Dual-power large-caliber inner deslagging wall protection type soft coal seam drilling device and construction method thereof

Abstract

The invention relates to the technical field of coal mining equipment, in particular to a dual-power large-diameter inner deslagging wall protection type soft coal seam drilling device and a construction method thereof. According to the technical scheme, the drill bit comprises outer drill rods, a spiral inner drill rod, a pipe drill bit, a PDC drill bit and an inner rod body, a composite slice drill bit is arranged at one end of the pipe drill bit, the inner rod body is arranged in the pipe drill bit, the PDC drill bit located on one side of the slice drill bit is arranged at one end of the inner rod body, and multiple sections of outer drill rods are arranged on one side of the pipe drill bit. A plurality of sections of spiral inner drill rods located in the outer drill rod are arranged on one side of the inner rod body. By means of the large-diameter dual-power dual-channel inner deslagging structure, the problems of drilling in a soft medium layer, hole spraying, hole collapsing, drill holding and other serious phenomena are mainly solved, the hole forming rate is low, the hole drilling construction difficulty is large, coal holes can be subjected to wall protection, the deslagging efficiency is improved, and the hole forming rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining equipment, in particular to a dual-power large-diameter internal slag discharge wall protection type soft coal seam drilling device and a construction method thereof. Background Art

[0002] During the drilling process of coal seams, it is easy to cause phenomena such as hole collapse, drill sticking, and blowout. The existing external slag discharge technology is generally characterized by low strength and high fissure development in coal seams in western regions. The gas content of western coal seams is high, and it has the following main problems: unstable slag discharge channels, which easily lead to borehole deformation and hole collapse; low slag discharge efficiency, accumulation of drill slag, affecting drilling efficiency; poor adaptability, large fluctuations in hole depth, and uncontrollable drilling process.

[0003] Although the existing dual-power internal slag discharge equipment can achieve internal slag discharge, the prerequisite is that the soft media layer must be small enough to prevent the holes from being stuck or blocked in the dual-channel internal slag discharge equipment, which in turn causes high pressure on the spiral blades of the inner drill pipe, resulting in blockage, and in severe cases, leading to hole collapse and drill bit sticking, resulting in economic losses;

[0004] Existing internal slag removal equipment requires a specialized slag collector for slag removal, as the outer rod is subject to high torque and the drill bit is connected to the outer rod. Furthermore, when the drill rod is rotating, it is difficult for coal slag to enter the slag collector, resulting in low efficiency. Therefore, those skilled in the art have provided a dual-powered, large-diameter, internal slag removal, wall-protecting soft coal seam drilling device to address the problems raised in the above-mentioned background technology. Summary of the Invention

[0005] The purpose of the present invention is to address the problems existing in the background technology and propose a dual-power large-diameter internal slag discharge wall protection soft coal seam drilling device and its construction method. In view of the characteristics of soft coal seams such as poor permeability and high gas content, it is easy to produce hole collapse, drill sticking, and blowout during the coal seam drilling construction process. It is mainly used for drilling slag and pressure relief in soft coal seams.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a dual-power large-diameter internal slag discharge wall protection soft coal seam drilling device, comprising an external drill rod, a spiral inner drill rod, a tube drill bit, a PDC drill bit and an inner rod body, one end of the tube drill bit is provided with a composite slicing drill bit, an inner rod body is provided inside the tube drill bit, one end of the inner rod body is provided with a PDC drill bit located on one side of the slicing drill bit, one side of the tube drill bit is provided with multiple sections of external drill rods, and one side of the inner rod body is provided with multiple sections of spiral inner drill rods located inside the external drill rod.

[0007] Preferably, the outer wall of the spiral inner drill rod is welded with multiple sets of blades arranged in a spiral pattern, and the blades between the spiral inner drill rods are in close contact. This close contact reduces coal dust leakage and improves the stability of the slag discharge channel. The spiral blades form a continuous conveyor belt, enhancing the propulsion force of the slag and preventing the accumulation of drill cuttings. The spiral thrust overcomes the influence of gravity in the inclined hole.

[0008] Preferably, the spiral inner drill rod and the PDC drill bit are each provided with interconnected flow channels, and the outer wall of the PDC drill bit is provided with multiple fluid holes connected to the internal flow channels of the PDC drill bit. Flushing fluid flows directly through the flow channels to the drill bit, cooling the PDC drill bit and lubricating the hole wall, thereby extending the drill bit life. Flushing fluid is discharged through the fluid holes in multiple streams, evenly distributed at the PDC drill bit.

[0009] Preferably, a spirally distributed slag discharge channel is provided between the blades and the outer drill rod, and is located between the spiral inner drill rod and the outer drill rod. The slag discharge channel is separated from the flushing fluid flow path to prevent coal slime from clogging the waterway. The spiral structure can adapt to fluctuations in hole depth and reduce fluctuations in drill rod torque.

[0010] Preferably, a threaded butt joint 1 is provided at one end of the tube drill bit, a threaded butt joint 2 is provided at one end of the external drill rod, and a threaded butt joint 1 is provided on the inner wall of one end of the external drill rod for threadedly sleeved installation with the threaded butt joint 1 and the threaded butt joint 2. The threaded butt joint 1, the threaded butt joint 2 and the threaded butt joint 1 constitute a threaded butt joint structure 1.

[0011] Preferably, a threaded butt joint four is provided at one end of the inner rod body, a threaded butt joint three is provided at one end of the spiral inner drill rod, and a threaded butt groove two is provided inside one end of the threaded inner drill rod for threadedly sleeved installation with the threaded butt joint three and the threaded butt joint four, and the threaded butt joint three, the threaded butt joint four and the threaded butt groove two constitute a threaded butt structure two.

[0012] Preferably, the threads of the first and second threaded docking structures are tightened in opposite directions. The threaded docking structure simplifies the assembly process of the drill rod, and the reverse threads of the first and second threaded docking structures meet the need of automatically locking the outer drill rod and the spiral inner drill rod in opposite directions during drilling.

[0013] Preferably, the PDC drill bit is the primary drilling cutting tool and has a smaller diameter than the external drill rod and tubing drill bit.

[0014] Preferably, the external drill rod is a large-diameter outer casing, which primarily serves as a wall protector and increases the distance between the drill rod and the internal drill rod, thereby improving internal slag removal efficiency. The PDC drill bit first drills the hole, while the pipe drill bit simultaneously expands the hole to reduce disturbance of the hole wall. The external drill rod of the large-diameter outer casing immediately supports the hole wall, and the expanded annulus accommodates the secondary cut coal slag and grinds the fragments of the primary cut coal slag.

[0015] The tubular bit and PDC drill bit preferably have different cutting diameters and opposite cutting directions. The tubular bit is primarily used for hole enlargement, and a large annulus is left between the PDC bit and the tubular bit. The reverse cutting generates shear force, breaking up large particles of coal slag and adapting to the size of the internal slag discharge channel.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The PDC drill bit and the composite cutting blade drill bit of the present invention cut in tandem, with different cutting calibers and opposite cutting directions. The PDC drill bit is the main drilling component, and the composite cutting blade drill bit is mainly used for expanding holes.

[0018] A layered cutting drill bit is used, with the inner rod body equipped with a PDC drill bit, and the tubular external drill rod equipped with a composite cutting blade drill bit. The inner rod body and the PDC drill bit bear the main torque and the main cutting task of hole formation. The cut coal seam is repeatedly ground and refined. The tubular external drill rod is equipped with a composite slicing drill bit to perform secondary cutting on large-particle coal so that it can enter the internal slag discharge channel. The composite slicing drill bit performs secondary drilling to form a large-diameter deep hole. The structure is simple and the slag discharge is smoother. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the main three-dimensional structure of the present invention;

[0020] Figure 2 It is a schematic diagram of the main cross-sectional three-dimensional structure of the present invention;

[0021] Figure 3 This is a schematic diagram of the main three-dimensional structure of the multi-section spiral inner drill rod of the present invention;

[0022] Figure 4 This is a schematic diagram of the main cross-sectional perspective structure of the external drill rod of the present invention;

[0023] Figure 5 This is a schematic diagram of the main three-dimensional structure of a single-section spiral inner drill rod of the present invention;

[0024] Figure 6 This is a schematic diagram of the main three-dimensional structure of the inner rod body of the present invention;

[0025] Figure 7 This is a schematic diagram of the three-dimensional structure of the tubular drill bit and the PDC drill bit of the present invention when viewed from above;

[0026] Figure 8 This is a schematic side view of the three-dimensional structure of the PDC drill bit of the present invention;

[0027] Figure 9 This is a schematic diagram of the main three-dimensional structure of a single-section external drill rod of the present invention.

[0028] Figure numerals: 1. External drill rod; 2. Spiral inner drill rod; 3. Tube drill bit; 4. PDC drill bit; 5. Flow channel; 6. Liquid hole; 7. Slag discharge channel; 8. Threaded butt joint 1; 9. Threaded butt joint 2; 10. Threaded butt groove 1; 11. Threaded butt joint 3; 12. Threaded butt groove 2; 13. Threaded butt joint 4; 14. Composite slicing drill bit; 15. Inner rod body. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] See also Figures 1 to 9 , the present invention provides three embodiments:

[0031] Example 1:

[0032] A dual-powered, large-diameter, internal slag removal, wall-protecting soft coal seam drilling device comprises an external drill rod 1, a spiral internal drill rod 2, a pipe drill bit 3, a PDC drill bit 4, and an internal rod body 15. A composite slicing drill bit 14 is provided at one end of the pipe drill bit 3. The internal rod body 15 is provided inside the pipe drill bit 3. A PDC drill bit 4 is provided at one end of the internal rod body 15, located on the side of the slicing drill bit. Multiple sections of the external drill rod 1 are provided on one side of the pipe drill bit 3.

[0033] The PDC drill bit 4 is the main drilling and cutting tool, and its diameter is smaller than the external drill rod 1 and the pipe drill bit 3;

[0034] The external drill rod 1 is a large-diameter outer casing, which mainly plays the role of wall protection and increases the space distance between it and the rotating inner drill rod, thereby improving the internal slag removal efficiency;

[0035] The casing drill bit 3 and the PDC drill bit 4 have different cutting diameters and opposite cutting directions. The casing drill bit 3 is mainly used for hole expansion. A large annulus is left between the PDC drill bit 4 and the casing drill bit 3.

[0036] In this embodiment, the external drill rod 1 and the spiral inner drill rod 2 are connected to two sets of power heads respectively. The speed and direction are independently controlled by the variable frequency motor. The external drill rod 1 rotates clockwise to provide wall protection torque, and the spiral inner drill rod 2 rotates counterclockwise to drive the PDC drill bit 4 to cut. The reverse motion offsets the overall torque fluctuation of the drill rod system and reduces the risk of drill sticking.

[0037] The threaded connection structure 1 and structure 2 adopt reverse thread design (left-hand and right-hand). During drilling, the rotation direction of the drill pipe is consistent with the thread locking direction. The drilling torque is used to automatically strengthen the drill pipe connection to prevent the drill pipe from falling off during deep hole operation.

[0038] The inner rod 15 and the PDC drill bit 4 bear the main cutting torque, giving priority to breaking the coal seam. The pipe drill bit 3 and the composite cutting blade expand and grind at a low speed, breaking up the large coal slag for the second time. The layered design reduces the torque load at a single point and prolongs the life of the drill bit.

[0039] The blades of the spiral inner drill pipe 2 are optimized for fluid dynamics to ensure efficient slag removal while reducing blade wear. Flushing fluid is delivered to the PDC drill bit 4 through the central flow channel 5 of the spiral inner drill pipe 2 and ejected through the liquid hole 6. The resulting flushing surface covers the drill bit cutting area. The liquid hole 6 adopts a tapered design to effectively clean the coal powder on the drill bit tooth surface. The slag discharge channel 7 is completely isolated from the flow channel 5. The flushing fluid is only used for cooling and lubrication. The slag is discharged by spiral thrust and gravity, avoiding the cross-interference problem of hydraulic and mechanical slag discharge in traditional internal slag discharge equipment.

[0040] The surface pumping system integrates a pressure sensor to monitor the pressure of flow channel 5 in real time. When the slag discharge channel 7 is blocked, the pressure in flow channel 5 suddenly rises, triggering the variable frequency motor to slow down and simultaneously increasing the flow rate of the flushing fluid. The blockage is cleared by the impact of the liquid kinetic energy. The dual-power reverse rotation combined with the spiral slag discharge channel 7 improves the slag discharge efficiency compared to traditional equipment. The spiral blade fitting design reduces coal powder leakage, and the composite cutting blade grinds large particles of coal slag. Combined with the flushing fluid adjustment, the risk of drill sticking is completely eliminated.

[0041] The large-diameter external drill rod 1 instantly supports the hole wall and cooperates with the flushing fluid for lubrication, which reduces the collapse rate. It is especially suitable for high-gas soft coal seams in the west. The dual-channel structure means that one channel enters the fluid and the other channel discharges the fluid at the same time. During the drilling process, the drill cuttings do not go through the drill hole, reducing the impact of the drill cuttings and fluid on the wall of the completed drill hole, thereby ensuring the drill hole size, reducing deviation, and high drill cuttings discharge efficiency. The external drill rod 1 with the dual-channel structure can be left directly in the drill hole as a casing to directly extract gas. The spiral inner drill rod 2 for dual-channel internal slag discharge has multiple spiral structures inside, and the spiral thrust is used to achieve ultra-long-distance drill cuttings transportation. The dual-channel internal spiral structure can overcome the difficulty of slag discharge in inclined holes. At the same time, the large-diameter drill rod can also play a wall protection role during drilling.

[0042] Example 2:

[0043] It includes an external drill rod 1, a spiral inner drill rod 2, a pipe drill bit 3, a PDC drill bit 4 and an inner rod body 15. A composite slicing drill bit 14 is provided at one end of the pipe drill bit 3. The inner rod body 15 is provided inside the pipe drill bit 3. A PDC drill bit 4 is provided at one end of the inner rod body 15, which is located on the side of the slicing drill bit. Multiple sections of the external drill rod 1 are provided on one side of the pipe drill bit 3.

[0044] The PDC drill bit 4 is the main drilling and cutting tool, and its diameter is smaller than the external drill rod 1 and the pipe drill bit 3;

[0045] The external drill rod 1 is a large-diameter outer casing, which mainly plays the role of wall protection and increases the space distance between it and the rotating inner drill rod, thereby improving the internal slag removal efficiency;

[0046] The casing drill bit 3 and the PDC drill bit 4 have different cutting diameters and opposite cutting directions. The casing drill bit 3 is mainly used for hole expansion. A large annulus is left between the PDC drill bit 4 and the casing drill bit 3.

[0047] In this embodiment, the external drill rod 1 and the spiral inner drill rod 2 are connected to two sets of power heads respectively. The speed and direction are independently controlled by the variable frequency motor. The external drill rod 1 rotates clockwise to provide wall protection torque, and the spiral inner drill rod 2 rotates counterclockwise to drive the PDC drill bit 4 to cut. The reverse motion offsets the overall torque fluctuation of the drill rod system and reduces the risk of drill sticking.

[0048] The threaded connection structure 1 and structure 2 adopt reverse thread design (left-hand and right-hand). During drilling, the rotation direction of the drill pipe is consistent with the thread locking direction. The drilling torque is used to automatically strengthen the drill pipe connection to prevent the drill pipe from falling off during deep hole operation.

[0049] The inner rod 15 and the PDC drill bit 4 bear the main cutting torque, giving priority to breaking the coal seam. The pipe drill bit 3 and the composite cutting blade expand and grind at a low speed, breaking up the large coal slag for the second time. The layered design reduces the torque load at a single point and prolongs the life of the drill bit.

[0050] The blades of the spiral inner drill pipe 2 are optimized for fluid dynamics to ensure efficient slag removal while reducing blade wear. Flushing fluid is delivered to the PDC drill bit 4 through the central flow channel 5 of the spiral inner drill pipe 2 and ejected through the liquid hole 6. The resulting flushing surface covers the drill bit cutting area. The liquid hole 6 adopts a tapered design to effectively clean the coal powder on the drill bit tooth surface. The slag discharge channel 7 is completely isolated from the flow channel 5. The flushing fluid is only used for cooling and lubrication. The slag is discharged by spiral thrust and gravity, avoiding the cross-interference problem of hydraulic and mechanical slag discharge in traditional internal slag discharge equipment.

[0051] The surface pumping system integrates a pressure sensor to monitor the pressure of flow channel 5 in real time. When the slag discharge channel 7 is blocked, the pressure in flow channel 5 suddenly rises, triggering the variable frequency motor to slow down and simultaneously increasing the flow rate of the flushing fluid. The blockage is cleared by the impact of the liquid kinetic energy. The dual-power reverse rotation combined with the spiral slag discharge channel 7 improves the slag discharge efficiency compared to traditional equipment. The spiral blade fitting design reduces coal powder leakage, and the composite cutting blade grinds large particles of coal slag. Combined with the flushing fluid adjustment, the risk of drill sticking is completely eliminated.

[0052] The large-diameter external drill rod 1 instantly supports the hole wall and cooperates with the flushing fluid for lubrication, which reduces the collapse rate. It is especially suitable for high-gas soft coal seams in the west. The dual-channel structure means that one channel enters the fluid and the other channel discharges the fluid at the same time. During the drilling process, the drill cuttings do not go through the drill hole, reducing the impact of the drill cuttings and fluid on the wall of the completed drill hole, thereby ensuring the drill hole size, reducing deviation, and high drill cuttings discharge efficiency. The external drill rod 1 with the dual-channel structure can be left directly in the drill hole as a casing to directly extract gas. The spiral inner drill rod 2 for dual-channel internal slag discharge has multiple spiral structures inside, and the spiral thrust is used to achieve ultra-long-distance drill cuttings transportation. The dual-channel internal spiral structure can overcome the difficulty of slag discharge in inclined holes. At the same time, the large-diameter drill rod can also play a wall protection role during drilling.

[0053] One side of the inner rod body 15 is provided with multiple sections of spiral inner drill rods 2 located inside the outer drill rod 1;

[0054] The outer wall of the spiral inner drill rod 2 is welded with multiple groups of blades distributed in a spiral, and the blades between the spiral inner drill rods 2 are in close contact with each other;

[0055] A spirally distributed slag discharge channel 7 is provided between the blade and the external drill rod 1. The slag discharge channel 7 is located between the spiral inner drill rod 2 and the external drill rod 1.

[0056] The spiral inner drill rod 2 and the PDC drill bit 4 are both provided with flow channels 5 that are interconnected. The outer wall of the PDC drill bit 4 is provided with a plurality of liquid holes 6 that are connected to the flow channels 5 inside the PDC drill bit 4.

[0057] In this embodiment, the core is to solve the problems of low slag discharge efficiency, unbalanced drill pipe torque and poor hole wall stability in the prior art through a double-layer drill pipe structure design and a reverse threaded connection mechanism. The specific structure includes five parts: an external drill pipe 1, a spiral inner drill pipe 2, a pipe drill bit 3, a PDC drill bit 4 and an inner rod body 15. The external drill pipe 1 is made of a large-diameter seamless steel pipe, the surface of which is treated with a wear-resistant coating and mainly performs the wall protection function; the spiral inner drill pipe 2 is made of high-strength alloy steel, and continuous spiral blades are welded on the surface, and the blade end faces of adjacent spiral inner drill pipes 2 are precisely docked to form a leak-free spiral slag discharge channel 7. A composite slicing drill bit 14 is installed at the front end of the pipe drill bit 3, whose outer diameter is consistent with the external drill pipe 1 and the inner diameter matches the spiral inner drill pipe 2. The diameter of the PDC drill bit 4 is 20% smaller than that of the pipe drill bit 3 and is connected to the spiral inner drill pipe 2 through the inner rod body 15 to form a layered cutting structure;

[0058] Through the physical isolation of the spiral slag discharge channel 7 and the flushing liquid flow channel 5, the axial flow channel 5 opened in the center of the spiral inner drill pipe 2 is connected to the annular flow channel 5 inside the PDC drill bit 4. A plurality of tapered liquid holes 6 are evenly arranged on the surface of the PDC drill bit 4. The hole outlet diameter is reduced to 3mm to increase the jet velocity. The flushing liquid is delivered at a pressure of 3MPa through the independent flow channel 5 to achieve drill bit cooling and hole wall lubrication, while the coal slag is reversely discharged through the annular gap formed by the spiral blades and the inner wall of the external drill pipe 1. This design improves the slag discharge efficiency, which is higher than that of traditional equipment, and reduces the consumption of flushing liquid.

[0059] The adaptive control of the slag discharge system is achieved through multi-sensor fusion. A pressure sensor is installed at the end of the spiral inner drill rod 2, with a range of 0-10MPa and an accuracy of ±0.1%FS. The back pressure of the slag discharge channel 7 is monitored in real time. When the pressure exceeds the set threshold;

[0060] For example, when the pressure reaches 4MPa, the PLC automatically triggers the three-level response:

[0061] ① The rotation speed of the spiral inner drill rod 2 is increased by 20% to enhance the thrust for slag removal;

[0062] ② Increase the flushing liquid pump flow rate by 30% to flush the blockage point;

[0063] ③ If the pressure does not drop within 10 seconds, the external drill rod 1 will stop rotating to prevent the hole from getting blocked. This mechanism reduces the incidence of hole blockage compared to traditional equipment.

[0064] The multi-spiral flow channel 5 design between the spiral blades further improves the slag removal efficiency. CFD simulation is used to determine the blade spiral angle is 28°. A 0.2mm thick tungsten carbide coating is sprayed on the blade surface to reduce the friction coefficient. Under the inclined drilling condition, the spiral thrust and the gravity component are superimposed to form a composite slag removal power. Compared with horizontal drilling, the efficiency does not decrease significantly, which is significantly better than traditional spiral slag removal.

[0065] Example 3:

[0066] It includes an external drill rod 1, a spiral inner drill rod 2, a pipe drill bit 3, a PDC drill bit 4 and an inner rod body 15. A composite slicing drill bit 14 is provided at one end of the pipe drill bit 3. The inner rod body 15 is provided inside the pipe drill bit 3. A PDC drill bit 4 is provided at one end of the inner rod body 15, which is located on the side of the slicing drill bit. Multiple sections of the external drill rod 1 are provided on one side of the pipe drill bit 3.

[0067] The PDC drill bit 4 is the main drilling and cutting tool, and its diameter is smaller than the external drill rod 1 and the pipe drill bit 3;

[0068] The external drill rod 1 is a large-diameter outer casing, which mainly plays the role of wall protection and increases the space distance between it and the rotating inner drill rod, thereby improving the internal slag removal efficiency;

[0069] The casing drill bit 3 and the PDC drill bit 4 have different cutting diameters and opposite cutting directions. The casing drill bit 3 is mainly used for hole expansion. A large annulus is left between the PDC drill bit 4 and the casing drill bit 3.

[0070] In this embodiment, the external drill rod 1 and the spiral inner drill rod 2 are connected to two sets of power heads respectively. The speed and direction are independently controlled by the variable frequency motor. The external drill rod 1 rotates clockwise to provide wall protection torque, and the spiral inner drill rod 2 rotates counterclockwise to drive the PDC drill bit 4 to cut. The reverse motion offsets the overall torque fluctuation of the drill rod system and reduces the risk of drill sticking.

[0071] The threaded connection structure 1 and structure 2 adopt reverse thread design (left-hand and right-hand). During drilling, the rotation direction of the drill pipe is consistent with the thread locking direction. The drilling torque is used to automatically strengthen the drill pipe connection to prevent the drill pipe from falling off during deep hole operation.

[0072] The inner rod 15 and the PDC drill bit 4 bear the main cutting torque, giving priority to breaking the coal seam. The pipe drill bit 3 and the composite cutting blade expand and grind at a low speed, breaking up the large coal slag for the second time. The layered design reduces the torque load at a single point and prolongs the life of the drill bit.

[0073] The blades of the spiral inner drill pipe 2 are optimized for fluid dynamics to ensure efficient slag removal while reducing blade wear. Flushing fluid is delivered to the PDC drill bit 4 through the central flow channel 5 of the spiral inner drill pipe 2 and ejected through the liquid hole 6. The resulting flushing surface covers the drill bit cutting area. The liquid hole 6 adopts a tapered design to effectively clean the coal powder on the drill bit tooth surface. The slag discharge channel 7 is completely isolated from the flow channel 5. The flushing fluid is only used for cooling and lubrication. The slag is discharged by spiral thrust and gravity, avoiding the cross-interference problem of hydraulic and mechanical slag discharge in traditional internal slag discharge equipment.

[0074] The surface pumping system integrates a pressure sensor to monitor the pressure of flow channel 5 in real time. When the slag discharge channel 7 is blocked, the pressure in flow channel 5 suddenly rises, triggering the variable frequency motor to slow down and simultaneously increasing the flow rate of the flushing fluid. The blockage is cleared by the impact of the liquid kinetic energy. The dual-power reverse rotation combined with the spiral slag discharge channel 7 improves the slag discharge efficiency compared to traditional equipment. The spiral blade fitting design reduces coal powder leakage, and the composite cutting blade grinds large particles of coal slag. Combined with the flushing fluid adjustment, the risk of drill sticking is completely eliminated.

[0075] The large-diameter external drill rod 1 instantly supports the hole wall and cooperates with the flushing fluid for lubrication, which reduces the collapse rate. It is especially suitable for high-gas soft coal seams in the west. The dual-channel structure means that one channel enters the fluid and the other channel discharges the fluid at the same time. During the drilling process, the drill cuttings do not go through the drill hole, reducing the impact of the drill cuttings and fluid on the wall of the completed drill hole, thereby ensuring the drill hole size, reducing deviation, and high drill cuttings discharge efficiency. The external drill rod 1 with the dual-channel structure can be left directly in the drill hole as a casing to directly extract gas. The spiral inner drill rod 2 for dual-channel internal slag discharge has multiple spiral structures inside, and the spiral thrust is used to achieve ultra-long-distance drill cuttings transportation. The dual-channel internal spiral structure can overcome the difficulty of slag discharge in inclined holes. At the same time, the large-diameter drill rod can also play a wall protection role during drilling.

[0076] One side of the inner rod body 15 is provided with multiple sections of spiral inner drill rods 2 located inside the outer drill rod 1;

[0077] The outer wall of the spiral inner drill rod 2 is welded with multiple groups of blades distributed in a spiral, and the blades between the spiral inner drill rods 2 are in close contact with each other;

[0078] A spirally distributed slag discharge channel 7 is provided between the blade and the external drill rod 1. The slag discharge channel 7 is located between the spiral inner drill rod 2 and the external drill rod 1.

[0079] The spiral inner drill rod 2 and the PDC drill bit 4 are both provided with flow channels 5 that are interconnected. The outer wall of the PDC drill bit 4 is provided with a plurality of liquid holes 6 that are connected to the flow channels 5 inside the PDC drill bit 4.

[0080] In this embodiment, the core is to solve the problems of low slag discharge efficiency, unbalanced drill pipe torque and poor hole wall stability in the prior art through a double-layer drill pipe structure design and a reverse threaded connection mechanism. The specific structure includes five parts: an external drill pipe 1, a spiral inner drill pipe 2, a pipe drill bit 3, a PDC drill bit 4 and an inner rod body 15. The external drill pipe 1 is made of a large-diameter seamless steel pipe, the surface of which is treated with a wear-resistant coating and mainly performs the wall protection function; the spiral inner drill pipe 2 is made of high-strength alloy steel, and continuous spiral blades are welded on the surface, and the blade end faces of adjacent spiral inner drill pipes 2 are precisely docked to form a leak-free spiral slag discharge channel 7. A composite slicing drill bit 14 is installed at the front end of the pipe drill bit 3, whose outer diameter is consistent with the external drill pipe 1 and the inner diameter matches the spiral inner drill pipe 2. The diameter of the PDC drill bit 4 is 20% smaller than that of the pipe drill bit 3 and is connected to the spiral inner drill pipe 2 through the inner rod body 15 to form a layered cutting structure;

[0081] Through the physical isolation of the spiral slag discharge channel 7 and the flushing liquid flow channel 5, the axial flow channel 5 opened in the center of the spiral inner drill pipe 2 is connected to the annular flow channel 5 inside the PDC drill bit 4. A plurality of tapered liquid holes 6 are evenly arranged on the surface of the PDC drill bit 4. The hole outlet diameter is reduced to 3mm to increase the jet velocity. The flushing liquid is delivered at a pressure of 3MPa through the independent flow channel 5 to achieve drill bit cooling and hole wall lubrication, while the coal slag is reversely discharged through the annular gap formed by the spiral blades and the inner wall of the external drill pipe 1. This design improves the slag discharge efficiency, which is higher than that of traditional equipment, and reduces the consumption of flushing liquid.

[0082] The adaptive control of the slag discharge system is achieved through multi-sensor fusion. A pressure sensor is installed at the end of the spiral inner drill rod 2, with a range of 0-10MPa and an accuracy of ±0.1%FS. The back pressure of the slag discharge channel 7 is monitored in real time. When the pressure exceeds the set threshold;

[0083] For example, when the pressure reaches 4MPa, the PLC automatically triggers the three-level response:

[0084] ① The rotation speed of the spiral inner drill rod 2 is increased by 20% to enhance the thrust for slag removal;

[0085] ② Increase the flushing liquid pump flow rate by 30% to flush the blockage point;

[0086] ③ If the pressure does not drop within 10 seconds, the external drill rod 1 will stop rotating to prevent the hole from getting blocked. This mechanism reduces the incidence of hole blockage compared to traditional equipment.

[0087] The multi-spiral flow channel 5 design between the spiral blades further improves the slag removal efficiency. CFD simulation is used to determine the blade spiral angle is 28°. A 0.2mm thick tungsten carbide coating is sprayed on the blade surface to reduce the friction coefficient. Under the inclined drilling condition, the spiral thrust and the gravity component are superimposed to form a composite slag removal power. Compared with horizontal drilling, the efficiency does not decrease significantly, which is significantly better than traditional spiral slag removal.

[0088] A threaded butt joint 8 is provided at one end of the pipe drill bit 3, a threaded butt joint 2 9 is provided at one end of the external drill rod 1, and a threaded butt joint groove 10 is provided on the inner wall of one end of the external drill rod 1 for threadedly sleeved installation with the threaded butt joint 8 and the threaded butt joint 2 9. The threaded butt joint 8, the threaded butt joint 2 9 and the threaded butt joint groove 10 constitute a threaded butt joint structure 1;

[0089] A threaded butt joint 4 13 is provided at one end of the inner rod body 15, a threaded butt joint 3 11 is provided at one end of the spiral inner drill rod 2, and a threaded butt joint 2 12 is provided inside one end of the threaded inner drill rod for threadedly sleeved installation with the threaded butt joint 3 11 and the threaded butt joint 4 13. The threaded butt joint 3 11, the threaded butt joint 4 13 and the threaded butt joint 2 12 constitute a threaded butt joint structure 2;

[0090] The tightening directions of the threads of the threaded butt joint structure 1 and the threaded butt joint structure 2 are opposite;

[0091] In this embodiment, the external drill rod 1 adopts a right-hand thread for clockwise locking, and the spiral inner drill rod 2 adopts a left-hand thread for counterclockwise locking. Specifically, a tapered right-hand male thread is provided at the end of the pipe drill bit 3 of the external drill rod 1, and a corresponding female thread groove is processed on the inner wall of the external drill rod 1. The left-hand male thread processed at the connecting end of the spiral inner drill rod 2 is provided with a left-hand female thread groove at the corresponding end. This design ensures that during the drilling process, when the external drill rod 1 rotates clockwise and the spiral inner drill rod 2 rotates counterclockwise, the torque direction generated by the drill rod system is consistent with the thread locking direction, and the rotational kinetic energy is used to automatically reinforce the connection to prevent the thread from loosening due to vibration during deep hole operation. Experiments have shown that under the condition of a hole depth of 1000 meters, this structure improves the torsional strength of the drill rod connection and reduces the probability of thread failure.

[0092] After drilling is completed, the spiral inner drill pipe 2 and PDC drill bit 4 can be withdrawn as a whole, and the outer drill pipe 1 remains in the hole as a permanent casing. The outer wall of the casing is preset with radial gas diversion grooves, and the inner wall is coated with an anti-static coating. It is directly connected to the gas extraction network. The dual-channel structure allows gas pre-extraction during drilling. The outer drill pipe 1 and the hole wall annulus serve as the main extraction channel, and the central flow channel 5 of the spiral inner drill pipe 2 serves as an auxiliary channel to form a three-dimensional extraction network.

[0093] It is worth noting that the external drill rod 1 and the spiral inner drill rod 2 are driven by two 55kW variable frequency motors respectively, and the speed and direction are independently controlled by the PLC controller. The external drill rod 1 is set to rotate clockwise with a speed range of 20-50r / min, and the spiral inner drill rod 2 rotates counterclockwise with a speed of 60-120r / min. The dual-power reverse rotation produces a shear effect, causing the PDC drill bit 4 to cut the main part and the composite slicing drill bit 14 to expand the hole to form layered crushing. The PDC drill bit 4 cuts the coal seam at a high speed to generate large-particle coal powder, and the composite slicing drill bit 14 performs secondary grinding on the large particles that are not fully crushed at a low speed.

[0094] Working principle:

[0095] S1: The PDC drill bit 4 rotates clockwise along the travel direction to perform drilling work at a distance of 2 m;

[0096] S2: After completing S1, the two drill bits (PDC drill bit 4 and composite slice drill bit 14) work simultaneously, and the two rotate in opposite directions;

[0097] S3: After reaching the predetermined hole depth, the tubular drill bit 3 remains in the hole and the PDC drill bit 4 exits the hole to facilitate subsequent gas extraction.

[0098] Advantages of combined dual-power dual-channel internal slag removal drilling equipment over integrated drilling equipment:

[0099] ①Simple structure, spiral inner drill rod 2 slag discharge is smoother;

[0100] ② The internal spiral drill rod 2 can be removed during drilling;

[0101] ③ The external drill rod 1 can be reserved inside the mine to facilitate subsequent gas extraction;

[0102] No need for secondary casing running, significantly reducing construction costs.

[0103] The above specific embodiments are only several preferred embodiments of the present invention. Based on the technical solutions of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

[0104] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A dual-power large-diameter internal slag removal wall-protecting soft coal seam drilling device, comprising an external drill rod (1), a spiral internal drill rod (2), a pipe drill bit (3), a PDC drill bit (4) and an internal rod body (15), characterized in that: A composite slicing drill bit (14) is provided at one end of the tube drill bit (3), an inner rod body (15) is provided inside the tube drill bit (3), a PDC drill bit (4) located on one side of the slicing drill bit is provided at one end of the inner rod body (15), multiple sections of external drill rods (1) are provided on one side of the tube drill bit (3), and multiple sections of spiral inner drill rods (2) located inside the external drill rods (1) are provided on one side of the inner rod body (15).

2. The dual-power large-diameter internal slag removal and wall-protecting soft coal seam drilling device according to claim 1 is characterized in that: The outer wall of the spiral inner drill rod (2) is welded with a plurality of groups of blades distributed in a spiral, and the blades between the spiral inner drill rods (2) are in close contact with each other.

3. The dual-power large-diameter internal slag removal and wall-protecting soft coal seam drilling device according to claim 1 is characterized in that: The spiral inner drill rod (2) and the PDC drill bit (4) are both provided with mutually communicating flow channels (5), and the outer wall of the PDC drill bit (4) is provided with a plurality of liquid holes (6) that are in communication with the internal flow channels (5) of the PDC drill bit (4).

4. The dual-power large-diameter internal slag removal and wall-protecting soft coal seam drilling device according to claim 2 is characterized in that: A slag discharge channel (7) distributed in a spiral pattern is provided between the blade and the external drill rod (1); the slag discharge channel (7) is located between the spiral inner drill rod (2) and the external drill rod (1).

5. The dual-power large-diameter internal slag removal and wall-protecting soft coal seam drilling device according to claim 1 is characterized in that: One end of the pipe drill bit (3) is provided with a threaded butt joint (8), and one end of the external drill rod (1) is provided with a threaded butt joint (9). The inner wall of one end of the external drill rod (1) is provided with a threaded butt joint (10) for threaded sleeve installation with the threaded butt joint (8) and the threaded butt joint (9). The threaded butt joint (8), the threaded butt joint (9) and the threaded butt joint (10) constitute a threaded butt joint structure (1).

6. The dual-powered, large-diameter, internal slag removal, wall-protecting soft coal seam drilling device according to claim 5 is characterized by: One end of the inner rod body (15) is provided with a threaded joint four (13), and one end of the spiral inner drill rod (2) is provided with a threaded joint three (11). One end of the threaded inner drill rod is provided with a threaded joint groove two (12) threadedly connected with the threaded joint three (11) and the threaded joint four (13). The threaded joint three (11), the threaded joint four (13) and the threaded joint groove two (12) constitute a threaded joint structure two.

7. The dual-power large-diameter internal slag removal and wall-protecting soft coal seam drilling device according to claim 6 is characterized in that: The screw thread of the first threaded docking structure is opposite to that of the second threaded docking structure.

8. The dual-powered, large-diameter, internal slag removal, wall-protecting soft coal seam drilling device according to claim 1 is characterized by: The PDC drill bit (4) is a main drilling cutting tool, and its diameter is smaller than the external drill rod (1) and the pipe drill bit (3).

9. The dual-powered, large-diameter, internal slag removal, wall-protecting soft coal seam drilling device according to claim 1, characterized in that: The external drill rod (1) is a large-diameter outer casing, which mainly plays the role of wall protection and increases the spatial distance between the external drill rod and the internal drill rod, thereby improving the internal slag removal efficiency.

10. The dual-power large-diameter internal slag removal and wall-protecting soft coal seam drilling device according to claim 1, characterized in that: The pipe drill bit (3) and the PDC drill bit (4) have different cutting diameters and opposite cutting directions. The pipe drill bit (3) is mainly used for hole expansion. A large annulus is left between the PDC drill bit (4) and the pipe drill bit (3).

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