An integrated system and method for non-submerged hydraulic cavity creation and slag removal in downhole drilling

Abstract

This invention discloses an integrated system and method for non-submerged hydraulic cavity creation and slag removal in downhole drilling. The system includes a hydraulic cavity creation unit and a pump-suction slag removal unit. The hydraulic cavity creation unit includes a coal-breaking drill bit, a high-low pressure conversion device, a jet device, a double-wall drill rod, a double-channel tailpipe, a drilling rig, and a high-pressure water pump. The pump-suction slag removal unit includes a borehole sealing device and a axial jet pump. This synergistic conveying, drainage, pressure relief, and permeability enhancement system for hydraulic cavity creation in downhole drilling can fully utilize the shear disturbance generated by the rotation of the drill rod and the pulsating flow field formed by the high-pressure water jet during the cavity creation stage to continuously break, suspend, and discharge coal particles in the borehole. It achieves simultaneous hydraulic cavity creation and synergistic conveying and drainage of coal particles, fundamentally eliminating particle deposition and consolidation problems, improving the stability and pressure relief and permeability enhancement effect of downhole cavity creation, and realizing an integrated gas-enhanced extraction process of cavity creation and conveying and drainage. It is particularly suitable for hydraulic cavity creation, pressure relief, and permeability enhancement in downhole drilling of inclined coal seams.

Description

Technical Field

[0001] This invention relates to a hydraulic cavity-forming system and method, specifically an integrated system and method for non-submerged hydraulic cavity-forming and slag removal in downward drilling, belonging to the field of coal mine gas control technology. Background Technology

[0002] In coal mining, gas drainage is the final crucial measure to reduce the risk of coal seam gas disasters and a vital link in achieving safe and efficient mine production. Coal seams in my country are generally low-permeability, with poor gas migration conditions and significant drainage challenges. To improve coal seam permeability and enhance gas drainage effectiveness, hydraulic cavity drilling technology, as an effective means of strengthening gas drainage, has been widely applied in many mining areas. This technology uses high-pressure water jets to create larger cavities around the borehole, significantly improving the stress state and fracture structure of the coal seam, thereby achieving pressure relief, increased permeability, and promoting gas desorption and drainage.

[0003] In practical applications, the upward drilling hydraulic cavity-making process has shown good results. During the cavity-making process, broken coal particles can be naturally discharged by gravity under the action of water flow, keeping the cavity unobstructed and forming a large cavity structure. This not only improves the stress distribution of the coal body but also significantly enhances the local pressure relief and permeability enhancement effects, thereby improving gas extraction efficiency.

[0004] However, during the drilling construction of this coal seam, due to the limitations of the coal seam dip angle and borehole layout, it is difficult to achieve effective coverage of the coal seam dip direction by simply relying on upward drilling for hydraulic cavity creation. In engineering practice, it is usually necessary to carry out counter-drilling in the intake and return airway to achieve full coverage of the coal seam dip direction. Therefore, downward drilling for hydraulic cavity creation is the inevitable choice for enhanced gas extraction in this coal seam.

[0005] Currently, conventional down-drilling cavity creation typically employs a "cavitation-slag removal step-by-step" process. This involves first creating the cavity using high-pressure water jets, followed by backwashing or injection to remove accumulated slag. However, this process has significant limitations: Firstly, because it's down-drilling, the bottom of the borehole is inevitably filled with water during the cavity creation phase, rendering the high-pressure water jet submerged and significantly reducing its cavity-creating capacity. Secondly, there's a time lag between cavity creation and slag removal, during which broken coal particles remain at the bottom of the borehole for an extended period, easily depositing and solidifying in a high-moisture, low-flow-velocity environment. Thirdly, the subsequent backwashing process lacks effective disturbance to the deposited particles, making complete resuspension and removal difficult. In practice, what is actually discharged is mostly coal-bearing water rather than the coal particles themselves, leaving a large amount of coal particles trapped inside the borehole. The aforementioned problems result in limited space for downward drilling to create cavity, and the gradual formation of a solidified blockage zone inside the borehole, which hinders the formation and connection of gas flow channels, significantly reducing the pressure relief and permeability enhancement effect, thus severely restricting the promotion and application of downward drilling hydraulic cavity creation technology.

[0006] Therefore, there is an urgent need to develop a pressure relief and permeability enhancement system and method that can simultaneously achieve non-submerged jet, efficient coal particle disturbance, and coordinated conveying and drainage during downhole drilling. This system should achieve non-submerged jet by injecting gas into the borehole during the cavity-building stage to control the bottom liquid level. Simultaneously, it should fully utilize the shear disturbance generated by drill pipe rotation and the pulsating flow field formed by high-pressure water jet to continuously break up, suspend, and discharge coal particles from the borehole, fundamentally eliminating particle deposition and consolidation problems, improving the stability and pressure relief / permeability enhancement effect of downhole drilling, and realizing an integrated gas extraction process combining cavity building and conveying / draining. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides an integrated system and method for non-submerged hydraulic cavity creation and slag removal in downhole drilling. When performing hydraulic cavity creation in downhole drilling, this method can improve the stability and pressure relief and permeability enhancement effect of downhole cavity creation by integrating non-submerged hydraulic cavity creation and slag removal through an air injection device, double-walled drill rod, and axial jet pump. It is particularly suitable for performing pressure relief and permeability enhancement in downhole hydraulic cavity creation in inclined coal seams.

[0008] To achieve the above objectives, the integrated system for non-submerged hydraulic cavity creation and slag removal in downhole drilling includes a hydraulic cavity creation unit and a pump-suction slag removal unit.

[0009] The hydraulic cavity-making unit includes a coal-breaking drill bit, a high-low pressure conversion device, a jetting device, double-walled drill rods, a dual-channel tailpipe, a drilling rig, and a high-pressure water pump. The double-walled drill rods consist of an inner and outer tube arranged coaxially. The annulus between the inner and outer tubes serves as a water conveyance channel, and the hollow inner cavity of the inner tube serves as a particulate matter conveying channel. Multiple double-walled drill rods are sequentially connected and coaxially mounted. The front end of the foremost double-walled drill rod is coaxially connected to the jetting device, and the rear end of the last double-walled drill rod is connected to the dual-channel tailpipe. The jetting device includes a double-tube base I and a jet nozzle. The double-tube base I is... The double-walled drill pipe is adapted to a double-pipe structure including a water conveying channel and a particulate matter conveying channel. The double-pipe base I includes an inner tube of a jet device. The jet nozzle is set in the radial direction along the double-pipe base I, and the input end of the jet nozzle is connected to the water conveying channel. A high-low pressure conversion device is coaxially installed in front of the jet device. A coal breaking drill bit is coaxially installed in front of the high-low pressure conversion device. The slag discharge port of the double-channel water tail is connected to the slag discharge pipe, and the pressure water input port of the double-channel water tail is sealed to the pressure water output port of the high-pressure water pump. The drilling rig is connected to the double-walled drill pipe via a drive.

[0010] The pump suction back-slag unit includes an orifice sealing device and a axial jet pump. The orifice sealing device includes a sealed box-shaped hollow cavity, a front sealing sleeve communicating with the front of the hollow cavity, a rear sealing sleeve communicating with the rear of the hollow cavity, an upper gas outlet communicating with the upper part of the hollow cavity, and a lower coal-water mixture outlet communicating with the lower part of the hollow cavity. The front and rear sealing sleeves are coaxially arranged. The annular space between the outer surface of the double-wall drill pipe and the inner surface of the front sealing sleeve serves as the drilling back-slag channel. The rear sealing sleeve is equipped with a sealing ring that matches the outer diameter of the double-wall drill pipe. A shut-off valve is installed on the lower coal-water mixture outlet. The upper gas outlet is connected to the gas extraction pipe; the axial jet pump is coaxially fixed between the jet device and the high-low pressure conversion device. The axial jet pump includes a double-pipe base II, which is a double-pipe structure including a water conveying channel and an inner pipe that is adapted to be connected to the jet device. The inner cavity of the inner pipe includes a throat section and a diffuser section from front to back. The front end of the throat section is connected to the rear end of the high-low pressure conversion device. The throat section is also provided with a coal suction pipe that is connected to it. The coal suction pipe is inclined forward and passes through the water conveying channel and is connected to the outside. The rear end of the diffuser section is connected to the particulate matter conveying channel of the inner pipe of the jet device.

[0011] As a further improvement of the present invention, the hydraulic cavity-forming unit also includes an air injection device disposed near the jet device. The air injection device includes a double-tube base III, an air injection pipe and an air injection nozzle. The double-tube base III is a double-tube structure that is adapted to be connected to the double-wall drill pipe and includes a water conveying channel and a particulate matter conveying channel. The air injection pipe can be disposed in the water conveying channel or the particulate matter conveying channel. The top end of the air injection pipe extends upward to the tail of the double channel and is connected to the air pump. The bottom end of the air injection pipe is connected to the air injection nozzle, which has the same structure as the jet nozzle. The air injection nozzle disposed on the double-tube base III penetrates the double-tube base III and the input end of the air injection nozzle is connected to the air injection pipe.

[0012] As a further improvement to the present invention, the diameter of the jet nozzle of the jet device is... and the injection pressure of the injection device Precise control can be achieved through the following formula:

[0013]

[0014] In the formula: The nozzle diameter of the throat section of the axial jet pump; The flow ratio of the axial jet pump is the ratio of the pumped flow rate to the operating flow rate. For fluid density; This is the total length of the double-walled drill pipe; The drilling angle; The pressure ratio of the axial jet pump is the pressure obtained by the suction fluid in the axial jet pump. Working pressure of axial jet pump The ratio; Atmospheric pressure; The friction coefficient of the inner tube of the double-walled drill pipe; The inner diameter of the double-walled drill pipe; This refers to the operating flow rate of the axial jet pump. The suction flow rate of the axial jet pump; The friction coefficient of the outer annulus of the double-walled drill pipe; The outer diameter of the double-walled drill pipe.

[0015] As a further improvement of the present invention, the jet nozzle of the jet device is disposed inside the double tube base I, the body of the jet nozzle penetrates the inner tube of the jet device along the radial direction of the double tube base I, and the body of the jet nozzle is sealed to the inner tube of the jet device.

[0016] As a further improvement of the present invention, the high-low pressure conversion device is a piston cylinder structure including a piston, a baffle seat, and a return spring. The rear end of the piston cylinder structure is connected to the water supply channel. The piston is slidably installed at the inner rear end of the piston cylinder structure, and the piston has a water inlet channel inside. Its water inlet hole is located on the side of the piston tail end, and the water outlet is located on the front end face of the piston. The baffle seat is positioned at the inner front end of the piston cylinder structure, and the baffle seat has a water passage hole that penetrates the baffle seat in the axial direction. The baffle seat also has a plug structure that extends backward at the position corresponding to the piston water outlet hole. The front and rear ends of the return spring abut against the rear end of the baffle seat and the front end of the piston, respectively. The drilling water jet channel in the coal breaking drill bit is connected to the water passage hole of the baffle seat of the high-low pressure conversion device.

[0017] As a further improvement of the present invention, a spiral drill rod is coaxially installed between the high-low pressure conversion device and the coal breaking drill bit, and the spiral drill rod is provided with a water passage that communicates with the high-low pressure conversion device and the coal breaking drill bit.

[0018] As a further improvement of the present invention, a back pressure valve with adjustable opening and closing pressure is provided on the upper gas outlet.

[0019] As a further improvement of the present invention, a turbulence nozzle connected to the water conveying channel is also provided between the jet device and the coal suction pipe.

[0020] An integrated method for non-submerged hydraulic cavity creation and slag removal based on an integrated system for downhole drilling includes the following steps:

[0021] a. Drilling operation: Using the drilling rig to drive the large-diameter coal-breaking drill bit to drill a hole in the coal wall to the set depth, the drill is withdrawn. The front sealing sleeve is lowered into the borehole and fixed. The hollow cavity and the rear sealing sleeve are coaxially and sealed on the front sealing sleeve. The lower coal-water mixture outlet is sealed to the slag discharge pipe, and the upper gas outlet is sealed to the gas extraction pipe. Then, the small-diameter coal-breaking drill bit is replaced, and the high-low pressure conversion device, the axial jet pump, the jet device, and the double-wall drill rod are installed in sequence and inserted into the rear sealing sleeve, the hollow cavity, and the front sealing sleeve. The drilling rig drives the coal-breaking drill bit to continue drilling downward to the first coal-breaking cavity section. During the drilling process, the high-pressure water pump supplies low-pressure water. The shut-off valve on the lower coal-water mixture outlet is in the open state. The slag returns to the hollow cavity through the annular gap between the double-wall drill rod and the borehole wall and the drilling slag return channel, and is discharged into the slag discharge pipe through the lower coal-water mixture outlet.

[0022] b. Hydraulic cavity creation: Close the shut-off valve at the outlet of the lower coal-water mixture, increase the pump pressure of the high-pressure water pump, and a portion of the high-pressure water is ejected through the jet nozzle of the jet device to form a high-pressure water jet for hydraulic cavity creation. The other portion of the high-pressure water continues to be transported forward to the high-low pressure conversion device, which is then converted to a high-pressure state. The front end of the throat section of the axial jet pump is connected to the water conveying channel. The high-pressure water enters the throat section of the axial jet pump to increase the pressure jet and enters the particle conveying channel of the double-wall drill rod through the diffuser section. At the same time, a negative pressure is formed in the coal suction pipe. Coal particles enter the particle conveying channel of the double-wall drill rod through the coal suction pipe and are finally discharged from the slag discharge port of the double-channel tail. The gas in the cavity is discharged into the gas extraction pipe through the upper gas discharge port. Control the drilling rig to drive the double-wall drill rod to rotate and reciprocate within the set range.

[0023] After the hydraulic cavity-making operation of the first coal-breaking cavity-making section is completed, the pump pressure of the high-pressure water pump is reduced, the high-low pressure conversion device is reset to the low-pressure state, and the drilling rig drives the coal-breaking drill bit to continue drilling downward to the second hydraulic cavity-making section, and the above hydraulic cavity-making operation is repeated.

[0024] This process is repeated to complete the hydraulic cavity-making operation for all coal-breaking and cavity-making sections.

[0025] As a further improvement of the present invention, after several cycles of cavity-making operations are completed in a single borehole, the pressure water inlet of the dual-channel water tail can be switched to be connected to the pressure gas pipeline. By injecting pressure gas into the cavity, the coal-water mixture remaining in the borehole can be forced out through the particulate matter conveying channel.

[0026] Compared with existing technologies, the integrated system and method of non-submerged hydraulic cavity creation and slag removal in downward drilling for coal seam decompression and permeability enhancement eliminates the need for slag removal after hydraulic cavity creation, enabling simultaneous hydraulic cavity creation and coal particle transport and discharge, thus shortening the single-hole operation time. Secondly, the gas injection device enables high-pressure water jets to create cavities in a non-submerged state, increasing the hydraulic cavity creation radius of the downward drilling and ensuring the coal seam decompression and permeability enhancement effect of the hydraulic cavity creation process. Furthermore, the use of a axial jet pump to extract coal particles from the borehole and hydraulically lift them out of the hole effectively removes the coal particles, reducing gas flow resistance in the downward drilling, improving gas extraction efficiency, and shortening the time required for gas extraction to reach the required standard at the working face. In addition, the coal-water mixture after backfilling at the dual-channel tail end can be separated, and the separated water can be recycled back into the system, reducing water consumption in hydraulic cavity creation operations. This method is simple in process, easy to operate, and has reliable equipment. It can simultaneously achieve efficient disturbance and coordinated conveying and drainage of coal particles during the non-submerged hydraulic cavity creation process of downward drilling, improve the efficiency of borehole gas extraction, shorten the extraction time to meet the standards of the working face, and ensure the safe and efficient mining of the longwall face, with significant economic benefits. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure for downward drilling hydraulic cavity creation according to the present invention;

[0028] Figure 2 This is a schematic diagram of the working position of the in-hole jet device and the coal suction pipe within the range of 0 to 600 mm in an embodiment of the present invention, wherein (a) is the initial working state of the in-hole jet device and the coal suction pipe, and (b) is the working state of the in-hole jet device and the coal suction pipe when the in-hole jet device is advanced to 600 mm.

[0029] Figure 3 This is a schematic diagram of the working position of the in-hole jet device and the coal suction pipe within the range of 600-1000mm in the embodiment of the present invention. (a) shows the working state of the in-hole jet device and the coal suction pipe when the in-hole jet device advances 1000mm, and (b) shows the working state of the in-hole jet device and the coal suction pipe when the in-hole jet device retracts to the 0mm position.

[0030] Figure 4 This is a schematic diagram of the working position of the in-hole jet device and the coal suction pipe within the range of 1000-1200mm in the embodiment of the present invention. (a) shows the working state of the in-hole jet device and the coal suction pipe when the in-hole jet device advances 1200mm, and (b) shows the working state of the in-hole jet device and the coal suction pipe when the in-hole jet device retracts to the 0mm position.

[0031] Figure 5 This is a schematic diagram of the internal structure of the high-low pressure conversion device in the hydraulic cavity-forming unit of the present invention.

[0032] In the diagram: 1. Hydraulic cavity-making unit; 1-1. Drilling rig; 1-2. Dual-channel tailpipe; 1-3. High-pressure water pump; 1-4. Double-walled drill rod; 1-5. Jet device; 1-6. Inner tube of jet device; 1-7. High-low pressure conversion device; 1-7-1. Piston; 1-7-2. Return spring; 1-7-3. Baffle seat; 1-8. Coal breaking drill bit; 2. Pump suction and slag backing unit; 2-1. Orifice sealing device; 2-1-1. Hollow cavity; 2-1-2. Front sealing sleeve; 2-1-3. Rear sealing sleeve; 2-1-4. Upper gas outlet; 2-1-5. Lower coal-water mixture outlet; 2-2. Coal suction pipe; 2-3. Shaft jet pump; 3. Gas extraction pipe; 4. Slag discharge pipe; 5. Spiral drill rod. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments (the following description is based on the drilling direction).

[0034] This integrated system for non-submerged hydraulic cavity creation and slag removal in downward drilling includes a hydraulic cavity creation unit 1 and a pump suction slag removal unit 2.

[0035] like Figure 1 As shown, the hydraulic cavity-creating unit 1 includes a coal-breaking drill bit 1-8, a high-low pressure conversion device 1-7, a jet device 1-5, a double-walled drill rod 1-4, a dual-channel water jet tail 1-2, a drilling rig 1-1, and a high-pressure water pump 1-3. The double-walled drill rod 1-4 includes an inner tube and an outer tube arranged coaxially. The annulus between the inner and outer tubes is a water conveying channel, and the hollow inner cavity of the inner tube is a particle conveying and discharging channel. Adjacent double-walled drill rods 1-4 are connected by a threaded seal. The front end of the foremost double-walled drill rod 1-4 is coaxially connected to the jet device 1-5, and the rear end of the last double-walled drill rod 1-4 is connected to the dual-channel water jet tail 1-2. The jet device 1-5 is used to spray high-pressure water jets for hydraulic cavity creation. The jet device 1-5 includes a double-tube base I and a jet spray nozzle. The nozzle, the double-tube base I, is a double-tube structure including a water conveying channel and a particulate matter conveying channel that is adapted to be connected to the double-walled drill rod 1-4. The double-tube base I includes the inner tube 1-6 of the jet device. The jet nozzle's spray direction is set along the radial direction of the double-tube base I, and the input end of the jet nozzle is connected to the water conveying channel. To avoid damage to the jet nozzle during drilling, the jet nozzle can be set inside the double-tube base I, that is, the body of the jet nozzle penetrates through the inner tube 1-6 of the jet device along the radial direction of the double-tube base I, and the body of the jet nozzle is sealed to the inner tube 1-6 of the jet device. The high-low pressure conversion device 1-7 is coaxially installed in front of the jet device 1-5. The high-low pressure conversion device 1-7 is used to adjust the working state of the hydraulic cavity-making unit 1, such as... Figure 5As shown, the high-low pressure conversion device 1-7 is a piston cylinder structure including a piston 1-7-1, a baffle seat 1-7-3, and a return spring 1-7-2. The rear end of the piston cylinder structure is connected to the water supply channel. The piston 1-7-1 is slidably installed on the inner rear end of the piston cylinder structure, and the piston 1-7-1 has a water inlet channel inside. Its water inlet hole is located on the side of the tail end of the piston 1-7-1, and its water outlet is located on the front end face of the piston 1-7-1. The baffle seat 1-7-3 is positioned on the inner front end of the piston cylinder structure, and the baffle seat 1-7-3 has a water passage hole that penetrates the baffle seat 1-7-3 in the axial direction. The baffle seat 1-7-3 also has a rearward-facing water passage hole at the position corresponding to the water inlet hole of the piston 1-7-1. The plug structure extends outwards, and the front and rear ends of the return spring 1-7-2 abut against the rear end of the baffle seat 1-7-3 and the front end of the piston 1-7-1, respectively. The high-low pressure conversion device 1-7 is existing technology and will not be described in detail here. The coal breaking drill bit 1-8 is coaxially installed in front of the high-low pressure conversion device 1-7, and the drilling water jet channel inside the coal breaking drill bit 1-8 is connected to the water passage of the baffle seat 1-7-3 of the high-low pressure conversion device 1-7. The slag discharge port of the double-channel water tail 1-2 is connected to the slag discharge pipe 4 used for conveying and discharging crushed coal particles. The pressure water input port of the double-channel water tail 1-2 is sealed to the pressure water output end of the high-pressure water pump 1-3 through a pipeline. The drilling rig 1-1 is connected to the double-wall drill rod 1-4 through a transmission.

[0036] The pump suction and slag backflow unit 2 includes an orifice sealing device 2-1 and a axial jet pump 2-3. The orifice sealing device 2-1 includes a sealed box-type hollow cavity 2-1-1, a front sealing sleeve 2-1-2 communicating with the front of the hollow cavity 2-1-1, a rear sealing sleeve 2-1-3 communicating with the rear of the hollow cavity 2-1-1, an upper gas outlet 2-1-4 communicating with the upper part of the hollow cavity 2-1-1, and a lower coal-water mixture outlet 2-1-5 communicating with the lower part of the hollow cavity 2-1-1. The front sealing sleeve 2-1-2 and the rear sealing sleeve 2-1-3 are coaxially arranged. The double-walled drill rod 1-4 can... The front sealing sleeve 2-1-2, the hollow cavity 2-1-1, and the rear sealing sleeve 2-1-3 pass through the front sealing sleeve 2-1-2, the hollow cavity 2-1-1, and the rear sealing sleeve 2-1-3 along the front and rear axial directions of the orifice sealing device 2-1. The annular space between the outer surface of the double-wall drill rod 1-4 and the inner surface of the front sealing sleeve 2-1-2 serves as a drilling backfill channel. The rear sealing sleeve 2-1-3 is equipped with a sealing ring that matches the outer diameter of the double-wall drill rod 1-4. A stop valve is installed on the lower coal-water mixture discharge port 2-1-5, and the lower coal-water mixture discharge port 2-1-5 is connected to the slag discharge pipe 4 through a pipeline. During drilling operations, the stop valve is opened, and the coal particles generated during drilling can pass through the lower coal-water mixture discharge port 2-1-5. 5. During hydraulic cavity creation, the shut-off valve closes to create a closed back pressure state. Coal particles generated by hydraulic cavity creation can be discharged through the particle conveying channel of the inner tube of the double-walled drill pipe 1-4 via the double-channel tail 1-2. The upper gas outlet 2-1-4 is connected to the gas extraction pipe 3 via a pipeline. The axial jet pump 2-3 is coaxially fixed between the jet device 1-5 and the high-low pressure conversion device 1-7. The axial jet pump 2-3 includes a double-pipe base II, which is a double-pipe structure that is adapted to be connected to the jet device 1-5, including a water conveying channel and an inner pipe. The inner cavity of the inner pipe includes a throat section and a diffuser section from front to back. The front end of the device is connected to the rear end of the piston cylinder structure of the high and low pressure conversion device 1-7. The throat section is also equipped with a coal suction pipe 2-2 that is connected to it. The coal suction pipe 2-2 is inclined forward and passes through the water conveying channel and is connected to the outside. The rear end of the diffuser section is connected to the particle conveying channel of the inner pipe 1-6 of the jet device. When high-pressure water is introduced into the water conveying channel, the high-pressure water is pressurized and jetted when it passes through the throat section of the double pipe base II of the axial jet pump 2-3, so that a negative pressure is formed in the coal suction pipe 2-2, which provides power for sucking coal particles in the borehole. The axial jet pump 2-3 is existing technology and will not be described in detail here.

[0037] To further reduce the deposition of coal particles in the borehole, a spiral drill rod 5 can be coaxially installed between the high-low pressure conversion device 1-7 and the coal breaking drill bit 1-8. The spiral drill rod 5 has a water passage inside that connects to the high-low pressure conversion device 1-7 and the coal breaking drill bit 1-8. During the rotation of the spiral drill rod 5, it can disturb and lift the crushed coal particles that have settled near the bottom of the hole and transport them to the vicinity of the coal suction pipe 2-2.

[0038] Taking the hydraulic cavity creation of a downhole in a coal mine working face as an example, the specific steps for hydraulic cavity creation of a downhole using the integrated system of non-submerged hydraulic cavity creation and slag removal are as follows:

[0039] a. Drilling Operation: Drilling rig 1-1 is arranged at the working face. From front to back, the following components are sequentially and tightly connected: Φ153 coal breaking drill bit 1-8, high / low pressure conversion device 1-7, axial jet pump 2-3, jet device 1-5, double-wall drill rod 1-4, and double-channel water tail 1-2. The water inlet of the double-channel water tail 1-2 is connected to high-pressure water pump 1-3 through a sealed pipeline, and the slag discharge port is connected to slag discharge pipe 4. The double-wall drill rod 1-4 is connected to the driving transmission of drilling rig 1-1. Drilling rig 1-1 drives the coal breaking drill bit 1-8 to open a hole in the coal wall. After drilling 5m, drilling is stopped, and the double-wall drill rod 1-4 and Φ153 coal breaking drill bit are withdrawn. Head 1-8; Lower the front sealing sleeve 2-1-2 into the borehole, and grout the annular gap between the borehole and the front sealing sleeve 2-1-2 to fix the front sealing sleeve 2-1-2. After the grouting section at the borehole opening solidifies, coaxially and tightly install the hollow cavity 2-1-1 and the rear sealing sleeve 2-1-3 on the front sealing sleeve 2-1-2. Seal and connect the lower coal-water mixture outlet 2-1-5 to the slag discharge pipe 4, and seal and connect the upper gas outlet 2-1-4 to the gas extraction pipe 3. Replace the Φ153 coal breaking drill bit 1-8 with the Φ133 coal breaking drill bit 1-8, and install the Φ133... The coal breaking drill bit 1-8, high-low pressure conversion device 1-7, axial jet pump 2-3, jet device 1-5, and double-wall drill rod 1-4 pass through the rear sealing sleeve 2-1-3, hollow cavity 2-1-1, and front sealing sleeve 2-1-2. The drilling rig 1-1 drives the coal breaking drill bit 1-8 downwards to the first coal breaking and cavity-creating section. During drilling, the high-pressure water pump 1-3 supplies low-pressure water. When the low-pressure water enters the high-low pressure conversion device 1-7 through the water delivery channel, the piston 1-7-1 of the high-low pressure conversion device 1-7 is positioned at the piston cylinder joint under the elastic force of the return spring 1-7-2. At the rear end of the stroke of the structure, in the state of blocking the front end of the throat section of the axial jet pump 2-3, the low-pressure water can only enter the drilling water jet channel in the coal breaking drill bit 1-8 through the water inlet hole of piston 1-7-1 and the water passage hole of baffle seat 1-7-3, and carry the slag back to the hollow cavity 2-1-1 of the hole sealing device 2-1 from the annular gap between the double wall drill rod 1-4 and the borehole wall and the drilling back slag channel. The coal particles carried out can be discharged through the coal-water mixture discharge outlet 2-1-5 (the shut-off valve is in the open state). The first hydraulic cavity-making section is drilled to a distance of 18m from the hole opening and then the drilling stops.

[0040] b. Hydraulic cavity creation: Close the shut-off valve at the outlet 2-1-5 of the coal-water mixture, and increase the pressure of the high-pressure water pump 1-3 to 5MPa. The high-pressure water enters the water conveying channel of the double-wall drill rod 1-4 through the inlet of the double-channel tail 1-2. The high-pressure water is first pumped to the jet device 1-5. At this time, part of the high-pressure water is sprayed out through the jet nozzle to form a high-pressure water jet for hydraulic cavity creation, and the other part of the high-pressure water continues to be conveyed forward to the high-low pressure conversion device 1-7. After the high-pressure water reaches the high-low pressure conversion device 1-7, it can force the piston 1-7-1 to move forward, so that the water inlet of the piston 1-7-1 is blocked and the high-low pressure conversion device 1-7 is converted to a high-pressure state. As the piston 1-7-1 moves forward, the front end of the throat section of the axial jet pump 2-3 is connected to the water conveying channel. Due to the piston 1 -7-1 The water inlet is blocked, so high-pressure water can only enter the throat section of the axial jet pump 2-3. The high-pressure water is pressurized and jetted through the throat section of the axial jet pump 2-3 and enters the particle conveying channel of the double-wall drill rod 1-4 through the diffuser section. At the same time, a negative pressure is formed in the coal suction pipe 2-2. The coal particles in the borehole can enter the particle conveying channel of the double-wall drill rod 1-4 through the coal suction pipe 2-2 and finally be discharged from the slag discharge port of the double-channel tail 1-2. During the hydraulic cavity creation, the gas in the cavity can be discharged into the gas extraction pipe 3 through the upper gas discharge port 2-1-4. Continue to increase the pump pressure of the high-pressure water pump 1-3 to 15~20MPa. The high-pressure water jet begins to impact the coal body from top to bottom. Control the drilling rig 1-1 to drive the double-wall drill rod 1-4 to rotate and reciprocate within a range of 1.2m.

[0041] The hydraulic cavity-creating operation of a single hydraulic cavity-creating section can be divided into the following five stages:

[0042] ① During the 0-400mm reciprocating cavity-making stage, the jet device reciprocates within the 0-400mm range. At this time, the coal suction pipe 2-2 is always located in the borehole at the front end of the cavity. The coal suction pipe 2-2 can suck up the smaller coal particles that fall into the borehole.

[0043] ②The 400-600mm reciprocating hole-making stage, such as Figure 2 As shown, the jet nozzle reciprocates within the range of 0-600mm. The coal suction pipe 2-2 can enter the cavity during the reciprocating motion of the drill rod 1-4, and can suck up the coal particles accumulated at the bottom of the cavity. When the slag backflow at the tail discharge port of the dual-channel water tail 1-2 approaches the clear water, the drill is retracted by 400mm, keeping the coal suction pipe 2-2 in the punching cavity, and the coal particles in the punching cavity are sucked up. When the slag backflow at the tail discharge port of the dual-channel water tail 1-2 approaches the clear water again, the drill rod is sent to the 0-600mm layer to continue the hydraulic cavity making operation. If any coal particles are lifted, the above cavity making steps are repeated. If no particles are lifted, the next cavity making stage is entered.

[0044] ③ During the 600-1000mm reciprocating hole-making stage, such as Figure 3As shown, the jet nozzle reciprocates within the range of 600-1000mm, and the punching process is consistent with the 0-400mm reciprocating cavity-making stage.

[0045] ④ During the 1000-1200mm reciprocating hole-making stage, such as Figure 4 As shown, the jet nozzle reciprocates within the range of 1000-1200mm, and the cavity-creating process is consistent with the 400-600mm reciprocating cavity-creating stage.

[0046] ⑤ Hole washing stage: After completing a single cycle of hole creation, keep the drill rod rotating and convey the drill rod downwards. After sending the jet device 1-5 to the bottom of the hole, keep the drill rod without reciprocating (with the upper boundary of the hole as a reference, the jet device 1-5 is at a layer of about 1200mm). Only keep the double-wall drill rod 1-4 rotating slowly. Use the conveying action of the spiral drill rod 5 to draw as much coal particles remaining at the bottom of the borehole as possible to the particle conveying channel of the double-wall drill rod 1-4.

[0047] After the hydraulic cavity creation operation for a single cavity is completed, the pressure of the high-pressure water pump 1-3 is reduced to 0~5MPa. The high-low pressure conversion device 1-7 is reset and converted to a low-pressure state under the elastic force of the return spring 1-7-2. The throat section of the axial jet pump 2-3 is blocked, and low-pressure water enters the drilling water jet channel in the coal breaking drill bit 1-8. The drilling rig 1-1 drives the coal breaking drill bit 1-8 to continue drilling downward to the second hydraulic cavity creation section, and the above hydraulic cavity creation operation is repeated. The length of a single hydraulic cavity creation operation is 1.2m, the distance between adjacent cavities is 10m, and the cumulative cavity creation length of a single borehole is 6m.

[0048] After several cycles of cavity-making are completed in a single borehole, the pressure water inlet of the dual-channel tail 1-2 can be switched to connect with the pressure gas pipeline. By injecting pressure gas into the cavity, the coal-water mixture remaining in the borehole can be forced out through the particulate matter conveying channel.

[0049] During hydraulic cavity creation operations, in order to maintain a certain gas pressure inside the cavity and thus keep the jet nozzle of the jet device 1-5 in a non-submerged, high-efficiency spraying state, a back pressure valve with a set opening and closing pressure can be installed on the upper gas outlet 2-1-4. When the pressure of the gas inside the cavity is greater than the set opening and closing pressure, the back pressure valve will automatically open to release the gas inside the cavity.

[0050] To further improve the suction efficiency of the coal suction pipe 2-2, an additional turbulence nozzle connected to the water conveying channel can be installed between the jet device 1-5 and the coal suction pipe 2-2 to agitate the coal-water mixture near the coal suction pipe 2-2, slow down the settling process of the crushed coal particles, and improve the suction efficiency of the crushed coal particles.

[0051] In the process of hydraulic cavity creation, to ensure that the high-pressure water jet is always in a non-submerged state during the hydraulic cavity creation operation, thereby improving the efficiency of hydraulic cavity creation, as a further improvement of the present invention, the hydraulic cavity creation unit 1 also includes an air injection device located near the jet device 1-5. The air injection device includes a double-tube base III, an air injection pipe, and an air injection nozzle. The double-tube base III is a double-tube structure that is adapted to be connected to the double-wall drill rod 1-4 and includes a water conveying channel and a particulate matter conveying and discharging channel. The air injection pipe can be located in the water conveying channel or the particulate matter conveying and discharging channel. The top end of the air injection pipe extends upward to the double-channel tail 1-2 and is connected to the air pump. The bottom end of the air injection pipe is connected to the air injection nozzle, with the same structure as the jet nozzle. The air injection nozzle located on the double-tube base III penetrates the double-tube base III, and the input end of the air injection nozzle is connected to the air injection pipe. During the hydraulic cavity creation operation, the liquid level can be adjusted by injecting air into the cavity through the air injection nozzle, so that the high-pressure water jet is always in a non-submerged state during the hydraulic cavity creation operation, thereby improving the efficiency of hydraulic cavity creation.

[0052] When using an air injection device, in order to ensure the stable operation of the axial jet pump 2-3 and maintain a non-submerged jet environment for the jet nozzle, the diameter of the jet nozzle of the jet device 1-5 needs to be adjusted. and the injection pressure of the injection device To conduct precise regulation:

[0053] Given the nozzle diameter of the 2-3 throat section of the axial jet pump Under these conditions, the operating flow rate of axial jet pump 2-3 It can be expressed by the following formula (1):

[0054]

[0055] In the formula: The high-pressure water flow velocity is in m / s; The nozzle diameter of the throat section 2-3 of the axial jet pump is in meters.

[0056] Because the jet nozzles in jet device 1-5 and the nozzles of axial jet pump 2-3 share the same high-pressure water supply during the hydraulic cavity-building process, the flow rate of the jet nozzles in jet device 1-5 is... It can be expressed by the following formula (2):

[0057]

[0058] In the formula: The diameter of the jet nozzle of jet devices 1-5 is in meters (m).

[0059] To ensure the stable operation of the axial jet pump 2-3, it is necessary to maintain a stable liquid level in the borehole annulus. Therefore, it is necessary to ensure the flow rate of the jet nozzles in the jet device 1-5. The suction flow rate of the axial jet pump 2-3 They are the same in numerical value, that is ,in The flow ratio of the axial jet pump 2-3 is defined as the ratio of the suction flow rate to the working flow rate of the axial jet pump 2-3.

[0060] Will Substituting into formula (2), the diameter of the jet nozzle of jet device 1-5 is... It can be expressed by the following formula (3):

[0061]

[0062] Substituting formula (1) into formula (3) yields the following formula (4):

[0063]

[0064] Define the pressure ratio of axial jet pump 2-3 The pressure obtained by the suction fluid in the axial jet pump 2-3 Working pressure of axial jet pump 2-3 The ratio is expressed by the following formula (5):

[0065]

[0066] In the formula: The static pressure at the diffuser outlet of the axial jet pump 2-3 is Pa; Fluid density, kg / m³ 3 ; The fluid velocity at the diffuser outlet of the axial jet pump 2-3 is m / s; The height of the diffuser tube for axial jet pump 2-3 is in meters (m). The static pressure at the coal suction port of coal suction pipe 2-2 is given in Pa. The fluid velocity at the suction port of the coal suction pipe 2-2 is m / s; The height of the coal suction port of coal suction pipe 2-2 is in meters (m). The inlet static pressure of the throat section 2-3 of the axial jet pump is in Pa; The inlet fluid velocity (m / s) is the velocity of the fluid in the throat section 2-3 of the axial jet pump. The inlet height of the throat section 2-3 of the axial jet pump is in meters (m).

[0067] In the downward drilling hydraulic cavity-making process, the lifting height of crushed coal particles can reach hundreds of meters, while the total length of the axial jet pump 2-3 is only 1-2 meters. Therefore, the height of each plane in formula (5) can be regarded as Furthermore, the fluid dynamic pressure at each component of the axial jet pump 2-3 accounts for only a small portion of the total pressure. Therefore, in the context of down-drilling hydraulic cavity creation practice, formula (5) can be simplified to the following formula (6):

[0068]

[0069] in It can be expressed as the following formula (7):

[0070]

[0071] In the formula: The height difference, in meters, is the difference between the liquid level in the borehole annulus and the coal suction port.

[0072] In engineering practice, to create a non-submerged jet coal breaking environment within the borehole annulus, it is necessary to inject pressure of [pressure value missing] into the borehole annulus. High-pressure gas is used to control the liquid level in the borehole annulus between the jet nozzle of jet device 1-5 and the coal suction port of axial jet pump 2-3. At this time, the height difference between the liquid level in the borehole annulus and the coal suction port is... Typically about 1m, the hydrostatic pressure it generates is similar to The static pressure at the coal suction port of coal suction pipe 2-2 is negligible. This can be simplified to the injection pressure of the injection device. ,Right now Then formula (6) can be simplified to the following formula (8):

[0073]

[0074] In formula (8), the static pressure at the diffuser outlet of the axial jet pump 2-3 The inlet static pressure of the axial jet pump 2-3 throat section The relationship can be obtained through Bernoulli's equation. Bernoulli's equation is derived from the diffuser outlet of the axial jet pump 2-3 and the inner tube outlet of the double-walled drill pipe 1-4, as shown in formula (9):

[0075]

[0076] In the formula: Atmospheric pressure, Pa; The height of the inner tube outlet of the double-walled drill pipe 1-4 is in meters. The fluid velocity at the outlet of the inner tube of the double-walled drill pipe 1-4 is in m / s; The friction resistance, in Pa, is the frictional resistance from the outlet of the diffuser tube of the axial jet pump 2-3 to the outlet of the inner tube of the double-walled drill pipe 1-4.

[0077] Since the outlet of the inner tube of the double-walled drill pipe 1-4 is a free interface, formula (9) can be simplified to the following formula (10):

[0078]

[0079] Bernoulli's equation is applied to the inlet plane of the throat section 2-3 of the axial jet pump and the outlet plane of the high-pressure water pump 1-3, as shown in the following formula (11):

[0080]

[0081] In the formula: The friction resistance, in Pa, is the resistance along the path of high-pressure water delivery to the inlet of the throat section 2-3 of the axial jet pump. The pressure of the high-pressure water pump is 1-3, Pa; The velocity of the fluid at the outlet of high-pressure water pumps 1-3 is in m / s.

[0082] Ignoring the dynamic pressure difference between the outlet of high-pressure water pump 1-3 and the inlet of the throat section of axial jet pump 2-3, formula (11) can be simplified to the following formula (12):

[0083]

[0084] Due to the aforementioned Then, formulas (10) and (12) can be further simplified to the following formula (13):

[0085]

[0086] In the formula: To increase the height, m, ,in The total length of the double-walled drill pipe 1-4 is in meters. The borehole inclination angle is expressed in degrees.

[0087] Friction resistance along the path from the outlet of the diffuser tube of the axial jet pump 2-3 to the outlet of the inner tube of the double-wall drill pipe 1-4 Friction resistance along the process of high-pressure water being delivered to the inlet of the throat section 2-3 of the axial jet pump. It can be calculated by the Darcy-Weisbach equation, as shown in the following formula (14):

[0088]

[0089] In the formula: The friction coefficient of the inner tube of the double-walled drill pipe 1-4; The friction coefficient of the outer annulus clearance of the double-walled drill pipe 1-4; The hydraulic diameter of the inner tube of the double-walled drill pipe 1-4 is in meters. The hydraulic diameter of the outer annulus of the double-walled drill pipe 1-4 is in meters. The fluid velocity in the inner tubes of the double-walled drill pipe 1-4 is m / s; The fluid velocity in the outer annulus of the double-walled drill pipe 1-4 is m / s.

[0090] and It can be calculated using the following formula (15):

[0091]

[0092] In the formula: The area of ​​the outer annulus of the double-walled drill pipe 1-4 is in meters. 2 ; For double-walled drill pipes, the outer annular wetted circumference is 1-4, m; The inner diameter of the double-walled drill pipe 1-4 is in meters. The outer pipe diameter of double-walled drill pipes 1-4 is in meters.

[0093] and It can be calculated using the following formula (16):

[0094]

[0095] Combining formulas (8) and (13) to (16), we can obtain the following formula (17):

[0096]

[0097] As can be seen from the above formula, in order to ensure the stable operation of the axial jet pump 2-3 and maintain the non-submerged jet environment of the jet nozzle, the diameter of the jet nozzle of the jet device 1-5 is... and the injection pressure of the injection device Precise control can be achieved through formulas (4) and (17) respectively.

[0098] To achieve water recycling, the slag discharge pipe 4 can be connected to a coal-water separation device, and the separated water can be used to supply high-pressure water pumps 1-3.

[0099] This integrated system for non-submerged hydraulic cavity creation and slag removal in downhole drilling can fully utilize the shear disturbance generated by the rotation of the drill rod and the pulsating flow field formed by the high-pressure water jet during the cavity creation stage to continuously break, suspend, and discharge coal particles in the borehole. It achieves simultaneous hydraulic cavity creation and coordinated coal particle conveying and discharge, which can fundamentally eliminate particle deposition and consolidation problems, improve the stability and pressure relief and permeability enhancement effect of downhole cavity creation, and realize the gas-enhanced extraction process integrating cavity creation and conveying and discharge. It is particularly suitable for downhole hydraulic cavity creation, pressure relief and permeability enhancement in inclined coal seams.

Claims

1. An integrated system for non-submerged hydraulic cavity creation and slag removal in downward drilling, comprising a hydraulic cavity creation unit (1), the hydraulic cavity creation unit (1) comprising a coal-breaking drill bit (1-8), a high-low pressure conversion device (1-7), a jet device (1-5), a double-wall drill rod (1-4), a dual-channel tailpipe (1-2), a drilling rig (1-1), and a high-pressure water pump (1-3); the double-wall drill rod (1-4) comprises an inner tube and an outer tube arranged coaxially, the annulus between the inner tube and the outer tube is a water conveying channel, the hollow inner cavity of the inner tube is a particle conveying and discharging channel, multiple double-wall drill rods (1-4) are sequentially connected and coaxially installed, the front end of the foremost double-wall drill rod (1-4) is coaxially connected to the jet device (1-5), and the rear end of the last double-wall drill rod (1-4) is connected to the dual-channel tailpipe (1-2); the jet device The device (1-5) includes a double-tube base I and a jet nozzle. The double-tube base I is a double-tube structure that is adapted to be connected to the double-wall drill rod (1-4) and includes a water conveying channel and a particulate matter conveying channel. The double-tube base I includes an inner tube (1-6) of the jet device. The jet nozzle is set in the radial direction along the double-tube base I and the input end of the jet nozzle is connected to the water conveying channel. The high-low pressure conversion device (1-7) is coaxially installed in front of the jet device (1-5). The coal breaking drill bit (1-8) is coaxially installed in front of the high-low pressure conversion device (1-7). The slag discharge port of the double-channel water tail (1-2) is connected to the slag discharge pipe (4). The pressure water input port of the double-channel water tail (1-2) is sealed to the pressure water output port of the high-pressure water pump (1-3). The drilling rig (1-1) is connected to the double-wall drill rod (1-4) in a transmission connection. Its features are, It also includes a pump suction and slag backing unit (2), which includes an orifice sealing device (2-1) and a axial jet pump (2-3); the orifice sealing device (2-1) includes a closed box-type hollow cavity (2-1-1) and a front sealing sleeve (2-1-2) that communicates with the front of the hollow cavity (2-1-1), a rear sealing sleeve (2-1-3) that communicates with the rear of the hollow cavity (2-1-1), and a rear sealing sleeve (2-1-3) that communicates with the upper part of the hollow cavity (2-1-1). The upper gas outlet (2-1-4) and the lower coal-water mixture outlet (2-1-5) are connected to the lower part of the hollow cavity (2-1-1). The front sealing sleeve (2-1-2) and the rear sealing sleeve (2-1-3) are coaxially arranged. The annulus between the outer surface of the double-wall drill rod (1-4) and the inner surface of the front sealing sleeve (2-1-2) serves as a drilling backfill channel. The rear sealing sleeve (2-1-3) is equipped with a seal that matches the outer diameter of the double-wall drill rod (1-4). The ring has a stop valve on the lower coal-water mixture outlet (2-1-5) and is connected to the slag discharge pipe (4). The upper gas outlet (2-1-4) is connected to the gas extraction pipe (3). The axial jet pump (2-3) is coaxially fixed between the jet device (1-5) and the high-low pressure conversion device (1-7). The axial jet pump (2-3) includes a double-pipe base II, which is adapted to the jet device (1-5). The connection includes a double-pipe structure consisting of a water conveying channel and an inner pipe. The inner cavity of the inner pipe consists of a throat section and a diffuser section from front to back. The front end of the throat section is connected to the rear end of the high-low pressure conversion device (1-7). The throat section is also equipped with a coal suction pipe (2-2) that is connected to it. The coal suction pipe (2-2) is inclined forward and passes through the water conveying channel and is connected to the outside. The rear end of the diffuser section is connected to the particulate matter conveying channel of the inner pipe (1-6) of the jet device.

2. The integrated system for non-submerged hydraulic cavity creation and slag removal in downward drilling according to claim 1, characterized in that, The hydraulic cavity-making unit (1) also includes an air injection device located near the jet device (1-5). The air injection device includes a double-tube base III, an air injection pipe, and an air injection nozzle. The double-tube base III is a double-tube structure that is adapted to be connected to the double-wall drill rod (1-4) and includes a water conveying channel and a particle conveying and discharging channel. The air injection pipe can be located in the water conveying channel or the particle conveying and discharging channel. The top end of the air injection pipe extends upward to the double-channel water tail (1-2) and is connected to the air pump. The bottom end of the air injection pipe is connected to the air injection nozzle. The structure is the same as that of the jet nozzle. The air injection nozzle located on the double-tube base III penetrates the double-tube base III and the input end of the air injection nozzle is connected to the air injection pipe.

3. The integrated system for non-submerged hydraulic cavity creation and slag removal in downward drilling according to claim 2, characterized in that, The diameter of the jet nozzle of the jet device (1-5) and the injection pressure of the injection device Precise control can be achieved through the following formula: In the formula: The nozzle diameter of the throat section of the axial jet pump (2-3); The flow ratio of the axial jet pump (2-3) is the ratio of the suction flow rate to the working flow rate of the axial jet pump (2-3); For fluid density; This is the total length of the double-walled drill pipe (1-4); The drilling angle; The pressure ratio of the axial jet pump (2-3) is the pressure obtained by the suction fluid in the axial jet pump (2-3). Working pressure of the axial jet pump (2-3) The ratio; Atmospheric pressure; The friction coefficient of the inner tube of the double-walled drill pipe (1-4); The inner diameter of the double-walled drill pipe (1-4); The working flow rate of the axial jet pump (2-3); The suction flow rate of the axial jet pump (2-3); The friction coefficient of the outer annulus of the double-walled drill pipe (1-4); The outer diameter of the double-walled drill pipe (1-4) is shown.

4. The integrated system for non-submerged hydraulic cavity creation and slag removal in downward drilling according to claim 1, characterized in that, The jet nozzle of the jet device (1-5) is located inside the double tube base I. The body of the jet nozzle passes through the inner tube (1-6) of the jet device along the radial direction of the double tube base I, and the body of the jet nozzle is sealed to the inner tube (1-6) of the jet device.

5. The integrated system for non-submerged hydraulic cavity creation and slag removal in downward drilling according to claim 1, characterized in that, The high-low pressure conversion device (1-7) is a piston cylinder structure including a piston (1-7-1), a baffle seat (1-7-3), and a return spring (1-7-2). The rear end of the piston cylinder structure is connected to the water supply channel. The piston is slidably installed at the inner rear end of the piston cylinder structure, and the piston (1-7-1) has a water inlet channel inside. Its water inlet hole is located on the side of the rear end of the piston (1-7-1), and its water outlet is located on the front end face of the piston (1-7-1). The baffle seat (1-7-3) is positioned at the inner front end of the piston cylinder structure. Furthermore, the baffle seat (1-7-3) is provided with a water passage hole that passes through the baffle seat (1-7-3) in the axial direction. The baffle seat (1-7-3) is also provided with a plug structure that extends backward at the position corresponding to the piston water outlet hole. The front and rear ends of the return spring (1-7-2) are respectively abutted against the rear end of the baffle seat (1-7-3) and the front end of the piston (1-7-1). The drilling water jet channel in the coal breaking drill bit (1-8) is connected to the water passage hole of the baffle seat (1-7-3) of the high and low pressure conversion device (1-7).

6. The integrated system for non-submerged hydraulic cavity creation and slag removal in downward drilling according to claim 1, characterized in that, A spiral drill rod (5) is coaxially installed between the high-low pressure conversion device (1-7) and the coal breaking drill bit (1-8), and the spiral drill rod (5) has a water passage inside that connects to the high-low pressure conversion device (1-7) and the coal breaking drill bit (1-8).

7. The integrated system for non-submerged hydraulic cavity creation and slag removal in downward drilling according to claim 1, characterized in that, A back pressure valve with adjustable opening and closing pressure is installed on the upper gas outlet (2-1-4).

8. The integrated system for non-submerged hydraulic cavity creation and slag removal in downward drilling according to claim 1, characterized in that, A turbulence nozzle connected to the water conveying channel is also provided between the jet device (1-5) and the coal suction pipe (2-2).

9. An integrated method for non-submerged hydraulic cavity creation and slag removal in downhole drilling based on the integrated system for downhole non-submerged hydraulic cavity creation and slag removal as described in claim 1, characterized in that, Specifically, the following steps are included: a. Drilling operation: Using the drilling rig (1-1) to drive the large-diameter coal-breaking drill bit (1-8) to drill a hole in the coal wall to the set depth, then retract the drill bit. Insert the front sealing sleeve (2-1-2) into the borehole and fix it. Install the hollow cavity (2-1-1) and the rear sealing sleeve (2-1-3) coaxially and sealed on the front sealing sleeve (2-1-2). Seal the lower coal-water mixture outlet (2-1-5) with the slag discharge pipe (4) and the upper gas outlet (2-1-4) with the gas extraction pipe (3). Then replace the small-diameter coal-breaking drill bit (1-8) and install the high-low pressure conversion device (1-7), the axial jet pump (2-3), and the jet pump in sequence. The flow device (1-5) and double-walled drill rod (1-4) are inserted into the rear sealing sleeve (2-1-3), hollow cavity (2-1-1) and front sealing sleeve (2-1-2). The drilling rig (1-1) drives the coal breaking drill bit (1-8) to continue drilling downward to the first coal breaking and cavity-making section. During the drilling process, the high-pressure water pump (1-3) supplies low-pressure water. The shut-off valve on the lower coal-water mixture discharge port (2-1-5) is in the open state. The slag returns to the hollow cavity (2-1-1) through the annular gap between the double-walled drill rod (1-4) and the borehole wall and the drilling slag return channel, and is discharged into the slag discharge pipe (4) through the lower coal-water mixture discharge port (2-1-5). b. Hydraulic Cavity Formation: Close the shut-off valve at the outlet (2-1-5) of the coal-water mixture, increase the pump pressure of the high-pressure water pump (1-3), and a portion of the high-pressure water is ejected through the jet nozzle of the jet device (1-5) to form a high-pressure water jet for hydraulic cavity formation. The other portion of the high-pressure water continues to be transported forward to the high-low pressure conversion device (1-7), causing the high-low pressure conversion device (1-7) to switch to a high-pressure state. The front end of the throat section of the axial jet pump (2-3) is connected to the water delivery channel, and the high-pressure water enters the axial jet pump (2-3). The jet is pressurized in the throat section and enters the particulate conveying channel of the double-wall drill rod (1-4) through the diffuser section. At the same time, a negative pressure is formed in the coal suction pipe (2-2). The coal particles enter the particulate conveying channel of the double-wall drill rod (1-4) through the coal suction pipe (2-2) and are finally discharged from the slag discharge port of the double-channel tail (1-2). The gas in the cavity is discharged into the gas extraction pipe (3) through the upper gas discharge port (2-1-4). The drilling rig (1-1) is controlled to drive the double-wall drill rod (1-4) to rotate and reciprocate within a set range. After the hydraulic cavity-making operation of the first coal-breaking cavity-making section is completed, the pump pressure of the high-pressure water pump (1-3) is reduced, the high-low pressure conversion device (1-7) is reset and converted to the low pressure state, and the drilling rig (1-1) drives the coal-breaking drill bit (1-8) to continue drilling downward to the second hydraulic cavity-making section, and the above hydraulic cavity-making operation is repeated. This process is repeated to complete the hydraulic cavity-making operation for all coal-breaking and cavity-making sections.

10. The integrated method for non-submerged hydraulic cavity creation and slag removal in downward drilling according to claim 9, characterized in that, After several cycles of cavity-making are completed in a single borehole, the pressure water inlet of the dual-channel water tail (1-2) can be switched to connect with the pressure gas pipeline. By injecting pressure gas into the cavity, the coal-water mixture remaining in the borehole can be forced out through the particulate matter conveying channel.

Images