Directional Drilling System and Method for Complex Underground Formations in Coal Mines (Gas-Liquid Dual Circulation)

Abstract

This invention discloses a gas-liquid dual-circulation directional drilling system and method for complex formations in coal mines. It includes a directional drill bit, a double-walled hollow hydraulically driven screw drill bit, a three-channel instrument outer tube, a three-channel drill rod, and a three-channel water jet connected sequentially. The front end of the double-walled hollow hydraulically driven screw drill bit is connected to the directional drill bit. The central channel of the double-walled hollow hydraulically driven screw drill bit is a high-pressure air or nitrogen channel, connected to the air hole of the directional drill bit. The annular channel between the stator and rotor is a high-pressure water inlet channel, and the annular channel between the stator rod and the screw drill bit outer tube is a high-pressure water outlet channel. The central channel of the three-channel instrument outer tube, the three-channel drill rod, and the three-channel water jet is a high-pressure air or nitrogen inlet channel, the middle annular channel is a high-pressure water inlet channel, and the outer annular channel is a high-pressure water outlet channel. This invention has significant advantages such as high hydraulic directional drilling torque, high rock drilling efficiency, and improved hole-forming capacity in complex and fractured formations due to air slag removal. It also enables the recycling of water used in directional drilling, saving water resources.

Description

Technical Field

[0001] This invention belongs to the technical field of coal mine drilling, and relates to a method for directional drilling in complex formations, specifically a gas-liquid dual-circulation directional drilling system and directional drilling process for complex formations. Background Technology

[0002] Near-horizontal directional drilling technology in coal mines has been widely applied in drilling operations for gas control, water hazard prevention, and detection of hidden disaster-causing factors in coal mines due to its advantages such as controllable borehole trajectory, high construction precision, and large single-hole coverage, achieving significant application results. Currently, directional drilling processes in coal mines mainly include hydraulic directional drilling and pneumatic directional drilling. Hydraulic directional drilling uses high-pressure water to drive a screw drill bit, offering the advantage of high output torque. It is suitable for rock formations with a hardness coefficient less than 10 and hard coal seams with a hardness coefficient greater than 0.8. However, for complex geological conditions, such as unstable strata like mudstone and sandy mudstone, geological structures like faults, folds, and collapse columns, and soft, fractured coal seams, the borehole wall is prone to instability and severe collapse under the scouring effect of high-pressure water during drilling, making borehole formation difficult. Therefore, it is not suitable for drilling in these complex geological conditions. Furthermore, hydraulic directional drilling requires a large amount of water, generally not less than 20 cubic meters per second. 3 The drilling water used is not recycled, resulting in serious water waste. This drilling technology is unsuitable for coal mines in areas with severe water shortages. Pneumatic directional drilling uses high-pressure gas to drive a screw drill. Because gas is used as the slag removal medium, gas slag removal has the advantage of minimal disturbance to the borehole wall. This technology has good hole-forming ability under complex geological conditions and is currently mainly suitable for soft, fractured coal seams with a hardness coefficient of 0.3-0.8. However, due to the compressibility of gas itself and the low output gas pressure of air compressors and nitrogen generators in coal mines, the output torque of the pneumatic screw drill is low. This technology is not suitable for rock drilling. When encountering the top or bottom plate of the coal seam or interbedded rock, the drilling efficiency is extremely low, and in severe cases, drilling becomes impossible, resulting in low drilling efficiency and, in severe cases, failure to achieve the designed hole depth. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a gas-liquid dual-circulation directional drilling system and method for complex formations in coal mines. This system solves the problems in existing technologies, such as severe hole collapse and difficulty in hole formation in hydraulic directional drilling under complex formation conditions, high water supply requirements and lack of recycling in hydraulic directional drilling, and extremely low drilling efficiency or even difficulty in drilling through rock formations in pneumatic directional drilling.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A gas-liquid dual-circulation directional drilling system for complex formations in coal mines includes a directional drill bit, a double-walled hollow hydraulically driven screw drill bit, a three-channel instrument outer tube, a three-channel drill rod, and a three-channel water jet connected in sequence.

[0006] The double-walled hollow hydraulically driven screw drill includes a hollow rotor, a universal joint, and a drive shaft connected in sequence, and also includes a stator sleeved outside the rotor, a stator rod body disposed outside the stator, and a screw drill outer tube sleeved outside the stator rod body; the three-channel instrument outer tube includes an inner tube, a middle tube, and an outer tube sleeved in sequence from the inside to the outside; the three-channel drill rod includes a drill rod inner tube, a drill rod middle tube, and a drill rod outer tube sleeved in sequence from the inside to the outside; the three-channel water pipe includes a water pipe inner tube, a water pipe middle tube, and a water pipe outer tube sleeved in sequence from the inside to the outside;

[0007] The drive shaft, universal joint, rotor, inner tube, drill rod inner tube, and water supply inner tube are connected sequentially from front to back to form a central channel. The front end of the central channel is connected to the air hole of the directional drill bit, and the rear end of the central channel is a high-pressure hose connector for connection to an air compressor or nitrogen generator. The stator and stator rod body, intermediate tube, drill rod intermediate tube, and water supply intermediate tube are connected sequentially to form an intermediate annular channel. The front end of the intermediate annular channel is sealed by a seal, and the rear end of the intermediate annular channel is connected to the high-pressure hose connector for connection to a mud pump. The screw drill outer tube, outer tube, drill rod outer tube, and water supply outer tube are connected sequentially to form an outer annular channel. The front end of the outer annular channel is sealed and connected to the intermediate annular channel through a water hole on the front side wall of the stator rod body. The rear end of the outer annular channel is connected to the high-pressure hose connector for connection to a water tank.

[0008] The present invention also includes the following technical features:

[0009] Specifically, the rear end of the rotor is a male connector that is inserted into the front end of the inner tube female connector, the rear end of the stator rod is a female connector that is inserted into the front end of the intermediate tube male connector, and the rear end of the screw drill tool outer tube is a female thread that is threadedly connected to the front end of the outer tube male thread.

[0010] Specifically, the rear end of the inner tube is a male connector that is inserted into the front end of the drill pipe inner tube female connector, the rear end of the middle tube is a female connector that is inserted into the front end of the drill pipe middle tube male connector, and the rear end of the outer tube is a female thread that is threadedly connected to the front end of the drill pipe outer tube male thread.

[0011] Specifically, the rear end of the drill pipe inner tube is a male connector that is inserted into the front end of the water pipe inner tube, the rear end of the drill pipe middle tube is a female connector that is inserted into the front end of the water pipe middle tube, and the rear end of the drill pipe outer tube is a female thread that is threadedly connected to the front end of the water pipe outer tube.

[0012] Specifically, a sealing ring is provided between the outer rear wall of the inner water pipe and the annular boss on the inner rear wall of the middle water pipe; a sealing ring is provided between the outer rear wall of the middle water pipe and the annular boss on the inner rear wall of the outer water pipe; bearing assemblies are installed between the inner water pipe and the middle water pipe, and between the middle water pipe and the outer water pipe, so that the inner water pipe, the middle water pipe and the outer water pipe can rotate independently of each other.

[0013] Specifically, the inner wall of the toilet's inner pipe has a connecting hole that connects the intermediate annular channel to the high-pressure hose connector; the middle pipe of the toilet also has a connecting hole that connects the outer annular channel to the high-pressure hose connector.

[0014] Specifically, the central channel corresponding to the three-channel instrument outer tube is equipped with a drilling measurement instrument component.

[0015] Specifically, the central channel is a compressed air or nitrogen inlet channel, the intermediate annular channel is a high-pressure water inlet channel, and the outer annular channel is a high-pressure water outlet channel. The high-pressure water enters through the intermediate annular channel, driving the rotor of the double-walled hollow hydraulic screw drill to rotate and drive the directional drill bit to rotate and break rocks for drilling. It then exits through the outer annular channel and enters the water tank. The compressed air or nitrogen enters through the central channel to the air hole of the directional drill bit, cooling the directional drill bit and carrying drill cuttings. It then exits through the directional drill and the annular channel of the borehole wall.

[0016] Specifically, the high-pressure water enters through the intermediate annular channel to drive the rotor of the double-walled hollow hydraulic screw drill bit to rotate, then exits through the outer annular channel into the water tank, and is then sucked into the intermediate annular channel by the mud pump, thus realizing the recycling of high-pressure water.

[0017] The method for directional drilling using the gas-liquid dual-circulation directional drilling system for complex underground coal mine formations includes the following steps:

[0018] Step 1: Connect the directional drill bit, double-walled hollow hydraulic screw drill bit, three-channel instrument outer tube, three-channel drill rod, and three-channel water pipe in sequence;

[0019] Step 2: The central channel of the three-channel water toilet is connected to the air compressor or nitrogen generator through a high-pressure hose; the middle annular channel of the three-channel water toilet is connected to the mud pump through a high-pressure hose; and the outer annular channel of the three-channel water toilet is connected to the water tank through a high-pressure hose.

[0020] Step 3: Start the mud pump, air compressor or nitrogen generator to supply high-pressure water and high-pressure air or nitrogen into the directional drilling tool. The high-pressure air or nitrogen returns out of the hole from the annular channel between the directional drilling tool and the hole wall, and the high-pressure water returns to the water tank from the outer annular channel. The high-pressure water is recycled.

[0021] Step 4: Start the directional drilling rig, rotate the directional drilling tool to adjust the tool face angle, and use the directional drilling rig to push the directional drilling tool forward, which in turn drives the directional drill bit forward. The double-walled hollow hydraulically driven screw drill tool drives the directional drill bit to rotate and break the rock, thus achieving sliding directional drilling.

[0022] Step 5: When the three-channel drill pipe of the directional drilling rig has finished drilling, turn off the mud pump, turn off the air compressor or nitrogen generator, disconnect the three-channel water pipe, use the drilling measurement instrument to measure the borehole trajectory, reconnect the three-channel drill pipe, and then reconnect the three-channel water pipe.

[0023] Step 6: Repeat steps 3, 4 and 5 to complete the directional drilling.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] This invention employs a dual-circulation gas-liquid system. On one hand, high-pressure water drives a screw drill bit to rotate and break rock, fully utilizing the high output torque of the hydraulic screw drill bit to meet the needs of efficient directional drilling in rock formations. On the other hand, high-pressure gas is used for slag removal, fully utilizing the advantage of gas's minimal disturbance to the borehole wall, meeting the drilling needs of unstable strata such as soft coal seams, mudstone, and sandy mudstone, as well as unstable geological structures such as faults and collapse columns. Simultaneously, this invention achieves the recycling of high-pressure water during directional drilling, conserving water resources and making it suitable for underground drilling in coal mines where water resources are extremely scarce. In summary, the system method of this invention can solve the technical problems of borehole collapse in unstable strata under complex geological conditions and the extremely low drilling efficiency of pneumatic directional drilling in rock formations, greatly expanding the applicable geological conditions range of directional drilling technology. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the gas-liquid dual-circulation directional drilling system for complex underground coal mine formations according to the present invention;

[0027] Figure 2 This is a schematic diagram of the double-walled hollow hydraulically driven screw drill tool structure of the present invention;

[0028] Figure 3 This is a schematic diagram of the three-channel instrument outer tube structure of the present invention;

[0029] Figure 4 This is a schematic diagram of the three-channel drill pipe structure of the present invention;

[0030] Figure 5 This is a schematic diagram of the three-channel water-filled toilet structure of the present invention.

[0031] The meanings of the labels in the diagram are as follows:

[0032] 1. Directional drill bit, 2. Double-walled hollow hydraulically driven screw drill bit, 3. Three-channel instrument outer tube, 4. Three-channel drill pipe, 5. Three-channel water pipe, 6. Air compressor or nitrogen generator, 7. Mud pump, 8. Water tank, 9. High-pressure hose;

[0033] 2-1. Drive shaft, 2-2. Seal, 2-3. Universal joint, 2-4. Water eye, 2-5. Rotor, 2-6. Stator, 2-7. Stator rod body, 2-8. Outer tube of screw drill bit;

[0034] 3-1. Inner tube; 3-2. Intermediate tube; 3-3. Outer tube; 3-4. Measuring instrument assembly;

[0035] 4-1. Drill pipe inner tube; 4-2. Drill pipe intermediate tube; 4-3. Drill pipe outer tube;

[0036] 5-1. Inner pipe of toilet; 5-2. Middle pipe of toilet; 5-3. Outer pipe of toilet; 5-4. High-pressure hose connector;

[0037] 10. Central passage, 20. Intermediate ring passage, 30. Outer ring passage. Detailed Implementation

[0038] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0039] Example 1:

[0040] like Figures 1 to 5 As shown, this embodiment provides a gas-liquid dual-circulation directional drilling system for complex underground coal mine formations, including a directional drill bit 1, a double-walled hollow hydraulically driven screw drill bit 2, a three-channel instrument outer tube 3, a three-channel drill rod 4, and a three-channel water jet 5 connected in sequence.

[0041] The double-walled hollow hydraulically driven screw drill 2 includes a hollow rotor 2-5, a universal joint 2-3, and a drive shaft 2-1 connected in sequence, and also includes a stator 2-6 sleeved outside the rotor 2-5, a stator rod body 2-7 disposed outside the stator 2-6, and a screw drill outer tube 2-8 sleeved outside the stator rod body 2-7; the three-channel instrument outer tube 3 includes an inner tube 3-1, a middle tube 3-2, and an outer tube 3-3 sleeved in sequence from the inside to the outside; the three-channel drill rod 4 includes a drill rod inner tube 4-1, a drill rod middle tube 4-2, and a drill rod outer tube 4-3 sleeved in sequence from the inside to the outside; the three-channel water pipe 5 includes a water pipe inner tube 5-1, a water pipe middle tube 5-2, and a water pipe outer tube 5-3 sleeved in sequence from the inside to the outside.

[0042] The drive shaft 2-1, universal joint 2-3, rotor 2-5, inner tube 3-1, drill rod inner tube 4-1, and water pipe inner tube 5-1 are connected sequentially from front to back to form a central channel 10. The front end of the central channel 10 is connected to the air vent of the directional drill bit 1, and the rear end of the central channel 10 is a high-pressure hose connector 5-4 for connection to the air compressor or nitrogen generator 6. The stator 2-6, stator rod 2-7, intermediate tube 3-2, drill rod intermediate tube 4-2, and water pipe intermediate tube 5-2 are connected sequentially to form an intermediate annular channel 20. The front end of the intermediate annular channel 20 is sealed by the seal 2-2. The rear end of the intermediate annular channel 20 is connected to the high-pressure hose connector 5-4 to connect to the mud pump 7. The screw drill outer tube 2-8, outer tube 3-3, drill rod outer tube 4-3 and water pipe 5-3 are connected in sequence to form the outer annular channel 30. The front end of the outer annular channel 30 is sealed and connected to the intermediate annular channel 20 through the water eye 2-4 on the front side wall of the stator rod 2-7. The rear end of the outer annular channel 30 is connected to the high-pressure hose connector 5-4 to connect to the water tank 8.

[0043] The rear end of rotor 2-5 is a male connector that is inserted into the front end of inner tube 3-1. The rear end of stator rod 2-7 is a female connector that is inserted into the front end of intermediate tube 3-2. The rear end of screw drill tool outer tube 2-8 is a female thread that is threadedly connected to the front end of outer tube 3-3 by thread.

[0044] The rear end of the inner tube 3-1 is a male connector and is inserted into the front end of the female connector of the drill pipe inner tube 4-1. The rear end of the middle tube 3-2 is a female connector and is inserted into the front end of the drill pipe middle tube 4-2 male connector. The rear end of the outer tube 3-3 is a female thread and is connected to the front end of the drill pipe outer tube 4-3 male thread by thread.

[0045] The rear end of the drill pipe inner tube 4-1 is a male connector, which is inserted into the front end of the water pipe inner tube 5-1 female connector. The rear end of the drill pipe middle tube 4-2 is a female connector, which is inserted into the front end of the water pipe middle tube 5-2 male connector. The rear end of the drill pipe outer tube 4-3 is a female thread, which is connected to the front end of the water pipe outer tube 5-3 male thread by thread.

[0046] A sealing ring is provided between the rear outer wall of the inner water pipe 5-1 and the annular boss on the rear inner wall of the intermediate water pipe 5-2; a sealing ring is also provided between the rear outer wall of the intermediate water pipe 5-2 and the annular boss on the rear inner wall of the outer water pipe 5-3. Bearing assemblies are installed between the inner water pipe 5-1 and the intermediate water pipe 5-2, and between the intermediate water pipe 5-2 and the outer water pipe 5-3, allowing the inner water pipe 5-1, the intermediate water pipe 5-2, and the outer water pipe 5-3 to rotate independently of each other.

[0047] The inner wall of the water pipe 5-1 has a connecting hole that connects the intermediate annular channel 20 to the high-pressure hose connector 5-4; the inner wall of the middle water pipe 5-2 has a connecting hole that connects the outer annular channel 30 to the high-pressure hose connector 5-4.

[0048] The central channel 10 corresponding to the three-channel instrument outer tube 3 is equipped with a drilling measurement instrument assembly 3-4.

[0049] The central passage 10 and the intermediate annular passage 20 have single-action functions.

[0050] Seals 2-2 are provided at both the front and rear of the drive shaft 2-1.

[0051] The central channel 10 is the inlet channel for compressed air or nitrogen, the intermediate annular channel 20 is the inlet channel for high-pressure water, and the outer annular channel 30 is the outlet channel for high-pressure water. High-pressure water enters through the intermediate annular channel 20 to drive the rotor 2-5 of the double-walled hollow hydraulic screw drill 2 to rotate, which in turn drives the directional drill bit 1 to rotate and break rocks for drilling. Then, it exits through the outer annular channel and enters the water tank 8. Compressed air or nitrogen enters through the central channel 10 to the air hole of the directional drill bit 1 to cool the directional drill bit 1 and carry the drill cuttings. Then, it exits through the annular channel of the directional drill bit and the borehole wall.

[0052] High-pressure water enters through the intermediate annular channel 20 to drive the rotor 2-5 of the double-walled hollow hydraulic screw drill 2 to rotate, then exits through the outer annular channel 30 into the water tank 8, and is then sucked into the intermediate annular channel 20 by the mud pump 7, thus realizing the recycling of high-pressure water.

[0053] Example 2:

[0054] This embodiment provides a method for directional drilling in a gas-liquid dual-circulation directional drilling system for complex formations in coal mines. During directional drilling, high-pressure water generated by the mud pump enters the double-walled hollow hydraulically driven screw drill bit through the intermediate annular channel, driving the rotor to rotate and causing the directional drill bit to rotate and break rock. The high-pressure water then returns through the outer annular channel, passes through a high-pressure hose connected to the three water channels, and enters the water tank. The mud pump then pressurizes the water again and returns it to the intermediate annular channel, thus achieving the recycling of high-pressure water. High-pressure air or nitrogen generated by an air compressor or nitrogen generator enters the bottom of the hole through the central channel to the vent of the directional drill bit, cooling the drill bit. Simultaneously, the drill cuttings generated by the directional drill bit are discharged from the hole through the annular channel between the directional drill bit and the hole wall. This ultimately forms a gas-liquid dual-circulation directional drilling process where high-pressure water drives the double-walled hollow hydraulically driven screw drill bit to rotate and break rock, while high-pressure air or nitrogen is used for cuttings removal. This method has significant advantages such as high hydraulic directional drilling torque, high rock drilling efficiency, and air slag removal that can improve the hole-forming ability in complex and fractured formations. At the same time, this method realizes the recycling of water used in directional drilling, thus saving water resources.

[0055] Specifically, the following steps are included:

[0056] Step 1: Connect the directional drill bit, double-walled hollow hydraulic screw drill bit, three-channel instrument outer tube, three-channel drill rod, and three-channel water pipe in sequence;

[0057] Step 2: The central channel of the three-channel water toilet is connected to the air compressor or nitrogen generator through a high-pressure hose; the middle annular channel of the three-channel water toilet is connected to the mud pump through a high-pressure hose; and the outer annular channel of the three-channel water toilet is connected to the water tank through a high-pressure hose.

[0058] Step 3: Start the mud pump, air compressor or nitrogen generator to supply high-pressure water and high-pressure air or nitrogen into the directional drilling tool. The high-pressure air or nitrogen returns out of the hole from the annular channel between the directional drilling tool and the hole wall, and the high-pressure water returns to the water tank from the outer annular channel. The high-pressure water is recycled.

[0059] Step 4: Start the directional drilling rig, rotate the directional drilling tool to adjust the tool face angle, and use the directional drilling rig to push the directional drilling tool forward, which in turn drives the directional drill bit forward. The double-walled hollow hydraulically driven screw drill tool drives the directional drill bit to rotate and break the rock, thus achieving sliding directional drilling.

[0060] Step 5: When the three-channel drill pipe of the directional drilling rig has finished drilling, turn off the mud pump, turn off the air compressor or nitrogen generator, disconnect the three-channel water pipe, use the drilling measurement instrument to measure the borehole trajectory, reconnect the three-channel drill pipe, and then reconnect the three-channel water pipe.

[0061] Step 6: Repeat steps 3, 4 and 5 to complete the directional drilling.

[0062] This invention employs a dual-circulation gas-liquid system. On one hand, high-pressure water drives a screw drill bit to rotate and break rock, fully utilizing the high output torque of the hydraulic screw drill bit to meet the needs of efficient directional drilling in rock formations. On the other hand, high-pressure gas is used for slag removal, fully utilizing the advantage of gas's minimal disturbance to the borehole wall, meeting the drilling needs of unstable strata such as soft coal seams, mudstone, and sandy mudstone, as well as unstable geological structures such as faults and collapse columns. Simultaneously, this invention achieves the recycling of high-pressure water during directional drilling, conserving water resources and making it suitable for underground drilling in coal mines where water resources are extremely scarce. In summary, the system method of this invention can solve the technical problems of borehole collapse in unstable strata under complex geological conditions and the extremely low drilling efficiency of pneumatic directional drilling in rock formations, greatly expanding the applicable geological conditions range of directional drilling technology.

[0063] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0064] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0065] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A gas-liquid dual-circulation directional drilling system for complex underground coal mine formations, characterized in that, It includes a directional drill bit (1), a double-walled hollow hydraulically driven screw drill (2), a three-channel instrument outer tube (3), a three-channel drill rod (4), and a three-channel water pipe (5) connected in sequence. The double-walled hollow hydraulically driven screw drill (2) includes a hollow rotor (2-5), a universal joint (2-3), and a drive shaft (2-1) connected in sequence, and also includes a stator (2-6) sleeved outside the rotor (2-5), a stator rod body (2-7) provided outside the stator (2-6), and a screw drill outer tube (2-8) sleeved outside the stator rod body (2-7); the three-channel instrument outer tube (3) includes an inner tube (3-1), a middle tube (3-2), and an outer tube (3-3) sleeved in sequence from the inside to the outside; the three-channel drill rod (4) includes a drill rod inner tube (4-1), a drill rod middle tube (4-2), and a drill rod outer tube (4-3) sleeved in sequence from the inside to the outside; the three-channel water pipe (5) includes a water pipe inner tube (5-1), a water pipe middle tube (5-2), and a water pipe outer tube (5-3) sleeved in sequence from the inside to the outside. The drive shaft (2-1), universal joint (2-3), rotor (2-5), inner tube (3-1), drill rod inner tube (4-1), and water pipe inner tube (5-1) are connected sequentially from front to back to form a central channel (10). The front end of the central channel (10) is connected to the air hole of the directional drill bit (1), and the rear end of the central channel (10) is a high-pressure hose connector (5-4) to connect with the air compressor or nitrogen generator (6). The stator (2-6), stator rod (2-7), intermediate tube (3-2), drill rod intermediate tube (4-2), and water pipe intermediate tube (5-2) are connected sequentially to form an intermediate annular channel (20). The front end of the intermediate annular channel (20) is sealed by a sealing element (2-2), and the rear part of the intermediate annular channel (20) is connected to the high-pressure hose connector (5-4) to connect to the mud pump (7); the screw drill outer tube (2-8), outer tube (3-3), drill rod outer tube (4-3) and water pipe outer tube (5-3) are connected in sequence to form an outer annular channel (30). The front end of the outer annular channel (30) is sealed and connected to the intermediate annular channel (20) through a water eye (2-4) on the front side wall of the stator rod (2-7). The rear part of the outer annular channel (30) is connected to the high-pressure hose connector (5-4) to connect to the water tank (8).

2. The gas-liquid dual-circulation directional drilling system for complex underground coal mine formations as described in claim 1, characterized in that, The rotor (2-5) has a male connector at the rear end, which is inserted into the female connector at the front end of the inner tube (3-1). The stator rod (2-7) has a female connector at the rear end, which is inserted into the male connector at the front end of the intermediate tube (3-2). The screw drill tool outer tube (2-8) has a female thread at the rear end, which is connected to the male thread at the front end of the outer tube (3-3) by thread.

3. The gas-liquid dual-circulation directional drilling system for complex underground coal mine formations as described in claim 1, characterized in that, The rear end of the inner tube (3-1) is a male connector and is inserted into the front end of the female connector of the drill pipe inner tube (4-1). The rear end of the middle tube (3-2) is a female connector and is inserted into the front end of the drill pipe middle tube (4-2). The rear end of the outer tube (3-3) is a female thread and is connected to the front end of the drill pipe outer tube (4-3) by threaded connection.

4. The gas-liquid dual-circulation directional drilling system for complex underground coal mine formations as described in claim 1, characterized in that, The rear end of the drill pipe inner tube (4-1) is a male connector and is inserted into the front end of the water pipe inner tube (5-1). The rear end of the drill pipe middle tube (4-2) is a female connector and is inserted into the front end of the water pipe middle tube (5-2). The rear end of the drill pipe outer tube (4-3) is a female thread and is connected to the front end of the water pipe outer tube (5-3) by threaded connection.

5. The gas-liquid dual-circulation directional drilling system for complex underground coal mine formations as described in claim 1, characterized in that, A sealing ring is provided between the rear outer wall of the inner water pipe (5-1) and the annular boss on the rear inner wall of the middle water pipe (5-2); a sealing ring is provided between the rear outer wall of the middle water pipe (5-2) and the annular boss on the rear inner wall of the outer water pipe (5-3); bearing assemblies are installed between the inner water pipe (5-1) and the middle water pipe (5-2), and between the middle water pipe (5-2) and the outer water pipe (5-3), so that the inner water pipe (5-1), the middle water pipe (5-2), and the outer water pipe (5-3) can rotate independently of each other.

6. The gas-liquid dual-circulation directional drilling system for complex underground coal mine formations as described in claim 1, characterized in that, The inner water pipe (5-1) has a connecting hole in the rear side wall, which connects the intermediate annular channel (20) and the high-pressure hose connector (5-4); the middle water pipe (5-2) has a connecting hole in the rear side wall, which connects the outer annular channel (30) and the high-pressure hose connector (5-4).

7. The gas-liquid dual-circulation directional drilling system for complex underground coal mine formations as described in claim 1, characterized in that, The central channel (10) corresponding to the three-channel instrument outer tube (3) is equipped with a drilling measurement instrument assembly (3-4).

8. The gas-liquid dual-circulation directional drilling system for complex underground coal mine formations as described in claim 7, characterized in that, The central channel (10) is a high-pressure air or nitrogen inlet channel, the intermediate annular channel (20) is a high-pressure water inlet channel, and the outer annular channel (30) is a high-pressure water outlet channel. The high-pressure water enters through the intermediate annular channel (20) to drive the rotor (2-5) of the double-walled hollow hydraulic screw drill (2) to rotate and drive the directional drill bit (1) to rotate and break rocks for drilling. Then it exits through the outer annular channel and enters the water tank (8). The high-pressure air or nitrogen enters through the central channel (10) to the air hole of the directional drill bit (1) to cool the directional drill bit (1) and carry the drill cuttings. Then it exits through the directional drill bit and the hole wall annular channel.

9. The gas-liquid dual-circulation directional drilling system for complex underground coal mine formations as described in claim 8, characterized in that, The high-pressure water enters through the intermediate annular channel (20) to drive the rotor (2-5) of the double-walled hollow hydraulic screw drill (2) to rotate, and then exits through the outer annular channel (30) into the water tank (8), and is then sucked into the intermediate annular channel (20) by the mud pump (7), thus realizing the recycling of high-pressure water.

10. The method for directional drilling using the gas-liquid dual-circulation directional drilling system for complex underground coal mine formations as described in claim 8, characterized in that, Includes the following steps: Step 1: Connect the directional drill bit, double-walled hollow hydraulic screw drill bit, three-channel instrument outer tube, three-channel drill rod, and three-channel water pipe in sequence; Step 2: The central channel of the three-channel water toilet is connected to the air compressor or nitrogen generator through a high-pressure hose; the middle annular channel of the three-channel water toilet is connected to the mud pump through a high-pressure hose; and the outer annular channel of the three-channel water toilet is connected to the water tank through a high-pressure hose. Step 3: Start the mud pump, air compressor or nitrogen generator to supply high-pressure water and high-pressure air or nitrogen into the directional drilling tool. The high-pressure air or nitrogen returns out of the hole from the annular channel between the directional drilling tool and the hole wall, and the high-pressure water returns to the water tank from the outer annular channel. The high-pressure water is recycled. Step 4: Start the directional drilling rig, rotate the directional drilling tool to adjust the tool face angle, and use the directional drilling rig to push the directional drilling tool forward, which in turn drives the directional drill bit forward. The double-walled hollow hydraulically driven screw drill tool drives the directional drill bit to rotate and break the rock, thus achieving sliding directional drilling. Step 5: When the three-channel drill pipe of the directional drilling rig has finished drilling, turn off the mud pump, turn off the air compressor or nitrogen generator, disconnect the three-channel water pipe, use the measurement while drilling instrument assembly to measure the borehole trajectory, reconnect the three-channel drill pipe, and then reconnect the three-channel water pipe. Step 6: Repeat steps 3, 4 and 5 to complete the directional drilling.

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