A gas rapid extraction method for a combined roadway and district coal seam mining face

Abstract

The application discloses a kind of well roadway combined area coal seam mining working face gas rapid extraction methods: step 1, according to the range of area coal seam mining working face extraction well site layout;Step 2, accurately determine the stratigraphic dip of area coal seam mining working face, if the stratigraphic dip of working face is up-inclined and near horizontal, enter step 3;If the stratigraphic dip of working face is down-inclined, enter step 4;Step 3, the coal seam mining working face with stratigraphic dip of up-inclined and near horizontal is carried out gas extraction construction;Step 4, a down-inclined multi-branch horizontal well along the roof of coal seam mining working face is drilled to carry out staged perforation fracturing, and the coal seam mining working face is carried out gas extraction construction.The method of the application can effectively reduce the number of coal seam mining working face or roof drilling layout, and the extraction efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of gas pre-extraction technology in coal mining areas, specifically to a rapid gas extraction method for coal seam recovery faces in combined mine shaft and roadway areas. Background Technology

[0002] Gas is one of the main factors restricting safe coal mining. Before large-scale mining of a regional coal seam, the gas content must be reduced to a safe standard value; otherwise, serious safety hazards may arise, or gas outbursts or explosions may occur during mining, causing serious loss of life and property. Therefore, efficient and rapid gas extraction from regional coal seam mining faces is crucial and is key to determining whether large-scale tunneling construction can proceed as planned.

[0003] Currently, large-scale gas drainage in regional coal seam mining faces mainly involves a combination of surface L-shaped horizontal wells or multi-branch horizontal wells with staged fracturing technology, and an underground directional borehole combined with staged fracturing technology. The advantage of combining surface L-shaped horizontal wells or multi-branch horizontal wells with staged fracturing technology lies primarily in the larger surface operating space, allowing for large-scale staged fracturing. The fracturing also provides a greater permeability enhancement range in all directions along the regional coal seam mining face, thus reducing the number of boreholes required in the mining face or its roof. However, this technology requires lengthy drainage operations before gas extraction can commence. In addition, the advantage of combining directional drilling along the bedding plane with segmented fracturing technology in coal mines is that it can create negative pressure extraction conditions underground after fracturing, allowing gas extraction work to be carried out without waiting for a long period of drainage construction. However, this technology is limited by the small underground working space, making it difficult to implement large-scale segmented fracturing. The permeability enhancement range of fracturing in all directions along the regional coal seam mining face is small. Therefore, it is necessary to appropriately increase the number of boreholes in the regional coal seam mining face or its roof.

[0004] To address the shortcomings of existing gas extraction methods in regional coal seam mining faces, it is urgent to research an efficient method for implementing gas extraction in regional coal seam mining faces to ensure safe and efficient tunneling operations. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid gas extraction method for coal seam longwall mining faces in combined mine and roadway areas, so as to solve the problems of low efficiency and the need to increase the number of boreholes in existing gas extraction methods.

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

[0007] A method for rapid gas extraction in a coal seam longwall face with combined mine and tunnel operations includes the following steps:

[0008] Step 1: Based on the range of the regional coal seam mining face, the well locations are laid out so that the well trajectories drilled at the laid out well locations can completely cover the entire working face range.

[0009] Step 2: Accurately determine the dip angle of the strata in the regional coal seam mining face. If the dip angle of the strata in the working face is updip or near-horizontal, proceed to Step 3; if the dip angle of the strata in the working face is downdip, proceed to Step 4.

[0010] Step 3 involves gas drainage operations in coal seam longwall faces with updip and near-horizontal dip angles, specifically including the following steps:

[0011] Step 31: Drill an upward-inclined multi-branch horizontal well along the roof of the coal seam mining face from the ground. The well is designed as follows: a vertical section, a roof inclined section, and a roof inclined section. The upward-inclined multi-branch horizontal well includes three branch holes composed of the roof inclined section and the roof inclined section. The three branch holes share a vertical section.

[0012] Step 32: Drill a downward-sloping multi-branch horizontal well along the coal seam mining face from the surface. The well is designed as follows: a vertical section, a coal seam sloping section, and a coal seam downward-sloping section. The downward-sloping multi-branch horizontal well includes two branch holes composed of the coal seam sloping section and the coal seam downward-sloping section. The two branch holes share a vertical section, which is shared with the vertical section in Step 31. The trajectories of the two branch holes are located below the midpoints of the pairwise trajectories of the three branch holes of the upward-sloping multi-branch horizontal well.

[0013] Step 33: Perform segmented perforation fracturing on the three branch holes of the inclined section on the roof in sequence to select the fracturing section; perform segmented perforation fracturing according to the designed perforation points; the direction of the perforation is perpendicular to the coal seam roof and a certain fan-shaped area on the left and right sides of the branch holes of the inclined section on the roof.

[0014] Step 4: For a coal seam mining face with a downward dip angle, drill a downward dip multi-branch horizontal well along the roof of the coal seam mining face from the surface. The horizontal well is designed as follows: vertical section, roof inclined section, and roof downward dip section. The roof of the coal seam mining face The downsloping multi-branch horizontal well consists of three branch holes, each consisting of a roof inclined section and a roof downsloping section. The three branch holes share a single vertical section. The roof downsloping section is subjected to segmented perforation fracturing, and gas drainage is carried out at the coal seam mining face.

[0015] Furthermore, step 31 specifically includes the following operations:

[0016] The vertical well section is drilled to 10-15m into the bedrock, a steel casing is installed, and mud is used for positive circulation cementing and returned to the surface; the roof inclined well section is drilled to the designed landing point on the roof, a steel casing is installed, and mud is used for positive circulation cementing and returned to the surface; the roof inclined well section is drilled through the tunnel, a steel casing is installed, and mud is used for positive circulation cementing and returned to the surface.

[0017] Furthermore, in step 31, the specific implementation method for cementing the inclined section on the top plate is as follows: the casing is lowered from one side of the tunnel to the other side. For the casing section located within the tunnel width, Marlite is wrapped around the outer wall of the casing section. At the ground, the casing is slowly lifted using the drilling rig lifting system. Simultaneously, the Marlite wrapped around the outer wall of the casing is triggered sequentially from top to bottom to form a Marlite filling section. A 1m length is reserved in the tunnel at the end of the lowered casing. Then, multiple thin tubes are evenly inserted along the outer wall of the casing. The thin tubes pass through the Marlite filling section. Pure cement slurry is injected into each thin tube at the same time to form a pure cement filling section. After the pure cement slurry has set for 48 hours, pure cement slurry positive circulation cementing is carried out at the ground with the help of a staged hoop.

[0018] Furthermore, in step 31, the spacing between each branch hole is 60~70m.

[0019] Furthermore, in step 32, the vertical well section is the same as the vertical well section drilled in step 1; the coal seam inclined well section is drilled to the designed landing point of the coal seam, and a steel casing is installed, with mud circulating back to the top of the coal seam inclined well section; the coal seam downward inclined well section is drilled through the roadway, and a combination of pressure-resistant non-steel screen pipe and pressure-resistant non-steel casing is installed, with the pressure-resistant non-steel screen pipe not cemented, and the pressure-resistant non-steel casing cemented.

[0020] Furthermore, in step 32, the spacing between the branch holes of the downward-sloping multi-branch horizontal well is 60~70m.

[0021] Furthermore, in step 32, the cementing of the pressure-resistant non-steel casing in the inclined section of the coal seam is carried out in the roadway. Specifically, the pressure-resistant non-steel casing is lowered from one side of the roadway to the other side. For the pressure-resistant non-steel casing section located within the width of the roadway, Marlite is wrapped around the outer wall of the casing section. The casing is slowly lifted from the ground using the drilling rig lifting system to form a Marlite-filled section. A 1m length is reserved in the roadway at the end of the lowered pressure-resistant non-steel casing. Then, multiple thin tubes are evenly inserted along the outer wall of the pressure-resistant non-steel casing. The thin tubes pass through the Marlite-filled section, and pure cement slurry is injected into each thin tube at the same time to form a pure cement-filled section of the length of the pressure-resistant non-steel casing section. After the pure cement slurry has set for 48 hours, the cementing of the pressure-resistant non-steel casing is completed.

[0022] Furthermore, the construction of the downsloping multi-branch horizontal well in step 4 is as follows: the vertical section is drilled to 10-15m into the bedrock, a steel casing is run in, and mud is circulated for cementing and returned to the surface; the roof-inclined section is drilled to the designed landing point on the roof, a steel casing is run in, and mud is circulated for cementing and returned to the surface; the roof-inclined section is drilled through the tunnel, a steel casing is run in, and mud is circulated for cementing and returned to the surface using auxiliary means.

[0023] Furthermore, in step 4, the spacing between each branch hole is designed to be 60~70m.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] (1) The segmented fracturing of horizontal wells is large in scale and the fractures extend over a wide range, which can effectively reduce the number of boreholes to be laid in the coal seam mining face or roof.

[0026] (2) Using horizontal wells on the surface for segmented fracturing allows for large-scale fracturing, wide range of fracturing fractures, and guaranteed extraction effect;

[0027] (3) Extraction is carried out by the underground negative pressure extraction system, which has a short extraction cycle and high extraction efficiency;

[0028] (4) Drainage and gas extraction are carried out in underground roadways, and multiple branches of the coal seam or roof inclined section are used for efficient drainage, which saves the cost of surface extraction equipment and has high underground drainage efficiency.

[0029] (5) Well repair (well washing) can make full use of the underground roadway, and no working machine is needed on the surface. Attached Figure Description

[0030] Figure 1 Diagram showing well locations for coal seam working faces with updip and near-horizontal well locations;

[0031] Figure 2 This is a well layout diagram for a coal seam working face with a downward dip angle.

[0032] Figure 3 This is a vertical cross-sectional view of the first type of well structure;

[0033] Figure 4 This is a vertical cross-sectional view of the second type of well structure;

[0034] Figure 5 A schematic diagram of cementing the inclined section on the top plate;

[0035] Figure 6 This is a diagram showing the relative positions of the branch holes in the inclined section of the roof and the branch holes in the inclined section below the coal seam.

[0036] Figure 7 A schematic diagram of cementing the lower inclined section of the coal seam;

[0037] Figure 8 This is a distribution map of the perforation direction control zone;

[0038] Figure 9 This is a diagram showing the relative positions of the branch holes in the inclined section of the roof.

[0039] Figure 10 This is a schematic diagram of cementing the inclined section below the roof.

[0040] The meanings of the labels in the diagram are as follows:

[0041] 1. Vertical shaft section, 2. Roof inclined shaft section, 3. Roof inclined shaft section, 4. Perforation point, 5. Roadway, 6. Roof of coal seam mining face, 7. Coal seam mining face, 8. Coal seam downward inclined shaft section, 9. Cross-layer fracture, 10. Coal seam inclined shaft section, 11. Shaft location, 12. Roof downward inclined shaft section, 13. Malisan filling section, 14. Pure cement filling section, 15. Graded hoop. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0043] This embodiment provides a method for rapid gas extraction in a coal seam longwall face in a combined mine and tunnel area, which specifically includes the following steps:

[0044] Step 1: Based on the area of ​​the regional coal seam mining face, the well locations are laid out to ensure that the well trajectories drilled at each of the laid-out well locations completely cover the entire working face area, such as... Figure 1 , 2 As shown.

[0045] Step 2: Accurately determine the dip angle of the coal seam longwall face in the region. Classify the dip angle of the longwall face into two categories: one is updip and the other is near-horizontal, such as... Figure 3 As shown; the second type is a working face with a downward dip angle, such as... Figure 4 As shown. If the dip angle of the working face is updip or near-horizontal, proceed to step 3; if the dip angle of the working face is downdip, proceed to step 4.

[0046] Step 3 involves gas drainage operations in coal seam longwall faces with updip and near-horizontal dip angles, specifically including the following steps:

[0047] Step 31: Drill a multi-branch horizontal well along the roof of the coal seam mining face from the surface. This well is designed as follows: Vertical section 1, Roof inclined section 2, and Roof inclined section 3. Specifically, the vertical section is drilled to 10-15m into the bedrock, a steel casing is run in, and mud is used for positive circulation cementing back to the surface; Roof inclined section 2 is drilled to the designed landing point on the roof, a steel casing is run in, and mud is used for positive circulation cementing back to the surface; Roof inclined section 3 is drilled into the through roadway 5, a steel casing is run in, and mud is used for positive circulation cementing back to the surface using auxiliary methods. Specific implementation method for cementing Roof inclined section 3: as follows... Figure 5 As shown, the casing is lowered from one side of the tunnel to the other. For the casing section located within the tunnel width, Marlite is wrapped around the outer wall of the casing section. The thickness of the wrapping should not exceed the open hole size of the inclined section on the roof. At the ground, the casing is slowly lifted using the drilling rig lifting system. Simultaneously, the Marlite wrapped around the outer wall of the casing is triggered sequentially from top to bottom to achieve the foaming expansion and sealing function, forming a Marlite-filled section. A 1m length is reserved in the tunnel at the end of the lowered casing for the installation of negative pressure gas extraction equipment. Then, multiple thin tubes are evenly inserted along the outer wall of the casing. The thin tubes pass through the Marlite-filled section. Each thin tube is simultaneously injected with a fast-setting pure cement slurry with a specific gravity of the design density, forming a pure cement-filled section tens of meters long. After the pure cement slurry has set for 48 hours, the pure cement slurry is positively circulated and cemented at the ground with the help of a staged hoop. Among them, the number of branch holes drilled in the top plate (i.e., the branch holes of the up-inclined multi-branch horizontal well) is designed to be 3. That is, the up-inclined multi-branch horizontal well is designed with three branch holes consisting of the top plate inclined section 2 and the top plate inclined section 3. The spacing between each branch is designed to be 60~70m, and the spacing can be optimized according to the capacity of the surface fracturing equipment.

[0048] Step 32: Drill a multi-branch horizontal well along the coal seam mining face from the surface. The well is designed as follows: a vertical section, a coal seam directional drilling section 10, and a coal seam downward-sloping section 8. The vertical section is the same as the vertical section 1 drilled in Step 31. The coal seam directional drilling section 10 is drilled to the designed landing point of the coal seam, and a steel casing is run in. The mud is circulated back to the top of the coal seam directional drilling section 10 for cementing. The coal seam downward-sloping section 8 is drilled into the through roadway 5, and a combination of pressure-resistant non-steel screen pipe and pressure-resistant non-steel casing is run in. The pressure-resistant non-steel screen pipe is not cemented, while the pressure-resistant non-steel casing is cemented. The design includes two branch holes (i.e., branch holes of the downsloping multi-branch horizontal well) located at the coal seam mining face. This means the downsloping multi-branch horizontal well has two branch holes formed by the coal seam inclined section 10 and the downsloping section 8. These two branch holes share a vertical section. The spacing between each branch is designed to be 60-70m, which can be adjusted appropriately based on the spacing between the three branch holes in the roof. The trajectories of the two downsloping section branch holes in the coal seam are located below the midpoints of the trajectories of the three upsloping section branch holes in the roof. Figure 1 , 6As shown. The pressure-resistant non-steel casing cementing of the lower inclined section 8 of the coal seam is carried out within roadway 5, specifically implemented as follows: Figure 7 The pressure-resistant non-steel casing is lowered from one side of the through roadway 5 to the other side. For the pressure-resistant non-steel casing section located within the width of the roadway, Marlite is used to wrap around the outer wall of the casing section. The thickness of the wrapping should not exceed the open hole size of the down-dipping section 8 of the coal seam. The casing is slowly lifted from the ground using the drilling rig lifting system. Simultaneously, Marlite wrapped around the outer wall of the pressure-resistant non-steel casing is triggered sequentially from top to bottom to achieve the foaming expansion and sealing function, forming a Marlite filling section. A 1m length is reserved in the roadway at the end of the lowered pressure-resistant non-steel casing for the installation of drainage equipment. Then, multiple thin tubes are evenly inserted along the outer wall of the pressure-resistant non-steel casing. The thin tubes pass through the Marlite filling section. Each thin tube is simultaneously injected with a quick-setting pure cement slurry with a specific gravity of the design density, forming a pure cement filling section of the length of the pressure-resistant non-steel casing section. After the pure cement slurry has set for 48 hours, the cementing of the pressure-resistant non-steel casing is completed.

[0049] Step 33: Perform segmented perforation fracturing sequentially through the three branch holes on the inclined section of the roof, selecting the optimal fracturing sections. Sections within 30 meters of the roadway are excluded from fracturing. According to the designed perforation point 4, segmented perforation fracturing is carried out to generate large-scale, complex cross-seam fractures penetrating the roof and connecting the coal seam. The perforation direction is mainly controlled within a 30° fan-shaped area perpendicular to the coal seam roof along the branch holes on the inclined section of the roof, such as... Figure 8 After the segmented perforation fracturing operation is completed, efficient gas extraction under negative pressure conditions can be achieved in the three branch holes of the inclined section on the roof, and efficient drainage can be achieved in the two branch holes of the inclined section 8 below the coal seam. After the extraction well locations are laid out in the coal seam working face of the area to be mined, efficient gas extraction in the coal mine area can be achieved.

[0050] Step 4 involves gas drainage operations at the down-dipping coal seam longwall face, which includes the following steps:

[0051] This implementation is relatively simple, similar to situations where the formation dip angle is up-dip or near-horizontal (similar to step 31, only the well inclination angle is different due to the different formation dip angles; also, for cases where the formation dip angle is down-dip, there is no need to lay drainage boreholes at the coal seam mining face). A down-dip, multi-branch horizontal well is drilled from the surface along the roof 6 of the coal seam mining face. This well is designed as follows: a vertical section, a roof-inclined section, and a roof-down-dip section. Specifically, the vertical section is drilled to 10-15m into the bedrock, a steel casing is installed, and mud is used for positive circulation cementing back to the surface; the roof-inclined section is drilled to the designed landing point on the roof, a steel casing is installed, and mud is used for positive circulation cementing back to the surface; the roof-down-dip section is drilled through the roadway, a steel casing is installed, and mud is used for positive circulation cementing back to the surface using auxiliary methods. The design includes three branch boreholes located in the roof, meaning the downsloping multi-branch horizontal well has three branch boreholes formed by the roof inclined section and the upper inclined section of the roof. These three branch boreholes share a single vertical section, with a spacing of 60-70 meters between each branch borehole. This spacing can be optimized based on the capacity of the surface fracturing equipment. For formations with a downsloping dip, it is not necessary to install boreholes at the coal seam mining face. Figure 2 , 9 As shown. Cementing of the top-tilted well section (such as...) Figure 10 The segmented perforation fracturing method is the same as the above-described cementing and segmented perforation fracturing method for the inclined section of the roof, except that segmented perforation fracturing is performed on the inclined section below the roof. Upon completion of the segmented perforation fracturing, the three branch holes in the inclined section below the roof can quickly complete drainage operations, creating negative pressure conditions for efficient gas extraction. After this extraction well location is established throughout the coal seam working face area to be mined, efficient gas extraction in the coal mine area can be achieved.

[0052] This invention utilizes segmented fracturing and extraction via horizontal wells to create a fracture network within the coal seam working face. The surface wellhead fracturing scale is large, ranging from 8 to 14 m. 3 / min, while the downhole fracturing scale is only 1-2m 3 The fracturing speed is [value missing] / min, resulting in a long surface extension and a large extraction range, which is beneficial for coal seam gas extraction. Extraction is carried out using roadways connected to horizontal wells, eliminating the need for conventional vertical shaft drilling and the installation of extraction equipment. Furthermore, due to the hydraulic pressure within the horizontal wellbore, extraction only requires controlling the opening of the extraction valve, making it easy to implement. Later, it can be connected to an underground negative pressure extraction system to reduce reservoir pressure by 4-35 kPa, further promoting coal seam gas desorption. This invention changes the traditional coal seam gas extraction method, employing a safer surface construction method that saves on the construction costs of underground floor rock roadways and floor penetration holes, aligning with our country's philosophy of "people-oriented, life-first."

Claims

1. A method for rapid gas extraction in a coal seam longwall face with combined mine shaft and tunnel operations, characterized in that, Specifically, the steps include the following: Step 1: Based on the range of the regional coal seam mining face, the well locations are laid out so that the well trajectories drilled at the laid out well locations can completely cover the entire working face range. Step 2: Accurately determine the dip angle of the strata in the regional coal seam mining face. If the dip angle of the strata in the working face is updip or near-horizontal, proceed to Step 3; if the dip angle of the strata in the working face is downdip, proceed to Step 4. Step 3 involves gas drainage operations in coal seam longwall faces with updip and near-horizontal dip angles, specifically including the following steps: Step 31: Drill an upward-inclined multi-branch horizontal well along the roof of the coal seam mining face from the ground. The well is designed as follows: a vertical section, a roof inclined section, and a roof inclined section. The upward-inclined multi-branch horizontal well includes three branch holes composed of the roof inclined section and the roof inclined section. The three branch holes share a vertical section. Step 32: Drill a downward-sloping multi-branch horizontal well along the coal seam mining face from the surface. The well is designed as follows: a vertical section, a coal seam sloping section, and a coal seam downward-sloping section. The downward-sloping multi-branch horizontal well includes two branch holes composed of the coal seam sloping section and the coal seam downward-sloping section. The two branch holes share a vertical section, which is the same as the vertical section in Step 31. The trajectories of the two branch holes are located below the midpoints of the pairwise trajectories of the three branch holes of the upward-sloping multi-branch horizontal well. Step 33: Perform segmented perforation fracturing on the three branch holes of the inclined section on the roof in sequence to select the fracturing section; perform segmented perforation fracturing according to the designed perforation points; the direction of the perforation is perpendicular to the coal seam roof and a certain fan-shaped area on the left and right sides of the branch holes of the inclined section on the roof. Step 4: For a coal seam longwall face with a downward dip angle, drill a downward-dipping multi-branch horizontal well along the roof of the longwall face. This horizontal well is designed as follows: a vertical section, a roof inclined section, and a roof downward-dipping section. The downward-dipping multi-branch horizontal well along the roof of the longwall face includes three branch holes composed of a roof inclined section and a roof downward-dipping section, with the three branch holes sharing a vertical section. Perform segmented perforation fracturing on the roof downward-dipping section and carry out gas drainage operations on the coal seam longwall face.

2. The method for rapid gas extraction in a coal seam longwall face with combined mine shaft and roadway operations as described in claim 1, characterized in that, Step 31 specifically includes the following operations: The vertical well section is drilled to 10-15m into the bedrock, a steel casing is installed, and mud is used for positive circulation cementing and returned to the surface; the roof inclined well section is drilled to the designed landing point on the roof, a steel casing is installed, and mud is used for positive circulation cementing and returned to the surface; the roof inclined well section is drilled through the tunnel, a steel casing is installed, and mud is used for positive circulation cementing and returned to the surface.

3. The method for rapid gas extraction in a coal seam longwall face with combined mine shaft and roadway operations as described in claim 2, characterized in that, In step 31, the specific implementation method for cementing the inclined section on the top plate is as follows: the casing is lowered from one side of the tunnel to the other side. For the casing section located in the tunnel width, Marlite is wrapped around the outer wall of the casing section. At the ground, the casing is slowly lifted using the drilling rig lifting system. Simultaneously, the Marlite wrapped around the outer wall of the casing is triggered from top to bottom to form a Marlite filling section. A 1m length is reserved in the tunnel at the end of the lowered casing. Then, multiple thin tubes are evenly inserted along the outer wall of the casing. The thin tubes pass through the Marlite filling section. Pure cement slurry is injected into each thin tube at the same time to form a pure cement filling section. After the pure cement slurry has set for 48 hours, pure cement slurry positive circulation cementing is carried out on the ground with the help of a staged hoop.

4. The method for rapid gas extraction in a coal seam longwall face with combined mine shaft and roadway operations as described in claim 1, characterized in that, In step 31, the spacing between each branch hole is 60~70m.

5. The method for rapid gas extraction in a coal seam longwall face with combined mine shaft and roadway operations as described in claim 1, characterized in that, In step 32, the vertical well section is the same as the vertical well section drilled in step 1; the coal seam inclined well section is drilled to the designed landing point of the coal seam, and a steel casing is installed, with mud circulating back to the top of the coal seam inclined well section; the coal seam downward inclined well section is drilled through the roadway, and a combination of pressure-resistant non-steel screen pipe and pressure-resistant non-steel casing is installed, with the pressure-resistant non-steel screen pipe not cemented, and the pressure-resistant non-steel casing cemented.

6. The method for rapid gas extraction in a coal seam longwall face with combined mine shaft and roadway operations as described in claim 4, characterized in that, In step 32, the spacing between the branch holes of the downward inclined multi-branch horizontal well is 60~70m.

7. The method for rapid gas extraction in a coal seam longwall face with combined mine shaft and roadway operations as described in claim 1, characterized in that, In step 32, the cementing of the pressure-resistant non-steel casing in the inclined section of the coal seam is carried out in the roadway. Specifically, the pressure-resistant non-steel casing is lowered from one side of the roadway to the other side. For the pressure-resistant non-steel casing section located in the width of the roadway, Marlite is wrapped around the outer wall of the casing section. The casing is slowly lifted from the ground using the drilling rig lifting system to form a Marlite filling section. A 1m length is reserved in the roadway at the end of the lowered pressure-resistant non-steel casing. Then, multiple thin tubes are evenly inserted along the outer wall of the pressure-resistant non-steel casing. The thin tubes pass through the Marlite filling section. Pure cement slurry is injected into each thin tube at the same time to form a pure cement filling section of the length of the pressure-resistant non-steel casing section. After the pure cement slurry has set for 48 hours, the cementing of the pressure-resistant non-steel casing is completed.

8. The method for rapid gas extraction in a coal seam longwall face with combined mine shaft and roadway operations as described in claim 1, characterized in that, The construction of the downsloping multi-branch horizontal well in step 4 is as follows: the vertical section is drilled to 10-15m into the bedrock, a steel casing is run in, and mud is circulated for cementing and returned to the surface; the roof-inclined section is drilled to the designed landing point on the roof, a steel casing is run in, and mud is circulated for cementing and returned to the surface; the roof-inclined section is drilled through the tunnel, a steel casing is run in, and mud is circulated for cementing and returned to the surface using auxiliary means.

9. The method for rapid gas extraction in a coal seam longwall face with combined mine shaft and roadway operations as described in claim 8, characterized in that, In step 4, the spacing between each branch hole is designed to be 60~70m.

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