Coal seam gas extraction structure based on rock fracture environment

Abstract

This utility model discloses a coal seam gas extraction structure based on a rock fracture environment, belonging to the field of gas extraction. The structure includes an extraction pipe extending into a grouting chamber equipped with at least two sets of filling mechanisms. These two sets of filling mechanisms are respectively located on both sides of the fracture and sealed with the grouting chamber to form a working cavity. The grouting chamber also contains at least two sets of grouting mechanisms. The outlet end of one grouting mechanism extends into the cavity between the coal seam and the filling mechanism, while the outlet end of the other grouting mechanism extends between the two sets of filling mechanisms. This utility model allows grout to penetrate into the surrounding fractures, forming a high-strength support layer after consolidation. This ensures that the borehole is not affected by the fractures after sealing, preventing borehole cross-cutting or the failure of the negative pressure to reach the coal seam due to fracture interruption of extraction negative pressure, thus preventing borehole abandonment.

Description

Technical Field

[0001] This utility model relates to the field of gas extraction technology, and in particular to a coal seam gas extraction structure based on rock fissure environment. Background Technology

[0002] Longtan Coal Mine is a single-seam mining mine. From 2015 to 2024, gas level assessments were conducted, all of which concluded it was a coal and gas outburst mine. The mine adopted pre-drainage of coal seam gas as a regional outburst prevention measure. Originally, this involved both in-seam (pre-drainage mining face backfill area) and cross-seam (pre-drainage roadway excavation strip). However, the mine has complex geological conditions, with all floor drainage roadways located in Maokou limestone. The fractures between the floor roadways and the coal seam are severely developed. Furthermore, the gas control boreholes used in construction were diverse. Initially, the mine used a "one-plug, one-inject" method to seal the drainage boreholes. However, due to poor sealing airtightness and the inability of the negative pressure from the floor roadway to the coal seam to reach the coal seam, the drilling drainage effect was significantly reduced. The regional outburst prevention measures failed to achieve the expected results, leading to varying degrees of weak areas in the boreholes at each mining face. This created significant safety hazards for subsequent coal roadway excavation and face backfilling.

[0003] Currently, the existing gas drainage borehole sealing technology involves drilling holes in the Maokou limestone during working face construction to form grouting chambers, with the outlet of the grouting chambers contacting the coal seam. However, cracks will be generated in the rock layer, and gas will be generated between the cracks and the coal seam. This gas needs to be extracted. Then, a 16m drainage pipe is inserted, with the first 4m being a screen pipe. A sealing pipe is then inserted, and the borehole opening is filled tightly with filling material to complete the pre-sealing process. Then, a cement slurry made of water and cement is injected into the borehole. The slurry flows out through the grouting pipe and fills the sealing section to complete the sealing process.

[0004] However, this gas extraction borehole sealing technology has the following shortcomings: for rock strata with well-developed fractures, if there are fractures in the borehole, the borehole is easily affected by the fractures after sealing, which may cause the borehole to cross-hole or the negative pressure of extraction to be cut off by the fractures, resulting in the negative pressure not being able to act on the coal seam and the borehole being scrapped. Utility Model Content

[0005] The purpose of this invention is to solve the problem in the prior art where boreholes are strung together or the negative pressure during extraction is cut off by fissures, resulting in the inability of the negative pressure to act on the coal seam and thus causing the borehole to be scrapped. Therefore, this invention proposes a coal seam gas extraction structure based on rock fissure environments.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A coal seam gas extraction structure based on a rock fracture environment includes an extraction pipe extending into a grouting chamber with at least two sets of filling mechanisms. The two sets of filling mechanisms are respectively located on both sides of the fracture and are sealed with the grouting chamber to form a working cavity. The grouting chamber is also equipped with at least two sets of grouting mechanisms. The outlet end of one grouting mechanism extends into the cavity between the coal seam and the filling mechanism, and the outlet end of the other grouting mechanism extends between the two sets of filling mechanisms.

[0008] To facilitate subsequent filling of the grouting chamber, the grouting mechanism preferably includes a primary grouting pipe and a secondary grouting pipe.

[0009] To facilitate the sealing or opening of the grouting pipe channel, a gate valve is further provided on the grouting pipe.

[0010] To facilitate the sealing of local chambers in the grouting chamber, the filling mechanism preferably includes a bladder that covers the outside of the grouting pipe and the extraction pipe.

[0011] To improve the extraction effect of the extraction pipe, preferably, a screen pipe is provided at the inlet end of the extraction pipe.

[0012] Furthermore, the length ratio of the screen tube to the extraction tube is 4:1.

[0013] Compared with the prior art, this utility model provides a coal seam gas extraction structure based on rock fracture environment, which has the following beneficial effects:

[0014] 1. This coal seam gas extraction structure based on rock fissure environment can quickly extract gas generated in Maokou limestone or other rock fissures through extraction pipes;

[0015] 2. This coal seam gas extraction structure based on rock fissure environment can be injected into the injection cavity between two sets of bags through the grouting pipe, and at the same time, the grout can penetrate into the surrounding fissures. After consolidation, a high-strength support layer is formed, so that the hole will not be affected by the fissure after sealing. This prevents the phenomenon of borehole cross-hole or the failure of the negative pressure to act on the coal seam due to the interruption of extraction negative pressure by the fissure, which would lead to the failure of the borehole.

[0016] The parts not involved in this device are the same as or can be implemented using existing technologies. This utility model can allow the slurry to penetrate into the surrounding fissures and form a high-strength support layer after consolidation, so that it will not be affected by the fissures after the hole is sealed, preventing the phenomenon of borehole cross-hole or the failure of the negative pressure to act on the coal seam due to the interruption of the extraction negative pressure by the fissure, resulting in the failure of the borehole. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a planar structure for coal seam gas extraction based on a rock fracture environment, as proposed in this utility model.

[0018] Figure 2 This utility model proposes a coal seam gas extraction structure based on rock fracture environment. Figure 1 A schematic diagram of the structure of part A;

[0019] Figure 3 This invention presents a partial structural schematic diagram of a coal seam gas extraction structure based on a rock fracture environment. Figure 1 ;

[0020] Figure 4 This invention presents a partial structural schematic diagram of a coal seam gas extraction structure based on a rock fracture environment. Figure 2 .

[0021] In the diagram: 1. Extraction pipe; 2. Primary grouting pipe; 3. Secondary grouting pipe; 4. Screen pipe; 5. Bag; 6. Gate valve. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0023] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0024] A tiered treatment system for gas drainage boreholes in fractured rock strata comprises six integrated measures: exploration, probing, consolidation, drilling, drainage, and treatment. This systematic approach, involving exploration, probing, consolidation, drilling, drainage, and treatment, firstly, enhances the accuracy of geological exploration through the "exploration" and "probing" steps, providing reliable geological data for subsequent drilling and significantly reducing the risk of borehole deviations or gas leaks due to unclear geological conditions. Secondly, the "consolidation" step, through grouting to solidify fractures, significantly improves the stability and sealing of the rock strata, laying a solid foundation for drilling and gas drainage. Thirdly, the "drilling" step ensures the accuracy and efficiency of drilling operations, providing strong support for subsequent tiered treatment. The "drainage" step, through the selection of sealing and grouting schemes at different levels, allows for flexible responses to different borehole types and fracture development degrees, ensuring optimal airtightness for each borehole. Finally, the "treatment" step implements targeted treatment for abnormal boreholes, effectively improving drainage efficiency and safety. Example

[0025] Reference Figures 1-4 A coal seam gas extraction structure based on rock fissure environment includes an extraction pipe 1, which is connected to a water ring vacuum extraction pump for extracting gas generated in Maokou limestone or other rock fissures. The inlet end of the extraction pipe 1 is equipped with a screen pipe 4, the length of which is 4:1 to the length of the extraction pipe 1. The design of the screen pipe 4 can improve the gas transport efficiency, ensure efficient gas collection, and improve extraction efficiency.

[0026] In the above scheme, the extraction pipe 1 of this device extends into the grouting chamber and is equipped with two sets of filling mechanisms. These two sets of filling mechanisms are respectively located on both sides of the crack and are sealed with the grouting chamber to form a working cavity. The filling mechanism includes a bag 5, which covers the outside of the grouting pipe and the extraction pipe 1. The bag 5 is made of a wear-resistant flexible polymer material (such as a nano-diffusion expanding agent). After being injected into the grouting chamber, it rapidly expands and fills the cavity, forming a primary sealing barrier. A tensile fiber reinforcement layer is built into the bag 5, which, in conjunction with the primary grouting pipe 2 and the secondary grouting pipe 3, further seals the rock stratum grouting chamber through high-pressure grouting.

[0027] Furthermore, the diameter of the bag 5 is adjusted according to the drilling angle and fracture density. When the angle is <25°, the standard "two plugs and one injection" method is adopted. In complex fracture areas, the method is upgraded to "three plugs and two injections". The number of bags 5 can be increased or decreased as needed. Antistatic rubber or nylon canvas is used on the outer layer of the bag 5 to resist wear. Polyurethane or nano-expansion agent is filled inside. After the reaction, the volume expansion rate is greater than 300%. Cement grout or high-pressure gas can also be filled inside the bag 5.

[0028] Two sets of grouting mechanisms are also installed in the grouting chamber. The outlet end of one grouting mechanism extends into the cavity between the coal seam and the filling mechanism, and the outlet end of the other grouting mechanism extends between the two sets of filling mechanisms. The grouting mechanism includes a primary grouting pipe 2 and a secondary grouting pipe 3. Gate valves 6 are installed on the two sets of grouting pipes. The primary grouting pipe 2 can fill the grouting chamber between the bag 5 and the coal seam with grout. The secondary grouting pipe 3 can pour the grouting cavity between the two sets of bags 5, and at the same time allow the grout to penetrate into the surrounding fissures. After solidification, a high-strength support layer is formed, so that the borehole will not be affected by the fissures after sealing. This prevents borehole cross-holes or the failure of the negative pressure to act on the coal seam due to the interruption of the extraction negative pressure by the fissures, which would lead to the failure of the borehole.

[0029] Based on the borehole type and the degree of fracture development, different methods such as "one-stop-one-injection," "two-stop-one-injection," and "three-stop-two-injection" can be selected to ensure the airtightness of the extraction borehole. "One-stop-one-injection" is suitable for boreholes with fewer fractures, relatively intact rock strata, and a drilling inclination angle >25°. A single sealing material is used to seal the area around the borehole, followed by the injection of a curing material for solidification, ensuring the borehole's airtightness. "Two-stop-one-injection" is suitable for boreholes with fewer fractures, relatively intact rock strata, and a drilling inclination angle less than 25°. Two layers of sealing material are used to seal the middle area of ​​the borehole, followed by pressurized grouting to ensure saturation of the grout in low-angle boreholes, enhancing the borehole's airtightness and stability. "Three-stop-two-injection" is suitable for boreholes with extremely complex fracture development and highly fractured rock strata. Three layers of sealing material divide the borehole into multiple areas, and then curing material is injected into different areas to form a multi-layered solidification layer, maximizing the borehole's airtightness and extraction efficiency. This tiered selection method allows for flexible adjustment of sealing and grouting schemes based on different borehole types and fracture development levels, ensuring that each borehole achieves optimal airtightness.

[0030] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A coal seam gas extraction structure based on a rock fracture environment, characterized in that, The system includes a extraction pipe (1), which extends into the grouting chamber and is equipped with at least two sets of filling mechanisms. The two sets of filling mechanisms are respectively located on both sides of the crack and are sealed with the grouting chamber to form a working cavity. The grouting chamber is also equipped with at least two sets of grouting mechanisms. The outlet end of one grouting mechanism extends into the cavity between the coal seam and the filling mechanism, and the outlet end of the other grouting mechanism extends between the two sets of filling mechanisms.

2. The coal seam gas extraction structure based on rock fracture environment according to claim 1, characterized in that, The grouting mechanism includes a primary grouting pipe (2) and a secondary grouting pipe (3).

3. A coal seam gas extraction structure based on a rock fracture environment according to claim 2, characterized in that, A gate valve (6) is installed on the grouting pipe.

4. A coal seam gas extraction structure based on a rock fracture environment according to claim 1, characterized in that, The filling mechanism includes a bladder (5) that covers the outside of the grouting pipe and the extraction pipe (1).

5. A coal seam gas extraction structure based on a rock fracture environment according to claim 4, characterized in that, A screen (4) is installed at the inlet end of the extraction pipe (1).

6. A coal seam gas extraction structure based on a rock fracture environment according to claim 5, characterized in that, The length ratio of the screen tube (4) to the extraction tube (1) is 4:1.

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