Time-sharing cooperative efficient gas extraction method for fully mechanized caving face of thick coal seam

Abstract

The invention discloses a time-sharing cooperative efficient gas extraction method for a fully mechanized caving face of a thick coal seam, and relates to the technical field of coal mine gas extraction. S1, theoretical analysis before construction: determining coal seam geological conditions and gas storage and transportation rules; s2, gas extraction before recovery of the fully mechanized caving face of the thick coal seam; s3, gas extraction at the initial stage of recovery of the fully mechanized caving face of the thick coal seam: laying an extraction pipe at an upper corner, and performing supplementary extraction on coal seam gas; and S4, gas extraction is conducted in the middle stage of stoping of the fully mechanized caving face of the thick coal seam and after stoping, specifically, after the flow of gas extracted by the pre-extraction drill holes is attenuated, enhanced extraction is conducted on coal seam gas by adding the high-position drill holes, and meanwhile extraction pipes are laid at the upper corners to conduct supplementary extraction on the coal seam gas. According to the method, the extraction methods in different extraction periods are reasonably distributed, the gas time-sharing extraction method suitable for fully mechanized caving mining of the thick coal seam is formed, the gas extraction flow, the extraction concentration and the field gas extraction effect are effectively improved, and efficient gas extraction of the extra-thick high-gas coal seam is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal mine gas extraction, more particularly, it relates to a thick coal seam fully mechanized caving face gas time-sharing coordinated efficient extraction method. BACKGROUND

[0002] For thick coal seam fully mechanized caving face gas extraction, the current selection of gas extraction method in thick coal seam mining mainly includes: according to the location, there are mining layer, adjacent layer, goaf and surrounding rock extraction; according to the ground stress comparison, there are unloading pressure and unloading pressure extraction; according to the time comparison, there are pre-extraction before mining (tunneling), extraction during mining (tunneling) and post-mining extraction. However, due to the characteristics of thick coal seam, such as large coal seam thickness, high original gas content and high gas pressure, the gas extraction standard period will be prolonged. If only a single method is used to control coal seam gas, the effect is generally not ideal and cannot achieve the expected extraction effect. However, the combination of multiple methods may cause problems such as uncoordinated gas extraction method and unreasonable layout, which is counterproductive.

[0003] Therefore, the present application provides a thick coal seam fully mechanized caving face regional gas time-sharing coordinated efficient extraction method, which masters the theory of thick coal seam fully mechanized caving face gas extraction, comprehensively considers the advantages of different extraction methods at different mining periods, combines the pre-mining coal seam gas pre-extraction, upper corner gas extraction and coal seam pressure relief triple effect comprehensive extraction method, and forms a thick coal seam fully mechanized caving face regional gas time-sharing coordinated efficient extraction method. It has certain foresight, theoretical value and practical significance, and realizes the thick coal seam fully mechanized caving face regional gas time-sharing coordinated efficient extraction. SUMMARY

[0004] The purpose of the present application is to provide a thick coal seam fully mechanized caving face gas time-sharing coordinated efficient extraction method to solve the problems existing in the prior art, which can meet the requirements of thick coal seam fully mechanized caving face gas extraction, greatly reduce the cost of gas prevention and control, reduce carbon emissions, ensure the safety production of mine, and has important significance for energy transfer and sustainable development.

[0005] The above technical purpose of the present application is realized by the following technical scheme: a thick coal seam fully mechanized caving face gas time-sharing coordinated efficient extraction method, comprising the following steps:

[0006] S1: Theoretical analysis before construction: through the analysis of coal resource occurrence condition, hydrogeological condition, rock and geomechanics, the coal seam geological condition and gas storage and transportation rule of coal mine are determined;

[0007] S2: Gas extraction before thick coal seam fully mechanized caving face mining: the appropriate drilling is selected for hydraulic fracturing treatment, and the coal seam is pre-mining gas pre-extraction after the drilling hydraulic fracturing permeability is improved, the coal seam gas content is reduced, and the post-mining extraction pressure relief gas is prepared;

[0008] S3: Gas extraction in the early stage of mining of thick coal seam fully mechanized longwall face: By continuously pre-draining gas before mining, the gas content in this coal seam is reduced. Then, as the coal seam is mined, gas extraction pipes are laid in the upper corner to supplement the gas extraction of the coal seam.

[0009] S4: Gas extraction during and after the longwall mining of thick coal seams: After the gas flow rate from the pre-drainage boreholes decreases, gas extraction from the coal seam is enhanced by adding high-level boreholes. At the same time, gas extraction pipes are laid in the upper corners to supplement the gas extraction from the coal seam.

[0010] The present invention is further configured as follows: In step S2, a suitable borehole is selected for hydraulic fracturing. Fracturing begins from the bottom of borehole No. 1, with the final fracturing position 9m from the bottom of the borehole, and fracturing is performed once. Fracturing begins from the bottom of borehole No. 3, with the final fracturing position 30m from the bottom of the borehole, and fracturing is performed twice. The fracturing interval is 15m. The four boreholes in the track roadway are grouped together, and the spacing between the pre-drainage boreholes is arranged as 3 to 6m.

[0011] The present invention is further configured such that the pre-extraction borehole spacing is 3 to 6 m, and the specific spacing is determined by the actual borehole extraction radius.

[0012] The present invention is further configured to: conduct pre-mining gas drainage of the coal seam, connect to the drainage system for gas drainage, and monitor the gas drainage parameters in real time through the gas drainage monitoring system to dynamically grasp the changes in drainage flow rate.

[0013] The present invention is further configured such that: in step S4, a high-level drilling site is set up every 60 to 80 m to increase the number of high-level boreholes, and the spacing between high-level drilling sites is determined according to the actual borehole pressure difference distance and the extraction radius.

[0014] The present invention is further configured to: allocate different extraction methods at different mining stages, reduce the gas content of the coal seam by pre-fracturing hydraulic pressure before mining and setting up pre-extraction boreholes to extract coal seam gas, enhance the extraction of depressurized gas by high-level boreholes, and at the same time lay pipelines in the upper corner to supplement extraction, forming a gas extraction system with multiple extraction methods working together at different extraction and mining stages.

[0015] In summary, the present invention has the following beneficial effects:

[0016] (1) This invention combines the advantages and established methods of gas extraction in thick coal seam fully mechanized longwall mining, such as pre-fracturing, pre-drainage, and depressurization, at different mining stages. It integrates multiple extraction methods and rationally allocates them across different extraction periods, enabling synergistic effects of these methods at different times. This system reduces the gas content of the coal seam by performing pre-fracturing hydraulic pressure in the early stages of mining, in conjunction with pre-drainage boreholes. In the initial stage of mining, pre-drainage boreholes further reduce the gas content, and supplementary gas extraction is achieved through the use of buried pipes in the upper corner riser. During the mid-term and post-mining stages of fully mechanized longwall mining in thick coal seams, the flow rate of pre-drainage boreholes is reduced. This is combined with enhanced gas drainage and decompression through high-level boreholes. Simultaneously, additional drainage is achieved by laying underground pipes in the upper corner. This forms a gas drainage system that integrates multiple drainage methods at different stages, effectively solving the problems of poor drainage results from single measures and the cross-influence of multiple methods. It significantly reduces the cost and measures of technological gas prevention and control, improves gas drainage effectiveness, and provides important support for safe production in mines.

[0017] (2) This invention constructs a time layout for time-sharing coordinated decompression gas drainage during different mining periods, fully considers the decompression gas drainage conditions, and rationally allocates the drainage methods for different mining periods to form a time-sharing gas drainage method suitable for fully mechanized caving mining of thick coal seams. This effectively improves the gas drainage flow rate, drainage concentration and on-site gas drainage effect, and achieves the comprehensive evaluation results of the thick coal seam gas drainage system to meet the standards, ensuring safe and efficient mining.

[0018] (3) This invention achieves the extraction of coal seam gas in the area before mining by pre-extraction of large area, thereby reducing the coal seam gas content, which is in line with the current development trend of coal mines.

[0019] (4) This invention solves the problem of excessive gas levels in the upper corner of the working face and the return airway by implementing the upper corner vertical pipe buried pipe extraction technology in the goaf of the fully mechanized longwall mining face in thick coal seams, and provides a strong guarantee for safe mining of the working face.

[0020] (5) This invention takes into account three time periods: before the longwall mining of thick coal seam, the initial stage of longwall mining of thick coal seam, the middle stage of longwall mining of thick coal seam, and after longwall mining. It rationally arranges the gas extraction method in each time period and comprehensively considers the gas storage and transportation characteristics of different periods to determine the time-sharing and efficient gas extraction method for longwall mining of thick coal seam.

[0021] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0022] Figure 1 This is a flowchart of a time-sharing and coordinated high-efficiency gas extraction method for fully mechanized longwall mining faces in thick coal seams, according to the present invention.

[0023] Figure 2 This is a plan view of the pre-drilling borehole and the upper corner riser buried pipe of the present invention.

[0024] Figure 3 This is a plan view of the high-level drilling layout of the present invention;

[0025] Figure 4 This is a schematic diagram of the upper corner riser pipe buried in this invention.

[0026] In the diagram: 1. Cut-in hole; 2. Pre-drainage borehole; 3. Return airway; 4. Transport roadway; 5. Drainage pipeline; 6. Upper corner; 7. Sealing wall; 8. Drainage source; 9. Goaf; 10. High-level borehole; 11. High-level borehole pressure differential; 12. High-level drilling site; 13. Floor; 14. Cement support; 15. Buried suction pipe; 16. Connecting pipe; 17. Tee; 18. Bend; 19. Riser; 20. Screen hole; 21. Roof. Detailed Implementation

[0027] The following specific examples illustrate the implementation 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 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 illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0028] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0029] The following is in conjunction with the appendix Figures 1-4 The present invention will be described in further detail below.

[0030] Example: A time-sharing and efficient gas extraction method for fully mechanized longwall mining faces in thick coal seams, such as... Figures 1-4 As shown, the method includes the following steps:

[0031] S1: Theoretical analysis before construction: By analyzing the occurrence of coal resources, hydrogeological conditions, rock and geomechanical conditions, the geological conditions of coal seams and the gas storage and transportation laws of coal mines are determined.

[0032] S2: Gas drainage before mining in thick coal seam fully mechanized longwall face: After hydraulic fracturing and permeability enhancement of the borehole, pre-mining gas drainage is carried out in the coal seam to reduce the gas content and prepare for gas drainage and decompression after coal seam mining.

[0033] The drilling and fracturing process begins with hole No. 1, which is fracturing from the bottom of the hole until the final fracturing position is 9m from the bottom of the hole, and is fracturing once. Hole No. 3 is fracturing from the bottom of the hole until the final fracturing position is 30m from the bottom of the hole, and is fracturing twice, with a fracturing interval of 15m. The four holes in the track roadway are grouped together, and the subsequent fracturing holes are selected in the same manner as before.

[0034] During the pre-drainage borehole hydraulic fracturing, borehole inspection monitoring is used to determine the impact range of subsequent borehole hydraulic fracturing, providing a basis for subsequent borehole design.

[0035] The boreholes are located within the coal seam, with the final borehole located at the top of the coal seam (21), primarily for pre-drainage of this coal seam. The boreholes are located in the return airway (3) and transport roadway (4), with a pressure difference of more than 4 meters between them. A pre-drainage pipe is installed within the pre-drainage borehole (2), connecting to a flexible hose in the roadway. Each borehole (2) has a pre-installed tee for manual inspection, and the main roadway pipeline is equipped with monitoring devices for flow rate, concentration, and pressure.

[0036] The pre-drainage borehole 2 adopts a three-hole arrangement with a borehole spacing of 3 to 6 meters. The specific spacing is determined according to the actual borehole drainage radius. It is connected to the gas drainage system for gas drainage, and the gas drainage flow rate, concentration, negative pressure and other parameters of the surface well are monitored in real time through the gas drainage monitoring system to dynamically grasp the changes in drainage flow rate.

[0037] S3: Initial gas extraction in the longwall mining of thick coal seams: Through continuous pre-mining gas extraction, the gas content in this coal seam is reduced. Then, as the coal seam is mined, gas extraction pipes are laid in the upper corner to supplement the gas extraction.

[0038] A gas extraction system is installed at the upper corner of the longwall face. Extraction risers 19 are arranged along the bottom of the return airway at the tail end of the face. Branch pipes 5 extend continuously with the advancing direction of the longwall face, and a perforated riser 19 is installed every 12-25m along the branch pipes 5. The risers 19 use PE pipes with a diameter of 350-400mm as the extraction main pipe. The risers 19 are connected to the buried suction pipe 15 via bends 18. The buried suction pipe 15 is connected to a tee 17 via a connecting pipe 16, and finally connected to the branch pipes 5 via a tee 17. The perforated risers 19 are 1.5m-2.0m high, with 64 15mm diameter perforated screens 20 evenly arranged within a 0.8m range at their top. The bottom of the perforated risers 19 is supported by cement supports 14 to ensure that the perforated risers tilt due to mining activity, thus enabling uninterrupted extraction of gas from the goaf.

[0039] S4: Gas extraction during and after the longwall mining of thick coal seams: After the gas flow rate from the pre-drainage boreholes decreases, gas extraction from the coal seam is enhanced by adding high-level boreholes. At the same time, gas extraction pipes are laid in the upper corners to supplement the gas extraction from the coal seam.

[0040] The high-level drilling sites are located in the return airway 3, with one high-level drilling site 12 set up every 60-80m. The spacing between the high-level drilling sites is determined by taking into account the actual borehole pressure difference 11 and the extraction radius. They are arranged in two rows, with the upper row of holes 2.0m away from the bottom plate of the drilling site and the lower row of holes 1.5m away from the bottom plate of the drilling site.

[0041] A comprehensive gas drainage technology system for thick coal seam longwall faces integrates the advantages of multiple drainage methods, employing different drainage methods at different stages of mining. This system reduces coal seam gas content through pre-mining hydraulic fracturing, combined with pre-drainage boreholes, enhanced drainage of depressurized gas via high-level boreholes, and supplementary drainage by laying pipelines in the upper corners. This forms a gas drainage system that coordinates multiple drainage methods at different mining stages. The selection of gas drainage methods in thick coal seam mining mainly includes: by location (drainage from the mined seam, adjacent seams, goaf, and surrounding rock); by stress ratio (drainage before and after depressurization); and by time (pre-drainage before mining / excavation, drainage during mining / excavation, and post-mining drainage).

[0042] Taking full account of the advantages of various gas extraction methods, and through reasonable analysis of the mining period, a time-sharing and coordinated gas extraction method suitable for fully mechanized longwall mining of thick coal seams is formed, which effectively improves the gas extraction flow rate, extraction concentration and on-site gas extraction effect.

[0043] This invention fully considers the gas extraction conditions in coal mines. By rationally allocating extraction methods for different mining periods, it forms a time-sharing gas extraction method suitable for fully mechanized longwall mining of thick coal seams. This effectively improves the gas extraction flow rate, extraction concentration, and on-site gas extraction effect. It can effectively solve problems such as high original gas content, low coal seam permeability, and long extraction period to meet gas extraction standards in thick coal seams. Thus, it achieves efficient gas extraction from extra-thick, high-gas coal seams, thereby effectively reducing gas control costs, improving coal seam gas utilization, reducing carbon emissions, and providing an important guarantee for ensuring safe production in mines.

[0044] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A time-sharing and coordinated high-efficiency gas extraction method for fully mechanized longwall mining faces in thick coal seams, characterized in that, Includes the following steps: S1: Theoretical analysis before construction: By analyzing the occurrence of coal resources, hydrogeological conditions, rock and geomechanical conditions, the geological conditions of coal seams and the gas storage and transportation laws of coal mines are determined. S2: Gas drainage before mining of thick coal seam fully mechanized longwall face: At the beginning of drilling, a suitable borehole is selected for hydraulic fracturing. After hydraulic fracturing and permeability enhancement of the borehole, pre-mining gas drainage is carried out in the coal seam to reduce the gas content of the coal seam and prepare for gas drainage and decompression after coal seam mining. S3: Gas extraction in the early stage of mining of thick coal seam fully mechanized longwall face: By continuously pre-draining gas before mining, the gas content in this coal seam is reduced. Then, as the coal seam is mined, gas extraction pipes are laid in the upper corner to supplement the gas extraction of the coal seam. S4: Gas extraction during and after the longwall mining of thick coal seams: After the gas flow rate from the pre-drainage boreholes decreases, gas extraction from the coal seam is enhanced by adding high-level boreholes. At the same time, gas extraction pipes are laid in the upper corners to supplement the gas extraction from the coal seam.

2. The method for efficient gas extraction in a fully mechanized longwall face of a thick coal seam according to claim 1, characterized in that: In step S2, suitable boreholes are selected for hydraulic fracturing. Fracturing begins at borehole 1 from the bottom of the borehole, with the final fracturing position 9m from the bottom of the borehole, and fracturing is performed once. Fracturing begins at borehole 3 from the bottom of the borehole, with the final fracturing position 30m from the bottom of the borehole, and fracturing is performed twice, with a fracturing interval of 15m. The four boreholes in the track roadway are grouped together, and the spacing between the pre-drainage boreholes is arranged at 3 to 6m.

3. The method for efficient gas extraction in a fully mechanized longwall face of a thick coal seam according to claim 2, characterized in that: The pre-drainage borehole spacing is 3 to 6 meters, and the specific spacing is determined by the actual borehole drainage radius.

4. The method for efficient gas extraction in a fully mechanized longwall face of a thick coal seam according to claim 2, characterized in that: Pre-mining gas drainage is carried out in the coal seam, and gas drainage is carried out by connecting to the drainage system. The gas drainage parameters are monitored in real time through the gas drainage monitoring system to dynamically grasp the changes in drainage flow rate.

5. The method for efficient gas extraction in a fully mechanized longwall face of a thick coal seam according to claim 1, characterized in that: In step S4, a high-level drilling site is set up every 60-80m to increase the number of high-level boreholes. At the same time, the spacing between high-level drilling sites is determined according to the actual borehole pressure difference distance and the extraction radius.

6. The method for efficient gas extraction in a fully mechanized longwall face of a thick coal seam according to claim 1, characterized in that: in Different extraction methods are allocated for different mining periods. Pre-fracturing of coal seam gas is carried out by hydraulic pressure before mining, and pre-drainage boreholes are set up to extract coal seam gas to reduce the coal seam gas content. High-level boreholes are used to enhance the extraction of depressurized gas. At the same time, pipelines are laid in the upper corner to supplement extraction, forming a gas extraction system with multiple extraction methods working together for different mining periods.

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