阅读说明：本技术 一种煤层气-致密气合采储层干扰机理的模拟系统及方法 (Simulation system and method for interference mechanism of coal bed gas-dense gas combined production reservoir ) 是由 张健 吴建光 吴翔 孙晗森 林亮 杨宇光 卓仁燕 朱苏阳 彭小龙 王超文 于 2019-09-24 设计创作，主要内容包括：本发明公开了一种煤层气-致密气合采储层干扰机理的模拟系统及方法,包括吸附气模拟系统、致密气模拟系统、煤层水饱和系统、临界解吸模拟系统、井筒排采模拟及气液流速测量系统,所述吸附气模拟系统的右端连接临界解吸模拟系统的左端下部,所述致密气模拟系统的一端连接吸附气模拟系统,另一端连接临界解吸模拟系统的左端上部,所述临界解吸模拟系统的右端连接井筒排采模拟及气液流速测量系统,所述煤层水饱和系统连接临界解吸模拟系统的下端；本发明针对煤层气-致密气合采储层干扰特点,测试煤层气-致密气合采储层干扰及气-液流动特征,测试过程科学,结果准确,为煤层气与致密气等非常规气藏合采的有效开发创造了良好的条件。(The invention discloses a simulation system and a method for a coal bed gas-dense gas combined mining reservoir interference mechanism, which comprises an adsorbed gas simulation system, a dense gas simulation system, a coal bed water saturation system, a critical desorption simulation system, a shaft drainage simulation and gas-liquid flow rate measurement system, wherein the right end of the adsorbed gas simulation system is connected with the lower part of the left end of the critical desorption simulation system; the method aims at the interference characteristics of the coalbed methane-dense gas commingled production reservoir, tests the coalbed methane-dense gas commingled production reservoir interference and the gas-liquid flow characteristics, has scientific test process and accurate result, and creates good conditions for the effective development of unconventional gas reservoir commingled production of coalbed methane, dense gas and the like.)

1. A simulation system of interference mechanism of a coal bed gas-dense gas co-production reservoir is characterized by comprising the following components: the system comprises an adsorbed gas simulation system, a dense gas simulation system, a coal bed water saturation system, a critical desorption simulation system, a shaft drainage and production simulation and gas-liquid flow rate measurement system, wherein the right end of the adsorbed gas simulation system is connected with the lower part of the left end of the critical desorption simulation system through a pipeline;

the critical desorption simulation system comprises a second needle valve (22) and a sand filling box (6), wherein the outlet end of the second needle valve (22) is connected with the lower part of the left end face of the sand filling box (6) through a pipeline and extends into the sand filling box (6), and starting differential pressure check valves (5) are arranged in the pipeline in the sand filling box (6) in a radial and side-by-side mode.

2. The system for simulating the interference mechanism of the coalbed methane-dense gas co-production reservoir as claimed in claim 1, wherein the adsorbed gas simulation system comprises a high-pressure gas cylinder (1) and a first intermediate container (41), the high-pressure gas cylinder (1) is connected with the inlet end of the first intermediate container (41) through a pipeline, and a first needle valve (21) and a first pressure gauge (31) are arranged on the pipeline connecting the high-pressure gas cylinder (1) and the first intermediate container (41).

3. The system for simulating the interference mechanism of the coal bed methane-tight gas co-production reservoir as claimed in claim 1, wherein the coal bed water saturation system comprises a water tank (13) and a second constant-speed pump (82), the inlet end of the second constant-speed pump (82) is connected with the water tank (13) through a pipeline, the outlet end of the second constant-speed pump is connected with the lower end of the sand filling box (6) through a pipeline, and a second pressure gauge (32) and a third needle valve (23) are arranged on the pipeline connecting the second constant-speed pump (82) and the sand filling box (6).

4. The system for simulating the interference mechanism of the coal bed methane-dense gas co-production reservoir is characterized by comprising a sealed transparent barrel (10), a first constant-speed pump (81), a measuring cylinder (9) and a gas recovery device (12), wherein the upper part and the lower part of the sealed transparent barrel (10) are respectively connected with the upper part and the lower part of the right end face of a sand filling box (6) through pipelines and are communicated with the inside of the sand filling box (6), the inlet end of the first constant-speed pump (81) is connected with the bottom end of the sealed transparent barrel (10) through a pipeline, and the outlet end of the first constant-speed pump is connected with the measuring cylinder (9); the upper end of the sealed transparent barrel (10) is connected with the gas recovery device (12) through a pipeline, and a third pressure gauge (33) and a gas flowmeter (11) are arranged on the pipeline connecting the sealed transparent barrel (10) and the gas recovery device (12).

5. The system for simulating the interference mechanism of the coalbed methane-dense gas co-production reservoir as claimed in claim 4, wherein the joints of the upper part and the lower part of the sand filling box (6) and the pipeline are respectively provided with a second sand control net (72) and a first sand control net (71).

6. The system for simulating the interference mechanism of the coal bed methane-dense gas co-production reservoir as claimed in claim 1, wherein the dense gas simulation system comprises a second intermediate container (42), the inlet end of the second intermediate container (42) is connected with the high-pressure gas cylinder (1) through a pipeline, the outlet end of the second intermediate container is connected with the upper part of the left end face of the sand filling box (6) through a pipeline and communicated with the inside of the sand filling box (6), a fourth needle valve (24) is arranged on the pipeline of the second intermediate container (42) connected with the sand filling box (6), and a fourth pressure gauge (34) and a fifth needle valve (25) are arranged on the pipeline connected with the high-pressure gas cylinder (1).

7. The method for simulating the interference mechanism of the coalbed methane-dense gas commingled production reservoir in the claim 1 is characterized by comprising the following steps of:

s1, sand filling and saturated water process: filling fine sand, coarse sand and fine sand into a sand filling box (6) in sequence, and stopping saturated water when the water in the sand filling box (6) is saturated through a coal bed water saturation system until the water in a sealed transparent barrel (10) does not overflow;

s2, an adsorbed gas simulation process: filling gas into the first intermediate container (41) through a high-pressure gas bottle (1);

s3, dense gas filling process: gas is filled into the second intermediate container (42) through the high-pressure gas bottle (1), and the second intermediate container (42) is filled with the gas into the sand filling box (6), so that water in fine sand at the upper part in the sand filling box (6) is discharged through the sealed transparent barrel (10);

s4, well bore extraction process: slowly pumping out water in the sealed transparent barrel (10) through a first constant speed pump (81);

s5, critical desorption and gas-liquid measurement process: the amount of water slowly pumped by the first constant speed pump (81) is continuously measured, after the gas is produced, the gas pressure in the sealed transparent barrel (10) is measured by the third pressure gauge (33), and the gas flow is measured by the gas flow meter (11).

8. The method for simulating the disturbance mechanism of the coalbed methane-dense gas commingled production reservoir of claim 7, wherein in step S1, the fine sand has a mesh size of 320 meshes and a weight of 200Kg, the coarse sand has a mesh size of 80 meshes and a weight of 150Kg, and 100Kg of the fine sand, 150Kg of the coarse sand and 100Kg of the fine sand are sequentially filled into the sand filling box (6).

9. The method for simulating the interference mechanism of the coalbed methane-tight gas co-production reservoir as claimed in claim 7, wherein in step S2, when the pressure in the first intermediate container (41) is 0.12MPa, the gas filling is stopped; in step S3, when the pressure in the second intermediate container (42) is 0.118MPa, the inflation is stopped.

10. The method for simulating the disturbance mechanism of the coalbed methane-tight gas co-production reservoir according to claim 7, wherein in the step S4, the pumping speed of the first constant speed pump (81) is 9.6 ml/min.

Technical Field

The invention relates to the technical field of development of coal bed methane reservoirs, in particular to a system and a method for simulating an interference mechanism of a coal bed methane-dense gas co-production reservoir.

Background

The coal bed gas is hydrocarbon gas which is stored in a coal bed, takes methane as a main component, is adsorbed on the surface of coal matrix particles as a main component, is partially dissociated in coal pores or dissolved in coal bed water, is an associated mineral resource of coal, belongs to unconventional natural gas, and is a clean and high-quality energy and chemical raw material which is grown internationally in nearly twenty years.

The dense gas is sandstone formation natural gas with the permeability of less than 0.1 millidarcy, has become one of important fields of global unconventional natural gas exploration and development, and has great strategic significance for the development of natural gas industry and social operation in China by accelerating the development and utilization of unconventional natural gas resources such as the dense gas.

Due to the huge geological reserves, the effective development of unconventional natural gas such as coal bed gas, dense gas and the like can improve the energy structure of China and supplement the defects of the distribution and supply of the conventional natural gas in China. Different from the conventional natural gas reservoir, the coal bed gas and the dense gas generally grow in a symbiotic manner, taking the east edge of the Ordos basin as an example, the exploitation yield of a single gas reservoir is low, no economic benefit exists, and the yield and the economic benefit of a gas well can be improved by the combined exploitation of the coal bed gas and the dense gas. In the combined mining process, the escape of the coal bed gas can interfere with the compact gas reservoir and the combined mining. Therefore, the interference process of the coalbed methane-dense gas commingled production reservoir is a key problem for carrying out unconventional gas reservoir commingled production development and design. At present, scholars at home and abroad research on interference of a coal bed gas-dense gas co-production reservoir stratum do a lot of work, derive an escape model of the coal bed gas and speculate co-production interference dynamics. However, the reservoir interference phenomenon in the coalbed methane-dense gas combined production process is essentially the coupling mass transfer problem of a multiphase fluid in porous media at different layers, and the reservoir interference characteristic is difficult to directly obtain through theoretical research. At present, the physical simulation research of coalbed methane-dense gas co-production still stays in the theoretical aspect, and no system and method capable of carrying out physical simulation on the interference process of the coalbed methane-dense gas co-production reservoir are available.

Disclosure of Invention

Aiming at the problems, the invention provides a system and a method for simulating the interference mechanism of a coalbed methane-dense gas co-production reservoir, which are suitable for researching the mechanism of the coalbed methane-dense gas co-production reservoir and the influence of the reservoir interference on gas-water two-phase flow.

The invention adopts the following technical scheme:

a simulation system of interference mechanism of a coal bed gas-dense gas co-production reservoir comprises: the system comprises an adsorbed gas simulation system, a dense gas simulation system, a coal bed water saturation system, a critical desorption simulation system, a shaft drainage and production simulation and gas-liquid flow rate measurement system, wherein the right end of the adsorbed gas simulation system is connected with the lower part of the left end of the critical desorption simulation system through a pipeline;

the critical desorption simulation system comprises a second needle valve and a sand filling box, wherein the outlet end of the second needle valve is connected with the lower part of the left end face of the sand filling box through a pipeline and extends into the sand filling box, and the pipeline in the sand filling box is provided with starting pressure difference one-way valves in parallel in the radial direction.

Preferably, the adsorbed gas simulation system comprises a high-pressure gas cylinder and a first intermediate container, the high-pressure gas cylinder is connected with the inlet end of the first intermediate container through a pipeline, and a first needle valve and a first pressure gauge are arranged on the pipeline connecting the high-pressure gas cylinder and the first intermediate container.

Preferably, the coal seam water saturation system comprises a water tank and a second constant-speed pump, wherein the inlet end of the second constant-speed pump is connected with the water tank through a pipeline, the outlet end of the second constant-speed pump is connected with the lower end of the sand filling box through a pipeline, and a second pressure gauge and a third needle valve are arranged on the pipeline connecting the second constant-speed pump and the sand filling box.

Preferably, the shaft drainage and production simulation and gas-liquid flow rate measurement system comprises a sealed transparent barrel, a first constant-speed pump, a measuring cylinder and a gas recovery device, wherein the upper part and the lower part of the sealed transparent barrel are respectively connected with the upper part and the lower part of the right end surface of a sand filling box through pipelines and are communicated with the inside of the sand filling box, the inlet end of the first constant-speed pump is connected with the bottom end of the sealed transparent barrel through a pipeline, and the outlet end of the first constant-speed pump is connected with the measuring cylinder; the upper end of the sealed transparent barrel is connected with a gas recovery device through a pipeline, and a third pressure gauge and a gas flowmeter are arranged on the pipeline connecting the sealed transparent barrel and the gas recovery device.

Preferably, the joints of the upper part and the lower part of the sand filling box and the pipeline are respectively provided with a second sand control net and a first sand control net.

Preferably, the dense gas simulation system comprises a second intermediate container, an inlet end of the second intermediate container is connected with the high-pressure gas cylinder through a pipeline, an outlet end of the second intermediate container is connected with the upper part of the left end face of the sand filling box through a pipeline and communicated with the inside of the sand filling box, a fourth needle valve is arranged on the pipeline of the second intermediate container connected with the sand filling box, and a fourth pressure gauge and a fifth needle valve are arranged on the pipeline connected with the high-pressure gas cylinder.

A method of a simulation system utilizing a coal bed gas-dense gas co-production reservoir interference mechanism comprises the following steps:

s1, sand filling and saturated water process: filling fine sand, coarse sand and fine sand into a sand filling box in sequence, and stopping saturated water in the sand filling box through a coal bed water saturation system until the water in the sealed transparent barrel (10) does not overflow;

s2, an adsorbed gas simulation process: filling gas into the first intermediate container through a high-pressure gas cylinder;

s3, dense gas filling process: filling gas into the second intermediate container through the high-pressure gas cylinder, and filling gas into the sand filling box through the second intermediate container, so that water in fine sand at the upper part in the sand filling box is discharged through the sealed transparent barrel;

s4, well bore extraction process: slowly pumping out water in the sealed transparent barrel through a first constant-speed pump;

s5, critical desorption and gas-liquid measurement process: constantly measure the water yield of slowly taking out through first constant speed pump, after gaseous output, measure the gas pressure in the sealed transparent bucket through the third pressure gauge, measure gas flow through gas flowmeter.

Preferably, in step S1, the fine sand having a mesh size of 320 mesh and a weight of 200Kg and the coarse sand having a mesh size of 80 mesh and a weight of 150Kg is filled into the filling box in the order of 100Kg of fine sand, 150Kg of coarse sand and 100Kg of fine sand.

Preferably, in step S2, when the pressure in the first intermediate container is 0.12MPa, the aeration is stopped; in step S3, when the pressure in the first intermediate container is 0.118MPa, the inflation is stopped.

Preferably, in step S4, the first constant-speed pumping water rate is 9.6 ml/min.

The invention has the beneficial effects that:

the method can test the interference and gas-liquid flow characteristics of the coalbed methane-dense gas co-production reservoir aiming at the interference characteristics of the coalbed methane-dense gas co-production reservoir, has scientific test process and accurate test result, and creates good conditions for the effective development of the co-production of unconventional gas reservoirs such as the coalbed methane, the dense gas and the like.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below, and it is apparent that the drawings in the following description only relate to some embodiments of the present invention and are not limiting on the present invention.

FIG. 1 is a schematic diagram of the system of the present invention;

FIG. 2 is a graph showing the reading of the pressure gauge of the present invention;

FIG. 3 is a schematic diagram of a gas-water flow curve according to the present invention;

shown in the figure:

1-a high-pressure gas cylinder, 21-a first needle valve, 22-a second needle valve, 23-a third needle valve, 24-a fourth needle valve, 25-a fifth needle valve, 31-a first pressure gauge, 32-a second pressure gauge, 33-a third pressure gauge, 34-a fourth pressure gauge, 41-a first intermediate container, 42-a second intermediate container, 5-a starting pressure difference one-way valve, 6-a sand filling box, 71-a first sand control net, 72-a second sand control net, 81-a first constant speed pump, 82-a second constant speed pump, 9-a measuring cylinder, 10-a sealed transparent barrel, 11-a gas flowmeter, 12-a gas recovery device, and 13-a water tank.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of the word "comprising" or "comprises", and the like, in this disclosure is intended to mean that the elements or items listed before that word, include the elements or items listed after that word, and their equivalents, without excluding other elements or items. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

The invention is further illustrated with reference to the following figures and examples.

As shown in fig. 1 to 3, a physical simulation system and method for critical desorption of coal bed gas includes

A simulation system of interference mechanism of a coal bed gas-dense gas co-production reservoir comprises: the system comprises an adsorbed gas simulation system, a dense gas simulation system, a coal bed water saturation system, a critical desorption simulation system, a shaft drainage and production simulation and gas-liquid flow rate measurement system, wherein the right end of the adsorbed gas simulation system is connected with the lower part of the left end of the critical desorption simulation system through a pipeline;

the adsorption gas simulation system comprises a high-pressure gas bottle 1 and a first intermediate container 41, wherein the high-pressure gas bottle 1 is connected with the inlet end of the first intermediate container 41 through a pipeline, and a first needle valve 21 and a first pressure gauge 31 are arranged on the pipeline connecting the high-pressure gas bottle 1 and the first intermediate container (41);

the high-pressure gas bottle 1 provides gas with a certain pressure for the system, the gas in the high-pressure gas bottle 1 is introduced into the first intermediate container 41, the adsorption gas amount can be simulated, the volume of the first intermediate container 41 is 15L, the pressure can be supported by 3.6MPa, the gas in the first intermediate container 41 can be sealed through the first needle valve 21, and the pressure change in the first intermediate container 41 can be measured through the first pressure gauge 31.

The coal seam water saturation system comprises a water tank 13 and a second constant-speed pump 82, the inlet end of the second constant-speed pump 82 is connected with the water tank 13 through a pipeline, the outlet end of the second constant-speed pump 82 is connected with the lower end of a sand filling box 6 through a pipeline, and a second pressure gauge 32 and a third needle valve 23 are arranged on the pipeline connecting the second constant-speed pump 82 and the sand filling box 6;

pumping the water in the water tank 12 into the sand filling box 6 through a second constant speed pump 82, and stopping saturated water when the water in the sealed transparent barrel (10) does not overflow after the water completely submerges the sand; the final pressure of the saturated water process and the initial pressure in the sand-filling box 6 at the start of the experiment can be measured by the second pressure gauge 32, and the water supply in the sand-filling box 6 can be closed by closing the third needle valve 23.

The dense gas simulation system comprises a second intermediate container 42, the inlet end of the second intermediate container 42 is connected with the high-pressure gas cylinder 1 through a pipeline, the outlet end of the second intermediate container 42 is connected with the upper part of the left end surface of the sand filling box 6 through a pipeline and is communicated with the interior of the sand filling box 6, a fourth needle valve 24 is arranged on the pipeline of the second intermediate container 42 connected with the sand filling box 6, and a fourth pressure gauge 34 and a fifth needle valve 25 are arranged on the pipeline connected with the high-pressure gas cylinder 1;

the gas in the high-pressure gas cylinder 1 is introduced into a second intermediate container 42 through a fifth needle valve 25, the volume of the second intermediate container 42 is 15L and can bear 3.6MPa, the second intermediate container is used for simulating the storage amount of the dense gas, a fourth pressure gauge 34 is used for measuring the real-time change of the pressure in the second intermediate container 42, and a fourth needle valve 24 can communicate the second intermediate container 42 with a sand filling box 6 and is used for simulating the gas supply of the dense gas.

The shaft drainage and production simulation and gas-liquid flow rate measurement system comprises a sealed transparent barrel 10, a first constant-speed pump 81, a measuring cylinder 9 and a gas recovery device 12, wherein the upper part and the lower part of the sealed transparent barrel 10 are respectively connected with the upper part and the lower part of the right end face of a sand filling box 6 through pipelines and are communicated with the inside of the sand filling box 6, the inlet end of the first constant-speed pump 81 is connected with the bottom end of the sealed transparent barrel 10 through a pipeline, and the outlet end of the first constant-speed pump is connected with the measuring cylinder 9; the upper end of the sealed transparent barrel 10 is connected with a gas recovery device 12 through a pipeline, and a third pressure gauge 33 and a gas flowmeter 11 are arranged on the pipeline connecting the sealed transparent barrel 10 and the gas recovery device 12; the joints of the upper part and the lower part of the sand filling box 6 and the pipeline are respectively provided with a second sand control net 72 and a first sand control net 71;

the first sand control net 71 is used for preventing fine sand of a simulated coal bed from entering a pipeline, the second sand control net 72 is used for preventing fine sand of a simulated dense gas reservoir from entering the pipeline, water in the sealed transparent barrel 10 is discharged through the first constant speed pump 81, the diameter of the sealed transparent barrel 10 is 127mm, the wall thickness is 10mm, the height is 3500mm, the discharged water amount is measured through the measuring cylinder 9, when the system starts to produce gas, the pressure in the sealed transparent barrel 10 can be measured through the third pressure gauge 33, the gas flow is measured through the gas flowmeter 11, and the discharged gas is recovered through the gas recovery device 12.

The critical desorption simulation system comprises a second needle valve 22 and a sand filling box 6, wherein the outlet end of the second needle valve 22 is connected with the lower part of the left end face of the sand filling box 6 through a pipeline and extends into the sand filling box 6, the pipeline in the sand filling box 6 is provided with starting differential pressure one-way valves 5 in a radial direction side by side mode, the number of the starting differential pressure one-way valves is at least 6, but not limited to 6, the starting differential pressure of the one-way valves is 0.1Bar, and when the differential pressure at the two ends of the valves is larger than 0.1Bar, the valves allow fluid to pass through in a one-way mode.

The second needle valve 22 is used for controlling the communication degree between the first intermediate container 41 and the starting pressure difference single-phase valve 5, the size of the sand filling box 6 is 300mm multiplied by 900mm multiplied by 1000mm, the sand filling box 6 is filled with sand to simulate the seepage environment of porous media, fine sand at the bottom and the top respectively simulate the seepage environment of coal and dense gas, coarse sand at the middle simulates the seepage environment for interference dissipation, the starting pressure difference single-phase valve 5 is arranged in the middle of the sand filling box 6 and is connected with the second needle valve 22 through a pressure-resistant pipeline, the starting pressure difference single-phase valve 5 can allow fluid to flow in a single direction under the pressure difference condition of 0.1Bar, when the water pressure in the sand filling box 6 is reduced, the difference between the water pressure and the gas pressure in the first intermediate container 41 reaches a threshold value, the starting pressure difference single-phase valve 5 is opened, and gas flows into the sand filling box 6 from the first intermediate container 41, so that the critical desorption process is simulated.

A method of a simulation system utilizing a coal bed gas-dense gas co-production reservoir interference mechanism comprises the following steps:

s1, sand filling and saturated water process:

1. 200kg of 320-mesh fine sand and 150kg of 80-mesh coarse sand are sieved, sand grains are wetted by distilled water in advance, and the fine sand 100kg, the coarse sand 150kg and the fine sand 100kg are filled into a filling box 6 in sequence,

2. Opening the second constant-speed pump 82, introducing the water in the water tank 13 into the sand filling box 6 to saturate the sand filling box 6, and stopping the saturated water when the water is continuously added to the pressure of the water phase after the water completely submerges the sand so that the water in the sealed transparent barrel 7 does not overflow;

s2, an adsorbed gas simulation process:

1. the second needle valve 22 was closed, the first needle valve 21 was opened, and a certain amount of gas was charged into the first intermediate tank 41 through the high-pressure gas cylinder 1, so that the pressure in the first intermediate tank 41 was 0.12 MPa.

2. The first needle valve 21 is closed and the pressure change in the first intermediate container 4 is measured in real time by the first pressure gauge 31.

S3, dense gas filling process:

1. the fifth needle valve 25 and the fourth needle valve 24 were opened, and a certain amount of gas was charged into the second intermediate container 42 and the flask 6 through the high-pressure gas cylinder 1, so that the pressure in the second intermediate container 42 was 0.118 MPa.

2. And (3) removing the water on the upper layer in the sand filling box 6 by using the sealed transparent barrel 10 to complete the filling of the dense gas.

3. The fourth needle valve 24 and the fifth needle valve 25 are closed, and the pressure change in the second intermediate container 42 is measured by the fourth pressure gauge 34.

S4, well bore extraction process:

1. slowly pumping water in the sealed transparent barrel 7 by a first constant speed pump 81, wherein the pumping speed is 9.6 ml/min;

2. opening the fourth needle valve 24 to simulate the dense gas to generate gas, and measuring the real-time pressure in the second intermediate container 42 through the fourth pressure gauge 34;

s5, critical desorption and gas-liquid measurement process:

1. the amount of water pumped by the first constant speed pump 81 is measured in real time by the measuring cylinder 9;

2. the gas pressure in the sealed transparent tub 10 is measured by the third gas pressure 33, and the gas flow rate is measured by the gas flow meter 11.

3. The gas in the experiment was recovered by the gas recovery device 12.

The test results are shown in fig. 2 to 3, in which the curves of fig. 2 are the pressure changes measured by the first pressure gauge 31, the second pressure gauge 32, the third pressure gauge 33, and the fourth pressure gauge 34, and fig. 3 is a graph showing the water discharge dynamics obtained by the measuring cylinder 9 and the gas generation dynamics obtained by the gas flowmeter 11.

In fig. 2, the value of the first pressure gauge 31 is kept constant and then is decreased, which indicates that the coal seam does not produce gas at the beginning of the experiment, and the coal seam begins to produce gas after the pressure is reduced to a certain degree; the value of the second pressure gauge 32 decreases indicating a continuous decrease in reservoir pressure; the value of the third pressure gauge 33 is reduced all the time, which indicates that the production of the coal bed gas has little influence on the casing pressure; the pressure measured by the fourth pressure gauge 34 is constantly decreasing, indicating that the simulated tight gas formation is being produced, and that the pressure dynamics are consistent with the pressure dynamics obtained on site. The gas production in figure 3 begins to decrease, indicating the production dynamics of the dense gas, and then increases, indicating the problem of output interference after the gas production of the coal bed gas, and the water production is reduced in a step shape and keeps the same with the field dynamics. The yield data simulation result is consistent with the coalbed methane-dense gas combined mining numerical simulation result, and the experimental device can better model-fit the mining process.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.