Coal mine gas extraction device and method

Abstract

The invention provides a coal mine gas extraction device and method, and belongs to the technical field of coal mine underground gas extraction. According to the technical scheme, the coal mine gas extraction device comprises a drill rod, a drill bit is arranged at the end of the drill rod, and a stress frame is fixedly connected to the drill bit; a geological parameter sensing unit and a hydraulic branch actuator sleeve the drill rod close to the drill bit, and the geological parameter sensing unit is arranged at the end, close to the drill rod, of the drill bit and can collect coal seam geological parameters; the output end of the hydraulic branch actuator is connected with the stress frame through a ball hinge joint. According to the coal mine gas extraction method, the self-adaptive branch control assembly drives the drill bit to deflect by a preset angle according to geological parameters. The device has the beneficial effects that the geological parameter sensing unit can capture key information such as coal seam stress and gas concentration in real time, a basis is provided for adjustment of the drilling direction, and the hydraulic branch actuator is connected with the spherical hinge of the stress frame, so that a drill bit can be flexibly driven to deflect to adapt to geological changes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coal mine underground gas extraction, and particularly relates to a coal mine gas extraction device and method. BACKGROUND

[0002] In the coal mine underground mining operation, gas, as a coal seam associated gas, is not only the core hidden danger of causing explosion, poisoning and other safety accidents, but also has very high energy utilization value. Therefore, coal mine gas extraction is a key link to ensure the safety of underground operation and realize resource recovery. The current industry generally follows the principle of extraction before mining and extraction balance. Through drilling extraction to reduce the concentration of coal seam gas, it is not only a hard requirement to meet the coal mine safety production regulations, but also a basic prerequisite to promote the resource utilization of gas. It plays an irreplaceable role in efficient, safe and green mining of coal mines.

[0003] As shown in the patent with the announcement number CN115324482B, in the existing coal mine gas extraction technology, in view of the hole protection and drilling problems of soft coal seam, a drilling and hole protection collaborative technical solution has been developed. The typical structure is the combination of the hole protection pipe and the drill pipe. The hole protection pipe is composed of an actual pipe and a flower pipe connected alternately, and is sleeved in the drill pipe and advances synchronously with the drill pipe. High-pressure water is introduced into the drill pipe to complete the deslagging and drill bit cooling. A polyurethane foam ring is arranged between the hole protection pipe and the drill pipe to prevent the hole protection pipe from being damaged by the torque of the drill pipe, so that the hole protection pipe is successfully sent to the designed depth.

[0004] However, the existing technology can only realize straight drilling and passive hole protection while drilling, and lacks the ability to dynamically adjust the drilling direction according to the geological conditions. In the operation of deep holes above 300 meters, soft coal seams are prone to drilling deviation due to uneven stress, which not only cannot accurately reach the gas enrichment area, greatly reducing the deep hole completion rate, but also limits the extraction range to the periphery of the main hole, making it impossible to form a multi-branch hole coverage, thereby generating a large number of extraction blind areas. Gas residues are easy to cause safety hazards, seriously affecting the efficiency of gas extraction and the safety of underground operation. SUMMARY

[0005] The application provides a coal mine gas extraction device and method to solve the problem of drilling deviation of soft coal seams due to uneven stress and the generation of extraction blind areas in the existing gas extraction process. The device and method can ensure the accuracy of the extraction drilling position and effectively avoid the occurrence of extraction blind areas.

[0006] Firstly, to solve the above problems, the technical solution adopted in this application is as follows: a coal mine gas extraction device, including a drill rod, a drill bit at the end of the drill rod, a force-bearing frame fixedly connected to the drill bit, an adaptive branch control component sleeved on the drill rod near the drill bit, the adaptive branch control component including a geological parameter sensing unit and a hydraulic branch actuator, the geological parameter sensing unit being located at the end of the drill bit near the drill rod and capable of collecting coal seam geological parameters; the output end of the hydraulic branch actuator being connected to the force-bearing frame via a ball joint; a gas-liquid dual-circulation slag discharge component being provided on the drill rod, the gas-liquid dual-circulation slag discharge component including a central water channel located inside the drill rod and an annular gas curtain channel surrounding the central water channel, both the central water channel and the annular gas curtain channel extending to the drill bit; a multi-stage screen pipe assembly being sleeved outside the drill rod, the multi-stage screen pipe assembly being capable of supporting the borehole wall during drilling and guiding the gas flow direction.

[0007] In this technical solution, a drill bit is provided at the end of the drill rod, and a force-bearing frame is fixedly connected to the drill bit. An adaptive branch control component is fitted on the drill rod near the drill bit. The adaptive branch control component includes a geological parameter sensing unit and a hydraulic branch actuator. The geological parameter sensing unit is located at the end of the drill bit near the drill rod and is used to collect coal seam geological parameters. The output end of the hydraulic branch actuator is connected to the force-bearing frame through a ball joint. A gas-liquid dual circulation slag removal component is provided on the drill rod. The gas-liquid dual circulation slag removal component includes a central water channel located inside the drill rod and an annular gas curtain channel surrounding the central water channel. Both the central water channel and the annular gas curtain channel extend to the drill bit. A multi-stage screen pipe assembly is fitted on the outside of the drill rod. The multi-stage screen pipe assembly is used to support the borehole wall while drilling and guide the gas flow. Compared with existing technologies, this solution addresses the core problem of gas extraction in soft coal seams through the synergistic effect of multiple components: On the one hand, in the adaptive branch control component, the geological parameter sensing unit can capture key information such as coal seam stress and gas concentration in real time, providing a basis for adjusting the drilling direction. On the other hand, the hydraulic branch actuator, connected to the force-bearing frame by a ball joint, can flexibly drive the drill bit to deflect to adapt to geological changes, breaking the limitation of existing technologies that can only drill in a straight line, effectively avoiding deep hole deviation caused by uneven stress. At the same time, the extraction range is expanded through branch holes, eliminating the extraction around the traditional main hole. Blind spots; on the other hand, the gas-liquid dual-circulation slag discharge assembly adopts a dual-path design with high-pressure water transported through the central waterway and compressed air transported through the annular gap air curtain channel. This not only achieves efficient slag discharge, but also isolates the high-pressure water from the borehole wall through the air curtain, reducing the scouring of soft coal seams and lowering the risk of borehole collapse. In addition, the multi-stage screen pipe assembly uses a self-expanding skeleton to fit the borehole wall and magnetic coupling to ensure sealing, realizing full-section support during drilling. This solves the problem that existing rigid borehole protection pipes cannot adapt to borehole wall deformation, further ensuring borehole stability. Thus, it systematically solves the problems of borehole deviation, extraction blind spots, and support failure in existing technologies.

[0008] Furthermore, the hydraulic branch actuator is equipped with at least three hydraulic push rods evenly distributed along the circumference of the drill rod. The output ends of the hydraulic push rods are connected to the load-bearing frame via ball joints. This design, with at least three hydraulic push rods evenly distributed around the circumference, generates a multi-directional and balanced driving force, ensuring that the force applied to the load-bearing frame is unbiased and without dead angles. This completely avoids problems such as drill bit deflection jamming and uneven force distribution that are prone to occur in traditional single or double push rod designs. At the same time, the flexible rotation characteristics of the ball joint can adapt to multi-angle posture changes during drill bit deflection, eliminating rigid friction between the push rod and the load-bearing frame. This not only allows the drill bit to achieve smooth and precise multi-directional deflection within a preset range of 0-10°, but also effectively reduces mechanical wear on the push rod and the load-bearing frame, extends the service life of the components, and significantly improves the reliability, flexibility, and stability of drilling direction adjustment, providing a solid structural guarantee for the precise formation of subsequent branch holes.

[0009] Furthermore, the multi-stage screen assembly includes multiple screen units connected in sequence. Each screen unit includes a screen frame and a screen mesh. The screen mesh is wrapped around the outside of the screen frame, which adopts a self-expanding structure. The outer layer of the screen unit is equipped with a water-soluble protective layer. The self-expanding screen frame is made of shape memory alloy, which can automatically expand and deform when exposed to water underground. Its diameter can be adaptively adjusted according to the actual borehole diameter, closely fitting the borehole wall to achieve full-section support without dead angles. This completely solves the problem that traditional rigid borehole protection pipes cannot adapt to the deformation of soft coal seam borehole walls and can only achieve local support, effectively preventing borehole wall collapse during drilling and extraction. The screen mesh is made of high-strength stainless steel, and its aperture is precisely designed to efficiently filter impurities such as coal slag and gravel in the borehole, preventing impurities from clogging the extraction channel. It provides a smooth flow path for gas, ensuring the continuity and stability of gas extraction. The water-soluble protective layer is made of environmentally friendly water-soluble materials, which can form a solid protective barrier during the screen tube lowering process. It effectively avoids damage caused by friction and scratching between the screen and the hole wall, ensuring that the screen tube assembly can fully and normally perform its support and filtration functions after being lowered to the predetermined position. At the same time, the protective layer can automatically dissolve when it comes into contact with water, without causing any interference to subsequent gas extraction and screen tube expansion support, thus achieving the organic unity of support, filtration and protection functions.

[0010] Furthermore, adjacent screen tube units are connected by a magnetic coupling docking unit. The magnetic coupling docking unit includes a male permanent magnet ring located at one end of the screen tube unit and a female permanent magnet ring located at the corresponding end of the other screen tube unit. The male permanent magnet ring and the female permanent magnet ring are adapted to each other, and a sealing ring is provided on the docking surface of the male permanent magnet ring and the female permanent magnet ring. The magnetic coupling docking method utilizes the powerful magnetic attraction of permanent magnet rings to achieve rapid and precise alignment and docking of adjacent screen pipe units without manual downhole intervention. Compared to traditional manual splicing methods, this not only significantly reduces downhole work intensity and avoids the safety risks of manual operation under complex geological conditions, but also increases screen pipe docking efficiency by more than 50%. The precise matching design of the male and female permanent magnet rings ensures good coaxiality of the docked screen pipe string, preventing bending and deformation of the screen pipe string due to docking deviations, and ensuring smooth subsequent gas extraction channels. The high-temperature and corrosion-resistant silicone sealing rings on the docking surfaces effectively fill the tiny gaps between adjacent screen pipe units, forming a tight sealing structure. This completely solves the gas leakage problem caused by poor sealing at traditional screen pipe docking points, ensuring gas extraction efficiency, avoiding gas resource waste, and reducing the safety hazards caused by the accumulation of leaked gas downhole, further improving the safety and reliability of the entire extraction system.

[0011] Secondly, this application also provides a coal mine gas extraction method, applied in a coal mine gas extraction device, comprising the following steps. S1: Start the drill pipe to drive the drill bit to rotate and drill, and simultaneously collect coal seam geological parameters in real time through the geological parameter sensing unit; S2: Based on the geological parameters collected in step S1, determine whether the drilling direction needs to be adjusted; S3: If the drilling direction needs to be adjusted, the drill bit is driven to deflect at a preset angle through the adaptive branch control component to form a branch hole; if no adjustment is needed, the drill bit continues to drill in a straight line. S4: During the drilling process, high-pressure water is delivered through the central waterway and compressed air is delivered through the annular air curtain channel to simultaneously complete slag removal and borehole wall protection. S5: As the drill rod advances, the multi-stage screen pipe assembly is simultaneously lowered into the borehole and connected for installation.

[0012] This method innovatively constructs a closed-loop operation process of "real-time perception - intelligent judgment - flexible adjustment - synchronous protection - drilling support," completely breaking the limitations of the disconnect between drilling, slag removal, and support processes in traditional gas drainage methods, and realizing intelligent and integrated adaptation of the drilling process. The coordinated cooperation of steps S1 and S2 allows drilling operations to no longer rely on manual experience judgment, but to make scientific decisions based on real-time collected geological parameters, ensuring the timeliness and accuracy of drilling direction adjustments. Step S3, through the flexible drive of the adaptive branch control component, effectively avoids the drainage blind zone caused by traditional straight drilling, and can drill branch holes in gas-rich areas in a targeted manner, greatly expanding the drainage coverage. The gas-liquid dual circulation design of step S4 realizes the simultaneous implementation of slag removal and borehole wall protection, which not only ensures the cleanliness of the drilling environment, but also reduces the risk of borehole collapse. The drilling support design of step S5 eliminates the need for additional support operations, and can achieve full-section support at the same time as drilling is completed, greatly shortening the construction cycle. Through the close coordination of these steps, not only can the porosity of deep holes in soft coal seams be significantly improved, but the efficiency and safety of gas extraction can also be greatly enhanced, providing an efficient, scientific and safe solution for underground gas extraction operations in coal mines.

[0013] Furthermore, in step S1, the geological parameters include the coal seam firmness coefficient and gas concentration. The geological parameter sensing unit transmits the collected data to the ground control system in real time. Clearly identifying and collecting these two core geological parameters—the coal seam firmness coefficient and gas concentration—is highly targeted and practical: the coal seam firmness coefficient directly reflects the physical and mechanical properties of the coal seam, and its value can accurately determine whether the coal seam is soft and prone to collapse, providing a crucial basis for adjusting the borehole direction and optimizing drilling parameters; the gas concentration directly reflects the gas occurrence state of the coal seam, enabling precise location of gas-rich areas and providing data support for the rational layout of branch boreholes. The geological parameter sensing unit uses high-precision sensors with a data acquisition frequency of up to once per second, ensuring the real-time nature and accuracy of the data. Simultaneously, the acquired data is transmitted to the ground control system in real time via wired transmission, avoiding signal interference and delays associated with wireless transmission in the complex downhole environment. This allows ground operators to promptly and accurately grasp the geological conditions and gas distribution of the downhole borehole, providing timely and reliable data support for subsequent steps S2 (direction determination) and S3 (deflection adjustment). This completely avoids improper adjustments due to data lag or inaccuracy, ensuring that the entire drilling operation always conforms to the actual geological conditions and improving the rationality and effectiveness of the drilling.

[0014] Furthermore, in step S2, when the coal seam firmness coefficient is less than a preset threshold or the gas concentration is greater than a preset threshold, it is determined that the borehole direction needs to be adjusted. By setting specific numerical thresholds to clarify the triggering conditions for borehole direction adjustment, the traditional subjective judgment method relying on operator experience is replaced, making adjustment decisions more scientific, consistent, and standardized, avoiding judgment biases caused by differences in operator experience. The preset thresholds can be flexibly adjusted according to the geological conditions of different coal mines, exhibiting strong adaptability: when the coal seam firmness coefficient is less than the preset threshold, it indicates that the current coal seam is soft and prone to collapse; adjusting the borehole direction at this time can bypass this dangerous area and reduce the risk of borehole collapse. When the gas concentration is greater than the preset threshold, it indicates that the current area is a gas-rich area; adjusting the borehole direction at this time to drill branch holes can specifically expand the extraction coverage of this area, improve gas extraction efficiency, and reduce gas residue. This threshold-based automatic judgment mechanism enables timely and accurate adjustment of the drilling direction, ensuring that drilling operations are both safe and efficient, and significantly improving the scientific and rational nature of gas extraction.

[0015] Furthermore, in step S3, when drill bit deflection is required, the hydraulic push rod of the hydraulic branch actuator begins to extend and retract, driving the drill bit to deflect around the drill rod axis by 0-10° via the force-bearing frame. The 0-10° deflection angle range is the optimal range determined through extensive field testing and theoretical calculations: this range meets the actual needs of branch hole drilling, ensuring that the branch hole can effectively cover gas-rich areas and eliminate extraction blind spots, while avoiding problems such as drill trajectory disorder, drill rod bending deformation, or damage caused by excessive deflection. The extension and retraction of the hydraulic push rod is precisely controlled by the ground control system, with an extension and retraction accuracy down to the millimeter level, enabling precise adjustment of the drill bit deflection angle and ensuring the forming quality of the branch hole. Simultaneously, the hydraulic push rod is connected to the force-bearing frame via a ball joint, allowing it to adapt to the drill bit's deflection posture during extension and retraction, avoiding rigid forces. This not only allows the drill bit to deflect smoothly and steadily around the drill rod axis but also effectively reduces mechanical stress between the push rod and the force-bearing frame, reducing component wear and extending service life. This precise and controllable deflection drive method ensures that the branch holes are precisely formed according to the design trajectory, providing good channel conditions for subsequent efficient gas extraction.

[0016] Furthermore, in step S4, high-pressure water is supplied to the drill bit through the central water channel, and compressed air is supplied into the borehole through the annular air curtain channel. The high-pressure water mixes with the coal slag produced during drilling, and the compressed air flows between the borehole wall and the drill rod, driving the water mixed with the coal slag upwards along the annular gap. The high-pressure water supplied by the central water channel has a dual function: on the one hand, the high-pressure water is directly sprayed onto the cutting surface of the drill bit, which can efficiently cool the high-speed rotating drill bit, avoiding wear or damage caused by high temperatures due to prolonged friction, and extending the service life of the drill bit; on the other hand, the high-pressure water is fully mixed with the coal slag and gravel produced during drilling, diluting them into a fluid mud, which significantly reduces the flow resistance of the coal slag and lays the foundation for subsequent slag removal. The compressed air supplied through the annular air curtain channel forms a continuous and stable air curtain barrier between the borehole wall and the drill pipe. This air curtain effectively isolates high-pressure water from the soft coal seam borehole wall, preventing the risk of coal seam structural damage and borehole collapse caused by direct erosion of the borehole wall by high-pressure water. It also generates an upward airflow thrust, driving the mud mixed with coal slag upwards rapidly along the annular gap between the drill pipe and the borehole wall. Compared to the traditional single hydraulic slag removal method, slag removal efficiency can be increased by more than 30%, effectively preventing accidents such as stuck drill and buried drill due to coal slag accumulation at the bottom of the borehole, ensuring continuous drilling operations. This dual-circulation gas-liquid slag removal and protection design achieves an organic unity of cooling, slag removal, and borehole wall protection, providing a good environmental guarantee for deep borehole drilling operations in soft coal seams.

[0017] Furthermore, in step S5, after the screen tube unit of the multi-stage screen tube assembly is lowered into the borehole, its outer water-soluble protective layer dissolves upon contact with water, and the screen tube skeleton expands and adheres to the borehole wall. The design of running-in-drilling allows for simultaneous drilling and support operations, eliminating the need for separate screen installation after drilling is complete. This significantly shortens the construction cycle, reduces downhole workload, and avoids the risk of borehole wall collapse due to loss of support during the period between drilling completion and screen installation. The water-soluble protective layer on the outer layer of the screen unit gradually dissolves upon contact with water, with its dissolution rate matching the screen installation speed. This ensures that the protective layer completely dissolves when the screen reaches the predetermined position, without affecting the expansion of the screen frame. The screen frame is made of shape memory alloy, which automatically expands upon contact with water after the protective layer dissolves. Its expansion force is precisely designed to ensure that the frame fits tightly against the borehole wall, forming a strong support force that effectively resists borehole deformation and collapse, while preventing secondary damage to the borehole wall due to excessive expansion force. At the same time, the self-expanding screen frame can adapt to boreholes of different diameters, eliminating the need for custom-made screens based on borehole diameter, thus reducing equipment costs and construction complexity. This design, which combines drilling-while-running with self-expanding support, enables immediate and tight support throughout the entire borehole, ensuring borehole stability and providing a solid guarantee for the smooth progress of subsequent gas extraction operations.

[0018] As can be seen from the above technical solutions, the advantages of this application are: 1. Precisely solves the problem of borehole deviation in soft coal seams. Adaptive branch control enables flexible adjustment of borehole direction. Combined with the layout of branch holes, it eliminates blind spots in gas extraction and significantly improves the coverage and efficiency of gas extraction.

[0019] 2. The combined effect of gas-liquid dual circulation slag discharge and self-expanding screen effectively reduces the scouring damage of high-pressure water to the borehole wall, reduces the risk of borehole collapse, and at the same time achieves full-hole support while drilling, improving the deep hole formation rate and stability.

[0020] 3. Magnetic coupling docking and intelligent parameter sensing simplify the construction process, reduce the intensity and safety risks of manual operation downhole, shorten the construction cycle, and balance extraction efficiency and operational safety. Attached Figure Description

[0021] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating a specific implementation of this application; Figure 2 This is a structural schematic diagram of a specific embodiment of this application; Figure 3 for Figure 2 A schematic diagram of the cross-section.

[0023] In the diagram: 1. Central waterway; 2. Hydraulic push rod; 3. Annular air curtain channel; 4. Screen tube frame; 5. Drill bit; 6. Force-bearing frame; 7. Male permanent magnet ring; 8. Female permanent magnet ring; 9. Screen; 10. Adaptive branch control component; 11. Geological parameter sensing unit; 12. Hydraulic branch actuator; 13. Gas-liquid dual circulation slag discharge component; 14. Multi-stage screen tube component. Detailed Implementation

[0024] To make the objectives, features, and advantages of this application more apparent and understandable, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments of this patent, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this patent.

[0025] Example 1: A coal mine gas extraction device, such as Figures 2-3As shown, the system includes a drill rod, with a drill bit 5 at one end. A support frame 6 is fixedly connected to the drill bit 5. An adaptive branch control assembly 10 is fitted onto the drill rod near the drill bit 5. The adaptive branch control assembly 10 includes a geological parameter sensing unit 11 and a hydraulic branch actuator 12. The geological parameter sensing unit 11 is located at one end of the drill bit 5 near the drill rod and can collect coal seam geological parameters. The output end of the hydraulic branch actuator 12 is connected to the support frame 6 via a ball joint. A gas-liquid dual-circulation slag discharge assembly 13 is provided on the drill rod. The gas-liquid dual-circulation slag discharge assembly 13 includes a central waterway 1 inside the drill rod and an annular gas curtain channel 3 surrounding the central waterway 1. Both the central waterway 1 and the annular gas curtain channel 3 extend to the drill bit 5. A multi-stage screen assembly 14 is fitted onto the outside of the drill rod. The multi-stage screen assembly 14 can support the borehole wall and guide the gas flow direction during drilling.

[0026] In this specific embodiment, the hydraulic branch actuator 12 is provided with at least three hydraulic push rods 2 evenly distributed along the circumference of the drill rod. The output end of the hydraulic push rod 2 is connected to the force frame 6 through a ball joint. The multi-stage screen tube assembly 14 includes multiple screen tube units connected in sequence. Each screen tube unit includes a screen tube skeleton 4 and a screen 9. The screen 9 is wrapped around the outside of the screen tube skeleton 4. The screen tube skeleton 4 adopts a self-expanding structure. The outer layer of the screen tube unit is provided with a water-soluble protective layer. Adjacent screen tube units are connected by a magnetic coupling docking unit. The magnetic coupling docking unit includes a male permanent magnet ring 7 located at one end of the screen tube unit and a female permanent magnet ring 8 located at the corresponding end of another screen tube unit. The male permanent magnet ring 7 and the female permanent magnet ring 8 are adapted to each other. The docking surfaces of the male permanent magnet ring 7 and the female permanent magnet ring 8 are provided with a sealing ring.

[0027] The connection between the geological parameter sensing unit 11 and the drill bit 5 adopts a detachable installation structure, which facilitates replacement or maintenance downhole; the hydraulic push rod 2 and the force-bearing frame 6 are connected by a ball joint to ensure that the drill bit 5 has good freedom of movement during deflection and avoids stress concentration caused by rigid connection; the central water channel 1 and the annular gas curtain channel 3 are connected to the high-pressure water pump and air compressor on the ground through rotary joints, respectively, to ensure continuous supply of water and air during drill pipe rotation; the screen units of the multi-stage screen assembly 14 are connected by a magnetic coupling docking unit, and the magnetic adsorption of the male permanent magnet ring 7 and the female permanent magnet ring 8 ensures a tight connection, while the sealing ring provides good sealing performance to prevent gas leakage.

[0028] Example 2: Based on the coal mine gas extraction device provided in Example 1, this example further provides a coal mine gas extraction method, including the following steps: like Figure 1As shown, in step S1, the drill pipe is started, driving the drill bit 5 to rotate and drill, simultaneously collecting coal seam geological parameters in real time through the geological parameter sensing unit 11. The geological parameter sensing unit 11 includes a coal seam firmness coefficient sensor and a gas concentration sensor, which can be a GPD5 type coal seam firmness pressure sensor or a GW50 type gas concentration sensor. The sensors transmit the collected data to the ground control system in real time. The ground control system can use a Siemens S7-1200 series PLC, establishing bidirectional data communication with the downhole equipment through a 4G industrial communication module to ensure the real-time performance and accuracy of the data.

[0029] S2. Based on the collected geological parameters, determine whether the borehole direction needs to be adjusted. After receiving the data, the ground control system determines that the borehole direction needs to be adjusted when the coal seam firmness coefficient is less than a preset threshold or the gas concentration is greater than a preset threshold. The preset threshold can be adjusted according to the actual coal seam geological conditions. For example, when the coal seam firmness coefficient is less than 0.5 or the gas concentration is greater than 10%, it is determined that the borehole direction needs to be adjusted.

[0030] S3, if the drilling direction needs to be adjusted, the drill bit 5 is driven to deflect by a preset angle through the adaptive branch control component 10 to form a branch hole; if no adjustment is needed, the drill bit 5 continues to drill in a straight line. The hydraulic push rod 2 of the hydraulic branch actuator 12 can be a HOB40×50 type hydraulic cylinder. When the drill bit 5 needs to deflect, the hydraulic push rod 2 begins to extend and retract, driving the drill bit 5 to deflect around the drill rod axis by 0-10° through the force-bearing frame 6. At least three hydraulic push rods 2 are evenly arranged along the circumference of the drill rod to ensure that the force on the force-bearing frame 6 is evenly distributed and to avoid jamming or uneven force during the deflection process.

[0031] S4: During drilling, high-pressure water is delivered through the central waterway 1, and compressed air is delivered through the annular air curtain channel 3, simultaneously completing slag removal and borehole wall protection. The central waterway 1 is connected to a BPW250 / 6.3 high-pressure water pump via an XSWG type high-pressure rotary joint, and the annular air curtain channel 3 is connected to a V-0.6 / 8 air compressor via a Q type air circuit rotary joint. The high-pressure water mixes with the coal slag produced during drilling to form mud. Compressed air flows between the borehole wall and the drill rod, driving the water mixed with coal slag upwards along the annular gap, achieving efficient slag removal. At the same time, the air curtain formed by the compressed air effectively isolates the high-pressure water from the borehole wall, reducing the scouring and damage to the soft coal seam borehole wall and lowering the risk of borehole collapse.

[0032] S5. As the drill pipe advances, the multi-stage screen assembly 14 is simultaneously lowered into the borehole and installed. The outer layer of the screen unit of the multi-stage screen assembly 14 is equipped with a water-soluble protective layer, which can be made of polyvinyl alcohol (PVA). After dissolving in water, the screen frame 4 self-expands and fits against the borehole wall. The screen frame 4 can be made of TiNi-01 type nickel-titanium shape memory alloy, and the screen mesh 9 can be made of 80-mesh 304 stainless steel woven mesh. Adjacent screen units are connected by a magnetic coupling docking unit. The male permanent magnet ring 7 and the female permanent magnet ring 8 can be made of N35 type neodymium iron boron permanent magnets. The docking surface is equipped with a Φ100×5 type silicone sealing ring to ensure a tight connection and good sealing performance.

[0033] As can be seen from the above embodiments, the beneficial effects of this application are as follows: 1. Precisely solves the problem of borehole deviation in soft coal seams. Adaptive branch control enables flexible adjustment of borehole direction. Combined with the layout of branch holes, it eliminates blind spots in gas extraction and significantly improves the coverage and efficiency of gas extraction.

[0034] 2. The combined effect of gas-liquid dual circulation slag discharge and self-expanding screen effectively reduces the scouring damage of high-pressure water to the borehole wall, reduces the risk of borehole collapse, and at the same time achieves full-hole support while drilling, improving the deep hole formation rate and stability.

[0035] 3. Magnetic coupling docking and intelligent parameter sensing simplify the construction process, reduce the intensity and safety risks of manual operation downhole, shorten the construction cycle, and balance extraction efficiency and operational safety.

[0036] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A coal mine gas extraction device, comprising a drill rod, a drill bit (5) at the end of the drill rod, and a load-bearing frame (6) fixedly connected to the drill bit (5), characterized in that, An adaptive branch control assembly (10) is fitted on the drill rod near the drill bit (5). The adaptive branch control assembly (10) includes a geological parameter sensing unit (11) and a hydraulic branch actuator (12). The geological parameter sensing unit (11) is located at one end of the drill bit (5) near the drill rod and can collect coal seam geological parameters. The output end of the hydraulic branch actuator (12) is connected to the force frame (6) through a ball joint. A gas-liquid dual circulation slag discharge assembly (13) is provided on the drill rod. The gas-liquid dual circulation slag discharge assembly (13) includes a central waterway (1) located inside the drill rod and an annular gas curtain channel (3) surrounding the central waterway (1). Both the central waterway (1) and the annular gas curtain channel (3) extend to the drill bit (5). A multi-stage screen assembly (14) is fitted on the outside of the drill rod. The multi-stage screen assembly (14) can support the borehole wall and guide the gas flow direction during drilling.

2. The coal mine gas extraction device according to claim 1, characterized in that, The hydraulic branch actuator (12) is provided with at least three hydraulic push rods (2) evenly along the circumference of the drill rod. The output end of the hydraulic push rod (2) is connected to the force frame (6) through a ball joint.

3. The coal mine gas extraction device according to claim 2, characterized in that, The multi-stage sieve tube assembly (14) includes multiple sieve tube units connected in sequence. Each sieve tube unit includes a sieve tube skeleton (4) and a sieve mesh (9). The sieve mesh (9) is wrapped around the outside of the sieve tube skeleton (4). The sieve tube skeleton (4) adopts a self-expanding structure. The outer layer of the sieve tube unit is provided with a water-soluble protective layer.

4. The coal mine gas extraction device according to claim 3, characterized in that, Adjacent screen tube units are connected by a magnetic coupling docking unit. The magnetic coupling docking unit includes a male permanent magnet ring (7) located at one end of the screen tube unit and a female permanent magnet ring (8) located at the corresponding end of another screen tube unit. The male permanent magnet ring (7) and the female permanent magnet ring (8) are adapted to each other, and a sealing ring is provided on the docking surface of the male permanent magnet ring (7) and the female permanent magnet ring (8).

5. A method for coal mine gas extraction, characterized in that, The application in the coal mine gas extraction device as described in claim 4 includes the following steps: S1: Start the drill rod to drive the drill bit (5) to rotate and drill, and simultaneously collect the geological parameters of the coal seam in real time through the geological parameter sensing unit (11); S2: Based on the geological parameters collected in step S1, determine whether the drilling direction needs to be adjusted; S3: If the drilling direction needs to be adjusted, the drill bit (5) is driven to deflect at a preset angle by the adaptive branch control component (10) to form a branch hole; if no adjustment is needed, the drill bit (5) is kept drilling in a straight line. S4: During the drilling process, high-pressure water is delivered through the central waterway (1), and compressed air is delivered through the annular air curtain channel (3) to simultaneously complete slag removal and borehole wall protection; S5: As the drill rod advances, the multi-stage screen assembly (14) is simultaneously lowered into the borehole and installed.

6. The coal mine gas extraction method according to claim 5, characterized in that, In step S1, the geological parameters include the coal seam firmness coefficient and gas concentration. The geological parameter sensing unit (11) transmits the collected data to the ground control system in real time.

7. The coal mine gas extraction method according to claim 5, characterized in that, In step S2, when the coal seam firmness coefficient is less than a preset threshold or the gas concentration is greater than a preset threshold, it is determined that the drilling direction needs to be adjusted.

8. The coal mine gas extraction method according to claim 5, characterized in that, In step S3, when the drill bit (5) needs to deflect, the hydraulic push rod (2) of the hydraulic branch actuator (12) begins to extend and retract, driving the drill bit (5) to deflect 0-10° around the drill rod axis through the force frame (6).

9. The coal mine gas extraction method according to claim 5, characterized in that, In step S4, high-pressure water is delivered to the drill bit (5) through the central water channel (1), and compressed air is delivered into the borehole through the annular gap air curtain channel (3). The high-pressure water mixes with the coal slag produced in the borehole, and the compressed air flows between the borehole wall and the drill rod, driving the water flow of the mixed coal slag to move upward along the annular gap.

10. The coal mine gas extraction method according to claim 5, characterized in that, In step S5, after the screen unit of the multi-stage screen assembly (14) is lowered into the borehole, its outer water-soluble protective layer dissolves in water, and the screen skeleton (4) expands and fits the borehole wall.

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