Mine composite disaster prevention and control method and system based on well-ground collaborative fracturing and extraction

Abstract

The invention provides a mine composite disaster prevention and control method and system based on well-ground collaborative fracturing and extraction. The method comprises the steps that a high-position overlying strata key layer and a low-position overlying strata key layer in overlying strata are identified based on mine geological conditions; an L-shaped double-step horizontal well is established according to the key layer, and segmented hydraulic fracturing is conducted on well sections, located in the high-position overlying strata key layer and the low-position overlying strata key layer, of the L-shaped double-step horizontal well; the straight well section of the L-shaped double-step horizontal well extends downwards to be communicated with an underground operation roadway, and a high-pressure fluid conveying channel leading to the underground roadway is built; the drill holes formed in the underground roadway are subjected to segmented hydraulic fracturing through ground fracturing equipment; and the fractured L-shaped double-step horizontal well and the fractured drill hole in the underground roadway are connected to a coal mine extraction system, and grid-connected collaborative extraction is carried out. According to the technical scheme, large-area pressure relief and permeability increase of the coal seam are achieved, the extraction efficiency is improved, and safe and efficient production of a mine is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mine gas and mine pressure control, and particularly relates to a mine compound disaster prevention method and system based on well-ground collaborative fracturing and extraction. BACKGROUND

[0002] With the extension of coal mining to the deep part, the coal rock mass gradually presents the geological characteristics of high ground stress, high gas pressure, high energy storage and low permeability. The complex geological environment highlights the interaction between various dynamic disasters in coal mines, and various disaster-causing factors interweave with each other, mutually induce and mutually strengthen in the process of accident incubation, occurrence and development, and present the characteristics of compound dynamic disasters. Mainly reflected in that the low permeability of coal seam significantly weakens the gas dissipation capacity, and is easy to form a local gas enrichment area. At the same time, the high ground stress environment induces stress concentration, which not only aggravates the risk of surrounding rock instability after mining disturbance, but also significantly increases the occurrence frequency and intensity of compound dynamic disasters such as coal and gas outburst and rock pressure through the energy accumulation-release mechanism. Compared with single dynamic disaster, the threshold of compound dynamic disaster may be lower, the disaster occurrence intensity may be greater and more violent, which makes the occurrence mechanism more complex and the prediction and prevention more difficult. Coal and gas outburst, rock pressure dynamic disaster and its derivative disaster seriously restrict the safe and efficient development of deep coal resources. Modern prevention and control system mainly adopts two types of core technologies: one is the disaster prevention and control technology taking underground drilling as the core, which improves the permeability of coal seam and strengthens the extraction effect in the local area through directional long drilling or ordinary drilling; the other is the disaster prevention and control technology taking surface well as the core, which establishes a straight well-horizontal well combined extraction system on the ground to destroy the energy storage structure of coal rock in a large range, weaken the energy basis of rock pressure, and reduce the risk of coal and gas outburst and rock pressure disaster.

[0003] At present, the underground disaster prevention and control technology system taking underground drilling as the core has the advantages of uniform treatment effect, high flexibility, etc., but is limited by the underground space, resulting in low equipment power and limited treatment range. Although the disaster prevention and control technology system taking surface well as the core is not restricted by space, has large equipment power and wide influence range, it is easily affected by geological structure and is easy to cause treatment blank area in local area. Single use of the disaster prevention and control technology system taking surface well as the core or the disaster prevention and control technology system taking underground drilling as the core cannot realize effective prevention and control of deep mine disaster. Therefore, it is urgent to provide a mine compound disaster prevention and control scheme based on well-ground collaborative fracturing and extraction. SUMMARY

[0004] The present application provides a mine compound disaster prevention method and system based on well-ground collaborative fracturing and extraction, to at least solve the technical problem that effective prevention and control of deep mine disaster cannot be realized.

[0005] The first aspect embodiment of the present application provides a mine composite disaster prevention method based on well-ground cooperative fracturing and extraction, which comprises: According to the high-position overburden key layer and the low-position overburden key layer, an L-shaped double-step horizontal well is established from the ground, and the well section of the L-shaped double-step horizontal well in the high-position overburden key layer and the low-position overburden key layer is subjected to staged hydraulic fracturing. The vertical well section of the L-shaped double-step horizontal well is extended downward to be connected with the underground operation roadway, and a high-pressure fluid conveying channel from the ground fracturing equipment to the underground roadway is established; Using the high-pressure fluid conveying channel, the boreholes arranged in the underground roadway are subjected to staged hydraulic fracturing by the ground fracturing equipment; The L-shaped double-step horizontal well after fracturing and the boreholes in the underground roadway after fracturing are connected to the coal mine extraction system for network cooperation and extraction.

[0006] Preferably, the high-position overburden key layer and the low-position overburden key layer in the overburden layer are identified based on the mine geological conditions, which comprises: The lower part of the bending subsidence zone of the area where the mine is located is taken as the high-position overburden key layer, and the lower part of the water flowing fractured zone of the area where the mine is located is taken as the low-position overburden key layer.

[0007] Further, the L-shaped double-step horizontal well is an L-shaped double-step horizontal well penetrating the high-position overburden key layer and the low-position overburden key layer.

[0008] Further, the well section of the L-shaped double-step horizontal well in the high-position overburden key layer and the low-position overburden key layer is subjected to staged hydraulic fracturing, which comprises: The L-shaped double-step horizontal well is subjected to staged hydraulic fracturing by using a large-displacement staged hydraulic sand fracturing process; Wherein, the interval of staged fracturing is 60-100 meters.

[0009] Further, the high-pressure fluid conveying channel comprises a ground fracturing equipment high-pressure outlet, a fracturing wellhead, a well bottom end extending to the underground roadway, and a high-pressure connection device connected in sequence, and the high-pressure connection device is connected with the underground borehole.

[0010] Further, the boreholes arranged in the underground roadway are subjected to staged hydraulic fracturing, which comprises: The boreholes in the underground roadway are subjected to staged hydraulic fracturing by using a directional perforation staged fracturing process; Wherein, the fracturing fluid in the directional perforation staged fracturing process is clear water, and the fracturing section interval is 50-80 meters.

[0011] Further, the borehole in the underground roadway comprises a directional long borehole and / or a common borehole. When the hardness of the coal seam is greater than or equal to the first threshold value, the borehole is arranged in the coal seam. When the hardness of the coal seam is less than the first threshold value, the borehole is arranged in the roof or floor of the coal seam, and the distance between the horizontal section track of the borehole and the roof or floor of the coal seam is in the range of 2-5 meters.

[0012] Preferably, the method further comprises: The borehole after fracturing is detected by using the borehole transient electromagnetic profile detection technology, and the influence range and effect of hydraulic fracturing are evaluated.

[0013] Preferably, the connecting of the L-shaped double-step horizontal well after fracturing and the borehole in the underground roadway after fracturing to the coal mine extraction system comprises: The L-shaped double-step horizontal well is connected to the low negative pressure extraction pipeline laid in the roadway through the extraction pipeline, and the goaf gas during and after the mining is continuously extracted; The borehole in the underground roadway is connected to the high negative pressure extraction pipeline laid in the roadway through the extraction pipeline, and the regional coal seam gas is extracted.

[0014] The second aspect embodiment of the application proposes a mine composite disaster prevention and control system based on well-ground collaborative fracturing and extraction, comprising: The identification module is configured to identify a high-position overburden key layer and a low-position overburden key layer in the overburden based on the mine geological conditions; The establishment module is configured to establish an L-shaped double-step horizontal well from the ground according to the high-position overburden key layer and the low-position overburden key layer, and to perform segmented hydraulic fracturing on the well section of the L-shaped double-step horizontal well located in the high-position overburden key layer and the low-position overburden key layer; The through module is configured to extend the vertical section of the L-shaped double-step horizontal well downward to the underground operation roadway, and to establish a high-pressure fluid delivery channel from the ground fracturing equipment to the underground roadway; The fracturing module is configured to use the high-pressure fluid delivery channel to perform segmented hydraulic fracturing on the borehole arranged in the underground roadway by the ground fracturing equipment; The extraction module is configured to connect the L-shaped double-step horizontal well after fracturing and the borehole in the underground roadway after fracturing to the coal mine extraction system for networked collaborative extraction.

[0015] The technical scheme provided by the embodiments of the application at least brings the following beneficial effects: The application provides a mine composite disaster prevention method and system based on well-ground collaborative fracturing and extraction. The method comprises the following steps: identifying a high-position overburden key layer and a low-position overburden key layer in overburden strata based on mine geological conditions; establishing an L-shaped double-bench horizontal well according to the high-position overburden key layer and the low-position overburden key layer from the ground; performing segmented hydraulic fracturing on a well section of the L-shaped double-bench horizontal well located in the high-position overburden key layer and the low-position overburden key layer; extending a vertical well section of the L-shaped double-bench horizontal well downward to a roadway in a mine and establishing a high-pressure fluid conveying channel from a ground fracturing device to the roadway; performing segmented hydraulic fracturing on a borehole arranged in the roadway in the mine by the ground fracturing device through the high-pressure fluid conveying channel; and connecting the L-shaped double-bench horizontal well after fracturing and the borehole after fracturing in the roadway to a coal mine extraction system for network connection and collaborative extraction. The technical scheme provided by the application realizes large-area pressure relief and permeability improvement of a coal seam, improves extraction efficiency and ensures safe and efficient production of a mine.

[0016] Additional aspects and advantages of the application will be set forth in part in the description that follows, and in part will become apparent to those having ordinary skill in the art upon examination of the following or can be learned from practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0017] The above and / or additional aspects and advantages of the application will become apparent and be readily appreciated from the following description, taken in conjunction with the accompanying drawings, in which: Figure 1 A flow chart of a mine composite disaster prevention method based on well-ground collaborative fracturing and extraction according to an embodiment of the application is provided. Figure 2 A structure diagram of a mine composite disaster prevention system based on well-ground collaborative fracturing and extraction according to an embodiment of the application is provided. Figure 3 A structure diagram of a mine composite disaster prevention system based on well-ground collaborative fracturing and extraction according to an embodiment of the application is provided. DETAILED DESCRIPTION

[0018] Embodiments of the application are described in detail below with reference to the accompanying drawings, in which the same or similar components have the same reference numbers throughout. The embodiments described below are examples for explaining the application and are not intended to be limiting of the application.

[0019] The mine composite disaster prevention method and system based on well-ground collaborative fracturing and extraction provided in the application, the method comprises: identifying high-position overburden key layers and low-position overburden key layers in overburden layers based on mine geological conditions; establishing an L-shaped double-bench horizontal well from the ground according to the high-position overburden key layers and the low-position overburden key layers, and performing segmented hydraulic fracturing on the well section of the L-shaped double-bench horizontal well located in the high-position overburden key layers and the low-position overburden key layers; extending the vertical well section of the L-shaped double-bench horizontal well downward to the underground operation roadway, and establishing a high-pressure fluid conveying channel from the ground fracturing equipment to the underground roadway; using the high-pressure fluid conveying channel to perform segmented hydraulic fracturing on the borehole arranged in the underground roadway by the ground fracturing equipment; and connecting the L-shaped double-bench horizontal well after fracturing and the borehole in the underground roadway after fracturing to a coal mine extraction system for networked collaborative extraction. The technical solution provided in the application realizes large-area pressure relief and permeability improvement of coal seams, improves extraction efficiency, and ensures safe and efficient production of mines.

[0020] The mine composite disaster prevention method and system based on well-ground collaborative fracturing and extraction of the embodiments of the application will be described below with reference to the accompanying drawings.

[0021] Embodiment one Figure 1 A flowchart of a mine composite disaster prevention method based on well-ground collaborative fracturing and extraction according to one embodiment of the application is shown in FIG. 1, which comprises the following steps. Figure 1 Step 1: identifying high-position overburden key layers and low-position overburden key layers in overburden layers based on mine geological conditions.

[0022] In the embodiments of the present disclosure, the step 1 specifically comprises: The lower part of the bending subsidence zone of the area where the mine is located is taken as the high-position overburden key layer, and the lower part of the water flowing fractured zone of the area where the mine is located is taken as the low-position overburden key layer.

[0023] It should be noted that the high-position overburden key layer and the low-position overburden key layer refer to rock layers that control the movement of all or part of the rock layers. The common characteristics of the two are large rock layer thickness, hard rock quality, high elastic modulus, and non-coordinated deformation with the upper rock layer after breaking and coordinated deformation with the lower rock layer. The high-position overburden key layer should be selected at the lower part of the bending subsidence zone, and the low-position overburden key layer should be selected at the lower part of the water flowing fractured zone.

[0024] Step 2: establishing an L-shaped double-bench horizontal well from the ground according to the high-position overburden key layers and the low-position overburden key layers, and performing segmented hydraulic fracturing on the well section of the L-shaped double-bench horizontal well located in the high-position overburden key layers and the low-position overburden key layers.

[0025] ​It should be noted that the L-shaped double-step horizontal well is an L-shaped double-step horizontal well that penetrates the key upper overburden layer and the key lower overburden layer.

[0026] In this embodiment of the disclosure, the segmented hydraulic fracturing of the L-shaped double-step horizontal well section located within the upper and lower critical overburden layers includes: The L-shaped double-step horizontal well was subjected to segmented hydraulic fracturing using a high-displacement, segmented sand fracturing process. The spacing between the fracturing segments is 60 to 100 meters.

[0027] It should be noted that a set of L-shaped double-step horizontal wells were constructed on the ground, and segmented fracturing was carried out in the key layers of high and low overburden to promote the early decompression of the hard top plate.

[0028] L-shaped double-step horizontal wells refer to horizontal wells dug during the construction of vertical wells on the surface, when passing through the key high and low overburden layers described in step one. The end of the horizontal well should cover the cut-in point of the working face. The preferred construction method for horizontal wells is high-volume segmented hydraulic fracturing with proppant, with segmented fracturing intervals of 60-100m.

[0029] Step 3: Extend the vertical section of the L-shaped double-step horizontal well downward to connect with the underground working roadway, and establish a high-pressure fluid transport channel from the surface fracturing equipment to the underground roadway.

[0030] It should be noted that the high-pressure fluid transport channel includes: a high-pressure outlet of the surface fracturing equipment, a fracturing wellhead, a well bottom extending to the underground roadway, and a high-pressure connection device connected in sequence, which is connected to the underground borehole through the high-pressure connection device.

[0031] Based on the existing vertical section of the L-shaped horizontal well, drilling continues until it connects with the underground working roadway. A high-pressure manifold is used to connect the surface fracturing equipment with the long borehole underground, forming a channel for transporting high-pressure fluid from the surface to the borehole underground.

[0032] Connecting surface fracturing equipment to underground long boreholes using high-pressure manifolds refers to connecting the high-pressure outlet and fracturing wellhead of the surface fracturing equipment, the bottom end of the surface well, and the underground long borehole through a high-pressure connection device. This forms a channel for transporting high-pressure fluid from the surface to the underground long borehole in the coal mine, ensuring the safe operation of segmented fracturing of the underground long borehole in the underground roadway.

[0033] Step 4: Using the high-pressure fluid delivery channel, the boreholes arranged in the underground roadway are subjected to segmented hydraulic fracturing through the surface fracturing equipment.

[0034] In this embodiment of the disclosure, the segmented hydraulic fracturing of the boreholes arranged in the underground roadway includes: The directional perforation staged fracturing process was used to perform staged hydraulic fracturing on the boreholes in the underground roadway. In the directional perforation segmented fracturing process, the fracturing fluid is clean water, and the spacing between the fracturing segments is 50-80 meters.

[0035] It should be noted that the boreholes in the underground roadway include: directional long boreholes and / or ordinary boreholes; Wherein, when the hardness of the coal seam is greater than or equal to a first threshold, the borehole is arranged in the coal seam; When the hardness of the coal seam is less than the first threshold, the borehole is arranged in the top or bottom plate of the coal seam, and the distance between the horizontal section trajectory of the borehole and the top or bottom plate of the coal seam is within the range of 2-5 meters.

[0036] In this embodiment of the disclosure, the method further includes: In-hole transient electromagnetic profiling technology was used to detect the borehole after fracturing and to assess the impact range and effect of hydraulic fracturing.

[0037] It should be noted that surface fracturing equipment is used to perform alternating fracturing operations on downhole directional long boreholes or conventional boreholes, achieving segmented fracturing of each borehole. In-hole transient electromagnetic profiling technology is employed to detect the influence range of hydraulic fracturing in the fracturing boreholes, further analyzing the effectiveness of the hydraulic fracturing operation.

[0038] For downhole directional long boreholes or ordinary boreholes, the preferred construction method is directional perforation segmented hydraulic fracturing. Clean water is used as the fracturing fluid, and the spacing between fracturing segments is 50-80m.

[0039] Specifically, for medium-hard and above coal seams, underground directional long boreholes and ordinary boreholes should be set in the coal seam to directly fracturing the coal seam, improve the permeability of the coal seam, and shorten the pre-drainage time; while for broken and soft coal seams, underground directional long boreholes and ordinary boreholes should be arranged in the top / bottom of the coal seam, and the trajectory of the horizontal section of the directional long borehole should be controlled within a range of 2-5m from the top / bottom of the coal seam.

[0040] Step 5: Connect the fractured L-shaped double-step horizontal well and the boreholes in the fractured underground roadway to the coal mine extraction system for grid-connected and coordinated extraction.

[0041] In this embodiment of the disclosure, connecting the fractured L-shaped double-step horizontal well and the borehole in the fractured underground roadway to the coal mine extraction system includes: The L-shaped double-step horizontal well is connected to a low negative pressure extraction pipeline laid in the roadway through an extraction pipeline to continuously extract gas from the goaf during and after the mining period. The boreholes in the underground roadway are connected to the high negative pressure extraction pipeline laid in the roadway through the extraction pipeline to extract regional coal seam gas.

[0042] It should be noted that a coal mine-specific extraction system is used to conduct grid-connected extraction of the L-shaped double-step horizontal well after fracturing and all underground boreholes.

[0043] The coal mine-specific extraction system refers to the high negative pressure extraction system in high-gas mines. It connects the L-shaped double-step horizontal well to the high negative pressure extraction pipeline laid in the roadway through the extraction pipeline, and also has the function of controlling gas in the goaf during mining. It connects each borehole underground to the high negative pressure extraction pipeline laid in the roadway to accurately control regional coal seam gas and shorten the extraction time to meet standards.

[0044] In particular, after the working face is finished, the goaf is fully enclosed for extraction. The L-shaped double-step horizontal well can still continuously extract gas from the goaf to achieve its long-term effective utilization.

[0045] It should be noted that, as Figure 2 The diagram shown is a schematic representation of the well-to-surface structure in the mine composite disaster prevention method of well-to-surface coordinated fracturing and extraction implemented in this embodiment. Figure 2 In the diagram, 1 represents the surface fracturing equipment, 2 represents the double-step horizontal well, 3 represents the key layer of high-level overburden, 4 represents the key layer of low-level overburden, 5 represents the high-pressure manifold, 6 represents the directional long borehole, 7 represents the coal seam, 8 represents the drilling rig, 9 represents the working roadway, and 10 represents the cross-layer borehole.

[0046] The mine composite disaster prevention and control method based on well-ground coordinated fracturing and extraction proposed in this embodiment has the following advantages: (1) By using L-shaped double-step horizontal wells to perform segmented fracturing in key overburden strata at high and low levels, it is possible to promote the early decompression of the hard roof, effectively reduce the pressure step distance, reduce support resistance, and reduce the deformation of the advance roadway during mining. At the same time, the fracturing of the overlying key strata generates new fractures, providing a good channel for the movement of coal seam decompression gas, which greatly alleviates the gas control burden in the goaf and upper corner during mining.

[0047] (2) Using ground fracturing equipment for construction solves the shortcomings of small displacement of underground fracturing equipment, difficulty in sand addition, difficulty in equipment transportation, and poor coal seam permeability enhancement. It can realize low-cost, high-displacement segmented fracturing transformation.

[0048] (3) Make full use of the good uniformity and flexibility of underground boreholes, and use high flow rate and high pressure ground equipment in conjunction with underground directional long boreholes and ordinary boreholes to control roof pre-fracture, gas in mining face and coal roadway strip gas during mining. This can effectively improve the effect of measures and shorten the gas pre-drainage time.

[0049] (4) The vertical shaft section not only serves as a channel for the surface fracturing equipment to deliver fracturing media to the horizontal shaft and downhole borehole, but also serves as the main channel for the double-step horizontal shaft to extract gas from the goaf throughout the entire mining cycle, truly achieving "one well for multiple uses". While improving the utilization rate of the vertical shaft, it reduces the amount of tunnel engineering and lowers the cost of mine disaster management.

[0050] (5) The double-step horizontal well proposed in this invention achieves large-area pressure relief and permeability enhancement of the coal seam through advanced fracturing of the overlying hard rock strata. It does not rely on the pressure drop funnel in traditional drainage and gas production, but utilizes the gas diffusion and buoyancy effect to produce gas, greatly extending the service life. Combined with the refined extraction of underground boreholes, it improves extraction efficiency while ensuring safe and efficient mine production.

[0051] In summary, the proposed method for preventing and controlling complex mine disasters based on well-ground coordinated fracturing and extraction integrates surface and underground measures to coordinate the management of multiple disasters such as coal mine rock bursts, gas outbursts, and water hazards. This effectively ensures the proactive, regional, sustainable, and efficient nature of mine disaster prevention and control, enables the multi-scenario utilization of drilling, and reduces the cost of mine disaster management.

[0052] Example 2 Figure 3 This is a structural diagram of a mine composite disaster prevention system based on well-to-surface coordinated fracturing and extraction, according to an embodiment of this application. Figure 3 As shown, the system includes: Identification module 100 is used to identify key upper and lower overlying strata in the overlying strata based on the geological conditions of the mine. Module 200 is used to establish an L-shaped double-step horizontal well from the ground based on the high-level overburden key layer and the low-level overburden key layer, and to perform segmented hydraulic fracturing on the well section of the L-shaped double-step horizontal well located in the high-level overburden key layer and the low-level overburden key layer. It should be noted that the L-shaped double-step horizontal well is an L-shaped double-step horizontal well that penetrates the key upper overburden layer and the key lower overburden layer.

[0053] The through module 300 is used to extend the vertical section of the L-shaped double-step horizontal well downward to connect with the underground working roadway, and to establish a high-pressure fluid transport channel from the surface fracturing equipment to the underground roadway. It should be noted that the high-pressure fluid transport channel includes: a high-pressure outlet of the surface fracturing equipment, a fracturing wellhead, a well bottom extending to the underground roadway, and a high-pressure connection device connected in sequence, which is connected to the underground borehole through the high-pressure connection device.

[0054] The fracturing module 400 is used to perform segmented hydraulic fracturing of boreholes arranged in the underground roadway by means of the high-pressure fluid delivery channel and the surface fracturing equipment. It should be noted that the boreholes in the underground roadway include: directional long boreholes and / or ordinary boreholes; Wherein, when the hardness of the coal seam is greater than or equal to a first threshold, the borehole is arranged in the coal seam; When the hardness of the coal seam is less than the first threshold, the borehole is arranged in the top or bottom plate of the coal seam, and the distance between the horizontal section trajectory of the borehole and the top or bottom plate of the coal seam is within the range of 2-5 meters.

[0055] The extraction module 500 is used to connect the L-shaped double-step horizontal well after fracturing and the boreholes in the underground roadway after fracturing to the coal mine extraction system for grid-connected and coordinated extraction.

[0056] In this embodiment of the disclosure, the identification module 100 is further configured to: The lower part of the curved subsidence zone in the area where the mine is located is designated as the key stratum of the high-level overburden, and the lower part of the water-conducting fracture zone in the area where the mine is located is designated as the key stratum of the low-level overburden.

[0057] In this embodiment of the disclosure, the establishment module 200 is further configured to: The L-shaped double-step horizontal well was subjected to segmented hydraulic fracturing using a high-displacement, segmented sand fracturing process. The spacing between the fracturing segments is 60 to 100 meters.

[0058] In this embodiment of the disclosure, the fracturing module 400 is further configured to: The directional perforation staged fracturing process was used to perform staged hydraulic fracturing on the boreholes in the underground roadway. In the directional perforation segmented fracturing process, the fracturing fluid is clean water, and the spacing between the fracturing segments is 50-80 meters.

[0059] In this embodiment of the disclosure, the sampling module 500 is further configured to: In-hole transient electromagnetic profiling technology was used to detect the borehole after fracturing and to assess the impact range and effect of hydraulic fracturing.

[0060] In this embodiment of the disclosure, the sampling module 500 is further configured to: The L-shaped double-step horizontal well is connected to a low negative pressure extraction pipeline laid in the roadway through an extraction pipeline to continuously extract gas from the goaf during and after the mining period. The boreholes in the underground roadway are connected to the high negative pressure extraction pipeline laid in the roadway through the extraction pipeline to extract regional coal seam gas.

[0061] In summary, the mine composite disaster prevention and control system based on well-ground coordinated fracturing and extraction proposed in this embodiment realizes large-area pressure relief and permeability enhancement of coal seams, improves extraction efficiency, and ensures safe and efficient mine production.

[0062] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0063] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0064] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preventing and controlling complex mine disasters based on well-ground coordinated fracturing and extraction, characterized in that, The method includes: Identify key upper and lower overlying strata in the overlying strata based on the geological conditions of the mine. Based on the key overburden layers of the high and low levels, an L-shaped double-step horizontal well is constructed from the ground, and the well section of the L-shaped double-step horizontal well located within the key overburden layers of the high and low levels is subjected to segmented hydraulic fracturing. The vertical section of the L-shaped double-step horizontal well is extended downward to connect with the underground working roadway, and a high-pressure fluid transport channel is established from the surface fracturing equipment to the underground roadway. Using the high-pressure fluid delivery channel, the surface fracturing equipment is used to perform segmented hydraulic fracturing on the boreholes arranged in the underground roadway. The L-shaped double-step horizontal well after fracturing and the boreholes in the underground roadway after fracturing are connected to the coal mine extraction system for grid-connected and coordinated extraction.

2. The method as described in claim 1, characterized in that, The identification of key upper and lower overlying strata based on mine geological conditions includes: The lower part of the curved subsidence zone in the area where the mine is located is designated as the key stratum of the high-level overburden, and the lower part of the water-conducting fracture zone in the area where the mine is located is designated as the key stratum of the low-level overburden.

3. The method as described in claim 2, characterized in that, The L-shaped double-step horizontal well is an L-shaped double-step horizontal well that penetrates the key upper overburden layer and the key lower overburden layer.

4. The method as described in claim 3, characterized in that, The segmented hydraulic fracturing of the L-shaped double-step horizontal well section located within the upper and lower critical overburden layers includes: The L-shaped double-step horizontal well was subjected to segmented hydraulic fracturing using a high-displacement, segmented sand fracturing process. The spacing between the fracturing segments is 60 to 100 meters.

5. The method as described in claim 4, characterized in that, The high-pressure fluid transport channel includes: a high-pressure outlet of the surface fracturing equipment, a fracturing wellhead, a well bottom extending to the underground roadway, and a high-pressure connection device connected in sequence, which is connected to the underground borehole through the high-pressure connection device.

6. The method as described in claim 5, characterized in that, The staged hydraulic fracturing of boreholes arranged in the underground roadway includes: The directional perforation staged fracturing process was used to perform staged hydraulic fracturing on the boreholes in the underground roadway. In the directional perforation segmented fracturing process, the fracturing fluid is clean water, and the spacing between the fracturing segments is 50-80 meters.

7. The method as described in claim 6, characterized in that, The boreholes in the underground roadway include: directional long boreholes and / or ordinary boreholes; Wherein, when the hardness of the coal seam is greater than or equal to a first threshold, the borehole is arranged in the coal seam; When the hardness of the coal seam is less than the first threshold, the borehole is arranged in the top or bottom plate of the coal seam, and the distance between the horizontal section trajectory of the borehole and the top or bottom plate of the coal seam is within the range of 2-5 meters.

8. The method as described in claim 1, characterized in that, The method further includes: In-hole transient electromagnetic profiling technology was used to detect the borehole after fracturing and to assess the impact range and effect of hydraulic fracturing.

9. The method as described in claim 1, characterized in that, The process of connecting the fractured L-shaped double-step horizontal well and the boreholes in the fractured underground roadway to the coal mine extraction system includes: The L-shaped double-step horizontal well is connected to a low negative pressure extraction pipeline laid in the roadway through an extraction pipeline to continuously extract gas from the goaf during and after the mining period. The boreholes in the underground roadway are connected to the high negative pressure extraction pipeline laid in the roadway through the extraction pipeline to extract regional coal seam gas.

10. A mine composite disaster prevention system based on well-ground coordinated fracturing and extraction, according to any one of claims 1-9, characterized in that, The system includes: The identification module is used to identify key upper and lower overlying strata in the overlying strata based on the geological conditions of the mine. A module is established to build an L-shaped double-step horizontal well from the ground based on the key upper and lower overburden layers, and to perform segmented hydraulic fracturing on the well section of the L-shaped double-step horizontal well located in the key upper and lower overburden layers. The connecting module is used to extend the vertical section of the L-shaped double-step horizontal well downward to connect with the underground working roadway, and to establish a high-pressure fluid transport channel from the surface fracturing equipment to the underground roadway. The fracturing module is used to perform segmented hydraulic fracturing of boreholes arranged in the underground roadway by means of the high-pressure fluid delivery channel and the surface fracturing equipment. The extraction module is used to connect the fractured L-shaped double-step horizontal well and the boreholes in the fractured underground roadway to the coal mine extraction system for grid-connected and coordinated extraction.

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