Coal seam gas radial flow simulation device and method under negative pressure extraction conditions

Abstract

The present invention discloses a device and method for simulating radial flow of coal seam gas under negative pressure extraction conditions, and relates to the technical field of gas radial flow simulation test, wherein an axial pressure and confining pressure loading system is used to load axial pressure and confining pressure on a first coal sample holder, a second coal sample holder, a third coal sample holder and a fourth coal sample holder, respectively, to simulate coal bodies under different stress states around the extraction borehole; then, a vacuum system is used to perform vacuum treatment on the coal samples in the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder; in addition, gas is injected into the coal samples through a gas injection system; and negative pressure is provided for the coal samples in the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder, to realize gas radial flow simulation test of coal bodies under different stress states around the borehole under negative pressure extraction conditions.

Description

Technical Field

[0001] The invention relates to the technical field of gas radial flow simulation testing, and in particular to a device and method for simulating coal seam gas radial flow under negative pressure extraction conditions. Background Art

[0002] Coalbed gas (CBM) is a key factor restricting safe coal mining. As coal mining in China continues to deepen at a rate of 10 to 20 meters per year, the gas pressure and gas content of deep coal seams are gradually increasing, resulting in an increasing number of high-gas and coal and gas outburst mines, and the danger of outbursts in deep coal seams is also increasing. At present, coalbed gas extraction is the most effective method and way to control gas and prevent outbursts. From the perspective of energy development and utilization, coalbed gas is a clean unconventional resource, and its extraction and utilization are of great significance to ensuring coal mine safety, national energy security and improving environmental quality; in particular, the relevant research results on the displacement and extraction of coalbed gas can guide and achieve the increase in production of coalbed gas extraction projects, and can also achieve the burial and storage of greenhouse gases in unminable coal seams.

[0003] Since Academician Zhou Shining proposed the "Radial Unsteady Flow Theory of Coal Seam Gas", a large number of scholars have carried out a lot of research on the simulation calculation of gas seepage in deep coal seams and gas extraction parameters (sealing parameters of boreholes and effective extraction radius, etc.) with Academician Zhou's gas radial flow equation as the core. In particular, extensive research has been carried out on the theory and model of nonlinear seepage of coal seam gas, the determination and simulation calculation of gas extraction parameters, and the numerical solution of coal seam gas flow. A large number of beneficial research results have been achieved, which have better characterized and guided the gas extraction and control work in mines. However, these simulation calculations are based on the gas radial nonlinear seepage equation and use numerical simulation calculation methods to obtain approximate analytical solutions, and obtain the gas pressure distribution expression of the gas radial flow field around the borehole, which approximates the gas pressure distribution law of the reaction radial flow field. Up to now, similar simulation experimental research on the radial flow law of gas in loaded coal seams under negative pressure extraction conditions has not been carried out.

[0004] At the same time, previous gas adsorption and desorption experiments on loaded coal samples and gas permeability experiments on coal samples were all carried out using coal dust or small-sized standard raw coal (coal briquette) as research objects. In fact, the experimental results are greatly affected by the size of the coal samples and their own properties, and it is difficult to truly reflect the gas desorption and seepage laws of coal seams, especially under negative pressure extraction conditions. The gas diffusion, desorption and seepage characteristics in coal seams will be more complicated; therefore, a large number of scholars have to use the gas radial flow equation, Darcy's law and the law of conservation of mass as theoretical premises to establish the seepage equation of gas movement, and use numerical simulation software such as COMSOL to simulate and calculate the gas seepage equation to verify the correctness of the coal seam gas flow field and its flow law.

[0005] From the above analysis, it can be seen that although Academician Zhou Shining’s gas radial seepage equation can better characterize the gas flow law of coal seams, and with the help of relevant numerical simulation software and calculation methods, a simple approximate analytical solution can be obtained, and the gas pressure distribution characteristics and gas flow law around the borehole can be quickly solved, these are closely related to the assumptions of the simulation calculation, the physical parameters of the coal seam itself, the calculation algorithm of the numerical simulation and other related parameters. Sometimes, the relevant numerical simulation verification is acceptable, but in fact it cannot truly reflect the gas desorption and seepage law of coal seams under negative pressure extraction conditions.

[0006] To this end, the following research objectives were achieved through testing and analysis of the coal seam gas radial flow simulation equipment under negative pressure extraction conditions:

[0007] (1) Radial flow characteristics of gas around the extraction borehole in the loaded coal body

[0008] The equipment can simulate and test the radial flow parameters and characteristics of gas in different stress distribution areas of the extraction borehole; it can simulate and test the radial flow parameters and characteristics of coal seam gas under different extraction negative pressures; it can test the gas desorption and seepage parameters and characteristics of loaded coal samples in different axial pressure / confining pressure unloading stages;

[0009] (2) Evolution of seepage law of gas injection displacement in loaded coal bodies

[0010] It can simulate and test the gas seepage parameters and characteristics of loaded coal samples under different gas injection displacement conditions, and realize the comprehensive simulation test of the radial flow characteristics of coal seam gas and the gas injection displacement seepage parameters under negative pressure extraction conditions of loaded coal samples;

[0011] (3) Test and analysis of coal seam gas extraction and control methods

[0012] The influence of stress, negative pressure, flow rate, borehole leakage, gas injection displacement and other parameters on coal seam gas flow during gas extraction is simulated and tested, and the methods of coal seam gas extraction and regulation are explained. Summary of the invention

[0013] To achieve the above object, the present invention provides the following technical solution: a device for simulating radial flow of coal seam gas under negative pressure extraction conditions, comprising:

[0014] A first coal sample holder, a second coal sample holder, a third coal sample holder and a fourth coal sample holder connected in series in sequence;

[0015] An axial pressure and confining pressure loading system, used to load axial pressure and confining pressure on the first coal sample holder, the second coal sample holder, the third coal sample holder, and the fourth coal sample holder, respectively, to simulate coal bodies under different stress states around the extraction borehole; and

[0016] The gas extraction system is used to vacuum the coal samples in the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder, so as to subsequently inject gas into the coal samples through the gas injection system, and then provide negative pressure for the coal samples in the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder, so as to realize the gas radial flow simulation test of the coal body in different stress states around the extraction borehole under negative pressure extraction conditions.

[0017] Further, preferably, the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder are connected to the first pipeline and the second pipeline on both axial sides, the adjacent first pipelines and the second pipelines are connected in series, and the first pipeline on one side of the first coal sample holder is connected to the exhaust system by the seventh pipeline;

[0018] A third pipeline is also connected to one side of the second pipeline, and a gas pressure sensor is arranged on the third pipeline;

[0019] A gas flow meter is provided on the first pipeline;

[0020] The first pipeline is connected to a sixth pipeline, and a negative pressure sensor is arranged on the sixth pipeline.

[0021] Further, as a preference, the vacuum system includes an vacuum pump, an eighth pipeline, a fifth pipeline and a fourth pipeline, wherein the suction end of the vacuum pump is connected to the fifth pipeline via the eighth pipeline, eight fourth pipelines are connected in parallel to the fifth pipeline, four fourth pipelines are connected to the first pipeline one-to-one, and the other four fourth pipelines are connected to the second pipeline one-to-one.

[0022] Further, preferably, the gas supply system comprises a gas source, a buffer bottle and a ninth pipeline connected in sequence, and the ninth pipeline is connected to the second pipeline on one side of the fourth coal sample holder.

[0023] Further, as a preference, the axial pressure and confining pressure loading system includes four confining pressure loading pipes, four axial pressure loading pipes and a constant pressure pump, wherein the four confining pressure loading pipes respectively use a constant pressure pump to provide confining pressure for the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder, and the four axial pressure loading pipes respectively use a constant pressure pump to provide axial pressure for the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder.

[0024] Further, as a preference, the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder have the same structure, and the fourth coal sample holder comprises: a ring tube, a first clamping ring, a second clamping ring and a pressurizing assembly, wherein a first clamping ring is threadedly connected to one side of the ring tube, and a mounting ring is threadedly connected to the other side, and a second clamping ring is threadedly connected in the mounting ring, a first shaft seat slidably connected to the ring tube seal is slidably connected in the first clamping ring, a first through hole is provided in the middle of the first shaft seat for communicating with the first pipeline, a second shaft seat slidably connected to the ring tube seal is slidably connected in the second clamping ring, a second shaft seat slidably connected to the ring tube seal is provided in the middle of the second clamping ring, and a second through hole is provided in the middle of the second shaft seat for communicating with the second pipeline, a guide ring connected to the ring tube seal is fixed on one side of the mounting ring, the guide ring is used to provide guidance for the second shaft seat, a flexible tube is connected between the guide ring and the first shaft seat, a flow channel is provided on the second clamping ring for connecting to the axial pressure loading pipe, and the ring tube is also connected to the confining pressure loading pipe.

[0025] Further, as a preference, a pressurizing assembly is also rotatably connected in the ring cylinder, and the pressurizing assembly is driven by a pressurizing drive assembly, and the pressurizing assembly includes a pressurizing ring, a pressurizing arc plate, a first pressurizing rod and a second pressurizing rod, wherein a plurality of groups of first pressurizing rods and a plurality of groups of second pressurizing rods are distributed in the circumferential direction of the pressurizing ring, each group of first pressurizing rods is a plurality of axially distributed, and each group of second pressurizing rods is a plurality of axially distributed, the first pressurizing rod is radially slidably embedded in the pressurizing ring, and is connected to the pressurizing ring by a first reset sleeve, and the first pressurizing rod has a first magnetic block at one end close to the pressurizing drive assembly; the second pressurizing rod is radially slidably embedded in the pressurizing ring, and is connected to the pressurizing ring by a second reset sleeve, and the second pressurizing rod has a second magnetic block at one end close to the pressurizing drive assembly; a plurality of first pressurizing rods are commonly connected to a pressurizing arc plate at one end away from the pressurizing drive assembly;

[0026] The pressurizing driving assembly is embedded with a plurality of electromagnetic driving blocks corresponding to the first magnetic block and the second magnetic block.

[0027] Further, preferably, the magnetic pole of the electromagnetic driving block is changeable.

[0028] A method for simulating radial flow of coal seam gas under negative pressure extraction conditions comprises the following steps:

[0029] S1. Place the coal sample into the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder;

[0030] S2. A first coal sample holder, a second coal sample holder, a third coal sample holder and a fourth coal sample holder connected in series in sequence;

[0031] S3. Using the axial pressure and confining pressure loading system to load the first coal sample holder, the second coal sample holder, the third coal sample holder, and the fourth coal sample holder with axial pressure and confining pressure respectively;

[0032] S4. Using the exhaust system to vacuum the coal samples in the first coal sample holder, the second coal sample holder, the third coal sample holder, and the fourth coal sample holder;

[0033] S5. injecting gas into the coal sample through the gas injection system;

[0034] S6. Provide negative pressure for the coal samples in the first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder to realize the radial flow simulation of coal seam gas under negative pressure extraction conditions.

[0035] The first coal sample holder, the second coal sample holder, the third coal sample holder and the fourth coal sample holder are all provided with a pressurizing component, and the pressurizing component can change the regional confining pressure of a certain area or the point confining pressure of a certain area.

[0036] Compared with the prior art, the present invention provides a device and method for simulating radial flow of coal seam gas under negative pressure extraction conditions, which has the following beneficial effects:

[0037] In the embodiments of the present invention, the radial gas flow parameters and characteristics of different stress distribution areas in the extraction borehole can be tested and analyzed; the radial flow parameters and characteristics of coal seam gas under different extraction negative pressures can be tested and analyzed; the gas desorption and seepage parameters and characteristics of loaded coal samples in different axial pressure / confining pressure unloading stages can be tested and analyzed; the gas seepage parameters and characteristics of loaded coal samples under different gas injection displacement conditions can be tested and analyzed; the evolution law of borehole gas flow characteristics and extraction parameters under different leakage conditions can be tested and analyzed. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a structural schematic diagram of a coal seam gas radial flow simulation device under negative pressure extraction conditions;

[0039] Figure 2 It is a structural schematic diagram of a fourth coal sample holder in a coal seam gas radial flow simulation device under negative pressure extraction conditions;

[0040] Figure 3 It is a structural schematic diagram of a pressurizing component and a pressurizing driving component in a coal seam gas radial flow simulation device under negative pressure extraction conditions;

[0041] Figure 4 It is a simulation schematic diagram of a coal seam gas radial flow simulation device under negative pressure extraction conditions;

[0042] In the figure: 1, the first coal sample holder; 2, the second coal sample holder; 3, the third coal sample holder; 4, the fourth coal sample holder; 5, the confining pressure loading pipe; 6, the axial pressure loading pipe; 8, the constant pressure pump; 9, the first pipeline; 10, the second pipeline; 11, the third pipeline; 12, the fourth pipeline; 13, the fifth pipeline; 14, the sixth pipeline; 15, the seventh pipeline; 16, the eighth pipeline; 17, the gas source; 18, the buffer bottle; 19, the ninth pipeline; 2 0. The tenth pipeline; 41. The ring cylinder; 42. The first retaining ring; 43. The first shaft seat; 44. The mounting ring; 45. The guide ring; 46. The second retaining ring; 47. The second shaft seat; 48. The flexible cylinder; 49. The pressurizing assembly; 410. The pressurizing drive assembly; 491. The pressurizing ring; 492. The pressurizing arc plate; 493. The first pressurizing rod; 494. The first reset sleeve; 495. The second pressurizing rod; 496. The second reset sleeve; 411. The electromagnetic drive block. DETAILED DESCRIPTION

[0043] Example: See Figures 1 to 4 In an embodiment of the present invention, a device for simulating radial flow of coal seam gas under negative pressure extraction conditions includes:

[0044] A first coal sample holder 1, a second coal sample holder 2, a third coal sample holder 3 and a fourth coal sample holder 4 connected in series in sequence;

[0045] An axial pressure and confining pressure loading system, used for respectively loading axial pressure and confining pressure on the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4; and

[0046] The exhaust system is used to vacuum the coal samples in the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4, so as to subsequently inject coal gas into the coal samples through the gas injection system, and then provide negative pressure for the coal samples in the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4, so as to realize the radial flow simulation of coal seam gas under negative pressure extraction conditions.

[0047] In addition, the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4 are connected to the first pipeline 9 and the second pipeline 10 on both axial sides, and the adjacent first pipelines 9 and the second pipelines 10 are connected in series. The first pipeline 9 on one side of the first coal sample holder 1 is connected to the exhaust system through the seventh pipeline 15;

[0048] One side of the second pipeline 10 is also connected to a third pipeline 11, and a gas pressure sensor is provided on the third pipeline 11;

[0049] The first pipeline 9 is provided with a gas flow meter;

[0050] The first pipeline 9 is connected to a sixth pipeline 14, and a negative pressure sensor is provided on the sixth pipeline 14;

[0051] A tenth pipeline 20 is further disposed on one side of the seventh pipeline 15 .

[0052] Among them, the sixth pipeline 14 on one side of the first coal sample holder 1 can be used as a sampling interface;

[0053] The third pipeline 11 on one side of the first coal sample holder 1, the second coal sample holder 2, and the third coal sample holder 3 can be used as a displacement gas injection / sampling interface;

[0054] The third pipeline 11 on one side of the fourth coal sample holder 4 can be used as a displacement gas injection interface;

[0055] In this embodiment, the radial flow characteristics of coal gas around the extraction borehole under loaded conditions and the seepage law of gas injection displacement can be tested, and a comprehensive simulation test of the radial flow characteristics of coal seam gas and the seepage parameters of gas injection displacement under negative pressure extraction conditions of loaded coal samples can be realized. The effects of parameters such as negative pressure of extraction of loaded coal samples and borehole leakage on the radial flow law of gas can be simulated and studied, and the intelligent regulation of coal seam gas extraction parameters and the mechanism of coal seam gas injection displacement seepage can be simulated and studied.

[0056] Specifically, the vacuum system includes an vacuum pump, an eighth pipeline 16, a fifth pipeline 13 and a fourth pipeline 12, wherein the suction end of the vacuum pump is connected to the fifth pipeline 13 via the eighth pipeline, and eight fourth pipelines 12 are connected in parallel to the fifth pipeline 13, wherein four fourth pipelines 12 are connected to the first pipeline 9 one-to-one, and the other four fourth pipelines are connected to the second pipeline 10 one-to-one.

[0057] The vacuum pump uses a water ring vacuum pump with a stainless steel pump core to simulate coal seam gas extraction. The pump core is made of stainless steel; negative pressure ≥ -88kPa; vacuum degree: ≤6×10 -2 Pa; Pumping speed: 0~22L / s.

[0058] In addition, the gas supply system includes a gas source 17 , a buffer bottle 18 and a ninth pipeline 19 which are connected in sequence. The ninth pipeline 19 is connected to the second pipeline 10 on one side of the fourth coal sample holder 4 .

[0059] The gas supply system uses a gas cylinder group (or a centralized gas supply pipeline) to pre-fill the buffer tank, and controls the air intake pressure and flow rate during extraction to simulate the original coal seam gas source.

[0060] In this embodiment, the axial pressure and confining pressure loading system includes four confining pressure loading pipes 5, four axial pressure loading pipes 6 and a constant pressure pump 8, wherein the four confining pressure loading pipes 5 respectively use constant pressure pumps to provide confining pressure for the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4, and the four axial pressure loading pipes 6 respectively use constant pressure pumps to provide axial pressure for the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4.

[0061] That is to say, the confining pressure and axial pressure in the first coal sample clamp 1, the second coal sample clamp 2, the third coal sample clamp 3 and the fourth coal sample clamp 4 can be adjusted independently, so as to simulate the stress conditions of the coal body in the pressure relief zone, the stress conditions of the coal body in the linear rebound zone, the stress conditions of the coal body in the stress concentration zone and the stress conditions of the coal body in the original rock stress zone respectively.

[0062] It should be noted that the gas flow direction is from the gas injection system to flow through the fourth coal sample holder, the third coal sample holder, the second coal sample holder and the first coal sample holder in sequence;

[0063] The axial pressure / confining pressure loading range is: 0~25MPa.

[0064] In this embodiment, the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4 have the same structure. The fourth coal sample holder comprises: a ring tube 41, a first clamping ring 42, a second clamping ring 46 and a pressurizing assembly 49, wherein one side of the ring tube 41 is threadedly connected with the first clamping ring 42, and the other side is threadedly connected with the mounting ring 44, and the mounting ring 44 is threadedly connected with the second clamping ring 46, and the first clamping ring 42 is slidably connected with a first shaft seat 43 that is sealed and slidably connected with the ring tube 41, and the middle part of the first shaft seat 43 has a first through hole. The through hole is used to communicate with the first pipeline 9. The second retaining ring 46 is slidably connected with the second shaft seat 47 which is slidably connected with the annular tube seal. The middle part of the second shaft seat 47 has a second through hole for communicating with the second pipeline 10. A guide ring 45 which is seal-connected with the annular tube 41 is fixed on one side of the mounting ring 44. The guide ring 45 is used to provide guidance for the second shaft seat. A flexible tube 48 is connected between the guide ring 45 and the first shaft seat 43. A flow channel is opened on the second retaining ring 46 for connecting with the axial pressure loading tube 6. The annular tube 41 is also connected with the confining pressure loading tube 5.

[0065] It should also be noted that, in the present embodiment, valve bodies are provided on the first pipeline, the second pipeline, the third pipeline, the fourth pipeline, the fifth pipeline, the sixth pipeline, the seventh pipeline, the eighth pipeline, the collecting pipe, the ninth pipeline, the tenth pipeline 20, the confining pressure loading pipe and the axial pressure loading pipe, and of course a flow meter may also be provided.

[0066] During implementation, liquid can be injected into the flow channel through the axial pressure loading tube 6, and the liquid pushes the second shaft seat 47 to move axially to achieve axial pressure loading of the coal sample, while liquid can be injected into the annular tube 41 through the confining pressure loading tube, and the liquid can achieve confining pressure loading of the coal sample through the flexible tube 48, and the loaded axial pressure and confining pressure can be adjusted through the valve body.

[0067] In addition, a pressurizing assembly 49 is rotatably connected in the ring cylinder 41, and the pressurizing assembly 49 is driven by the pressurizing driving assembly 410. The pressurizing assembly 49 includes a pressurizing ring 491, a pressurizing arc plate 492, a first pressurizing rod 493, and a second pressurizing rod 495, wherein the pressurizing ring 491 is provided with a plurality of groups of first pressurizing rods 493 and a plurality of groups of second pressurizing rods 495 distributed in the circumferential direction, each group of first pressurizing rods 493 is a plurality of axially distributed, each group of second pressurizing rods 495 is a plurality of axially distributed, and the first pressurizing rods The first pressure rod is radially slidably embedded in the pressure ring 491 and connected to the pressure ring 491 by a first reset sleeve 494. The first pressure rod has a first magnetic block at one end close to the pressure drive assembly 410. The second pressure rod is radially slidably embedded in the pressure ring 491 and connected to the pressure ring 491 by a second reset sleeve 496. The second pressure rod has a second magnetic block at one end close to the pressure drive assembly 410. The ends of the multiple first pressure rods away from the pressure drive assembly 410 are commonly connected to a pressure arc plate 492.

[0068] The pressurizing driving assembly 410 has a plurality of electromagnetic driving blocks 411 embedded therein corresponding to the first magnetic block and the second magnetic block.

[0069] In addition, the magnetic pole of the electromagnetic driving block 411 is changeable.

[0070] Therefore, when the magnetic poles of the electromagnetic drive block 411 are adjusted to be able to attract each other with the first magnetic block, the pressurizing component 49 can be driven to rotate by driving the pressurizing drive component 410 to rotate. At this time, the position of the pressurizing arc plate 492 and the position of the second pressurizing rod can be adjusted. Thereafter, the magnetic poles of some electromagnetic drive blocks 411 are adjusted again to selectively drive the pressurizing plate 492 for regional pressurization, or selectively drive the second pressurizing rod for point pressurization, thereby simulating the uneven pressure of coal blocks in a certain area.

[0071] A method for simulating radial flow of coal seam gas under negative pressure extraction conditions comprises the following steps:

[0072] S1. Place the coal sample into the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4;

[0073] S2. A first coal sample holder 1, a second coal sample holder 2, a third coal sample holder 3 and a fourth coal sample holder 4 connected in series in sequence;

[0074] S3. Using the axial pressure and confining pressure loading system, the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4 are respectively loaded with axial pressure and confining pressure;

[0075] S4. Using the exhaust system to vacuum the coal samples in the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4;

[0076] S5. injecting gas into the coal sample through the gas injection system;

[0077] S6. Provide negative pressure for the coal samples in the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4 to realize a gas radial flow simulation test of coal bodies in different stress states around the borehole under negative pressure extraction conditions.

[0078] The first coal sample holder 1 , the second coal sample holder 2 , the third coal sample holder 3 and the fourth coal sample holder 4 are all provided with a pressurizing assembly 49 , and the pressurizing assembly 49 can change the regional confining pressure of a certain area or the point confining pressure of a certain area.

[0079] Among them, the above settings can be used to analyze the radial gas flow parameters and characteristics of different stress distribution areas in the extraction borehole;

[0080] In addition, the gas extraction system is used to provide negative pressure to the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4, so as to test and analyze the radial flow parameters and characteristics of coal seam gas under different extraction negative pressures;

[0081] In addition, the axial pressure and confining pressure loading system is used to load the axial pressure on the first coal sample holder 1, the second coal sample holder 2, the third coal sample holder 3 and the fourth coal sample holder 4 respectively. The loading / unloading of the confining pressure can test and analyze the gas desorption and seepage parameters and characteristics of the loaded coal samples at different axial pressure / confining pressure unloading stages;

[0082] In addition, the third pipeline 11 on one side of the first coal sample holder 1, the second coal sample holder 2, and the third coal sample holder 3 can be used as a displacement gas injection / sampling interface;

[0083] The third pipeline 11 on one side of the fourth coal sample holder 4 can be used as a displacement gas injection interface, so the displacement gas injection interface can be used to test and analyze the gas seepage parameters and characteristics of the loaded coal sample under different gas injection displacement conditions;

[0084] In addition, by switching the valve on the tenth pipeline, the flow characteristics of the borehole gas and the regulation rules of the extraction parameters under different leakage conditions can be tested and analyzed.

[0085] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A device for simulating radial flow of coal seam gas under negative pressure extraction conditions, characterized in that: include: A first coal sample holder (1), a second coal sample holder (2), a third coal sample holder (3) and a fourth coal sample holder (4) connected in series in sequence; An axial pressure and confining pressure loading system is used to load axial pressure and confining pressure on the first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4), respectively, to simulate the coal bodies under different stress states around the extraction borehole; as well as The gas extraction system is used to perform vacuum extraction on the coal samples in the first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4), so as to subsequently inject gas into the coal samples through the gas injection system, and then provide negative pressure for the coal samples in the first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4), so as to realize the gas radial flow simulation test of the coal body in different stress states around the extraction borehole under negative pressure extraction conditions; The axial pressure and confining pressure loading system comprises four confining pressure loading pipes (5), four axial pressure loading pipes (6) and a constant pressure pump (8), wherein the four confining pressure loading pipes (5) respectively use a constant pressure pump to provide confining pressure for the first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4), and the four axial pressure loading pipes (6) respectively use a constant pressure pump to provide axial pressure for the first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4); The first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4) have the same structure. The fourth coal sample holder comprises: a ring tube (41), a first clamping ring (42), a second clamping ring (46) and a pressurizing assembly (49), wherein one side of the ring tube (41) is threadedly connected with the first clamping ring (42), and the other side is threadedly connected with the mounting ring (44), and the mounting ring (44) is threadedly connected with the second clamping ring (46), and the first clamping ring (42) is slidably connected with a first shaft seat (43) which is sealingly and slidably connected to the ring tube (41), and the middle part of the first shaft seat (43) has a first through hole , used to communicate with the first pipeline (9), the second retaining ring (46) is slidably connected with a second shaft seat (47) which is slidably connected with the ring tube, the middle part of the second shaft seat (47) has a second through hole, which is used to communicate with the second pipeline (10), one side of the mounting ring (44) is fixed with a guide ring (45) which is sealed and connected with the ring tube (41), the guide ring (45) is used to provide guidance for the second shaft seat, a flexible tube (48) is connected between the guide ring (45) and the first shaft seat (43), the second retaining ring (46) is provided with a flow channel, which is used to connect with the axial pressure loading tube (6), and the ring tube (41) is also connected with the confining pressure loading tube (5); A pressurizing assembly (49) is also rotatably connected in the annular cylinder (41), and the pressurizing assembly (49) is driven by a pressurizing driving assembly (410). The pressurizing assembly (49) includes a pressurizing ring (491), a pressurizing arc plate (492), a first pressurizing rod (493) and a second pressurizing rod (495), wherein a plurality of groups of first pressurizing rods (493) and a plurality of groups of second pressurizing rods (495) are distributed in the circumferential direction of the pressurizing ring (491), each group of first pressurizing rods (493) is a plurality of axially distributed, each group of second pressurizing rods (495) is a plurality of axially distributed, and the first The pressurizing rod is radially slidably embedded in the pressurizing ring (491) and is connected to the pressurizing ring (491) by a first reset sleeve (494); the end of the first pressurizing rod close to the pressurizing drive assembly (410) has a first magnetic block; the second pressurizing rod is radially slidably embedded in the pressurizing ring (491) and is connected to the pressurizing ring (491) by a second reset sleeve (496); the end of the second pressurizing rod close to the pressurizing drive assembly (410) has a second magnetic block; the ends of the multiple first pressurizing rods away from the pressurizing drive assembly (410) are commonly connected to a pressurizing arc plate (492); The pressurizing drive component (410) is embedded with a plurality of electromagnetic drive blocks (411) corresponding to the first magnetic block and the second magnetic block; The magnetic pole of the electromagnetic driving block (411) is changeable.

2. The device for simulating radial flow of coal seam gas under negative pressure extraction conditions according to claim 1, characterized in that: The first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4) are connected to the first pipeline (9) and the second pipeline (10) on both axial sides, the adjacent first pipelines (9) and second pipelines (10) are connected in series, and the first pipeline (9) on one side of the first coal sample holder (1) is connected to the exhaust system via a seventh pipeline (15); One side of the second pipeline (10) is also connected to a third pipeline (11), and a gas pressure sensor is provided on the third pipeline (11); The first pipeline (9) is provided with a gas flow meter; The first pipeline (9) is connected to a sixth pipeline (14), and a negative pressure sensor is provided on the sixth pipeline (14).

3. The device for simulating radial flow of coal seam gas under negative pressure extraction conditions according to claim 2, characterized in that: The air extraction system comprises an air extraction pump, an eighth pipeline (16), a fifth pipeline (13) and a fourth pipeline (12), wherein the suction end of the air extraction pump is connected to the fifth pipeline (13) via the eighth pipeline, and eight fourth pipelines (12) are connected in parallel to the fifth pipeline (13), wherein four fourth pipelines (12) are connected to the first pipeline (9) in a one-to-one correspondence, and the other four fourth pipelines are connected to the second pipeline (10) in a one-to-one correspondence.

4. The device for simulating radial flow of coal seam gas under negative pressure extraction conditions according to claim 2, characterized in that: The gas injection system comprises a gas source (17), a buffer bottle (18) and a ninth pipeline (19) which are connected in sequence, and the ninth pipeline (19) is connected to the second pipeline (10) on one side of the fourth coal sample holder (4).

5. A method for simulating radial flow of coal seam gas under negative pressure extraction conditions, which uses a device for simulating radial flow of coal seam gas under negative pressure extraction conditions as claimed in any one of claims 1 to 4, characterized in that: The steps include: S1. Place coal samples into the first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4); S2. A first coal sample holder (1), a second coal sample holder (2), a third coal sample holder (3) and a fourth coal sample holder (4) connected in series in sequence; S3. Using the axial pressure and confining pressure loading system, the first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4) are respectively loaded with axial pressure and confining pressure; S4. Using the vacuum system to vacuum the coal samples in the first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4); S5. injecting gas into the coal sample through the gas injection system; S6. Provide negative pressure for the coal samples in the first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4) to realize the radial flow simulation of coal seam gas under negative pressure extraction conditions.

6. The method for simulating radial flow of coal seam gas under negative pressure extraction conditions according to claim 5, characterized in that: The first coal sample holder (1), the second coal sample holder (2), the third coal sample holder (3) and the fourth coal sample holder (4) are all provided with a pressurizing component (49), and the pressurizing component (49) is capable of changing the regional confining pressure of a certain area or the point confining pressure of a certain area.

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