Coal rock permeability testing system based on instantaneous pulse method

Abstract

The utility model discloses a coal rock permeability testing system based on an instantaneous pulse method, which comprises an air inlet system and an industrial personal computer, the air inlet system is connected with an experimental system, the experimental system is connected with an exhaust system, and the exhaust system is connected with a vacuumizing system; the experimental system comprises a coal sample holder, an inlet of the coal sample holder is connected with a gas outlet end of a gas inlet system, and an outlet of the coal sample holder is connected with a gas inlet end of a gas exhaust system; the coal sample holder is respectively connected with a first constant-speed constant-pressure pump and a second constant-speed constant-pressure pump through an axial pressure interface and a confining pressure interface; an adjusting valve is connected between an inlet and an outlet of the coal sample holder, and a differential pressure sensor is connected between an inlet and an outlet of the adjusting valve; an outlet of the coal sample holder is connected with a downstream reference tank through a downstream pipeline; and a downstream pressure gauge and a valve are arranged on the downstream pipeline. The device is convenient to operate and high in measurement precision; the pressure difference can be adjusted through the gas inlet system, the high-stress condition is accurately simulated through the two constant-speed constant-pressure pumps, and the gas seepage characteristics of the low-permeability coal sample under the high-stress condition are tested through experiments.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of coalbed gas exploration and development, and mainly relates to the field of permeability testing of low-permeability coal seams. BACKGROUND

[0002] I. It is necessary to measure the permeability of coal samples under high stress conditions or dense coal samples.

[0003] In the field of coalbed gas exploration and development, understanding the permeability of coal is crucial to understanding the migration of gases such as gas in coal seams.

[0004] With the increasing total energy demand in China, coal resources are gradually being exploited deeper, and coal mining has entered the deep, the mining environment has changed dramatically, the gas content and gas pressure of the coal seam and the ground stress have also risen, resulting in denser coal seams and lower permeability.

[0005] This high stress condition has become the norm for most coal mines, making gas extraction more difficult and further increasing the risk of gas outburst disasters in coal mines. Therefore, it is particularly important to conduct experiments to measure the permeability of coal samples under high stress conditions or dense coal samples.

[0006] II. Introduction to the permeability measurement method.

[0007] The traditional steady-state method for measuring permeability has the characteristics of long measurement time and low efficiency. Under high stress conditions, the permeability of the coal seam is low, and the time to reach steady state will be longer, and it may even be difficult to reach steady state.

[0008] The existing gas expansion method for measuring permeability requires measuring the volume of the pipeline and reference tank in the upstream and downstream, which is relatively complex to operate, especially under high stress conditions, the pore structure of the coal seam is complex, and the gas expansion method is difficult to accurately measure the volume.

[0009] The existing numerical simulation method, due to the difficulty in obtaining accurate geological parameters and boundary conditions under high stress conditions, has affected the accuracy of the numerical simulation method for measuring coal seam permeability.

[0010] The transient method (instantaneous pulse method) is more suitable for coal seam permeability measurement under high stress conditions than other permeability measurement methods. The design idea of the utility model is to design a coal and rock permeability test system based on the instantaneous pulse method, which can simulate high stress conditions and analyze the gas seepage characteristics of low permeability coal samples under high stress conditions. Utility model content

[0011] The utility model aims to provide a coal and rock permeability test system based on the instantaneous pulse method, which simulates high stress conditions and analyzes the gas seepage characteristics of low permeability coal samples under high stress conditions.

[0012] To achieve the above object, the coal rock permeability test system based on the instantaneous pulse method includes a gas inlet system and an industrial computer, the gas inlet system is connected with an experimental system and is used for supplying gas to the experimental system; the experimental system is connected with an exhaust system, the exhaust system is used for discharging gas and fine-tuning pressure; the exhaust system is connected with a vacuum pumping system, the vacuum pumping system is used for pumping vacuum to the experimental system before the experiment;

[0013] The experimental system includes a coal sample holder, the coal sample holder is used for clamping a coal sample for experiment, the inlet of the coal sample holder is connected with the gas outlet end of the gas inlet system, and the outlet of the coal sample holder is connected with the gas inlet end of the exhaust system;

[0014] The coal sample holder has a shaft pressure interface and a confining pressure interface, the coal sample holder is connected with a first constant-speed constant-pressure pump through the shaft pressure interface, and the coal sample holder is connected with a second constant-speed constant-pressure pump through the confining pressure interface;

[0015] The inlet and the outlet of the coal sample holder are connected with an adjusting valve, the inlet and the outlet of the adjusting valve are connected with a differential pressure sensor; the outlet of the coal sample holder is connected with a downstream reference tank through a downstream pipeline, and a downstream pressure gauge and a valve are arranged on the downstream pipeline; the downstream pressure gauge, the differential pressure sensor, the first constant-speed constant-pressure pump and the second constant-speed constant-pressure pump are connected with the industrial computer.

[0016] The gas inlet system includes a gas storage tank used for storing high-pressure gas, the gas storage tank is connected with a buffer tank, and a pressure reducing valve is connected in series on the pipeline between the gas storage tank and the buffer tank; the buffer tank is connected in parallel with an auxiliary pipeline and a main pipeline;

[0017] The auxiliary pipeline is connected with a standard chamber at the tail end, a first gas inlet valve and a second gas inlet valve are connected in series on the auxiliary pipeline, and an upstream pipeline is connected with the auxiliary pipeline between the first gas inlet valve and the second gas inlet valve;

[0018] The tail end of the main pipeline serves as the gas outlet end of the gas inlet system; a third gas inlet valve and a fourth gas inlet valve are connected in series on the main pipeline, the main pipeline between the upstream pipeline and the third gas inlet valve and the fourth gas inlet valve is connected with the upstream pipeline; the upstream pipeline is connected with a pressure sensor at one end and connected with an upstream reference tank at the other end; a downstream pressure gauge is arranged on the main pipeline at the gas outlet end of the gas inlet system;

[0019] The pressure sensor and the upstream pressure gauge are connected with the industrial computer.

[0020] The exhaust system includes an exhaust pipeline, the upstream end of the exhaust pipeline is connected with the outlet of the coal sample holder and the downstream end of the differential pressure sensor; a gas flow meter and an exhaust valve are arranged on the exhaust pipeline, and a fine-tuning valve is arranged on the exhaust pipeline in the downstream direction of the exhaust valve;

[0021] The vacuum pumping system comprises a water ring vacuum pump, an inlet pipeline of the water ring vacuum pump is connected with an exhaust pipeline, the inlet pipeline of the water ring vacuum pump is provided with an air exhaust valve and a negative pressure sensor, and the gas flow meter and the negative pressure sensor are connected with an industrial computer respectively.

[0022] The utility model has the advantages of:

[0023] The utility model discloses simple structure, convenient operation, high measuring accuracy, can adjust pressure difference through the air intake system, and the required axial pressure and confining pressure are accurately adjusted through two constant speed constant pressure pumps, and the gas permeation characteristics of the coal sample under high stress conditions are simulated and tested. The water ring vacuum pump can deaerate the coal sample in the experiment, and can also provide stable and adjustable extraction negative pressure during the experiment.

[0024] The utility model discloses that the first constant speed constant pressure pump and second constant speed constant pressure pump are applied to the coal sample holder with specific axial pressure and confining pressure, so as to simulate the actual coal seam stress state under the target coal seam, and carry out the permeability experiment of the coal sample under high stress conditions. The vacuum pumping system can remove impurity gas interference, and the exhaust system can not only exhaust gas, but also can fine-tune the pressure.

[0025] The buffer tank can provide more stable gas pressure to the downstream, avoid the pressure pulsation phenomenon in the upstream of the experimental system, and is beneficial to the stable performance of the experiment.

[0026] The standard chamber and the pressure sensor are connected, and are used for measuring the volume of the upstream pipeline and the downstream pipeline and the reference tank, providing support for determining the volume change of the gas in the system and then measuring the permeability. The specific structure of the air intake system ensures the accuracy and reliability of the volume measurement.

[0027] The upstream reference tank is located in the upstream of the coal sample holder, and is used for storing high-pressure gas, providing support for applying controllable pressure pulse.

[0028] The vacuum pumping system has simple structure, and can extract system impurity gas and control negative pressure. DETAILED DESCRIPTION

[0029] Figure 1 It is the structure schematic diagram of the utility model. CONCRETE IMPLEMENTING METHOD

[0030] As Figure 1As shown, the coal rock permeability test system based on the instantaneous pulse method of the utility model includes an air inlet system and an industrial computer 26, the air inlet system is connected with an experimental system and is used for supplying air to the experimental system; the experimental system is connected with an air outlet system, the air outlet system is used for discharging gas and fine tuning pressure; the air outlet system is connected with a vacuum pumping system, the vacuum pumping system is used for pumping vacuum to the experimental system before the experiment so as to avoid the influence of impurity gas on the experimental result, especially the coal sample;

[0031] The experimental system includes a coal sample holder 5, the coal sample holder 5 is used for clamping a coal sample to carry out an experiment, the inlet of the coal sample holder 5 is connected with the gas outlet end of the air inlet system, and the outlet of the coal sample holder 5 is connected with the gas inlet end of the air outlet system;

[0032] The coal sample holder 5 has a shaft pressure interface and a confining pressure interface, the coal sample holder 5 is connected with a first constant speed constant pressure pump 41 through the shaft pressure interface, and the coal sample holder 5 is connected with a second constant speed constant pressure pump 42 through the confining pressure interface;

[0033] The inlet and the outlet of the coal sample holder 5 are connected with an adjusting valve 15, and the inlet and the outlet of the adjusting valve 15 are connected with a pressure difference sensor 14; the outlet of the coal sample holder 5 is connected with a downstream reference tank 32 through a downstream pipeline, and a downstream pressure gauge 8 and a valve 7 are arranged on the downstream pipeline; the working pressure of the downstream reference tank 32 is relatively low, and the downstream reference tank 32 can receive the gas released by the coal sample holder 5 to the downstream. The downstream pressure gauge 8, the pressure difference sensor 14, the first constant speed constant pressure pump 41 and the second constant speed constant pressure pump 42 are connected with the industrial computer 26. The line connection of the industrial computer 26 and each component is a conventional technology, and each connection line of the industrial computer 26 is not shown in the figure.

[0034] The first constant speed constant pressure pump 41 and the second constant speed constant pressure pump 42 are used for applying specific shaft pressure and confining pressure to the coal sample holder 5, so as to simulate the actual coal seam stress state under the target coal seam and carry out the permeability experiment of the coal sample under the high stress condition. The vacuum pumping system can eliminate the interference of impurity gas, the air outlet system can not only discharge gas but also fine tune pressure; the initial balance pressure can be formed after the adjusting valve 15 is opened, the pressure difference can be generated after the adjusting valve 15 is closed, and the seepage phenomenon appears and gradually recovers balance again after the adjusting valve 15 is opened again, thereby providing the basis for the permeability experiment.

[0035] The air inlet system includes a gas storage tank 1 used for storing high-pressure gas, the gas storage tank 1 is connected with a buffer tank 2, and a pressure reducing valve 25 is connected in series on the pipeline between the gas storage tank 1 and the buffer tank 2; the buffer tank 2 is connected with an auxiliary pipeline 61 and a main pipeline 62 in parallel;

[0036] The end of the auxiliary pipeline 61 is connected with a standard chamber 22, the first intake valve 24 and the second intake valve 25 are connected in series on the auxiliary pipeline 61, and the auxiliary pipeline 61 between the first intake valve 24 and the second intake valve 25 is connected with the upstream pipeline 63;

[0037] The end of the main pipeline 62 serves as an air outlet end of the intake system, the third intake valve 20 and the fourth intake valve 17 are connected in series on the main pipeline 62, the main pipeline 62 between the upstream pipeline 63 and the third intake valve 20 and the fourth intake valve 17 is connected, one end of the upstream pipeline 63 is connected with the pressure sensor 23, and the other end is connected with the upstream reference tank 31, and the upstream pressure gauge 16 is arranged on the main pipeline 62 at the air outlet end of the intake system;

[0038] The pressure sensor 23 and the upstream pressure gauge 16 are connected with the industrial computer 26, so that the industrial computer 26 can monitor pressure data.

[0039] The buffer tank 2 can provide more stable gas pressure to the downstream, avoids the pressure pulsation phenomenon in the upstream of the experimental system, and is beneficial to the stable performance of the experiment.

[0040] The standard chamber 22 and the pressure sensor 23 are connected, and are used for measuring the volume of the upstream pipeline and the downstream pipeline and the reference tank, so as to provide support for determining the volume change of the gas in the system and then determining the permeability. The specific structure of the intake system ensures the accuracy and reliability of the volume measurement.

[0041] The upstream reference tank 31 is located upstream of the coal sample holder 5 and is used for storing high-pressure gas to provide support for applying a controllable pressure pulse.

[0042] The pipeline valve 19 is preferably arranged on the upstream pipeline 63.

[0043] The exhaust system comprises an exhaust pipeline 64, the upstream end of the exhaust pipeline 64 is connected with the outlet of the coal sample holder 5 and the downstream end of the differential pressure sensor 14, the gas flow meter 65 and the exhaust valve 10 are arranged on the exhaust pipeline 64, and the fine adjustment valve 9 is arranged on the exhaust pipeline 64 in the downstream direction of the exhaust valve 10.

[0044] The vacuum pumping system comprises a water ring vacuum pump 13, the inlet pipeline of the water ring vacuum pump 13 is connected with the exhaust pipeline 64, the inlet pipeline of the water ring vacuum pump 13 is provided with the air exhaust valve 12 and the negative pressure sensor 11, and the gas flow meter 65 and the negative pressure sensor 11 are connected with the industrial computer 26.

[0045] The vacuum pumping system is simple in structure, and can conveniently pump out impurity gas in the system and control negative pressure.

[0046] The process of the high-stress condition low-permeability coal sample experiment by adopting the utility model is as follows:

[0047] 1. Sample and make a coal sample from the simulated target coal seam, and the size of the coal sample matches the coal sample holder 5. Put the coal sample into the coal sample holder 5.

[0048] 2. Turn on the first constant speed and constant pressure pump 41 and the second constant speed and constant pressure pump 42 through the industrial computer 26, and apply a predetermined axial pressure and confining pressure (matching the stress condition of the target coal seam) to the coal sample holder 5, so as to simulate the high stress condition of the target coal seam.

[0049] 3. Close all valves outside the experimental system, open the regulating valve 15, the valve 7, the exhaust valve 12 and the water ring vacuum pump 13, and vacuumize the experimental system to exclude the interference of impurity gas on the experiment. If it is not the first experiment (because there is no impurity gas in the gas inlet system after the previous experiment), the gas inlet system does not need to be vacuumized. If it is the first experiment, open all valves of the gas inlet system except the pressure reducing valve 25 to vacuumize the gas inlet system at the same time. After the system pressure reaches the predetermined negative pressure value and remains for a period of time, the vacuumization is ended, and the water ring vacuum pump 13 and the exhaust valve 12 are closed.

[0050] 4. Adjust the pressure reducing valve 25 to adjust the system pressure in the upstream buffer tank 2 to the pressure designed in the experiment, open the valves through which the gas flows when the experiment is started, including the first gas inlet valve 24, the second gas inlet valve 25, the regulating valve 15 and the valve 7, and wait for the internal pressure of the entire system to stabilize, at which time the pressures measured by the pressure sensor 23, the upstream pressure gauge 16 and the downstream pressure gauge 8 are consistent, which is taken as the initial equilibrium pressure P0. Then the first gas inlet valve 24, the second gas inlet valve 25 and the regulating valve 15 are closed, and the valve 7 is kept open.

[0051] 5. Fine adjustment. Open the exhaust valve 10, adjust the fine adjustment valve 9, and reduce the gas pressure in the downstream reference tank 32, with the pulse being the gas pressure in the downstream reference tank 32 minus P0.

[0052] In order to ensure that the experimental results are not affected by the size of the pulse, the pressure difference is fixed at 0.2 MPa each time, and the exhaust valve 10 is closed after the required pressure difference is reached. Then the regulating valve 15 is opened, and the pressure difference can be monitored through the pressure difference sensor 14.

[0053] The pressures of the upstream reference tank 31 and the downstream reference tank 32 and the pressure difference between the two ends are recorded by the industrial computer 26. Under the action of the pressure gradient, seepage phenomenon occurs after the balance is broken, until the system re-balances, and then the data collection is stopped. Finally, the permeability can be calculated according to the experimental data, and relevant data reports can be generated for subsequent experimental data processing.

[0054] The above examples are only used to illustrate but not to limit the technical solutions of the present application. Although the present application is described in detail with reference to the above examples, it should be understood by those skilled in the art that the present application can still be modified or equivalently replaced without departing from the spirit and scope of the present application, and any modification or partial replacement should be covered in the scope of the claims of the present application.

Claims

1. A coal and rock permeability testing system based on the instantaneous pulse method, comprising an air intake system and an industrial control computer, wherein the air intake system is connected to an experimental system and is used to supply air to the experimental system; the experimental system is connected to an exhaust system, characterized in that: The exhaust system is used to discharge gases and fine-tune the pressure; the exhaust system is connected to a vacuum system, which is used to evacuate the experimental system before the experiment. The experimental system includes a coal sample holder, which is used to hold coal samples for experiments. The inlet of the coal sample holder is connected to the outlet of the air intake system, and the outlet of the coal sample holder is connected to the air intake of the exhaust system. The coal sample holder has an axial pressure interface and a confining pressure interface. The coal sample holder is connected to a first constant speed and constant pressure pump through the axial pressure interface, and the coal sample holder is connected to a second constant speed and constant pressure pump through the confining pressure interface. A regulating valve is connected between the inlet and outlet of the coal sample holder, and a differential pressure sensor is connected between the inlet and outlet of the regulating valve. The outlet of the coal sample holder is connected to a downstream reference tank through a downstream pipeline, and a downstream pressure gauge and a valve are installed on the downstream pipeline. The downstream pressure gauge, differential pressure sensor, first constant speed constant pressure pump and second constant speed constant pressure pump are all connected to the industrial control computer.

2. The coal and rock permeability testing system based on the instantaneous pulse method according to claim 1, characterized in that: The intake system includes a gas storage tank for storing high-pressure methane gas, a buffer tank connected to the gas storage tank, and a pressure reducing valve connected in series on the pipeline between the gas storage tank and the buffer tank; the buffer tank is connected in parallel to the main pipeline and the auxiliary pipeline. The auxiliary pipeline is connected to a standard chamber at its end. A first intake valve and a second intake valve are connected in series on the auxiliary pipeline. An upstream pipeline is connected to the auxiliary pipeline between the first intake valve and the second intake valve. The end of the main pipeline serves as the outlet of the intake system; a third intake valve and a fourth intake valve are connected in series on the main pipeline, and the upstream pipeline is connected to the main pipeline between the third intake valve and the fourth intake valve; a pressure sensor is connected to one end of the upstream pipeline and an upstream reference tank is connected to the other end; an upstream pressure gauge is installed on the main pipeline at the outlet of the intake system. Both the pressure sensor and the upstream pressure gauge are connected to the industrial control computer.

3. The coal and rock permeability testing system based on the instantaneous pulse method according to claim 2, characterized in that: The exhaust system includes an exhaust pipe, the upstream end of which is connected to both the outlet of the coal sample holder and the downstream end of the differential pressure sensor; the exhaust pipe is equipped with a gas flow meter and an exhaust valve, and a fine-tuning valve is installed on the exhaust pipe downstream of the exhaust valve.

4. The coal and rock permeability testing system based on the instantaneous pulse method according to claim 3, characterized in that: The vacuum system includes a water ring vacuum pump, the inlet pipe of which is connected to the exhaust pipe. The inlet pipe of the water ring vacuum pump is equipped with a suction valve and a negative pressure sensor. The gas flow meter and the negative pressure sensor are respectively connected to the industrial control computer.

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