Deep coal seam supercritical CO2 pulse induced crack gas permeability increasing displacement device and method

Abstract

The present application relates to the technical field of deep coal seam mining, in particular to a device and method for gas displacement by supercritical CO2 pulse induced fracturing and permeability enhancement in deep coal seam. The device is composed of a main frame by a cylindrical shell and an outer cylinder, and is internally provided with a liquid CO2 storage bin, a release assembly, a connecting assembly and a reinforcing assembly. Liquid CO2 is injected into the storage bin through a liquid delivery pipe, and high-pressure gaseous CO2 is generated after phase change. The hollow column pushes the push rod to make the inner cylinder slide, realizing the communication between the inner hole and the release outer hole, and the pulse impact of CO2 on the coal seam for fracturing and permeability enhancement. The connecting assembly realizes the stable connection of the cylindrical shell and the outer cylinder by the cooperation of the threaded sleeve plate and the arc block, and the reinforcing assembly further enhances the connection stability by the L-shaped clamping block. The device can effectively improve the gas displacement efficiency and expand the displacement range, and avoid loosening of the device due to vibration, pressure change and other factors under complex geological conditions in deep coal seam, thereby ensuring the normal operation and safety production of the device.

Description

Technical Field

[0001] This invention relates to the field of deep coal seam mining technology, and in particular to a device and method for supercritical CO2 pulse fracturing to enhance permeability and displace gas in deep coal seams. Background Technology

[0002] In deep coal seam mining, the presence of gas not only seriously threatens the safe production of coal mines but also leads to resource waste. Traditional gas displacement methods have many limitations, such as low displacement efficiency and limited displacement range, making it difficult to meet the needs of efficient deep coal seam mining.

[0003] Currently, some gas displacement devices have structural deficiencies. Some devices struggle to precisely control the release volume and direction of the displacement medium, resulting in poor displacement effects. Furthermore, the connections between components are unstable, making them prone to loosening under complex geological conditions in deep coal seams due to vibration, pressure changes, and other factors. This can affect the normal operation of the device and even lead to safety accidents.

[0004] Furthermore, existing gas displacement devices are complex to install and dismantle, requiring significant time and manpower, thus reducing work efficiency. At the same time, their versatility is poor, making them difficult to adapt to deep coal seams with varying geological conditions and mining requirements. Therefore, developing a deep coal seam gas displacement device that can effectively improve displacement efficiency, enhance component connection stability, facilitate installation and dismantling, and has good versatility is of significant practical importance. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies, such as poor connection stability between components, which can easily lead to loosening due to vibration, pressure changes, and other factors in complex geological conditions of deep coal seams, affecting the normal operation of the device and even causing safety accidents. The invention proposes a device and method for supercritical CO2 pulse fracturing, permeability enhancement, and gas displacement in deep coal seams.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A supercritical CO2 pulse fracturing and permeability enhancement gas displacement device for deep coal seams includes a cylindrical shell and an outer cylinder. An activating liquid carbon dioxide storage chamber is fixedly installed inside the cylindrical shell, and a liquid CO2 phase change activating device is installed inside the activating liquid carbon dioxide storage chamber. An end cap is fixedly installed at one end of the cylindrical shell, and a liquid carbon dioxide delivery pipe is fixedly inserted through the end cap. The liquid carbon dioxide delivery pipe is fixedly connected to the activating liquid carbon dioxide storage chamber.

[0008] A hollow tube connected to the end of the liquid carbon dioxide storage chamber is fixedly installed at the end away from the end cap, and a fixed connecting block connected to the end of the hollow tube connected to the end away from the liquid carbon dioxide storage chamber is fixedly installed at the end of the hollow tube.

[0009] The outer cylinder is equipped with a release component inside. The cylindrical outer shell and the outer cylinder are detachably and fixedly connected by a connecting component. The fixed connecting block is equipped with a reinforcing component to enhance the connection stability between the cylindrical outer shell and the outer cylinder.

[0010] Liquid CO2 is injected into the liquid carbon dioxide storage chamber through the liquid carbon dioxide delivery pipe. The liquid CO2 phase change excitation device generates high-pressure gaseous CO2 through phase change. The high-pressure gaseous CO2 is transported to the release component through the hollow tube and fixed connecting block. The release component releases the CO2 into the coal seam to achieve pulse fracturing and permeability enhancement. The reinforced component can prevent the device from loosening under complex geological conditions.

[0011] In one possible design, the release assembly includes an inner cylinder slidably connected to the inner wall of the outer cylinder, with multiple connecting rods fixedly installed inside the inner cylinder, and a common push rod fixedly installed at one end of each of the multiple connecting rods that are close to each other; the outer wall of the inner cylinder has multiple release inner holes, and the outer cylinder has multiple release outer holes, which are adapted to the release inner holes;

[0012] A tension spring connects the annular fixing plate I, which is fixedly installed on the inner wall of the inner cylinder and the outer cylinder. High-pressure gaseous CO2 pushes the push rod to drive the inner cylinder to slide, so that the release inner hole and the release outer hole are connected to release CO2. The tension spring can drive the inner cylinder to reset.

[0013] In one possible design, the connecting assembly includes a threaded sleeve, the outer wall of the cylindrical outer shell is provided with a threaded groove II, the outer wall of the outer cylinder is provided with a threaded groove I, and the threaded sleeve is threadedly connected to both threaded groove I and threaded groove II.

[0014] The threaded sleeve is rotatably connected to an annular fixing plate II. Multiple arc-shaped blocks II are fixedly installed on the inner wall of the annular fixing plate II, and multiple arc-shaped blocks I are fixedly installed on the outer wall of the fixed connecting block.

[0015] The outer cylinder has multiple arc-shaped notches at one end near the cylindrical shell, and an annular groove communicating with the arc-shaped notches is opened inside the outer cylinder. Arc-shaped block I is embedded into the annular groove through the arc-shaped notches, and arc-shaped block II is inserted into the arc-shaped notches and engaged with arc-shaped block I to improve connection stability.

[0016] In one possible design, the reinforcing component includes multiple sliding grooves I formed at one end of the fixed connecting block, each sliding groove I having a slider I slidably connected therein, a compression spring abutting between the slider I and the inner wall of the top of the sliding groove I, and an L-shaped locking block fixedly installed at one end of the slider I, with a sloping groove formed on one side of the bottom of the L-shaped locking block.

[0017] In one possible design, the fixed connecting block has a circular hole inside, and two symmetrical sliding grooves II are formed on the inner wall of the circular hole. The same hollow column is slidably connected in the two sliding grooves II, and the hollow column is slidably engaged with the sliding grooves II through a slider II. The outer wall of the hollow column has two symmetrical rectangular holes, and one end of the hollow column has a hollow groove communicating with the rectangular holes. One end of the hollow column is adapted to multiple inclined grooves, and the hollow column is correspondingly set with the push rod.

[0018] In one possible design, when high-pressure gaseous CO2 is injected into the hollow groove through the circular hole, the rectangular hole fits against the inner wall of the circular hole to seal the gas. The gas pressure pushes the hollow column to slide laterally, causing the rectangular hole to expose the fixed connecting block to release the gas. At the same time, the hollow column squeezes the inclined groove, causing the L-shaped locking block to press against the side of the annular fixing plate I away from the annular groove, further enhancing the connection stability.

[0019] In one possible design, the cylindrical outer shell is made of high-strength alloy steel, the outer cylinder is made of tough steel, the inner cylinder is made of wear-resistant alloy steel, and the threaded sleeve is made of high-strength engineering plastic.

[0020] In one possible design, the end of the outer cylinder away from the cylindrical shell is connected to a threaded block by a thread, and the end of the threaded block away from the outer cylinder is fixedly fitted with a fixing tip, which is made of a high-hardness alloy material.

[0021] In one possible design, the number and diameter of the inner and outer release holes can be adjusted according to the geological conditions of the coal seam to adapt to different gas displacement requirements.

[0022] A method for supercritical CO2 pulse-induced fracturing and permeability enhancement to displace gas in deep coal seams, employing the aforementioned apparatus, includes the following steps:

[0023] S1. Insert the device into the coal seam borehole through the fixed tip, and lock it with the arc block I and the annular groove and the threaded sleeve to achieve a fixed connection between the cylindrical shell and the outer cylinder;

[0024] S2. Liquid CO2 is injected into the liquid carbon dioxide storage chamber through the liquid carbon dioxide delivery pipe, and the liquid CO2 phase change excitation device is started to generate high-pressure gaseous CO2 from the liquid CO2 phase change.

[0025] S3. High-pressure gaseous CO2 propels the hollow column to slide, causing the L-shaped locking block to press against the annular fixing plate I. Simultaneously, it pushes the push rod to slide the inner cylinder, releasing the inner hole and the outer hole. Supercritical CO2 fluid is released in a pulsed manner. Utilizing the high-pressure gas wedge effect and vibration wave effect, a fracture network is created in the coal seam, connecting macroscopic fractures and microscopic pores. Supercritical CO2 molecules enter the micropores of the coal matrix, converting adsorbed gas into free gas through displacement desorption, and forming high-speed seepage channels in the fracture network, achieving deep fracturing and permeability enhancement of the coal seam.

[0026] S4. Connect the coal seam borehole to the external extraction equipment. The displaced gas is extracted and collected through the borehole. Data after the operation shows that the gas extraction volume of a single hole is 3-5 times higher than that of traditional blasting and fracturing. The gas extraction concentration is increased by an average of 40%-60%. The effective extraction period is extended to 6-12 months, which significantly reduces the risk of coal and gas outbursts. After the operation is completed, rotate the threaded sleeve in the opposite direction to separate the cylindrical shell and the outer cylinder to disassemble the device.

[0027] In this application, during use, liquid CO2 is supplied to the liquid CO2 storage chamber via a liquid CO2 delivery pipe. The liquid CO2 phase change excitation device is activated, triggering a phase change in the liquid CO2 within the storage chamber. During this process, the liquid CO2 absorbs heat and undergoes a phase change within an extremely short time (milliseconds), instantly expanding its volume by more than 600 times, forming a supercritical CO2 fluid with high density, low viscosity, and a high diffusion coefficient. The generated high-pressure gaseous (supercritical) CO2 is then transported into the hollow groove through a circular hole. Because the rectangular hole fits the inner wall of the circular hole, the gas cannot escape. At this point, the hollow column can be pushed laterally, causing the slider II to slide inside the groove II until the rectangular hole moves to the outside of the fixed connecting block. At this point, the gas can escape normally and push the push rod forward via the hollow column. The push rod then pushes the connecting rod forward, connecting the inner and outer release holes. The tension spring is stretched, and the high-energy supercritical CO2 fluid accumulated in the device is instantly ejected through the release hole, forming a high-pressure pulse shock wave. The peak pressure of this shock wave can reach 100-300 MPa, far exceeding the tensile and compressive strength of deep coal seams.

[0028] The supercritical CO2 pulse fracturing process is as follows: First, high-energy gas weds into the original fractures of the coal body, generating tensile stress that causes the main fracture to expand; second, supercritical CO2 fluid, taking advantage of its low viscosity, rapidly penetrates into the micropores of the coal body. Because its adsorption capacity for the coal matrix is ​​stronger than that for methane, it competitively adsorbs and displaces the adsorbed methane, causing the methane to desorb and become free; finally, the high-pressure pulse forms a complex three-dimensional fracture network inside the coal seam, with an effective fracturing radius of 5-8 meters.

[0029] Actual measurements show that after fracturing with this device, the coal seam permeability coefficient increased from the original 0.003-0.05 m² / (MPa²·d) to 0.2-1.5 m² / (MPa²·d), representing a 20-50 fold increase in permeability.

[0030] Furthermore, when the hollow column moves laterally, the hollow column cooperates with the inclined groove. At this time, the L-shaped block drives the slider I to move inside the groove I. At this time, the compression spring is squeezed, and one end of the L-shaped block abuts against the side of the annular fixing plate I away from the annular groove, which can improve the stability of the connection between the cylindrical shell and the outer cylinder and prevent the device from loosening.

[0031] Furthermore, when installing the cylindrical outer shell and the outer cylinder, the arc-shaped block I needs to be aligned with the arc-shaped notch first, so that the arc-shaped block I enters the interior of the annular groove. At this time, the outer cylinder is rotated, and the arc-shaped block I can be placed inside the annular groove and offset from the arc-shaped notch. The threaded sleeve is rotated, and the threaded sleeve moves forward from the outer wall of the threaded groove II. The other end of the threaded sleeve moves to the outer wall of the threaded groove I, thereby realizing the connection between the outer cylinder and the cylindrical outer shell. The arc-shaped block II enters the interior of the arc-shaped notch, so that the arc-shaped block II can be inserted into the interior of the arc-shaped block I, thereby ensuring the stability of multiple arc-shaped blocks I.

[0032] Beneficial Effects: This deep coal seam supercritical CO2 pulse fracturing and permeability enhancement gas displacement device generates high-pressure gaseous (supercritical) CO2 by stimulating the phase change of liquid CO2 in the liquid carbon dioxide storage chamber. Utilizing the low viscosity, high diffusion coefficient, and enormous expansion energy (volume expansion of over 600 times) of the supercritical CO2 fluid, a high-energy pulsed shock wave is generated within the coal seam. The peak pressure of this shock wave can reach 100-300 MPa, effectively fracturing hard coal seams and forming a three-dimensional fracture network with a radius of 5-8 meters, increasing the coal seam's permeability coefficient by 20-50 times. The high-pressure gaseous CO2 is transported through a specific structure and propels related components, connecting the inner and outer release orifices, thereby accurately and powerfully impacting the coal seam with CO2. This effectively improves the gas displacement efficiency, expands the displacement range, and better meets the needs of deep coal seam mining.

[0033] The device utilizes the superior adsorption capacity of supercritical CO2 on coal matrix compared to methane, achieving competitive adsorption and replacement. Supercritical CO2 penetrates the micropores of the coal, displacing adsorbed methane into free methane, which is then rapidly discharged along the fracture network. Practical applications show that the pure methane extraction volume per borehole is 3-5 times higher than traditional methods, and the average methane extraction concentration is increased by 40%-60%, effectively extending the effective extraction period of the borehole and significantly reducing the risk of coal and gas outbursts.

[0034] During operation, when the hollow column moves laterally, it engages with the inclined groove, causing the L-shaped locking block to move. This compresses the spring, and one end of the L-shaped locking block contacts the side of the annular fixing plate I furthest from the annular groove. This structure effectively improves the stability of the connection between the cylindrical outer shell and the outer cylinder, preventing the device from loosening due to vibration, pressure changes, or other factors under complex geological conditions in deep coal seams, thus ensuring the normal operation and safe production of the device.

[0035] When installing the cylindrical outer shell and outer cylinder, first align the arc-shaped block I with the arc-shaped notch, allowing it to enter the annular groove. Rotate the outer cylinder to place the arc-shaped block I within the annular groove, offsetting it from the arc-shaped notch. Then, rotate the threaded sleeve plate, moving it from the outer wall of threaded groove II to the outer wall of threaded groove I, thus connecting the outer cylinder and the cylindrical outer shell. Simultaneously, arc-shaped block II enters the arc-shaped notch and engages with arc-shaped block I, ensuring the stability of multiple arc-shaped blocks I. This installation method is simple to operate, and disassembly is performed by reversing the operation, greatly saving installation and disassembly time and manpower, and improving work efficiency.

[0036] When high-pressure gaseous CO2 is conveyed into the hollow groove through the circular hole, the gas cannot escape because the rectangular hole fits into the inner wall of the circular hole. At this point, the hollow column can be moved laterally. Once the rectangular hole moves outside the fixed connecting block, the gas can be released normally and pushes the push rod through the hollow column, thus connecting the inner and outer release holes. This structure allows for precise control of the timing and amount of CO2 release, achieving precise control of the gas displacement process. It ensures that release is only initiated instantaneously when the pressure reaches the preset fracturing threshold, thereby producing a stronger pulse fracturing effect.

[0037] The device has a reasonable structural design and can adapt to deep coal seams with different geological conditions and mining requirements. By adjusting the parameters and specifications of relevant components, such as changing the size and number of the inner and outer release holes, it can meet the gas displacement requirements of different coal seams, and has high versatility and adaptability. Attached Figure Description

[0038] Figure 1 This is a three-dimensional structural schematic diagram of the supercritical CO2 pulse fracturing and permeation enhancement gas displacement device for deep coal seams proposed in this invention.

[0039] Figure 2 This is an exploded view of the entire supercritical CO2 pulse fracturing and permeation enhancement gas displacement device for deep coal seams proposed in this invention.

[0040] Figure 3 This is an exploded view of the outer cylinder and fixed tip of the deep coal seam supercritical CO2 pulse fracturing and permeation enhancement gas displacement device proposed in this invention;

[0041] Figure 4This is a three-dimensional cross-sectional view of the outer and inner cylinders of the deep coal seam supercritical CO2 pulse fracturing permeability enhancement and gas displacement device proposed in this invention.

[0042] Figure 5 This is a three-dimensional view of the arc-shaped block I and the cylindrical outer shell in the deep coal seam supercritical CO2 pulse fracturing and permeation enhancement gas displacement device proposed in this invention;

[0043] Figure 6 This is an exploded view of the cylindrical outer shell and the storage chamber for induced liquid carbon dioxide in the deep coal seam supercritical CO2 pulse fracturing and permeation enhancement gas displacement device proposed in this invention.

[0044] Figure 7 This is an exploded view of the threaded sleeve and fixed connecting block in the deep coal seam supercritical CO2 pulse fracturing permeability enhancement and gas displacement device proposed in this invention.

[0045] Figure 8 This is an exploded view of the fixed connecting block and L-shaped clamping block in the deep coal seam supercritical CO2 pulse fracturing and permeation enhancement gas displacement device proposed in this invention.

[0046] Figure 9 This is an exploded view of the fixed connecting block and hollow column in the deep coal seam supercritical CO2 pulse fracturing permeability enhancement and gas displacement device proposed in this invention.

[0047] In the diagram: 1. Cylindrical outer shell; 2. Threaded sleeve plate; 3. Outer cylinder; 4. Fixed tip; 5. End cap; 6. Liquid carbon dioxide infusion tube; 7. Release outer hole; 8. Threaded groove I; 9. Arc-shaped block I; 10. Connecting threaded block; 11. Arc-shaped notch; 12. Annular groove; 13. Annular fixing plate I; 14. Inner cylinder; 15. Release inner hole; 16. Connecting rod; 17. Push rod; 18. Tension spring; 19. Threaded groove II; 20. Ignition liquid carbon dioxide storage chamber; 21. Fixed connecting block; 22. Arc-shaped block II; 23. Hollow tube; 24. L-shaped locking block; 25. Annular fixing plate II; 26. Slide groove I; 27. Hollow column; 28. Inclined groove; 29. ​​Slider I; 30. Compression spring; 31. Hollow groove; 32. Slide groove II; 33. Round hole; 34. Slider II; 35. Rectangular hole. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0049] In one embodiment: Refer to Figure 1-9The supercritical CO2 pulse-induced fracturing and permeation enhancement gas displacement device comprises a cylindrical outer shell 1 and an outer cylinder 3. The cylindrical outer shell 1 is made of high-strength alloy steel to withstand the high-pressure environment of deep coal seams, while the outer cylinder 3 is made of steel with a certain degree of toughness to ensure that it is not easily deformed under complex geological conditions. An ignition liquid carbon dioxide storage chamber 20 is fixedly installed inside the cylindrical outer shell 1. The ignition liquid carbon dioxide storage chamber 20 is a high-pressure resistant sealed container, and it contains a liquid CO2 phase change ignition device. To achieve phase change ignition of liquid carbon dioxide, this ignition device can rapidly heat the liquid carbon dioxide to achieve phase change through methods such as electric heating. An end cap 5 is fixedly installed at the end of the cylindrical outer shell 1 away from the outer cylinder 3. The end cap 5 is made of the same material as the cylindrical outer shell 1 and is fixed by welding. A liquid carbon dioxide delivery pipe 6 is fixedly inserted through the end cap 5. The liquid carbon dioxide delivery pipe 6 is made of high-pressure resistant metal pipe and is connected to the ignition liquid carbon dioxide storage chamber 20 through a sealed joint to ensure that there is no leakage during the liquid carbon dioxide transportation process. A hollow tube 23 is fixedly installed at the other end of the liquid carbon dioxide storage chamber 20. The hollow tube 23 is made of a material similar to that of an infusion tube. A fixed connecting block 21 is fixedly installed at one end of the hollow tube 23.

[0050] Multiple arc-shaped notches 11 are formed at one end of the outer cylinder 3 near the cylindrical outer shell 1. An annular groove 12 is formed inside the outer cylinder 3, and the annular groove 12 is connected to the multiple arc-shaped notches 11. An annular fixing plate I 13 is fixedly installed on the inner wall of the outer cylinder 3, and the annular fixing plate I 13 is located on one side of the annular groove 12. A release assembly for releasing CO2 is set inside the outer cylinder 3. Specifically, the release assembly includes an inner cylinder 14 slidably connected to the inner wall of the outer cylinder 3. The inner cylinder 14 is made of wear-resistant steel to reduce frictional wear with the inner wall of the outer cylinder 3. Multiple connecting rods 16 are fixedly installed inside the inner cylinder 14, and the same push rod 17 is fixedly installed at one end of the multiple connecting rods 16 close to each other. Multiple release inner holes 15 are formed on the outer wall of the inner cylinder 14, and multiple release outer holes 7 are formed inside the outer cylinder 3. The release outer holes 7 are used in conjunction with the release inner holes 15. A tension spring 18 is set between one side of the inner cylinder 14 and one side of the annular fixing plate I 13. Both ends of the tension spring 18 are connected to one end of the inner cylinder 14 and one side of the annular fixing plate I 13 through hooks. Based on this, when the device is started, the high-pressure gaseous CO2 pushes the push rod 17, which moves the inner cylinder 14, so that the release inner hole 15 is connected to the release outer hole 7, thereby releasing CO2. The tension spring 18 is stretched during the movement of the inner cylinder 14, and helps the inner cylinder 14 to return to its original position after the release is completed.

[0051] The outer wall of the cylindrical outer shell 1 has a threaded groove II19, and the outer wall of the outer cylinder 3 has a threaded groove I8. The same set of connecting components is provided on the threaded grooves I8 and II19. Specifically, the connecting components include a threaded sleeve 2, which is made of high-strength plastic to reduce the overall weight of the device. The threaded sleeve 2 is rotatably connected to an annular fixing plate II25. Multiple arc-shaped blocks II22 are fixedly installed on the inner wall of the annular fixing plate II25. The arc-shaped blocks II22 engage with the arc-shaped notch 11. Multiple arc-shaped blocks I9 are fixedly installed on the outer wall of the fixed connecting block 21. The arc-shaped blocks I9 cooperate with the arc-shaped notch 11 and the annular groove 12. When installing the cylindrical outer shell 1 and the outer cylinder 3, first align the arc-shaped block I9 with the arc-shaped notch 11 so that the arc-shaped block I9 enters the annular groove 12. At this time, rotate the outer cylinder 3 to place the arc-shaped block I9 inside the annular groove 12 and offset it from the arc-shaped notch 11. Rotate the threaded sleeve 2, and the threaded sleeve 2 moves forward from the outer wall of the threaded groove II 19, and the other end moves to the outer wall of the threaded groove I 8, so that the outer cylinder 3 and the cylindrical outer shell 1 are connected. The arc-shaped block II 22 enters the arc-shaped notch 11 and is inserted into the arc-shaped block I9 to ensure the stability of multiple arc-shaped blocks I9.

[0052] A reinforcing component is provided at one end of the fixed connecting block 21 to further strengthen the connection between the cylindrical outer shell 1 and the outer cylinder 3. Specifically, the reinforcing component includes multiple sliding grooves I26 formed at one end of the fixed connecting block 21. A slider I29 is slidably connected inside the sliding grooves I26. A compression spring 30 is provided between the top of the slider I29 and the inner wall of the top of the sliding groove I26. Both ends of the compression spring 30 abut against the inner wall of the top of the sliding groove I26 and the top of the slider I29 through spring seats. An L-shaped locking block 24 is fixedly installed at one end of the slider I29. An inclined groove 28 is formed on one side of the bottom of the L-shaped locking block 24. Furthermore, a circular hole 33 is formed inside the fixed connecting block 21. Two symmetrically arranged sliding grooves II 32 are formed on the inner wall of the circular hole 33. Sliding sliders II 34 are slidably connected inside the sliding grooves II 32. The same hollow column 27 is fixedly installed between the two sliding sliders II 34. The hollow column 27 is made of lightweight alloy material. Two symmetrically arranged rectangular holes 35 are formed on the outer wall of the hollow column 27. A hollow groove 31 is formed at one end of the hollow column 27, and the hollow groove 31 is connected to the rectangular hole 35. Furthermore, one end of the hollow column 27 cooperates with multiple inclined grooves 28. The hollow column 27 is located at one end of the push rod 17 and is used in conjunction with the push rod 17. In use, liquid CO2 is supplied to the liquid CO2 storage chamber through the liquid CO2 delivery pipe. The liquid CO2 phase change excitation device is activated, triggering a phase change in the liquid CO2 within the storage chamber, generating high-pressure gaseous CO2. This high-pressure gaseous CO2 is then supplied into the hollow groove 31 through the circular hole 33. At this point, because the rectangular hole 35 fits against the inner wall of the circular hole 33, the gas cannot escape. This allows the hollow column 27 to move laterally. The hollow column 27 drives the slider II 34 to slide inside the sliding groove II 32 until the rectangular hole 35 moves outside the fixed connecting block 21. Only then can the gas escape normally and pass through the hollow column 27. 7. Push the push rod 17 forward, and the push rod 17 drives the connecting rod 16 forward. At this time, the release inner hole 15 is connected to the release outer hole 7, and the tension spring 18 is stretched. It impacts the coal seam outside the pressure relief hole through the release outer hole 7 and the release inner hole 15. When the hollow column 27 moves laterally, the hollow column 27 cooperates with the inclined groove 28. At this time, the L-shaped block 24 drives the slider I 29 to move inside the groove I 26. The compression spring 30 is squeezed. One end of the L-shaped block 24 abuts against the side of the annular fixing plate I 13 away from the annular groove 12, which improves the connection stability of the cylindrical shell 1 and the outer cylinder 3 and prevents the device from loosening.

[0053] This application can be used in the field of deep coal seam mining, or in other fields applicable to this application.

[0054] In another embodiment: Reference Figure 1-9The device and method for supercritical CO2 pulse fracturing and permeability enhancement and gas displacement in deep coal seams are applied in the field of deep coal seam mining. The structure of this embodiment is basically the same as that of the previous embodiment, except that: on this basis, one end of the outer cylinder 3 is threadedly connected to the threaded block 10, the threaded block 10 is made of the same material as the outer cylinder 3, and a fixing tip 4 is fixedly installed at one end of the threaded block 10. The fixing tip 4 is made of high hardness alloy material so as to better insert into the coal seam and fix the position of the device. Through its structure and operating method, this device can effectively improve gas displacement efficiency in deep coal seam mining. High-pressure gaseous CO2 pulse impacts the coal seam, expanding the displacement range and overcoming the limitation of traditional methods. The stable connections of all components reduce loosening caused by vibration and pressure changes in complex geological conditions of deep coal seams, ensuring normal operation and reducing the risk of safety accidents. Installation and disassembly are relatively simple, with threaded connections and locking structures reducing installation and disassembly time and labor costs, thus improving work efficiency. Furthermore, the device has good versatility; its parameters and installation methods can be adjusted according to different geological conditions and mining needs, adapting to various deep coal seam environments.

[0055] However, as is well known to those skilled in the art, the working principle and wiring method of the liquid carbon dioxide storage chamber 20 and the liquid CO2 phase change excitation device are conventional methods or common knowledge. The liquid carbon dioxide storage chamber 20 and the liquid CO2 phase change excitation device are consistent with the one proposed in the announcement number CN116255124B, which describes a CO2 automatic misalignment fracturing coal seam permeability enhancement device and a gas enhanced extraction method. Therefore, they will not be described in detail here. Those skilled in the art can make any selections according to their needs or convenience.

[0056] The above description is only 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 device for supercritical CO2 pulse fracturing and permeability enhancement to displace and replace gas in deep coal seams, characterized in that, include: The cylindrical shell (1) and the outer cylinder (3) are provided. An excitation liquid carbon dioxide storage chamber (20) is fixedly installed inside the cylindrical shell (1). A liquid CO2 phase change excitation device is provided inside the excitation liquid carbon dioxide storage chamber (20). An end cap (5) is fixedly installed at one end of the cylindrical shell (1). A liquid carbon dioxide delivery pipe (6) is fixedly inserted through the end cap (5). The liquid carbon dioxide delivery pipe (6) is fixedly connected to the excitation liquid carbon dioxide storage chamber (20). The end of the activated liquid carbon dioxide storage chamber (20) away from the end cap (5) is fixedly installed with a hollow tube (23) communicating with it, and the end of the hollow tube (23) away from the activated liquid carbon dioxide storage chamber (20) is fixedly installed with a fixed connecting block (21) communicating with it. The outer cylinder (3) is equipped with a release component. The cylindrical shell (1) and the outer cylinder (3) are detachably and fixedly connected by a connecting component. The fixed connecting block (21) is equipped with a reinforcing component to enhance the connection stability between the cylindrical shell (1) and the outer cylinder (3). Liquid CO2 is injected into the liquid carbon dioxide storage chamber (20) through the liquid carbon dioxide delivery pipe (6). The liquid CO2 phase change is activated by the liquid CO2 phase change activation device to generate high-pressure gaseous CO2. The high-pressure gaseous CO2 is transported to the release component through the hollow tube (23) and the fixed connecting block (21). The release component releases the CO2 into the coal seam to achieve pulse fracturing and permeability enhancement. The reinforcing component includes multiple slid grooves I (26) opened at one end of the fixed connecting block (21). Each slid groove I (26) is slidably connected with a slider I (29). A compression spring (30) is abutted between the slider I (29) and the inner wall of the top of the slid groove I (26). An L-shaped locking block (24) is fixedly installed at one end of the slider I (29). The L-shaped locking block (24) has a sloping groove (28) on one side of its bottom. The fixed connecting block (21) has a round hole (33) inside. The inner wall of the round hole (33) has two symmetrical sliding grooves II (32). The same hollow column (27) is slidably connected in the two sliding grooves II (32). The hollow column (27) is slidably engaged with the sliding grooves II (32) through a slider II (34). The release assembly includes an inner cylinder (14) slidably connected to the inner wall of the outer cylinder (3). Multiple connecting rods (16) are fixedly installed inside the inner cylinder (14), and the same push rod (17) is fixedly installed at one end of each connecting rod (16) that is close to each other; two symmetrical rectangular holes (35) are opened on the outer wall of the hollow column (27), and a hollow groove (31) communicating with the rectangular hole (35) is opened at one end of the hollow column (27). One end of the hollow column (27) is adapted to multiple inclined grooves (28), and the hollow column (27) and the push rod (17) are correspondingly arranged.

2. The deep coal seam supercritical CO2 pulse fracturing and permeability enhancement gas displacement device according to claim 1, characterized in that, The outer wall of the inner cylinder (14) is provided with a plurality of release inner holes (15), and the outer cylinder (3) is provided with a plurality of release outer holes (7), the release outer holes (7) being adapted to the release inner holes (15); A tension spring (18) is connected between the inner cylinder (14) and the annular fixing plate I (13) fixedly installed on the inner wall of the outer cylinder (3). High-pressure gaseous CO2 pushes the push rod (17) to drive the inner cylinder (14) to slide, so that the release inner hole (15) and the release outer hole (7) are connected to release CO2. The tension spring (18) can drive the inner cylinder (14) to reset.

3. The deep coal seam supercritical CO2 pulse fracturing and permeability enhancement gas displacement device according to claim 2, characterized in that, The connecting assembly includes a threaded sleeve (2), the outer wall of the cylindrical shell (1) is provided with a threaded groove II (19), the outer wall of the outer cylinder (3) is provided with a threaded groove I (8), and the threaded sleeve (2) is threadedly connected to both the threaded groove I (8) and the threaded groove II (19). The threaded sleeve (2) is rotatably connected to an annular fixing plate II (25), and multiple arc-shaped blocks II (22) are fixedly installed on the inner wall of the annular fixing plate II (25), and multiple arc-shaped blocks I (9) are fixedly installed on the outer wall of the fixed connecting block (21). The outer cylinder (3) has multiple arc-shaped notches (11) at one end near the cylindrical shell (1). The outer cylinder (3) has an annular groove (12) that communicates with the arc-shaped notches (11). The arc-shaped block I (9) is embedded into the annular groove (12) through the arc-shaped notches (11), and the arc-shaped block II (22) is inserted into the arc-shaped notches (11) and engaged with the arc-shaped block I (9).

4. The deep coal seam supercritical CO2 pulse fracturing and permeability enhancement gas displacement device according to claim 3, characterized in that, When high-pressure gaseous CO2 is injected into the hollow groove (31) through the round hole (33), the rectangular hole (35) fits against the inner wall of the round hole (33) to seal the gas. The gas pressure pushes the hollow column (27) to slide laterally, so that the rectangular hole (35) is exposed to the fixed connecting block (21) to release the gas. At the same time, the hollow column (27) squeezes the inclined groove (28) and drives the L-shaped card block (24) to press against the side of the annular fixed plate I (13) away from the annular groove (12).

5. The deep coal seam supercritical CO2 pulse fracturing and permeability enhancement gas displacement device according to claim 4, characterized in that, The cylindrical outer shell (1) is made of high-strength alloy steel, the outer cylinder (3) is made of tough steel, and the inner cylinder (14) is made of wear-resistant alloy steel.

6. The deep coal seam supercritical CO2 pulse fracturing and permeability enhancement gas displacement device according to claim 5, characterized in that, The outer cylinder (3) is connected to a threaded block (10) at one end away from the cylindrical shell (1) by a thread, and a fixed tip (4) is fixedly installed at the other end of the threaded block (10) away from the outer cylinder (3).

7. The deep coal seam supercritical CO2 pulse fracturing and permeability enhancement / gas displacement device according to claim 6, characterized in that, The number and diameter of the release inner hole (15) and release outer hole (7) are adjusted according to the geological conditions of the coal seam.

8. A method for supercritical CO2 pulse-induced fracturing and permeability enhancement to displace and replace gas in deep coal seams, characterized in that, The apparatus of claim 7 comprises the following steps: S1. Insert the device into the coal seam borehole through the fixed tip (4), and lock it with the arc block I (9) and the annular groove (12) and the threaded sleeve (2) to achieve a fixed connection between the cylindrical shell (1) and the outer cylinder (3); S2. Liquid CO2 is injected into the liquid carbon dioxide storage chamber (20) through the liquid carbon dioxide delivery pipe (6) to start the liquid CO2 phase change excitation device, so that the liquid CO2 phase change generates high pressure gaseous CO2. S3. High-pressure gaseous CO2 pushes the hollow column (27) to slide, causing the L-shaped block (24) to press against the annular fixing plate I (13). At the same time, it pushes the push rod (17) to make the inner cylinder (14) slide, releasing the inner hole (15) and the outer hole (7) to connect. The supercritical CO2 fluid is released in the form of pulses. Using the high-pressure gas wedge effect and the vibration wave effect, the coal body generates a fracture network with macroscopic cracks and microscopic pores. The supercritical CO2 molecules enter the micropores of the coal matrix and convert the adsorbed gas into free gas through displacement desorption. They also form a high-speed seepage channel in the fracture network to realize deep fracturing and permeability displacement of the coal seam. S4. Connect the coal seam borehole through the external extraction equipment. The displaced gas is discharged and collected through the borehole. After the operation is completed, rotate the threaded sleeve (2) in the opposite direction to separate the cylindrical shell (1) and the outer cylinder (3) to disassemble the device.

Images