Hydraulic fracturing-based method for efficient control of rock burst and gas in mining area

Abstract

The present application belongs to the field of deep coal seam mining, and particularly relates to a mining area rock burst and gas efficient control method based on hydraulic fracturing; a plurality of working faces are designed in turn from bottom to top along the inclination, a return air roadway of the last working face is constructed, a mining area air inlet roadway is constructed at the lower part of the first working face inclination, then a bedding borehole is constructed to connect the return air roadway of the last working face and the mining area air inlet roadway, and hydraulic fracturing pressure relief and gas pre-drainage are performed. The return air roadway and the transportation roadway of the first working face are constructed from the transportation upward slope, and the return air roadway is left along the goaf during recovery as the transportation roadway of the next working face; ventilation is performed from the transportation roadway to the working face coal mining position and from the mining area air inlet roadway to the goaf; the gas in the coal seam is carried to the return air roadway of the last working face by the remaining working face bedding borehole and the hydraulic fracturing fissure, and is discharged. The present application can ensure the gas pre-drainage effect of the subsequent working face, and solve the problem of gas disaster caused by the goaf.

Description

Technical Field

[0001] This invention belongs to the field of deep coal seam mining, specifically relating to an efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing. Background Technology

[0002] As coal seams deepen, the pressure they bear increases, making them prone to rockbursts during deep coal seam mining. Furthermore, coal seams often contain associated gas, which is difficult to dislodge and can easily lead to gas disasters during mining. Hydraulic fracturing and gas pre-drainage before mining are crucial for preventing rockbursts and gas disasters, providing essential conditions for safe mining. Therefore, the quality of gas pre-drainage is paramount; however, a short pre-drainage period can negatively impact safe mining, while a long period can disrupt production planning. In addition, gas can easily accumulate in goafs formed during the mining of gaseous coal seams, potentially triggering gas disasters. Therefore, ensuring both high-quality gas pre-drainage and goaf safety while maintaining production planning is key to efficient and safe deep coal seam mining. Summary of the Invention

[0003] To address the shortcomings of the existing technologies, this invention proposes a highly efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing, which specifically includes the following steps.

[0004] S1: Design several working faces sequentially from bottom to top along the dip in the mining area and number them from the first to the Nth working face; S2: Construct the return airway of the Nth working face along the strike from the return air incline, and construct the intake airway of the mining area along the strike from the transport incline at the lower part of the first working face; Construct several in-seam boreholes along the dip to connect the return airway of the Nth working face and the intake airway of the mining area; Hydraulic fracturing and depressurization of the coal seam are performed through the in-seam boreholes; S3: Construct the return airway and transport airway of the first working face along the strike from the transport incline, and construct a cut-out of the first working face to connect the two; Extend the cut-out of the first working face to connect the intake airway of the mining area; S4: S5: The first working face is mined, and the return airway of the first working face is left along the goaf to form the transport airway of the second working face; fresh air is introduced from the transport airway of the first working face and the intake airway of the mining area; S6: The return airway of the second working face is constructed along the strike from the transport uphill, and the cut-in of the second working face is constructed; S7: The second working face is mined, and the return airway of the second working face is left along the goaf to form the transport airway of the third working face; fresh air is introduced from the transport airway of the second working face and the intake airway of the mining area; this cycle continues until the mined face reaches the (N-1)th working face; S8: The cut-in of the Nth working face is constructed; S9: The Nth working face is mined.

[0005] Preferably, the gas content in the coal seam within the mining area gradually increases from bottom to top along the dip direction.

[0006] Preferably, in step S2, the in-seam boreholes are arranged at intervals along the strike; after hydraulic fracturing and depressurization of the coal seam through the in-seam boreholes, the in-seam boreholes are then used to pre-drain the gas from the coal seam.

[0007] Preferably, in step S3, an air door is installed at the stop line position of the first working face in the return airway of the first working face; the borehole in the middle layer of the first working face is sealed.

[0008] Preferably, in step S4, the first working face cut-out is retained, and the retained first working face cut-out is connected to the first working face goaf, and ventilation holes are constructed on the goaf wall to connect the first working face goaf.

[0009] Preferably, in step S4, fresh air is introduced from the first working face transport roadway to the coal mining position of the first working face, and then enters the first working face return air roadway and the second working face transport roadway to become exhaust air; fresh air is introduced from the mining area intake air roadway into the goaf of the first working face, and then enters the second working face transport roadway to become exhaust air; the exhaust air passes through the in-seam borehole and its hydraulic fracturing fractures, carrying the gas in the remaining coal seam of the working face to the Nth working face return air roadway.

[0010] Preferably, in step S5, the ventilation holes on the second working face transport level and the remaining first working face cut are closed; the air doors in the second working face transport level are removed.

[0011] Preferably, in step S5, an air door is installed at the stop line position of the second working face in the return airway of the second working face; the borehole in the middle layer of the second working face is closed.

[0012] Preferably, in step S6, fresh air is introduced from the second working face transport roadway to the coal mining position of the second working face, and then becomes exhaust air and enters the second working face return air roadway and the third working face transport roadway; fresh air is introduced from the mining area intake air roadway into the goaf of the second working face, and then becomes exhaust air and enters the third working face transport roadway; the exhaust air then passes through the in-seam borehole and its hydraulic fracturing fractures, carrying the gas in the remaining coal seam of the working face to the Nth working face return air roadway.

[0013] Preferably, in step S7, the ventilation holes on the Nth working face transport level and the remaining N-1th working face cut are closed; the air door in the Nth working face transport level is removed.

[0014] Preferably, in step S8, during the mining process, fresh air is introduced from the transport roadway of the Nth working face to the coal mining position of the Nth working face, and then becomes exhaust air and enters the return air roadway of the Nth working face; fresh air is introduced from the intake air roadway of the mining area into the goaf of the Nth working face, and then becomes exhaust air and enters the return air roadway of the Nth working face.

[0015] The inventive points and beneficial technical effects of this invention are as follows: 1. This invention designs several working faces sequentially from bottom to top along the dip direction in the mining area. First, the return airway of the last working face is constructed in the mining area, and the intake airway of the mining area is constructed at the lower part of the dip direction of the first working face. Then, hydraulic fracturing is performed by drilling along the bedding plane between the return airway of the last working face and the intake airway of the mining area. This allows for depressurization and pre-extraction of gas from the entire goaf. The construction of the along-bedding plane is centralized, avoiding the tedious process of constructing along-bedding planes separately before mining each working face.

[0016] 2. Based on this, during the mining process, the return airway and transport airway of the haulage face are used as haulage airways for the next working face by leaving the return airway along the goaf. After ventilation from the transport airway to the coal mining position, it becomes exhaust air. Simultaneously, after ventilation of the goaf from the mining area intake airway, it also becomes exhaust air. The exhaust air then passes through in-seam boreholes and hydraulic fracturing fractures, carrying the gas from the remaining coal seam to the return airway of the last working face for discharge. In other words, this invention can utilize the exhaust air of the currently mining face to pre-drain gas from subsequent working faces, ensuring that subsequent working faces can perform gas pre-drainage for a long time. Furthermore, the designed mining area intake airway ventilates the goaf, solving the problem of gas disasters caused by the goaf. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the drilling construction in the mid-layer of the mining area for efficient control of rockburst and gas according to the present invention.

[0018] Figure 2 This is a schematic diagram of the layout of the first working face in the mining area for efficient control of rockburst and gas according to the present invention.

[0019] Figure 3 This is a schematic diagram of the first working face in the efficient rockburst and gas control mining area of ​​the present invention.

[0020] Figure 4 This is a schematic diagram of the layout of the second working face in the mining area for efficient control of rockburst and gas according to the present invention.

[0021] Figure 5 This is a schematic diagram of the second working face in the mining area for efficient control of rockburst and gas according to the present invention.

[0022] Figure 6 This is a schematic diagram of the layout of the third working face in the mining area for efficient control of rockburst and gas according to the present invention.

[0023] Figure 7 This is a schematic diagram of the third working face in the mining area for efficient control of rockburst and gas according to the present invention.

[0024] In the diagram: 1-Return air incline; 2-Transport incline; 3-Intake airway of the mining area; 41-Stop line of the first working face; 42-Stop line of the second working face; 43-Stop line of the third working face; 51-Mining location of the first working face; 52-Mining location of the second working face; 53-Mining location of the third working face; 61-Transport airway of the first working face; 62-Transport airway of the second working face; 63-Transport airway of the third working face; 71-Return airway of the first working face; 72-Return airway of the second working face; 73-Return airway of the third working face; 81-Cutoff of the first working face; 82-Cutoff of the second working face; 83-Cutoff of the third working face; 91-Goaf of the first working face; 92-Goaf of the second working face; 93-Goaf of the third working face; 10-In-seam borehole; 11-Air door. Detailed Implementation

[0025] The specific embodiments of the present invention will now be described in conjunction with the accompanying drawings.

[0026] like Figures 1-7 As shown, this invention proposes an efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing, which is particularly suitable for working conditions where the gas content in the coal seam gradually increases from bottom to top along the dip direction; it includes the following steps.

[0027] S1: The first working face, the second working face, and the third working face are designed sequentially from bottom to top along the dip in the mining area.

[0028] S2: As Figure 1 As shown, the return airway 73 of the third working face is constructed along the strike from the return airway 1. The intake airway 3 of the mining area is constructed along the strike from the transport airway 2 at the lower dip of the first working face. Bedding boreholes 10 are drilled from the return airway 73 of the third working face towards the intake airway 3 of the mining area. These bedding boreholes 10 are spaced apart along the strike. Hydraulic fracturing and depressurization of the coal seam are performed through the bedding boreholes 10. Gas pre-drainage of the coal seam is then carried out using the bedding boreholes 10. In this invention, "dip" refers to the dip of the coal seam, and "strike" refers to the strike of the coal seam. "Dip" and "strike" are professional geological terms expressing the direction of strata and will not be elaborated upon here.

[0029] S3: As Figure 2 As shown, the first working face return airway 71 and the first working face transport airway 61 are constructed along the direction of the transport uphill 2. At the starting position of the first working face mining, the first working face cut-out 81 is constructed to connect the first working face return airway 71 and the first working face transport airway 61. The first working face cut-out 81 is extended to connect the mining area intake airway 3. The cross-sectional dimension of the extended part, that is, the part connecting the mining area intake airway 3 and the first working face transport airway 61, can be smaller than the first working face cut-out 81. An air door 11 is set at the first working face stop line 41 in the first working face return airway 71. The bedding borehole 10 in the first working face is sealed.

[0030] S4: As Figure 3 As shown, the first working face is mined, forming a goaf 91. The first working face cut-out 81 is retained, and the retained cut-out 81 is connected to the goaf 91 (for example, ventilation holes can be constructed on the sidewall of the retained cut-out 81 near the goaf 91). The cross-sectional dimensions of the retained cut-out 81 can be smaller than the original cut-out 81. During the mining process, the return airway 71 of the first working face is left along the goaf to form a second working face transport roadway 62. Ventilation holes are constructed on the wall of the left-away roadway to connect to the goaf 91 of the first working face. The mining of the first working face is carried out directly... To the first working face stop line 41; during the mining process, fresh air is introduced from the first working face transport level 61 to the first working face coal mining position 51, and then becomes exhaust air and enters the first working face return air level 71 and the second working face transport level 62; at the same time, fresh air is introduced from the mining area intake air level 3 into the first working face goaf 91, and then becomes exhaust air and enters the second working face transport level 62; the exhaust air then passes through the in-seam borehole 10 and its hydraulic fracturing fractures, carrying the gas in the coal seams of the second and third working faces to the third working face return air level 73, forming a gas pre-extraction effect on the coal seams of the second and third working faces, and then is discharged from the mining area through the return air incline 1.

[0031] S5: As Figure 4 As shown, the second working face return airway 72 is constructed along the direction of the transport uphill 2. At the starting position of the second working face mining, the second working face cut-out 82 is constructed to connect with the retained first working face cut-out 81. The ventilation holes on the second working face transport airway 62 and the retained first working face cut-out 81 are sealed. The air door 11 in the second working face transport airway 62 is removed. An air door 11 is installed at the second working face stop mining line 42 in the second working face return airway 72. The mid-layer borehole 10 in the second working face is sealed.

[0032] S6: As Figure 5As shown, the second working face is mined, forming a goaf 92. The second working face cut-out 82 is retained, and the retained cut-out 82 is connected to the goaf 92 (for example, by constructing ventilation holes on the sidewall of the retained cut-out 82 near the goaf 92). The cross-sectional dimensions of the retained cut-out 82 can be smaller than the original cut-out 82. During the mining process, the return airway 72 of the second working face is left along the goaf to form a third working face transport roadway 63. Ventilation holes are constructed on the wall of the left-away roadway to connect to the goaf 92 of the second working face. The mining continues until the second working face stops at the mining line 42. During the mining process, fresh air is introduced from the second working face transport level 62 to the second working face coal mining position 52, and then becomes exhaust air and enters the second working face return air level 72 and the third working face transport level 63. At the same time, fresh air is introduced from the mining area intake air level 3 into the second working face goaf 92, and then becomes exhaust air and enters the third working face transport level 63. The exhaust air then passes through the in-seam borehole 10 and its hydraulic fracturing fractures, carrying the gas in the third working face coal seam to the third working face return air level 73, forming a gas pre-extraction effect on the third working face coal seam, and then is discharged from the mining area through the return air incline 1.

[0033] S7: As Figure 6 As shown, at the starting position of the third working face mining, the third working face cut-out 83 is constructed to connect the retained second working face cut-out 82 with the third working face return airway 73; the third working face transport airway 63 and the ventilation holes on the retained second working face cut-out 82 are sealed; and the air door 11 in the third working face transport airway 63 is removed.

[0034] S8: As Figure 7 As shown, the third working face is mined, and after the mining, the goaf 93 of the third working face is formed; the mining of the third working face continues until the stop line 43 of the third working face is reached; during the mining process, fresh air is introduced from the transport roadway 63 of the third working face to the coal mining position 53 of the third working face, and then becomes exhaust air and enters the return air roadway 73 of the third working face; at the same time, fresh air is introduced from the intake air roadway 3 of the mining area, passing through the first working face cut-out 81 and the second working face cut-out 82 in sequence and then entering the goaf 93 of the third working face, and then becomes exhaust air and enters the return air roadway 73 of the third working face, and the exhaust air is then discharged from the mining area through the return air incline 1.

[0035] This invention is not limited to the preferred embodiments described above. Anyone can derive other methods in various forms under the guidance of this invention. Any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A highly efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing, characterized in that, Includes the following steps: S1: Several working faces are designed sequentially from bottom to top along the dip in the mining area and numbered sequentially as the first to the Nth working faces; S2: Construct the return airway of the Nth working face along the strike from the return air incline; construct the intake airway of the mining area along the strike from the transport incline at the lower part of the first working face; construct several in-seam boreholes along the strike to connect the return airway of the Nth working face and the intake airway of the mining area; perform hydraulic fracturing and depressurization of the coal seam through the in-seam boreholes. S3: Construct the return airway and transport airway of the first working face along the direction of the transport uphill section, and connect the two by constructing the first working face cut-out; extend the first working face cut-out to connect the intake airway of the mining area; S4: The first working face is mined back, and the return airway of the first working face is left along the goaf to form the transport airway of the second working face; fresh air is introduced from the transport airway of the first working face and the intake airway of the mining area; the first working face cut-off is preserved, and the preserved first working face cut-off is connected to the goaf of the first working face, and ventilation holes are constructed on the wall of the left-along-goaf to connect to the goaf of the first working face; fresh air is introduced from the transport airway of the first working face to the coal mining position of the first working face, and then becomes exhaust air and enters the return airway of the first working face and the transport airway of the second working face; fresh air is introduced from the intake airway of the mining area into the goaf of the first working face, and then becomes exhaust air and enters the transport airway of the second working face; the exhaust air then passes through the in-seam borehole and its hydraulic fracturing fractures, carrying the gas in the remaining coal seam of the working face to the return airway of the Nth working face. S5: Construction of the return airway of the second working face along the direction of the uphill transport, and construction of the cut-in point of the second working face; S6: Mining the second working face, leaving a roadway along the gob in the return airway of the second working face to form a transport roadway for the third working face; fresh air is introduced from the transport roadway of the second working face and the intake airway of the mining area; this cycle continues until mining reaches the N-1 working face; S7: Cutting the Nth working face during construction; S8: Perform back mining on the Nth working face.

2. The efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing according to claim 1, characterized in that, The gas content in the coal seam within the mining area gradually increases from bottom to top along the dip direction.

3. The efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing according to claim 1, characterized in that, In step S2, the in-seam boreholes are arranged at intervals along the strike; after hydraulic fracturing and depressurization of the coal seam through the in-seam boreholes, the coal seam is pre-drained of gas using the in-seam boreholes.

4. The efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing according to claim 3, characterized in that, In step S3, an air door is installed at the stop line position of the first working face in the return airway of the first working face; the borehole in the middle layer of the first working face is sealed.

5. The efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing according to claim 1, characterized in that, In step S5, the ventilation holes on the second working face transport roadway and the remaining first working face cut are sealed; the air doors in the second working face transport roadway are removed; an air door is installed at the second working face stop line position in the second working face return airway; and the in-seam borehole in the second working face is sealed.

6. The efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing according to claim 5, characterized in that, In step S6, fresh air is introduced from the second working face transport roadway to the coal mining position of the second working face, and then becomes exhaust air and enters the second working face return air roadway and the third working face transport roadway; fresh air is introduced from the mining area intake air roadway into the goaf of the second working face, and then becomes exhaust air and enters the third working face transport roadway; the exhaust air then passes through the in-seam borehole and its hydraulic fracturing fractures, carrying the gas in the remaining coal seam of the working face to the Nth working face return air roadway.

7. The efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing according to claim 6, characterized in that, In step S7, the ventilation holes on the Nth working face transport level and the remaining N-1th working face cut are closed; the air door in the Nth working face transport level is removed.

8. The efficient method for controlling rockburst and gas in mining areas based on hydraulic fracturing according to claim 7, characterized in that, In step S8, during the mining process, fresh air is introduced from the transport roadway of the Nth working face to the coal mining position of the Nth working face, and then becomes exhaust air and enters the return air roadway of the Nth working face; fresh air is introduced from the intake air roadway of the mining area into the goaf of the Nth working face, and then becomes exhaust air and enters the return air roadway of the Nth working face.

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