An experimental device and method for simulating liquid and residue carrying in gas drilling in a coal mine underground

Abstract

This invention discloses an experimental device and method for simulating gas drilling with fluid and slag carrying in coal mines. The device includes a drilling simulation system, a gas injection system, a liquid injection system, a solid phase supply system, a data acquisition and monitoring system, a separation and recovery system, and a centralized control system. This invention, through an adjustable-angle simulated borehole, a rotatable drill rod, and multi-point injectable liquid, can highly replicate the complex drilling conditions in coal mines. Key parameters such as gas flow rate, liquid flow rate, slag supply rate, and drill rod rotation speed can be independently and precisely controlled, facilitating single-factor influence analysis. The transparent simulated borehole design, combined with high-speed imaging, allows for direct observation of the multiphase flow mechanism. Through system experiments, key process parameters such as the minimum slag-carrying gas velocity and optimal gas injection volume under different geological and technological conditions can be determined, providing a scientific basis for optimizing borehole design parameters, drilling process parameters, and preventing accidents, effectively improving drilling efficiency and safety.

Description

Technical Field

[0001] This invention belongs to the field of coal mine gas control, and relates to an experimental simulation device and method for simulating and studying the multiphase flow law of gas, liquid and drill cuttings in the annulus when drilling in coal mines using gas as the circulating medium. Background Technology

[0002] Gas drilling technology is one of the key technologies for gas drainage drilling in soft, fractured coal seams in underground coal mines, significantly improving the drilling depth, efficiency, and gas drainage effect. However, under conditions of formation water inflow, this technology still exhibits significant limitations. This is due to two main reasons: firstly, drill cuttings mix with formation water to form clumps that adhere to the drill pipe and borehole wall, increasing the frictional resistance of the drill string and gradually clogging the annulus; secondly, formation water inflow weakens borehole stability, easily causing overall borehole collapse, leading to borehole accidents such as drill bit burial and stuck drill bits, seriously threatening drilling success rate and operational safety.

[0003] Currently, research on the slag and fluid carrying mechanisms during gas drilling in soft, fractured coal seams mainly relies on two methods: field tests and numerical simulations. While field tests can reflect real-world conditions, they are costly, risky, and time-consuming, and are limited by geological conditions, making it difficult to systematically analyze the influence mechanisms of various parameters. Numerical simulations, while facilitating parameter control, are limited in accuracy by the constitutive model and boundary conditions, still requiring experimental data verification, thus lacking reliability. Furthermore, existing laboratory simulation devices have relatively limited functionality, making it difficult to reproduce the complex geological and working conditions underground, especially in simulating the coupling effects of multiple factors, leading to significant deviations between experimental results and actual drilling processes. Therefore, to deeply reveal the annular multiphase flow mechanism during underground gas drilling in coal mines, there is an urgent need to develop experimental devices and methods that can highly simulate real-world conditions and possess independent control and visualization capabilities for multiple parameters. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an experimental device and method for simulating gas drilling with fluid and slag carrying in underground coal mines. This invention solves the problem that existing methods for studying the multiphase flow law in underground coal mine gas drilling are unable to realistically simulate complex geological and working conditions. By accurately reproducing the real gas drilling environment in underground coal mines, the invention enables a systematic study of the flow law of gas, liquid, and solid multiphase media within the borehole, providing reliable theoretical support for optimizing gas drilling technology and safety control strategies in soft coal seams.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] An experimental device for simulating underground gas drilling with liquid and slag carrying in coal mines includes a drilling simulation system, a gas injection system, a liquid injection system, a solid phase supply system, a data acquisition and monitoring system, a separation and recovery system, and a centralized control system. The drilling simulation system includes a simulated borehole, a simulated drill rod extending into the simulated borehole, a simulated drill bit connected to the front end of the simulated drill rod, a motor connected to the rear end of the simulated drill rod, and a simulated angle adjustment mechanism that can support and adjust the angle of the simulated borehole. The gas injection system includes an air compressor, a gas storage tank, a pressure regulating valve, and a gas flow meter connected in sequence via a gas supply pipeline and connected to the simulated borehole opening; The liquid injection system includes a liquid storage tank, a liquid pump, a liquid flow meter, and a liquid regulating valve connected in sequence through a liquid supply pipeline and connected to multiple radial liquid injection holes on the simulated borehole sidewall. The solid phase supply system includes a cuttings storage bin and a cuttings feeding device connected to it. The cuttings feeding device is connected to the bottom of the simulated borehole to transport the cuttings. The data acquisition and monitoring system includes a high-speed camera group located outside the simulated borehole, and a pressure sensor and a differential pressure sensor located inside the simulated borehole. The separation and recovery system includes a recovery tank connected to the simulated borehole outlet, a filter screen installed inside the recovery tank, and a conduit installed at the top of the recovery tank. The centralized control system is connected to the gas injection system, liquid injection system, solid phase supply system, data acquisition and monitoring system, and separation and recovery system via data lines. It centrally sets and controls all experimental parameters and receives, processes, displays, and stores monitoring data and video data from each sensor in real time.

[0007] The present invention also includes the following technical features: Specifically, the simulated borehole is made of high-strength transparent plexiglass; the front end of the simulated drill rod is connected to the simulated drill bit via threads, and both the simulated drill rod and the simulated drill bit are built into the simulated borehole; the motor is connected to the rear end of the simulated drill rod via a coupling; the simulated angle adjustment mechanism is located below the entire simulated borehole to support and fix it. The simulated drill pipe is a drill pipe with a replaceable structure, including an external flat drill pipe, a spiral drill pipe, and a triangular spiral drill pipe.

[0008] Specifically, the gas supply pipeline is equipped with a high-frequency pulse generator to generate pulsed airflow with a specific frequency and amplitude, simulating the mechanism by which oscillating shear force destroys borehole sediment and enhances the ability to carry liquid and sediment.

[0009] Specifically, the drill cuttings storage bin includes multiple independent chambers, in which drill cuttings of different particle sizes are pre-loaded. The opening and closing of the independent chambers are controlled by electromagnetic valves, so that the drill cuttings are mixed in a preset ratio or transported to the simulated borehole through a drill cuttings feeding device in a specific time sequence to simulate the heterogeneous drill cuttings generated by complex broken coal seams.

[0010] Specifically, the drill cuttings storage bin includes a coal sample chamber and a gangue chamber; The coal sample chamber is equipped with multiple chambers, each containing coal samples with different strength coefficients; The gangue chamber is filled with coal gangue; Both the coal sample chamber and the gangue chamber are equipped with electromagnetic valves and conveying pipelines at their lower outlets, and are connected to a slag collector via the conveying pipelines; the slag collector is connected to a negative pressure pipeline to provide slag discharge power to the coal sample chamber and the gangue chamber; A stirrer is connected below the slag collector; The bottom of the drill cuttings storage bin has a conical structure; a vibrator is installed on the outer side of the bottom of the conical structure.

[0011] Specifically, the cuttings feeding device includes a screw feeder and a stepper motor, and a vibrator is connected to the screw feeder through a flexible conveying pipe; the outlet of the screw feeder is connected to the injection point at the bottom of the simulated borehole through a flexible conveying pipe.

[0012] Specifically, the high-speed camera group includes multiple high-speed cameras, which are spaced apart on the outside of the transparent simulated borehole; the pressure sensors are spaced apart along the inside of the simulated borehole; the differential pressure sensors are placed in specific sections inside the simulated borehole; and the high-speed cameras are equipped with particle image velocimetry modules.

[0013] Specifically, after the gas-liquid-solid mixture discharged from the simulated borehole enters the recovery tank, the gas is discharged into the atmosphere through a conduit; the liquid and fine particles pass through the filter screen, the drill cuttings particles are intercepted by the filter screen, and the liquid is collected and processed uniformly at the bottom of the recovery tank.

[0014] Specifically, the simulated angle adjustment mechanism includes: a support frame as the basic load-bearing structure of the entire mechanism; a rotary support device fixedly installed on the support frame; a clamping device for directly clamping the simulated borehole and fixedly connected to the rotary support device; a fixing device on the rotary support device to achieve reliable locking of the simulated borehole; and an angle sensor installed on the rotary support device to detect and feedback its rotation angle in real time.

[0015] The experimental simulation method for the simulated coal mine underground gas drilling fluid-carrying and slag-carrying experimental device includes the following steps: Step 1, Experimental preparation: Load the dry simulated drill cuttings with a preset particle size distribution into the solid phase supply system and check the sealing and operating status of each system. Step 2, parameter setting: Set the experimental operating parameters through the centralized control system, including the simulated borehole inclination angle, gas flow rate, liquid injection flow rate, drill cuttings injection rate, and drill rod rotation speed. Step 3, Start the experiment: First, start the gas injection system and introduce gas at a set flow rate into the simulated borehole through the through hole in the simulated drill rod; then, start the rotation of the simulated drill rod; finally, start the liquid phase injection system and the solid phase supply system and inject clean water and drill cuttings into the bottom of the simulated borehole at a set rate. Step 4, Process Monitoring and Data Acquisition: The gas-liquid-solid three-phase flow state in the annulus is recorded in its entirety by a high-speed camera group; the pressure distribution along the annulus and the pressure drop parameters of specific sections are collected in real time by pressure sensors and differential pressure sensors; the torque and speed of the simulated drill pipe are collected in real time by deploying torque sensors and speed sensors; the collected data are transmitted to the centralized control system in real time. Step 5, Result Analysis and Processing: First, stop the injection of drill cuttings, then stop the injection of water, and finally stop the gas injection; perform image analysis based on high-speed camera video to quantify the parameters of drill cuttings transport speed, critical cuttings-carrying gas velocity, and liquid accumulation height; combine pressure and differential pressure data to analyze the friction loss of annular multiphase flow; and analyze the influence of different drilling process parameters on cuttings discharge based on the collected torque and rotational speed data. Step 6: Change one or more operating parameters from Step 2, and repeat Step 3 and Step 4 to conduct comparative experiments and study the influence of each parameter on the liquid and slag carrying efficiency. Step 7: Change the input parameters of the gas-liquid-solid mixture to form sediment at the lower edge of the simulated borehole wall; then inject pulsed airflow of specific frequency and amplitude into the simulated borehole through a high-frequency pulse generator to study the mechanism of oscillating shear force on destroying sediment on the lower side of the borehole wall and enhancing liquid carrying capacity. Step 8: After the experiment is completed, treat the wastewater and drilling slag collected by the separation and recovery system.

[0016] Compared with the prior art, the present invention has the following technical effects: (1) The present invention can highly reproduce the complex drilling conditions in coal mines by means of adjustable tilt angle simulated drilling, rotatable drill rod, and multi-point injectable liquid.

[0017] (2) The key parameters of this invention, such as gas flow rate, liquid flow rate, slag supply rate, and drill rod rotation speed, can be independently and precisely controlled, facilitating single-factor influence analysis; the transparent simulated borehole design, combined with high-speed imaging, allows for intuitive observation of the multiphase flow mechanism. The experimental data are abundant, mutually verified, and highly reliable.

[0018] (3) Through systematic experiments, this invention can determine key process parameters such as minimum slag-carrying gas velocity and optimal gas injection volume under different geological and technological conditions, providing a scientific basis for the optimization of borehole design parameters, drilling process parameters and accident prevention, and effectively improving drilling efficiency and safety. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the experimental apparatus of the present invention.

[0020] Figure 2 This is a schematic diagram of the simulated angle adjustment mechanism of the present invention.

[0021] Figure 3 This is a schematic diagram of the cuttings storage bin structure of the solid phase supply system of the present invention.

[0022] The meanings of the various markings in the diagram are as follows: 1-Simulated drilling, 2-Simulated drill rod, 3-Simulated drill bit, 4-Motor, 5-Simulated angle adjustment mechanism, 6-Coupling, 7-Liquid injection hole, 8-Air compressor, 9-Gas storage tank, 10-Pressure regulating valve, 11-Gas flow meter, 12-Gas supply pipeline, 13-High frequency pulse generator, 14-Liquid storage tank, 15-Liquid pump, 16-Liquid flow meter, 17-Regulating valve, 18-Liquid supply pipeline, 19-Drill cuttings storage bin, 20-Drill cuttings addition device, 21-High-speed camera group, 22-Pressure sensor, 23-Differential pressure sensor, 24-Recovery box Body, 25-Filter screen, 26-Conduit; 27-Centralized control system; 501-Support frame; 502-Rotary support device; 503-Clamping device; 504-Fixing device; 505-Angle sensor, 1901-Coal sample chamber, 1902-Gange chamber, 1903-Solenoid valve, 1904-Conveying pipeline, 1905-Slag collector, 1906-Agitator, 1907-Negative pressure pipeline, 1908-Conical structure, 1909-Vibrator, 19010-Flexible conveying pipeline, 2001-Screw feeder, 2002-Stepper motor. Detailed Implementation

[0023] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0024] Example: This embodiment provides an experimental device for simulating underground gas drilling with fluid and slag carrying in coal mines, such as... Figures 1 to 3 As shown, it includes a drilling simulation system, a gas injection system, a liquid injection system, a solid phase supply system, a data acquisition and monitoring system, a separation and recovery system, and a centralized control system.

[0025] The drilling simulation system includes a simulated borehole 1, a simulated drill rod 2 extending into the simulated borehole 1, a simulated drill bit 3 connected to the front end of the simulated drill rod 2, a motor 4 connected to the rear end of the simulated drill rod 2, and a simulated angle adjustment mechanism 5 that can support and adjust the angle of the simulated borehole 1.

[0026] The gas injection system includes an air compressor 8, a gas storage tank 9, a pressure regulating valve 10, and a gas flow meter 11 connected in sequence through a gas supply pipeline 12 and connected to the opening of the simulated borehole 1, for injecting compressed air with a preset pressure and flow rate into the simulated borehole 1.

[0027] The liquid injection system includes a liquid storage tank 14, a liquid pump 15, a liquid flow meter 16 and a liquid regulating valve 17 connected in sequence through a liquid supply pipeline 18 and connected to multiple radial liquid injection holes 7 on the sidewall of the simulated borehole 1, so as to realize multi-point and multi-time sequence injection of liquid, which is used to simulate annular multiphase flow under complex formation water intrusion environment.

[0028] The solid phase supply system includes a cuttings storage bin 19 and a cuttings feeding device 20 connected thereto. The cuttings feeding device 20 is connected to the bottom of the simulated borehole 1 to transport the cuttings.

[0029] The data acquisition and monitoring system includes a high-speed camera group 21 located outside the simulated borehole 1, a pressure sensor 22 located inside the simulated borehole 1, and a differential pressure sensor 23.

[0030] The separation and recovery system includes a recovery tank 24 connected to the outlet of the simulated borehole 1, a filter screen 25 disposed inside the recovery tank 24, and a conduit 26 disposed at the top of the recovery tank 24.

[0031] The centralized control system is connected to the gas injection system, liquid injection system, solid phase supply system, data acquisition and monitoring system, and separation and recovery system via data cables. It is used to centrally set and control all experimental parameters, and to receive, process, display, and store monitoring data and video data from each sensor in real time.

[0032] Specifically, the simulated borehole 1 is made of high-strength transparent plexiglass and is used to simulate the annular environment of the borehole; the front end of the simulated drill rod 2 is connected to the simulated drill bit 3 by a thread, and both the simulated drill rod 2 and the simulated drill bit 3 are built into the simulated borehole 1; the motor 4 is connected to the rear end of the simulated drill rod 2 through a coupling 6 to drive the simulated drill rod 2 to rotate the simulated drill bit 3, which is used to simulate the actual drilling process; the simulated angle adjustment mechanism 5 is located below the entire simulated borehole 1 to support and fix it. The simulated drill pipe 2 is designed as a drill pipe with a replaceable structure, including external flat drill pipe, spiral drill pipe and triangular spiral drill pipe, etc., to study the influence of different drill pipe structures on slag removal efficiency and multiphase flow field.

[0033] A high-frequency pulse generator 13 is installed on the gas supply pipeline 12 to generate pulsed airflow with a specific frequency and amplitude, which is used to simulate the mechanism by which oscillating shear force destroys borehole sediment and enhances the ability to carry liquid and sediment.

[0034] The cuttings storage chamber 19 includes multiple independent chambers, in which cuttings of different particle sizes are preloaded. The opening and closing of the independent chambers are controlled by solenoid valves, so that the cuttings are mixed in a preset ratio or transported to the simulated borehole 1 through the cuttings feeding device 20 in a specific time sequence, simulating the heterogeneous cuttings generated by complex broken coal seams.

[0035] The drill cuttings storage bin 19 includes a coal sample chamber 1901 and a gangue chamber 1902. Multiple coal sample chambers 1901 are provided, containing coal samples with different strength coefficients to simulate various types of broken coal bodies. The gangue chamber 1902 contains coal gangue to simulate the situation where soft, broken coal bodies contain intercalated gangue. Both the coal sample chamber 1901 and the gangue chamber 1902 are equipped with electromagnetic valves 1903 and conveying pipelines 1904 at their lower outlets, and are connected to a slag collector 1905 via the conveying pipelines 1904. The slag collector 1905 is connected to the negative pressure pipeline 1907 to provide slag discharge power to the coal sample chamber 1901 and the gangue chamber 1902; a stirrer 1906 is connected below the slag collector 1905 to fully stir the coal sample and gangue; the bottom of the slag storage bin 19 has a conical structure 1908, which is conducive to the coal slag gathering towards the outlet under the action of gravity and prevents blockage; a vibrator 1909 is installed on the outside of the bottom of the conical structure 1908 to assist in feeding and ensure the continuity of feeding; The cuttings feeding device includes a screw feeder 2001 and a stepper motor 2002. A vibrator 1909 is connected to the screw feeder 2001 through a flexible conveying pipe 19010 and is driven by the stepper motor 2002 via a belt. The outlet of the screw feeder 2001 is connected to the injection point at the bottom of the simulated borehole 1 through the flexible conveying pipe 19010.

[0036] The high-speed camera group 21 includes multiple high-speed cameras, which are spaced apart on the outside of the transparent simulated borehole 1 to capture the three-phase flow state of gas, liquid and solid in the annulus, the migration trajectory of drill cuttings particles, the distribution of liquid film on the annulus wall, and possible blockage processes throughout the process. Pressure sensors 22 are arranged at intervals along the inside of the simulated borehole 1 to measure the pressure values ​​at different locations in the annulus. Differential pressure sensors 23 are arranged in specific sections inside the simulated borehole 1 to monitor the real-time pressure drop in that section. The high-speed cameras are equipped with a particle image velocimetry module for non-contact and accurate measurement of the local velocity vector of the annulus flow field, the thickness of the liquid film, and the thickness of the drill cuttings accumulation.

[0037] After the gas-liquid-solid mixture discharged from the simulated borehole 1 enters the recovery tank 24, the gas is discharged into the atmosphere through the conduit 26; the liquid and fine particles pass through the filter screen 25, the drill cuttings particles are intercepted by the filter screen 25, and the liquid is collected and processed uniformly at the bottom of the recovery tank 24.

[0038] The simulated angle adjustment mechanism 5 includes: a support frame 501 as the basic load-bearing structure of the entire mechanism; a rotary support device 502 fixedly installed on the support frame 501; a clamping device 503 for directly clamping the simulated borehole 1 and fixedly connected to the rotary support device 502; a fixing device 504 provided on the rotary support device 502 for reliably locking the simulated borehole 1; and an angle sensor 505 provided on the rotary support device 502 for real-time detection and feedback of its rotation angle.

[0039] This embodiment describes an experimental simulation method for a gas drilling and fluid / slag-carrying experimental device in a coal mine, including the following steps: Step 1, Experimental preparation: Load the dry simulated drill cuttings with a preset particle size distribution into the solid phase supply system and check the sealing and operating status of each system. Step 2, parameter setting: Set the operating parameters for this experiment through the centralized control system, including the simulated borehole inclination angle, gas flow rate, liquid injection flow rate, drill cuttings injection rate, and drill rod rotation speed. Step 3, Start the experiment: First, start the gas injection system and introduce gas at a set flow rate into the simulated borehole through the through hole in the simulated drill rod; then, start the rotation of the simulated drill rod; finally, start the liquid phase injection system and the solid phase supply system and inject clean water and drill cuttings into the bottom of the simulated borehole at a set rate. Step 4, Process Monitoring and Data Acquisition: The gas-liquid-solid three-phase flow state in the annulus is recorded throughout the process using a high-speed camera array; the pressure distribution along the annulus and the pressure drop parameters in specific sections are collected in real time using pressure sensors and differential pressure sensors; the torque and rotational speed of the simulated drill pipe are collected in real time using torque sensors and speed sensors; the collected image, video, pressure, differential pressure, torque, and rotational speed data are transmitted to the centralized control system in real time. Step 5, Result Analysis and Processing: First, stop the injection of drill cuttings, then stop the injection of water, and finally stop the gas injection; perform image analysis based on high-speed camera video to quantify parameters such as drill cuttings transport speed, critical cuttings-carrying gas velocity, and liquid accumulation height; combine pressure and differential pressure data to analyze the friction loss of annular multiphase flow; and analyze the impact of different drilling process parameters on cuttings discharge based on the collected torque and rotational speed data. Step 6: Change one or more operating parameters from Step 2, and repeat Step 3 and Step 4 to conduct comparative experiments, and systematically study the influence of each parameter on the liquid and slag carrying efficiency. Step 7: Change the input parameters of the gas-liquid-solid mixture to form a certain thickness of sediment at the lower edge of the simulated borehole wall; then inject pulsed airflow of specific frequency and amplitude into the simulated borehole through a high-frequency pulse generator to study the mechanism of oscillating shear force on destroying sediment on the lower side of the borehole wall and enhancing liquid carrying capacity. Step 8: After the experiment is completed, treat the wastewater and drilling slag collected by the separation and recovery system; clean the experimental apparatus in preparation for the next experiment.

[0040] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0041] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0042] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A simulated underground gas drilling and fluid / slag carrying experimental device for coal mines, characterized in that, It includes a drilling simulation system, a gas injection system, a liquid injection system, a solid phase supply system, a data acquisition and monitoring system, a separation and recovery system, and a centralized control system; The drilling simulation system includes a simulated borehole (1), a simulated drill rod (2) extending into the simulated borehole (1), a simulated drill bit (3) connected to the front end of the simulated drill rod (2), a motor (4) connected to the rear end of the simulated drill rod (2), and a simulated angle adjustment mechanism (5) that can support and adjust the angle of the simulated borehole (1). The gas injection system includes an air compressor (8), a gas storage tank (9), a pressure regulating valve (10) and a gas flow meter (11) connected in sequence through a gas supply pipeline (12) and connected to the borehole of the simulated borehole (1); The liquid injection system includes a liquid storage tank (14), a liquid pump (15), a liquid flow meter (16) and a liquid regulating valve (17) connected in sequence through a liquid supply pipeline (18) and connected to multiple radial liquid injection holes (7) to the side wall of the simulated borehole (1). The solid phase supply system includes a cuttings storage bin (19) and a cuttings feeding device (20) connected thereto. The cuttings feeding device (20) is connected to the bottom of the simulated borehole (1) to transport cuttings. The data acquisition and monitoring system includes a high-speed camera group (21) located outside the simulated borehole (1), a pressure sensor (22) located inside the simulated borehole (1), and a differential pressure sensor (23). The separation and recovery system includes a recovery box (24) connected to the outlet of the simulated borehole (1), a filter screen (25) inside the recovery box (24), and a conduit (26) on the top of the recovery box (24). The centralized control system is connected to the gas injection system, liquid injection system, solid phase supply system, data acquisition and monitoring system, and separation and recovery system via data lines. It centrally sets and controls all experimental parameters and receives, processes, displays, and stores monitoring data and video data from each sensor in real time.

2. The experimental device for simulating underground gas drilling with fluid and slag carrying in coal mines as described in claim 1, characterized in that, The simulated borehole (1) is made of high-strength transparent organic glass; the front end of the simulated drill rod (2) is connected to the simulated drill bit (3) by a thread, and both the simulated drill rod (2) and the simulated drill bit (3) are built into the simulated borehole (1); the motor (4) is connected to the rear end of the simulated drill rod (2) by a coupling (6); the simulated angle adjustment mechanism (5) is located below the entire simulated borehole (1) to support and fix it; The simulated drill rod (2) is a drill rod with a replaceable structure, including an outer flat drill rod, a spiral drill rod, and a triangular spiral drill rod.

3. The experimental device for simulating underground gas drilling with fluid and slag carrying in coal mines as described in claim 1, characterized in that, The gas supply pipeline (12) is equipped with a high-frequency pulse generator (13) to generate pulsed airflow with a specific frequency and amplitude, simulating the mechanism of oscillating shear force in destroying borehole sediment and enhancing liquid and sediment carrying capacity.

4. The experimental device for simulating underground gas drilling with fluid and slag carrying in coal mines as described in claim 1, characterized in that, The cuttings storage bin (19) includes multiple independent chambers. Different particle sizes of cuttings are preloaded into the independent chambers, and the opening and closing of the independent chambers are controlled by electromagnetic valves. The cuttings are mixed in a preset ratio or transported to the simulated borehole (1) through the cuttings feeding device (20) in a specific time sequence to simulate the heterogeneous cuttings generated by complex broken coal seams.

5. The experimental device for simulating underground gas drilling with fluid and slag carrying in coal mines as described in claim 4, characterized in that, The drill cuttings storage bin (19) includes a coal sample chamber (1901) and a gangue chamber (1902). The coal sample chamber (1901) has multiple chambers containing coal samples with different strength coefficients; The gangue chamber (1902) was filled with coal gangue; Both the coal sample chamber (1901) and the gangue chamber (1902) are equipped with electromagnetic valves (1903) and conveying pipelines (1904) at their lower outlets, and are connected to slag collectors (1905) through the conveying pipelines (1904); the slag collectors (1905) are connected to negative pressure pipelines (1907) to provide slag discharge power to the coal sample chamber (1901) and the gangue chamber (1902); A stirrer (1906) is connected below the slag collector (1905). The bottom of the cuttings storage bin (19) is conical (1908); a vibrator (1909) is installed on the outside of the bottom of the conical structure (1908).

6. The experimental device for simulating underground gas drilling with fluid and slag carrying in coal mines as described in claim 5, characterized in that, The cuttings feeding device includes a screw feeder (2001) and a stepper motor (2002). A vibrator (1909) is connected to the screw feeder (2001) through a flexible conveying pipe (19010). The outlet of the screw feeder (2001) is connected to the injection point at the bottom of the simulated borehole (1) through the flexible conveying pipe (19010).

7. The experimental device for simulating underground gas drilling with fluid and slag carrying in coal mines as described in claim 1, characterized in that, The high-speed camera group (21) includes multiple high-speed cameras, which are spaced apart on the outside of the transparent simulated borehole (1); the pressure sensors (22) are spaced apart along the inside of the simulated borehole (1); the differential pressure sensors (23) are placed in a specific section inside the simulated borehole (1); the high-speed cameras are equipped with a particle image velocity measurement module.

8. The experimental device for simulating underground gas drilling with fluid and slag carrying in coal mines as described in claim 1, characterized in that, After the gas-liquid-solid mixture discharged from the simulated borehole (1) enters the recovery tank (24), the gas is discharged into the atmosphere through the conduit (26); after the liquid and fine particles pass through the filter screen (25), the drill cuttings particles are intercepted by the filter screen (25), and the liquid is collected and processed uniformly at the bottom of the recovery tank (24).

9. The experimental device for simulating underground gas drilling with fluid and slag carrying in coal mines as described in claim 1, characterized in that, The simulated angle adjustment mechanism (5) includes: a support frame (501) as the basic load-bearing structure of the entire mechanism; a rotary support device (502) fixedly installed on the support frame (501); a clamping device (503) for directly clamping the simulated borehole (1) and fixedly connected to the rotary support device (502); a fixing device (504) provided on the rotary support device (502) to realize the reliable locking of the simulated borehole (1); and an angle sensor (505) provided on the rotary support device (502) to detect and feedback its rotation angle in real time.

10. The experimental simulation method of the simulated coal mine underground gas drilling fluid-carrying and slag-carrying experimental device according to any one of claims 1 to 9, characterized in that, Includes the following steps: Step 1, Experimental preparation: Load the dry simulated drill cuttings with a preset particle size distribution into the solid phase supply system and check the sealing and operating status of each system. Step 2, parameter setting: Set the experimental operating parameters through the centralized control system, including the simulated borehole inclination angle, gas flow rate, liquid injection flow rate, drill cuttings injection rate, and drill rod rotation speed. Step 3, Start the experiment: First, start the gas injection system and introduce gas at a set flow rate into the simulated borehole through the through hole in the simulated drill rod; then, start the rotation of the simulated drill rod; finally, start the liquid phase injection system and the solid phase supply system and inject clean water and drill cuttings into the bottom of the simulated borehole at a set rate. Step 4, Process Monitoring and Data Acquisition: The gas-liquid-solid three-phase flow state in the annulus is recorded in its entirety by a high-speed camera group; the pressure distribution along the annulus and the pressure drop parameters of specific sections are collected in real time by pressure sensors and differential pressure sensors; the torque and speed of the simulated drill pipe are collected in real time by deploying torque sensors and speed sensors; the collected data are transmitted to the centralized control system in real time. Step 5, Result Analysis and Processing: First, stop the injection of drill cuttings, then stop the injection of water, and finally stop the gas injection; perform image analysis based on high-speed camera video to quantify the parameters of drill cuttings transport speed, critical cuttings-carrying gas velocity, and liquid accumulation height; combine pressure and differential pressure data to analyze the friction loss of annular multiphase flow; and analyze the influence of different drilling process parameters on cuttings discharge based on the collected torque and rotational speed data. Step 6: Change one or more operating parameters from Step 2, and repeat Step 3 and Step 4 to conduct comparative experiments and study the influence of each parameter on the liquid and slag carrying efficiency. Step 7: Change the input parameters of the gas-liquid-solid mixture to form sediment at the lower edge of the simulated borehole wall; then inject pulsed airflow of specific frequency and amplitude into the simulated borehole through a high-frequency pulse generator to study the mechanism of oscillating shear force on destroying sediment on the lower side of the borehole wall and enhancing liquid carrying capacity. Step 8: After the experiment is completed, treat the wastewater and drilling slag collected by the separation and recovery system.

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