Coal seam multi-section downward gas extraction drill hole acid fracturing device

Abstract

The utility model relates to a coal seam multi-section downward gas extraction drilling acid fracturing device, and relates to the technical field of coal seam gas extraction, the coal seam multi-section downward gas extraction drilling acid fracturing device comprises first conveying pipelines used for conveying acid liquid and second conveying pipelines used for conveying water, the end of each first conveying pipeline is provided with a first connector so that every two adjacent first conveying pipelines can be connected, and the end of each second conveying pipeline is provided with a second connector; a supporting assembly is arranged at the connecting position of every two adjacent first conveying pipelines, second connectors are arranged at the ends of the second conveying pipelines so that every two adjacent second conveying pipelines can be connected, the second conveying pipelines are sleeved with a plurality of compression-resistant bags, the compression-resistant bags are sleeved with the first conveying pipelines, and the first conveying pipelines are connected with the first connectors. The first conveying pipeline is provided with a communicating hole used for injecting acid liquid into or discharging acid liquid out of the drill hole. The method has the effects that the acid liquid is injected into different layers according to needs, minerals are dissolved, fractures are expanded, the coal seam permeability is improved, ground stress and fluid impact are effectively resisted, and pipeline dislocation, disjunction and leakage are prevented.

Description

Technical Field

[0001] This application relates to the technical field of coal seam gas extraction, and in particular to an acid fracturing device for multi-stage downward coal seam gas extraction boreholes. Background Technology

[0002] In the field of coal seam gas extraction, although there are a large number of fractures in the coal seam, they are basically filled with carbonate minerals such as calcite and dolomite, which makes coal seam gas extraction difficult. Injecting acid into the borehole for acid fracturing can dissolve the carbonate minerals contained in the coal, thereby opening up the fracture network in the coal and reducing the difficulty of coal seam gas extraction.

[0003] Currently, due to the long length of coal seam gas drainage boreholes, conventional single-stage acid fracturing technology suffers from uneven distribution of in-situ stress, causing acid to flow more easily to high-permeability sections and less to low-permeability sections with severe fracture network filling. This results in insufficient acidification of the target formation and limited improvement in gas drainage efficiency. In addition, during long downward drilling, the transmission pipelines are only connected by interfaces. The complex environment inside the borehole (such as in-situ stress and fluid impact) can cause misalignment or disconnection between the transmission pipelines, which can easily lead to leakage and make it difficult to ensure the continuity of acid injection and sealing processes. Utility Model Content

[0004] To address the issue of insufficient acidizing of target formations due to the long length of coal seam gas drainage boreholes and the tendency for leakage to occur in the complex environment within the borehole during long downward drilling, this application provides an acidizing fracturing device for multi-stage downward coal seam gas drainage boreholes.

[0005] This application provides an acid fracturing device for multi-stage downward gas drainage boreholes in coal seams, which adopts the following technical solution:

[0006] A coal seam multi-stage downward gas extraction borehole acid fracturing device includes a first transmission pipe for conveying acidic liquid and a second transmission pipe for conveying water. The end of the first transmission pipe is provided with a first interface to connect two adjacent first transmission pipes. A support component is installed at the connection between two adjacent first transmission pipes. The end of the second transmission pipe is provided with a second interface to connect two adjacent second transmission pipes. A plurality of pressure-resistant bags are fitted on the second transmission pipe. The first transmission pipe is fitted on the pressure-resistant bags. The first transmission pipe is provided with a connecting hole for injecting or discharging acidic liquid into the borehole.

[0007] By adopting the above technical solution, the dual-pipe setup of the first and second transmission pipelines achieves functional separation of acidic liquid transportation and clean water transportation, facilitating staged acid fracturing and cleaning operations. The first and second interfaces facilitate rapid connection between adjacent pipelines, ensuring transmission continuity. The support components enhance the stability of the connection point of the first transmission pipeline, preventing misalignment or disconnection in complex drilling environments. Pressure-resistant bags are fitted onto the second transmission pipeline, using water pressure to assist in sealing the bags, enhancing layered acid fracturing, and resisting in-hole stress and fluid impact, protecting the second transmission pipeline while providing buffer support for the first transmission pipeline. The first transmission pipeline is equipped with connecting holes, allowing for multi-stage layered acid fracturing by controlling the opening position of the connecting holes. This enables precise application of acid to coal seams with different permeabilities, solving the problem of uneven acid distribution in conventional technologies.

[0008] Optionally, the support assembly includes a first ring and a second ring, with a plurality of bolts connected to the first ring and nuts connected to the bolts, and the first transmission pipe is located between the first ring and the second ring to lock the first transmission pipe.

[0009] By adopting the above technical solution, the first ring sleeve and the second ring sleeve clamp the first transmission pipe from both sides. The first transmission pipe is firmly fixed between the two by the tightening action of bolts and nuts, thereby providing a reliable mechanical locking force, effectively resisting the complex stress and fluid impact in the borehole, preventing the connection of the first transmission pipe from loosening and leaking, ensuring the stability and sealing of acid liquid transmission, and providing a guarantee for the safe conduct of acid fracturing operations.

[0010] Optionally, the first ring and the second ring are provided with support rods, and the support rods are equipped with lifting members, which are arranged in an arc shape.

[0011] By adopting the above technical solution, the curved surface of the arc-shaped support member fits against the outer wall of the first transmission pipe, providing a stable support force for the first transmission pipe; the support rod connects the support member and the ring, transferring the weight of the pipe and external pressure to the ring structure, effectively dispersing the force on the first transmission pipe and preventing the pipe from bending and deforming due to its own weight or external pressure.

[0012] Optionally, one end of the first transmission pipe located outside the borehole is connected to a first storage tank for storing acidic liquid, and a first pump, a first flow meter, and a first pressure sensor are provided between the first transmission pipe and the first storage tank.

[0013] By adopting the above technical solution, the first storage tank stores a sufficient amount of acidic liquid for acid fracturing operations; the first pump, as a power source, draws the acidic liquid from the storage tank and transports it to the first transmission pipeline; the first flow meter monitors the flow rate of the acidic liquid in real time, allowing operators to adjust the transport speed according to the coal seam characteristics and fracturing requirements; the first pressure sensor continuously monitors the pressure inside the pipeline and promptly alarms when the pressure is abnormal, preventing pipeline rupture or leakage due to excessive pressure, while also preventing excessively low pressure from affecting the acidification effect, thus achieving precise control of the acidic liquid transport process.

[0014] Optionally, a variable diameter interface is provided at one end of the first transmission pipe located outside the borehole, and the variable diameter interface is connected to the first pump.

[0015] By adopting the above technical solution, the variable diameter interface can be adapted according to the difference between the input pipe diameter of the first pump and the pipe diameter of the first transmission pipeline, optimizing the fluid transmission path and reducing fluid resistance and energy loss caused by sudden changes in pipe diameter. At the same time, it facilitates quick connection and disassembly between the first pump and the first transmission pipeline, making it convenient for equipment installation, commissioning and maintenance, and ensuring that acidic liquid can be efficiently and stably transmitted from the pump body to the pipeline system.

[0016] Optionally, one end of the second transmission pipe located outside the borehole is connected to a second storage tank for storing water, and a second pump, a second flow meter, and a second pressure sensor are provided between the second transmission pipe and the second storage tank.

[0017] By adopting the above technical solution, the second storage tank stores clean water for cleaning boreholes and neutralizing acidic liquids; the second pump pumps the clean water from the storage tank to the second transmission pipeline; the second flow meter and the second pressure sensor monitor and control the flow rate and pressure of the clean water in real time, respectively. After acid fracturing is completed, by precisely controlling the water delivery parameters, residual acid in the borehole can be effectively flushed out, preventing acid from corroding the pipeline and contaminating the coal seam, while creating favorable conditions for subsequent gas extraction.

[0018] Optionally, the pressure-resistant bag is provided with a first connector to connect the pressure-resistant bag to the first transmission pipe, and the pressure-resistant bag is provided with a second connector to connect the pressure-resistant bag to the second transmission pipe.

[0019] By adopting the above technical solution, the first connector and the second connector respectively realize the reliable connection between the pressure-resistant bag and the first transmission pipeline and the second transmission pipeline, ensuring that the pressure-resistant bag will not fall off or shift in the complex environment inside the borehole, and continuously provide protection for the pipeline; at the same time, it facilitates the installation and disassembly of the pressure-resistant bag, and can be quickly replaced when the bag is damaged or aged, ensuring the long-term stable operation of the acid fracturing unit.

[0020] Optionally, both the input and output ends of the first transmission pipe are tapered.

[0021] By adopting the above technical solution, the conical input and output ends can guide the pipes to accurately connect when connecting adjacent pipes or equipment, reducing installation difficulty and improving connection efficiency. The conical structure can effectively reduce the resistance of fluid at the pipe port, making the acid liquid enter and exit the pipe more smoothly, and improving the efficiency and stability of liquid transmission in acid fracturing operations.

[0022] In summary, this application includes at least one of the following beneficial technical effects:

[0023] 1. This device delivers acid and water in stages through dual pipelines. Combined with the stable connection of the support components and the segmented sealing of the pressure-resistant bags, it enables layered acid fracturing and cleaning of multi-segment downward boreholes in coal seams. The connecting holes and pressure-resistant bags work together to allow acid to be injected into different layers as needed, dissolving minerals and expanding fractures, increasing coal seam permeability and enhancing gas extraction efficiency.

[0024] 2. The supporting components, pressure-resistant bags, and arc-shaped support components enhance the stability and sealing of the first transmission pipeline within the borehole, effectively resisting ground stress and fluid impact, preventing pipeline misalignment, disconnection, and leakage, and ensuring the safe and continuous operation of acid fracturing. Attached Figure Description

[0025] Figure 1 This is a structural schematic diagram of an embodiment of this application;

[0026] Figure 2 This is a top view of the supporting components in an embodiment of this application;

[0027] Figure 3 This is a schematic diagram of the actual application of the embodiments of this application.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. First transmission pipe; 11. Support assembly; 111. First ring sleeve; 112. Second ring sleeve; 113. Bolt; 114. Nut; 115. Support rod; 116. Lifting component; 12. Connecting hole; 13. Variable diameter interface; 2. Second transmission pipe; 21. Second interface; 3. Pressure-resistant bladder; 31. First connector; 32. Second connector; 4. First liquid storage tank; 5. First pump. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0031] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0032] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0033] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0034] This application discloses an acid fracturing device for multi-stage downward gas drainage boreholes in coal seams, referring to... Figure 1 and Figure 2 The acid fracturing device for multi-stage downward gas extraction boreholes in coal seams includes several first transmission pipes 1 for conveying acidic liquids and several second transmission pipes 2 for conveying water. The ends of the first transmission pipes 1 are provided with first interfaces to connect adjacent first transmission pipes 1. Support components 11 are installed at the connection between adjacent first transmission pipes 1. The ends of the second transmission pipes 2 are provided with second interfaces 21 to connect adjacent second transmission pipes 2. Several pressure-resistant bags 3 are fitted on the second transmission pipes 2. The first transmission pipes 1 are then fitted on the pressure-resistant bags 3 to form a composite structure of pipe-bag-pipe. This structure achieves segmented sealing by expanding the pressure-resistant bags 3 under water pressure and also provides buffer support for the first transmission pipes 1. The first transmission pipes 1 are provided with connecting holes 12 for injecting or discharging acidic liquids into the borehole.

[0035] In this multi-stage downward gas drainage borehole acidizing fracturing device, the first transmission pipe 1 is used to inject or discharge acidic liquid into the borehole. Segmented injection is achieved through connecting holes 12 on the pipe wall, dissolving carbonate minerals in the coal seam and connecting the fracture network. The connecting holes 12 can control the location of the acid's action, solving the problems of unidirectional acid flow and uneven acidification in traditional processes, thus improving gas drainage efficiency. Specifically, the connecting holes 12 serve as channels for acid injection or waste liquid discharge. By controlling the opening position, multi-stage fracturing is achieved, allowing the acid to act directionally on low-permeability coal seams, solving the problem of acid channeling and improving the fracture network's conductivity. The first transmission pipe 1 can be made of corrosion-resistant aluminum to extend its service life.

[0036] The second transmission pipeline 2 is used to inject or discharge clean water for flushing the borehole after acidizing and for pressure regulation. The second transmission pipeline 2 works in conjunction with the first transmission pipeline 1. It can flush away residual acid with clean water to prevent corrosion and optimize the extraction environment. At the same time, it uses water pressure to assist in sealing the pressure-resistant bag 3 and enhance the layered fracturing effect.

[0037] The first interface and the second interface 21 enable quick connection of adjacent pipes, ensuring the continuity of fluid transmission. The standardized interface settings simplify the installation process and adapt to the needs of segmented drilling and laying. The support component 11 is used to fix the connection of the first transmission pipe 1, providing mechanical locking force to prevent pipe misalignment or disconnection, and ensuring the stability and sealing of acid delivery.

[0038] The pressure-resistant bag 3 is fitted outside the second transmission pipe 2. Specifically, the pressure-resistant bag 3 is fixed to the second transmission pipe 2 with screws. Water is injected into the pressure-resistant bag 3 through the second transmission pipe 2 to expand it and achieve a seal, providing buffer support for the dual-pipeline system. It can withstand ground stress and fluid impact, protecting the pipe from compression damage. At the same time, it works with the connecting hole 12 to form segmented isolation, allowing the acid to act on the target layer in a concentrated manner, improving the targeting of fracturing. Specifically, after water is injected into the second transmission pipe 2, the pressure-resistant bag 3 expands and adheres to the borehole wall, dividing the borehole into multiple independent sections. At this time, by controlling the opening of the connecting hole 12, the acid can be injected only into the target section, reducing cross-flow.

[0039] This device delivers acid and clean water in stages through dual pipelines. Combined with the stable connection of the support component 11 and the segmented sealing of the pressure-resistant bag 3, it enables layered acid fracturing and cleaning of multi-segment downward boreholes in the coal seam. The connecting hole 12, in conjunction with the pressure-resistant bag 3, allows acid to be injected into different layers as needed, dissolving minerals and expanding fractures, increasing coal seam permeability and enhancing gas extraction. The support component 11 and the pressure-resistant bag 3 effectively resist complex loads within the borehole, reducing the risk of pipeline leakage and damage, ensuring operational continuity, and reducing construction safety hazards.

[0040] The support assembly 11 includes a first ring 111 and a second ring 112. Several bolts 113 are connected to the first ring 111, and nuts 114 are connected to the bolts 113. The first transmission pipe 1 is located between the first ring 111 and the second ring 112 to lock the first transmission pipe 1. The first ring 111 and the second ring 112 wrap around the first transmission pipe 1 from both sides, forming a clamping structure. This provides a point of force for the bolts 113 to be tightened, jointly constraining the displacement of the first transmission pipe 1 and forming a stable mechanical frame. This fixes the first transmission pipe 1 in the middle, restricting its lateral or longitudinal movement within the borehole caused by ground stress and fluid impact, and maintaining the tightness of the connection of the first transmission pipe 1.

[0041] Bolt 113 passes through the first ring sleeve 111 and the second ring sleeve 112. By tightening the nut 114, an axial tensile force is generated, causing the two ring sleeves to come closer together and squeeze the first transmission pipe 1. The tightness can be adjusted according to the actual working conditions to ensure a firm connection of the pipe. In complex drilling environments, it maintains a continuous locking effect on the pipe, preventing loosening and leakage at the connection, effectively resisting complex stresses in the borehole (such as ground stress and fluid impact), and preventing the first transmission pipe 1 from being misaligned or disconnected due to external forces, ensuring that there is no risk of leakage during the transportation of acidic liquid.

[0042] Support rods 115 are provided on the first ring sleeve 111 and the second ring sleeve 112. A lifting member 116 is installed on the support rod 115. The lifting member 116 is arc-shaped. The support rod 115 connects the first ring sleeve 111, the second ring sleeve 112 and the lifting member 116. As a force transmission medium, it transmits the pipeline pressure borne by the lifting member 116 to the first ring sleeve 111 and the second ring sleeve 112, sharing the weight of the first transmission pipeline 1 and the external pressure, avoiding bending deformation of the pipeline due to its own weight or uneven force, and enhancing the anti-settlement ability of the pipeline system in the borehole.

[0043] The lifting component 116 is arc-shaped, and its arc contour matches the outer wall contour of the first transmission pipeline 1, providing upward support force. The curved surface contact increases the force-bearing area, evenly dispersing pipeline pressure and preventing local stress concentration from causing pipeline wear or dents. At the same time, the arc structure matches the pipeline contour, limiting the radial displacement of the pipeline and further improving pipeline stability, which can resist the influence of complex external forces inside the borehole.

[0044] The support component 11 can effectively alleviate the sagging or displacement of the first transmission pipeline 1 caused by the downward drilling gravity and ground stress, reduce the stress load at the pipeline connection, and reduce the risk of loosening and leakage. At the same time, the stable support ensures that the pipeline position is fixed during acid transportation, ensuring the accuracy and continuity of acid fracturing operations.

[0045] The first transmission pipeline 1 is connected to a first storage tank 4 for storing acidic liquid at one end outside the borehole. A first pump 5, a first flow meter and a first pressure sensor are provided between the first transmission pipeline 1 and the first storage tank 4.

[0046] The first storage tank 4 is used to store sufficient acidic liquid to provide a continuous liquid supply for acid fracturing operations, ensuring sufficient acid during the operation, reducing construction interruptions caused by frequent liquid replenishment, and improving operation efficiency. The first pump 5 serves as a power source to transport the acidic liquid from the storage tank to the first transmission pipeline 1 and provide sufficient pressure to allow the acid to overcome resistance and be injected into the borehole, realizing the directional flow and controllable transportation of the acid. By adjusting the power of the pump, it can adapt to different borehole depths and coal seam permeability requirements, ensuring that the acid effectively reaches the target layer. The acidic liquid can be discharged and recovered in the form of negative pressure pumping.

[0047] The first flow meter monitors the flow rate of the acidic liquid in real time, providing flow data feedback. Operators can adjust the flow rate according to the coal seam characteristics and fracturing progress to ensure that the acid injection volume accurately matches the operational needs. It provides timely warnings when the flow rate is abnormal, reducing the impact of excessive flow on pipeline rupture or insufficient flow on the acidification effect. The first pressure sensor continuously detects the pressure inside the pipeline, monitoring pressure changes during acid delivery to prevent excessive pressure from causing safety hazards (such as pipeline rupture or seal failure), while also avoiding insufficient pressure that could lead to inability to inject acid or uneven distribution. Combined with the flow meter data, it enables precise control of acid delivery parameters.

[0048] The first transmission pipeline 1 is equipped with a reducing port 13 at one end outside the borehole. The reducing port 13 is connected to the first pump 5. The reducing port 13 can adapt to the difference in pipe diameter between the first transmission pipeline 1 and the first pump 5, adjust the cross-sectional area of ​​the fluid transmission channel, optimize the liquid flow path, reduce fluid resistance and pressure loss caused by sudden changes in pipe diameter, reduce eddy currents, and ensure efficient transmission of acidic liquid from the pump body to the pipeline. At the same time, it provides connection compatibility for pipelines and pump equipment of different specifications.

[0049] The second transmission pipeline 2 is connected to a second storage tank for storing water at one end outside the borehole. A second pump, a second flow meter, and a second pressure sensor are installed between the second transmission pipeline 2 and the second storage tank. The second storage tank stores clean water for borehole cleaning and auxiliary operations, providing a stable water source for the entire cleaning process. The second pump acts as a power source to draw clean water from the second storage tank and deliver it to the second transmission pipeline 2, providing the driving force for the clean water to flow in the pipeline. By adjusting the power of the pump, the flow rate and pressure of the clean water are controlled to adapt to different borehole depths and cleaning intensity requirements, ensuring that the clean water effectively flushes away residual acid and impurities in the borehole, providing a water source for the water level anti-pressure bag 3, realizing segmented isolation, and allowing the acid to act on the target layer in a concentrated manner, improving the targeting of fracturing.

[0050] The second flow meter monitors the clean water flow rate in real time and provides feedback on liquid delivery data, offering flow rate references for operators. This helps to accurately control the clean water injection volume, reducing the risk of excessive flow causing a surge in pipeline pressure or insufficient flow leading to incomplete cleaning, thus ensuring efficient and stable cleaning operations. The second pressure sensor continuously monitors pressure changes within the second transmission pipeline 2, providing real-time pressure data to prevent pipeline rupture or seal failure due to excessive pressure, and to avoid insufficient pressure preventing effective clean water delivery. Combined with the flow meter data, dynamic control of the clean water delivery process is achieved, ensuring operational safety.

[0051] The pressure-resistant bag 3 is provided with a first connector 31 to connect the pressure-resistant bag 3 to the first transmission pipe 1, and a second connector 32 to connect the pressure-resistant bag 3 to the second transmission pipe 2. The first connector 31 achieves a stable connection between the pressure-resistant bag 3 and the first transmission pipe 1 through bolts or other connection methods, ensuring that the pressure-resistant bag 3 is fixed on the outside of the first transmission pipe 1. Under the complex stress environment inside the borehole, the relative position of the pressure-resistant bag 3 and the first transmission pipe 1 remains stable, preventing the pressure-resistant bag 3 from shifting or falling off, thereby continuously providing buffer protection and segmented sealing function for the first transmission pipe 1. The second connector 32 fixes the pressure-resistant bag 3 to the second transmission pipeline 2 by means of bolts or other connections, so that the pressure-resistant bag 3 and the second transmission pipeline 2 form a reliable connection, ensuring that the pressure-resistant bag 3 can work together with the second transmission pipeline 2 to bear the force when subjected to external pressure, and preventing the pressure-resistant bag 3 from separating from the second transmission pipeline 2; at the same time, the second connector 32 provides an installation foundation for the pressure-resistant bag 3, ensuring that it can effectively resist ground stress and fluid impact, and protecting the second transmission pipeline 2 from damage.

[0052] Both the inlet and outlet of the first transmission pipe 1 are tapered. The tapered inlet serves as the entrance for acidic liquid into the first transmission pipe 1. The gradually narrowing conical surface guides the liquid to flow smoothly into the pipe, reducing turbulence during entry and minimizing impacts and eddies. This allows the acid to enter the pipe at a more uniform flow rate, ensuring the stability of the subsequent transport process. Simultaneously, the tapered structure facilitates connection with storage tanks, pumps, and other equipment, reducing installation difficulty and improving connection efficiency.

[0053] The conical output end serves as the outlet for the acidic liquid injection borehole. The gradually expanding conical surface disperses the pressure of the liquid flow, allowing the acid to diffuse more evenly through the connecting hole 12 to the target area. This prevents the acid from forming a high-pressure jet at the outlet, thus avoiding excessive local erosion of the borehole wall or coal seam. By dispersing the pressure, the acid can contact the coal seam more smoothly and evenly, improving the effect of acid fracturing and ensuring that the acid fully dissolves carbonate minerals, effectively connecting the fracture network.

[0054] refer to Figures 1-3The implementation process of the acid fracturing device for multi-segment downward gas extraction boreholes in this application is as follows: After completing the downward drilling in the coal seam, the second transmission pipeline 2 is sequentially connected and lowered into the borehole. The pressure-resistant bags 3 are securely fitted onto the second transmission pipeline 2 through the second connector 32, ensuring that the bags are spaced apart along the pipeline. Subsequently, the first transmission pipeline 1 is fitted onto the pressure-resistant bags 3, fixed using the first connector 31, and spliced ​​segment by segment through the first interface. At the same time, a support component 11 is installed at the connection point, and locked with the first ring sleeve 111 and the second ring sleeve 112 in conjunction with bolts 113 and nuts 114. The support is further enhanced by the support rod 115 and the arc-shaped lifting component 116.

[0055] On the ground, the first transmission pipeline 1 is connected to the first storage tank 4, through which the first pump 5, the first flow meter, and the first pressure sensor are connected, and the connection with the pump is optimized through the reducing interface 13; the second transmission pipeline 2 is connected to the second storage tank, and is equipped with the second pump, the second flow meter, and the second pressure sensor. To start the device, clean water is first injected into the second transmission pipeline 2 through the second pump, and the water pressure causes the pressure-resistant bag 3 to expand and adhere to the borehole wall, forming a segmented seal.

[0056] Subsequently, the first pump 5 transports the acidic liquid from the first storage tank 4 to the borehole via the first transmission pipeline 1. According to the preset fracturing scheme, the connecting holes 12 are opened to allow the acidic liquid to be injected directionally into different coal seam sections, dissolving carbonate minerals to open fractures. After acidification is completed, the system switches to clean water delivery mode, and the second pump drives clean water to flush the borehole, removing residual acid and creating conditions for subsequent gas extraction. Alternatively, waste acidic liquid can be discharged through negative pressure. Throughout the process, flow meters and pressure sensors monitor fluid parameters in real time to ensure safe and efficient operation.

[0057] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A coal seam multi-stage downward gas drainage borehole acid fracturing device, characterized in that: It includes several first transmission pipes (1) for conveying acidic liquids and several second transmission pipes (2) for conveying water. The ends of the first transmission pipes (1) are provided with first interfaces to connect adjacent first transmission pipes (1). Support components (11) are installed at the connection of adjacent first transmission pipes (1). The ends of the second transmission pipes (2) are provided with second interfaces (21) to connect adjacent second transmission pipes (2). Several pressure-resistant bags (3) are fitted on the second transmission pipes (2). The first transmission pipes (1) are fitted on the pressure-resistant bags (3). The first transmission pipes (1) are provided with connecting holes (12) for injecting or discharging acidic liquids into the borehole.

2. The acid fracturing device for multi-stage downward gas drainage boreholes in coal seams according to claim 1, characterized in that: The support assembly (11) includes a first ring (111) and a second ring (112). A plurality of bolts (113) are connected to the first ring (111), and nuts (114) are connected to the bolts (113). The first transmission pipe (1) is located between the first ring (111) and the second ring (112) to lock the first transmission pipe (1).

3. The acid fracturing device for multi-stage downward gas drainage boreholes in coal seams according to claim 2, characterized in that: The first ring (111) and the second ring (112) are provided with support rods (115), and the support rods (115) are provided with lifting members (116), which are arranged in an arc shape.

4. The acid fracturing device for multi-stage downward gas drainage boreholes in coal seams according to claim 1, characterized in that: The first transmission pipe (1) is connected to a first storage tank (4) for storing acidic liquid at one end outside the borehole. A first pump (5), a first flow meter and a first pressure sensor are provided between the first transmission pipe (1) and the first storage tank (4).

5. The acid fracturing device for multi-stage downward gas drainage boreholes in coal seams according to claim 4, characterized in that: The first transmission pipe (1) is provided with a variable diameter interface (13) at one end outside the borehole, and the variable diameter interface (13) is connected to the first pump (5).

6. The acid fracturing device for multi-stage downward gas drainage boreholes in coal seams according to claim 1, characterized in that: The second transmission pipe (2) is connected to a second liquid storage tank for storing water at one end outside the borehole. A second pump, a second flow meter and a second pressure sensor are provided between the second transmission pipe (2) and the second liquid storage tank.

7. The acid fracturing device for multi-stage downward gas drainage boreholes in coal seams according to claim 1, characterized in that: The pressure-resistant bag (3) is provided with a first connector (31) to connect the pressure-resistant bag (3) to the first transmission pipe (1), and the pressure-resistant bag (3) is provided with a second connector (32) to connect the pressure-resistant bag (3) to the second transmission pipe (2).

8. The acid fracturing device for multi-stage downward gas drainage boreholes in coal seams according to claim 1, characterized in that: The input and output ends of the first transmission pipe (1) are both tapered.

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