System for displacing coal seam gas through bedding hole pulsation circulation alternate water injection and gas injection

Abstract

The utility model discloses a system for displacing coal seam gas through bedding hole pulsation circulation alternate water and gas injection. A high-pressure gas pulsation injection unit comprises a gas storage tank and a high-pressure gas injection pump. The inlet end of the high-pressure gas injection pump is connected with the gas outlet of the gas storage tank through a high-pressure gas supply pipeline, and the outlet end is connected with the gas inlet end of the high-pressure gas injection pipeline; the high-pressure pulse water injection unit comprises a water storage tank and a high-pressure water injection pump; the inlet end of the high-pressure water injection pump is connected with the water outlet of the water storage tank through a high-pressure water supply pipeline; the displacement operation unit comprises a tee joint, a displacement operation pipeline, a drainage pipeline and a high-pressure capsule; the inlet end of the displacement operation pipeline is connected with the gas outlet end of the high-pressure gas injection pipeline and the water outlet end of the high-pressure water injection pipeline through a tee joint, and the outlet end of the displacement operation pipeline extends into a drill hole; the drainage pipeline is connected to one side of the outlet end of the displacement operation pipeline; the high-pressure capsules are arranged outside the outlet end of the displacement operation pipeline in a sleeving mode at intervals. The system can effectively solve the problem of low coal seam gas extraction rate.

Description

Technical Field

[0001] The utility model belongs to the technical field of coal mine safety, and in particular relates to a system for alternately injecting water and gas to displace coal seam gas through pulsating circulation of beds. Background Art

[0002] my country's coal seam gas storage has the characteristics of "three lows and one high" (low saturation, low permeability, low reservoir pressure, high adsorption), and gas extraction is a fundamental technical measure to achieve gas disaster prevention and control. At present, China mainly uses technical measures such as high-pressure hydraulic fracturing (or displacement), water splitting (or punching), coal seam pre-splitting blasting (explosive blasting, CO2 phase change blasting, high-voltage electric pulse fracturing, etc.) to improve the permeability of coal seams. However, it is difficult to promote the desorption of gas in nano-scale pores by only improving the permeability of coal seams, and thus it still cannot completely solve the problem of low coal seam gas extraction rate.

[0003] Therefore, it is urgent to provide a system for displacing coal seam gas by pulsating and cyclically injecting water and gas in the layer holes, so as to effectively solve the problem of low coal seam gas extraction rate. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the utility model provides a system for displacing coal seam gas by pulsating and cyclically alternating water and gas injection along the layer holes. The system can perform high-pressure pulse water and gas injection operations on the coal seams, which can effectively solve the problem of low coal seam gas extraction rate. The system can efficiently displace gas and effectively eliminate the water lock effect caused by hydraulic displacement. It is especially suitable for coal seams with high adsorption that are difficult to displace gas by water injection, and can provide important technical guarantee for the efficient extraction of gas contained in coal.

[0005] In order to achieve the above-mentioned purpose, the utility model provides a system for displacing coal seam gas by pulsating and cyclically alternating water and gas injection in the layer holes, comprising a high-pressure gas pulsating injection unit, a high-pressure pulsating water injection unit and a displacement operation unit;

[0006] The high-pressure gas pulsation injection unit comprises a gas storage tank, a high-pressure gas injection pump and a high-pressure stop valve; the gas storage tank is filled with gas; the high-pressure gas injection pump is used for pulse gas injection operation, the inlet end of which is connected to the gas outlet of the gas storage tank through a high-pressure gas supply pipeline, and the outlet end of which is connected to the gas inlet end of the high-pressure gas injection pipeline; the high-pressure stop valve is connected in series to the high-pressure gas injection pipeline;

[0007] The high-pressure pulsating water injection unit comprises a water storage tank, a high-pressure water injection pump and a high-pressure stop valve 2; the water storage tank is filled with water; the high-pressure water injection pump is used for pulse water injection operation, the inlet end of which is connected to the water outlet of the water storage tank through a high-pressure water supply pipeline, and the outlet end of which is connected to the water inlet end of the high-pressure water injection pipeline; the high-pressure stop valve 2 is connected in series to the high-pressure water injection pipeline;

[0008] The displacement operation unit includes a tee, a displacement operation pipeline, a drainage pipeline, a high-pressure stop valve and a high-pressure capsule; the two inlet ends of the tee are respectively connected to the gas outlet end of the high-pressure gas injection pipeline and the water outlet end of the high-pressure water injection pipeline; the inlet end of the displacement operation pipeline is connected to the outlet end of the tee, and its operation section extends into the borehole; the drainage pipeline is connected to one side of the outlet end of the displacement operation pipeline; the high-pressure stop valve is connected in series to the drainage pipeline; two high-pressure capsules are spaced apart and mounted on the outside of the outlet end of the displacement operation pipeline, and the gap between the displacement operation pipeline and the borehole wall is sealed; a fracturing outlet is opened in the part of the displacement operation pipeline between the two high-pressure capsules.

[0009] Furthermore, in order to facilitate switching the on / off state of the high-pressure gas supply pipeline, the high-pressure gas pulsation injection unit also includes a high-pressure stop valve four, and the high-pressure stop valve four is connected in series to the high-pressure gas supply pipeline.

[0010] Furthermore, in order to facilitate switching the on / off state of the high-pressure water supply pipeline, the high-pressure pulsating water injection unit also includes a high-pressure stop valve five, and the high-pressure stop valve five is connected in series to the high-pressure water supply pipeline.

[0011] Furthermore, in order to better promote the migration of gas, the working pressure range of the high-pressure gas injection pump is 0 to 10 MPa.

[0012] Furthermore, in order to improve the pre-cracking effect on the coal seam, the working pressure range of the high-pressure water injection pump is 10 to 30 MPa.

[0013] In the utility model, the inlet end of the displacement operation pipeline is connected to the gas outlet end of the high-pressure gas injection pipeline and the water outlet end of the high-pressure water injection pipeline through a tee, and the high-pressure stop valve 1 and the high-pressure stop valve 2 are connected in series on the high-pressure gas injection pipeline and the high-pressure water injection pipeline, respectively, which can facilitate the quick switching of the gas injection and water injection states, so that pulse water injection and gas injection operations can be performed alternately. A high-pressure water injection pump for pulse water injection operation is connected in series between the water storage tank and the water inlet end of the high-pressure water injection pipeline, which can facilitate the use of the high-pressure water injection pump to pressurize the water, and then the high-pressure water can be used to efficiently impact the coal seam to obtain a crack with better permeability enhancement effect and a larger extension range. A high-pressure gas injection pump for pulse gas injection operation is connected in series between the gas storage tank and the air inlet end of the high-pressure gas injection pipeline, which can facilitate the use of the high-pressure gas injection pump to pressurize the gas, and then the high-pressure gas can be used to efficiently impact the coal seam, so as to fully solve the water lock effect generated after water injection, which is conducive to promoting the migration of gas in coal.

[0014] The utility model can pre-crack the coal body by pulsating and cyclically injecting high-pressure water into the coal seam, while displacing CH4 in the nano-scale pores, and can remove the "water lock" effect by pulsating and cyclically injecting air to fully drive the migration of multiphase media. The system can improve the problem of the fracture channel being blocked by coal particles due to the limited pressure of a single injection by means of pulsed water and gas injection. At the same time, the fracture channel generated by a single water and gas injection can be further extended by means of cyclic pulsed water and gas injection, so that the fracture forms a network channel that is more conducive to gas migration.

[0015] The system has simple equipment requirements and high gas displacement efficiency. It can effectively eliminate the water lock effect caused by hydraulic displacement. It is especially suitable for coal seams with high adsorption that are difficult to displace gas by water injection. It can provide important technical support for the efficient extraction of coal gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the utility model;

[0017] Figure 2 It is a schematic diagram of the state in which the driving operation pipeline of the utility model is assembled in the drill hole.

[0018] In the figure: 1. air inlet lane, 2. return air lane, 3. drilling hole, 4. cutting eye, 5. high-pressure gas injection pipeline, 6. high-pressure stop valve one, 7. high-pressure gas injection pump, 8. gas storage tank, 9. high-pressure water injection pump, 10. water storage tank, 11. coal seam, 12. high-pressure capsule, 13. high-pressure gas supply pipeline, 14. high-pressure water supply pipeline, 15. high-pressure water injection pipeline, 16. high-pressure stop valve two, 17. tee, 18. displacement operation pipeline, 19. drainage pipeline, 20. high-pressure stop valve three, 21. high-pressure stop valve four, 22. high-pressure stop valve five. DETAILED DESCRIPTION

[0019] The utility model will be further described below in conjunction with the accompanying drawings.

[0020] like Figure 1 and Figure 2 As shown, the utility model provides a system for displacing coal seam gas by pulsating and cyclically alternating water and gas injection in the layer holes, comprising a high-pressure gas pulsating injection unit, a high-pressure pulsating water injection unit and a displacement operation unit;

[0021] The high-pressure gas pulsation injection unit comprises a gas storage tank 8, a high-pressure gas injection pump 7 and a high-pressure stop valve 6; the gas storage tank 8 is filled with gas; the high-pressure gas injection pump 7 is used for pulse gas injection operation, and its inlet end is connected to the gas outlet of the gas storage tank 8 through a high-pressure gas supply pipeline 13, and its outlet end is connected to the gas inlet end of the high-pressure gas injection pipeline 5; the high-pressure stop valve 6 is connected in series to the high-pressure gas injection pipeline 5;

[0022] The high-pressure pulsating water injection unit comprises a water storage tank 10, a high-pressure water injection pump 9 and a high-pressure stop valve 16; the water storage tank 10 is filled with water; the high-pressure water injection pump 9 is used for pulse water injection operation, and its inlet end is connected to the water outlet of the water storage tank 10 through a high-pressure water supply pipeline 14, and its outlet end is connected to the water inlet end of the high-pressure water injection pipeline 15; the high-pressure stop valve 16 is connected in series to the high-pressure water injection pipeline 15;

[0023] The displacement operation unit includes a tee 17, a displacement operation pipeline 18, a drainage pipeline 19, a high-pressure stop valve 20 and a high-pressure capsule 12; the two inlet ends of the tee 17 are respectively connected to the gas outlet end of the high-pressure gas injection pipeline 5 and the water outlet end of the high-pressure water injection pipeline 15; the inlet end of the displacement operation pipeline 18 is connected to the outlet end of the tee 17, and its operation section extends into the borehole 3; the drainage pipeline 19 is connected to one side of the outlet end of the displacement operation pipeline 18; the high-pressure stop valve 20 is connected in series to the drainage pipeline 19; two high-pressure capsules 12 are spaced apart and mounted on the outside of the outlet end of the displacement operation pipeline 18, and the gap between the displacement operation pipeline 18 and the wall of the borehole 3 is sealed; the displacement operation pipeline 18 is provided with a fracturing outlet in the part between the two high-pressure capsules 12. Among them, the borehole 3 is located in the coal seam, such as Figure 1 As shown in Figure 1 In the example, the cut hole 4 is a tunnel connecting the air inlet tunnel 1 and the return air tunnel 2;

[0024] In order to facilitate switching the on and off state of the high-pressure gas supply pipeline, the high-pressure gas pulsation injection unit also includes a high-pressure shut-off valve four 21, and the high-pressure shut-off valve four 21 is connected in series to the high-pressure gas supply pipeline 13.

[0025] In order to facilitate switching the on / off state of the high-pressure water supply pipeline, the high-pressure pulsating water injection unit further includes a high-pressure stop valve 5 22 , and the high-pressure stop valve 5 22 is connected in series to the high-pressure water supply pipeline 14 .

[0026] In order to better promote the migration of gas, the working pressure range of the high-pressure gas injection pump 7 is 0-10MPa.

[0027] In order to improve the pre-cracking effect on the coal seam, the working pressure range of the high-pressure water injection pump 9 is 10-30 MPa.

[0028] How to use: Figure 1As shown, a borehole 13 is constructed in the coal seam 11 of the air intake tunnel 1, and two high-pressure capsules 12 are first installed on the outside of the working section of the displacement operation pipeline 18 at intervals, and then the working section of the displacement operation pipeline 18 together with the high-pressure capsule 12 are placed in the predetermined position in the borehole 13, and the expanded high-pressure capsule 12 is used to complete the sealing operation. Open high-pressure stop valve five 22, open high-pressure stop valve two 16, keep high-pressure stop valve one 6 in a closed state, keep high-pressure stop valve three 20 in a closed state, start the high-pressure water injection pump 9 to perform pulsating water injection operation, and the pulsating pressure is set as follows: set the initial pressure value, and then increase the water injection pressure by 1MPa every 5 minutes until the maximum pressure is reached, and then reduce the pressure by 1MPa every 5 minutes until it drops to the initial pressure. The pulsating water injection process lasts for 5 to 10 hours; close the high-pressure stop valve two 16, close the high-pressure water injection pump 9, close the high-pressure stop valve five 22, and open the high-pressure stop valve three 20, use the drainage pipe 19 to drain the residual water in the borehole 3, and then close the high-pressure stop valve three 20. Open the high-pressure stop valve 421, open the high-pressure stop valve 16, start the high-pressure gas injection pump 7 to perform pulsating gas injection operation, and the pulsating pressure is set as follows: set the initial pressure value, then increase the gas injection pressure by 1MPa every 5 minutes until the maximum pressure is reached, and then reduce the pressure by 1MPa every 5 minutes until it drops to the initial pressure. The pulsating gas injection process lasts for 5 to 10 hours; close the high-pressure stop valve 421, turn off the high-pressure gas injection pump 7, and close the high-pressure stop valve 16; then perform pulsating water injection operation and pulsating gas injection operation in turn, repeat the above process and set the cycle and stop. Among them, the interval time of pulsating water injection operation and pulsating gas injection operation can be flexibly changed according to the occurrence characteristics of the coal seam on site. The water pressure variation range of pulsating water injection operation is 10 to 30MPa, and the gas pressure variation range of pulsating gas injection operation is 0 to 10MPa. At the same time, it is preferred that the pulsating water injection operation and pulsating gas injection operation time are not less than 12 hours.

[0029] In the utility model, the inlet end of the displacement operation pipeline is connected to the gas outlet end of the high-pressure gas injection pipeline and the water outlet end of the high-pressure water injection pipeline through a tee, and the high-pressure stop valve 1 and the high-pressure stop valve 2 are connected in series on the high-pressure gas injection pipeline and the high-pressure water injection pipeline, respectively, which can facilitate the quick switching of the gas injection and water injection states, so that pulse water injection and gas injection operations can be performed alternately. A high-pressure water injection pump for pulse water injection operation is connected in series between the water storage tank and the water inlet end of the high-pressure water injection pipeline, which can facilitate the use of the high-pressure water injection pump to pressurize the water, and then the high-pressure water can be used to efficiently impact the coal seam to obtain a crack with better permeability enhancement effect and a larger extension range. A high-pressure gas injection pump for pulse gas injection operation is connected in series between the gas storage tank and the air inlet end of the high-pressure gas injection pipeline, which can facilitate the use of the high-pressure gas injection pump to pressurize the gas, and then the high-pressure gas can be used to efficiently impact the coal seam, so as to fully solve the water lock effect generated after water injection, which is conducive to promoting the migration of gas in coal.

[0030] The utility model can pre-crack the coal body by pulsating and cyclically injecting high-pressure water into the coal seam, while displacing CH4 in the nano-scale pores, and can remove the "water lock" effect by pulsating and cyclically injecting air to fully drive the migration of multiphase media. The system can improve the problem of the fracture channel being blocked by coal particles due to the limited pressure of a single injection by means of pulsed water and gas injection. At the same time, the fracture channel generated by a single water and gas injection can be further extended by means of cyclic pulsed water and gas injection, so that the fracture forms a network channel that is more conducive to gas migration.

[0031] The system has simple equipment requirements and high gas displacement efficiency. It can effectively eliminate the water lock effect caused by hydraulic displacement. It is especially suitable for coal seams with high adsorption that are difficult to displace gas by water injection. It can provide important technical support for the efficient extraction of coal gas.

Claims

1. A system for displacing coal seam gas by pulsating and cyclically alternating water and gas injection along the layer holes, comprising a high-pressure gas pulsating injection unit and a high-pressure pulsating water injection unit, characterized in that: It also includes displacement operation units; The high-pressure gas pulsation injection unit comprises a gas storage tank (8), a high-pressure gas injection pump (7) and a high-pressure stop valve (6); the gas storage tank (8) is filled with gas; the high-pressure gas injection pump (7) is used for pulse gas injection operation, the inlet end of which is connected to the gas outlet of the gas storage tank (8) through a high-pressure gas supply pipeline (13), and the outlet end of which is connected to the gas inlet end of the high-pressure gas injection pipeline (5); the high-pressure stop valve (6) is connected in series to the high-pressure gas injection pipeline (5); The high-pressure pulsating water injection unit comprises a water storage tank (10), a high-pressure water injection pump (9) and a second high-pressure stop valve (16); the water storage tank (10) is filled with water; the high-pressure water injection pump (9) is used for pulse water injection operation, the inlet end of which is connected to the water outlet of the water storage tank (10) through a high-pressure water supply pipeline (14), and the outlet end of which is connected to the water inlet end of the high-pressure water injection pipeline (15); the second high-pressure stop valve (16) is connected in series to the high-pressure water injection pipeline (15); The displacement operation unit comprises a tee (17), a displacement operation pipeline (18), a drainage pipeline (19), a high-pressure stop valve (20) and a high-pressure capsule (12); the two inlet ends of the tee (17) are respectively connected to the gas outlet end of the high-pressure gas injection pipeline (5) and the water outlet end of the high-pressure water injection pipeline (15); the inlet end of the displacement operation pipeline (18) is connected to the outlet end of the tee (17), and its operation section extends into the borehole (3); the drainage pipeline (19) is connected to one side of the outlet end of the displacement operation pipeline (18); the high-pressure stop valve (20) is connected in series to the drainage pipeline (19); two high-pressure capsules (12) are spaced apart and mounted on the outside of the outlet end of the displacement operation pipeline (18), and the gap between the displacement operation pipeline (18) and the borehole (3) wall is sealed; and a fracturing outlet is opened in the displacement operation pipeline (18) between the two high-pressure capsules (12).

2. A system for displacing coal seam gas by pulsating and cyclically alternating water and gas injection in layers according to claim 1, characterized in that: The high-pressure gas pulsation injection unit further comprises a high-pressure stop valve four (21), and the high-pressure stop valve four (21) is connected in series to the high-pressure gas supply pipeline (13).

3. The system for displacing coal seam gas by pulsating and cyclically alternating water and gas injection in the layer holes according to claim 1 is characterized in that: The high-pressure pulsating water injection unit also includes a high-pressure stop valve five (22), and the high-pressure stop valve five (22) is connected in series to the high-pressure water supply pipeline (14).

4. A system for displacing coal seam gas by pulsating and cyclically alternating water and gas injection in layers according to claim 3, characterized in that: The working pressure range of the high-pressure gas injection pump (7) is 0-10 MPa.

5. A system for displacing coal seam gas by pulsating and cyclically alternating water and gas injection in layers according to claim 4, characterized in that: The working pressure range of the high-pressure water injection pump (9) is 10-30 MPa.

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