Device for simulating CH4 and gas nonlinear seepage of CO2-driven coal seam

Abstract

The utility model discloses a device for simulating CH4 and gas nonlinear seepage of a CO2-driven coal seam, which comprises a deep coal seam environment simulation system, a gas source constant pressure control device, a back pressure device, a vacuum device, a gas collection device and a data acquisition device, and the deep coal seam environment simulation system comprises a holder framework, a hand pump, a pressure gauge I and a pressure sensor III. A temperature control device sleeves the holder framework, a cavity is formed in the holder framework, a rubber sleeve is arranged in the cavity, a pair of coal body contact ends are symmetrically arranged at the two ends of the rubber sleeve, the free ends of the pair of coal body contact ends abut against threaded ends, the cavity is communicated with a hand pump through a first water pipe, and a fourth valve is arranged on the first water pipe; the first pressure gauge is used for detecting pressure in the cavity, and the third pressure sensor is used for detecting pressure in the rubber sleeve. The unknown problems of gas adsorption (CO2 sequestration) of a coal seam, a CO2 displacement coal seam CH4 rule, a migration process of multi-component gas in a coal body and the like are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of simulation experimental devices, in particular to a device for simulating the nonlinear seepage of CH4 and gas in coal seams driven by CO2. Background Art

[0002] China is not only rich in coal resources, but also in coal mine gas resources. Among them, the CMM reserves below 2000m reach 3.681×10 13 m 3 , which is equivalent to 4.2×l0 10 t standard coal. With the increasing depth of coal seam mining year by year, some mining mines have been transformed into high-gas / outburst mines, and other deep coal seams have been transformed into unminable coal seams. In response to the above situation, CO2 displacement of coal seam CH4 came into being, which can not only improve the gas recovery rate of coal seams, effectively reduce gas disasters in mining mines, and reduce the pollution of emissions to the environment; it can also achieve CO2 storage in deep unminable coal seams, and promote my country's energy transformation and achieve the long-term goal of "carbon peak in 2030 and carbon neutrality in 2060". Deep coal seams have the characteristics of high ground stress, high gas pressure, and high ground temperature. These basic characteristics seriously affect the migration of CO2 / CH4 in coal seams, and ultimately affect the effect of gas extraction and CO2 storage. Utility Model Content

[0003] The utility model aims to provide a device for simulating CO2 displacement of coal seam CH4 and nonlinear gas seepage, so as to solve unknown problems such as coal seam adsorption of gas (CO2 storage), CO2 displacement of coal seam CH4 law and migration process of multi-component gas in coal body.

[0004] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a device for simulating CO2-driven coal seam CH4 and gas nonlinear seepage, including a deep coal seam environment simulation system, a gas source constant pressure control device, a back pressure device, a vacuum device, a gas collection device, and a data acquisition device.

[0005] The deep coal seam environment simulation system includes a clamp frame, a hand pump, a pressure gauge 1 and a pressure sensor 3. The outer shell of the clamp frame is provided with a temperature control device. A chamber is opened in the clamp frame. A rubber sleeve is arranged in the chamber. A pair of coal body contact ends are symmetrically arranged at both ends of the rubber sleeve. The free ends of the pair of coal body contact ends are abutted with threaded ends. The chamber is connected to the hand pump through a water pipe 1. A valve 4 is arranged on the water pipe 1. The pressure gauge 1 is used to detect the pressure in the chamber. The pressure sensor 3 is used to detect the pressure in the rubber sleeve. The hand pump, the pressure gauge 1 and the pressure sensor 3 are arranged outside the temperature control device.

[0006] The gas source constant pressure control device includes a gas cylinder, which is connected to a gas booster pump through gas pipe 1, which is connected to a high-pressure container through gas pipe 2, which is connected to an air compressor for providing power, valve 1 is provided on gas pipe 2, a pressure gauge 3 for detecting the internal pressure of the high-pressure container is provided outside the high-pressure container, the high-pressure container is connected to a pressure regulating valve through gas pipe 3, valve 2 is provided on gas pipe 3, and the free end of the pressure regulating valve is connected to the deep coal seam environment simulation system.

[0007] The back pressure device comprises a buffer tank, which is connected to the hand pump through a second water pipe, a valve five is arranged on the second water pipe, and the buffer tank is connected to a second pressure gauge and a back pressure valve.

[0008] The vacuum device includes a vacuum pump, which is connected to the deep coal seam environment simulation system through an air pipe four, a valve eight is provided on the air pipe four, and air pipes five and six are provided at both ends of the rubber sleeve, respectively, and the air pipes five and six are connected to the air pipe four respectively, the air pipe five is provided with a valve three, a CH4 mass flowmeter one, a CO2 mass flowmeter one and a pressure sensor two, and the air pipe six is ​​provided with a valve six, a CH4 mass flowmeter two, a CO2 mass flowmeter two and a pressure sensor one.

[0009] The gas collection device comprises an exhaust gas recovery box, and the exhaust gas recovery box is connected to the exhaust pipes five and six through the exhaust pipe seven, and the exhaust pipe seven is provided with a valve nine.

[0010] The data acquisition device includes a data acquisition instrument and a gas chromatograph. The data acquisition instrument is respectively connected to the pressure sensor 2, pressure sensor 3, CH4 mass flowmeter 1, CH4 mass flowmeter 2, CO2 mass flowmeter 1, CO2 mass flowmeter 2 and pressure sensor 1. The gas chromatograph and the deep coal seam environment simulation system are connected through an air pipe 8, and a valve 7 is provided on the air pipe 8.

[0011] Preferably, the pressure sensor is connected to a tee below.

[0012] Preferably, a plurality of pressure measuring ports are provided on the side wall of the rubber sleeve.

[0013] Preferably, a plurality of grooves are formed on the end surface of the coal body contacting end head.

[0014] The principle and beneficial effects of this technical solution:

[0015] The experimental device mainly includes gas source supply device, gas pressure control device, deep coal seam environment simulation system, back pressure device, gas collection device, pressure flow and other data acquisition devices. The device can simulate the geological characteristics of high stress, high ground temperature and high gas in deep coal seams, and solve unknown problems such as coal seam adsorption of gas (CO2 storage), CO2 displacement of coal seam CH4 law and migration process of multi-component gas in coal body. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A device system diagram of a device for simulating CO2 flooding of coal seam CH4 and gas nonlinear seepage provided in an embodiment of the utility model;

[0017] Figure 2 A rubber sleeve structure diagram of a device for simulating CO2 flooding of coal seam CH4 and gas nonlinear seepage provided in an embodiment of the utility model;

[0018] Figure 3 An end view of a coal body contact end of a device for simulating nonlinear seepage of CO2 flooding coal seam CH4 and gas provided in an embodiment of the utility model;

[0019] In the figure: 1. gas booster pump; 2. gas cylinder; 3. air compressor; 4. valve 1; 5. high pressure container; 6. pressure gauge 3; 7. valve 2; 8. pressure regulating valve; 9. pressure sensor 2; 10. CH4 mass flow meter 1; 11. CO2 mass flow meter 1; 12. valve 3; 13. threaded end; 14. temperature control device; 15. coal body contact end; 16. clamp frame; 17. pressure sensor 3; 18. chamber; 19. rubber sleeve; 20 1. Pressure gauge one; 21. Valve four; 22. Hand pump; 23. Valve five; 24. Buffer tank; 25. Pressure gauge two; 26. Pressure sensor one; 27. Back pressure valve; 28. Valve six; 29. ​​CH4 mass flow meter two; 30. CO2 mass flow meter two; 31. Valve seven; 32. Gas chromatograph; 33. Valve eight; 34. Vacuum pump; 35. Valve nine; 36. Exhaust recovery box; 37. Data acquisition instrument; 38. Pressure measuring port; 39. Groove. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below with reference to the accompanying drawings and implementation modes:

[0021] like Figure 1 A device for simulating CO2 displacement of CH4 and nonlinear gas seepage in coal seams is shown, comprising a deep coal seam environment simulation system, a gas source constant pressure control device, a back pressure device, a vacuum device, a gas collection device, and a data acquisition device.

[0022] The deep coal seam environment simulation system includes a clamp frame 16, a hand pump 22, a pressure gauge 20 and a pressure sensor 3 17. The outer cover of the clamp frame 16 is provided with a temperature control device 14. A chamber 18 is opened in the clamp frame 16, and a rubber sleeve 19 is arranged in the chamber 18. A pair of coal body contact ends are symmetrically arranged at both ends of the rubber sleeve 19, and the free ends of the pair of coal body contact ends are abutted with threaded ends 13. The chamber 18 is connected to the hand pump 22 through a water pipe 1, and a valve 4 21 is arranged on the water pipe 1. The pressure gauge 20 is used to detect the pressure in the chamber 18, and the pressure sensor 3 17 is used to detect the pressure in the rubber sleeve 19. The hand pump 22, the pressure gauge 20 and the pressure sensor 3 17 are arranged outside the temperature control device 14; a Φ50mm×500mm coal sample is loaded into the rubber sleeve 19, and the coal body contact ends 15 at both ends are pushed into the rubber sleeve 19, and then the threaded ends 13 are tightened. Water is pressed into the chamber 18 by the hand pump 22 to pressurize the coal core to simulate the high ground pressure environment of the deep coal seam. When the pressure gauge 20 reaches a certain value, the valve 4 21 is closed. The experimental temperature is set by the temperature control device 14 to simulate the temperature environment of the deep coal seam.

[0023] The gas source constant pressure control device includes a gas cylinder 2, which is connected to a gas booster pump 1 through a gas pipe 1, which is connected to a high-pressure container 5 through a gas pipe 2, which is connected to an air compressor 3 for providing power, a valve 1 4 is provided on the gas pipe 2, a pressure gauge 3 6 for detecting the internal pressure of the high-pressure container 5 is provided outside the high-pressure container 5, and a pressure regulating valve 8 is connected to the high-pressure container 5 through a gas pipe 3, which is provided with a valve 2 7, and the free end of the pressure regulating valve 8 is connected to the deep coal seam environment simulation system. The gas is injected into the gas booster pump 1 from the gas cylinder 2, and the outlet gas of the air compressor 3 flows into the gas booster pump 1 to provide power for the pump, flows through the valve 1 4, and is injected into the high-pressure container 5 to obtain different gas source pressure values, and the valve 2 7 is opened to adjust the pressure value required for the experiment through the pressure regulating valve 8.

[0024] The back pressure device includes a buffer tank 24, which is connected to the hand pump 22 through a water pipe 2, a valve 5 23 is provided on the water pipe 2, and the buffer tank 24 is connected to a pressure gauge 25 and a back pressure valve 27. The valve 5 23 is opened, and water is pressed into the buffer tank 24 through the hand pump 22. When the pressure gauge 25 reaches a certain value, the valve 5 23 is closed, and the back pressure device can form a stable tail pressure.

[0025] The vacuum device includes a vacuum pump 34, which is connected to the deep coal seam environment simulation system through an air pipe four. A valve eight 33 is provided on the air pipe four. Air pipe five and air pipe six are provided at both ends of the rubber sleeve 19, respectively. Air pipe five and air pipe six are connected to air pipe four respectively. Valve three 12, CH4 mass flow meter one 10, CO2 mass flow meter two 30 and pressure sensor two 9 are provided on the air pipe five. Valve six 28, CH4 mass flow meter two 29, CO2 mass flow meter two 30 and pressure sensor one 26 are provided on the air pipe six. Open valve three 12, valve six 28 and valve eight 33 in sequence, and turn on the vacuum pump 34 to evacuate the entire system.

[0026] The gas collection device includes an exhaust gas recovery box 36, which is connected to the exhaust gas recovery box 36 through the exhaust pipe 7, the exhaust pipe 5 and the exhaust pipe 6. The exhaust pipe 7 is provided with a valve 9 35 to prevent the exhaust gas from being directly discharged to the external environment.

[0027] The data acquisition device includes a data acquisition instrument 37 and a gas chromatograph 32. The data acquisition instrument 37 is respectively connected to the pressure sensor 29, the pressure sensor 317, the CH4 mass flowmeter 10, the CH4 mass flowmeter 29, the CO2 mass flowmeter 11, the CO2 mass flowmeter 230 and the pressure sensor 26. The gas chromatograph 32 is connected to the deep coal seam environment simulation system through an air pipe 8. A valve 7 31 is provided on the air pipe 8. The inlet and outlet pressures of the clamp, the inlet and outlet CO2 and CH4 mass flows and the pore pressure along the process are monitored in real time through the data acquisition instrument 37.

[0028] Preferably, a three-way connection is provided below the pressure sensor 17, so that the gas components at various points along the process can be monitored in real time.

[0029] like Figure 2 As shown, a plurality of pressure measuring ports 38 are provided on the side wall of the rubber sleeve 19 .

[0030] like Figure 3 As shown, a plurality of grooves 39 are formed on the end surface of the coal body contacting end head 15 .

[0031] The specific implementation process is as follows:

[0032] Step 1: Collect large coal samples underground and transport them to the CO2 flooding coal seam CH4 and gas nonlinear seepage laboratory;

[0033] Step 2: Drill core samples with specifications of Φ50mm×100mm, select coal pillars with intact surfaces, and put them into a vacuum drying oven for drying;

[0034] Step 3: Check the air tightness and integrity of the CO2 flooding coal seam CH4 and gas nonlinear seepage experimental device;

[0035] Step 4: Rotate and unscrew the threaded ends 13 at both ends of the gripper, remove the coal body contact end 15, and insert 3 intact coal pillars with a specification of Φ50mm×100mm into the rubber sleeve 19. Subsequently, insert the coal body contact end 15 and rotate and tighten the threaded ends 13 at both ends of the gripper.

[0036] Step 5: Open valve 1 4, valve 2 7, valve 3 12, valve 6 28, valve 7 31, and valve 8 33, start the vacuum pump 34, and perform vacuum pumping on the system for 12 h continuously. Subsequently, stop the vacuum pump 34 and close valve 1 4, valve 2 7, valve 3 12, valve 6 28, valve 7 31, and valve 8 33.

[0037] Step 6: Open valve 5 23, and pump water into the buffer tank 24 through the hand pump 22. When the pressure gauge 2 25 reaches the specified pressure P1, the trigger pressure for the back pressure valve 27 to start is P1 at this time. Subsequently, close valve 5 23.

[0038] Step 9: Open the gas cylinder 2 (CO2 / CH4), and open valve 1 4. Subsequently, open the air compressor 3 and start the gas booster pump 1 to fill the gas into the buffer tank 24. When the pressure of the buffer tank 24 reaches P2 (P2 > P1), stop the gas booster pump 1 and the air compressor 3 simultaneously, and close the gas cylinder 2.

[0039] Step 8: Turn on the temperature control device 14 and set the temperature to the formation temperature T0.

[0040] Example 1: Gas seepage law scheme

[0041] Step 9: Open the gas cylinder 2 (CO2 / CH4), and open valve 1 4. Subsequently, open the air compressor 3 and start the gas booster pump 1 to fill the gas into the buffer tank 24. When the pressure of the buffer tank 24 reaches P2 (P2 > P1), stop the gas booster pump 1 and the air compressor 3 simultaneously, and close the gas cylinder 2.

[0042] Step 10: Adjust the pressure regulating valve 8 to the experimental constant pressure P3 (P1 < P3 < P2), turn on the data acquisition instrument 37, and monitor the pressure sensor 2 9, CH4 mass flowmeter 1 10, CO2 mass flowmeter 1 11, pressure sensor 3 17, pressure sensor 1 26, CH4 mass flowmeter 2 29, and CO2 mass flowmeter 2 30 in real time. At the same time, open valve 3 12 and valve 6 28 (open the corresponding valves according to the gas type), and valve 9 35.

[0043] Step 11: Open valve 2 7 to start the nonlinear gas seepage test. The pressure drop law of the gas seepage process is analyzed through the constant pressure P3 provided by the pressure regulating valve, the pressure sensor 3 17 and the back pressure valve trigger pressure P1. In addition, the data are monitored by CH4 mass flow meter 10, CO2 mass flow meter 11, CH4 mass flow meter 29 and CO2 mass flow meter 2 30, and the adsorption law of coal to gas is analyzed by formula (1). Finally, based on the pressure drop law and the gas adsorption law, the nonlinear relationship between pressure gradient and flow rate is explored.

[0044]

[0045] Where V is the gas adsorption per unit mass of coal sample, m 3 / g; Q2 is the data measured by CH4 mass flowmeter 29 or CO2 mass flowmeter 230, g / min; Q1 is the data measured by CH4 mass flowmeter 10 or CO2 mass flowmeter 11, g / min; t is the test time, min; m is the mass of the coal sample, g.

[0046] Example 2: CO2 displacement scheme for replacing CH4 in coal seams

[0047] Step 9: Open gas cylinder 2 (CH4) and open valve 1 4. Then, turn on the air compressor 3 and the gas booster pump 1 to fill the gas into the buffer tank 24. When the pressure of the buffer tank 24 reaches P2 (P2>P1), turn off the gas booster pump 1 and the air compressor 3 at the same time, and close the gas cylinder 2.

[0048] Step 10: Adjust the pressure regulating valve 8 to a constant adsorption pressure P1, open the data acquisition instrument 37, and monitor in real time the pressure sensor 2 9, the CH4 mass flow meter 1 10, the pressure sensor 3 17, the pressure sensor 4 26, and the CH4 mass flow meter 2 29. At the same time, open the valve 3 12, the valve 6 28, and the valve 9 35.

[0049] Step 11: Open valve 27 to start the CH4 gas adsorption experiment, continue adsorption for 24 hours, wait for adsorption equilibrium, stop the experiment, and close valve 312, valve 628 and valve 935. At this time, the data is monitored by CH4 mass flow meter 10 and CH4 mass flow meter 29, and the adsorption amount V of unit mass coal on CH4 gas is analyzed by formula (1): CH4 , and then the total adsorption amount V1 within time t1 is obtained.

[0050]

[0051] Step 12: Open the gas cylinder 2 (CO2) and open valve 1-4. Subsequently, turn on the air compressor 3 and start the gas booster pump 1 to fill the gas into the buffer tank 24. When the pressure in the buffer tank 24 reaches P2 (P2 > P1), stop the gas booster pump 1 and the air compressor 3 simultaneously and close the gas cylinder 2.

[0052] Step 13: Adjust the pressure regulating valve 8 to the constant adsorption pressure P4 (P1 < P4 < P2), turn on the data acquisition instrument 37, and monitor the pressure sensor 9, CH4 mass flowmeter 1-10, CO2 mass flowmeter 1-11, pressure sensor 3-17, pressure sensor 26, CH4 mass flowmeter 2-29, and CO2 mass flowmeter 2-30 in real time. At the same time, open valve 3-12, valve 6-28, valve 7-31, and the gas chromatograph 32 to analyze the gas components in real time.

[0053] Step 14: Open valve 2-7 to start the CO2 displacement of CH4 in the coal seam experiment. Stop the experiment when the gas components analyzed by the gas chromatograph 32 are stable. At this time, obtain the desorption volume V2 of CH4 within the time t2 through the CH4 mass flowmeter 2-29; obtain the adsorption volume V3 of CO2 within the time t2, that is, the CO2 sequestration volume, through the CO2 mass flowmeter 1-11 and the CO2 mass flowmeter 2-30.

[0054]

[0055] The displacement ratio η of CO2 displacing and replacing CH4 in the coal seam can be calculated by Equation (5).

[0056]

[0057] The above are only the embodiments of the present invention. Specific technical solutions or common knowledge such as characteristics that are well known in the art are not described in detail here. For those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be subject to the content of its claims, and the specific implementation manners described in the specification can be used to explain the content of the claims.

Claims

1. A device for simulating nonlinear seepage of CH4 and gas in coal seams by CO2 flooding, characterized in that: It includes deep coal seam environment simulation system, gas source constant pressure control device, back pressure device, vacuum device, gas collection device and data acquisition device; The deep coal seam environment simulation system comprises a clamp frame (16), a hand pump (22), a pressure gauge (20) and a pressure sensor (17); the clamp frame (16) is provided with a temperature control device (14) on its outer cover; a chamber (18) is provided in the clamp frame (16); a rubber sleeve (19) is provided in the chamber; a pair of coal body contact ends (15) are symmetrically provided at both ends of the rubber sleeve (19); a pair of free ends of the coal body contact ends (15) are abutted against a threaded end (13); the chamber (18) is connected to the hand pump (22) through a water pipe (1); a valve (21) is provided on the water pipe (1); the pressure gauge (20) is used to detect the pressure in the chamber (18); the pressure sensor (17) is used to detect the pressure in the rubber sleeve (19); the hand pump (22), the pressure gauge (20) and the pressure sensor (17) are provided outside the temperature control device (14); The gas source constant pressure control device comprises a gas cylinder (2), the gas cylinder (2) is connected to a gas booster pump (1) through a gas pipe 1, the gas booster pump (1) is connected to a high-pressure container (5) through a gas pipe 2, the gas booster pump (1) is connected to an air compressor (3) for providing power, a valve 1 (4) is provided on the gas pipe 2, a pressure gauge 3 (6) for detecting the internal pressure of the high-pressure container (5) is provided outside the high-pressure container (5), the high-pressure container (5) is connected to a pressure regulating valve (8) through a gas pipe 3, a valve 2 (7) is provided on the gas pipe 3, and the free end of the pressure regulating valve (8) is connected to the deep coal seam environment simulation system; The back pressure device comprises a buffer tank (24), the buffer tank (24) is connected to the hand pump (22) through a second water pipe, a fifth valve (23) is provided on the second water pipe, and the buffer tank (24) is connected to a second pressure gauge (25) and a back pressure valve (27); The vacuum device comprises a vacuum pump (34), the vacuum pump is connected to the deep coal seam environment simulation system through an air pipe four, the air pipe four is provided with a valve eight (33), the two ends of the rubber sleeve are provided with an air pipe five and an air pipe six, the air pipe five and the air pipe six are respectively connected to the air pipe four, the air pipe five is provided with a valve three (12), a CH4 mass flow meter one (10), a CO2 mass flow meter one (11) and a pressure sensor two (9), the air pipe six is ​​provided with a valve six (28), a CH4 mass flow meter two (29), a CO2 mass flow meter two (30) and a pressure sensor one (26); The gas collection device comprises an exhaust gas recovery box (36), the exhaust gas recovery box (36) is connected to the exhaust pipes five and six through an exhaust pipe seven, and a valve nine (35) is provided on the exhaust pipe seven; The data acquisition device comprises a data acquisition instrument (37) and a gas chromatograph (32). The data acquisition instrument is respectively connected to the pressure sensor 2 (9), the pressure sensor 3 (17), the CH4 mass flowmeter 1 (10), the CH4 mass flowmeter 2 (29), the CO2 mass flowmeter 1 (11), the CO2 mass flowmeter 2 (30) and the pressure sensor 1 (26). The gas chromatograph (32) and the deep coal seam environment simulation system are connected via an air pipe 8, and a valve 7 (31) is provided on the air pipe 8.

2. The device for simulating nonlinear seepage of CH4 and gas in coal seams by CO2 flooding according to claim 1, characterized in that: The pressure sensor 3 (17) is connected to a tee below.

3. The device for simulating nonlinear seepage of CH4 and gas in coal seams by CO2 flooding according to claim 1, characterized in that: The side wall of the rubber sleeve (19) is provided with a plurality of pressure measuring ports (38).

4. The device for simulating nonlinear seepage of CH4 and gas in coal seams by CO2 flooding according to claim 1, characterized in that: The end surface of the coal body contact end head is provided with a plurality of grooves (39).

Images