阅读说明：本技术 一种煤层气临界解吸的物理模拟系统及方法 (Physical simulation system and method for coal bed gas critical desorption ) 是由 杨宇光 吴翔 吴建光 张健 孙晗森 林亮 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临界解吸的物理模拟系统及方法,包括吸附气模拟系统、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通过管线连接临界解吸模拟系统的左端,临界解吸模拟系统的右端通过管线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通过管线连接临界解吸模拟系统的下端；本发明同时公开了采用该系统对煤层气临界解吸特征进行试验的方法。本发明针对煤层气的临界解吸特点,测试煤层气的临界解吸中气-液流动特征,测试过程科学,测试结果准确,为煤层气的有效开发创造了良好的条件。(The invention discloses a physical simulation system and a physical simulation method for coal bed gas critical desorption, which comprise an adsorbed 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 left end of the critical desorption simulation system through a pipeline, the right end of the critical desorption simulation system is connected with the shaft drainage and production simulation and gas-liquid flow rate measurement system through a pipeline, and the coal bed water saturation system is connected with the lower end of the critical desorption simulation system through a pipeline; the invention also discloses a method for testing the coal bed gas critical desorption characteristics by adopting the system. The method provided by the invention is used for testing the gas-liquid flow characteristics in the critical desorption of the coal bed gas aiming at the critical desorption characteristics of the coal bed gas, the testing process is scientific, the testing result is accurate, and good conditions are created for the effective development of the coal bed gas.)

1. A physical simulation system for coal bed gas critical desorption, comprising: the system comprises an adsorbed 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 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 sand filling box (6) through a pipeline and extends into the sand filling box (6), and starting pressure difference check valves (5) are arranged in the pipeline in the sand filling box (6) in a radial direction in parallel.

2. The physical simulation system for critical desorption of coal bed gas according to claim 1, wherein the adsorbed gas simulation system comprises a high-pressure gas cylinder (1) and an intermediate container (4), the high-pressure gas cylinder (1) is connected with the inlet end of the intermediate container (4) 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 intermediate container (4).

3. The physical simulation system for critical desorption of coal bed gas according to claim 1, wherein the coal bed water saturation system comprises a water tank (12) and a second constant-speed pump (82), the inlet end of the second constant-speed pump (82) is connected with the water tank (12) 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 of the second constant-speed pump (82) and the sand filling box (6).

4. The physical simulation system for coal bed methane critical desorption, which is characterized in that the shaft drainage simulation and gas-liquid flow rate measurement system comprises a sealed transparent barrel (7), a first constant-speed pump (81), a measuring cylinder (9) and a gas recovery device (11), wherein the inlet end of the first constant-speed pump (81) is connected with the bottom end of the sealed transparent barrel (7) 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 (7) is connected with the gas recovery device (11) through a pipeline, and a third pressure gauge (33) and a gas flowmeter (10) are arranged on the pipeline connecting the sealed transparent barrel (7) and the gas recovery device (11).

5. The physical simulation system for critical desorption of coal bed methane according to claim 1, wherein the number of the start pressure difference one-way valves (5) is at least 6, the start pressure difference is 0.1Bar, and when the pressure difference between two ends of the start pressure difference one-way valves (5) is larger than 0.1Bar, the fluid is allowed to pass through in one way.

6. A method of using the physical simulation system for coal bed methane critical desorption of claim 1, comprising the steps of:

s1, sand filling and saturated water process: filling sand into a sand filling box (6), and filling saturated water in the sand filling box (6) through a coal bed water saturation system until the water in the sealed transparent barrel (7) does not overflow, and stopping the saturated water;

s2, an adsorbed gas simulation process: gas is filled into the intermediate container (4) through the high-pressure gas bottle (1);

s3, well bore extraction process: slowly pumping out water in the sealed transparent barrel (7) through a first constant speed pump (81);

s4, critical desorption and gas-liquid measurement process: the amount of water slowly pumped out by the first constant speed pump (81) is continuously measured, after the gas is produced, the gas pressure in the sealed transparent barrel (7) is measured by the third pressure gauge (33), and the gas flow is measured by the gas flow meter (10).

7. The method according to claim 6, wherein in step S1, the sand has a mesh size of 50 mesh and a weight of 200 Kg.

8. The physical simulation method for critical desorption of coalbed methane according to claim 6, wherein in step S2, when the pressure in the intermediate container (4) is 0.12MPa, the aeration is stopped.

9. The physical simulation method for critical desorption of coalbed methane according to claim 6, wherein in the step S3, the pumping speed of the first constant speed pump (81) is 5.3 ml/min.

Technical Field

The invention relates to the technical field of development of coal bed gas reservoirs, in particular to a physical simulation system and method for coal bed gas critical desorption.

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.

Due to the huge geological reserves, the effective development of the coal bed gas can improve the energy structure of China and supplement the defects of the distribution and supply of the conventional natural gas in the territory of China. Different from a conventional natural gas reservoir, the coal bed gas is mainly stored by absorbing gas, a critical desorption phenomenon exists in the production process, a single-phase liquid flow exists in a reservoir before critical desorption, and two flow states, namely a gas-liquid two-phase flow and a single-phase gas flow, exist in the reservoir after critical desorption. Therefore, the critical desorption characteristics of coal bed gas are a key issue for carrying out coal bed gas development design. At present, a large amount of work is done by scholars at home and abroad on the research of the coal bed gas critical desorption characteristics, and the critical desorption dynamics is presumed by the adsorption and desorption experiments of the coal bed gas. However, the critical desorption process of the coal bed gas is a multi-phase fluid coupling mass transfer process, and the critical desorption characteristics of the coal bed gas are difficult to directly obtain through single-phase experimental research. At present, the physical simulation research of the coal bed gas critical desorption still stays in the theoretical aspect, and no system and method capable of carrying out physical simulation on the coal bed gas critical desorption process exist.

Disclosure of Invention

Aiming at the problems, the invention provides a physical simulation system and a physical simulation method for coal bed gas critical desorption, which are suitable for researching the critical desorption characteristics of the coal bed gas and the gas-liquid two-phase flow characteristics in the critical desorption process.

The invention adopts the following technical scheme:

a physical simulation system for critical desorption of coal bed gas comprises: the system comprises an adsorbed 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 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 sand filling box through a pipeline and extends into the sand filling box, and starting differential pressure check valves are arranged in the pipeline in the sand filling box in a radial direction in parallel.

Preferably, the adsorbed gas simulation system comprises a high-pressure gas cylinder and an intermediate container, the high-pressure gas cylinder is connected with the inlet end of the 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 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 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 number of the starting pressure difference one-way valves is at least 6, the starting pressure difference is 0.1Bar, and when the pressure difference between the two ends of the starting pressure difference one-way valve (5) is greater than 0.1Bar, the fluid is allowed to pass through in one direction.

A method of utilizing a physical simulation system of coal bed methane critical desorption comprises the following steps:

s1, sand filling and saturated water process: filling sand into a sand filling box, and stopping filling water when the water in the sealed transparent barrel (7) does not overflow through a coal bed water saturation system;

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

s3, well bore extraction process: slowly pumping out water in the sealed transparent barrel through a first constant-speed pump;

s4, 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 sand has a mesh size of 50 mesh and a weight of 200 Kg.

Preferably, in step S2, the aeration is stopped when the pressure in the intermediate container is 0.12 MPa.

Preferably, in step S3, the first constant-speed pumping water rate is 5.3 ml/min.

The invention has the beneficial effects that:

the method provided by the invention is used for testing the gas-liquid flow characteristics in the critical desorption of the coal bed gas aiming at the critical desorption characteristics of the coal bed gas, the testing process is scientific, the testing result is accurate, and good conditions are created for the effective development of the coal bed gas.

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-high pressure gas cylinder, 21-first needle valve, 22-second needle valve, 23-third needle valve, 31-first pressure gauge, 32-second pressure gauge, 33-third pressure gauge, 4-intermediate container, 5-start pressure difference one-way valve, 6-filling box, 7-sealed transparent barrel, 81-first constant speed pump, 82-second constant speed pump, 9-measuring cylinder, 10-gas flowmeter, 11-gas recovery device, 12-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 physical simulation system for critical desorption of coal bed gas comprises: the system comprises an adsorbed 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 left end of the critical desorption simulation system through a pipeline;

the adsorption gas simulation system comprises a high-pressure gas bottle 1 and an intermediate container 4, wherein the high-pressure gas bottle 1 is connected with the inlet end of the intermediate container 4 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 intermediate container 4;

the high-pressure gas bottle 1 provides gas with a certain pressure for a system, the gas in the high-pressure gas bottle 1 is introduced into the intermediate container 4 to simulate the adsorption gas amount, the volume of the intermediate container 4 is 5L, the pressure can be applied to 8MPa, the gas in the intermediate container 4 can be sealed through the first needle valve 21, and the pressure change in the intermediate container 4 can be measured through the first pressure gauge 31.

The coal seam water saturation system comprises a water tank 12 and a second constant-speed pump 82, wherein the inlet end of the second constant-speed pump 82 is connected with the water tank 12 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;

the water in the water tank 12 was pumped into the filling flask 6 by the second constant speed pump 82, the final pressure during the saturated water process and the initial pressure in the filling flask 6 at the start of the experiment were measured by the second pressure gauge 32, and the water supply in the filling flask 6 was closed by closing the third needle valve 23.

The shaft drainage and production simulation and gas-liquid flow rate measurement system comprises a sealed transparent barrel 7, a first constant-speed pump 81, a measuring cylinder 9 and a gas recovery device 11, wherein the inlet end of the first constant-speed pump 81 is connected with the bottom end of the sealed transparent barrel 7 through a pipeline, and the outlet end of the first constant-speed pump is connected with the measuring cylinder 9 through a pipeline; the upper end of the sealed transparent barrel 7 is sealed and is connected with the gas recovery device 11 through a pipeline, and a third pressure gauge 33 and a gas flowmeter 10 are arranged on the pipeline connecting the sealed transparent barrel 7 and the gas recovery device 11;

the water in the sealed transparent barrel 7 is discharged through the first constant speed pump 81, the sealed transparent barrel 7 is cylindrical, the diameter is 127mm, the wall thickness is 10mm, the height is 3000mm, the discharged water amount is measured through the measuring cylinder 9, when the system starts to generate gas, the pressure in the sealed transparent barrel is measured through the third pressure gauge 33, the gas flow is measured through the gas flowmeter 10, and the discharged gas is recovered through the gas recovery device 11.

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 sand filling box 6 through a pipeline and extends into the sand filling box 6, and the pipeline in the sand filling box 6 is provided with starting differential pressure check valves 5 in a radial direction in parallel;

the communication degree between the intermediate container 4 and the starting differential pressure single-phase valve 5 is controlled through the second needle valve 22, the size of the filling box 6 is 300mm multiplied by 500mm multiplied by 1000mm, the filling sand can simulate the seepage environment of porous media, the number of the starting differential pressure single-phase valves (5) is at least 6, but not limited to 6, the starting differential pressure single-phase valve 5 is arranged in the middle of the filling box 6 and is connected with the second needle valve 22 through a pressure-resistant pipeline, the starting differential pressure single-phase valve 5 can allow fluid to flow in a single direction under the differential pressure condition of 0.1Bar, when the water pressure in the filling box 6 is reduced, the difference between the water pressure and the gas pressure in the intermediate container 4 reaches a threshold value, the starting differential pressure single-phase valve 5 is opened, and the gas flows into the filling box 6 from the intermediate container 4, so.

A method of utilizing a physical simulation system of coal bed methane critical desorption comprises the following steps:

s1, sand filling and saturated water process:

1. 200kg of sand with the mesh diameter of 50 meshes is screened, sand grains are wetted by distilled water in advance, and the wetted sand grains are filled into a sand filling box 6;

2. opening the second constant-speed pump 82, and introducing the water in the water tank 12 into the filling box 6, so that the saturated water in the filling box 6 completely submerges the sand in the filling box 6, and stopping the saturated water when the water in the sealed transparent barrel 7 does not overflow;

s2, an adsorbed gas simulation process:

1. closing the second needle valve 22, opening the first needle valve 21, and filling a certain amount of gas into the intermediate container 4 through the high-pressure gas bottle 1 to ensure that the pressure in the intermediate container 4 is 0.12 MPa;

2. closing the first needle valve 21, measuring the real-time change of the pressure in the intermediate container 4 by the first pressure gauge 31;

3. opening the second needle valve 22 to simulate the gas production process of the coal bed gas;

s3, well bore extraction process: slowly pumping water in the sealed transparent barrel 7 by a first constant speed pump 81, wherein the pumping speed is 5.3 ml/min;

s4, critical desorption and gas-liquid measurement process: constantly measure the water yield of slowly taking out through first constant speed pump 81, after gaseous output, measure the gas pressure in sealed transparent bucket 7 through third pressure gauge 33, measure gas flow through gas flowmeter 10, retrieve the gas in the experiment through gas recovery unit 11.

The test results are shown in fig. 2 to 3, fig. 2 showing the pressure changes measured by the first pressure gauge 31, the second pressure gauge 32, and the third pressure gauge 33, and fig. 3 showing the water discharge dynamics obtained by the measuring cylinder 9 and the gas generation dynamics obtained by the gas flowmeter 10.

In fig. 2, the first pressure gauge 31 has a dynamic that is first kept constant and then reduced, which indicates that the gas production occurs at a certain pressure drop; the change in the second pressure gauge 32 is constantly decreasing, representing a constant decrease in reservoir pressure; the dynamics of the third pressure gauge 33, which is maintained at 0 first and then increased and then decreased, indicates that the pressure dynamics is completely consistent with the actual process of coal bed gas production, which occurs after the drainage has proceeded to a certain extent during gas production. Meanwhile, the gas and water production curves in fig. 3 are completely consistent with the curve form in the coal bed methane numerical simulation. Therefore, the experimental result of the device can better reflect the reservoir gas-water flow process and the production dynamics of the gas well in the actual production of the coal bed gas.

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.