Coal rock gas permeation direction testing system and testing method thereof

Abstract

The invention discloses a coal rock gas permeation direction test system and a test method thereof, and belongs to the technical field of determination of permeability and permeation directions of coal rock, shale and tight sandstone. The system comprises a gas source, a multidirectional gas permeability testing mechanism and a stress loading assembly, the gas source, the multidirectional gas permeability testing mechanism and the stress loading assembly are connected in series, and the multidirectional gas permeability testing mechanism comprises a plurality of unidirectional gas permeability testing parts which are connected in parallel. Coal samples and rock samples taken down from a coal block or a rock block from all directions are installed in a plurality of unidirectional gas permeability testing components in a one-to-one correspondence manner for permeability testing, so that the permeability of the coal samples or the rock samples in multiple directions can be simultaneously tested under the condition of the same gas source, and then the permeability of the coal samples or the rock samples in multiple directions can be tested according to permeability testing results in multiple directions. And inferring the permeation directions of the coal sample and rock sample reservoirs.

Description

Technical Field

[0001] The invention relates to a coal rock gas permeability direction testing system and a testing method thereof, belonging to the technical field of coal rock, shale, and dense sandstone permeability and permeability direction determination. Background Art

[0002] As conventional oil and gas resources are exhausted, humans have turned their attention to the development and utilization of deep unconventional clean energy such as coalbed methane, shale gas, and tight sandstone gas. Due to the deep burial depth of its reservoirs, complex geological structure, large ground stress, and low permeability, it is difficult to prevent and control gas, and the efficiency of coalbed methane extraction is low. Gas prevention and control and efficient extraction of unconventional clean energy such as coalbed methane, shale gas, and tight sandstone gas have become hot research topics in the energy field. It is very important to clarify the permeation mechanism and permeation direction of coalbed methane, shale gas, and tight sandstone gas in the reservoir for their efficient extraction. Therefore, understanding the reservoir permeability and the permeation direction of coalbed methane, shale gas, and tight sandstone gas in their reservoirs is of great significance to coal mine gas prevention and control and the extraction and utilization of coalbed methane, shale gas, and tight sandstone gas.

[0003] The Chinese patent document with the announcement number CN104713812A discloses a calibration method based on a core gas permeability measurement device, which includes using nitrogen to clear the air in the pipeline; collecting the cross-sectional area and length of the core to be measured, and clamping the core to be measured in a core holder; controlling the inlet pressure of the core holder by adjusting the gas permeability tester, collecting the pressure value and the core outlet flow rate; and fitting a functional relationship using the data of the core outlet flow rate and the square difference of the inlet and outlet stable pressures. Using this functional relationship, combined with Darcy's law, the corresponding inlet pressure and gas permeability under the limit pressure are calculated, and a relationship function between the gas permeability and the inverse of the average pressure is established. The horizontal intercept of the piecewise function is the Kershcherbazin permeability. The gas permeability calibration method of the present invention - the theoretical limit method, can quickly and accurately obtain the absolute permeability of the core.

[0004] However, the above permeability measurement is limited to a certain direction, while the gas seepage process in coal rock, shale, and tight sandstone has a certain directionality. In particular, under natural conditions, the internal material composition, material structure, pore fractures, and bedding distribution of coal rock and shale reservoirs are quite different, and these differences will affect their permeability and the direction of permeability expansion. In other words, the above device can only measure the permeability of coal samples and rock samples in one direction at a time, and cannot simultaneously measure the permeability of coal samples and rock samples in multiple directions under the same gas source conditions, and it is impossible to infer the permeability direction of coal samples and rock samples. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a coal rock gas permeability direction testing system and a testing method thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] A coal rock gas permeability directional testing system comprises a gas source, a multi-directional gas permeability testing mechanism and a stress loading component, wherein the gas source, the multi-directional gas permeability testing mechanism and the stress loading component are connected in series, and the multi-directional gas permeability testing mechanism comprises a plurality of unidirectional gas permeability testing components connected in parallel.

[0008] The gas source includes a gas cylinder and a pressure gauge A. The gas cylinder is connected to a gas supply pipe. One end of the gas supply pipe away from the gas cylinder is connected to a multi-directional gas permeability test mechanism. The pressure gauge A is installed on the gas supply pipe.

[0009] The multi-directional gas permeability testing mechanism includes six unidirectional gas permeability testing components connected in parallel.

[0010] The unidirectional gas permeability test component includes a triaxial core holder, an air inlet pipe is connected to the air inlet of the triaxial core holder, and one end of the air inlet pipe away from the triaxial core holder is connected to the gas source, and a ball valve A, a pressure reducing valve, a pressure gauge B, a ball valve B and an inlet pressure sensor are sequentially installed on the air inlet pipe, and the inlet pressure sensor is close to the triaxial core holder;

[0011] An outlet pipe is connected to the air outlet of the triaxial core holder, and one end of the air outlet pipe away from the triaxial core holder is connected to the outside world. An outlet pressure sensor, a dryer and a plurality of flow meters are sequentially installed on the air outlet pipe, and the outlet pressure sensor is close to the triaxial core holder.

[0012] The triaxial core holder is connected to a plurality of branch oil inlet pipes, and one end of all the branch oil inlet pipes away from the triaxial core holder is connected to the stress loading assembly through the same main oil pipe. A pressure sensor and a ball valve C are installed on the branch oil inlet pipes, and the pressure sensor is located between the ball valve C and the triaxial core holder;

[0013] A displacement sensor is provided on the three-axis core holder.

[0014] Three flow meters are installed on the air outlet pipe, the measuring ranges of the three flow meters decrease in sequence, and the flow meter with a large measuring range is close to the dryer.

[0015] The measuring ranges of the three flow meters are 5000 sccm, 200 sccm and 10 sccm respectively.

[0016] The multi-directional gas permeability testing mechanism also includes a gas pressure balance component, which is connected to all unidirectional gas permeability testing components.

[0017] The air pressure balance group includes a balance pipe, which is connected to the air inlet pipes in all unidirectional gas permeability test components, and the connection point between the balance pipe and the air inlet pipe is located between the pressure gauge B and the ball valve B. A ball valve D is installed on the balance pipe between two adjacent unidirectional gas permeability test components.

[0018] The stress loading component is a hand pump or a constant speed flow pump.

[0019] A test method for a coal-rock gas permeability direction test system comprises the following steps:

[0020] Step 1: According to the test needs, first go deep into the mine to select coal blocks and / or rocks and move them to the ground, then wrap them with plastic wrap and put them in plastic foam to fix them before transporting them to the laboratory;

[0021] Step 2: Mark the sampling positions from different directions on the coal block or / and rock block, then place the coal block or rock block on the sampling machine to drill coal samples or rock samples according to the marked directions, and record the names of the test coal samples or / and rock samples and the sampling direction information;

[0022] Step 3, placing multiple test pieces one by one into the triaxial core holders of multiple unidirectional gas permeability test components;

[0023] Step 4: According to the test plan, control the opening and closing of the ball valve C on each branch oil inlet pipe, and then use the stress loading assembly to slowly apply confining pressure and axial pressure to the test piece in the triaxial core holder until the pressure reaches the predetermined pressure and then stand still;

[0024] Step 5. After setting the gas injection pressure, open ball valve B, start the specimen permeability test, and record the readings on each flow meter;

[0025] Step 6: After the permeability test of the specimen is completed, the permeability direction of the coal block and / or rock block reservoir is inferred based on the permeability of the specimens in different orientations.

[0026] The beneficial effects of the present invention are:

[0027] 1. All unidirectional gas permeability test components are connected in parallel and then in series with the gas source, so that all unidirectional gas permeability test components are under the same gas source condition, and the coal samples and rock samples taken from the coal blocks or rock blocks in various directions are installed one by one in multiple unidirectional gas permeability test components for permeability testing, so that the permeability of the coal samples or rock samples in multiple directions can be tested simultaneously under the same gas source condition, and then the permeability direction of the coal sample and rock sample reservoir can be inferred based on the permeability test results in multiple directions.

[0028] 2. When all ball valves D are fully opened, the balance pipe connects all the air inlet pipes, which can keep the air inlet pressure of all triaxial core holders consistent, ensuring that the test pieces installed in all triaxial core holders are truly under the same gas source conditions; when all ball valves D are fully closed, the gas paths of each unidirectional gas permeability test component operate and work independently without interfering with each other; similarly, by controlling the opening and closing of ball valve D, the air inlet pressure of any adjacent triaxial core holders can be truly consistent, significantly improving the operational flexibility and practicality of the system.

[0029] 3. By controlling the opening and closing of ball valve A, it can be selected whether to pass gas into the corresponding unidirectional gas permeability test component. That is to say, the unidirectional gas permeability test component in the multi-directional gas permeability test mechanism can be partially ventilated and partially non-ventilated as needed, further improving the operational flexibility and practicality of the system.

[0030] 4. Some adjacent unidirectional gas permeability testing components in the multi-directional gas permeability testing mechanism can be used for permeability testing of coal samples in multiple directions under the same gas source conditions; the remaining adjacent unidirectional gas permeability testing components in the multi-directional gas permeability testing mechanism can be used for permeability testing of rock samples in multiple directions under the same gas source conditions, further improving the operational flexibility and practicality of the system.

[0031] 5. When the specimens are in the same position on the coal or rock block and the gas source conditions are the same during the permeability test, the ball valve C on each branch oil inlet pipe can be controlled to open and close, and the loading assembly can be used to apply different confining pressures and axial pressures to the specimens in the triaxial core holder to test the permeability of the specimens under different stress environments, further improving the practicality of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the present invention;

[0033] Figure 2 It is a structural schematic diagram of a unidirectional gas permeability testing component of the present invention;

[0034] Figure 3 It is a schematic diagram of obtaining coal samples and rock samples from different directions on a coal block or a rock block according to the present invention.

[0035] In the figure: 1-gas cylinder, 2-pressure gauge A, 3-multi-directional gas permeability test mechanism, 4-unidirectional gas permeability test component, 400-inlet pipe, 401-ball valve A, 402-pressure reducing valve, 403-pressure gauge B, 404-ball valve B, 405-inlet pressure sensor, 406-three-axis core holder, 407-displacement sensor, 408-outlet pressure sensor, 409-dryer, 410-flow meter, 411-outlet pipe, 412-main oil pipe, 413-branch oil inlet pipe, 414-ball valve C, 415-pressure sensor, 5-stress loading assembly, 6-balance pipe, 7-ball valve D. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0037] like Figure 1 and Figure 3 As shown, a coal-rock gas permeability direction testing system of the present invention comprises a gas source, a multi-directional gas permeability testing mechanism 3 and a stress loading component 5, wherein the gas source, the multi-directional gas permeability testing mechanism 3 and the stress loading component 5 are connected in series, and the multi-directional gas permeability testing mechanism 3 comprises a plurality of unidirectional gas permeability testing components 4 connected in parallel. When in use, all unidirectional gas permeability testing components 4 are connected in parallel and then in series with the gas source, so that all unidirectional gas permeability testing components 4 are placed under the same gas source condition, and the coal samples and rock samples taken from the coal block or rock block in all directions are correspondingly installed in the plurality of unidirectional gas permeability testing components 4 for permeability testing, so that the permeability of the coal sample or rock sample in multiple directions can be tested simultaneously under the same gas source condition, and then the permeability direction of the coal sample or rock sample reservoir can be inferred according to the permeability test results in multiple directions.

[0038] The gas source includes a gas cylinder 1 and a pressure gauge A2. The gas cylinder 1 is connected to a gas supply pipe, and one end of the gas supply pipe away from the gas cylinder 1 is connected to a multi-directional gas permeability test mechanism 3. The pressure gauge A2 is installed on the gas supply pipe. The pressure gauge A2 is used to detect the gas pressure of the gas supplied by the gas cylinder 1.

[0039] The multi-directional gas permeability testing mechanism 3 includes six unidirectional gas permeability testing components 4 connected in parallel.

[0040] The unidirectional gas permeability test component 4 includes a triaxial core holder 406, an air inlet pipe 400 is connected to the air inlet of the triaxial core holder 406, and one end of the air inlet pipe 400 away from the triaxial core holder 406 is connected to the gas source, and a ball valve A401, a pressure reducing valve 402, a pressure gauge B403, a ball valve B404 and an inlet pressure sensor 405 are sequentially installed on the air inlet pipe 400, and the inlet pressure sensor 405 is close to the triaxial core holder 406. When in use, one end of the air inlet pipe 400 away from the triaxial core holder 406 is connected to the air supply pipe. The ball valve A401 is used to control the on-off of the gas circuit of the unidirectional gas permeability testing component 4; the pressure reducing valve 402 is used to reduce the air pressure and keep its outlet pressure stable; the pressure gauge B403 is used to detect the outlet pressure of the pressure reducing valve 402; the ball valve B404 is used to control whether the gas is passed into the corresponding three-axis core clamp 406; the inlet pressure sensor 405 is used to detect the air inlet pressure of the three-axis core clamp 406.

[0041] The outlet of the triaxial core holder 406 is connected to an outlet pipe 411, and one end of the outlet pipe 411 away from the triaxial core holder 406 is connected to the outside, and an outlet pressure sensor 408, a dryer 409 and a plurality of flow meters 410 are sequentially installed on the outlet pipe 411, and the outlet pressure sensor 408 is close to the triaxial core holder 406. When in use, the outlet pressure sensor 408 is used to detect the outlet pressure of the triaxial core holder 406; the dryer 409 is used to dry the gas discharged from the triaxial core holder 406, so that the system can realize the permeability test of the test pieces with different water contents.

[0042] A plurality of branch oil inlet pipes 413 are connected to the triaxial core holder 406, and one end of all branch oil inlet pipes 413 away from the triaxial core holder 406 is connected to the stress loading assembly 5 through the same main oil pipe 412. A pressure sensor 415 and a ball valve C414 are installed on the branch oil inlet pipe 413, and the pressure sensor 415 is located between the ball valve C414 and the triaxial core holder 406. When in use, the pressure sensor 415 is used to detect the oil inlet pressure of the corresponding triaxial core holder 406; the ball valve C414 is used to control the on and off of the branch oil inlet pipe 413, and the ball valve C414 can be used to selectively control the plurality of branch oil inlet pipes 413 to adjust the axial pressure and confining pressure applied to the specimen by the triaxial core holder 406.

[0043] A displacement sensor 407 is provided on the triaxial core holder 406 .

[0044] Three flow meters 410 are installed on the air outlet pipe 411 . The measuring ranges of the three flow meters 410 decrease in sequence, and the flow meter 410 with a larger measuring range is close to the dryer 409 .

[0045] The three flow meters 410 have a range of 5000 sccm, 200 sccm and 10 sccm. The three flow meters 410 with a range of 5000 sccm, 200 sccm and 10 sccm are sequentially installed on the gas outlet pipe 411 to ensure the accuracy of gas flow detection and improve the accuracy of gas permeability test.

[0046] The multi-directional gas permeability testing mechanism 3 further includes a gas pressure balance component, which is connected to all the unidirectional gas permeability testing components 4 .

[0047] The gas pressure balance group includes a balance pipe 6, which is connected to the air inlet pipes 400 in all unidirectional gas permeability test components 4, and the connection point between the balance pipe 6 and the air inlet pipe 400 is located between the pressure gauge B403 and the ball valve B404. The ball valve D7 is installed on the balance pipe 6 between two adjacent unidirectional gas permeability test components 4. When all the ball valves D7 are opened, the balance pipe 6 connects all the air inlet pipes 400, so that the air inlet pressure of all the triaxial core holders 406 remains consistent, ensuring that the test pieces installed in all the triaxial core holders 406 are truly under the same gas source condition.

[0048] The stress loading component 5 is a hand pump or a constant speed flow pump.

[0049] A test method for a coal-rock gas permeability direction test system comprises the following steps:

[0050] Step 1: According to the test needs, first go deep into the mine to select coal blocks and / or rocks and move them to the ground, then wrap them with plastic wrap and put them in plastic foam to fix them before transporting them to the laboratory. When using, the size of coal blocks and rocks should be as large as possible, and the length, width and height should not be less than 300mm.

[0051] Step 2: Mark the positions for sampling from different directions on the coal block and / or rock block, then place the coal block and rock block on the sampler to drill coal samples and rock samples according to the marked directions, and record the name of the test coal sample and / or rock sample and the sampling direction information.

[0052] Step 3: Place multiple test pieces one by one into the three-axis core holders 406 of multiple unidirectional gas permeability test components 4.

[0053] Step 4: According to the test plan, the ball valve C414 on each branch oil inlet pipe 413 is controlled to be opened and closed, and then the stress loading assembly 5 is used to slowly apply confining pressure and axial pressure to the test piece in the triaxial core holder 406 until it is pressurized to a predetermined pressure and then left to stand. The ball valve C414 on each branch oil inlet pipe 413 is controlled to be opened and closed, and then the stress loading assembly 5 is used to apply confining pressure and axial pressure to the test piece in the triaxial core holder 406 to simulate the triaxial stress state in a real environment.

[0054] Step 5. After setting the gas injection pressure, open ball valve B404, start the specimen permeability test, and record the readings on each flow meter.

[0055] Step 6: After the permeability test of the specimen is completed, the permeability direction of the coal block or / and rock block reservoir is inferred based on the permeability of the specimens in different directions. Generally speaking, the direction of the coal block or rock block where the specimen with the highest permeability was originally located can be considered as the permeability direction of the coal block or rock block reservoir.

Claims

1. A coal rock gas permeability direction testing system, characterized by: The invention comprises an air source, a multi-directional air permeability test mechanism (3) and a stress loading component (5), wherein the air source, the multi-directional air permeability test mechanism (3) and the stress loading component (5) are connected in series, and the multi-directional air permeability test mechanism (3) comprises a plurality of unidirectional air permeability test components (4) connected in parallel.

2. The coal-rock gas permeability direction testing system according to claim 1, characterized in that: The gas source comprises a gas cylinder (1) and a pressure gauge A (2); the gas cylinder (1) is connected to a gas supply pipe, one end of the gas supply pipe away from the gas cylinder (1) is connected to a multi-directional gas permeability test mechanism (3), and the pressure gauge A (2) is installed on the gas supply pipe.

3. The coal-rock gas permeability direction testing system according to claim 1, characterized in that: The multi-directional gas permeability testing mechanism (3) comprises six unidirectional gas permeability testing components (4) connected in parallel.

4. The coal-rock gas permeability direction testing system according to claim 1, characterized in that: The unidirectional gas permeability test component (4) comprises a triaxial core holder (406), an air inlet pipe (400) is connected to the air inlet of the triaxial core holder (406), and one end of the air inlet pipe (400) away from the triaxial core holder (406) is connected to a gas source, and a ball valve A (401), a pressure reducing valve (402), a pressure gauge B (403), a ball valve B (404) and an inlet pressure sensor (405) are sequentially installed on the air inlet pipe (400), and the inlet pressure sensor (405) is close to the triaxial core holder (406); An outlet of the triaxial core holder (406) is connected to an outlet pipe (411), and one end of the outlet pipe (411) away from the triaxial core holder (406) is connected to the outside, an outlet pressure sensor (408), a dryer (409) and a plurality of flow meters (410) are sequentially installed on the outlet pipe (411), and the outlet pressure sensor (408) is close to the triaxial core holder (406); A plurality of branch oil inlet pipes (413) are connected to the triaxial core holder (406); the ends of all the branch oil inlet pipes (413) away from the triaxial core holder (406) are connected to the stress loading assembly (5) through the same main oil pipe (412); a pressure sensor (415) and a ball valve C (414) are installed on the branch oil inlet pipes (413), and the pressure sensor (415) is located between the ball valve C (414) and the triaxial core holder (406); A displacement sensor (407) is provided on the triaxial core holder (406).

5. The coal-rock gas permeability direction testing system according to claim 4, characterized in that: Three flow meters (410) are installed on the air outlet pipe (411), and the measuring ranges of the three flow meters (410) decrease in sequence, and the flow meter (410) with a large measuring range is close to the dryer (409).

6. The coal-rock gas permeability direction testing system according to claim 5, characterized in that: The measuring ranges of the three flow meters (410) are 5000 sccm, 200 sccm and 10 sccm respectively.

7. The coal-rock gas permeability direction testing system according to claim 4, characterized in that: The multi-directional gas permeability testing mechanism (3) further comprises a gas pressure balance component, which is connected to all the unidirectional gas permeability testing components (4).

8. The coal-rock gas permeability direction testing system according to claim 7, characterized in that: The gas pressure balance group comprises a balance pipe (6), the balance pipe (6) is connected to the air inlet pipes (400) in all the unidirectional gas permeability test components (4), and the connection point between the balance pipe (6) and the air inlet pipe (400) is located between the pressure gauge B (403) and the ball valve B (404), and a ball valve D (7) is installed on the balance pipe (6) between two adjacent unidirectional gas permeability test components (4).

9. The coal-rock gas permeability direction testing system according to claim 1, characterized in that: The stress loading component (5) is a hand pump or a constant speed flow pump.

10. A test method for a coal-rock gas permeability direction test system according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: According to the test needs, first go deep into the mine to select coal blocks and / or rocks and move them to the ground, then wrap them with plastic wrap and put them in plastic foam to fix them before transporting them to the laboratory; Step 2: Mark the sampling positions from different directions on the coal block or / and rock block, then place the coal block or rock block on the sampling machine to drill coal samples or rock samples according to the marked directions, and record the names of the test coal samples or / and rock samples and the sampling direction information; Step 3: placing the multiple test pieces one by one into the three-axis core holders (406) of the multiple unidirectional gas permeability test components (4); Step 4: According to the test plan, the ball valve C (414) on each branch oil inlet pipe (413) is controlled to be opened and closed, and then the stress loading assembly (5) is used to slowly apply confining pressure and axial pressure to the test piece in the triaxial core holder (406) until the pressure reaches a predetermined pressure and then the test piece is allowed to stand; Step 5: After setting the gas injection pressure, open ball valve B (404), start the specimen permeability test, and record the readings on each flow meter; Step 6: After the permeability test of the specimen is completed, the permeability direction of the coal block and / or rock block reservoir is inferred based on the permeability of the specimens in different orientations.

Images