Inclined coal seam gas underground area extraction method

Abstract

The invention provides an inclined coal seam gas underground area extraction method, which comprises the following steps of: 1, dividing an extraction area into a first section and a second section according to the inclination angle of a coal seam in the extraction area and the sequence of coal mining sections, and enabling the extraction sequence of the coal mining area in the first section to be earlier than that of the coal mining area in the second section; secondly, a first extraction roadway is excavated below the junction of the first section and the second section, extraction holes are formed in the first extraction roadway in the first section and the second section respectively, and gas in the first section and gas in the second section are extracted at the same time; and 3, after extraction is completed, coal seams of the multiple coal mining areas in the first section are mined in sequence, meanwhile, a second extraction roadway is excavated in the side, away from the first section, of the second section, and supplementary extraction is conducted on the second section. By means of the technical scheme, the problem that in the prior art, the coal seam mining efficiency is low can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining, and in particular to a method for extracting gas from an inclined coal seam underground. Background Art

[0002] At present, before coal mining, it is necessary to extract the gas in the coal mining area to prevent safety accidents such as gas explosions during coal mining.

[0003] The existing extraction methods are generally based on ground drilling pre-extraction and underground drilling negative pressure extraction. The ground drilling pre-extraction method is only for the preparation mining area with a long extraction time, and has a large extraction impact range, but there are problems such as a long construction period and high implementation cost, and there is still room for improvement in extraction efficiency. The underground negative pressure extraction method in coal mines generally requires the development of a dedicated gas extraction rock tunnel, and the use of through-layer drilling and along-layer drilling methods to densely arrange holes.

[0004] When negative pressure extraction is carried out underground in coal mines, gas extraction is usually carried out in a certain mining section before mining. Before extraction, drilling and fracturing are required in the mining section in the tunnel. After the mining work in the mining section is completed, gas extraction and coal seam excavation are repeated in the next mining section. However, underground fracturing equipment is frequently moved, and transportation and placement are limited by tunnel space. The installation preparation cycle is long, and the implementation of fracturing projects is difficult. The efficiency of mining and excavation is low, which affects the mining progress of coal seams. Summary of the invention

[0005] The present invention provides a method for extracting gas from an inclined coal seam underground, so as to solve the problem of low coal seam mining efficiency in the prior art.

[0006] The present invention provides a method for extracting gas from an inclined coal seam underground area. The method for extracting gas from an inclined coal seam underground area comprises:

[0007] Step 1: According to the inclination angle of the coal seam in the mining area and the order of the coal mining sections, the mining area is divided into a first section and a second section. The first section and the second section both include multiple coal mining areas. In the height direction, the first section is located above the second section. The mining order of the coal mining area in the first section is earlier than that of the coal mining area in the second section.

[0008] Step 2: excavating a first extraction tunnel below the junction of the first section and the second section, opening extraction holes in the first extraction tunnel toward the first section and the second section respectively, and extracting gas in the first section and the second section at the same time;

[0009] Step three, after the extraction is completed, the coal seams in multiple mining areas in the first section are mined in sequence. At the same time, a second extraction tunnel is excavated on the side of the second section away from the first section, and a hole is drilled into the second section through the second extraction tunnel to perform additional extraction on the second section.

[0010] Furthermore, along the inclination of the coal seam, the first section and the second section extend to the same length, and the first extraction tunnel is located in the middle of the mining area.

[0011] Furthermore, a plurality of extraction holes are provided, each of which has an inclined section and an extension section which are interconnected. The inclined section extends from the inner wall of the first extraction tunnel to the top of the coal seam. The inclined section and the extension section have an angle. The extension section is arranged parallel to the coal seam. The plurality of extraction holes are evenly distributed along the extension direction of the first extraction tunnel.

[0012] Furthermore, the projection of the inclined section in the height direction does not overlap with the first extraction tunnel, and the coal seam above the first extraction tunnel forms a protection area.

[0013] Furthermore, before gas extraction is performed, step two also includes: obtaining a designed half-fracture length, and hydraulically fracturing the extraction hole according to the designed half-fracture length.

[0014] Furthermore, the spacing between two adjacent extension sections is twice the designed fracturing half-fracture length.

[0015] Furthermore, when the extraction holes are opened in the first extraction tunnel, the extraction holes are opened sequentially along the extension direction of the first extraction tunnel. After each extraction hole is opened, the extraction hole is hydraulically fractured, and the next extraction hole is opened after the hydraulic fracturing is completed.

[0016] Furthermore, before performing step three, step two also includes: opening a supplementary mining hole in the first extraction tunnel to supplement the protected area.

[0017] Furthermore, before supplementary extraction of the second section, step three also includes: opening a drainage hole in the second extraction tunnel, the drainage hole is connected to the extraction hole, and after drainage, the drainage hole is used to supplement the extraction of gas in the second coal mining section.

[0018] Furthermore, the method for extracting gas from an inclined coal seam underground area also includes step four: mining the second section after supplementary extraction of the second section; and extracting gas from the goaf of the first section and the second section through the extraction holes of the first section and the second section after the first section and the second section are mined.

[0019] By applying the technical solution of the present invention, the gas in multiple coal mining areas can be centrally extracted through the first extraction tunnel at the same time. The extraction holes cover the gas source area of ​​the coal tunnel strips and the gas source area of ​​the mining area in each coal mining area. The engineering and equipment are centrally arranged in one tunnel, avoiding the arrangement of gas extraction tunnels in each coal mining area in the mining area, and mining is carried out after the gas extraction of a certain coal mining area is completed, avoiding frequent relocation of equipment, reducing frequent switching of water supply, power supply, ventilation and gas extraction monitoring, improving engineering operation efficiency, reducing tunnel management costs, and realizing intensive and factory-based efficient gas extraction in the limited space of coal mines. Mining is carried out immediately after the extraction of the first section is completed, and supplementary mining is carried out in the second section through the second extraction tunnel at the same time, which can optimize the use of the limited gas pre-extraction window period, ensure the normal mining and excavation succession of the working face, and improve the mining efficiency of the coal seam. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 A schematic diagram of a mining area provided by the present invention is shown;

[0022] Figure 2 A partial schematic diagram of a first extraction tunnel provided by the present invention is shown;

[0023] Figure 3 A schematic diagram showing the arrangement of the extraction holes provided by the present invention in the extraction area;

[0024] Figure 4 A cross-sectional schematic diagram showing the arrangement of the extraction holes provided by the present invention in the extraction area;

[0025] Figure 5 A cross-sectional schematic diagram shows the arrangement of supplementary production holes provided by the present invention in a production area.

[0026] The above drawings include the following reference numerals:

[0027] 100. Mining area;

[0028] 110, first section; 101, first coal mining section; 102, second coal mining section; 103, third coal mining section;

[0029] 120, the second section; 104, the fourth coal mining section; 105, the fifth coal mining section; 106, the sixth coal mining section;

[0030] 200, first extraction tunnel; 210, drilling site; 220, connecting pipe; 230, pumping station; 240, water tank;

[0031] 300, the second extraction tunnel;

[0032] 400, extraction hole; 410, inclined section; 420, extension section;

[0033] 500, supplementary mining hole;

[0034] 600. Drainage hole. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] like Figures 1 to 5 As shown, an embodiment of the present invention provides a method for extracting gas from an inclined coal seam underground area, and the method for extracting gas from an inclined coal seam underground area includes:

[0037] Step 1: According to the inclination angle of the coal seam in the mining area 100 and the order of coal mining sections, the mining area 100 is divided into a first section 110 and a second section 120. The first section 110 and the second section 120 both include a plurality of coal mining areas. In the height direction, the first section 110 is located above the second section 120. The mining order of the coal mining area in the first section 110 is earlier than that of the coal mining area in the second section 120.

[0038] Step 2: excavating a first extraction tunnel 200 below the junction of the first section 110 and the second section 120, opening extraction holes 400 in the first extraction tunnel 200 toward the first section 110 and the second section 120, and extracting gas in the first section 110 and the second section 120 at the same time;

[0039] Step three, after the extraction is completed, the coal seams in multiple mining areas in the first section 110 are mined in sequence. At the same time, a second extraction tunnel 300 is excavated on the side of the second section 120 away from the first section 110, and a hole is drilled into the second section 120 from the second extraction tunnel 300 to perform additional extraction on the second section 120.

[0040] Reference Figure 1 As shown, the x direction is the coal seam inclination, and the y direction is the coal seam strike, which is also the extension direction of the first extraction tunnel 200 and the second extraction tunnel 300 .

[0041] By applying the technical solution of the present invention, the gas in multiple coal mining areas can be centrally extracted through the first extraction tunnel 200 at the same time. The extraction holes 400 cover the coal tunnel strip gas source area and the recovery area gas source area of ​​each coal mining area. The engineering and equipment are centrally arranged in one tunnel, avoiding the arrangement of gas extraction tunnels in each coal mining area within the mining area 100, and mining after the gas extraction in a certain coal mining area is completed, avoiding frequent relocation of equipment, reducing frequent switching of water supply, power supply, ventilation and gas extraction monitoring, improving engineering operation efficiency, reducing tunnel management costs, and realizing intensive and factory-based efficient gas extraction in the limited space of coal mines. In addition, since coal seams usually have a certain inclination, water accumulation is easy to occur in the extraction holes 400 located in the lower coal mining area, and the gas extraction effect in the lower coal mining area is poor. The present application divides the mining area 100 into a first section 110 and a second section 120 according to the mining sequence and the inclination of the coal seam. After the extraction of the first section 110 is completed, mining is carried out immediately, and at the same time, the second section 120 is supplemented by mining through the second extraction tunnel 300. This can optimize the use of the limited gas pre-extraction window period, ensure the normal mining and excavation succession of the working face, and improve the mining efficiency of the coal seam.

[0042] Specifically, along the inclination of the coal seam, the first section 110 and the second section 120 extend to the same length, and the first extraction tunnel 200 is located in the middle of the mining area 100. Through the above arrangement, when drilling the extraction hole 400, the lengths of the extraction holes 400 in the first section 110 and the second section 120 can be the same, which prevents the need to drill an excessively long extraction hole 400 in a certain section and extract a larger area, thereby ensuring the extraction efficiency of the first section 110 and the second section 120.

[0043] Furthermore, a plurality of extraction holes 400 are provided, and the extraction holes 400 have an inclined section 410 and an extension section 420 that are interconnected, the inclined section 410 extends from the inner wall of the first extraction tunnel 200 to the upper side of the coal seam, the inclined section 410 and the extension section 420 have an angle, the extension section 420 is arranged parallel to the coal seam, and the plurality of extraction holes 400 are evenly distributed along the extension direction of the first extraction tunnel 200. Through the above arrangement, the extraction holes 400 can evenly extract the gas in the coal seam during extraction, prevent the phenomenon of mismatch between the extraction pump and the extraction amount, and ensure the extraction efficiency.

[0044] Specifically, the projection of the inclined section 410 in the height direction does not overlap with the first extraction tunnel 200, and a protection area is formed in the coal seam above the first extraction tunnel 200. Since the fracturing of the extraction hole 400 drilled during the extraction process will cause certain damage to the coal seam, the formation of the protection area can ensure the stability of the coal seam above the first extraction tunnel 200, prevent the first extraction tunnel 200 from becoming unstable, and ensure production safety.

[0045] Similarly, there is a protection area above the second extraction tunnel 300 .

[0046] Before gas extraction, step 2 also includes: obtaining the designed half-fracture length, and hydraulically fracturing the extraction hole 400 according to the designed half-fracture length. Through hydraulic fracturing, the permeability of the coal seam can be improved, which facilitates the release of gas from the coal seam. The specific method of obtaining the designed half-fracture length can be selected from production capacity simulation software and fracturing crack design simulation software.

[0047] Specifically, the distance between two adjacent extension sections 420 is twice the designed fracturing half-slit length. The above arrangement can prevent the fracturing half-slit length of one extraction hole 400 from being too long, thereby affecting the normal extraction of the other extraction holes 400, thereby ensuring the extraction efficiency.

[0048] In the present application, when the extraction holes 400 are opened in the first extraction tunnel 200, the extraction holes 400 are opened sequentially along the extension direction of the first extraction tunnel 200. After each extraction hole 400 is opened, the extraction hole 400 is hydraulically fractured, and the next extraction hole 400 is opened after the hydraulic fracturing is completed. Through the above arrangement, it can be ensured that the extraction hole 400 is hydraulically fractured immediately after the construction is completed, and the extraction hole 400 is prevented from collapsing.

[0049] Before step 3, step 2 also includes: opening a supplementary mining hole 500 in the first extraction tunnel 200 to supplement mining in the protection area. Through the above arrangement, the shorter supplementary mining hole 500 does not undergo fracturing, which causes less damage to the stability of the tunnel surrounding rock. While maintaining the stability of the first extraction tunnel 200 within a controllable range, the gas in the coal seam can be extracted as much as possible.

[0050] Similarly, after the supplementary extraction in the second section 120 is completed, a supplementary extraction hole 500 is also opened above the second extraction tunnel 300 to extract the protection area of ​​the second extraction tunnel 300 .

[0051] Specifically, before supplementary extraction of the second section 120, step three further includes opening a drainage hole 600 in the second extraction tunnel 300, the drainage hole 600 is connected to the extraction hole 400, and after drainage, the drainage hole 600 is used to supplement the extraction of gas in the second section 120. Through the above arrangement, the accumulated water in the extraction hole 400 in the second section 120 can be discharged through the drainage hole 600, and the extraction hole 400 can be used for supplementary extraction of gas through the drainage hole 600, without the need for additional drilling, thereby ensuring extraction efficiency.

[0052] Furthermore, the method for extracting gas from an inclined coal seam underground area also includes step 4: after supplementary extraction of the second section 120, the second section 120 is mined, and after the first section 110 and the second section 120 are mined, the goaf of the first section 110 and the second section 120 is extracted through the extraction holes 400 of the first section 110 and the second section 120. During the mining process, the gas in the coal seam and its adjacent layers is depressurized and released, and gas accumulates in the goaf, which can easily cause abnormal gas outflow or corner gas over-limit. During the mining process of the section coal seam, the extraction hole 400 used for pre-extraction of the section coal seam gas can continue to be used as a gas extraction hole in the goaf, achieving multiple uses of one hole.

[0053] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] S1: Planning the mining area 100.

[0055] See also Figure 1 The mining area 100 of the embodiment of the present application has a length of 1000m along the strike of the coal seam and a length of 1200m along the dip of the coal seam. It is designed to be divided into 6 coal mining areas, including the first coal mining section 101, the second coal mining section 102, the third coal mining section 103, the fourth coal mining section 104, the fifth coal mining section 105 and the sixth coal mining section 106. The first coal mining section 101, the second coal mining section 102 and the third coal mining section 103 form a first section 110, the fourth coal mining section 104, the fifth coal mining section 105 and the sixth coal mining section 106 form a second section 120, and the dip length of a single coal mining area is 200m.

[0056] S2: Excavating the first extraction tunnel 200.

[0057] See also Figure 2 and Figure 3 The first extraction tunnel is excavated in the stable bottom rock layer at the junction of the third coal mining section 103 and the fourth coal mining section 104. In the height direction, the distance between the first extraction tunnel 200 and the coal seam is 10m. Drilling sites 210 are respectively set up on the left and right sides of the first extraction tunnel 200. The drilling sites 210 are used for drilling and fracturing of extraction holes 400. The drilling orientation is perpendicular to the orientation of the first extraction tunnel 200. Each drilling site 210 is arranged with 3 directional long boreholes, and the drilling site arrangement spacing is 3 times the drilling spacing. A connecting pipe 220, a pump station 230 and a water tank 240 are arranged in the first extraction tunnel 200. The connecting pipe 220 connects multiple drilling sites 210 to centrally transport gas. A soft water tank is selected for the water tank 240. The water supply capacity of the water tank 240 is greater than the construction displacement of the pump station 230 by 3m 3 / min.

[0058] S3: Opening a drainage hole 400 and performing hydraulic fracturing on the drainage hole 400.

[0059] See also Figure 3 and Figure 4 As shown, in this example, the strength coefficient of the target coal seam f is less than 1.0, and the extraction hole 400 is arranged in the roof rock layer adjacent to the coal seam, and the distance from the coal seam is controlled within 2m. In this example, the angle between the azimuth of the first extraction tunnel 200 and the azimuth of the maximum horizontal principal stress in the mining area 100 is 15°, so the angle between the azimuth of the designed extraction hole 400 and the azimuth of the minimum horizontal principal stress in the mining area is also maintained at 15°, that is, the extraction hole 400 is arranged perpendicular to the first extraction tunnel 200. In this example, the coal seam inclination is 8°, and the extraction hole 400 in the first section 110 is an upward hole, which keeps consistent with the coal seam inclination after entering the target layer; the extraction hole 400 in the second section 120 is a downward hole, which keeps consistent with the coal seam inclination after entering the target layer; the extraction hole 400 in the first section 110 is designed to have a length of 600m, covering 3 coal mining areas, with a fracturing protection area of ​​80m reserved near the first section 110; the extraction hole 400 in the second section 120 is designed to have a length of 470m, covering 3 coal mining areas, with a fracturing protection area of ​​70m reserved near the second section 120.

[0060] Drain holes 400 are drilled in sequence along the extension direction of the first extraction tunnel 200. After drilling one extraction hole 400, hydraulic fracturing is performed on it. The gas extraction capacity prediction software and the fracturing crack design software are used for comprehensive simulation to optimize the fracturing section spacing to be 30m, the half-length of the fracturing crack to be 45m, and the fracturing construction displacement to be 3m 3 / min, the single-stage fracturing time is 110min. After the extraction hole 400 is constructed on one side of the first extraction tunnel 200, the other side is constructed.

[0061] S4: Connect the fracturing-completed extraction hole 400 to the gas extraction system to perform negative pressure gas extraction.

[0062] After fracturing the extraction hole 400, wait until the pressure in the hole drops below the blowout limit pressure of 0.5 MPa, connect the gas extraction system through the connecting pipe 220, slowly open the valve, perform steam-water separation and negative pressure extraction, and analyze the remaining gas content and gas pressure based on the gas concentration, flow, pressure and temperature parameters in the gas extraction pipeline monitored online in real time, and evaluate the gas pre-extraction effect of the gas source areas in each coal mining area.

[0063] S5: Reference Figure 5 As shown, a plurality of supplementary extraction holes 500 are opened on the top plate of the first extraction tunnel 200, and the protection area of ​​the first extraction tunnel 200 is supplementarily extracted in combination with the gas extraction measure of hydraulic punching.

[0064] S6: Coal mining is carried out in sequence in the order of the first coal mining section 101, the second coal mining section 102, and the third coal mining section 103. At the same time, a second extraction tunnel 300 is excavated at the boundary of the sixth coal mining section 106, and a drainage hole 600 is opened in the protection area of ​​the second extraction tunnel 300 toward the extraction hole 400 in the second section 120. An automatic water discharge device is installed at the hole mouth. When the water level in the borehole rises to the limit, the valve opens to drain water, thereby realizing gas extraction from the second section 120 to the drainage hole 600.

[0065] S7: A plurality of supplementary mining holes 500 are opened on the roof of the second extraction tunnel 300 , and the protection area of ​​the second extraction tunnel 300 is supplemented with mining in combination with gas extraction measures such as hydraulic punching, and the coal seam in the second section 120 is mined.

[0066] S8: After the coal seam in the mining area 100 is mined, the gas accumulated in the goaf is continuously extracted using the extraction holes 400.

[0067] After the gas extraction meets the standards, mining begins at the working face. During the mining process, the gas in the coal seam and its adjacent layers is depressurized and released, and gas accumulates in the goaf, which can easily cause abnormal gas outburst or excessive gas in the corners. Gas extraction in the goaf continues through extraction hole 400.

[0068] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0069] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0070] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0071] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0072] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for extracting gas from an inclined coal seam underground, characterized in that: The method for extracting gas from an underground inclined coal seam includes: Step 1: According to the inclination angle of the coal seam in the mining area (100) and the order of coal mining sections, the mining area (100) is divided into a first section (110) and a second section (120), wherein the first section (110) and the second section (120) each include a plurality of coal mining areas, and along the height direction, the first section (110) is located above the second section (120), and the mining order of the coal mining area in the first section (110) is earlier than that of the coal mining area in the second section (120); Step 2: excavating a first extraction tunnel (200) below the junction of the first section (110) and the second section (120), opening extraction holes (400) in the first extraction tunnel (200) towards the first section (110) and the second section (120), respectively, and extracting gas in the first section (110) and the second section (120) at the same time; Step three, after the extraction is completed, the coal seams in the multiple mining areas in the first section (110) are mined in sequence, and at the same time, a second extraction tunnel (300) is excavated on the side of the second section (120) away from the first section (110), and a hole is drilled into the second section (120) through the second extraction tunnel (300) to supplement the extraction of the second section (120).

2. The method for extracting gas from an inclined coal seam underground according to claim 1, characterized in that: Along the inclination of the coal seam, the first section (110) and the second section (120) extend over the same length, and the first extraction tunnel (200) is located in the middle of the mining area (100).

3. The method for extracting gas from an inclined coal seam underground according to claim 1, characterized in that: A plurality of extraction holes (400) are provided, and each extraction hole (400) has an inclined section (410) and an extension section (420) that are interconnected. The inclined section (410) extends from the inner wall of the first extraction tunnel (200) toward the top of the coal seam. An angle is formed between the inclined section (410) and the extension section (420). The extension section (420) is arranged parallel to the coal seam. Along the extension direction of the first extraction tunnel (200), the plurality of extraction holes (400) are evenly distributed.

4. The method for extracting gas from an inclined coal seam underground according to claim 3, characterized in that: The projection of the inclined section (410) in the height direction does not overlap with the first extraction tunnel (200), and the coal seam above the first extraction tunnel (200) forms a protection area.

5. The method for extracting gas from an inclined coal seam underground according to claim 3, characterized in that: Before gas extraction, the step 2 further includes: The designed half-fracture length is obtained, and hydraulic fracturing is performed on the extraction hole (400) according to the designed half-fracture length.

6. The method for underground regional extraction of inclined coal seam gas according to claim 5, characterized in that: The distance between two adjacent extension sections (420) is twice the designed fracturing half-fracture length.

7. The method for underground regional extraction of inclined coal seam gas according to claim 5, characterized in that: When the extraction holes (400) are opened in the first extraction tunnel (200), the extraction holes (400) are opened sequentially along the extension direction of the first extraction tunnel (200). After each extraction hole (400) is opened, the extraction hole (400) is hydraulically fractured, and the next extraction hole (400) is opened after the hydraulic fracturing is completed.

8. The method for extracting gas from an inclined coal seam underground according to claim 4, characterized in that: Before performing step 3, step 2 further includes: A supplementary extraction hole (500) is opened in the first extraction tunnel (200) to supplement the extraction in the protection area.

9. The method for extracting gas from an inclined coal seam underground according to claim 1, characterized in that: Before supplementary extraction is performed on the second section (120), the step three further comprises: A drainage hole (600) is opened in the second extraction tunnel (300), and the drainage hole (600) is connected to the extraction hole (400). After drainage, the drainage hole (600) is used to supplement the gas in the second section (120).

10. The method for underground regional extraction of inclined coal seam gas according to claim 1, characterized in that: The method for extracting gas from an underground inclined coal seam also includes step 4: After supplementary extraction of the second section (120), the second section (120) is mined; After the first section (110) and the second section (120) are mined, gas is extracted from the goaf of the first section (110) and the second section (120) through the extraction holes (400) of the first section (110) and the second section (120).

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