Drilling and sealing device for coal seam gas extraction

Abstract

The utility model discloses a hole drilling and sealing device for coal seam gas extraction. The hole drilling and sealing device comprises a first packer, a second packer, a grouting pipe, a slurry return pipe, a gas extraction pipe, a pressure ventilation pipe, an expansion device and a pressure applying device, firstly, a sealed grouting space is formed through a first packer and a second packer, primary grouting sealing is conducted in the space through mutual cooperation of a grouting pipe and a grout return pipe, and grout is partially diffused to the periphery of a drill hole; then the pressure ventilation pipe is used for inflating and expanding the expansion device to increase the volume, and the pressure ventilation pipe can apply thrust to the pressure applying device in the expansion process, so that the pressure applying device performs secondary pressure on the slurry in the pressure applying device in a manner of reducing the volume of the sealed grouting space, and the slurry further flows into the multi-scale hole fractures; and finally, the air leakage rate of the drill hole is reduced, and the hole sealing effect is guaranteed.

Description

Technical Field

[0001] The utility model relates to a coal seam gas extraction drilling hole sealing device, belonging to the technical field of underground coal seam gas extraction drilling hole grouting sealing. Background Art

[0002] In order to safely mine high-gas coal seams, the current method of multi-drilling is mainly used to extract and depressurize coal seam gas. The gas extraction process requires the extraction borehole to be sealed, thereby forming a negative pressure environment to extract the desorbed gas that has migrated into the borehole. The sealing effect of the extraction borehole is mostly evaluated from factors such as the sealing method, the selection of sealing materials, and the air leakage rate. The sealing method mostly adopts a two-blocking and one-injection method, and commonly used sealing materials include polyurethane and cement. The air leakage rate is mainly explained by factors such as the degree of integration between the grouting material and the borehole wall, and the distribution of microcracks around the borehole. If the grouting material can fit tightly with the borehole wall and can flow into the microcrack structure of the borehole wall, it can effectively prevent air leakage in the borehole.

[0003] Most of the slurries currently used are fluid. However, when they are injected into the slurry storage area within the two-blocking and one-injection system during the sealing process, the slurry is mainly injected into the cracks around the borehole by relying on external injection pressure. Due to the limited injection pressure, in most cases it is difficult for the slurry to fully flow into the multi-scale pores and cracks. It is impossible to flexibly adjust the length of the grouting area and increase the external applied stress according to the actual size of the borehole and the sealing interval. In many cases, the slurry only diffuses within a limited distance around the borehole, and the problem of borehole air leakage cannot be fundamentally solved, which ultimately leads to sealing failure. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the utility model provides a coal seam gas extraction drilling hole sealing device, which can carry out a secondary test on the grouting area after grouting, so that the slurry can further flow into the multi-scale pores and cracks, thereby increasing the slurry diffusion range, and ultimately reducing the drilling hole leakage rate to ensure the sealing effect.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the utility model is: a coal seam gas extraction drilling hole sealing device, including a first packer, a second packer, a grouting pipe, a slurry return pipe, a gas extraction pipe, a compressed air pipe, an expansion device and a pressure device;

[0006] One end of the gas extraction pipe extends into the borehole, and the first packer and the second packer are installed outside the gas extraction pipe and are located in the borehole, and are used to seal their respective positions, so that the borehole section between the first packer and the second packer forms a sealed grouting space; the second packer is closer to the orifice than the first packer; one end of the grouting pipe and one end of the return grouting pipe both pass through the second packer and extend into the sealed grouting space, the grouting pipe is used to inject slurry into the sealed grouting space, and the return grouting pipe is used to discharge the gas in the sealed grouting space;

[0007] The expansion device and the pressure device are both installed on the outside of the gas extraction pipe in the sealed grouting space, and the pressure device can move axially along the gas extraction pipe, and the pressure device can continuously cover the cross-section of the sealed grouting space during the movement; one end of the compressed air pipe passes through the second packer and is connected to the expansion device, which is used to inject gas into the expansion device to expand it and increase its volume, thereby pushing the pressure device to move toward the first packer to reduce the volume of the sealed grouting space, thereby achieving secondary pressure on the slurry.

[0008] Furthermore, the pressure device is a rigid pressure head with a rubber sealing ring around it, and a slideway is provided outside the gas extraction pipe in the sealed grouting space. The rigid pressure head is installed on the slideway and can move axially along the gas extraction pipe. This structure can better ensure that the pressure device slides along the slideway after being acted upon by the expansion device to apply secondary pressure to the slurry in the sealed grouting space, and finally ensure the sealing effect.

[0009] Furthermore, the expansion device is a high-pressure gas-injection expansion bag, which has a small volume before gas injection and expands after gas injection. This structure is not only easy to install, but also has good structural stability.

[0010] Furthermore, the first packer and the second packer are both water injection packers. This structure is not only convenient for construction, but also has good stability.

[0011] Further, the other end of the grouting pipe and the other end of the return grouting pipe are both equipped with ball valves for controlling the connection and disconnection between the grouting pipe and the return grouting pipe and the sealed grouting space. By setting the ball valve, the pressure in the sealed grouting space can be maintained after the grouting is completed, which is convenient for subsequent secondary pressure application.

[0012] Compared with the prior art, the utility model adopts a combination of a first packer, a second packer, an expansion device and a pressure device. A sealed grouting space is first formed by the first packer and the second packer, and a grouting seal is performed in the space through the cooperation of the grouting pipe and the return grouting pipe, so that part of the slurry is diffused to the surrounding of the borehole; then the expansion device is inflated by the compressed air pipe to increase the volume. During the expansion process, the pressure device can apply thrust to the pressure device, and then the pressure device reduces the volume of the sealed grouting space and applies secondary pressure to the slurry inside it, so that the slurry can further flow into the multi-scale pores and cracks, thereby increasing the diffusion range of the slurry, and ultimately reducing the air leakage rate of the borehole to ensure the sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0014] Figure 2 yes Figure 1 Schematic diagram of the structure of the expansion device and the pressure device.

[0015] In the figure: 1-coal seam; 2-drill hole; 3-second packer; 4-first packer; 5-expansion device; 6-grouting pipe; 7-return slurry pipe; 8-gas extraction pipe; 9-pressure air pipe; 10-pressure device. DETAILED DESCRIPTION

[0016] The utility model will be further described below.

[0017] like Figure 1 As shown, the utility model includes a first packer 4, a second packer 3, a grouting pipe 6, a grout return pipe 7, a gas extraction pipe 8, a compressed air pipe 9, an expansion device 5 and a pressure device 10;

[0018] One end of the gas extraction pipe 8 extends into the borehole 2, and the first packer 4 and the second packer 3 are installed outside the gas extraction pipe 8 and are located in the borehole 2, which are used to seal their respective positions so that the borehole section between the first packer 4 and the second packer 3 forms a sealed grouting space; the second packer 3 is closer to the orifice than the first packer 4; one end of the grouting pipe 6 and one end of the return grouting pipe 7 both pass through the second packer 3 and extend into the sealed grouting space, the grouting pipe 6 is used to inject slurry into the sealed grouting space, and the return grouting pipe 7 is used to discharge the gas in the sealed grouting space; the first packer 4 and the second packer 3 are both water injection packers. This structure is not only convenient for construction, but also has good stability; the other end of the grouting pipe 6 and the other end of the return grouting pipe 7 are equipped with ball valves, which are used to control the connection and disconnection between the grouting pipe 6 and the return grouting pipe 7 and the sealed grouting space respectively. By setting the ball valve, the pressure in the sealed grouting space can be maintained after the grouting is completed, which is convenient for subsequent secondary pressure application.

[0019] like Figure 2 As shown, the expansion device 5 and the pressure device 10 are both installed on the outside of the gas extraction pipe in the sealed grouting space, and the pressure device 10 can move axially along the gas extraction pipe 8, and the pressure device 10 can continuously cover the cross-section of the sealed grouting space during the movement; one end of the compressed air pipe 9 passes through the second packer 3 and is connected to the expansion device 5, which is used to inject air into the expansion device 5 to expand it and increase its volume, thereby pushing the pressure device 10 to move toward the first packer 4 to reduce the volume of the sealed grouting space, thereby realizing a secondary pressure effect on the slurry.

[0020] As an improvement of the present utility model, the pressure device 10 is a rigid pressure head with a rubber sealing ring around it. A slideway is provided on the outside of the gas extraction pipe 8 in the sealed grouting space. The rigid pressure head is mounted on the slideway and can move axially along the gas extraction pipe 8. This structure can better ensure that the pressure device 10 slides along the slideway after being acted upon by the expansion device to apply secondary pressure to the slurry in the sealed grouting space, thereby ultimately ensuring the sealing effect. The expansion device 10 is a high-pressure gas injection expansion bag, which has a small volume before gas injection and expands in volume after gas injection. The use of this structure is not only easy to install, but also has better structural stability.

[0021] When it is necessary to seal the borehole, first install the first packer 4, the second packer 3, the expansion device 5 and the pressure device 10 on the outside of the gas extraction pipe 8, and extend one end of the gas extraction pipe 8 into the borehole 2, then inject water into the first packer 4 and the second packer 3 to expand and seal, form a sealed grouting space between the two packers, and install the grouting pipe 6, the return grouting pipe 7 and the compressed air pipe 9; at this time, open the ball valves on the grouting pipe 6 and the return grouting pipe 7, and inject slurry into the sealed grouting space through the grouting pipe 6. The return grouting pipe 7 continuously discharges the gas in the sealed grouting space during the grouting process, which facilitates the smooth progress of grouting, until the return grouting pipe 7 continuously discharges slurry, indicating that the sealed grouting space is full, and then close the return grouting pipe. The ball valve of pipe 7 continues to grout into the sealed grouting space to maintain pressure, so that the slurry diffuses into the cracks around the borehole. After a period of time, the ball valve of the grouting pipe 6 is closed to stop grouting; then the compressed air pipe 9 is connected to the underground high-pressure air circuit. At this time, the high-pressure airflow inflates the expansion device 5, and the volume of the expansion device 5 begins to expand and increase. During its expansion process, the pressure-applying device is pressurized to push the pressure-applying device 10 to move toward the second packer 4, thereby reducing the sealed grouting space, and then the slurry in the space is subjected to secondary pressure, which further causes the slurry to diffuse and flow into the multi-scale pore cracks, thereby increasing the slurry diffusion range and reducing the borehole leakage rate. After the secondary pressure application, the entire sealing process is completed, and gas extraction can be carried out subsequently through the gas extraction pipe.

[0022] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A coal seam gas extraction drilling and sealing device, characterized in that: It includes a first packer, a second packer, a grouting pipe, a grouting pipe, a gas extraction pipe, a compressed air pipe, an expansion device and a pressure device; One end of the gas extraction pipe extends into the borehole, and the first packer and the second packer are installed outside the gas extraction pipe and are located in the borehole, and are used to seal their respective positions, so that the borehole section between the first packer and the second packer forms a sealed grouting space; the second packer is closer to the orifice than the first packer; one end of the grouting pipe and one end of the return grouting pipe both pass through the second packer and extend into the sealed grouting space, the grouting pipe is used to inject slurry into the sealed grouting space, and the return grouting pipe is used to discharge the gas in the sealed grouting space; The expansion device and the pressure device are both installed on the outside of the gas extraction pipe in the sealed grouting space, and the pressure device can move axially along the gas extraction pipe, and the pressure device can continuously cover the cross-section of the sealed grouting space during the movement; one end of the compressed air pipe passes through the second packer and is connected to the expansion device, which is used to inject gas into the expansion device to expand it and increase its volume, thereby pushing the pressure device to move toward the first packer to reduce the volume of the sealed grouting space, thereby achieving secondary pressure on the slurry.

2. The coal seam gas extraction drilling and sealing device according to claim 1, characterized in that: The pressure device is a rigid pressure head with a rubber sealing ring around it. A slideway is provided outside the gas extraction pipe in the sealed grouting space. The rigid pressure head is installed on the slideway and can move axially along the gas extraction pipe.

3. The coal seam gas extraction drilling and sealing device according to claim 1, characterized in that: The expansion device is a high-pressure gas-injection expansion bag, which has a small volume before gas injection and expands in volume after gas injection.

4. The coal seam gas extraction drilling and sealing device according to claim 1, characterized in that: The first packer and the second packer are both water injection packers.

5. The coal seam gas extraction drilling and sealing device according to claim 1, characterized in that: The other end of the grouting pipe and the other end of the return grouting pipe are both equipped with ball valves for respectively controlling the connection and disconnection between the grouting pipe and the return grouting pipe and the sealed grouting space.

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