A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines

Abstract

The present invention belongs to the field of coal mine gas drainage, and relates to a three-dimensional full-cycle gas drainage method for directional borehole groups in coal mines. First, in the development or preparation roadway exposed in the coal mine, a parallel directional main borehole group along the strike or dip of the mining face is arranged. Parallel downward branch borehole groups are arranged at a certain distance interval for each main borehole. A large-flow hydraulic punching permeability enhancement measure is implemented for each branch borehole. Before the operation of the mining and excavation face, all parallel downward branch borehole groups conduct advance pre-drainage of the gas in the original coal body in the covered area. During the operation of the mining and excavation face, the parallel downward branch borehole groups that are not damaged conduct continuous drainage of the gas in the coal body in the covered area. After the operation of the mining face, the parallel directional main borehole group conducts pressure-relief drainage of the gas in the goaf. The present invention can effectively solve the problem that the existing directional boreholes in coal mines have a single use and are damaged by mining influence and cannot be continuously utilized, achieve the goal of multi-purpose use of directional borehole groups, and effectively guarantee the safety of mining and excavation operations in the mine.

Description

Technical Field

[0001] The invention belongs to the field of coal mine gas drainage, and relates to a three-dimensional full-cycle gas drainage method for directional borehole groups in coal mines Background Technique

[0002] A large amount of gas gushing in the mine will seriously affect the safe production of coal mines, and efficient gas drainage is the fundamental method to realize mine gas control

[0003] At present, the main method for pre-draining coal seam gas in China is to use underground boreholes for pre-drainage. Among the common measures for underground borehole pre-drainage, directional long boreholes have been gradually promoted in recent years. However, in view of the characteristics of soft and low-permeability coal seams in high-gas or outburst coal mines in China, the single directional long borehole has a small drainage radius and low efficiency, and it is difficult to achieve the standard of coal seam gas drainage in a short time. At the same time, the directional long borehole cannot be continuously used after being damaged by mining influence. In recent years, the technology of hydraulic punching and pressure relief for cross-cut boreholes has become increasingly mature and has been promoted and applied in a small range. Therefore, combining directional long boreholes and hydraulic punching in coal mines and optimizing the layout of directional borehole groups is of great significance for improving the gas control effect of the whole life cycle of the mining and excavation working face

[0004] According to the publicly available technical materials, there is no feasible gas drainage method combining directional long boreholes and hydraulic punching in coal mines in the existing technology of China Summary of the Invention

[0005] In view of this, the purpose of the invention is to provide a three-dimensional full-cycle gas drainage method for directional borehole groups in coal mines, aiming at the technical problems that the current directional boreholes in coal mines have a single use and cannot be continuously used after being damaged by mining influence, realizing the goal of multi-purpose use of directional borehole groups and effectively ensuring the safety of mine mining and excavation operations

[0006] To achieve the above purpose, the invention provides the following technical solution: A three-dimensional full-cycle gas drainage method for directional borehole groups in coal mines, including the following steps

[0007] S1. First, in the development or preparation roadway exposed in the coal mine, arrange a parallel directional main borehole group along the strike or dip of the coal mining face

[0008] S2. Arrange a parallel downward branch borehole group at a certain distance for each main borehole, and implement a large-flow hydraulic punching and permeability enhancement measure for each branch borehole

[0009] S3. Before the operation of the mining and excavation working face, all parallel downward branch borehole groups pre-drain the gas in the original coal body in the covered area

[0010] During the operation of the working face, the intact parallel downward branch borehole groups in the non - damaged area continuously extract the gas from the coal body in the covered area, and after the operation of the mining face, the parallel directional main borehole groups extract the gas in the goaf under pressure relief.

[0011] Optionally, the opening positions of the directional boreholes are arranged in the development or preparatory roadways exposed in the underground coal mine, and the coal body in the mining area is pre - extracted before the excavation roadway is driven.

[0012] Optionally, the parallel directional main borehole groups are arranged parallel to the dip of the mining face in the development roadway and parallel to the strike of the mining face in the preparatory roadway.

[0013] Optionally, the layer position of the parallel directional main borehole groups is selected in the stable rock strata in the bending and subsidence zone of the coal seam roof, avoiding the caving zone and fracture zone of the coal seam roof.

[0014] Optionally, the downward branch borehole groups are arranged parallel at a certain interval along each main borehole. The boreholes should penetrate the coal seam and enter the floor by no less than 3m. The borehole diameter is generally not less than 200mm, and the borehole spacing should be determined according to the coal seam and gas occurrence conditions.

[0015] Optionally, the downward branch borehole groups need to implement the measure of large - flow hydraulic punching for permeability enhancement. In the coal hole section of the branch boreholes, large - flow hydraulic punching is carried out to relieve the pressure and enhance the permeability of the original coal body. The punching pressure is generally 30 - 50MPa, and the punching flow is generally not less than 100L / min.

[0016] Optionally, before the operation of the mining face, all the parallel downward branch borehole groups pre - extract the gas from the original coal body in the covered area to ensure that the gas extraction from the coal seam in the mining area meets the standard.

[0017] Optionally, during the operation of the mining face, the parallel downward branch borehole groups are partially damaged by mining influence. The intact parallel downward branch borehole groups continuously extract the gas from the pre - extracted coal body in the covered area to ensure the gas extraction effect of the coal seam in the mining area.

[0018] Optionally, after the operation of the mining face, the parallel downward branch borehole groups located in the goaf are completely damaged by mining influence, but the parallel directional main borehole groups located in the stable rock strata of the coal seam roof form a gas flow channel to extract the gas in the goaf under pressure relief, reducing the gas emission from the goaf in the return airway during the mining process.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. The three - dimensional full - cycle gas extraction method of directional borehole groups in the underground coal mine of the present invention uses the development or preparatory roadways exposed in the underground coal mine to arrange the directional borehole groups along the strike or dip of the mining face in advance, which can achieve the advanced and efficient treatment of the gas in the coal body of the mining area in terms of time and space.

[0021] 2. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to the present invention, where the directional main borehole groups are arranged in the harder rock strata in the bending subsidence zone of the coal seam roof, which can ensure the integrity of the boreholes throughout the entire mining and excavation cycle. Some of the branch boreholes can also be retained after the mining operation, thereby continuing to achieve gas drainage in the goaf.

[0022] 3. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to the present invention, where a large-flow hydraulic punching and permeability enhancement measure is implemented for each branch borehole, ensuring the hole-forming effect of the coal hole section of the branch borehole. The borehole penetrates 3 m into the coal seam floor, enabling the drainage of gas in the floor surrounding rock and also retaining the residues that fall off the borehole wall during construction and later stages, keeping the coal hole section unobstructed, and better ensuring the gas drainage effect of the borehole throughout the cycle.

[0023] 4. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to the present invention, where the layout of the roof grid boreholes can prompt the timely collapse of the goaf roof, facilitating the management of the goaf roof and the treatment of gas in the upper corner.

[0024] 5. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to the present invention, where the directional main and downward branch borehole groups can achieve the purpose of multiple uses of borehole groups, realizing the full-life cycle drainage of pre-extraction of coal seam gas in the covered area, gas drainage during mining, and post-mining pressure relief drainage, improving the utilization rate of directional boreholes and reducing the cost of gas control.

[0025] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0027] Figure 1 is the overall drainage schematic diagram of the present invention;

[0028] Figure 2 is Figure 1 the sectional view taken along A-A1 of

[0029] Figure 3 is Figure 1 the sectional view taken along B-B1 of

[0030] Figure 4 is Figure 1 the sectional view taken along C-C1 of

[0031] Figure 5 For Figure 1 the D-D1 sectional view.

[0032] Reference numerals: development roadway 1, preparatory roadway 2, extraction roadway 3, roof 4, coal seam 5, floor 6, bending subsidence zone 7, fracture zone 8, caving zone 9, goaf 10, dry hole 11, branch borehole 12, grid branch borehole 13. Specific embodiments

[0033] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0034] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation on the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0035] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Please refer to Figures 1 to 5 , which is a three-dimensional full-cycle gas drainage method for a directional borehole group in a coal mine, including the following steps: S1, first, in the development or preparatory roadway 2 exposed in the coal mine, arrange a parallel directional main borehole group along the strike or dip of the mining face;

[0037] S2, arrange a group of parallel downward branch boreholes 12 at a certain distance interval for each main borehole, and implement a large-flow hydraulic punching and permeability enhancement measure for each branch borehole 12;

[0038] S3. Before the operation of the excavation working face, all 12 groups of parallel downward branch boreholes pre-drain the gas in the original coal body in the covered area in advance.

[0039] S4. During the operation of the excavation working face, the 12 groups of parallel downward branch boreholes that are not damaged continuously drain the gas in the coal body in the covered area. After the operation of the longwall working face, the parallel directional main borehole group drains the gas in the goaf 10 for pressure relief.

[0040] In the present invention, the opening positions of the directional boreholes are arranged in the development or preparatory roadway 2 exposed in the coal mine underground. Before the excavation roadway is driven, the gas in the coal body in the excavation area is pre-drained. The parallel directional main borehole group is arranged parallel to the inclination of the longwall working face in the development roadway 1 and parallel to the strike of the longwall working face in the preparatory roadway 2. The horizon of the parallel directional main borehole group is selected in the stable rock stratum of the bending subsidence zone 7 of the coal seam 5 roof 4, avoiding the caving zone 9 and fracture zone 8 of the coal seam 5 roof 4. The 12 groups of downward branch boreholes are arranged in parallel at a certain interval along each main borehole. The boreholes should penetrate the coal seam 5 and enter the floor 6 by no less than 3 m. The borehole diameter is generally not less than 200 mm. The borehole spacing should be determined according to the coal seam 5 and the gas occurrence situation. The 12 groups of downward branch boreholes need to implement the measure of increasing permeability by large-flow hydraulic punching. In the coal hole section of the branch boreholes 12, large-flow hydraulic punching is adopted to relieve the pressure and increase the permeability of the original coal body. The punching pressure is generally 30 - 50 MPa, and the punching flow is generally not less than 100 L / min. Before the operation of the excavation working face, all 12 groups of parallel downward branch boreholes pre-drain the gas in the original coal body in the covered area in advance to ensure that the gas drainage in the coal seam 5 in the excavation area meets the standard. During the operation of the excavation working face, part of the 12 groups of parallel downward branch boreholes are damaged by mining influence. The undamaged 12 groups of parallel downward branch boreholes continuously drain the gas in the pre-drained coal body in the covered area to ensure the gas drainage effect of the coal seam 5 in the excavation area. After the operation of the longwall working face, the 12 groups of parallel downward branch boreholes located in the goaf 10 are completely damaged by mining influence, but the parallel directional main borehole group located in the stable rock stratum of the coal seam 5 roof 4 forms a gas flow channel to drain the gas in the goaf 10 for pressure relief, reducing the gas emission from the goaf 10 in the excavation roadway 3 during the longwall mining process.

[0041] Specific Embodiment 1

[0042] A three-dimensional full-cycle gas drainage method for directional borehole groups in coal mine underground, and the specific method is as follows:

[0043] In the preparatory roadway 2, large-diameter directional boreholes are constructed perpendicular to the roadway, with a diameter of more than 200 mm. After the boreholes enter the selected rock stratum, they continue to be constructed parallel to the coal seam; branch boreholes are constructed downward at intervals of 20 - 30 m. The boreholes penetrate the coal seam and enter the floor by 3 m, which is used to extract the gas in the surrounding rock of the floor 6. It can also retain the residues that fall off the borehole wall during construction and in the later stage, ensuring the smoothness of the coal borehole section and the gas extraction effect.

[0044] In the coal borehole section of the branch borehole, large-flow hydraulic punching is adopted to relieve the pressure and enhance the permeability of the original coal body. The punching pressure is 30 - 50 MPa, and the punching flow rate is greater than 100 L / min; after the completion of each borehole's dry hole 11 and the branch borehole, they are sealed and connected for gas extraction, and finally a regional three-dimensional grid borehole layout is formed, as Figure 1 shown.

[0045] After combined extraction, the pre-extraction branch borehole 12 pre-extracts the coal body before coal mining, as Figure 2 shown; after the pre-extraction reaches the standard, during coal mining, the branch borehole 12 relieves the pressure and extracts gas from the mining face; after coal mining, the retained grid branch borehole 13 extracts the gas from the goaf 10, as Figure 3 shown; all the main and branch boreholes serve the whole cycle of pre-mining, in-mining and post-mining of the coal seam in the whole area.

[0046] In this embodiment, the boreholes can only be constructed after the preparatory roadway is excavated. Moreover, as the working face advances, only the boreholes within the current working face will change from the pre-extraction state to pressure-relief gas extraction, without affecting other working faces.

[0047] Specific embodiment 2,

[0048] A three-dimensional full-cycle gas extraction method for directional borehole groups in coal mines is as follows:

[0049] In the development roadway 1, large-diameter directional boreholes are constructed perpendicular to the roadway, with a diameter of more than 200 mm. After the boreholes enter the selected rock stratum, they continue to be constructed parallel to the coal seam; branch boreholes are constructed downward at intervals of 20 - 30 m. The boreholes penetrate the coal seam and enter the floor by 3 m, which is used to extract the gas in the surrounding rock of the floor 6. It can also retain the residues that fall off the borehole wall during construction and in the later stage, ensuring the smoothness of the coal borehole section and the gas extraction effect.

[0050] In the coal borehole section of the branch borehole, large-flow hydraulic punching is adopted to relieve the pressure and enhance the permeability of the original coal body. The punching pressure is 30 - 50 MPa, and the punching flow rate is greater than 100 L / min; after the completion of each borehole's dry hole and the branch borehole, they are sealed and connected for gas extraction, and finally a regional three-dimensional grid borehole layout is formed, as Figure 1 shown.

[0051] After combined extraction, the branch borehole 12 pre-extracts the coal body before coal mining, as Figure 4As shown; after the pre-drainage reaches the standard, during the coal mining period, the grid branch boreholes 13 carry out pressure-relief drainage on the mining face; after coal mining, the remaining grid branch boreholes 14 carry out gas drainage on the goaf 10, as Figure 5 shown; all main and branch boreholes serve the whole cycle of pre-mining, in-mining and post-mining of the coal seam in the whole area.

[0052] In this embodiment, the drainage boreholes can be constructed successively as the development roadway is driven. The pre-drainage time is earlier than that in Embodiment 1. As the working face advances, the boreholes entering the goaf are changed from pre-drainage to pressure-relief drainage, and the corresponding areas of the other working faces also become pressure-relief drainage. However, since the drainage time of all working faces is the same, it will not affect the evaluation of the drainage compliance of this working face.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines, characterized in that It includes the following steps: S1. First, in the development or preparatory roadway exposed underground in a coal mine, a group of parallel directional main boreholes along the strike or dip of the coal mining face is arranged. The group of parallel directional main boreholes is arranged parallel to the dip of the coal mining face in the development roadway and parallel to the strike of the coal mining face in the preparatory roadway. The horizon of the group of parallel directional main boreholes is selected in the stable rock stratum of the bending subsidence zone of the coal seam roof, avoiding the caving zone and fracture zone of the coal seam roof. S2. A group of parallel downward branch boreholes is arranged at a certain distance interval for each main borehole, and a large-flow hydraulic punching permeability enhancement measure is implemented for each branch borehole. A large-flow hydraulic punching permeability enhancement measure needs to be implemented for the group of parallel downward branch boreholes. In the coal hole section of the branch boreholes, large-flow hydraulic punching is adopted to relieve the pressure and enhance the permeability of the original coal body. S3. Before the operation of the mining and excavation working face, all the groups of parallel downward branch boreholes pre-drain the gas in the original coal body in the covered area in advance. S4. When the mining and excavation working face is operating, the groups of parallel downward branch boreholes that are not damaged continuously drain the gas in the coal body in the covered area, and after the operation of the coal mining face, the group of parallel directional main boreholes drains the gas in the goaf under pressure relief.

2. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to claim 1, characterized in that: The opening positions of the directional boreholes are arranged in the development or preparatory roadway exposed underground in a coal mine, and the gas in the coal body in the mining and excavation area is pre-drained before the excavation of the mining and excavation roadway.

3. A three-dimensional full-cycle gas drainage method for directional borehole groups in coal mines according to claim 1, characterized in that: The group of parallel directional main boreholes is arranged parallel to the dip of the coal mining face in the development roadway and parallel to the strike of the coal mining face in the preparatory roadway.

4. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to claim 1, characterized in that: The horizon of the group of parallel directional main boreholes is selected in the stable rock stratum of the bending subsidence zone of the coal seam roof, avoiding the caving zone and fracture zone of the coal seam roof.

5. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to claim 1, characterized in that: The group of parallel downward branch boreholes is arranged parallel at a certain distance interval for each main borehole. The boreholes should penetrate the coal seam and enter the floor by no less than 3 m, the borehole diameter is not less than 200 mm, and the borehole spacing should be determined by investigating the coal seam and gas occurrence conditions.

6. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to claim 1, characterized in that: A large-flow hydraulic punching permeability enhancement measure needs to be implemented for the group of parallel downward branch boreholes. In the coal hole section of the branch boreholes, large-flow hydraulic punching is adopted to relieve the pressure and enhance the permeability of the original coal body. The punching pressure is 30 - 50 MPa, and the punching flow rate is not less than 100 L / min.

7. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to claim 1, characterized in that: Before the operation of the mining and excavation working face, all the groups of parallel downward branch boreholes pre-drain the gas in the original coal body in the covered area in advance to ensure that the gas drainage in the coal seam in the mining and excavation area meets the standard.

8. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to claim 1, characterized in that: When the mining and excavation working face is operating, the groups of parallel downward branch boreholes are partially damaged due to the influence of mining. The groups of parallel downward branch boreholes that are not damaged continuously drain the gas in the pre-drained coal body in the covered area to ensure the gas drainage effect in the coal seam in the mining and excavation area.

9. A three-dimensional full-cycle gas drainage method for directional borehole groups in underground coal mines according to claim 1, characterized in that: After the operation of the coal mining face, the groups of parallel downward branch boreholes located in the goaf are completely damaged due to the influence of mining, but the group of parallel directional main boreholes located in the stable rock stratum of the coal seam roof forms a gas flow channel to drain the gas in the goaf under pressure relief, reducing the gas emission from the goaf in the mining roadway during the coal mining process.

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