Dynamic simulation experiment device and method for borehole gas extraction based on partition loading

Abstract

The invention relates to a partition loading drilling gas extraction dynamic simulation experiment device and method, and belongs to the field of coal mine safety. The device comprises an experiment cylinder body, a loading device and an air supply device. A hole sealing section confining pressure pressurizing device, an extraction section confining pressure pressurizing device and an axial pressurizing device are arranged in the experiment cylinder body, and the influence of coal body elasticoplastic deformation on permeability is truly reflected by accurately distinguishing stress loading of a hole sealing section and stress loading of an extraction section; the method comprises the following steps: analyzing a stress state, formulating an experimental scheme, preparing an experimental sample, simulating a loading experiment and analyzing experimental data. By combining drilling construction simulation and negative pressure extraction testing, gas emission rules and leakage characteristics under different hole sealing materials, processes and extraction parameters are systematically analyzed. The technology can accurately test the gas emission rule and the air leakage characteristic of drill holes with different hole sealing processes and hole sealing parameters under negative pressure extraction, and provides a scientific basis for optimizing the gas extraction process and improving the extraction efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of mine safety and relates to a dynamic simulation experimental device and method for drilling gas extraction with partition loading. Background Art

[0002] Coal mine gas extraction is a key link in ensuring safe production in mines and achieving efficient use of clean energy. It involves a complex system engineering with multiple links such as desorption and migration, drilling and gas collection, sealing and continuous extraction, and pipeline transportation. In the existing technology, a lot of research has been carried out on the optimization of gas extraction technology, mainly focusing on the fields of coal permeability testing, sealing and sealing evaluation, and simulation of pipeline extraction effects. For example, existing technologies use triaxial compression seepage experiments to test the gas flow characteristics of coal under different stress states, or use transient methods to simulate the desorption and migration laws of gas in water-bearing coal seams. In addition, some studies simulate the sealing performance of the sealing section by constructing a confining pressure loading device, or develop a pipeline system to analyze the correlation between extraction negative pressure and gas flow. These technologies provide basic theoretical support for the improvement of gas extraction technology, but still have significant limitations.

[0003] Traditional methods mostly focus on coal permeability testing or static sealing effect evaluation under a single stress environment, and fail to fully restore the elastic-plastic deformation characteristics of the coal body caused by the difference in stress state between the sealing section and the extraction section in the actual borehole. For example, existing devices often use a uniformly distributed confining pressure loading method, which makes it difficult to distinguish the difference in mechanical response between the stress superposition area of ​​the sealing section and the original rock stress area, resulting in deviations between the experimental data and the actual borehole loading state. In addition, most experimental devices only test single parameters such as permeability or sealing, and lack the ability to dynamically simulate the entire process of drilling construction, sealing technology, and negative pressure extraction. Especially in the study of the synergistic effect of air leakage and gas outburst in the sealing section, the data acquisition system of existing technologies is often limited to local parameter monitoring and cannot systematically analyze the extraction rules under the coupling of multiple factors.

[0004] It is worth noting that existing patents have proposed simulating borehole deformation through three-dimensional loading devices or using pipe network systems to study gas flow characteristics under true triaxial stress. However, these methods still have the following problems: First, they fail to achieve differentiated stress loading between the sealing and extraction sections, resulting in an inability to accurately reproduce the dynamic response of coal permeability changes; second, the experimental equipment does not integrate drilling construction and sealing process simulation functions, making it difficult to assess the impact of actual borehole damage on extraction results; third, the data collection dimensionality is insufficient, making it impossible to simultaneously monitor the synergistic effects of multiple parameters such as confining pressure, axial pressure, gas concentration, and leakage, which restricts the construction of theoretical models for extraction process optimization. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an experimental device and method that can simulate the loading state of the borehole in different zones, dynamically restore the entire extraction process, and support multi-parameter collaborative analysis. By accurately distinguishing the stress loading in the sealing section and the extraction section, the impact of the elastic-plastic deformation of the coal body on the permeability is truly reflected. At the same time, combining drilling construction simulation with negative pressure extraction testing, a systematic analysis of the gas emission patterns and leakage characteristics under different sealing materials, processes, and extraction parameters is carried out, thus providing a scientific basis for efficient extraction.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a dynamic simulation experimental device and method for drilling and gas extraction with zoned loading, which is used to truly restore the differentiated loading states of the sealing section and the extraction section during the gas extraction process, and dynamically analyze the full process characteristics of drilling construction, sealing technology and negative pressure extraction.

[0008] A dynamic simulation experimental device for drilling and gas extraction with zoned loading includes an experimental cylinder, a loading device, and an air supply device. The experimental cylinder is equipped with a sealing section confining pressure device, a drainage section confining pressure device, and an axial pressure device. Among them:

[0009] The sealing section confining pressure device includes a sealing section displacement sensor, a sealing section pressurizing piston and a pressure pump. The pressure pump is connected to the injection port of the sealing section confining pressure device through a four-way valve and is used to apply radial confining pressure to the coal and rock samples.

[0010] The extraction section confining pressure device includes a extraction section displacement sensor, a extraction section pressurizing piston and a pressure pump. The pressure pump is connected to the injection port of the extraction section confining pressure device through a four-way valve and is used to apply radial confining pressure to the coal and rock samples.

[0011] The axial pressure device includes an axial displacement sensor, an axial pressure piston and a pressure pump. The pressure pump is connected to the injection port of the axial pressure device through a ball valve and is used to apply axial pressure to the coal and rock samples.

[0012] The gas supply device is connected to the experimental cylinder through the gas injection port and is used to inject methane gas into the coal rock sample to simulate the gas storage environment.

[0013] Optionally, the device further includes a data acquisition device comprising a multi-channel data acquisition instrument and a data acquisition and processing system. The sealing section displacement sensor, the extraction section displacement sensor, and the axial displacement sensor are connected to the multi-channel data acquisition instrument via signal lines. The multi-channel data acquisition instrument is further connected to the data acquisition and processing system via signal lines for real-time acquisition and processing of parameters such as displacement, confining pressure, and axial pressure.

[0014] Optionally, the gas injection port is provided on the plug, and the plug is fixed in the prefabricated hole of the upper pressure cover by a thread, so as to ensure air tightness and facilitate operation.

[0015] Optionally, both the sealing section confining pressure pressurizing device and the extraction section confining pressure pressurizing device are provided with a drain port for controlling the discharge of pressurized fluid or the unloading of the device, thereby achieving flexible adjustment of the loading force.

[0016] Optionally, the coal rock sample is a cube with a size of 500mm×500mm×1000mm, and space is reserved between the edge line of its loaded surface and the edge line of the pad to avoid mutual squeezing of the pads during loading.

[0017] Optionally, the two ends of the experimental cylinder are connected to the upper cover and the lower cover by threads, and the inner side of the lower cover is provided with a movable liquid injection cavity of the axial pressure piston. The bottom of the experimental cylinder is fixed on the base to ensure the stability and sealing of the overall structure.

[0018] A dynamic simulation experimental method for drilling gas extraction with partitioned loading includes the following steps:

[0019] Stress state analysis: Collect the target area coal seam burial depth, the range of the roadway surrounding rock loosening zone and the drilling instability parameters to determine the original stress and superimposed stress state of the sealing section and the extraction section;

[0020] Experimental plan formulation: Based on the stress analysis results, set the confining pressure loading parameters, axial pressure loading parameters, pore pressure injection balance value and experimental operation steps;

[0021] Experimental sample preparation: The coal rock samples were cut into cubes and placed into the experimental cylinder. Non-current experimental samples were sealed with plastic wrap and wax to maintain their original state.

[0022] Simulated loading experiment: by loading confining pressure, axial pressure and pore pressure in stages, the real coal and rock loading environment is simulated;

[0023] Experimental data analysis: Based on the collected displacement, confining pressure, axial pressure, gas concentration and leakage data, a correlation model between sealing process parameters and gas migration and diffusion mechanism was established.

[0024] Optionally, the simulated loading experiment specifically includes:

[0025] Air tightness test: Inject inert gas into the experimental device, let it stand and detect the pressure change, and continue the experiment after confirming that there is no leakage;

[0026] Confining pressure and axial pressure loading: According to the experimental plan, the confining pressure and axial pressure are alternately loaded to the target value to simulate the three-dimensional stress state of coal rock;

[0027] Pore ​​pressure injection: inject methane gas in stages to the set pressure, record the injection time and equilibrium time, and the adsorption equilibrium time can be set to 24 hours;

[0028] Simulated drilling construction: Drill a hole with a depth of 800mm and a diameter of 42mm in the sample after adsorption equilibrium, and monitor the gas concentration at the hole, the quality of the drill cuttings, the axial confining pressure, and the strain value in real time;

[0029] Sealing and extraction: After sealing the holes with designated sealing technology and materials, connect them to the negative pressure extraction system to detect the gas outburst volume and air leakage volume under different negative pressure conditions.

[0030] Optionally, during the pore pressure injection process, balanced gas injection in stages can ensure uniform gas distribution inside the coal rock sample, and the adsorption equilibrium time is preferably 24 hours.

[0031] Optionally, during the drilling construction stage, the gas concentration at the borehole, the quality of the drill cuttings, the shaft confining pressure, and the strain value are monitored in real time to evaluate the impact of the drilling construction on the coal body damage and gas release.

[0032] Through the above-mentioned device and method, the present invention can accurately simulate the differentiated stress loading state of the sealing section and the extraction section, dynamically restore the entire gas extraction process, and systematically analyze the extraction rules under the action of multi-parameter coupling, providing a scientific basis for optimizing the gas extraction process.

[0033] The beneficial effects of the present invention are:

[0034] This invention significantly improves the authenticity, controllability, and theoretical support of gas extraction experiments through innovative partitioned loading structure design, dynamic full-process simulation capabilities, and a multi-dimensional data collaborative analysis system. This is specifically reflected in the following aspects:

[0035] 1. Partition loading technology accurately restores the differentiated loading state of drilling

[0036] Traditional experimental devices often use a uniformly distributed loading method, which makes it difficult to distinguish the stress difference between the sealing section and the extraction section, resulting in a deviation between the simulation results and the actual borehole loading state. The present invention independently sets a sealing section confining pressure pressurization device, an extraction section confining pressure pressurization device and an axial pressure pressurization device, and combines the coordinated control of the first pressure pump, the second pressure pump and the third pressure pump to apply differentiated radial confining pressure and axial pressure to the sealing section and the extraction section respectively. For example, the sealing section can simulate a high confining pressure environment to reflect the sealing requirements of the sealing material, while the extraction section simulates the coal body damage state during gas release through low confining pressure. This partitioned loading technology can truly restore the mechanical distribution characteristics of the "three zones" (stress superposition zone, original rock stress zone, and damage zone) circumferentially of the borehole, and provide high-precision experimental conditions for studying the influence of coal body elastic-plastic deformation on permeability.

[0037] 2. Dynamic full-process simulation improves experimental authenticity

[0038] Existing technologies are mostly limited to static testing of a single link (such as permeability or sealing effect), and are unable to dynamically simulate the full-process coupling effects of drilling construction, sealing and continuous extraction, and negative pressure extraction. The experimental device of the present invention combines the gas injection port with the gas cylinder to achieve staged balanced injection of the pore pressure inside the coal rock sample, accurately simulating the coal seam gas storage environment. Subsequently, by simulating the drilling construction steps, the orifice gas concentration, drill cuttings quality, axial confining pressure, and strain value during the drilling process are monitored in real time to evaluate the cumulative effect of drilling construction on coal body damage. Finally, by connecting to the negative pressure extraction system, the gas outburst law and air leakage characteristics under different sealing materials and processes are dynamically tested. This full-process simulation capability can systematically reveal the dynamic relationship between extraction process parameters and coal body response, and provide a high-reliability reference for actual underground working conditions.

[0039] 3. Multi-dimensional data collaborative analysis and optimization of process models

[0040] The data acquisition system of traditional experimental devices is often limited to a single parameter (such as confining pressure or gas concentration), which makes it difficult to support multi-factor coupled analysis. This invention integrates a multi-channel data acquisition instrument with a data acquisition and processing system to simultaneously collect the following parameters:

[0041] Mechanical parameters: Sealing section displacement sensor, extraction section displacement sensor and axial displacement sensor provide real-time feedback of coal body strain;

[0042] Fluid parameters: data such as gas injection pressure, gas concentration, leakage rate, etc. dynamically reflect gas migration characteristics;

[0043] Process parameters: negative pressure value, sealing material properties, drilling construction speed and other operating variables.

[0044] Through the collaborative analysis of the above data, a quantitative model of sealing process parameters and gas migration and diffusion mechanisms can be established, for example:

[0045] Variation of coal permeability under different confining pressure gradients;

[0046] The correlation between the elastic modulus of sealing materials and the air leakage rate;

[0047] Dynamic equilibrium relationship between negative pressure extraction efficiency and borehole damage degree.

[0048] This multi-dimensional data analysis capability provides a scientific basis for optimizing extraction processes and reducing the risk of gas outbursts.

[0049] 4. Modular structure design improves experimental flexibility and scalability

[0050] The test cylinder, upper gland and lower gland of this device are connected by threaded connections to achieve quick assembly and disassembly, making it easy to replace coal and rock samples of different sizes or adjust the loading configuration. For example:

[0051] The discharge port and the injection pressure port are connected by a high-pressure hose, which supports dynamic adjustment of the loading force and rapid unloading;

[0052] The stability design of the base ensures the safety of the device when loaded with high confining pressure.

[0053] In addition, by replacing the sensor type or expanding the data acquisition channel, this device can be further applied to related research in the fields of coalbed methane development, shale gas seepage, etc., and has strong technical scalability.

[0054] 5. Significantly reduce downhole testing risks and costs

[0055] Traditional downhole experiments have problems such as interference with production, high safety risks, and difficulty in data collection. This invention can replace some downhole experiments through high-precision simulation in a laboratory environment, significantly reducing the following costs:

[0056] Safety cost: Avoid the risk of accidents caused by unknown environmental hazards when conducting relevant observation experiments underground;

[0057] Time cost: Full-process simulation can complete the parameter verification cycle of traditional underground wells that takes several months in a few days;

[0058] Economic cost: Reduce the trial-and-error losses of sealing materials, extraction equipment and manpower.

[0059] For example, by comparing the leakage data of different sealing processes, the optimal solution can be directly screened out, reducing the repetitive investment in large-scale underground experiments.

[0060] In summary, this invention, through the organic combination of partitioned loading technology, dynamic full-process simulation, multidimensional data analysis, and modular design, not only addresses core issues in existing technologies, such as stress simulation distortion, single data dimension, and lack of theoretical support for process optimization, but also provides a key technical platform for intelligent and efficient mine gas extraction. Its application will promote the upgrading of gas disaster prevention and control technologies and contribute to the clean utilization of coalbed methane resources under the "dual carbon" goals.

[0061] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0063] Figure 1The actual loading condition of the drilling hole;

[0064] Figure 2 is a cross-sectional view of the device;

[0065] Figure 3 This is the plan view of the device;

[0066] Figure 4 This is a schematic diagram of the device connection;

[0067] Figure 5 Flow chart of the method.

[0068] Figure numerals: 1 gas injection port, 2 plug, 3 upper pressure cover, 4 sealing section pad, 5 sealing section confining pressure pressurizing device, 6 sealing section displacement sensor, 7 extraction section confining pressure pressurizing device, 8 extraction section displacement sensor, 9 extraction section pad, 10 lower pressure cover, 11 cylinder body, 12 sealing section pressurizing piston, 13 extraction section pressurizing piston, 14 axial pressurizing piston, 15 drainage port, 16 axial pressure pressurizing device, 17 liquid injection pressure port, 18 axial displacement sensor, 19 coal and rock sample, 20 base, 21 gas cylinder, 22 first pressure pump, 23 second pressure pump, 24 third pressure pump, 25 multi-channel data acquisition instrument, 26 data acquisition and processing system. DETAILED DESCRIPTION

[0069] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0070] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0071] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0072] See also Figures 1 to 5 The dynamic simulation experimental device and method for gas extraction by partitioned loading drilling of the present invention are implemented by the following specific implementation steps:

[0073] 1. Experimental device structure and connection relationship

[0074] Main structure

[0075] The experimental apparatus is centered around cylinder 11, a cylindrical, sealed chamber housing a coal and rock sample 19. Threaded connections connect the upper and lower glands 3 and 10 at either end of cylinder 11. Inside the lower gland 10 is a movable injection chamber for an axially pressurized piston 14. The bottom of cylinder 11 is secured to a base 20 to ensure overall stability.

[0076] The upper gland 3 has a prefabricated gas injection port 1, which is sealed by a plug 2. The plug 2 is threadedly connected to the prefabricated hole of the upper gland 3. The gas injection port 1 is connected to a gas cylinder 21 through a high-pressure hose for injecting methane gas into the coal sample 19.

[0077] Loading System

[0078] The sealing section confining pressure device 5 is located on the side of the cylinder 11 near the upper gland 3 and includes a sealing section pressurizing piston 12, a sealing section displacement sensor 6, and a first pressurizing pump 22. The first pressurizing pump 22 is connected to the injection port 17 of the sealing section confining pressure device 5 via a high-pressure hose and a four-way valve. By injecting pressurized fluid, the first pressurizing pump 22 pushes the sealing section pressurizing piston 12, applying radial confining pressure to the sealing section of the coal and rock sample 19. The sealing section backing plate 4 contacts the coal and rock sample 19, ensuring uniform pressure transmission.

[0079] The extraction section confining pressure device 7 is located below the sealing section confining pressure device 5 and includes a extraction section pressure piston 13, an extraction section displacement sensor 8, and a second pressure pump 23. The second pressure pump 23 is connected to the injection port 17 of the extraction section confining pressure device 7 via a high-pressure hose and a four-way valve. It is used to apply differentiated radial confining pressure to the extraction section of the coal and rock sample 19. The extraction section pad 9 conforms to the surface of the coal and rock sample 19 to reduce stress concentration.

[0080] Axial pressure device 16: Integrated within the lower gland 10, it includes an axial pressure piston 14, an axial displacement sensor 18, and a third pressure pump 24. The third pressure pump 24 is connected to the injection port 17 of the axial pressure device 16 via a high-pressure hose and a ball valve, and is used to apply axial pressure to the coal and rock sample 19.

[0081] Accessibility features

[0082] Drain port 15: Both the sealing section confining pressure pressurizing device 5 and the extraction section confining pressure pressurizing device 7 are provided with a drain port 15 for discharging pressurized liquid or adjusting the loading force after the experiment.

[0083] Data acquisition system: The sealing section displacement sensor 6, the extraction section displacement sensor 8, and the axial displacement sensor 18 are connected to the multi-channel data acquisition instrument 25 through signal lines. The multi-channel data acquisition instrument 25 is further connected to the data acquisition and processing system 26 to collect displacement, confining pressure, axial pressure, gas concentration and leakage data in real time.

[0084] 2. Experimental method implementation steps

[0085] Stress state analysis and experimental plan formulation

[0086] The burial depth of coal seams in the target area, the range of the loosening zone of the tunnel surrounding rock, and the instability parameters of the drilling hole are collected, and the original stress and superimposed stress distribution of the sealing section and the extraction section are analyzed.

[0087] According to the analysis results, the confining pressure loading parameters (target confining pressure values ​​for the sealing section and the extraction section), axial pressure loading parameters, and pore pressure injection balance values ​​are set, and detailed experimental operation steps are formulated.

[0088] Coal and rock sample preparation and installation

[0089] Coal rock samples were collected from the target area and cut into cubic specimens 19 with a size of 500 mm × 500 mm × 1000 mm. Non-current experimental samples were sealed with plastic wrap and wax.

[0090] The sample 19 is loaded into the cylinder 11, and the sealing section shim 4 and the extraction section shim 9 are ensured to fit the surface of the sample 19 to avoid eccentric loading.

[0091] Air tightness detection and initialization

[0092] Close plug 2 of gas injection port 1 and inject inert gas into cylinder 11 via gas cylinder 21 to the set pressure. Wait for 2 hours to monitor the pressure change. If the pressure does not drop, the device is well sealed. If a leak is present, use a foaming agent to locate and repair the leak.

[0093] Release the inert gas to restore the device to its original state.

[0094] Confining pressure and axial pressure loading

[0095] The first pressure pump 22 and the second pressure pump 23 are used to inject pressure fluid into the sealing section confining pressure device 5 and the extraction section confining pressure device 7 respectively, and radial confining pressure is slowly applied to the target value in an alternating loading manner according to the experimental plan.

[0096] Simultaneously, the third pressure pump 24 injects pressure fluid into the axial pressure device 16 to apply axial pressure to a set value. During the loading process, the strain response of the coal rock sample 19 is monitored in real time by the displacement sensors 6, 8, and 18.

[0097] Pore ​​pressure injection and adsorption balance

[0098] Connect gas cylinder 21 to injection port 1. Based on the target gas pressure p in the experimental plan, a phased balanced injection method was used to raise the pore pressure to the target value. Phased balanced injection refers to the pressure increasing from 0 to p1, then to p2, and finally to p. After each injection phase, the injection time and pressure equilibrium time were recorded. The total adsorption equilibrium time was set to 24 hours to ensure uniform gas distribution within the coal rock sample 19.

[0099] Simulated drilling construction and parameter monitoring

[0100] After adsorption equilibrium, the plug 2 was removed, and a hole with a depth of 800 mm and a diameter of 42 mm was vertically drilled into the upper surface of the sample 19 using a drilling device.

[0101] During the drilling process, the gas concentration at the borehole, the quality of the drill cuttings, the shaft confining pressure, and the strain value are monitored in real time to evaluate the impact of the drilling construction on the coal body damage.

[0102] Sealing and negative pressure extraction test

[0103] The borehole is sealed using designated sealing technology and materials, and connected to the negative pressure extraction system.

[0104] Different negative pressure values ​​were set for extraction experiments, and data on gas outburst, air leakage, confining pressure, and axial pressure changes were collected simultaneously to analyze the sealing performance and extraction efficiency of the sealing process.

[0105] Data analysis and model building

[0106] The following theoretical model is established by integrating displacement, confining pressure, axial pressure, gas concentration and leakage data through the data acquisition and processing system 26:

[0107] Quantitative relationship between elastic modulus of sealing material and air leakage rate;

[0108] Dynamic variation of coal permeability under different confining pressure gradients;

[0109] Coupling mechanism between negative pressure extraction efficiency and borehole damage degree.

[0110] 3. Functional description of key components

[0111] Liquid injection and pressure port 17: connected to the pressure pump and loading device to achieve accurate injection and pressure control of the pressure liquid.

[0112] Multi-channel data acquisition instrument 25: supports the simultaneous acquisition of mechanical parameters (displacement, confining pressure, axial pressure) and fluid parameters (gas concentration, leakage).

[0113] Drain port 15: used for quick unloading after the experiment or dynamic adjustment of loading force, improving experimental flexibility.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A dynamic simulation experimental device for drilling gas extraction with partitioned loading, characterized in that: It includes an experimental cylinder (11), a loading device, and an air supply device; The test cylinder (11) is provided with a sealing section confining pressure pressurizing device (5), a pumping section confining pressure pressurizing device (7) and an axial pressure pressurizing device (16) inside; The sealing section confining pressure device (5) comprises a sealing section displacement sensor (6), a sealing section pressurizing piston (12), and a first pressurizing pump (22). The first pressurizing pump (22) is connected to the injection and pressure injection port (17) of the sealing section confining pressure device (5) via a four-way valve, and is used to apply radial confining pressure to the coal and rock sample (19); The extraction section confining pressure device (7) comprises a extraction section displacement sensor (8), a extraction section pressurizing piston (13), and a second pressurizing pump (23). The second pressurizing pump (23) is connected to the injection and pressure injection port (17) of the extraction section confining pressure device (7) via a four-way valve, and is used to apply radial confining pressure to the coal and rock sample (19). The axial pressure device (16) includes an axial displacement sensor (18), an axial pressure piston (14), and a third pressure pump (24). The third pressure pump (24) is connected to the injection port (17) of the axial pressure device (16) through a ball valve and is used to apply axial pressure to the coal and rock sample (19). The air supply device is connected to the experimental cylinder (11) via the air injection port (1).

2. The dynamic simulation experimental device for gas extraction by drilling with partitioned loading according to claim 1 is characterized in that: The invention also includes a data acquisition device, which includes a multi-channel data acquisition instrument (25) and a data acquisition processing system (26). The sealing section displacement sensor (6), the extraction section displacement sensor (8), and the axial displacement sensor (18) are connected to the multi-channel data acquisition instrument (25) via signal lines, and the multi-channel data acquisition instrument (25) is connected to the data acquisition processing system (26) via signal lines.

3. The dynamic simulation experimental device for gas extraction by drilling with partitioned loading according to claim 1 is characterized in that: The gas injection port (1) is provided on the plug (2), and the plug (2) is fixed in the prefabricated hole of the upper pressure cover (3) via a thread.

4. The device according to claim 1, characterized in that The sealing section confining pressure pressurizing device (5) and the extraction section confining pressure pressurizing device (7) are both provided with a liquid discharge port (15) for controlling the discharge of pressurized liquid or unloading the device.

5. The device according to claim 1, characterized in that The coal rock sample (19) is a cube with a size of 500mm×500mm×1000mm, and a space is reserved between the edge line of the load-bearing surface and the edge line of the pad.

6. The device according to claim 1, characterized in that The two ends of the experimental cylinder body (11) are connected to the upper pressure cover (3) and the lower pressure cover (10) respectively through threads, and the inner side of the lower pressure cover (10) is provided with a movable liquid injection cavity for the axial pressure piston (14); the bottom of the experimental cylinder body (11) is fixed on the base (20).

7. A dynamic simulation experimental method for gas extraction by drilling with partition loading, characterized in that: The following steps are involved: Step 1, stress state analysis: Collect the target area coal seam burial depth, the range of the roadway surrounding rock loosening zone and the drilling instability parameters to determine the original stress and superimposed stress state of the sealing section and the extraction section; Step 2, experimental plan formulation: Based on the analysis results of step 1, set the confining pressure loading parameters, axial pressure loading parameters, pore pressure injection balance value and experimental operation steps; Step 3, experimental sample preparation: cut the coal rock sample (19) into cubes and put them into the experimental cylinder (11), and seal the non-current experimental samples with plastic wrap and wax; Step 4, simulate loading experiment: Step 5, experimental data analysis: Based on the collected displacement, confining pressure, axial pressure, gas concentration and leakage data, a correlation model between the sealing process parameters and the gas migration and diffusion mechanism is established.

8. The method according to claim 7, characterized in that The step 4 comprises the following steps: Step 4.1, airtightness test: Inject inert gas into the experimental device, let it stand and detect the pressure change to confirm there is no leakage; Step 4.2, confining pressure and axial pressure loading: alternately load confining pressure and axial pressure to the target value according to the experimental plan; Step 4.3, pore pressure injection: inject methane gas in stages to the set pressure, and record the injection time and equilibrium time; Step 4.4, simulated drilling construction: drill a hole with a depth of 800 mm and a diameter of 42 mm in the sample after adsorption equilibrium, and monitor the gas concentration and strain parameters during the drilling process; Step 4.5, sealing and extraction: Use the specified sealing process and materials to seal the hole, connect to the negative pressure extraction system, and detect the gas outburst pattern and air leakage characteristics under different negative pressure conditions.

9. The method according to claim 8, characterized in that In step 4.3, the adsorption equilibrium time of the pore pressure balanced gas injection in stages is 24 hours.

10. The method according to claim 8, characterized in that In the sub-step 4.4, the gas concentration at the borehole, the quality of the drill cuttings, the axial confining pressure, and the strain value are monitored in real time during the drilling process.

Images