Well-ground cooperative coal mine mining area gas disaster control method

Abstract

The application discloses a kind of well ground coordination coal mine mining area gas disaster control method, first in the exploitation area stage of coal mine is implemented to control mining area working face excavation strip roadway stored coal seam gas;In mining area strip roadway, after the preferred strip roadway excavation is completed, determine the gas control mode of the rest coal seam mining face, which depends on the angle between the minimum principal stress direction of stratum and the direction of excavation strip roadway, based on the roof fracturing borehole drilled, coal seam fracturing borehole or coal seam gas extraction bedding borehole carries out coal mine underground negative pressure gas efficient extraction.The present application can realize only in the exploitation area and preparation area stage of the whole life production cycle of coal mine to reduce coal seam gas content to the minimum requirement standard 8m 3 / t of coal seam excavation, and then effectively guarantee the replacement of coal mining, ensure efficient and safe production in production area of coal mine, while reducing the cost of gas control, realize integrated gas disaster control.

Description

Technical Field

[0001] This invention belongs to the field of coal mine gas disaster control technology, and relates to a method for coal mine gas disaster control in a coordinated manner between the mine and the ground. Background Technology

[0002] my country has abundant coal reserves, and coal will remain the country's primary and fundamental energy source for a considerable period, with both production and consumption continuing to grow. However, methane gas is a major factor restricting the safe mining of coal resources, seriously threatening the safety of life and property. Therefore, methane drainage must be carried out before coal mining to reduce or eliminate methane levels in the coal seams.

[0003] The entire life cycle of coal mining is mainly divided into three stages: development zone, preparation zone, and production zone. Currently, gas hazard control methods for the entire life cycle of coal mining can be divided into two main categories: surface gas extraction methods, mainly including combinations of vertical wells and fracturing technology, combinations of horizontal wells and segmented fracturing technology, and mining-induced well technology; and underground gas extraction methods, mainly including in-seam drilling technology, bottom drainage roadway cross-seam drilling technology, combinations of near-horizontal long boreholes and segmented fracturing technology, and high-level drilling technology. The above-mentioned gas extraction technologies are the main means of gas hazard control in coal mining areas today, and each of these methods corresponds to a different life cycle stage of the coal mining process.

[0004] Relying solely on any single method is insufficient to effectively address the gas hazard threat throughout the entire coal mining process, nor can it adequately address the continuity issues within the mining operation, ensuring that the production phase of the entire coal mining lifecycle is unaffected by gas hazards. Therefore, to effectively eliminate or mitigate the coal seam gas hazard threat throughout the entire coal mining process and ensure the effective continuity of coal mining activities, a comprehensive approach is needed. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for gas disaster management in coal mining areas with well-ground coordination, so as to solve the problems that the existing technology is unable to effectively solve the gas disaster threat throughout the entire coal mining process, and also cannot meet the problems of continuity in the coal mining process, and cannot ensure that the production area stage of the entire life cycle of coal mining is not affected by gas disasters.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for controlling gas disasters in coal mining areas using a combined mine-ground approach includes the following steps:

[0008] Step 1: Determine the relative spatial layout between the strip roadway to be excavated and the coal seam mining face in the coal mining area that needs to be treated.

[0009] Step 2: Determine the Protodyakonov hardness value f of the coal seam in the working face to be treated in the coal mining area;

[0010] Step 3: Based on the Protodyakonov hardness value f of the coal seam in the treatment working face obtained in Step 2, determine the layout layer of the L-shaped long horizontal borehole track for the treatment of gas in the strip roadway to be excavated. The layout layer is the coal seam or the roof of the coal seam in the strip roadway to be excavated.

[0011] Step 4: After the L-shaped long horizontal borehole on the ground is completed according to the design requirements in Step 3, the L-shaped long horizontal borehole on the ground is flushed with solids-free drilling fluid until no rock cuttings are returned from the borehole. Then, sonic logging, density logging and caliber logging instruments are installed to obtain formation stress parameters. Then, cluster perforation and hydraulic fracturing are carried out in this coal seam or the roof of the coal seam. Microseismic monitoring is carried out at the same time as the hydraulic fracturing process.

[0012] Step 5: After the completion of step 4, perform hydraulic fracturing followed by pressure release and blowout. Then, install the wellhead gas extraction device to extract gas from the roadway to be excavated. The extraction process should continue until the gas level in the roadway is reduced to the point where the surface well produces no gas or the coal seam gas content is below 8 mg / m³. 3 When the coal seam gas pressure is less than 0.74 MPa, strip roadway excavation is carried out in the coal mine.

[0013] Step 6: After the excavation of the above-mentioned strip roadway is completed, calculate the magnitude and direction of the minimum horizontal principal stress of the coal seam in the mining area based on the stratum stress parameter information obtained in Step 4. At the same time, determine the gas control mode of the remaining coal seam mining face based on the Protodyakonov hardness value f of the coal seam in the mining area measured in Step 2.

[0014] Step 7: Based on the completion of the construction in Step 6, perform full-section perforation within the main borehole of various near-horizontal long boreholes drilled along the coal seam or coal seam roof, within a section S meters from the borehole opening or the main borehole of multiple branch near-horizontal boreholes. This ensures communication between the main boreholes of various near-horizontal long boreholes drilled along the coal seam or coal seam roof and the surrounding hydraulic fracturing influence area, thereby ensuring the gas convergence within the control range of the main boreholes of various near-horizontal long boreholes drilled along the coal seam or coal seam roof, and thus enabling the extraction of gas stored in the coal seam mining face.

[0015] The present invention also includes the following technical features:

[0016] Specifically, in step 2, if the coal seam hardness value f≥1, it indicates that the coal seam hardness is good, and the drilling construction of this coal seam is safe, has good porosity, and a high porosity rate; conversely, it indicates that the coal seam hardness is poor, and the drilling construction of the coal seam has safety hazards, poor porosity, and a low porosity rate.

[0017] Specifically, in step 3, if the coal seam hardness value f≥1, then the L-shaped long horizontal borehole track on the ground is laid in the coal seam where the strip roadway to be excavated is to be treated.

[0018] If the coal seam hardness value f < 1, then the L-shaped long horizontal borehole track on the ground will be laid in the roof of the coal seam of the strip roadway to be excavated. The distance between the L-shaped long borehole track on the ground in the roof of the coal seam of the strip roadway to be excavated and the top of the coal seam will be controlled within the range of 0 to 1m.

[0019] Specifically, in step 4, microseismic monitoring with denser measuring points is used to ensure efficient and accurate acquisition of the farthest radial extension distance S of the hydraulic fracturing crack along the L-shaped horizontal borehole track on the ground during the hydraulic segmented fracturing construction process, while effectively monitoring the boundary of the hydraulic segmented fracturing crack extension range in real time.

[0020] Specifically, step 6 includes:

[0021] Step 61: If the angle α between the direction of the minimum principal stress and the direction of the tunneling strip roadway is greater than or equal to 45° and the coal seam hardness value f≥1 in the mining area, then the design is to construct near-horizontal long boreholes along both sides of the strip roadway and perform hydraulic segmented fracturing on the surface to carry out gas extraction in the coal seam mining face.

[0022] Step 62: If the angle α between the direction of the minimum principal stress and the direction of the tunneling strip roadway is greater than or equal to 45° and the coal seam hardness value f < 1, then the coal seam roof or the near-horizontal long borehole of the coal seam and the surface hydraulic segmented fracturing are designed to be constructed along both sides of the strip roadway to carry out gas extraction of the coal seam mining face.

[0023] Step 63: If the angle α between the direction of the minimum principal stress and the direction of the tunneling strip is less than 45°, then multiple branch near-horizontal boreholes of the coal seam are constructed on both sides of the strip roadway, and boreholes along the coal seam are designed to be constructed on both sides of the strip roadway within the strip roadway to carry out gas extraction at the coal seam mining face.

[0024] Specifically, in step 63, based on the design of a main hole at the center of each segment of the hydraulic fracturing construction in step 4 above, a multi-branch near-horizontal borehole is constructed. The main hole of the multi-branch near-horizontal borehole is drilled to the farthest distance S meters along the L-shaped long horizontal borehole track of the hydraulic fracturing in step 4 above. Then, multiple branch holes are opened at the depth S meters of the main hole of the multi-branch near-horizontal borehole. The spacing between each branch hole is designed to be 5 to 10 meters. Each branch hole is drilled until the designed hole depth.

[0025] Specifically, in step 6, all the near-horizontal long boreholes or multi-branch near-horizontal main boreholes drilled along the coal seam or the roof of the coal seam are drilled to the farthest distance S meters along the radial extension of the hydraulic fracturing fracture in step 4 along the L-shaped long horizontal borehole track on the ground, and pneumatic directional drilling is used for construction.

[0026] Specifically, PVC pipes or fiberglass casings are installed in the main boreholes of each near-horizontal long borehole or multi-branch near-horizontal borehole to a depth of S meters. Marlium and pure cement slurry are used to seal the annulus around the PVC pipes or fiberglass casings. The pure cement slurry seals the borehole to a depth of S meters to ensure that the pure cement slurry can effectively seal the furthest distance S meters of the fracturing fracture propagation. This reduces gas loss during pneumatic directional drilling or drilling fluid loss during conventional hydraulic drilling during subsequent drilling of the branch holes of each near-horizontal long borehole or multi-branch near-horizontal borehole. Then, near-horizontal long borehole drilling continues at a depth of S meters in the main borehole of each near-horizontal long borehole or side-drilling is used to open branch holes for multi-branch near-horizontal boreholes.

[0027] Specifically, for the near-horizontal long borehole drilling carried out outside the boundary of the hydraulic segmented fracturing fracture in step 61, a water-based drilling fluid circulation system is used for drilling.

[0028] Specifically, for the drilling method of near-horizontal long boreholes constructed outside the boundary of the hydraulic segmented fracturing fracture in step 62, if the design is to construct near-horizontal long boreholes in the coal seam roof, a water-based drilling fluid circulation system is adopted; if the design is to construct near-horizontal long boreholes in the coal seam, a pneumatic directional drilling process is adopted.

[0029] Specifically, for the drilling method of the multi-branch near-horizontal borehole in step 63, based on the coal seam hardness value of the treatment working face obtained in step 2, if the coal seam hardness value f≥1, the multi-branch near-horizontal borehole is drilled using a water-based drilling fluid circulation system; if the coal seam hardness value f<1, the multi-branch near-horizontal borehole is drilled using a pneumatic directional drilling process.

[0030] Compared with the prior art, the present invention has the following technical effects:

[0031] The method of this invention can efficiently eliminate or reduce the hazards of gas disasters in coal mining areas to a level that does not affect the safety of life and property before the production stage of the entire life cycle of coal mining.

[0032] This invention uses the coal seam hardness value, i.e., the drilling porosity, as the main judgment parameter. Based on the effective combination and sequential connection of existing surface gas extraction methods and underground gas extraction methods, and referring to the coal seam hardness and porosity, it optimizes the suitable strata for the drilling process in surface gas extraction methods. It also optimizes the gas control mode for the remaining coal seam longwall faces after the completion of the strip roadway excavation in the mining area, and the reasonable drilling method for the underground in-seam drilling process. This efficiently reduces the coal seam gas content to the minimum requirement of 8m³ for coal seam mining in the development and preparation areas throughout the entire coal mine production cycle. 3 The coal seam gas pressure in the mining area is 0.74 MPa, which ensures that the coal mining is not affected by gas disasters during the production phase and that mining can continue smoothly. Attached Figure Description

[0033] Figure 1 A diagram showing the relative spatial positions of the strip roadway to be excavated and the longwall face in the treatment working face;

[0034] Figure 2 This is a diagram showing the layout of the L-shaped horizontal borehole track in the coal seam of the strip roadway to be excavated.

[0035] Figure 3 A diagram showing the layout of the L-shaped horizontal borehole track on the roof of the coal seam in the tunnel to be excavated.

[0036] Figure 4 Horizontal projection diagram of segmented fracturing of the strip to be excavated in an L-shaped long horizontal borehole on the ground;

[0037] Figure 5 Design drawings for main holes and branch holes of multi-branch near-horizontal boreholes along the bedding plane in underground coal mines;

[0038] Figure 6 This is a schematic diagram showing the angle between the direction of the minimum principal stress in the coal seam and the direction of the tunneling strip.

[0039] Figure 7 A schematic diagram of segmented fracturing construction of near-horizontal long boreholes in underground strip roadways of coal mines based on L-shaped long horizontal boreholes on the ground.

[0040] Figure 8 This is a schematic diagram of the borehole layout for the roof or near-horizontal long boreholes in a coal seam.

[0041] The meanings of the labels in the diagram are as follows:

[0042] 1. Coal seam mining face; 2. Roadway to be excavated; 3. Surface; 4. Coal seam roof; 5. Coal seam; 6. Surface L-shaped long horizontal borehole track; 7. Fracturing fracture; 8. Surface L-shaped wellhead; 9. Perforation point; 10. Boundary of hydraulic segmented fracturing fracture expansion range; 11. Branch holes of multi-branch near-horizontal boreholes; 12. Main holes of multi-branch near-horizontal boreholes; 13. Direction of minimum principal stress; 14. Direction of roadway excavation; 15. Surface fracturing pump unit; 16. Hydraulic fracturing high-pressure pipeline; 17. Near-horizontal long borehole. Detailed Implementation

[0043] This invention provides a method for controlling gas disasters in coal mining areas using a combined well-ground approach. Firstly, during the coal mine development phase, the gas stored in the coal seam in the tunneling strips of the working face is controlled. This is achieved by combining surface L-shaped long horizontal drilling with hydraulic fracturing technology for pre-drainage. The goal is to reduce the gas level in the tunneling strips of the working face to a level where surface wells are not producing gas or the coal seam gas content is below 8 m³. 3 When the coal seam gas pressure is less than 0.74 MPa, meeting the specified requirements, strip roadway excavation is carried out underground in the coal mine. This eliminates the need for roof roadways and cross-layer boreholes, effectively reducing costs. After completing the strip roadway excavation as required, the optimal strip roadway is selected within the mining area. Then, the gas control mode for the remaining coal seam working faces is determined. This mode primarily depends on the angle between the direction of the minimum principal stress in the strata and the direction of the excavated strip roadway. Next, roof fracturing, coal seam fracturing, or in-seam gas extraction boreholes are designed within the strip roadway. Finally, based on the drilled roof fracturing, coal seam fracturing, or in-seam gas extraction boreholes, efficient negative pressure gas extraction is carried out underground in the coal mine. This invention is based on the geomechanical characteristics of coal seams in mining areas, and combines the advantages of existing coal mine gas disaster control technologies to reduce coal seam gas content to the minimum requirement of 8m³ during the development and preparation phases of the entire coal mine production life cycle. 3 The coal seam gas pressure is less than 0.74 MPa, which effectively ensures the succession of coal mining and ensures efficient and safe production in the production area, while reducing the cost of gas control and realizing integrated gas disaster management.

[0044] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0045] Example 1:

[0046] This embodiment provides a method for controlling gas disasters in coal mining areas using a combined mine-ground approach, including the following steps:

[0047] Step 1: Determine the relative spatial layout between the tunnel 2 to be excavated in the coal mining area and the coal seam mining face 1, such as... Figure 1 As shown;

[0048] Step 2: In the laboratory, measure the Protodyakonov hardness value f (unit is dimensionless) of the coal seam in the working face to be treated in the coal mine area. If the coal seam hardness value f≥1, it indicates that the coal seam hardness is good, the drilling construction of this coal seam is safe, the porosity is good, and the porosity rate is high; conversely, it indicates that the coal seam hardness is poor, the drilling construction of the coal seam has safety hazards, poor porosity, and low porosity rate.

[0049] Step 3: Based on the Protodyakonov hardness value f of the coal seam in the treatment working face obtained in Step 2, determine the arrangement layer of the L-shaped long horizontal borehole track 6 on the ground for the treatment of gas in the strip roadway 2 to be excavated. It is arranged in the coal seam or the roof of the coal seam in the strip roadway to be excavated.

[0050] If the coal seam hardness value f≥1, then the L-shaped long horizontal borehole track 6 needs to be laid in the coal seam of the strip roadway 2 to be excavated, such as... Figure 2 As shown, in order to reduce the damage to the coal reservoir during the drilling process of the horizontal section of this coal seam, clean water is used as the drilling fluid circulation body during the drilling process. At the same time, in order to meet the cuttings return effect during the drilling process, an appropriate amount of potassium chloride can be added to the clean water drilling fluid circulation body to increase the viscosity of the drilling fluid circulation body and thus improve the cuttings return efficiency.

[0051] If the coal seam hardness value f < 1, then the L-shaped long horizontal borehole track 6 needs to be laid in the roof 4 of the coal seam in the strip roadway 2 to be excavated, such as... Figure 3 As shown, the lithology of the coal seam roof 4 is usually mudstone. If the drilling trajectory is located in the mudstone, the mudstone is prone to expansion after hydration, which may lead to risks such as borehole diameter reduction and stuck drill. Therefore, under the premise of ensuring cost, a soil-based drilling fluid system is used as the drilling fluid circulation body during the drilling process. At the same time, an appropriate amount of anti-mudstone agent needs to be added to the drilling fluid to prevent risks such as mudstone diameter reduction and stuck drill. The subsequent fracturing construction of the L-shaped long horizontal borehole track 6 on the ground in the coal seam roof 4 of the strip roadway 2 to be excavated is cross-layer fracturing. In order to ensure the cross-layer fracturing effect, the distance between the L-shaped long borehole track 6 on the ground in the coal seam roof 4 of the strip roadway 2 to be excavated and the top of the coal seam 5 must be strictly controlled within the range of 0 to 1m.

[0052] Step 4: After the L-shaped horizontal borehole in Step 3 is completed according to the design requirements, the L-shaped horizontal borehole is flushed with solids-free drilling fluid until no cuttings are returned from the borehole. Then, logging instruments such as sonic logging, density logging, and borehole diameter logging are installed to obtain relevant formation stress parameters. Then, cluster perforation and hydraulic fracturing are carried out on the coal seam 5 or the roof 4. During the hydraulic fracturing process, effective microseismic monitoring is required. Microseismic monitoring with denser monitoring points is used to ensure efficient and accurate acquisition of the furthest radial extension distance S of the fracturing fracture 7 along the L-shaped horizontal borehole track 6 during the hydraulic fracturing process. Simultaneously, the boundary 10 of the hydraulic fracturing fracture extension range is effectively monitored in real time. Figure 4 As shown.

[0053] Step 5: After the completion of step 4, perform hydraulic fracturing followed by pressure release and blowout. Then, install the wellhead gas extraction device to extract gas from the roadway 2 to be excavated. The extraction process should continue until the gas level in the roadway 2 is reduced to the point where the surface well produces no gas or the coal seam gas content is below 8m³. 3 When the coal seam gas pressure is less than 0.74 MPa, strip roadway excavation is carried out underground in the coal mine.

[0054] Step 6: After the excavation of the aforementioned strip roadway 2 is completed, the magnitude and direction of the minimum horizontal principal stress of the coal seam in the mining area are calculated based on the relevant geostress parameters obtained in Step 4. Figure 6 As shown, based on the Protodyakonov hardness value f of the coal seam in the mining area measured in step 2, the gas control mode of the remaining coal seam mining face 1 is determined.

[0055] Step 61: If the angle α between the minimum principal stress direction 13 and the tunneling strip roadway direction 14 is greater than or equal to 45° and the coal seam hardness value f ≥ 1, then a near-horizontal long borehole along both sides of the strip roadway and hydraulic fracturing on the surface are designed to be constructed within the strip roadway for gas extraction from the coal seam working face 1. Figure 7 As shown. The spacing between each near-horizontal long borehole 17 is designed to be 180-200m, as... Figure 8 As shown, since the influence range of a single borehole in the surface hydraulic segmented fracturing is 90-100m, after the completion of the drilling of each of the designed near-horizontal long boreholes, the high-pressure fracturing pipeline 16 is then inserted into the surface through the L-shaped long horizontal borehole implemented in step 4. This is coordinated with the installation of relevant fracturing devices at the openings of each of the near-horizontal long boreholes 17 constructed in the underground strip roadways of the coal mine, to carry out segmented fracturing construction. Figure 7 As shown.

[0056] Step 62: If the angle α between the minimum principal stress direction 13 and the tunneling strip roadway direction 14 is greater than or equal to 45° and the coal seam hardness value f < 1, then the design is to construct a near-horizontal long borehole along both sides of the strip roadway to hydraulically fracture the coal seam roof or the coal seam 4 in stages with the surface for gas extraction at the coal seam recovery face 1. Figure 7 As shown. The spacing between each near-horizontal long borehole 17 is designed to be 180-200m, as... Figure 8 Therefore, after the completion of drilling of each of the aforementioned near-horizontal long boreholes, a fracturing high-pressure pipeline 16 is then inserted into the ground within the L-shaped long horizontal borehole implemented in step 4. This pipeline, along with the fracturing devices installed at the borehole openings of the near-horizontal long boreholes constructed within the underground strip roadways of the coal mine, facilitates segmented fracturing operations. Figure 7 As shown.

[0057] Step 63: If the angle α between the minimum principal stress direction 13 and the tunneling strip roadway direction 14 is less than 45°, then multi-branch near-horizontal boreholes of the coal seam 5 will be constructed on both sides of the strip roadway. Since the angle α between the minimum principal stress direction 13 and the tunneling strip roadway direction 14 is less than 45°, the propagation of the hydraulic segmented fracturing fracture 7 at the surface cannot be effectively controlled along both sides of the borehole. Therefore, surface hydraulic segmented fracturing is not designed to be carried out. Based on this situation, regardless of the magnitude of the coal seam hardness f, boreholes along both sides of the strip roadway are designed to be constructed within the strip roadway for gas extraction at the coal seam recovery face 1. Based on the length of each segment in the hydraulic segmented fracturing construction in step 4 above (e.g., Figure 5 The segment length H shown is typically designed to be 45-50 meters. A main borehole with multiple branches is designed at the center of this segment. The main borehole 11 is drilled to the furthest point S meters along the L-shaped horizontal borehole track of the hydraulic fracturing fracture 7 in step 4 above. Then, multiple branch boreholes are drilled at a depth S meters of the main borehole 11. The spacing between each branch borehole is designed to be 5-10 meters. Figure 5 As shown (the spacing between each branch hole mainly depends on the permeability of the coal seam matrix, which can be determined according to Darcy's law of seepage), each branch hole is drilled to the designed depth.

[0058] All the aforementioned near-horizontal long boreholes 17 or multi-branch near-horizontal main boreholes 12 drilled along coal seam 5 or coal seam roof 4 have been drilled to the furthest distance S meters along the L-shaped long horizontal borehole track of the hydraulic fracturing fracture 7 in step 4. Pneumatic directional drilling technology was used for construction. Due to the hydraulic segmented fracturing, the fracture network developed within the section of the fracturing fracture 7 extending radially along the L-shaped long horizontal borehole track 6 to the furthest point S meters. That is, the fracture network developed within the boundary 10 of the hydraulic segmented fracturing fracture expansion range. If a water-based drilling fluid system is used for drilling, risks such as leakage, difficulty in cuttings return, and stuck drill pipe are likely to occur. Then, each near-horizontal long borehole 17 or multi-branch near-horizontal borehole... A PVC pipe or fiberglass casing is driven into the main borehole 11 to a depth of S meters. A mixture of malathion and pure cement slurry is used to seal the annulus around the PVC pipe or fiberglass casing. The pure cement slurry is applied to the depth of S meters to ensure effective sealing of the furthest point of the fracturing fracture propagation (S meters). This reduces gas loss during pneumatic directional drilling or drilling fluid loss during conventional hydraulic drilling during subsequent near-horizontal long boreholes or multi-branch near-horizontal branch boreholes 12. Then, near-horizontal long borehole drilling continues at a depth of S meters in each near-horizontal long borehole 17 or multi-branch near-horizontal branch borehole 11, or side-drilling is used to create branch holes for multi-branch near-horizontal boreholes. Figure 5 As shown.

[0059] For the near-horizontal long borehole 17 drilled outside the boundary 10 of the hydraulic fracturing fracture extension range in step 61, a water-based drilling fluid circulation system is used for drilling.

[0060] The preferred drilling method for the near-horizontal long borehole 17 constructed outside the boundary 10 of the hydraulic segmented fracturing fracture expansion range in step 62 is as follows: if the design is to construct the near-horizontal long borehole 17 located on the coal seam roof 4, a water-based drilling fluid circulation system is adopted for drilling; if the design is to construct the near-horizontal long borehole 17 located on the coal seam 5, a pneumatic directional drilling process is adopted for drilling.

[0061] The preferred drilling method for the multi-branch near-horizontal borehole branch hole 11 in step 63 is as follows: Based on the coal seam hardness value obtained in step 2, if the coal seam hardness value f≥1, the multi-branch near-horizontal borehole branch hole 11 is drilled using a water-based drilling fluid circulation system; if the coal seam hardness value f<1, the multi-branch near-horizontal borehole branch hole 11 is drilled using a pneumatic directional drilling process.

[0062] Step 7, based on the completion of the construction in Step 6 above, drill a near-horizontal long borehole 17 along the coal seam or the roof of the coal seam, with a distance of S meters from the borehole opening (e.g., Figure 8(As shown) or multi-branch near-horizontal borehole main hole 12, a perforation device is installed inside and related equipment is used to perform perforation throughout the main hole section. This ensures that the near-horizontal long borehole 17 drilled along the coal seam or coal seam roof is connected to the surrounding hydraulic fracturing influence area from the borehole opening S meters away, or the multi-branch near-horizontal borehole main hole 12. This ensures that the gas convergence within the control range of the near-horizontal long borehole 17 drilled along the coal seam or coal seam roof is within the borehole opening S meters away, or the multi-branch near-horizontal borehole main hole 12, thereby enabling the extraction of gas stored in the coal seam mining face 1.

[0063] Therefore, based on the above steps and methods, it is possible to efficiently reduce the coal seam gas content to the minimum requirement of 8m³ for coal seam mining only during the development and preparation phases of the entire coal mine production life cycle. 3 The coal seam gas pressure is less than 0.74 MPa, which effectively ensures the succession of coal mining and ensures efficient and safe production in the production area, while reducing the cost of gas control and realizing integrated gas disaster management.

Claims

1. A method for controlling gas disasters in coal mining areas using a combined mine-ground approach, characterized in that, Includes the following steps: Step 1: Determine the relative spatial layout between the strip roadway to be excavated and the coal seam mining face in the coal mining area that needs to be treated. Step 2: Determine the Protodyakonov hardness value f of the coal seam in the working face to be treated in the coal mining area; Step 3: Based on the Protodyakonov hardness value f of the coal seam in the treatment working face obtained in Step 2, determine the layout layer of the L-shaped long horizontal borehole track for the treatment of gas in the strip roadway to be excavated. The layout layer is the coal seam or the roof of the coal seam in the strip roadway to be excavated. Step 4: After the L-shaped long horizontal borehole on the ground is completed according to the design requirements in Step 3, the L-shaped long horizontal borehole on the ground is flushed with solids-free drilling fluid until no rock cuttings are returned from the borehole. Then, sonic logging, density logging and caliber logging instruments are installed to obtain formation stress parameters. Then, cluster perforation and hydraulic fracturing are carried out in this coal seam or the roof of the coal seam. Microseismic monitoring is carried out at the same time as the hydraulic fracturing process. Step 5: After the completion of step 4, perform hydraulic fracturing followed by pressure release and blowout. Then, install the wellhead gas extraction device to extract gas from the roadway to be excavated. The extraction process should continue until the gas level in the roadway is reduced to the point where the surface well produces no gas or the coal seam gas content is below 8 mg / m³. 3 When the coal seam gas pressure is less than 0.74 MPa, strip roadway excavation is carried out in the coal mine. Step 6: After the excavation of the above-mentioned strip roadway is completed, calculate the magnitude and direction of the minimum horizontal principal stress of the coal seam in the mining area based on the stratum stress parameter information obtained in Step 4. At the same time, determine the gas control mode of the remaining coal seam mining face based on the Protodyakonov hardness value f of the coal seam in the mining area measured in Step 2. Step 7: Based on the completion of the construction in Step 6, perform full-section perforation within the main borehole of various near-horizontal long boreholes drilled along the coal seam or coal seam roof, within a section S meters from the borehole opening or the main borehole of multiple branch near-horizontal boreholes. This ensures communication between the main boreholes of various near-horizontal long boreholes drilled along the coal seam or coal seam roof and the surrounding hydraulic fracturing influence area, thereby ensuring the gas convergence within the control range of the main boreholes of various near-horizontal long boreholes drilled along the coal seam or coal seam roof, and thus enabling the extraction of gas stored in the coal seam mining face.

2. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 1, characterized in that, In step 2, if the coal seam hardness value f≥1, it indicates that the coal seam hardness is good, and the drilling construction of this coal seam is safe, has good porosity, and a high porosity rate; conversely, it indicates that the coal seam hardness is poor, and the drilling construction of the coal seam has safety hazards, poor porosity, and a low porosity rate.

3. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 2, characterized in that, In step 3, if the coal seam hardness value f≥1, then the L-shaped long horizontal borehole track on the ground is laid in the coal seam where the strip roadway to be excavated is to be treated. If the coal seam hardness value f < 1, then the L-shaped long horizontal borehole track on the ground will be laid in the roof of the coal seam of the strip roadway to be excavated. The distance between the L-shaped long borehole track on the ground in the roof of the coal seam of the strip roadway to be excavated and the top of the coal seam will be controlled within the range of 0 to 1m.

4. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 2, characterized in that, In step 4, microseismic monitoring with denser measuring points is used to ensure that the farthest radial extension distance S of the hydraulic fracturing crack along the L-shaped horizontal borehole track on the ground can be obtained efficiently and accurately during the hydraulic segmented fracturing construction process, while effectively monitoring the boundary of the hydraulic segmented fracturing crack extension range in real time.

5. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 2, characterized in that, Step 6 includes: Step 61: If the angle α between the direction of the minimum principal stress and the direction of the tunneling strip roadway is greater than or equal to 45° and the coal seam hardness value f≥1 in the mining area, then the design is to construct near-horizontal long boreholes along both sides of the strip roadway and perform hydraulic segmented fracturing on the surface to carry out gas extraction in the coal seam mining face. Step 62: If the angle α between the direction of the minimum principal stress and the direction of the tunneling strip roadway is greater than or equal to 45° and the coal seam hardness value f < 1, then the coal seam roof or the near-horizontal long borehole of the coal seam and the surface hydraulic segmented fracturing are designed to be constructed along both sides of the strip roadway to carry out gas extraction of the coal seam mining face. Step 63: If the angle α between the direction of the minimum principal stress and the direction of the tunneling strip is less than 45°, then multiple branch near-horizontal boreholes of the coal seam are constructed on both sides of the strip roadway, and boreholes along the coal seam are designed to be constructed on both sides of the strip roadway within the strip roadway to carry out gas extraction at the coal seam mining face.

6. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 5, characterized in that, In step 63, based on the design of a main hole at the center of each segment of the hydraulic fracturing construction in step 4 above, a multi-branch near-horizontal borehole is constructed. The main hole of the multi-branch near-horizontal borehole is drilled to the farthest distance S meters along the L-shaped long horizontal borehole track of the hydraulic fracturing in step 4 above. Then, multiple branch holes are opened at the depth S meters of the main hole of the multi-branch near-horizontal borehole. The spacing between each branch hole is designed to be 5 to 10 meters. Each branch hole is drilled until the designed hole depth.

7. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 5, characterized in that, In step 6, all near-horizontal long boreholes or multi-branch near-horizontal main boreholes drilled along the coal seam or coal seam roof are drilled to the farthest distance S meters along the radial extension of the hydraulic fracturing fracture in step 4 along the L-shaped long horizontal borehole track on the ground, and pneumatic directional drilling is used for construction.

8. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 7, characterized in that, PVC pipes or fiberglass casings are installed in the main boreholes of each near-horizontal long borehole or multi-branch near-horizontal borehole to a depth of S meters. Marl powder and pure cement slurry are used to seal the annulus around the PVC pipes or fiberglass casings. The pure cement slurry seals the borehole to a depth of S meters to ensure that the pure cement slurry can effectively seal the furthest distance S meters of the fracturing fracture propagation. This reduces gas loss during pneumatic directional drilling or drilling fluid loss during conventional hydraulic drilling during subsequent drilling of the branch holes of each near-horizontal long borehole or multi-branch near-horizontal borehole. Then, near-horizontal long borehole drilling continues at a depth of S meters in the main borehole of each near-horizontal long borehole or side-drilling is performed to open branch holes for multi-branch near-horizontal boreholes.

9. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 5, characterized in that, For the near-horizontal long borehole drilling outside the boundary of the hydraulic fracturing fracture extension range in step 61, a water-based drilling fluid circulation system is used.

10. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 5, characterized in that, For the drilling method of near-horizontal long boreholes constructed outside the boundary of the hydraulic segmented fracturing fracture in step 62, if the design is to construct near-horizontal long boreholes in the coal seam roof, a water-based drilling fluid circulation system is adopted; if the design is to construct near-horizontal long boreholes in the coal seam, a pneumatic directional drilling process is adopted.

11. The method for controlling gas disasters in coal mining areas with well-ground coordination as described in claim 5, characterized in that, Regarding the drilling method of the multi-branch near-horizontal borehole in step 63, based on the coal seam hardness value of the treatment working face obtained in step 2, if the coal seam hardness value f≥1, the multi-branch near-horizontal borehole is drilled using a water-based drilling fluid circulation system. If the coal seam hardness value f<1, the multi-branch near-horizontal borehole is drilled using a pneumatic directional drilling process.

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