fixed crossbar 73 via a torsion spring.

[0102] In other words, during the fracturing fluid injection stage, high-pressure fracturing fluid flows downward from the inner vertical pipe 4, impacting the collection mesh 71. Due to the inclined setting of the collection mesh 71, the fluid pressure pushes it downward, compressing the elastic moving column 72. The collection mesh 71 opens a larger channel, and at the same time, the lower end of the elastic moving column 72 abuts against the flipping circular surface 74, keeping it in a horizontal closed state to prevent fracturing fluid from leaking into the sedimentation chamber 22 from the flipping circular surface 74. During the extraction stage, coalbed methane carrying coal powder flows from the horizontal section through the inner horizontal pipe. 3. The gas enters the inner vertical pipe 4 and flows upward. The gas impacts the collecting screen 71 from bottom to top. Due to inertia, the coal powder is intercepted by the screen and slides down the inclined surface onto the flipping circular surface 74. When the weight of the coal powder accumulated on the flipping circular surface 74 exceeds the preload of the torsion spring, the flipping circular surface 74 flips downward around the fixed crossbar 73, pouring the coal powder into the sedimentation chamber 22. After pouring, the torsion spring resets it. The collecting screen 71 is also periodically vibrated by ground pulse airflow or mechanical knocking to shake off the attached fine powder and keep the screen transparent.

[0103] In this embodiment, a method for using a high-efficiency, low-rank coalbed methane extraction device is characterized by the following steps:

[0104] Step 1: Connect multiple fracturing and extraction devices 5 in series and install them into the horizontal section of the L-shaped horizontal well. Fix the end of the fracturing and extraction device 5 closest to the outer horizontal pipe 1 to the outer horizontal pipe 1 and the inner horizontal pipe 3. Connect the outer vertical pipe 2 and the inner vertical pipe 4 in sequence, so that the outer vertical pipe 2 is connected to the fixed outer horizontal pipe 1, and the inner vertical pipe 4 is fixedly connected to the inner horizontal pipe 3. At this time, the entire string is lowered into place, and an annulus is formed between the outer horizontal pipe 1 and the well wall. The inner horizontal pipe 3 serves as the main channel for fracturing fluid and coalbed methane. Each fracturing and extraction device 5 corresponds to a fracturing section. The sealing device 6 is located at the left end of each fracturing and extraction device 5. The coal powder sedimentation device 7 is located at the corner connection between the vertical section and the horizontal section. The sedimentation chamber 22 is located at the lowest point of the lower part of the outer vertical pipe 2. The sealing annulus 21 seals the annulus between the inner vertical pipe 4 and the outer vertical pipe 2.

[0105] Step 2: High-pressure fracturing fluid is pumped into the well through the inner vertical pipe 4. The fracturing fluid flows downward from the inner vertical pipe 4 and impacts the collection mesh 71 located at the connection between the inner horizontal pipe 3 and the inner vertical pipe 4. Due to the inclined setting of the collection mesh 71, the fluid pressure pushes the collection mesh 71 downward, compressing the elastic moving column 72. The collection mesh 71 opens a larger channel, allowing the fracturing fluid to smoothly enter the inner horizontal pipe 3. At the same time, the lower end of the elastic moving column 72 presses against the flipping circular surface 74, so that the flipping circular surface 74 overcomes the preload of the torsion spring and remains in a horizontal closed state, thereby preventing the high-pressure fracturing fluid from leaking into the sedimentation chamber 22 from the flipping circular surface 74 and causing energy loss. The fracturing fluid then enters the central pipe 52 of each fracturing and extraction device 5 through the inner horizontal pipe 3.

[0106] Step 3: After the high-pressure fracturing fluid enters the central tube 52, it passes through the annular through-hole 521 on the central tube 52 and the long channel 541 that is always connected to the regulating tube 54, and enters the annular space between the outer tube 51 and the regulating tube 54. As the fracturing fluid pressure continues to increase, the fracturing fluid acts on the pushing annular surface 64, generating a leftward thrust. The pushing annular surface 64 drives the regulating polyhedron 63 and the regulating tube 54 to move to the left together. The regulating polyhedron 63 compresses the compression spring assembly 61 to the left, and at the same time, its outer inclined surface gradually squeezes the sealing column 621 in the sealing assembly 62. Under the push of the inclined surface, the sealing column 621 expands radially outward along the connecting square hole 512, and the movement connected to the sealing column 621... As the moving arc surface 623 moves outward, the fixed arc surface 622 and the moving arc surface 623 together form a continuous annular sealing surface, which tightly presses against the well wall and achieves reliable sealing of the annulus of the fracturing section. The sealing components 62 of multiple fracturing and extraction devices 5 operate simultaneously, dividing the horizontal section into multiple independent fracturing sections. At the same time, the state in which the outer wall of the right end of the regulating pipe 54 was originally pressed against the hemisphere of the locking block 554 is released. The locking block 554 retracts towards the center under the action of its own spring, and its cylindrical part is dislodged from the sealing slot of the sealing pipe 553. Under the tension of the tension spring body 552, the sealing pipe 553 moves rapidly to the right, completely exposing the injection hole 511 on the outer pipe body 51.

[0107] Step 4: High-pressure fracturing fluid then impacts the coal seam through injection hole 511, forcefully fracturing the horizontal section of the coal seam. After fracturing, the high-pressure fracturing fluid is depressurized and returned to its original position. As the pressure decreases, the compression spring assembly 61 pushes the adjusting polyhedron 63 to reset to the right. The inclined surface of the adjusting polyhedron 63 moves away from the sealing column 621. Under the action of the elastic reset element within the connecting square hole 512, the sealing column 621 retracts radially inward. The moving arc surface 623 then retracts to the space between the fixed arc surface 622 and the limiting channel. When the packer assembly 62 is fully reset, the packer assembly releases the annulus. The regulating pipe 54 resets to the right along with the regulating polyhedron 63. When the regulating pipe 54 is reset, the outer wall of its right end pushes the locking block 554 outward, and the sealing pipe 553 remains in the rightward position. The injection hole 511 remains open. As the fracturing fluid continues to be discharged, the pressure in the inner horizontal pipe 3 and the inner vertical pipe 4 gradually decreases. The collecting mesh surface 71 moves upward under the reset force of the elastic moving column 72 and returns to the initial tilt position.

[0108] Step 5: Coalbed methane is extracted through the central pipe 52. The surface extraction equipment generates negative pressure, allowing the coalbed methane, carrying a small amount of water and coal dust, to enter the wellbore annulus through formation fractures. It then enters the space between the outer pipe 51 and the central pipe 52 through the permanently opened injection holes 511 on each fracturing extraction device 5, and then enters the central pipe 52 through the through-hole 521. The gas flows along the central pipe 52, the inner horizontal pipe 3, and towards the inner vertical pipe 4. When the coalbed methane carrying coal dust enters the inner vertical pipe 4 from bottom to top, it first impacts the inclined collection mesh 71. The coal dust is intercepted due to inertia after impacting the mesh and slides down the inclined collection mesh 71 onto the lower rotating circular surface 74. The gas then passes through the collection mesh 71 and continues... The coal is drawn upwards to the ground. As the extraction continues, the coal dust accumulated on the rotating circular surface 74 gradually increases. When the weight of the coal dust exceeds the preload torque of the torsion spring, the rotating circular surface 74 rotates downwards around the fixed crossbar 73, pouring the coal dust into the sedimentation chamber 22 at the bottom of the outer vertical pipe 2. After pouring, the rotating circular surface 74 automatically resets under the action of the torsion spring and re-closes, waiting for the next coal dust discharge. The sedimentation chamber 22 can be cleaned periodically through sand removal operations. In addition, in order to maintain the permeability of the collecting screen 71, a low-frequency pulse wave can be generated periodically by a ground pulse airflow generator to make the collecting screen 71 vibrate slightly, shaking off the fine coal dust attached to the screen, ensuring that the screen does not become clogged during long-term extraction.

[0109] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-efficiency, low-rank coalbed methane extraction device, characterized in that: include: The outer horizontal pipe (1) is set in the horizontal section of the L-shaped horizontal well and is fixedly connected to the outer vertical pipe (2); The inner horizontal tube (3) is coaxially arranged inside the outer horizontal tube (1); The inner vertical pipe (4) is set inside the outer vertical pipe (2) and is fixedly connected to the inner horizontal pipe (3); Multiple fracturing extraction devices (5) are arranged horizontally. Two adjacent fracturing extraction devices (5) are connected to each other, and the end of the fracturing extraction device (5) adjacent to the outer horizontal pipe (1) is fixedly connected to the outer horizontal pipe (1) and the inner horizontal pipe (3). The sealing device (6) is set in correspondence with the fracturing extraction device (5) and is set at the left end of the fracturing extraction device (5); The coal powder sedimentation device (7) is located at the connection between the inner horizontal pipe (3) and the inner vertical pipe (4).

2. The high-efficiency low-rank coalbed methane extraction device according to claim 1, characterized in that: The lower part of the outer vertical pipe (2) is provided with a sedimentation chamber (22), and the upper part of the sedimentation chamber (22) is provided with a sealing ring surface (21). The inner ring of the sealing ring surface (21) is in contact with the inner vertical pipe (4) and is located below the connection between the outer horizontal pipe (1) and the outer vertical pipe (2).

3. The high-efficiency low-rank coalbed methane extraction device according to claim 1, characterized in that: The fracturing and extraction device (5) includes: The outer pipe body (51) is set in the horizontal section of the L-shaped horizontal well, and its end is fixedly connected to the outer horizontal pipe (1); The central tube (52) is coaxially arranged with the outer tube body (51), and its end is fixedly connected to the inner horizontal tube (3); Two sealing rings (53) are symmetrically distributed and fixed at the ends between the outer tube (51) and the central tube (52); The regulating pipe (54) is movably mounted on the central pipe (52), and its left end is fixedly connected to the sealing device (6); The positioning and sealing component (55) is set between the regulating pipe (54) and the outer pipe body (51), and its right end is fixedly connected to the sealing ring body (53).

4. The high-efficiency low-rank coalbed methane extraction device according to claim 3, characterized in that: The outer tube (51) is provided with a spray hole (511) corresponding to the positioning and sealing component (55) and a connecting square hole (512) corresponding to the sealing device (6). The spray hole (511) and the connecting square hole (512) are arranged in a ring. The central tube (52) is provided with a ring of through holes (521) and the regulating tube (54) is provided with a long channel (541) corresponding to the through holes (521).

5. A high-efficiency low-rank coalbed methane extraction device according to claim 4, characterized in that: The positioning and closing component (55) includes: The limiting tube (551) is fixedly connected to the sealing ring (53) at its right end and slidably connected to the outer wall of the adjusting tube (54) at its left end. The limiting tube (551) is provided with a ring-shaped through slot. The tension spring body (552) is disposed between the limiting tube body (551) and the outer tube body (51) and is fixedly connected to the sealing ring body (53); The closed tube (553) is slidably disposed between the limiting tube body (551) and the outer tube body (51), and its right end is fixedly connected to the tension spring body (552). The inner side of the closed tube (553) is provided with a closed slot corresponding to the through slot. The locking block (554) is moved by a spring and is set in the through slot on the limiting tube (551). Its outer side corresponds to the closing slot on the sealing tube (553). The locking block (554) is composed of a cylinder and a hemisphere, with the hemisphere facing the center.

6. The high-efficiency low-rank coalbed methane extraction device according to claim 4, characterized in that: The sealing device (6) includes: Compression spring assembly (61) is set on the outer wall of the central tube (52) and is fixedly connected to the left end sealing ring (53); The sealing assembly (62) is provided corresponding to the connecting square hole (512) on the outer tube body (51); Adjust the polyhedron (63), move it on the central tube (52), the outer slope corresponds to the sealing assembly (62), and the left end is fixedly connected to the compression spring assembly (61); Push the toroidal surface (64) to connect the adjusting polyhedron (63) and the adjusting tube (54).

7. A high-efficiency low-rank coalbed methane extraction device according to claim 6, characterized in that: The sealing assembly (62) includes: The closed column (621) is provided in a ring, and is movably disposed in the connecting square hole (512). An elastic reset member is connected between the closed column (621) and the connecting square hole (512). A limiting channel is provided on the outside of the closed column (621). Fixed arc surfaces (622) are arranged in multiple groups in a ring, with two fixed arc surfaces (622) arranged symmetrically in each group. Each fixed arc surface (622) is fixed on the outer tube (51) between two adjacent closed columns (621) and is slidably connected to the closed column (621). The two fixed arc surfaces (622) in the same group are located on both sides of the restricted channel. The movable arc surface (623) is movably positioned between the fixed arc surfaces (622) in the same group, and its two ends are connected to the limiting channels in the adjacent closed columns (621). The four corners of the movable arc surface (623) connected to the limiting channels are made of soft material.

8. A high-efficiency low-rank coalbed methane extraction device according to claim 2, characterized in that: The pulverized coal sedimentation device (7) includes: The collecting mesh (71) is inclinedly set at the connection between the inner horizontal pipe (3) and the inner vertical pipe (4); The elastic movable column (72) is movably set on the inner wall of the inner vertical tube (4), and its top is fixedly connected to the edge of the collecting net surface (71); A fixed crossbar (73) is fixed to the bottom of the inner vertical tube (4); The rotating circular surface (74) is rotated and connected to the fixed crossbar (73) via a torsion spring.

9. A method for high-efficiency low-rank coalbed methane extraction, comprising using a high-efficiency low-rank coalbed methane extraction apparatus as described in any one of claims 1-8, characterized in that, It includes the following steps: Step 1: Connect multiple fracturing extraction devices (5) to each other, install them in the horizontal section, and connect the ends to the inner horizontal pipe (3) and the outer horizontal pipe (1), and connect the outer vertical pipe (2) and the inner vertical pipe (4) in sequence. Step 2: Then, high-pressure fracturing fluid is pumped in through the inner vertical pipe (4). During the fracturing fluid delivery process, the collecting mesh (71) is pushed down, the channel is opened and the fluid flows into the inner horizontal pipe (3), and the elastic moving column (72) is pushed to fix the flipping circular surface (74), and then the high-pressure fracturing fluid enters the central pipe (52). Step 3: Then, the high-pressure fracturing fluid enters between the outer tube body (51) and the regulating tube (54) through the through hole (521) on the central tube (52). Under the action of the fracturing fluid pressure, the annular surface (64) pushes the regulating polyhedron (63) to move, compressing the compression spring assembly (61) and causing the sealing assembly (62) to expand outward, thus sealing the horizontal section in segments. At this time, the regulating tube (54) disengages from the position of the locking block (554) in the restricting tube body (551), and then the locking block (554) moves towards the center, releasing the sealing tube (553) and opening the injection hole (511). Step 4: The high-pressure fracturing fluid then impacts the coal seam through the injection hole (511) to perform segmented fracturing on the horizontal section of the coal seam. After fracturing is completed, the high-pressure fracturing fluid is depressurized and discharged back, and the sealing component (62) is reset, which drives the regulating pipe (54) to reset. The sealing pipe (553) remains in the same position, so that the injection hole (511) is always open. As the fracturing fluid is discharged, the collecting screen (71) is reset. Step 5: Finally, coalbed methane is extracted through the central pipe (52). The coalbed methane enters the central pipe (52) through the injection hole (511) and the through hole (521), and then enters the inner vertical pipe (4) through the inner horizontal pipe (3). It impacts the collection screen (71) from below, intercepting coal powder and causing it to settle on the flipping circular surface (74). When the coal powder reaches a certain amount, the flipping circular surface (74) flips on the fixed crossbar (73) to transport the coal powder to the sedimentation chamber (22). The collection screen (71) is vibrated and dusted regularly.

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