A drilling device and method for drilling in water-prone areas of thick limestone layers at the bottom of coal seams.

Abstract

This invention relates to the field of coal seam drilling technology, and discloses a drilling device and method for drilling areas in thick limestone layers at the bottom of coal seams prone to water inrush. The device connects adjacent sets of double-wall drill rods via a conversion joint, and the end of the last set of double-wall drill rods is fixedly connected to a double-wall drive rod via the conversion joint. A screw motor is installed inside the double-wall drive rod, and a transmission seat is coaxially arranged at the end of the double-wall drive rod. The transmission seat contains a flow control component that controls the flow direction of the flushing fluid. A guide component is installed at the other end of the transmission seat to facilitate targeted drilling for different water inrush coefficients on the aquitard. This invention optimizes the design structure of the treatment borehole distribution network, enhances the support strength of the aquitard, adjusts the working state of the drill bit according to the water pressure inside the borehole, and improves the working environment of the drill bit by changing the high-pressure water inrush inside the borehole, avoiding significant resistance at the bottom of the drill bit from high-pressure water inrush that would prevent efficient rock breaking.

Description

Technical Field

[0001] This invention relates to the field of coal seam drilling technology, and in particular to a drilling device and method for drilling in water-prone areas of thick limestone layers at the bottom of coal seams. Background Technology

[0002] According to the formula for calculating the water inrush coefficient T = P / M in the "Detailed Rules for Water Prevention and Control in Coal Mines", in the actual coal mining process, it is necessary to conduct preliminary research on the geological and hydrogeological characteristics of the coal seam floor in the region. It was found that the Ordovician limestone aquifer on the floor of coal seam 5 in the region is the main aquifer. Therefore, it is necessary to carry out full-area coverage and treatment of the Ordovician limestone layer. Near-horizontal directional long boreholes in coal mines are an efficient means of water hazard prevention and control, and have obvious potential technical advantages in draining roof water, exploring old workings for water accumulation, and treating confined water in the floor.

[0003] Currently, the most commonly used drilling equipment on the market is the oil drilling rig, which can effectively complete the drilling operation of limestone layers. In the past, there were two methods for mining thin aquifers in coal mines and treating surface areas of thick limestone aquifers: one is to construct a main hole on the ground and treat aquifers at different depths through cutting and pulling technology; the other method is to implement multiple main holes on the ground to treat aquifers at different depths.

[0004] However, in actual use, current drilling equipment only targets aquifers to form a network of treatment holes and increases the thickness of the bottom aquitard through grouting. However, grouting through the treatment hole network can only solve the risk of water inrush in the thin bottom aquitard, but there is no drilling countermeasure for the thin aquitard at the top of the coal seam. This can lead to the danger of water inrush at the top. Therefore, the drilling equipment currently on the market cannot adjust the drilling strategy according to the changes in the water inrush coefficient of the top and bottom aquitards in the coal seam being mined. As a result, after the drilling equipment explores the treatment holes, it cannot complete the drilling of the treatment hole network in one go, resulting in low drilling efficiency.

[0005] Therefore, the present invention solves the above problems by providing a drilling device and drilling method for drilling areas with huge layers of limestone at the bottom of coal seams that are prone to water damage. Summary of the Invention

[0006] The purpose of this invention is to provide a drilling device and method for drilling in water-prone areas of thick limestone layers at the bottom of coal seams, in order to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a drilling device for a coal seam floor thick limestone flood-prone area, comprising several sets of identical double-wall drill rods, adjacent sets of double-wall drill rods being connected by a conversion joint, and the end of the last set of double-wall drill rods being fixedly connected to a double-wall drive rod via the conversion joint. A screw motor is installed inside the double-wall drive rod, and a transmission seat is coaxially arranged at the end of the double-wall drive rod, extending into the double-wall drive rod and fixedly connected to the screw motor. A flow control component for controlling the flow direction of the flushing fluid is installed inside the transmission seat, and a guide component is installed at the other end of the transmission seat, with the output end of the guide component connected to a drill bit.

[0008] The guide assembly includes a hinged ball head hinged to the center of the end of the transmission seat. A fixing post is integrally formed on the hinged ball head and fixedly installed on the drill bit. Four sets of hydraulic telescopic cylinders are arranged along the circumferential direction on the outer edge of the end face of the transmission seat. The end of each set of hydraulic telescopic cylinders is installed between the transmission seat and the drill bit through the ball head. A corrugated sleeve is encapsulated on the outer edge between the transmission seat and the drill bit.

[0009] Preferably, the double-walled drill rod has a through first central flow channel along the axis inside, a first internal annular flow channel is formed on one side of the outer edge of the double-walled drill rod, and a first guide channel communicating with the first internal annular flow channel is formed on both ends of the double-walled drill rod.

[0010] Preferably, the conversion joint includes a limiting ring sleeved on the outer wall of the double-wall drill rod and the double-wall drive rod, a limiting seat fixed on the inner wall of the limiting ring, a central flow channel being provided at the center of the limiting seat, and a second flow channel being uniformly provided along the circumferential direction on the outer edge of the limiting seat.

[0011] Preferably, the double-walled drive rod has a second central flow channel, a pressurizing flow channel and a flow channel arranged sequentially along the axis inside. A second internal annular flow channel is opened on one side of the outer edge of the double-walled drive rod, and a third guide channel communicating with the second internal annular flow channel is opened on the end face of the double-walled drill rod near the conversion joint. The flow channel and the second internal annular flow channel are connected by a bypass channel.

[0012] Preferably, the transmission base includes a transmission cylinder rotatably mounted inside the flow channel. One end of the transmission cylinder extending into the flow channel is fixedly connected to a screw motor. The other end of the transmission cylinder extends out a double-walled drive rod integrally formed with a drill cylinder. The hinged ball head is mounted on the drill cylinder, and four sets of hydraulic telescopic cylinders are evenly hinged to the end face of the drill cylinder through the ball head.

[0013] Preferably, an internal discharge channel is provided on the drill barrel at the position corresponding to the bypass channel, and an external discharge channel is provided on the drill barrel at the position corresponding to the gap between the double-wall drive rod and the transmission seat, and a pressure detection valve is fixedly installed in the external discharge channel.

[0014] Preferably, the screw motor includes a drive cylinder rotatably mounted inside the pressurization channel, and the outer side wall of the drive cylinder is uniformly provided with outer drive blades along the circumferential direction, the inner side wall of the drive cylinder is uniformly provided with inner drive blades along the circumferential direction, and the outer side wall of the drive cylinder is uniformly provided with guide grooves.

[0015] Preferably, the flow control component includes a plug head slidably mounted inside the transmission cylinder, a pressure plate slidably mounted inside the drill cylinder, the plug head and the pressure plate being connected by a connecting rod, a pressure spring being provided on the side of the pressure plate near the plug head, the other end of the pressure spring being fixed to the inner wall of the drill cylinder, and a transversely penetrating guide hole being provided on the plug head.

[0016] Preferably, the drill bit is provided with an underflow hole, and the articulated ball head is provided with a transverse fluid channel that connects the drill barrel and the underflow hole.

[0017] This invention discloses a drilling method for a coal seam floor with a thick layer of limestone prone to waterlogging. This method utilizes the drilling device described above for such areas. The specific steps of the drilling method are as follows:

[0018] S1: First, obtain the thickness of the aquifer to be modified, including the aquifer at the top of the coal seam and the aquifer at the bottom;

[0019] S2: Then drill exploration and treatment boreholes on the ground extending to the aquifer. The exploration and treatment boreholes include the straight section and the inclined section of the treatment borehole.

[0020] S3: Subsequently, based on the thickness of the aquifer to be modified, a branch section is drilled at the tail end of the inclined section of the treatment hole to achieve the initial treatment hole drilling of the aquifer. At the same time, an upward or downward reinforcing branch section is drilled independently at the location of the water inrush coefficient of the aquitard, so as to complete the design of the aquifer treatment hole distribution network. Then, the drill bit is controlled to carry out the drilling work according to the preset treatment hole distribution network.

[0021] S4: During normal drilling, the flushing fluid is introduced into the first central channel of the double-walled drill pipe through the dual-channel water feeder, and then flows into the second central channel through the guide central channel. As the orifice diameter of the pressurizing channel gradually decreases, the flushing fluid forms a pressurized force inside the pressurizing channel to drive the screw motor to rotate, thereby driving the transmission seat and drill bit to rotate synchronously. The flushing fluid after driving the screw motor to rotate is directly introduced into the transmission cylinder, and then flows into the drill barrel through the guide hole to realize the circulation of the flushing fluid. This facilitates the use of the flushing fluid to complete the rock drilling operation when the drill bit rotates. When drilling in the aquifer, the guide component is controlled to adjust the angle of the drill bit relative to the transmission seat, thereby achieving the guiding drive function according to the distribution network of treatment holes, changing the drilling direction of the drill bit, and increasing the drilling range of the drill bit.

[0022] The technical effects and advantages of this invention are as follows:

[0023] 1. This invention changes the traditional drill bit installation method by setting the drill bit and transmission seat as separate units. The drill bit can be rotated by using a hinged ball head, and the four sets of hydraulic telescopic cylinders can drive the drill bit and the hinged ball head to adjust the angle relative to the transmission seat by using their different extension lengths. This can adjust the drilling direction of the drill bit during drilling, greatly increasing the drilling range of the drilling device in the aquifer, improving the drilling range of the aquifer treatment holes, and making it more conducive to the design of the treatment hole distribution network. It is convenient to carry out targeted drilling for different water inrush coefficients on the aquitard, optimize the design structure of the treatment hole distribution network, enhance the support strength of the aquitard, and avoid the risk of water inrush.

[0024] 2. The high-pressure water gushing inside the borehole of this invention can constantly exert an impact force on the pressure detection valve. This pressure detection valve can detect the water pressure of the high-pressure water gushing inside the borehole, making it convenient to adjust the working state of the drill bit according to the water pressure inside the borehole. The tension of the pressure spring can directly detect the pressure value of the flushing fluid inside the transmission seat. In combination with the water pressure inside the borehole detected by the pressure detection valve, the upward return path of the flushing fluid can be changed. The working environment of the drill bit can be improved by the change of the high-pressure water gushing inside the borehole, so that the flushing fluid always circulates in a "low back pressure" state. By reducing the pressure loss of the flushing fluid circulation, the ineffective load of the mud pump can also be reduced, ensuring the bottom power of the drill bit and avoiding the high-pressure water gushing from creating great resistance at the bottom of the drill bit, which would prevent efficient rock breaking. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall first-view structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the overall second-view structure of the present invention;

[0027] Figure 3This is a schematic diagram of the overall first cross-sectional structure of the present invention;

[0028] Figure 4 This is a schematic diagram of the overall second cross-sectional structure of the present invention;

[0029] Figure 5 This is a schematic diagram of the double-walled drill pipe structure of the present invention;

[0030] Figure 6 This is a schematic diagram of the adapter structure of the present invention;

[0031] Figure 7 This is a schematic diagram of the double-walled drive rod structure of the present invention;

[0032] Figure 8 This is a schematic diagram of the assembly structure of the screw motor, transmission base, and drill bit of the present invention;

[0033] Figure 9 This is a cross-sectional view of the screw motor, transmission base, and drill bit assembly of the present invention.

[0034] In the diagram: 1. Double-walled drill pipe; 11. First central flow channel; 12. First internal annular flow channel; 13. First guide channel; 2. Converter joint; 21. Limiting ring; 22. Limiting seat; 23. Guide central flow channel; 24. Second guide channel; 3. Double-walled drive rod; 31. Second central flow channel; 32. Pressure boosting flow channel; 33. Flow channel; 34. Second internal annular flow channel; 35. Bypass channel; 36. Third guide channel; 4. Screw motor; 41. 42. Drive cylinder; 43. External drive blade; 44. Internal drive blade; 5. Guide groove; 6. Transmission seat; 51. Transmission cylinder; 52. Drill barrel; 53. External discharge channel; 54. Pressure detection valve; 55. Internal discharge channel; 6. Flow direction control component; 61. Sealing head; 62. Connecting rod; 63. Pressure plate; 64. Pressure spring; 65. Guide hole; 7. Guide component; 71. Hinged ball head; 72. Hydraulic telescopic cylinder; 73. Corrugated sleeve; 8. Drill bit. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example

[0036] This embodiment provides, for example Figures 1 to 9The drilling device shown is for a coal seam floor in a thick layer of limestone prone to waterlogging. It includes several sets of identical double-wall drill rods 1. The number of double-wall drill rods 1 can be increased according to actual drilling needs. Adjacent sets of double-wall drill rods 1 are connected by adapter joints 2. The last set of double-wall drill rods 1 is fixedly connected to a double-wall drive rod 3 at its end via adapter joint 2, which increases connection stability and ensures effective transmission. The double-wall drive rod 3 is equipped with a screw motor 4. When flushing fluid is introduced into the double-wall drill rod 1, the flushing fluid... The flow of fluid can drive the screw motor 4 to rotate. The double-walled drive rod 3 has a transmission seat 5 arranged coaxially at its end. The transmission seat 5 extends into the double-walled drive rod 3 and is fixedly connected to the screw motor 4. When the screw motor 4 rotates, it can drive the transmission seat 5 to rotate synchronously. The transmission seat 5 is equipped with a flow direction control component 6 to control the flow direction of the flushing fluid. The other end of the transmission seat 5 is equipped with a guide component 7. The output end of the guide component 7 is connected to the drill bit 8. The transmission seat 5 can drive the drill bit 8 to rotate synchronously through the guide component 7 to realize the drilling work.

[0037] Please see Figure 3 and Figure 9 The guide assembly 7 includes a hinged ball head 71 hingedly mounted at the center of the end of the transmission seat 5. A fixing post is integrally formed on the hinged ball head 71 and is fixedly mounted on the drill bit 8. Four sets of hydraulic telescopic cylinders 72 are arranged along the circumferential direction on the outer edge of the end face of the transmission seat 5. The end of each set of hydraulic telescopic cylinders 72 is installed between the transmission seat 5 and the drill bit 8 through the ball head. A corrugated sleeve 73 is encapsulated on the outer edge between the transmission seat 5 and the drill bit 8.

[0038] This design departs from the traditional drill bit installation method, setting the drill bit 8 and transmission seat 5 as separate units. The drill bit 8 can be rotated by the hinged ball head 71, and the four sets of hydraulic telescopic cylinders 72 can drive the drill bit 8 and the hinged ball head 71 to adjust the angle relative to the transmission seat 5 by using their different extension lengths. This allows the drilling direction of the drill bit 8 during drilling operations to be adjusted, greatly increasing the drilling range of the drilling device in the aquifer, improving the drilling range of the aquifer treatment holes, and making it more conducive to the design of the treatment hole distribution network. It facilitates targeted drilling for different water inrush coefficients on the aquitard, optimizes the design structure of the treatment hole distribution network, enhances the support strength of the aquitard, and avoids the risk of water inrush.

[0039] It should be noted that the purpose of the corrugated sleeve 73 is to protect the drill bit 8 and the transmission seat 5, to achieve a sealing function, and at the same time, to provide room for the drill bit 8 to adjust its angle relative to the transmission seat 5, so as to facilitate the adjustment of the drill bit 8 angle.

[0040] Please see Figure 5The double-walled drill rod 1 has a first central flow channel 11 that runs through the center line inside, and a first internal annular flow channel 12 that runs through the outer edge of the double-walled drill rod 1. Both ends of the double-walled drill rod 1 have a first guide channel 13 that communicates with the first internal annular flow channel 12.

[0041] Please see Figure 6 The conversion connector 2 includes a limiting ring 21 sleeved on the outer wall of the double-wall drill rod 1 and the double-wall drive rod 3. A limiting seat 22 is fixed on the inner wall of the limiting ring 21. A flow guiding center channel 23 is opened at the center of the limiting seat 22. A second flow guiding channel 24 is evenly opened along the circumferential direction on the outer edge of the limiting seat 22. The limiting seat 22 is installed between the two sets of double-wall drill rods 1 or between the double-wall drill rod 1 and the double-wall drive rod 3. The limiting ring 21 is sleeved and installed between the two sets of double-wall drill rods 1 or between the double-wall drill rod 1 and the double-wall drive rod 3 to enhance the stability when installing the two sets of double-wall drill rods 1 or the double-wall drill rod 1 and the double-wall drive rod 3.

[0042] Please see Figure 7 The double-walled drive rod 3 has a second central flow channel 31, a pressurizing flow channel 32 and a flow channel 33 arranged sequentially along the axis inside. The double-walled drive rod 3 has a second internal annular flow channel 34 on one side of its inner outer edge. The double-walled drill rod 1 has a third guide channel 36 on the end face of the side near the conversion joint 2 that communicates with the second internal annular flow channel 34. The flow channel 33 and the second internal annular flow channel 34 are connected by a bypass channel 35.

[0043] Please see Figure 8 and Figure 9 The transmission base 5 includes a transmission cylinder 51 rotatably mounted inside the flow channel 33. One end of the transmission cylinder 51 extends into the flow channel 33 and is fixedly connected to the screw motor 4. The other end of the transmission cylinder 51 extends out a double-walled drive rod 3 integrally formed with a drill barrel 52. A hinged ball head 71 is mounted on the drill barrel 52. Four sets of hydraulic telescopic cylinders 72 are evenly hinged on the end face of the drill barrel 52 through the ball head.

[0044] When the screw motor 4 rotates, it can synchronously drive the drill bit 8 to rotate, thus completing the drilling work.

[0045] Please see Figure 8 and Figure 9 An internal discharge channel 55 is provided on the drill barrel 52 at the position corresponding to the bypass channel 35. An external discharge channel 53 is provided on the drill barrel 52 at the position corresponding to the gap between the double-wall drive rod 3 and the transmission seat 5. A pressure detection valve 54 is fixedly installed in the external discharge channel 53. Since the external discharge channel 53 is always connected to the borehole, the high-pressure water in the borehole can always generate an impact force on the pressure detection valve 54. In this way, the pressure of the high-pressure water in the borehole can be detected by the pressure detection valve 54, which is denoted as M2. It is convenient to adjust the working state of the drill bit 8 according to the water pressure in the borehole.

[0046] Please see Figure 8 The screw motor 4 includes a drive cylinder 41 rotatably mounted inside the pressurization channel 32. External drive blades 42 are evenly arranged along the circumferential direction on the outer side wall of the drive cylinder 41, and internal drive blades 43 are evenly arranged along the circumferential direction on the inner side wall of the drive cylinder 41. Guide grooves 44 are evenly opened on the outer side wall of the drive cylinder 41. The flow of flushing fluid inside the double-wall drive rod 3 can generate flow pressure. The fluid pressure drives the external drive blades 42 and the internal drive blades 43 to rotate, which in turn drives the screw motor 4 to rotate, forming the driving force of the drill bit 8. This realizes the conversion of fluid pressure energy into rotational mechanical energy, thereby achieving directional drilling.

[0047] Please see Figure 9 The flow control component 6 includes a plug head 61 slidably mounted inside the transmission cylinder 51, a pressure plate 63 slidably mounted inside the drill barrel 52, the plug head 61 and the pressure plate 63 are connected by a connecting rod 62, a pressure spring 64 is provided on the side of the pressure plate 63 near the plug head 61, the other end of the pressure spring 64 is fixed on the inner wall of the drill barrel 52, and a transverse through-hole 65 is provided on the plug head 61.

[0048] The flushing fluid after the drive screw motor 4 rotates will be directly introduced into the transmission cylinder 51, and then flow into the drill barrel 52 through the guide hole 65, thus realizing the flow of flushing fluid.

[0049] The drill bit 8 is provided with a bottom flow hole, and the hinged ball head 71 is provided with a transverse fluid channel that connects the drill barrel 52 and the bottom flow hole. This ensures that the flushing fluid flowing from the inside can be introduced into the bottom flow hole through the fluid channel and sprayed out. With the rotation of the drill bit 8, directional drilling is achieved. Then the flushing fluid merges with the formation water and returns from the borehole.

[0050] During normal drilling, drill bit 8 performs drilling work according to the preset distribution network of treatment holes. First, it obtains the thickness of the aquifer to be modified, including the top and bottom aquifers of the coal seam. Then, it drills exploratory treatment holes extending to the aquifer on the ground. The exploratory treatment holes include the straight section and the inclined section of the treatment hole. Subsequently, according to the thickness of the aquifer to be modified, it drills a branch section at the end of the inclined section of the treatment hole to achieve the initial treatment hole drilling of the aquifer. At the same time, it independently drills upward or downward reinforcing branch sections at locations with a large water inrush coefficient in the aquitard.

[0051] It is worth noting that when the branch section is close to the upper part of the aquifer, several downward-sloping secondary branch sections are equally spaced along the length of the branch section, and the tail end of the secondary branch section is close to the lower part of the aquifer. In the middle of the branch section, an upward-sloping exploration branch section is opened, and the exploration branch section extends a distance beyond the upper part of the aquifer.

[0052] When the branch section is close to the lower part of the aquifer, several upwardly inclined secondary branch sections are equally spaced along the length of the branch section, and the tail end of the secondary branch section is located in the lower part of the aquifer.

[0053] It is worth noting that when drilling the straight section, directional section, branch section, secondary branch section, and exploration branch section of the treatment hole within the aquifer, the guide component 7 is activated to adjust the angle of the drill bit 8 relative to the transmission seat 5. This achieves the guiding and driving function according to the distribution network of treatment holes, changes the drilling direction of the drill bit 8, and increases the drilling range of the drill bit 8. The drilling strategy can be adjusted accordingly based on the changes in the water inrush coefficient of the top and bottom aquitards in the coal seam, thus achieving a corresponding distribution of the treatment hole network.

[0054] When drilling the reinforced branch section inside the aquifer, the four sets of hydraulic telescopic cylinders 72 can drive the drill bit 8 and the hinged ball head 71 to adjust the angle relative to the transmission seat 5 by utilizing their different extension lengths. This greatly increases the drilling range of the drilling device in the aquifer, improves the drilling range of the aquifer treatment holes, and is more conducive to the design of the treatment hole distribution network. It facilitates targeted drilling for different water inrush coefficients on the aquitard, optimizes the design structure of the treatment hole distribution network, enhances the support strength of the aquitard, and avoids the risk of water inrush.

[0055] It should be noted that as the water flow in the borehole increases, the water pressure also gradually increases. This causes the resistance to the backflow of the flushing fluid ejected from the drill bit 8 to gradually increase, resulting in an increase in the flushing fluid pressure inside the transmission seat 5, which directly leads to an increase in the output power consumption of the mud pump.

[0056] In actual use, after drill bit 8 reaches the high-pressure water-bearing formation at the bottom plate, a large amount of high-pressure formation water rushes into the borehole under the action of pressure difference (formation pore pressure is greater than the circulating flow pressure of flushing fluid in the hole). This increases the annular return water volume and flow velocity, leading to increased resistance to the circulating flow of flushing fluid and increased bottom hole pressure (back pressure). This directly affects the pressure energy conversion of flushing fluid, and thus affects the working performance of drill bit 8 at the bottom of the hole. Especially when the formation water inflow pressure reaches 3MPa to 4MPa, directional drilling becomes difficult. This is manifested in increased annular return water volume, increased bottom hole back pressure, significantly increased mud pump supply pressure, reduced output torque of bottom hole power drill, significantly reduced mechanical drilling speed, and difficulty in directional drilling. Therefore, under high-pressure formation water inflow conditions, directional drilling with top water is difficult, the hole depth often fails to meet design requirements, the water control effect is poor, and additional drilling work is required, resulting in high costs and long cycles.

[0057] It should be noted that when the flushing fluid pressure inside the transmission seat 5 increases, the pressure spring 64 is stretched as the pressure plate 63 moves. Therefore, the amount of stretching of the pressure spring 64 can directly detect the flushing fluid pressure inside the transmission seat 5. Combined with the borehole water pressure detected by the pressure detection valve, the upward return path of the flushing fluid is changed. The working environment of the drill bit 8 can be improved by the change of high-pressure water in the borehole, so that the flushing fluid always circulates in a "low back pressure" state. By reducing the pressure loss of the flushing fluid circulation, the ineffective load of the mud pump can also be reduced, ensuring the bottom power of the drill bit 8 and avoiding the large resistance of high-pressure water in the bottom of the drill bit, which would prevent efficient rock breaking.

[0058] Based on this, the flushing fluid is introduced into the first central channel 11 of the double-walled drill pipe 1 through the dual-channel water feeder, and then flows into the second central channel 31 through the guide central channel 23. As the aperture of the pressurizing channel 32 gradually decreases, the flushing fluid will form a pressurized force inside the pressurizing channel 32 to drive the screw motor 4 to rotate, thereby driving the transmission seat 5 and the drill bit 8 to rotate synchronously. The flushing fluid after driving the screw motor 4 to rotate will be directly introduced into the transmission cylinder 51, and then flow into the drill barrel 52 through the guide flow hole 65, which can realize the flow of flushing fluid and facilitate the use of flushing fluid to complete the rock drilling operation when the drill bit 8 rotates. The fluid pressure introduced from the screw motor 4 into the transmission seat 5 can be calculated by the tensile deformation of the pressure spring 64, denoted as M1, specifically:

[0059] When the internal pressure M1 of the transmission seat 5 is much greater than the water pressure M2 in the borehole, the drilling is characterized as a low back pressure condition. At this time, because the plugging head 61 blocks the internal discharge channel 55 and the pressure detection valve is opened, some flushing fluid flows into the borehole through the external discharge channel 53. In this way, the flushing fluid will merge with the formation water in the borehole and return from the borehole.

[0060] When the internal pressure M1 of the transmission seat 5 is greater than and close to the water inflow pressure M2 in the borehole, the drilling is characterized as a medium back pressure condition. At this time, the pressure detection valve is closed, and the flushing fluid will not flow out through the external discharge channel 53. Instead, the flushing fluid will flow through the transmission seat 5 and the drill bit 8 and be introduced into the bottom of the hole. This is to overcome the problem of increased back pressure caused by the increase in water inflow pressure in the borehole. The flushing fluid circulation resistance is reduced by increasing the flushing fluid flow pressure. Subsequently, the flushing fluid and the formation water in the borehole merge and return from the borehole. At this time, the flushing fluid return flow rate increases, and the flow velocity also increases.

[0061] When the internal pressure M1 of the transmission seat 5 is less than the water inflow pressure M2 in the borehole, drilling is characterized as a high back pressure condition. At this time, the flow resistance of the flushing fluid increases significantly, causing the flushing fluid pressure inside the transmission cylinder 51 to gradually increase. This pushes the pressure plate 63 to move, causing the pressure spring 64 to stretch. As the pressure plate 63 moves, the connecting rod 62 pushes the sealing head 61 downwards within the transmission cylinder 51, thus misaligning the sealing head 61 with the inner discharge channel 55. This opens the inner discharge channel 55, allowing the flushing fluid inside the transmission seat 5 to flow into the bypass channel 35 along the inner discharge channel 55. The flushing fluid flows along the second internal annular flow channel 34, the third guide channel 36, the second guide channel 24, and the first internal annular flow channel 12, achieving upward return of the flushing fluid. The pressure detection valve is closed, so the flushing fluid will not flow into the borehole from the external discharge channel 53. Thus, the upward return of the flushing fluid will not be affected by the water pressure inside the borehole. Therefore, the drilling device can adjust the upward return path of the flushing fluid in real time according to the changes in the water pressure inside the borehole when drilling, thereby ensuring that the flushing fluid inside the drilling device always flows under a low back pressure state. This can reduce the load on the mud pump and significantly improve the drilling efficiency of the drilling device. Example

[0062] This embodiment provides a drilling method for a coal seam floor with a thick layer of limestone prone to waterlogging. This method utilizes the drilling device for a coal seam floor with a thick layer of limestone prone to waterlogging as described in Embodiment 1. The specific steps of the drilling method are as follows:

[0063] S1: First, obtain the thickness of the aquifer to be modified, including the aquifer at the top of the coal seam and the aquifer at the bottom;

[0064] S2: Then drill exploration and treatment boreholes on the ground extending to the aquifer. The exploration and treatment boreholes include the straight section and the inclined section of the treatment borehole.

[0065] S3: Subsequently, based on the thickness of the aquifer to be modified, a branch section is drilled at the tail end of the inclined section of the treatment hole to achieve the initial treatment hole drilling of the aquifer. At the same time, an upward or downward reinforcing branch section is drilled independently at the location of the water inrush coefficient of the aquitard, so as to complete the design of the aquifer treatment hole distribution network. Then, the drill bit 8 is controlled to carry out the drilling work according to the preset treatment hole distribution network.

[0066] S4: During normal drilling, the flushing fluid is introduced into the first central channel 11 of the double-walled drill pipe 1 through the dual-channel water feeder, and then flows into the second central channel 31 through the guide central channel 23. As the diameter of the pressurizing channel 32 gradually decreases, the flushing fluid forms a pressurized force inside the pressurizing channel 32 to drive the screw motor 4 to rotate, thereby driving the transmission seat 5 and the drill bit 8 to rotate synchronously. The flushing fluid after driving the screw motor 4 to rotate is directly introduced into the transmission cylinder 51, and then flows into the drill barrel 52 through the guide flow hole 65 to realize the flow of flushing fluid. This facilitates the use of flushing fluid to complete the rock drilling operation when the drill bit 8 rotates. When drilling in the aquifer, the guide component 7 is controlled to move, driving the drill bit 8 to adjust the angle relative to the transmission seat 5, thereby achieving the guiding drive function according to the distribution network of treatment holes, changing the drilling direction of the drill bit 8, and increasing the drilling range of the drill bit 8.

[0067] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A drilling device for a coal seam floor in a water-prone area with a thick layer of limestone, comprising several sets of identical double-walled drill rods (1), characterized in that: Two adjacent sets of double-wall drill rods (1) are connected by a conversion joint (2), and the end of the last set of double-wall drill rods (1) is fixedly connected to a double-wall drive rod (3) by a conversion joint (2). The double-wall drive rod (3) is equipped with a screw motor (4). The end of the double-wall drive rod (3) is provided with a transmission seat (5) on the coaxial center line. The transmission seat (5) extends into the double-wall drive rod (3) and is fixedly connected to the screw motor (4). The transmission seat (5) is equipped with a flow direction control component (6) for controlling the flow direction of the flushing fluid. The other end of the transmission seat (5) is equipped with a guide component (7). The output end of the guide component (7) is connected to a drill bit (8). The guide assembly (7) includes a hinged ball head (71) hingedly assembled at the center of the end of the transmission seat (5). A fixing post is integrally formed on the hinged ball head (71), and the fixing post is fixedly installed on the drill bit (8). Four sets of hydraulic telescopic cylinders (72) are arranged along the circumferential direction on the outer edge of the end face of the transmission seat (5). The end of each set of hydraulic telescopic cylinders (72) is installed between the transmission seat (5) and the drill bit (8) through the ball head. A corrugated sleeve (73) is encapsulated on the outer edge between the transmission seat (5) and the drill bit (8). The double-walled drill rod (1) has a through first central flow channel (11) along the axis inside, and a first internal annular flow channel (12) is opened on one side of the outer edge inside the double-walled drill rod (1). The double-walled drill rod (1) also has a first guide channel (13) that communicates with the first internal annular flow channel (12) on both ends of the double-walled drill rod (1). The conversion connector (2) includes a limiting ring (21) sleeved on the outer wall of the double-wall drill rod (1) and the double-wall drive rod (3). A limiting seat (22) is fixed on the inner wall of the limiting ring (21). A flow guiding center channel (23) is opened at the center of the limiting seat (22). A second flow guiding channel (24) is evenly opened along the circumferential direction on the outer edge of the limiting seat (22). The transmission base (5) includes a transmission cylinder (51) rotatably mounted inside the flow channel (33). One end of the transmission cylinder (51) extends into the flow channel (33) and is fixedly connected to the screw motor (4). One end of the transmission cylinder (51) extends out a double-walled drive rod (3) and is integrally formed with a drill cylinder (52). An internal discharge channel (55) is provided on the drill barrel (52) at the position corresponding to the bypass channel (35), and an external discharge channel (53) is provided on the drill barrel (52) at the position corresponding to the gap between the double-wall drive rod (3) and the transmission seat (5). A pressure detection valve (54) is fixedly installed in the external discharge channel (53). The flow control component (6) includes a plug head (61) slidably mounted inside the transmission cylinder (51), a pressure plate (63) slidably mounted inside the drill barrel (52), the plug head (61) and the pressure plate (63) are connected by a connecting rod (62), a pressure spring (64) is provided on the side of the pressure plate (63) near the plug head (61), the other end of the pressure spring (64) is fixed on the inner wall of the drill barrel (52), and a transverse through-hole (65) is provided on the plug head (61).

2. The drilling device for water-prone areas of thick limestone layers in the coal seam floor according to claim 1, characterized in that: The double-wall drive rod (3) has a second central flow channel (31), a pressurizing flow channel (32) and a flow channel (33) arranged sequentially along the axis. The double-wall drive rod (3) has a second internal annular flow channel (34) on one side of its inner outer edge. The double-wall drill rod (1) has a third guide channel (36) connected to the second internal annular flow channel (34) on one end face near the conversion joint (2). The flow channel (33) and the second internal annular flow channel (34) are connected by a bypass channel (35).

3. The drilling device for water-prone areas of thick limestone layers in the coal seam floor according to claim 2, characterized in that: The hinged ball head (71) is mounted on the drill barrel (52), and four sets of hydraulic telescopic cylinders (72) are evenly hinged on the end face of the drill barrel (52) through the hinged ball head.

4. The drilling device for water-prone areas of thick limestone layers in the coal seam floor as described in claim 3, characterized in that: The screw motor (4) includes a drive cylinder (41) rotatably mounted inside the pressurization channel (32), and the outer side wall of the drive cylinder (41) is uniformly provided with outer drive blades (42) along the circumferential direction, the inner side wall of the drive cylinder (41) is uniformly provided with inner drive blades (43) along the circumferential direction, and the outer side wall of the drive cylinder (41) is uniformly provided with guide grooves (44).

5. The drilling device for water-prone areas of thick limestone layers in the coal seam floor according to claim 4, characterized in that: The drill bit (8) is provided with an underflow hole, and the articulated ball head (71) is provided with a transverse fluid channel that connects the drill barrel (52) and the underflow hole.

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